Phẫu Thuật Tạo Hình (Tập 6): Bàn Tay Và Chi Trên – Neligan (Ấn bản 4)

523
Surgical treatment of pain
The key to operating on neuropathic pain is to proactively
employ all the treatment options discussed earlier. These
patients should have the perioperative, intraoperative and
postoperative treatments planned before surgery is consid­
ered. Psychological support should be in place for those with
concomitant anxiety or depression. Therapy must be available
to help the patient through the post surgical rehabilitation. If
a thoughtful multimodal strategy is used, the risks of worsen­
ing the pain can be significantly decreased, making the sur­
gery’s risk–benefit ratio in the patient’s favor.71–73
Neuromas
Painful neuromas can potentially be improved with surgical
correction. If possible, the best treatment for neuromas is
neuroma excision followed by reconstruction with nerve
grafts.74 Another technique for a painful neuroma is end-to-
side coaptation of the injured nerve to a healthy nerve, which
is particularly useful for digital neuromas. Both these tech­
niques restore a path for injured axons to reconnect with their
end organs.
However, pure sensory neuromas are often distal and recon­
structing the nerve is not an option. For these cases, surgical
correction of a neuroma is more about recreating the injury and
then attempting to alter the post-injury course to result in a
non-painful neuroma. The goal is to place the new injured
nerve stump in a new low-stimulation environment. The
microenvironment impacts the development of the neuroma
and the surgeon can optimize the neuroma placement.75
The literature on neuroma resection is limited and het­
erogeneous. A prospective study of 34 patients found that
surgically treated neuromas in the upper limb resulted in a
decrease of the mean visual analog scale score from 6.8 to 4.9
(p < 0.01).72
Nerve compression
Nerve release is a common technique for the surgeon who
cares for the upper limb. Carpal tunnel and cubital tunnel
syndromes are known pain generators and easily recognized
by providers. Other sites of nerve compression should be
considered and treated when working with neuropathic
pain of the upper limb. Radial tunnel, pronator syndrome,
quadrangular space entrapment, and thoracic outlet all
can be addressed surgically if conservative treatment
fails.76
Neuro-stimulation
For the patient who has failed other treatments, neuro-
stimulation can give pain relief. Neuro-stimulation is thought
to work by blocking pain signals via the “gate theory”. The
gate theory posits that stimulation of the nerve with non-
painful signals can close the “gate” preventing other painful
signals from being processed.77 Most of the information in this
field is related to spinal cord stimulators, which can reduce
pain by 50%.78 Neuro-stimulation is an exciting area that is
being transformed by emerging technology. The current avail­
able devices are limited by lead failure, lead migration, and
limited locations to place the bulky power sources. As tech­
nology miniaturizes the power sources and eliminates the
leads, there will be an increase of uses for nerve stimulators
in the patient with neuropathic pain.
intolerable side effects (sedation, dizziness), but slow titration
allows these side effects to be significantly minimized. This
need for patience must be explained at the outset or the patient
will discard a medication that may provide pain relief.
The gabapentinoids (gabapentin and pregabalin) are very
useful in the treatment of neuropathic pain. These medica­
tions appear to modulate voltage-gated calcium channels
existing on presynaptic pain-carrying neurons in the dorsal
horn of the spinal cord.65 In studies of other neuropathic pain
conditions, such as diabetic neuropathy and post-herpetic
neuralgia, the number needed to treat for gabapentin ranged
from 4 to 6 12.66 The primary issue with these medications are
the cognitive side effects; however, these can be ameliorated
by slow titration.
Tricyclic antidepressants (nortriptyline, desipramine) have
been found in many trials to be effective in the treatment of
neuropathic pain.67 They are thought to work by central
mechanisms of inhibition of noradrenaline and serotonin
uptake, as well as NMDA receptor antagonism and sodium
channel inhibition. They also have a lower number needed to
treat than the gabapentinoids. However, these medications
need to be carefully monitored due to their potential severe
adverse effects including cardiac issues, especially at higher
doses. The surgeon, may not be comfortable monitoring the
titration of these medications and could consider starting at a
low dose and initiating a referral to a pain physician for titra­
tion. In addition, if the patient has comorbid depression, the
hand provider could discuss the patient with their mental
health provider to see if switching to tricyclic antidepressants
might be feasible.
Serotonin–norepinephrine reuptake inhibitors such as
duloxetine (trade name: Cymbalta) have been found to be
effective against neuropathic pain and these medications do
not have the anti-cholinergic or cardiac side effects.67
Physical modalities
These treatments have long been a central pillar to the treat­
ment of neuropathic pain. Standard hand therapy is useful in
the patient with neuropathic pain, especially in the acute
injury time period. These treatments focus on decreasing
edema, promoting nerve gliding, and improving range of
motion. There are also additional interventions uniquely tar­
geting the pathologic pathways that promote neuropathic
pain. Neuropathic pain causes changes at every level of the
somatosensory system. Neuropathic pain-specific physical
modalities attempt to modulate not only the peripheral pain
generators but also the central components of the brain and
spinal cord. The therapists will focus on left/right identifica­
tion, graded motor imagery exercises, and mirror therapy.68–70
Neuropathic physical treatments require a distinct approach
with care to not overstimulate, using short duration and
repetitive interventions.
Surgical treatment of pain
Surgeons are often hesitant to operate on pain with historic
recommendations to avoid surgery as it risks “flaring” the
pain. However, as time has progressed, it has become clear
that if an injured or compressed nerve is contributing to pain,
surgical intervention may be a critical part of the rehabilita­
tion plan.

524
SECTION III
CHAPTER 23 • Neuropathic pain in the upper extremity
Future directions
Given the enormous costs to the patient, society, and the
healthcare system, there is a large amount of interest in
improving neuropathic pain. Interesting new avenues of
research include the role of the immune system in neuropathic
pain. Emerging evidence suggests that some pain may be
mediated through autoimmune mechanisms.79–80 This link
may open up new avenues of treatment through immune
modulators.
On a healthcare system level, pain has taken on increased
importance. The Institute of Medicine recently released a
report, Relieving Pain in America: A Blueprint for Transforming
Prevention, Care, Education, and Research.81 This report high­
lighted the impact of pain and presented specific timelines
and goals. This focused effort will continue to push us towards
improved pain care.
3. IASP website.
?ItemNumber=1698#Centralneropathicpain.
9. Harden RN, Oaklander AL, Burton AW, et al. Complex regional
pain syndrome: practical diagnostic and treatment guidelines. Pain
Med. 2013;14:180–229. This is a systematic review by experts in the field.
It provides information on the diagnosis of CRPS. The article then reviews
the evidence for potential treatment modalities including physical,
pharmacological, and psychological interventions.
26. Mehta SP, MacDermid JC, Richardson J, et al. Baseline pain
intensity is a predictor of chronic pain in individuals with distal
radius fracture. J Orthop Sports Phys Ther. 2015;45:119–127.
36. Terkelsen AJ, Bach FW, Jensen TS. Experimental forearm
immobilization in humans induces cold and mechanical
hyperalgesia. Anesthesiology. 2008;109:297–307. This study took 27
healthy controls and placed them in a forearm cast for 4 weeks. After cast
removal the subjects had transient symptoms similar to CRPS including
changes in skin temperature, mechanosensitivity, and thermosensitivity.
40. Mackey S, Carroll I, Emir B, et al. Sensory pain qualities in
neuropathic pain. J Pain. 2012;13:58–63.
41. Hagert CG, Hagert E, Slutsky DJ. Manual muscle testing: a clinical
examination technique for diagnosing focal neuropathies in the
upper extremity. In: Upper Extremity Nerve Repair: Tips and
Techniques. A Master Skills Publication. Rosemont, IL: American
Society for Surgery of the Hand; 2008:451–466. This text provides a
detailed description of the manual muscle testing to assess for nerve
injury. There is detailed information on the physical exam and anatomy. It
reviews the diagnosis of less common nerve entrapments such as pronator
and radial tunnel syndrome.
53. Dauri M, Faria S, Gatti A, et al. Gabapentin and pregabalin for the
acute post-operative pain management. A systematic-narrative
review of the recent clinical evidences. Curr Drug Targets.
2009;10:716–733.
54. Tiippana EM, Hamunen K, Kontinen VK, et al. Do surgical patients
benefit from perioperative gabapentin/pregabalin? A systematic
review of efficacy and safety. Anesth Analg. 2007;104:1545–1556. This
systematic review of 22 studies found that perioperative gabapentin
provided postoperative pain relief, reduced opioid use, and limited opioid
side effects. They also found that the most common adverse effects of
gabapentin were dizziness and sedation.
57. Carroll I, Hah J, Mackey S, et al. Perioperative interventions to
reduce chronic postsurgical pain. J Reconstr Microsurg. 2013;29:213–
222. This manuscript reviews in detail pre-surgical interventions to
reduce pain. It provides a clear algorithm with drug dosages for the
patient at risk for chronic pain.
73. Dellon AL, Mackinnon SE. Treatment of the painful neuroma by
neuroma resection and muscle implantation. Plast Reconstr Surg.
1986;77:427–438.
76. Hagert E, Hagert CG. Upper extremity nerve entrapments: the
axillary and radial nerves – clinical diagnosis and surgical
treatment. Plast Reconstr Surg. 2014;134:71–78.
81. Institute of Medicine (US) Committee on Advancing Pain Research,
Care, and Education. Relieving Pain in America: A Blueprint for
Transforming Prevention, Care, Education, and Research. Washington,
DC: National Academies Press (US); 2011.
Access the complete reference list online at

524.e1
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37. Pepper A, Li W, Kingery WS, et al. Changes resembling complex
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examination technique for diagnosing focal neuropathies in the
upper extremity. In: Upper Extremity Nerve Repair: Tips and
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Society for Surgery of the Hand; 2008:451–466. This text provides a
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reviews the diagnosis of less common nerve entrapments such as pronator
and radial tunnel syndrome.
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CHAPTER 23 • Neuropathic pain in the upper extremity
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54. Tiippana EM, Hamunen K, Kontinen VK, et al. Do surgical patients
benefit from perioperative gabapentin/pregabalin? A systematic
review of efficacy and safety. Anesth Analg. 2007;104:1545–1556. This
systematic review of 22 studies found that perioperative gabapentin
provided postoperative pain relief, reduced opioid use, and limited opioid
side effects. They also found that the most common adverse effects of
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DC: National Academies Press (US); 2011.

SECTION III • Acquired Non-traumatic Disorders
24 
Nerve entrapment syndromes
Elisabet Hagert and Donald Lalonde
SYNOPSIS
■ Chronic nerve entrapment syndromes in the upper extremity are
common and their occurrence is only likely to increase as risk factors
such as diabetes, obesity, and advanced age become more prevalent
in the general population.
■ In most cases, the diagnosis is based on a good history and a proper
physical examination.
■ For more atypical presentations, a detailed clinical examination using a
clinical triad of muscle testing, scratch collapse test, and specific pain
points must be performed to rule out proximal nerve entrapments in
the upper extremity.
■ In the event of advanced muscle atrophy, muscle fibrillations, and
severe sensory disturbances, consideration should be given to other
neurologic conditions that mimic nerve entrapment syndromes such as
mononeuritis, Parsonage–Turner syndrome, and motor neuropathies;
not only will these conditions not respond to surgical decompression,
they may in fact be exacerbated by operative management.
■ When the diagnosis is unclear, electrodiagnostic tests and magnetic
resonance or ultrasound imaging may be of benefit.
■ The purpose of this chapter is to provide the reader with a
comprehensive review of the pathophysiology, clinical diagnosis, and
surgical treatment of nerve entrapment syndromes of the upper
extremity.
Pathophysiology of chronic nerve
compression
In carpal tunnel syndrome (CTS), the initial pathophysiology
in chronic nerve compression (CNC) is seen clinically as
paresthesias and an elevation in the static cutaneous sensory
threshold as measured by Semmes–Weinstein monofilament
testing. With increased compression, localized demyelination
occurs followed by more diffuse demyelination.1 At this stage,
patients will experience muscle weakness and will demon­
strate increased pressure thresholds for quickly adapting
fibers on vibrometry; two-point discrimination, measured in
millimeters, remains unchanged. Superficial fascicles tend to
undergo demyelination earlier and may explain varying
patient symptoms within a single nerve distribution. In early
CTS, for example, patients are more likely first to experience
paresthesias in the long and ring fingers as the fascicles to
these digits are most superficial within the median nerve.
Wallerian degeneration and axonal damage is not seen until
the final stages of CNC,2,3 at which point the patient presents
with chronic numbness and thenar atrophy.
More proximal median nerve entrapments, such as the
lacertus syndrome,4 will differ in clinical presentation as the
most superficial fascicles in the nerve at the level of the lacer­
tus fibrosus are motor fibers to the flexor carpi radialis, flexor
pollicis longus, and the deep flexor of the index finger.5
Patients with early lacertus syndrome thus complain of diffuse
weakness of pinch and grip, but the sensory symptoms are
not evident until later stages, when deeper sensory fibers are
affected. This is why lacertus syndrome is predominantly
diagnosed by demonstrating weakness of the affected muscles
on proper physical examination.
Double-crush syndrome
The double-crush syndrome (DCS) is an important concept
in CNC. First proposed by Upton and McComas, the double-
crush concept holds that compression of a peripheral nerve at
one site increases susceptibility to compression at another site
along the same nerve.6 This phenomenon appears to be the
result of the disruption of anterograde or, in the case of “reverse
DCS”, retrograde axoplasmic flow of neurotrophic factors.7
DCS has been demonstrated experimentally in animal models
of chronic compression.8–11 Clinically, numerous examples of
multiple sites of compression along the same nerve have been
described and include reports of cervical radiculopathy and
median nerve compression, CTS and pronator syndrome,
and cubital tunnel syndrome and ulnar nerve compression in
Guyon’s canal.12–15 The DCS concept suggests that two or more
simultaneous points of compression, each of which might be
  Access video and video lecture content for this chapter online at expertconsult.com

526
SECTION III
CHAPTER 24 • Nerve entrapment syndromes
insufficient to cause symptoms on its own, could together
produce symptoms of clinical severity. The underlying causes
of DCS may include impaired axonal transport, changes in
ion channel regulation, neuro-inflammatory processes and
instances of neuroma-in-continuity.16
The presence of DCS places a great responsibility on the
surgeon or therapist to perform a thorough physical examina­
tion to delineate the levels of nerve compression, using a
combination of manual muscle testing algorithms and the
scratch collapse test.17,18 In the surgical treatment of DCS,
decompression of one of the two sites might be sufficient
to address a patient’s symptoms. The most distal nerve
compression is typically decompressed first as it is usually
the site of the more severe compression and lower surgical
risk. If decompression in the distal extremity fails to relieve
symptoms, decompression of the more proximal site, such
as the intervertebral space or brachial plexus, should be
considered.
Clinical examination of upper extremity
nerve entrapments
The difficulty in diagnosis of upper extremity nerve entrap­
ments lies in the variable spectrum of a patient’s symptoms.
Even in instances of apparent carpal tunnel syndrome, symp­
toms outside of the median innervated region in the hand are
present in two-thirds of patients.19 In some cases, bilateral
pain is present despite only unilateral nerve involvement.20
Another aspect that influences a clinical presentation is the
origin of the CNC, where disturbances in neural blood flow
and axonal transport commonly occurs without axonal injury.
This results in an inability to reliably use electrodiagnostic
tools for a definitive diagnosis. Electrodiagnostics should
rather be seen as a complimentary modality to a thorough
clinical examination.18 The degree of nerve injury in CNC is
most commonly associated to a Sunderland degree I, or a
Seddon’s neuropraxia.21 Possible loss of motor function will
not be evident as muscle atrophy. However, muscle weakness
can be shown through a clinical triad including: (1) manual
muscle testing to delineate the level of nerve entrapment(s);
(2) scratch collapse test to confirm and order the importance
of nerve entrapment(s); and (3) pain and tenderness over the
nerve at the level of entrapment(s).17
Manual muscle testing algorithm (Video 24.1 )
Here is why proper physical examination with muscle testing
is so important. The principle of grading of muscle strength
was established by Seddon in the 1950s into six grades: M0 to
M5.22 M0 to M3 represent weaknesses that are clinically appar­
ent and found in instances of axonotmesis or complete nerve
transections. M5 represents normal power with no loss of
strength. The difficulty is diagnosing the M4 grade of muscle
strength, which is defined as “contraction against gravity and
resistance”. If we look for it, we will commonly find M4 weak­
ness in CNC, where changes in the nerve are not dependent
on axonal injury. Since this type of muscle weakness can only
be found using “resistance”, it is only found through clinical
examination of muscle strength. Based on this, the clinical
entity of M4 may be referred to as the “hidden paresis”, and
one we must actively look for.23
Out of the 60 muscles in the upper limb, about 45 are
accessible to manual testing of individual strength. A simpli­
fied manageable, manual muscle testing protocol involving
four positions and 12 muscles has been advocated.17,23 The
efficacy (sensitivity and specificity) of manual muscle testing
of antagonist muscles to determine levels of focal neuropa­
thies in the upper extremities have been established in
randomized and blinded level II studies to 88 and 93%,
respectively.24,25 The principle is straightforward: distal to the
level of nerve entrapment, distinct patterns of muscle weak­
nesses will be clinically present.
The four positions of muscle testing are as follows:
(1) shoulder – testing of pectoralis and posterior deltoid;
(2) elbow – testing of biceps, triceps and infraspina­
tus; (3) wrist – testing of extensor carpi ulnaris (ECU),
extensor carpi radialis brevis (ECRB) and flexor carpi
radialis (FCR); and (4) hand – testing of extrinsics (flexor
pollicis longus, FPL; flexor digitorum profundus V, FDP V)
and intrinsics (abductor pollicis brevis, APB; abductor digiti
minimi, ADM) (Video 24.1
).
The interpretation of each test is, of course, of outmost
importance and will be delineated in each nerve entrapment
section described in this chapter. Each muscle is also described
in Table 24.1 related to possible level of involvement as well
as in relation to position within the upper extremity (Fig.
24.1). The principle of the muscle testing algorithm is to
investigate the upper extremity consistently from a proximal
to a distal level of involvement, starting with the pectoralis
and ending with the hand intrinsics.
Scratch collapse test (Video 24.2 )
The scratch collapse test (SCT) was first described by Cheng,
Beck, and Mackinnon in 2008,26 and has since been used in
several publications to clinically verify levels of nerve entrap­
ment in the upper and lower extremities.4,17,27–29 In carpal
tunnel and cubital tunnel syndromes, the SCT has a diagnostic
accuracy of 82 and 89%, respectively, rendering this test more
sensitive than the commonly used Tinel’s and flexion nerve
compression tests.26
The concept of SCT is that a patient with a focal nerve
entrapment has an area of skin allodynia located at the level
of nerve entrapment. When scratching this area of skin, a brief
spinal reflex causes a momentary loss of voluntary muscle
contraction. Clinically, the patient is seated with elbows flexed
to 90°, shoulders adducted and slightly externally rotated.
The patient is asked to resist bilateral internal pressure applied
by the examiner onto the forearms. The area of suspected
nerve entrapment is then gently scratched and pressure again
applied onto the forearms. In the event of a focal nerve com­
pression, the patient will feel a distinct loss of muscle strength
in the affected arm (Video 24.2
).26,27
In instances of suspected multiple points of nerve compres­
sion, topical ethyl chloride may additionally be used to grade
the hierarchy of nerve compressions. By applying ethyl chlo­
ride over the primary level of nerve entrapment, underlying
and subclinical levels of entrapment may be revealed to
further aid the examiner in understanding a patient’s symp­
toms.18 The use of SCT can thus aid the clinical diagnosis of
nerve entrapment, where manual muscle testing is used to
delineate the level of nerve entrapment and SCT is used to
verify this level of entrapment.

527
Median nerve entrapments
Table 24.1  Interpretation of muscle exam: patterns of muscle weakness, nerve involvement, and level of entrapment
Weakness
Nerve
Level of entrapment
Pectoral
Cervical roots C6–T1
C6–T1 radiculopathy; possibly non-participating patient
Posterior deltoid
Axillary N.
Quadrilateral space
Biceps
Musculocutaneous N.
Proximal upper arm
Deltoid + biceps
Cervical roots C5–C6
C5–C6 radiculopathy
Pect + deltoid + biceps (+ triceps)
Infraclavicular brachial plexus
Subclavicular
Triceps
Radial N.
Triangular interval
Deltoid + triceps
Axillary + Radial N
Quadrilateral space + radial triangular interval
Triceps + FCR
Cervical root C7
C7 radiculopathy
Infra + supraspinatus
Suprascapular N.
Suprascapular notch
Infraspin + rhomboid
Cervical root C5
C5 radiculopathy
Rhomboid
Dorsal scapular N.
Middle scalene or proximal rhomboid edge
ECRB + EIP + EPL
Radial N.
Lateral intermuscular septum, distal upper arm
ECU
Radial N.
Radial tunnel syndrome – arcade of Frohse
EDC
Radial N.
Distal edge of supinator
FCR + FPL + FDP II
Median N.
Lacertus fibrosus
FDS III–IV
Median N.
Superficialis arcade
FPL + FDP II
Median N.
Anterior interosseous syndrome
APB
Median N.
Carpal tunnel
FDP V + ADM
Ulnar N.
Cubital tunnel
ADM
Ulnar N.
Guyon’s canal zone 1
1-DIO
Ulnar N.
Guyon’s canal zone 3
1-DIO, First dorsal interosseous; ADM, abductor digiti minimi; APB, abductor pollicis brevis; ECRB, extensor carpi radialis brevis; ECU, extensor carpi ulnaris; EIP,
extensor indicis proprius; EPL, extensor pollicis longus; FCR, flexor carpi radialis; FDP, flexor digitorum profundus; FDS, flexor digitorum superficialis; FPL, flexor pollicis
longus.
The last part in the clinical triad is the presence of pain
upon compression and/or a positive Tinel’s test at the level
of nerve compression to further confirm the correct level of
diagnosis.
Electrodiagnostic studies (EDS)
Although EDS are widely used in the evaluation of patients
with suspected upper extremity nerve entrapments, the sen­
sitivity and specificity of nerve entrapments aside from the
carpal tunnel and cubital tunnel syndromes, is only between
30–65%.30,31 The pitfalls of EDS include technical- and operator-
dependent errors, inability to distinguish mixed pattern type
of nerve injuries, limitation in electromyographic studies
where only a portion of muscle function is evaluated, and an
inability to detect early nerve compression syndromes.32
These shortcomings have even lead some authors to advise
against EDS,33 and rather advocate the use of clinical examina­
tion techniques.18
When an atypical presentation or comorbidities cloud the
clinical picture, symptom criteria and provocative tests can be
combined with EDS to make the diagnosis. Electrodiagnostics
are of particular use in grading nerve injuries in patients with
suspected diabetic or alcohol-induced polyneuropathy, in
patients with advance muscle atrophies and/or in patients
with peripheral muscle fibrillations where peripheral neuro­
pathic disease may be suspected. Two aspects of electrodiag­
nostic tests are most often used to diagnose nerve entrapment
syndromes: nerve conduction studies (NCS) and electromy­
ography (EMG). Of the two studies, the former are especially
helpful. An NCS is performed by placing two electrodes on
the skin, along the course of the nerve (Fig. 24.2). The first
electrode is used to stimulate a peripheral nerve to fire, and
the second electrode is used to record the characteristics of the
generated action potential at some distance away from the
stimulation point. The electrodes typically detect only larger,
faster-conducting fibers.
EMG studies assess the integrity of muscle function.
Because muscle integrity is dependent on innervation, these
studies help determine whether axonal damage has occurred.
Median nerve entrapments
Carpal tunnel syndrome
CTS is the most common nerve entrapment syndrome in the
upper extremity, with an estimated incidence in the US of 1–3
cases per 1000 subjects per year and a prevalence of 50 cases
per 1000 subjects per year.34 The surgical release of carpal
tunnel syndromes has the highest utilization rate of upper

528
SECTION III
CHAPTER 24 • Nerve entrapment syndromes
Fig. 24.1  The patient chart routinely used for nerve
entrapments. The patterns of muscle weakness found in
clinical testing is mapped according to dermatome, as
well as position in the arm. It allows for easier
visualization as to level of nerve entrapment. 1-DIO, first
dorsal interosseous; ADM, abductor digiti minimi;
AP, adductor pollicis; APB, abductor pollicis brevis;
ECRB, extensor carpi radialis brevis; ECRL, extensor carpi
radialis longus; ECU, extensor carpi ulnaris; EDC, extensor
digitorum communis; EIP, extensor indicis proprius;
EPL, extensor pollicis longus; FCR, flexor carpi radialis;
FDP, flexor digitorum profundus; FDS, flexor digitorum
superficialis; FPB, flexor pollicis brevis; FPL, flexor
pollicis longus; M, median nerve; R, radial nerve; U, ulnar
nerve. (Reprinted with kind permission from Prof.
Carl-Göran Hagert, MD, PhD.)
Rhomboid
ECRL-ECRB
FCR
EDC
ECU
EPL - EIP
FDP II-V
P
FPL
FDS
APB
ADM - 1-DIO
Triceps
Pronator
Serratus Ant
Infraspin
Supraspin
Deltoid
Biceps
Pectoralis
Latissimus
C5
C6
C7
C8
T1
Rhomb.
FDP II
FPL
ABP
Med.
Uln.
Name
Date of birth
Date of exam
Right / left arm
Right / left dominance
Pronator
FCR
FCU
FDS
FPB
AP
FDP V
FDP IV
ADM
FDP Ill
1-DIO
C5
C6
C7
C8
Th1
Rad.
Triceps
Brach.Rad.
ECRL
ECRB
EDC EPL
ECU
Supinator
EIP
Lumbr. I
I.Spin
Delt.
Biceps
Serratus
Pectoralis
Latissimus
R
M U
Fig. 24.2  Method for determining the median nerve
conduction velocity (CV) in the forearm, recording at the
thenar eminence.
Proximal latency (ms)
Distal latency (ms)
Distance
Distance (cm)
= CV (m/s)
+
+
S1
R
S2
Prox. lat. – Dist. lat. (ms)

529
Median nerve entrapments
beneath the TCL (subligamentous, 31%) or perforates the TCL
(transligamentous, 23%).37 The palmar cutaneous branch typi­
cally arises off the radial aspect of the median nerve 5–6 cm
proximal to the distal wrist crease. Additional branching
pattern variations of the recurrent motor branch and palmar
cutaneous branch have been described.38
Etiology
In the vast majority of CTS cases, an underlying etiology
cannot be identified. Women are more often affected than
men.39 Compression tends to be greatest at a point 1 cm distal
to the distal wrist crease where the TCL is thickest.40 In rare
instances, structural causes such as a persistent median artery,
ganglion cyst, hemangioma, or proximal lumbrical origin can
increase pressure within the carpal tunnel.
Systemic conditions, such as renal failure, thyroid
disease, rheumatoid arthritis, and diabetes mellitus, may also
predispose patients to CTS. CTS can occur in up to 45%
of pregnant women during the third trimester but usually
extremity disorders in the US, with an average of about 40
surgical releases per 10 000 subjects per year.35 The economic
burden from lost wages and productivity and treatment costs
is considerable.36 Despite the prevalence of CTS, debate
remains over the accurate diagnosis and optimal treatment of
the condition.
Anatomy
The anatomic boundaries of the carpal tunnel are defined
dorsally by the carpus, and volarly by the transverse carpal
ligament (TCL), which spans from the hamate and triquetrum
on the ulnar side to the scaphoid and trapezium on the radial
side. The median nerve is the most superficial structure within
the canal. The median nerve may divide in the forearm or split
within the carpal tunnel. Both presentations are associated
with a persistent median artery. The recurrent motor branch
to the thenar muscles usually arises off the median nerve in
an extraligamentous position distal to the TCL (46–90%) (Fig.
24.3). Less frequently, the motor branch originates from
Fig. 24.3  Variations in median nerve anatomy in the carpal tunnel. (A) The most common branching pattern of the motor branch is extraligamentous. (B) Subligamentous
branching pattern of the motor branch. (C) Transligamentous course of the recurrent motor branch. (D) The motor branch can rarely arise from the ulnar border of the
median nerve. (E) The motor branch can also lie superficial to the transverse carpal ligament.
A
B
D
E
C

530
SECTION III
CHAPTER 24 • Nerve entrapment syndromes
Given the utility of patient symptoms and physical find­
ings, attempts have been made to develop formal clinical
criteria for the diagnosis of CTS. Graham et al. generated a list
of six clinical criteria (CTS-6) for the diagnosis of CTS, based
on a validated statistical analysis of recommendations by an
expert panel. The six criteria included: (1) nocturnal numb­
ness; (2) numbness and tingling in the median nerve distribu­
tion; (3) weakness and/or atrophy of the thenar muscles; (4)
Tinel sign; (5) Phalen’s test; and (6) loss of two-point discrimi­
nation.54 Similarly, an American Academy of Orthopaedic
Surgeons (AAOS) panel reviewed the available literature and
developed recommendations for diagnosing CTS; high-level
evidence was lacking to support the majority of recommenda­
tions.55 The CTS-6 lacks a recommendation regarding muscle
exam, which should always be considered an important part
of the clinical diagnosis of CTS to rule out possible proximal
median nerve involvement.
Other diagnostic tools
CTS remains a clinical diagnosis, and the role of electrodiag­
nostic and imaging studies remains complementary. Electro­
diagnostic tests are routinely performed, yet their validity is
largely unproven. EMG and NCS have been shown to be poor
predictors of symptom severity or functional impairment.56
Patients with clinical evidence of CTS and negative NCS
studies have been shown to have identical clinical improve­
ment after surgery as patients with positive NCS findings.57
Distal motor and sensory latencies greater than 4.5 and 3.5 ms,
respectively, are generally considered positive.58
Ultrasound is inexpensive, reproducible, available to all,
and actually shows compression objectively in the live human.
A recent level 1 study comparing the use of ultrasound and
electrodiagnostic testing in CTS revealed an equivalent sensi­
tivity (89%) and a greater specificity (90% vs. 80%) of ultra­
sound in accurately diagnosing CTS.59 Since ultrasound can
be performed by the surgeon in an office setting, independent
of radiological evaluation, the cost-effectiveness and safety is
promising in the diagnosis of CTS.
resolves postpartum.41 In the pediatric population, mucopoly­
saccharidoses are a frequent cause of CTS.42 To date, the only
strong evidence linking occupation to CTS has been among
operators of handheld vibratory tools.43 Scientific support for
a causative role for other repetitive work activities (e.g.,
typing) in the development of CTS is otherwise lacking.44
History
A thorough history and physical examination are central to
the diagnosis of CTS. Patients with CTS report nocturnal pain,
numbness, and tingling in the thumb and radial fingers.
Paresthesias are usually triggered by activities involving
sustained wrist flexion or extension. Shaking and wringing of
the hands tend to alleviate symptoms. Bilateral symptoms are
common. Occasionally, paresthesias can radiate proximally
along the median nerve to the forearm and may even involve
the ulnar digits.
Clinical examination
Using the clinical triad described above (muscle exam, SCT,
Tinel’s test), patients with CTS should be examined using the
manual muscle testing protocol with particular emphasis on
the median innervated muscles: FCR, FPL, FDP II and APB.
In a case of CTS, a weakness of APB may be found when
comparing to the contralateral side. Actual manifest thenar
atrophy has a high predictive value in CTS, but is not com­
monly observed.45 It is of great importance to test FCR, FPL
and FDP II strength in every patient with suspected CTS to
rule out concomitant DCS and proximal median nerve
involvement. The SCT has an estimated 82% accuracy as a
clinical provocative test in CTS,26 and is elicited by scratching
over the carpal tunnel just distal to the wrist flexion crease
(Video 24.2
). Tinel’s sign is elicited by gently percussing
over the median nerve at the carpal tunnel. A positive sign is
present if the patient describes an electrical shock sensation
in the median nerve distribution. The low specificity and
sensitivity of the sign may in part be due to the wide intra-
and interexaminer variability with which it is elicited.46
Other provocative tests that can be considered to aid in the
evaluation of CTS include the Phalen’s test and the Durkan’s
test. The Phalen’s test is performed by having the patient
place the elbow on a table and flex the wrist for 60 s. The
test is considered positive if the patient reports paresthesias
in the median nerve distribution. Durkan’s median nerve
compression test involves direct compression of the median
nerve at the carpal tunnel for 30 s. A positive test is obtained
if the patient reports numbness or tingling in at least one
of the radial digits.47 Other less frequently used provocative
tests include the reverse Phalen’s, tourniquet test and the
flick maneuver.48,49 For multiple reasons, including poor study
design, variability in outcome measures, and small datasets,
no single test has been identified to diagnose CTS consis­
tently. Of the above maneuvers, Durkan’s compression test
performed with a calibrated pressure device demonstrates
the highest sensitivity (89%) and specificity (96%).47 The
sensitivities and specificities of Tinel’s sign and Phalen’s
test are lower.50–52 Threshold sensory tests such as Semmes–
Weinstein monofilament measurements tend to be more
sensitive for detecting early CTS than innervation density
measurements.53
Clinical tips
If nerve conduction studies are positive, the patient most likely
has carpal tunnel syndrome that will respond to surgery,
particularly if the findings are profound. Surgery may still be
helpful even if the nerve conduction studies are negative,
particularly if the patient provides a classic history of
numbness at night or with prolonged wrist flexion.
Patient selection
Non-operative treatment
There is a role for both non-surgical modalities in the manage­
ment of CTS (Table 24.2).55 Splinting is the most widely used.
On the basis of two well-designed studies, splinting has been
shown to be more effective than no treatment at relieving
symptoms for at least 3 months.60,61 No difference has been
demonstrated between continuous splinting and nocturnal
splinting alone.62

531
Median nerve entrapments
Wide-awake OCTR
The wide-awake approach (local infiltration without sedation
or tourniquet) has been shown to be safe and cost-effective
and is the preferred method of the authors.69,70 Tumescent field
infiltration of 20 mL of 1% lidocaine with 1 : 100 000 epineph­
rine is performed (Fig. 24.4 and Video 24.11
). A 3-cm inci­
sion is made in line with the flexed ring finger paralleling the
thenar crease and ending just distal to the distal wrist flexion
crease. The palmar fascia and TCL are incised longitudinally
to expose the median nerve. In cases where a prominent
palmaris brevis muscle is present, one should attempt to
preserve it, dividing the TCL deep to it (Fig. 24.5). The liga­
ment and forearm fascia releases are extended distally to
divide all distal TCL fibers completely in the fat pad and
proximally beneath the wrist flexion crease for about 1 cm
into the forearm. The authors prefer to perform skin closure
using buried intradermal 5-0 absorbable monofilament
sutures, thereby obviating the need for suture removal (as
shown in video 24.4
, which also contains detailed advice
provided to patients intraoperatively). A light dressing only
is applied, as postoperative splinting has not been shown to
improve pain relief or surgical outcome.71 Patients are allowed
to remove the dressing and shower the day after surgery. A
new dressing may be applied for padding and protection for
up to a week. Patients are advised to elevate and rest the hand
for the first 2 postoperative days. In most cases, ibuprofen and
acetaminophen provide sufficient analgesia over this time.
After the second postoperative day, any residual pain is
usually the result of overexertion; a gradual return to full
activities is advised with pain serving as a guide. Most patients
can return to full work activities by 8 weeks. Patients are
advised that mild discomfort at the operative site and
decreased grip strength can persist for several more months.
Endoscopic carpal tunnel release (ECTR)
ECTR techniques were developed in an attempt to avoid
problems occasionally experienced following OCTR, namely
Steroid injection has been extensively reviewed.63 It provides
greater clinical improvement in symptoms 1 month after
injection compared to placebo.64,65 In addition, local injection
provides superior symptom relief compared to systemic
steroid administration for up to 3 months.66 Two local cortico­
steroid injections do not provide significant added clinical
benefit compared to one injection.67 Steroid injection in com­
bination with splinting has also been shown to be better than
splinting only at 6-month follow-up.68
Treatment/surgical technique
Surgery is the treatment of choice when non-surgical treat­
ments have failed or when APB weakness and/or sensory
disturbance is advanced. Release of the TCL may be performed
using an open or endoscopic technique. Open carpal tunnel
release (OCTR) remains the most common method of
decompression.
Table 24.2  American Academy of Orthopaedic Surgeons clinical practice guidelines for the treatment of carpal tunnel syndrome (CTS):
recommendations
1.
Non-surgical treatment is an option for early CTS. Surgery is an option when there is evidence of median nerve denervation
2.
A second non-surgical treatment or surgery is recommended when initial non-surgical treatment fails after 2–7 weeks
3.
There is no evidence to support specific treatment recommendations for CTS associated with diabetes, cervical radiculopathy,
hypothyroidism, polyneuropathy, pregnancy, rheumatoid arthritis, or CTS in the workplace
4a. Local steroid injection or splinting is recommended prior to treatment with surgery
4b. Oral steroids and ultrasound are also options for treatment
4c. Carpal tunnel release is recommended for treatment of CTS based on level I evidence
4d. Heat therapy does not have evidence to support its use in CTS
4e. Other non-surgical treatment modalities are not recommended for treatment of CTS
5.
Surgical treatment with complete division of the flexor retinaculum is recommended, regardless of the technique used
6.
Skin nerve preservation, epineurotomy, flexor retinacular lengthening, internal neurolysis, tenosynovectomy, and ulnar bursa
preservation are not recommended in the performance of carpal tunnel surgery
7.
Use of preoperative antibiotics is an option that may be decided upon by the surgeon
8.
Wrist immobilization is not recommended postoperatively after routine carpal tunnel release. No recommendation is made regarding
use of postoperative rehabilitation
9.
It is suggested that physicians use one or more patient response tools to assess results after carpal tunnel treatment in performing
research
Clinical tips
Most patients with carpal tunnel syndrome will experience
nocturnal numbness, or numbness with sustained wrist flexion
as occurs with driving or talking on the telephone. Patients
who experience symptomatic relief with splinting are also likely
to respond well to surgery.
Clinical tips
For almost pain-free local anesthesia using the wide-awake
approach, never advance the needle tip ahead of the
infiltrated local anesthetic. Palpate the wheal of local
anesthetic so it is firm ahead of the slowly advancing needle
tip. Remember: “Blow slow before you go” (video 24.3
).

532
SECTION III
CHAPTER 24 • Nerve entrapment syndromes
A
B
Fig. 24.4  Method of local anesthesia infiltration for the wide-awake approach to open carpal
tunnel release. (A) Up to 10 cc of 1% lidocaine with 1 : 100 000 epinephrine local anesthetic is
infiltrated superficial and deep to the antebrachial fascia of the distal volar forearm, producing a
clear wheal proximal to the planned incision. (B,C) Infiltration then continues distally deep
superficial to the proximal transverse carpal ligament under the incision. Paresthesia induction is
contraindicated as the needle can damage nerve fascicles.
C

533
Median nerve entrapments
major complications occur 1% less often than in OCTR.81
Previous prospective studies have not shown a substantial
cost difference between the techniques if the cost of ECTR
equipment is excluded.74,75,77
Outcomes and complications
While advanced thenar wasting and complete anesthesia are
not likely to resolve following surgery, pain associated with
CTS typically does, regardless of its duration. Although
response to carpal tunnel release is widely held to be worse
among elderly and diabetic patients, this has not been borne
out by a number of recent studies.82–84 Overall, outcomes fol­
lowing carpal tunnel release are excellent, with patient satis­
faction, symptom relief, and functional improvement observed
in more than 94% of cases.83,85
scar tenderness and pillar pain. Popular approaches include
the dual-portal technique of Chow and the single-portal
technique of Agee.72,73
Using the Chow technique, proximal and distal incisions
are made deep to the TCL. The endoscope and blade assembly
are passed from the proximal incision through the distal inci­
sion, deep to the TCL. The distal TCL is released using a probe
knife. A second cut is made in the midsection of the TCL with
a triangular knife and joined to the first cut using a retrograde
knife. The endoscope is then repositioned and in a similar
fashion the probe knife used to cut the proximal TCL. A ret­
rograde knife is inserted into the midsection of the TCL and
drawn proximally to complete the release.
In the Agee ECTR, a small transverse skin incision is made
at the ulnar border of the palmaris longus tendon, midway
between the flexors carpi ulnaris and radialis, and proximal
to the wrist flexion creases. A distally based forearm fascia
flap is elevated to reveal the proximal edge of the TCL. With
the wrist in extension, the endoscopic blade assembly is
inserted into the canal in line with the ring finger. The TCL is
visualized and divided distally to proximally.
OCTR vs. ECTR
Both OCTR and ECTR are practiced widely, with proponents
of both techniques continuing to debate the merits of one over
the other. A common argument in favor of ECTR over OCTR
has been reduced postoperative pain and a shorter return to
vocational activities. Although these findings have been borne
out in some studies,74–76 other studies show that any differ­
ences between techniques in patient symptoms, function, and
satisfaction equalize by 1 year.77,78 Supporters of OCTR have,
in turn, cited a higher incidence of postoperative neurovascu­
lar complications as a reason to avoid ECTR.79 More recent
studies have failed to support this higher risk in ECTR.74,75,77,78,80
Cost has been another factor in the debate between OCTR and
ECTR. A 1998 cost-effectiveness analysis comparing the two
techniques concluded that ECTR is cost-effective provided
Fig. 24.5  Preservation of prominent palmaris brevis or thenar muscles during open
carpal tunnel release. In the authors’ experience, postoperative pain and grip
strength are improved with preservation of palmaris brevis or thenar muscles
encountered during dissection with no compromise of decompression. The
transverse carpal ligament is divided deep to the muscle under direct visualization.
Clinical tips
Patients can be advised that, although carpal tunnel release
relieves most of the numbness most of the time in most
patients, it does not relieve all of the numbness all of the time
in all people. If constant numbness has been present for an
extended period of time, return of normal sensation after
carpal tunnel release is less likely. Surgery may be helpful in
alleviating shoulder, arm, elbow, or forearm pain associated
with the numbness.
Complications of carpal tunnel release include, but are not
limited to, injuries to the motor and palmar cutaneous
branches and main trunk of the median nerve; hypertrophic
scarring; pillar pain; superficial palmar arterial arch injury;
incomplete TCL release; tendon adhesions; infection; wound
hematoma; stiffness; and recurrence. The most common
complication with OCTR is pillar pain (25%), followed by
laceration of the palmar cutaneous branch of the median
nerve.86 Incomplete TCL release is the most frequent compli­
cation of ECTR.74 Recurrent CTS symptoms are seen in up to
20% of cases.87 Ultrasound is an easy and reliable tool in
evaluating the median nerve at the carpal tunnel, where an
increase in cross-sectional area, hypervascularity, and reduced
echogenicity are signs of persistent nerve compression.88
Clinical tips
All patients with failed and/or recurrent carpal tunnel release
should be examined regarding strength in the FCR, FPL, FDP
II to rule out a proximal median nerve entrapment at the elbow,
lacertus syndrome, as a possible cause of incomplete
recovery following carpal tunnel surgery (video 24.5
).
Median nerve entrapments in the elbow
and forearm
Background
Compression of the median nerve in the forearm and elbow
has traditionally been regarded as a rare entity and far less
common than CTS. Recent publications, however, are raising

534
SECTION III
CHAPTER 24 • Nerve entrapment syndromes
an awareness regarding the presence of proximal median
nerve entrapments as a cause of arm pain, hand weakness,
and possible sensory deficits within the median innervated
area.4,89 The presence of median nerve entrapments has tradi­
tionally been called the “pronator syndrome”, after the first
description by Seyffarth in 1951 of a pronator teres compres­
sion of the median nerve.90 Later, the pronator syndrome has
become a collective entity denoting a median nerve entrap­
ment that can exist from the upper arm to the distal forearm.91
With the advent of more thorough physical exams in patients
with upper extremity pain and dysfunctions, a delineation of
entrapment levels is seen. Proximal median nerve entrap­
ments can thus be divided into three separate entities: the
lacertus syndrome4; the superficialis syndrome89; and the
anterior interosseous (AIN) syndrome.92
Lacertus syndrome
Compression of the median nerve by the lacertus fibrosus, or
bicipital aponeurosis, at the level of the cubital fossa was first
described by Laha in 1978.93 It has later been described in
relation to repetitive and strenuous work with the arm in a
pronated position,94 and is slightly more common in computer
workers than manual laborers.23 In the largest published
prospective study on lacertus syndrome, women and men
were affected equally, as was the dominant/non-dominant
hand.95
Anatomy
Akin to the carpal tunnel, at the level of the lacertus fibrosus
the median nerve passes through a “tunnel”, where the
bottom is the medial trochlea of the humerus, the lateral and
medial walls are the brachialis and pronator muscles, respec­
tively, and the roof is the lacertus fibrosus (Fig. 24.6). The
lacertus fibrosus thus acts like the transverse carpal ligament,
being a strong fibrous band that may constrict the median
nerve at the level of the elbow.96 According to Sunderland,5 at
this level, the median nerve is organized such that the branches
to the pronator teres and FCR are located anteriorly, and the
branches to the FPL and FDP II, medially, whereas the sensory
branches are located more deeply in the nerve. The motor
symptoms will therefore appear before sensory symptoms in
the instance of lacertus syndrome.
History
The most common complaints in patients with lacertus syn­
drome is a loss of key- and tip-pinch strength, a loss of fine
motor skills, and sense of clumsiness (dropping objects). It is
rarely associated with transient paresthesias in the median
nerve-innervated region of the hand and there are no noctur­
nal symptoms of numbness as in CTS.23 The presence of volar
forearm pain is common in the later stages of lacertus syn­
drome, usually located in the cubital fossa and proximal volar
forearm. It may at times be mistaken for medial epicondylitis
due to the pain distribution in the medial elbow region.
Clinical examination
The clinical triad of muscle testing, SCT, and pain upon
compression will reveal the following in a patient with lacer­
tus syndrome: (1) distinct weakness when manually testing
the strength of the muscles innervated by the median nerve
distal to the lacertus fibrosus, especially the FPL, FDP II and
FCR; (2); a positive SCT over the median nerve at the level of
the lacertus fibrosus; and (3) pain upon external pressure of
the median nerve at the proximal edge of the lacertus fibrosus
(video 24.5
).
Non-operative treatment
In patients with early onset of symptoms, a trial of local tri­
amcinolone injections at the edge of the lacertus fibrosus may
have success in reducing, even eliminating, symptoms. The
effect of local cortisone is most likely a combination of reduced
swelling around the nerve, as well as an effect in reducing the
neuro-inflammatory response in the nerve.97
Wide-awake surgical release
The surgery is performed according to the wide-awake tech­
nique (video 24.5
), with an awake patient and no tourniquet:
20–30 min preoperatively, the patient is anesthetized using
30–40 mL 1% lidocaine (10 mg/mL) with epinephrine (5 µg/
mL) with 2–3 mL sodium bicarbonate (50 mg/mL) solution
added. Using a 27-inch gauge needle, the anesthesia is slowly
infiltrated from the medial elbow crease and obliquely 4 cm
distally and centrally to cover the course of the lacertus
fibrosus. A 2–3 cm transverse incision is placed in the flexion
crease of the cubital fossa, from 1 cm medial of the biceps
tendon to 2 cm lateral of the medial epicondyle. Careful dis­
section is made subcutaneously to the pronator teres (PT)
fascia, taking great care to identify and protect branches of the
medial antebrachial cutaneous nerve (MACN). The PT fascia
is incised and followed laterally, allowing exposure of the
lacertus fibrosus, which is subsequently divided. By retracting
PT medially, the median nerve is readily seen. Any focal
adherences to the underlying brachialis muscle may then be
released. At this point, the strength of the FPL and FDP II is
again tested intraoperatively before the skin is closed, as
return of muscle strength is usually immediate after proper
release of the nerve (video 24.5
).
Intraoperative examination of the superficialis sling actively
flexing on the surgeon’s small finger in the wound of the
lacertus release can delineate further compression at this
point. It could be released through a separate incision if
identified.
After cauterization, the wound is closed with intra­
dermal 4-0 monocryl sutures, a small soft dressing
applied, and immediate mobilization encouraged. Patients
with non-manual labor return to work within 1–2 days
postoperatively.
In a retrospective 10-year follow-up of surgically released
median nerves at the level of the lacertus fibrosus vs. conser­
vatively treated patients, the surgical patients had no return
of symptoms but only 30% of the conservatively treated
patients had relief of symptoms.98 The surgical release at this
level can thus be considered safe, minimally invasive, and
effective.
Superficialis syndrome – AIN syndrome
In the traditional release of pronator syndrome, this fibrous
flexor digitorum superficialis (FDS) arch has been considered
one of the important pressure points to release. About 6 cm
distal to the cubital fossa and medial epicondyle, the FDS arch

535
Median nerve entrapments
A
Brachial artery
Radial artery
Lacertus fibrosus
Median nerve
Pronator teres
Pronator teres
insertion
B
Radial artery
Median nerve
Ulnar head of
pronator teres
Reflected
humeral head
of pronator
teres
Arch of flexor
digitorum
superficialis
Fig. 24.6  Anatomy of proximal median nerve entrapments. (A) The lacertus syndrome is entrapment at the level of the lacertus fibrosus, resulting in weakness in the flexor
carpi radialis, flexor pollicis longus (FPL) and the deep flexor to the index finger (FDP II). During surgery, the lacertus fibrosus should be completely transected. (B) The
arch of the flexor digitorum superficialis (FDS) is the level of entrapment for the superficialis syndrome, with weakness in FDS IV and often paresthesias in the hand. This
arch should be completely opened when performing superficialis syndrome surgery.
is found as a fibrous structure between the PT and FDS (see
Fig. 24.6). The FDS arch is always located proximal to the
bifurcation of the main median nerve and the anterior interos­
seous nerve. Originally, the AIN syndrome was described to
occur under the fibrous arch of the FDS or the PT, but median
nerve compression at these levels will not only involve the
AIN but also the main median nerve and should be referred
to as the superficialis syndrome. Pure AIN entrapment thus
occurs distal to the FDS arch, after the bifurcation between the
AIN and the main median nerve (see Fig. 24.6). Isolated
entrapment of the AIN is the most uncommon of the proximal
median nerve entrapments.
History
Like the lacertus syndrome, the patient with a median nerve
entrapment at the FDS arch will complain of volar forearm
pain and weakness in pinch. One distinct difference in pre­
sentation is that the superficialis syndrome also is associated
with sensory disturbances within the median innervated
region of the hand.
Contrarily, the AIN presents with a pure motor weakness
and no sensory disturbance. There may be a history of forearm
pain preceding the motor weakness. If instead there is a
history of transient shoulder pain following a viral infection

536
SECTION III
CHAPTER 24 • Nerve entrapment syndromes
release, as described in the lacertus section above. The patient
flexes the long and then the ring fingers while the surgeon has
his/her fifth finger under the superficialis sling through the
lacertus wound after lacertus release. Superficialis compres­
sion can be released at the time of lacertus release through a
separate incision if identified with active movement during
surgery.
Because the AIN innervates the FPL, FDP II–III, and prona­
tor quadratus, patients with a complete AIN palsy should
exhibit no motor function in these three muscles unless a
Martin–Gruber connection or ulnar contribution to the middle
finger, FDP III, is present.101 In incomplete AIN palsy, isolated
FPL involvement is most typically observed. SCT will be posi­
tive over the branch of the AIN, about mid-forearm. Pressure
over the AIN may elicit pain, but should never elicit sensory
symptoms (negative Tinel’s test).
Non-operative treatment
The conservative management of superficialis and AIN syn­
drome is identical to that of the lacertus syndrome, with a trial
of steroid injections, physiotherapy, and activity-modification
regimes. In the event of a Parsonage–Turner as a cause of the
AIN palsy, the conservative management should also take
into consideration any possible involvement of the shoulder
girdle, such as adhesive capsulitis, to ensure a proper return
of function in the entire upper extremity.102
Surgical release
The surgical release of the median nerve at the level of the
FDS arch is usually performed using the Zancolli mini-
invasive approach89 and following the principles of wide-
awake anesthesia. Lidocaine–epinephrine 1%, 30–40 mL
buffered with 2–3 mL bicarbonate, is slowly infiltrated from
about 2 cm distal to the cubital fossa and about 5 cm distally
and centrally in the forearm, over the level of the FDS arch. A
3-cm transverse skin incision is placed over the FDS arch.
Blunt dissection is made with careful retraction of the MACN,
to the lateral edge of the PT fascia that is incised, to allow
medial retraction of the muscle. Between the PT and FDS, the
fibrous arch is found. Then the median nerve proximal to this
edge is located and the nerve followed for about 3 cm distally,
to ensure complete release.
In an AIN syndrome, following the release of the FDS arch,
a more distal approach is undertaken to securely identify and
release the AIN distal to the bifurcation from the main median
nerve. Skin closure and postoperative management follows
that of the lacertus syndrome.
Ulnar nerve entrapments
Ulnar nerve compression in Guyon’s canal
Background
Compression of the ulnar nerve in Guyon’s canal may also be
called “ulnar tunnel syndrome”.103 The most common cause
of ulnar nerve compression at the wrist is external compres­
sion by a space-occupying lesion, most commonly a gan­
glion.104 The zone within which the ganglion arises can
typically be determined on the basis of patient symptoms and
that precedes the motor weakness, the surgeon should con­
sider the possibility of Parsonage–Turner syndrome (brachial
neuritis or neuropathic amyotrophy).99,100
Clinical examination
The muscle testing of a superficialis syndrome will reveal a
weakness in FPL and FDP II but, contrary to lacertus syn­
drome, a distinct weakness in FDS IV and no weakness in the
FCR. The SCT is positive at the level of the FDS arch, and
external compression over the median nerve will cause numb­
ness in the hand. Tinel’s is often positive at the same level.
Superficialis sling compression of the median nerve can also
be palpated internally at the time of a wide-awake lacertus
(C) Anterior interosseous nerve (AIN) syndrome is a rare
compression of the motor nerve, resulting in FPL, FDP II and pronator quadratus
weakness but no paresthesias. After releasing the FDS arch, the AIN is followed
distally to ensure proper release.
C
Radial artery
Median nerve
Anterior interosseous
nerve
Ulnar head of
pronator teres
(reflected)
Reflected
humeral head
of pronator
teres
Arch of flexor
digitorum
superficialis
(reflected)
Fig. 24.6, cont’d

537
Ulnar nerve entrapments
Zone II is defined by the deep motor branch of the ulnar
nerve. It extends from the level of the bifurcation to the fibrous
arch formed by the flexor and abductor digiti minimi muscles
radially and distally. Soon after passing under the fibrous
hypothenar arch, the deep motor branch wraps radially
around the hook of the hamate and passes beneath the piso­
hamate ligament, where it can become compressed. The motor
branch innervates the interossei, lumbricals IV–V, adductor
pollicis, and deep head of the flexor pollicis brevis.
Zone III is located ulnar to zone II and is bordered volarly
by palmaris brevis and dorsally by the hypothenar muscles.
The superficial branch contained in zone III is predominantly
sensory with only a few motor fibers to palmaris brevis. Loss
of palmaris brevis function is rarely, if ever, noticed by patients,
and so for practical reasons the superficial branch is consid­
ered to be purely sensory.
History
Patients with ulnar nerve compression in Guyon’s canal
may present with a history of paresthesias in the small and
ring fingers, ulnar-sided wrist pain, decreased grip strength,
or clawing of the ring and little fingers. A history of wrist
trauma, long-distance cycling, or vocational exposure to
repetitive hand vibration is not uncommon. Patients with
ulnar nerve entrapment at the wrist may also suffer from
CTS; carpal tunnel release can often eliminate ulnar symp­
toms as it has been shown to decompress Guyon’s canal
indirectly.110
Clinical examination
The manual muscle testing should include an evaluation of
the FDP V to rule out a more proximal involvement of the
ulnar nerve (at elbow level). Furthermore, the muscle exam
will help delineate the level of Guyon’s canal involvement.
Weakness of the ADM is associated with a zone I entrapment;
normal strength in the ADM but weakness in the first dorsal
interosseus signifies a zone II entrapment.
Physical examination should also include a thorough
sensory assessment. The absence of dorsoulnar hand sensa­
tion suggests a site of compression proximal to the branching
of the dorsal sensory branch of the ulnar nerve. The SCT can
also be used to stage the entrapment in Guyon’s canal, as it
will be positive at the wrist crease level in zone I, at the level
of the hook of the hamate in zone II, and in the ulnovolar
region distal to the pisiform in zone III. Tinel’s test will be
positive for zone I and III, but negative in a zone II
entrapment.
In addition to the above testing, an Allen test should be
performed to assess for potential ulnar artery thrombosis
(hypothenar hammer syndrome). Palpation of the ulnar wrist
may reveal a ganglion, tumor, aneurysm, or hook of hamate
fracture.
Ultrasound is a useful tool in Guyon’s canal entrapments
as it can directly reveal potential ganglion cysts as well as
evaluate the blood flow in the ulnar artery.111 Computed
tomography and magnetic resonance imaging (MRI) is of use
primarily in suspected carpal fractures or in the absence of
ultrasound. Electrodiagnostic tests may be an adjunct to
confirm the level of entrapment,112 but physical examination
is the foundation for proper diagnosis.
clinical examination alone.105 Following space-occupying
lesions, entrapment in Guyon’s canal may also be caused by
excessive or repetitive external pressure to the ulnovolar
aspect of the hand. Hypothenar hammer syndrome is one
such instance where repetitive trauma can be associated with
compression of the ulnar nerve in Guyon’s.106 Another
common sports-related cause of entrapment is the “handlebar
palsy”, where long-distance cyclists develop ulnar nerve
entrapment in Guyon’s canal due to excessive pressure on the
hand.107 Other less common causes of ulnar nerve compres­
sion at Guyon’s canal include rheumatoid arthritis and carpal
(in particular, hook of hamate) fractures.108,109
Anatomy
Guyon’s canal is defined radially by the hamate, volarly by
the volar carpal ligament, dorsally by the TCL and the piso­
hamate ligament, and ulnarly by the pisiform, flexor carpi
ulnaris (FCU) tendon, and the proximal belly of the ADM.
More distally, nerve branches course deep to the hypothenar
muscles (Fig. 24.7). Depending on the location of the compres­
sion with Guyon’s canal, symptoms may be a combination of
motor and sensory (zone I), purely motor (zone II), or purely
sensory (zone III).
Zone I contains both sensory fibers to the ulnar ring and
little fingers and motor fibers to the hypothenars and interos­
sei, and extends from the proximal edge of the volar carpal
ligament to the bifurcation of the ulnar nerve.
Fig. 24.7  Guyon’s canal. The relationship of the ulnar nerve and artery to the hook
of hamate, pisiform, opponens digiti minimi, abductor digiti minimi, flexor digiti
minimi, and flexor carpi ulnaris is clearly depicted.
Ulnar artery
Trans carpal
ligament
Opponens digiti minimi
Abductor digiti minimi
Flexor digiti minimi
Hamate
Volar carpal
ligament (cut)
Flexor carpi ulnaris
Pisiform
Piso-hamate
ligament (cut)
Ulnar nerve (deep branch)
Ulnar nerve
(superficial
branch)

538
SECTION III
CHAPTER 24 • Nerve entrapment syndromes
cubital tunnel syndrome is at the ligament of Osborne, just
distal to the medial epicondyle.27
History
A thorough history should include the onset of symptoms,
presence of grip or pinch weakness, numbness, aggravating
and alleviating activities, comorbidities (i.e., diabetes, periph­
eral neuropathies), and previous elbow trauma. Perhaps the
single most important feature on history, however, is the
chronicity of the symptoms. Intermittent symptoms elicited
by elbow flexion are likely due to transient ischemia of the
nerve and will respond well to treatment. Constant numbness
or weakness responds less predictably to surgery.
Clinical examination
The manual muscle testing is important to exclude more
proximal nerve involvement, and should always include a
thorough examination of shoulder and elbow strength. In the
presence of a cubital tunnel syndrome, the focus of the muscle
exam should be on the FDP V and ADM to delineate if the
entrapment is at the elbow or wrist level. A cubital tunnel
syndrome will correspond to a weakness of both the FDP V
and ADM.
In addition to the muscle exam, the SCT is of use in staging
the level of ulnar nerve entrapment at the cubital tunnel. The
most common site of entrapment, and the focus of potential
nerve release, is at Osborne’s ligament.27 The Tinel’s sign is
also of aid in staging the site of nerve entrapment.
Another provocative test is the elbow flexion pressure test.
The sensitivity of Tinel’s sign is 70%, while that of the elbow
flexion pressure test is 98%.114 The latter test is considered
positive if symptoms are elicited after 60 s of digital pressure
applied over the cubital tunnel with the elbow in flexion.
Radiographs may be obtained to assess for elbow arthritis
or post-traumatic deformity. Electrodiagnostic testing can be
helpful to confirm the diagnosis or rule out a peripheral
neuropathy or other sites of compression. An ulnar nerve
motor conduction velocity across the elbow of less than
50 m/s is generally considered positive. Electrodiagnostic
results must be interpreted carefully, however, as they have
been shown to have a false-negative rate of more than 10% in
the setting of cubital tunnel syndrome.33 Patients with clinical
symptoms but negative electrodiagnostic results should still
be considered for surgical release as this renders positive
outcomes and resolution of symptoms.115
Non-surgical treatment
Patients with mild or intermittent symptoms can often be
successfully treated with local steroid injections, activity modi­
fication, splinting, and physiotherapy (nerve mobilization
techniques).116 Nocturnal splinting to prevent elbow flexion of
more than 45° can be particularly helpful. Surgical intervention
should be considered if non-operative modalities fail to
improve symptoms after more than 2–4 months or if symptoms
worsen during the period of conservative treatment.113
Surgical release
Controversy persists as to the optimal surgical management
of cubital tunnel syndrome, a fact underscored by the
Surgical release
Although conservative methods such as non-steroidal anti-
inflammatory drugs (NSAIDs) and splinting are often an
option, if an anatomic cause of nerve compression is present,
surgical intervention is warranted. A 6–7-cm incision is
marked between the hook of the hamate and pisiform extend­
ing into the ulnar forearm. Proximally, the FCU is retracted
ulnarly to expose the ulnar artery and nerve that are then
traced distally. The volar carpal ligament and palmaris brevis
are incised. A careful examination is made for any ganglion
or tumor. The deep motor branch is subsequently decom­
pressed by dividing the fibrous edge of the hypothenar
muscles and any fascial bands arising from the hook of
hamate. The sensory branch is then traced superficial to the
fibrous hypothenar arch where it is most commonly impinged
upon by an aneurysm or thrombosis of the ulnar artery or a
ganglion in Guyon’s canal.
Postoperatively, patients are allowed to remove the dress­
ing and shower the day after surgery. A dressing may be
reapplied for padding and protection for a week. Patients can
return to work when they no longer experience pain while
performing their duties, usually by 8 weeks.113
Cubital tunnel syndrome
Compression of the ulnar nerve at the cubital tunnel is very
common and second only to CTS in incidence. The diagnosis
of cubital tunnel syndrome is primarily clinical, as electrodi­
agnostic tests can often be negative despite significant symp­
toms and exam findings.
Clinical tips
Patients can be advised that the results following cubital
tunnel surgery are not as good as those following carpal
tunnel surgery and that numbness (or muscle power) may not
improve significantly after surgery. By performing cubital tunnel
surgery, we may at least prevent further nerve damage and
disease progression.
Anatomy
In the upper arm, the ulnar nerve travels posterior to the
medial intermuscular septum anterior to the medial head of
the triceps. The arcade of Struthers is a deep brachial fascial
band that joins the intermuscular septum and invests the
ulnar nerve approximately 8 cm proximal to the medial epi­
condyle. This is a rare but potential site of ulnar nerve com­
pression about the elbow. The medial antebrachial cutaneous
nerve passes posterior to the ulnar nerve immediately proxi­
mal to or at the epicondyle; injury to this nerve can result in
significant postoperative neuroma and pain. The ulnar nerve
travels posterior to the medial epicondyle and medial to the
olecranon to enter the cubital tunnel. The tunnel roof com­
prises a tight fascial layer that extends from the FCU to the
arcuate ligament of Osborne, while the floor is defined by the
ulnar collateral ligament. Upon exiting the cubital tunnel, the
ulnar nerve travels into the forearm between the ulnar and
humeral FCU heads, then deep to the deep flexor pronator
aponeurosis. The most common site of entrapment for the

539
Radial nerve entrapments
numerous techniques currently used by experienced surgeons
to treat the condition. These techniques include in situ and
endoscopic decompression, submuscular transposition, intra­
muscular transposition, subcutaneous transposition, and/or
medial epicondylectomy. Since the most common site of
nerve compression is just distal to the medial epicondyle, at
Osborne’s ligament, our preferred approach is a simple, in situ
decompression using wide-awake techniques.
In situ decompression – the authors’ preferred technique
We prefer to perform this procedure using the wide-awake
approach (local infiltration without sedation or tourniquet).
If the release is planned to the Osborne’s ligament and distal
of the medial epicondyle alone, the following is used: field
infiltration of 20–40 mL of 1% lidocaine with 1 : 1–200 000
epinephrine buffered with 2–4 mL of bicarbonate, infiltration
from the level of the sulcus to about 5 cm distal of the medial
epicondyle. After waiting 20–30 min, a 3-cm skin incision is
made just distal of the sulcus.117 Blunt dissection is made
to the FCU fascia where Osborne’s band is identified. Just
proximal of this, the ulnar nerve can be seen and followed
distally as Osborne’s and other constricting bands are
released (Video 24.12
).
Simple decompression
In a patient where more proximal ulnar nerve involvement is
suspected, we prefer a simple decompression (videos 24.6

and 24.7) with the use of 0.5–1% lidocaine with 1 : 200 000
epinephrine beginning 8–10 cm proximal to the medial epi­
condyle to ensure anesthesia in the MACN distribution. Care
should be taken to avoid branches of this nerve during sub­
sequent dissection. Beginning proximally, the arcade of
Struthers is released, followed by Osborne’s ligament and the
FCU fascia. The ulnar nerve is left undisturbed in its bed. The
elbow is placed through a range of motion to check for any
residual compression sites or subluxation of the nerve. If the
latter is present, we prefer to perform a medial epicondylec­
tomy (see below) to ensure that the ulnar nerve rolls smoothly
over the medial border of the elbow.
Endoscopic decompression
Endoscopic decompression techniques make use of a small
15–35-mm incision over the ulnar nerve at the level of the
condylar groove.118–120 Tunneling forceps are used to create a
space superficial to the fascia covering the nerve and deep to
the subcutaneous tissue. An endoscope is placed in this space
and blunt scissors used to release any points of constriction
over the nerve under direct visualization.
Submuscular–subcutaneous transposition
With elbow flexion, the ulnar nerve is placed under tension
and compression as the cubital tunnel volume decreases. The
goal of transposition is to move the nerve anterior to the axis
of elbow flexion, thereby decreasing tension on the nerve.
Critics of this technique feel that dissection of the nerve from
its bed compromises the segmental blood supply of the
nerve.121
In the submuscular transposition, the proximal nerve is
identified and traced distally following release of the arcade
of Struthers. To prevent the formation of a new compression
site proximally, a segment of the intramuscular septum is
excised. The nerve is then unroofed to the level of the deep
flexor pronator aponeurosis. The nerve is dissected free from
its bed and transposed anterior to the medial epicondyle. The
motor branches to the FCU and the FDP are preserved. The
flexor pronator muscle mass is divided 1–2 cm distal to
the medial epicondyle. The median nerve must be identified
and preserved. The flexor pronator mass is repaired over the
transposed nerve with a stepwise lengthening technique to
avoid causing a new compression site.
In the subcutaneous transposition, instead of elevating the
flexor pronator mass, the ulnar nerve is instead maintained in
its transposed position by suturing the loose epineurium to
the forearm fascia.
Medial epicondylectomy
The medial epicondylectomy technique is primarily used
following a simple decompression with a tendency for
ulnar nerve subluxation. The principles of anesthesia and
nerve release follow that of the simple decompression. The
medial epicondyle is exposed in a subperiosteal plane,
maintaining the origin of the flexor pronator mass with the
periosteum. The anteromedial edge of the epicondyle is
scored with an osteotome. The epicondylectomy is performed
along a plane midway between the sagittal and coronal
planes of the humerus, all the while preserving the attach­
ments of the ulnar collateral ligament. The flexor pronator
origin is then reattached over the epicondylectomy site113
(Fig. 24.8).
Outcomes and complications
Controversy over the optimal operative management of
cubital tunnel syndrome is ongoing, with numerous compara­
tive studies demonstrating no statistical difference in out­
comes with any given technique. Simple decompression has
been shown to be effective in treating cubital tunnel syndrome,
with results equivalent to those of anterior transposition.122–124
Goldfarb et al. recently demonstrated a 93% success rate with
in situ decompression.125 Similarly, a retrospective study
comparing medial epicondylectomy alone with medial
epicondylectomy and anterior subcutaneous transposition
showed no statistical differences.126
Recurrent or unrelieved symptoms are much more frequent
than with CTS. Predictors of revision surgery include previ­
ous elbow fractures and should be assessed for prior to plan­
ning surgery.127 The posterior branch of the MACN is at
potential risk of injury, and can result in a painful neuroma
and hyperesthesia.128 Ulnar nerve subluxation following
simple decompression can lead to persistent pain. Hematoma
is more frequently observed following the endoscopic tech­
nique than open approaches.119,120 Medial epicondylectomy is
complicated by persistent elbow pain in up to 45% of
patients.129
Radial nerve entrapments
The radial nerve originates from the posterior cord in the
brachial plexus. It traverses posterior of the shoulder and
upper arm, transverses into the anterior compartment
through the lateral intermuscular septum (LIS) in the distal

540
SECTION III
CHAPTER 24 • Nerve entrapment syndromes
Wartenberg’s syndrome – entrapment of
the SBRN
Anatomy
The SBRN travels down the forearm immediately deep
to the BR. It emerges into the subcutaneous plane
approximately 9 cm proximal to the radial styloid by passing
between BR and extensor carpi radialis longus (ECRL)
(Fig. 24.9). It is at this arcade that the nerve becomes com­
pressed. The SBRN provides sensation to the dorsum of the
three radial digits to the level of the proximal interphalangeal
joints.
History and clinical examination
Patients with Wartenberg’s syndrome report isolated pain
or dysesthesias over the dorsoradial aspect of the hand.
The presence of motor weakness suggests a more proximal
site of compression. There may be a preceding history of
trauma to the area (i.e., handcuffs, forearm fracture). It is
important to differentiate Wartenberg’s syndrome from de
Quervain’s tenosynovitis, as both may present with radial
wrist pain.130 Since Finkelstein’s test will elicit pain in both
of these diagnoses, it may further lead to a misinterpreta­
tion of symptoms.131 The key differences between the two
lie in the presence of a positive Tinel’s test at the BR–ECRL
arcade in Wartenberg’s syndrome and no pain upon palpa­
tion of the first dorsal extensor compartment.132 A positive
SCT will usually also be present at the level of the BR–ECRL
arcade.
Non-surgical treatment
Spontaneous resolution of symptoms is common in Wart­
enberg’s syndrome. Indeed, many cases respond by simply
eliminating the inciting factor, such as a tight watchband
or bracelet. Rest, splinting, and NSAIDs are also effec­
tive. Evidence to support the use of corticosteroids is
limited and should be considered carefully, as steroid
injections at this level may cause subcutaneous and skin
atrophies.133
Surgical release
In patients who fail to respond to conservative treatment,
surgical decompression may be considered. Wide-awake
surgical technique using 10–20 mL lidocaine–epinephrine is
advantageous as the patient then can cooperate during
surgery to ensure proper gliding of the SBRN following
release. A longitudinal incision is made from 5 cm proximal
of the radial styloid and 4–5 cm proximally, making sure to
stay slightly volar to the Tinel’s sign, thereby avoiding injury
to the lateral antebrachial nerve and preventing tethering of
the incision scar over the superficial radial nerve. The fascia
between the brachioradialis and ECRL is divided and the
superficial radial nerve carefully freed from its bed. At times,
a radial slip of the BR tendon must be removed to allow
adequate passage of the nerve. In addition to nerve gliding,
postoperative care may involve a desensitization program. An
overall success rate of 74% has been reported following surgi­
cal decompression.130
forearm and continues deep under the brachioradialis (BR)
where it divides into the posterior interosseous nerve (PIN)
and sensory branch of the radial nerve (SBRN). Along its
course, the radial nerve may become compressed at two
locations in the upper arm, three in the forearm, and one at
the wrist. In this section, we will describe four of the more
common radial nerve entrapments encountered: two in the
upper arm – triangular interval syndrome and lateral inter­
muscular syndrome; one in the forearm – radial tunnel syn­
drome (PIN entrapment); and Wartenberg syndrome (SBRN
entrapment).17
Fig. 24.8  Medial epicondylectomy technique. (A) The ulnar nerve is
protected while the common flexor pronator origin is elevated from the medial
epicondyle. (B) The proper plane of the osteotomy is between the sagittal and
coronal planes.
A
B
Ulnar nerve
Common flexor pronator origin
Medial epicondyle
Anterior part of ulnar
collateral ligament (cut)
Posterior part of ulnar
collateral ligament

541
Radial nerve entrapments
History
RTS is frequently found in conjunction with, or misdiagnosed
as, lateral epicondylitis,140 with a reported prevalence of 95%
failed epicondylitis-treated patients in a series of surgically
released RTS.23 It is not uncommon that both conditions may
exist in the same patient, and in our experience, RTS should
always be considered in cases where lateral epicondylitis
patients have failed to respond to conservative treatments.
The most common complaint in RTS is pain in the dorsal
and proximal aspect of the forearm, with pain presenting
primarily after exertion and at night. In lateral epicondylitis,
tenderness is localized to the ECRB insertion, while in radial
tunnel syndrome the point of tenderness is 3–4 cm distal over
the mobile wad.141 In a retrospective review of surgically
treated RTS, the syndrome was found to be more common in
men, manual workers, and affecting the dominant hand.23
Clinical examination
The most superficial fascicle in the radial nerve at the level of
the arcade of Frohse is the branch to the ECU.5 Based on
this, the testing of strength in the ECU has been reported as
a reliable clinical test (video 24.8
).142,143 With the patient
seated, shoulder at 90° elevation and extended elbow, the
patient ulnarly deviates the wrist. The examiner places one
hand over the radial aspect of the distal radius, the other on
the ulnar side of the hand, and then asks the patient to resist
as the examiner radially deviates the wrist.23 Always compare
the strength in the healthy arm before testing the affected arm
to facilitate examination and diagnosis. SCT is positive at the
level of the arcade of Frohse, about three fingerbreadths distal
to the lateral epicondyle, and pain upon compression is
evident at the same level.
Radial tunnel syndrome – PIN compression in
the proximal forearm
Radial nerve entrapment in the proximal forearm, at the
arcade of Frohse, the fibrous proximal edge of the supinator
muscle,134 is referred to by several names: radial tunnel syn­
drome (RTS); posterior interosseous nerve (PIN) syndrome;
and supinator syndrome. Regardless of label, this compres­
sion signifies an entrapment of the PIN.
Anatomy
The PIN arises from the bifurcation of the radial nerve in the
proximal forearm. The PIN has traditionally been considered
a “pure motor nerve”, which is not entirely correct. While it
is true that the PIN contains the motor innervation to the
forearm extensors distal to the elbow and the abductor pollicis
longus, the terminal branch of the PIN contains important
sensory innervation of the dorsal wrist joint,135 and is a source
of both proprioceptive136 and nociceptive137 afference from the
wrist.
The PIN does not innervate the ECRL, ECRB, BR, or anco­
neus muscles; these muscles instead receive their innervation
from the main radial nerve. Immediately distal to the bifurca­
tion, the PIN travels through the radial tunnel, a 5-cm space
originating at the level of the radiocapitellar joint and travers­
ing between the superficial and deep layers of the supinator
muscle.138
Within the area of the radial tunnel there are described five
potential sites of compression: (1) fibrous bands to the radio­
capitellar joint between the brachialis and brachioradialis; (2)
the recurrent radial vessels, or so-called leash of Henry; (3)
the proximal edge of the ECRB; (4) the proximal edge of the
supinator, or so-called arcade of Frohse; and (5) the distal edge
of the supinator. The arcade of Frohse is by far the most
common site of PIN compression, where high pressures (up
to 200 mmHg) on the nerve may be elicited during active
contraction of the supinator muscle.139 Compression of the
PIN at the distal edge of the supinator is exceedingly rare and
should be considered an entirely separate nerve entrapment
as it presents with completely different symptoms than the
RTS.
Fig. 24.9  Anatomy of the superficial sensory branch of the radial nerve. The fascia between the extensor carpi radialis longus and brachioradialis is released in patients
with Wartenberg’s syndrome.
Superficial branch of radial nerve
Extensor retinaculum
Lister’s tubercle
Extensor pollicis longus
Extensor pollicis brevis
Abductor pollicis longus
Styloid process
5.1cm
9.0cm
Extensor carpi radialis brevis tendon
Extensor carpi radialis longus tendon
Brachioradialis
Clinical tips
In a patient with chronic lateral epicondylitis, “tennis elbow”,
that fails to respond to conservative treatments, always test
the strength of the extensor carpi ulnaris (ECU). Weakness of
the ECU is indicative of a radial tunnel syndrome, a diagnosis
that is a source of pain in the lateral elbow and proximal
forearm and frequently misdiagnosed as lateral epicondylitis.

542
SECTION III
CHAPTER 24 • Nerve entrapment syndromes
and about 5 cm distally and obliquely. We also inject 10 mL
lidocaine–epinephrine in the volar aspect of the brachioradia­
lis muscle, over the volar aspect of the radial nerve, to block
possible pain sensation when releasing the PIN toward the
volar aspect of the supinator.
An oblique dorsal incision is made distal to the lateral epi­
condyle. Following incision of the forearm extensor fascia,
blunt dissection is performed between the ECRB/L, and the
muscles retracted. Identify the SBRN and follow this proxi­
mally to the radial nerve bifurcation to identify the PIN. This
can then be followed distally, to the point where it enters into
the arcade of Frohse, beneath the proximal edge of the supina­
tor. Release 2–3 cm of the proximal supinator fascia to complete
the neurolysis. Immediate mobilization is encouraged, but
limited to 1 kg loading during the first 2 weeks postopera­
tively. Full load is generally allowed 4 weeks postoperatively.
Outcomes following surgery
Hashizume et al. demonstrated full recovery in 16 of 17
patients who underwent surgical decompression of the PIN
after symptom onset.146 Hagert and Hagert reported complete
return of ECU strength and pain relief in 40 of 45 patients
released (88%).23 Interestingly, Simon Perez et al. reported
identical results in their recent publication, with good to
excellent results in 37 of 42 patients (88%).147
In their systematic review of observational studies, Huis­
stede et al. noted the success of surgical decompression ranged
from 67% to 92%.148 This variability in success rates may be
due in part to the presence of concomitant lateral epicondylitis
in some patients; other studies have shown poorer outcomes
among patients with coexistent lateral epicondylitis.140,149
Lateral intermuscular syndrome – radial
compression in the distal upper arm
Anatomy
In the distal upper arm, as the radial nerve passes from the
dorsal to the volar compartment of the upper arm, it passes
through the LIS. This septum is a taut fascia, covering the
lateral aspect of the humerus from the deltoid insertion proxi­
mally, to the lateral epicondyle distally. The radial nerve
pierces the LIS approximately 10 cm proximal to the lateral
epicondyle150 to exit between the brachialis and BR volarly
(Fig. 24.11).
History and clinical examination
The primary complaint is of an aching pain in the distal,
lateral upper arm.151 The pain is usually aggravated with
physical exertion, such as repetitive elbow extension/flexion.
This type of radial nerve entrapment is most commonly
encountered in manual laborers and athletes.151,152
When performing the muscle exam, a pattern of muscle
weakness involving wrist extension and thumb/index finger
extension is found (video 24.9
). It is important to thoroughly
examine the triceps strength, as simultaneous weakness of the
triceps will denote a more proximal radial nerve involvement.
Positive SCT is found where the radial nerve pierces the
septum, about 10 cm proximal of the lateral epicondyle. The
level of positive SCT and maximum point of tenderness upon
Non-operative treatment
An initial treatment of local corticosteroid at the level of the
arcade of Frohse may be therapeutic. Indeed, one study
showed a 72% response rate to local injection in patients with
radial tunnel syndrome at 6 weeks of follow-up; in the major­
ity of these responders, pain relief persisted for more than 2
years.144 Conservative management such as avoidance of
aggravating activities, hand therapy management (stretching,
nerve gliding, splinting), adaptation of the workplace, and
use of NSAIDs have been shown to be helpful.145
Surgical release
Surgery is recommended for RTS if there is no appreciable
improvement in motor function by 2–3 months, or even earlier
in cases of nocturnal and residual pain. Our preferred tech­
nique for is the posterior approach, as this allows an easy
exposure of the proximal edge of the supinator, ability for
possible concomitant release of a tense ECRB edge, and results
in more aesthetically pleasing scars as compared to the volar
approach (Fig. 24.10).
The procedure is usually done in general anesthesia and
using a tourniquet. However, the wide-awake approach is
also possible. If performing a wide-awake release, 20–30 mL
lidocaine–epinephrine should be infiltrated in the dorsal
proximal forearm, from just distal to the lateral epicondyle
Fig. 24.10  The posterior approach to the radial tunnel. The plane between the
extensor carpi radialis and longus is developed. The proximal edge of the supinator
is released, slightly to the side of the nerve to avoid direct scarring. ECRB, Extensor
carpi radialis brevis; ECRL, extensor carpi radialis longus.
A
B

543
Radial nerve entrapments
surgical procedure. The skin incision is planned from about
5 cm proximal of the lateral epicondyle and about 10 cm in a
proximal direction. Perform blunt dissection to the triceps,
incise the fascia, and retract the muscle posteriorly. Identify
the posterior antebrachial cutaneous nerve in the distal aspect
of the wound, superficial to the fascia. Follow the cutaneous
nerve proximally, as it will lead to the radial nerve. After
identifying the bifurcation, the main radial nerve can be fol­
lowed distally while releasing constricting fibrous bands
compressing the nerve at the LIS.17 The patient is allowed to
start immediate motion without load to allow nerve gliding
through the septum. Manual work is restricted until 4–6
weeks postoperatively.
Triangular interval syndrome – radial
compression in the proximal upper arm
Anatomy
In the proximal upper arm, just distal to the shoulder girdle,
the radial nerve passes through the triangular interval that is
bordered medially by the long head of the triceps, laterally by
the lateral head of the triceps, and by the teres major cranially
(Fig. 24.11). Entrapment of the radial nerve at this level is rela­
tively rare but has been described in physically active adults,153
and is sometimes referred to as the triangular interval syn­
drome (TIS).154
History and clinical examination
Pain of a dull and aching character located to the dorsolateral
aspect of the upper arm, slightly distal to the axilla, is the
principal symptom in radial nerve entrapment at this level.
The patient may describe worsening of pain following strenu­
ous use of the triceps, either in relation to work or athletic
activity. Nocturnal pain is common. Intermittent paresthesias
in the dermatome of the radial nerve, from the upper arm into
the forearm, may also occur.
Like the lateral intermuscular syndrome described above,
the manual muscle testing will reveal weakness of wrist
and finger extension, but also when testing the strength in
the triceps. The triceps is examined with the patient in a
seated position, adducted arms and elbows flexed to 90°.
The examiner holds underneath the forearms of the patient
from behind, while the patient tries to push the arms beyond
90° flexion. If the symptoms have persisted over time, elec­
trodiagnostic examinations can be helpful to reveal EMG
changes in the triceps indicative of a proximal radial nerve
entrapment.
Non-surgical treatment
As with other radial nerve entrapments, the principal of
conservative management includes local steroid injections at
the site of the triangular interval, activity modifications, and
physiotherapy. In a majority of instances, the conservative
management will be successful in resolving the pain.
Surgical release
If the patient has failed conservative management for about
3 months and pain is persistent, surgical management is
indicated.
compression over the nerve will guide the surgeon in plan­
ning the level of surgical release.
Non-surgical treatment
In an acute onset of lateral upper arm pain and weakness, a
resolution of symptoms can be expected with local steroid
injections, NSAIDs, activity modifications, and rest. In a
majority of patients, the onset of symptoms is more gradual.
Conservative management should always be attempted
before proceeding to surgical release.
Surgical release
The procedure is usually done under general anesthesia. The
use of a tourniquet is optional, but generally facilitates the
Fig. 24.11  The anatomy of the radial nerve in the upper arm. Proximally, the radial
nerve enters into the triangular interval, bordered by the teres major cranially, the
long head of triceps medially and the lateral head laterally. Distally, the radial nerve
passes through the lateral intermuscular septum to exit between the brachialis and
brachioradialis.
Teres major
Long head triceps
Lateral head triceps
Lateral intermuscular
septum
Brachialis
Brachioradialis
Radial nerve
Radial nerve
Deltoid

544
SECTION III
CHAPTER 24 • Nerve entrapment syndromes
Clinical tips
In a patient with clinical signs of high radial nerve involvement
(weakness in the triceps, wrist and finger extension,
paresthesias in the radial innervated region), always
perform a muscle exam to test the strength in shoulder
abduction. Concomitant axillary nerve entrapment and high
radial nerve entrapment may exist and should be treated
simultaneously.
Fig. 24.12  Anatomic boundaries and contents of the
quadrilateral space.
Acromion
Humerus
Axillary nerve
(C5,6)
Posterior circumflex
humeral artery
Radial nerve
Triceps brachii
lateral head
Triceps brachii long head
Teres minor
Teres major
Posterior cord
Deltoid
Supraspinatus
Infraspinatus
In general anesthesia and with the patient in a semi-prone
position, a dorsolateral skin incision is performed from
the distal edge of the deltoid and about 5–6 cm distally.
If the patient has a concomitant axillary nerve entrap­
ment, the skin incision used for the axillary release may be
extended distally. The edge of the posterior deltoid muscle
is identified as the most superficial and cranial muscle.
By lifting this edge, the teres major (TMa) can be identi­
fied underneath. The radial nerve is seen just distal to the
edge of TMa, before it enters into the triangular interval. A
muscular septum connecting the lateral and long heads of
the triceps is the primary cause of compression at this level.
The fascial edge is released while carefully protecting the
radial nerve. Skin closure and postoperative management
is identical to that described in the lateral intermuscular
syndrome.
Other nerve compressions of
the upper extremity
Axillary nerve entrapment
Anatomy and etiology
The quadrilateral space (QS) is defined by the teres minor
(TMi) superiorly, the neck of the humerus laterally, the long
head of triceps medially, and the upper border of TMa inferi­
orly (Fig. 24.12). The axillary nerve and the posterior circum­
flex humeral artery (PCHA) travel through this space. In the
QS, the nerve branches into an anterior division that inner­
vates the middle and anterior deltoid, and a posterior division.
The posterior division supplies motor innervation to the
posterior deltoid and TMi and is the portion most commonly
compressed.
Reported causes of entrapment include ganglion, muscle
hypertrophy, scapular fracture, and glenoid labral cysts;
however, fibrous bands are the most common cause of
compression.155–159 Compression of the axillary nerve in the QS
is a nerve compression most commonly found in young active
adults, such as overhead-throwing athletes.160,161 Axillary
nerve compression has also recently been highlighted as a
possible cause of shoulder pain in spinal cord-injured patients
where manual wheelchair propulsion appears to predispose
to hypertrophy and scarring of the quadrilateral space.162

545
Other nerve compressions of the upper extremity
History
Patients with QS syndrome present with a gradual increase
in diffuse pain over the posterior aspect of the shoulder, com­
monly nocturnal pain with an inability to sleep on the affected
shoulder. Paresthesias over the deltoid may also be a com­
plaint, as is a feeling of weakness in shoulder strength and
endurance.17,163
Clinical examination
The manual muscle testing will reveal a weakness in the
posterior deltoid when comparing to the contralateral side
(video 24.10
). With the patient seated, arms elevated to 90°
and slightly abducted, the patient is asked to resist as the
examiner pushes on the forearms inward. It is important to
rule out weakness of the pectoralis, as combined weakness of
pectoralis and posterior deltoid is indicative of a brachial
plexus affliction. Furthermore, strength in the infraspinatus
should be tested, as a combined posterior deltoid and infra­
spinatus weakness indicates a C5/C6-radiculopathy, or a
combined axillary and suprascapular compression, rather
than an isolated axillary nerve entrapment (Fig. 24.13).
When performing the SCT test, scratching posteriorly over
the QS may elicit a positive response. Tenderness is usually
noted over the QS posteriorly. In severe cases, wasting of the
deltoid may be present.
Other diagnostic tools
EMG has been shown to be insensitive but specific for QS
syndrome.164 Originally, angiography was considered the
investigation of choice, as PCHA occlusion was considered
pathognomonic of the condition.163 However, as fibrous bands
and scarring are the most common cause of entrapment,
angiography is usually negative. MRI findings of TMi atrophy
and presence of fatty infiltrations may also confirm the diag­
nosis.165,166 Recently, the use of ultrasound to look for fatty
infiltrations in the TMi and performing Doppler examination
of the PCHA has been advocated as a reliable and cost-effective
modality.167
Fig. 24.13  Clinical image. Patient with right-sided supraspinatus (arrows) and
posterior deltoid (arrowheads) atrophy due to C5–C6 radiculopathy.
Non-surgical treatment
In cases of early onset QS syndrome, an initial trial of steroid
injections, activity modifications, NSAIDs, and strengthening
exercises are often effective in relieving pain and restoring
function. In patients with significant deltoid atrophy or with
a clear structural compression, however, a surgical approach
is indicated.
Surgical release
In a recent review of QS syndrome, it has been suggested that
it should be separated into a neurogenic and a vascular syn­
drome depending on the cause of compression.168 In the
instance of a vascular etiology, a ligation of the artery with or
without thrombolysis is advocated.
Since the neurogenic component with fibrous entrapment
of the axillary nerve is most commonly seen, a nerve release
in the QS is our treatment of choice (video 24.10
).17
In general anesthesia and with the patient in a lateral, or
three-quarters prone, position, a 10-cm dorsal skin incision is
made along the inferior border of the posterior deltoid.
Perform blunt dissection to the posterior deltoid and lift the
posterior edge. The TMi will be seen underneath. Locate and
release the axillary nerve branch innervating the TMi, then
follow this branch toward the axilla, as it will facilitate iden­
tification of the axillary nerve as it exits the QS. Release the
fibrous bands around the nerve but be cautious as the PCHA
is adjacent to the nerve. The patient is allowed to start imme­
diate motion without load; full load is allowed 4–8 weeks
postoperatively.
Musculocutaneous nerve compression
Anatomy and etiology
The musculocutaneous nerve arises from the lateral cord of
the brachial plexus. Shortly after its origin, it innervates the
coracobrachialis muscle. The musculocutaneous nerve then
pierces through a tight muscle fascia to innervate the biceps
brachii and brachialis muscle. Where the musculocutaneous
nerve pierces through the fascia between the coracobrachialis
and short head of the biceps is a potential site of nerve entrap­
ment.169,170 The terminal branch of the musculocutaneous
nerve is the lateral antebrachial cutaneous nerve, which
pierces through the distal fascial edge of the biceps, just
proximal of the elbow, providing sensation in the volar lateral
aspect of the forearm.
Isolated entrapment of the musculocutaneous nerve is a
relatively rare clinical entity. It has been reported as a compli­
cation following shoulder arthroscopy and proximal biceps
tenodesis,171,172 as well as a complication following heavy
weightlifting or strenuous overuse of the biceps.173,174
History and clinical examination
The patient usually presents with a complaint of arm weak­
ness, at times upper arm pain and paresthesias in the lateral
forearm.
Clinically, bilateral testing of biceps strength will reveal a
weakness on the affected side. SCT may be positive where the
musculocutaneous nerve passes between the coracobrachialis
and biceps brachii, about 8–10 cm distal to the shoulder joint.

546
SECTION III
CHAPTER 24 • Nerve entrapment syndromes
The suprascapular notch is found medial to the coracoid
process and bordered superiorly by the transverse scapular
ligament. Recent investigations into the anatomy of the trans­
verse scapular ligament has this as a primary source of nerve
compression.177 After innervating the supraspinatus muscle,
the nerve reaches the spinoglenoid notch at the lateral base of
the scapular spine. This is bordered by the spinoglenoid liga­
ment, and serves as a second common site of suprascapular
nerve compression.178,179
History and clinical examination
Suprascapular compression neuropathy should be suspected
in younger athletes, in particular overhead-throwing athletes,
or laborers who perform repetitive overhead activities. The
most common causes of suprascapular compression is trauma,
inflammation, pressure from ganglion cysts, or in relation to
rotator cuff injuries.180 Patients commonly present with dull
Pain upon compression at this site may elicit painful pares­
thesias into the forearm. EMG is helpful to determine possible
atrophy of the biceps muscles (Fig. 24.14). In the event of
normal biceps strength but paresthesias in the volar lateral
forearm, an isolated entrapment of the lateral antebrachial
cutaneous nerve should be suspected.175 If a biceps weakness
is found in combination with weakness of the pectoralis and
posterior deltoid, a more proximal brachial plexus entrap­
ment is probable.
Non-surgical treatment
The choice to treat conservatively is based on the degree of
biceps involvement. In early stages of entrapment, a conserva­
tive regime of NSAID and activity modifications are usually
sufficient.
Surgical release
Should atrophy of the biceps muscles be evident, clinically
and/or at EMG, surgical release of the musculocutaneous
nerve is indicated.
With the patient in a supine position, shoulder abducted,
an incision is made from about 2 cm distal to the coracoid
process and about 10 cm distally into the upper arm. The
distal edge of the pectoralis minor is elevated to reveal the
coracobrachialis muscle. At this level, the bifurcation of
the musculocutaneous nerve and lateral cord to the median
nerve can be identified. By following the musculocutaneous
nerve through the coracobrachialis, the tight fibrous bands
over the nerve and between the coracobrachialis and biceps
brachii can be released. Skin closure and postoperative man­
agement includes early range-of-motion exercises but refrain­
ing from elbow flexion with load during the first 4–8 weeks.
Suprascapular nerve compression
Anatomy and etiology
Although compression of the suprascapular nerve is consid­
ered a rare entity and a diagnosis of exclusion,176 this nerve
entrapment has received much attention in recent years as a
cause of shoulder pain in elite athletes. With the advent of
arthroscopic management of suprascapular nerve entrap­
ments, this rare nerve compression syndrome has become
among the most published nerve disorders in the past 3 years.
From its origins from the upper trunk of the brachial
plexus, the suprascapular nerve courses through the posterior
cervical triangle to reach the suprascapular notch (Fig. 24.15).
Fig. 24.14  Clinical image. Patient with right-sided biceps (arrows) atrophy due to
musculocutaneous nerve entrapment. (Reprinted with kind permission from Prof.
Carl-Göran Hagert, MD, PhD.)
Fig. 24.15  Anatomy of the dorsal scapular and suprascapular nerves. The dorsal
scapular nerve passes underneath the medial scalene muscle and more distally,
just underneath the proximal edge of the rhomboids, medial to the medial upper
corner of the scapula. Both muscles can compress the dorsal scapular nerve. The
suprascapular nerve passes under the transverse scapular ligament and through the
suprascapular notch. Similarly, the spinoglenoid notch is covered by the
spinoglenoid ligament. Both ligaments can compress the suprascapular nerve.
Levator scapulae
Rhomboid minor
Rhomboid
major
Teres major
Teres minor
Axillary nerve
Radial nerve
Suprascapular nerve
Dorsal scapular nerve
Supraspinatus
Infraspinatus
Deltoid

547
Other nerve compressions of the upper extremity
compression, to pass posteriorly beneath the levator scapulae,
which it innervates (see Fig. 24.15). After the levator, the nerve
passes beneath the proximal edge of the rhomboid major, just
medial to the medial upper corner of the scapula, at which
point the nerve is most commonly entrapped.191
Although a rare entrapment, compression of the dorsal
scapular nerve should be recognized as a cause of unilateral
interscapular pain and discomfort. Some authors believe the
presence of the dorsal scapular nerve entrapments to be
grossly underestimated.191,192 The most common cause of
entrapment is related to traction injuries of the neck, repetitive
overhead exertions, or direct pressure on the nerve.192–194
Recently, dorsal scapular nerve entrapment has been recog­
nized as a source of interscapular pain in spinal cord-injured
patients.162
History and clinical examination
The clinical presentation is one of gradual onset of dull pain
along the medial border of the scapula, at times radiating into
the posterior neck.195 Paresthesias are not a common finding
as the dorsal scapular nerve is primarily a motor nerve.
The most common clinical finding is a subtle lateralization
of the scapula, giving an appearance of mild scapular
winging.193,196 Winging may become more noticeable as the
arm is lowered from an elevated position.197 SCT may be posi­
tive just medial to the medial upper corner of the scapula,
where the nerve moves underneath the proximal edge of the
rhomboids. Pain is usually evident upon compression at this
level. It is important to test the strength in the infraspinatus
as concomitant scapular winging and infraspinatus weakness
may be a sign of C5-radiculopathy. Electrodiagnostics may be
of use, but the accuracy of these studies is limited to about
50%.192
Non-surgical treatment
As with the suprascapular nerve entrapment, patients with
dorsal scapular nerve involvement frequently have a history
of overhead overuse, and activity modifications, strengthen­
ing exercises of the rhomboids, and local steroid injections can
provide resolution of symptoms.
Surgical release
Before planning a release of the dorsal scapular nerve, it is
important to delineate if the primary point of compression is
at the middle scalene muscle or at the proximal edge of the
rhomboid muscles. In the former, a complete division of the
middle scalene muscle has been advised with good resolution
of symptoms. In our experience, the latter is more common
and will be described below.
The surgical release at the level of the medial scapular
corner is suitable for the wide-awake approach. With the
patient in a lateral position, the affected scapula upward, an
infiltration of 40 mL lidocaine–epinephrine is performed from
the cranial edge of the levator scapulae to 3–5 cm caudal of
the upper medial scapular corner. A straight incision is made
on the medial upper aspect of the scapula. Identify the levator
scapulae and lift the distal edge to identify the cranial border
of the rhomboid major muscle. Here, the dorsal scapular
nerve rides around the medial upper corner of the scapula,
about 1.5 cm from the medial edge,198 and beneath the tight
posterolateral shoulder pain and dysfunction. The diagnosis
can be delayed by months as treatment is erroneously directed
towards the cervical spine, rotator cuff, or glenohumeral joint.
The clinical examination should include muscle testing of
the infraspinatus, where weakness in external shoulder rota­
tion is evident. Supraspinatus strength may also be reduced
and is tested with the shoulder abducted to 60° as the patient
tries to resist and adduction motion by the examiner. Supra­
spinatus strength is, however, rather difficult to assess as
deltoid function often masks an underlying supraspinatus
weakness. In advanced cases, infra- and supraspinatus
atrophy may be evident. SCT may be positive over the supra­
scapular notch, and pain may be exacerbated by arm adduc­
tion and internal rotation that tighten the spinoglenoid
ligament.181
Other diagnostic tools
MRI studies are the primary imaging modality in suprascapu­
lar entrapments as they can reveal atrophy and fatty infiltra­
tion in the infraspinatus, as well as concomitant rotator cuff
injuries.182 Ultrasound may also be of use to examine for pos­
sible presence of ganglion cysts and changed, hypoechoic,
appearance in the suprascapular nerve.183 EMG studies may
also be obtained but carry an increased rate of false-negative
and -positive findings,184 and is not found to correlate to
outcomes of treatment.180
Non-surgical treatment
Most patients with suprascapular neuropathy have an under­
lying etiology of overuse, and activity modification, NSAIDs,
and strengthening exercise is adequate to relieve pain and
restore function in up to 80% of patients.185 If a ganglion cyst
is the cause of nerve entrapment, an ultrasound-guided
aspiration of the cyst may relieve the symptoms.180 In patients
with significant muscle atrophy or with a clear structural
compression, however, a non-surgical approach is unlikely to
be of benefit and may in fact lead to further dysfunction.186
Surgical release
Traditionally, the suprascapular notch has been decompressed
via a trapezius-splitting incision along the scapular spine.187
Although the arthroscopic approach carries with it a learning
curve,188 the advantages with smaller incisions and visualiza­
tion of the suprascapular nerve is now rendering arthroscopic
suprascapular nerve release the treatment of choice. Iannotti
and Ramsey have described the arthroscopic decompression
of the suprascapular nerve at the spinoglenoid notch.189 Bhatia
and colleagues have recently demonstrated an arthroscopic
approach to release both suprascapular and spinoglenoid
notch.190 Several long-term studies are showing favorable
results with arthroscopic release, both with regard to pain
relief, return to activities, and normalization of EMG.180
Dorsal scapular nerve compression
Anatomy and etiology
The dorsal scapular nerve originates from the C5 root, just
proximal to the upper cord of the brachial plexus. The nerve
pierces the middle scalene muscle, a potential point of

548
SECTION III
CHAPTER 24 • Nerve entrapment syndromes
various diagnostic algorithms and subsequent conservative
and/or surgical treatments.
The advent of higher-resolution MRIs (8-Tesla) and refined
ultrasound techniques will likely become increasingly impor­
tant diagnostic tools in nerve entrapment syndromes, with a
higher accuracy to find fatty muscle infiltrations due to dis­
creet denervations, changes in nerve echogenicity and the
presence of possible externally compressing factors.
The area of nerve compression syndromes offers the curious
researcher and clinician ample opportunity to investigate,
explore, and discover. As the 1906 Nobel Prize winner Dr.
Santiago Ramón y Cajal wrote, “Even granting that the genius
subjected to the test of critical inspection emerges free from
all error, we should consider that everything he has discov­
ered in a given domain is almost nothing in comparison with
what is left to be discovered.”
fascial edge of the rhomboids. The fascial edge is released and
the patient is asked to actively move the scapula to ensure
proper nerve gliding.
Future directions
Since electrodiagnostics are frequently inaccurate in diagnos­
ing entrapments other than carpal or cubital tunnel syndromes,
a combination of thorough clinical examination (manual
muscle testing, SCT, and provocative tests) must be the foun­
dation for a proper diagnosis and treatment. This chapter on
nerve compressions has focused on recognizing the impor­
tance of clinical examination skills in patients with upper
extremity pain and/or dysfunctions. One future challenge lies
in constructing clinical studies reporting on the efficacy of
4. Hagert E. Clinical diagnosis and wide-awake surgical treatment of
proximal median nerve entrapment at the elbow: a prospective
study. Hand (N Y). 2013;8:41–46. This article provides a detailed review
of the lacertus syndrome and outcomes following minimal nerve release
in 44 patients.
5. Sunderland S. The intraneural topography of the radial, median
and ulnar nerves. Brain. 1945;68:243–299. The original work
highlighting the nerve anatomy and internal topography, which is
essential in understanding patterns of muscle weakness in patients with
nerve entrapments.
6. Upton AR, McComas AJ. The double crush in nerve entrapment
syndromes. Lancet. 1973;2:359–362.
7. Mackinnon SE. Double and multiple “crush” syndromes. Double
and multiple entrapment neuropathies. Hand Clin. 1992;8:369–390.
A comprehensive review of double-crush syndrome and the use of careful
clinical examination to elicit symptoms in patients.
18. Tang DT, Barbour JR, Davidge KM, et al. Nerve entrapment:
update. Plast Reconstr Surg. 2015;135:199e–215e. The most recent
review of nerve entrapment pathophysiology in relation to clinical
concepts.
21. Tapadia M, Mozaffar T, Gupta R. Compressive neuropathies of the
upper extremity: update on pathophysiology, classification, and
electrodiagnostic findings. J Hand Surg Am. 2010;35:668–677. This
article summarizes the current developments in the basic science of
chronic nerve compression and provides a review of the double-crush
phenomenon as well as electrodiagnostic tests.
23. Hagert CG, Hagert E. Manual muscle testing – a clinical
examination technique for diagnosing focal neuropathies in the
upper extremity. In: Slutsky DJ, ed. Upper Extremity Nerve Repair
– Tips and Techniques: A Master Skills Publication. Rosemont, IL: The
American Society for Surgery of the Hand; 2008:451–466. This book
chapter summarizes the use of the manual muscle testing technique to
diagnose upper extremity nerve entrapments.
34. Bickel KD. Carpal tunnel syndrome. J Hand Surg Am. 2010;35:147–
152. This review examines the ongoing challenges in developing clinical
criteria for the diagnosis of carpal tunnel syndrome as well as reviewing
current treatment approaches.
69. Lalonde D, Bell M, Benoit P, et al. A multicenter prospective study
of 3,110 consecutive cases of elective epinephrine use in the fingers
and hand: the Dalhousie Project clinical phase. J Hand Surg Am.
2005;30:1061–1067. This article firmly established the safe use of
epinephrine in hand surgery, launching the concept of wide-awake hand
surgery in clinical practice.
70. Leblanc MR, Lalonde J, Lalonde DH. A detailed cost and efficiency
analysis of performing carpal tunnel surgery in the main operating
room versus the ambulatory setting in Canada. Hand (N Y).
2007;2:173–178. The authors examine the benefits of the wide-awake
approach to carpal tunnel release compared to carpal tunnel surgery
performed in the main operating suite under general anesthesia in terms
of cost and overall efficiency. The wide-awake approach to carpal tunnel
release allows the hand surgeon to improve productivity without
compromising patient safety or outcomes.
198. Tubbs RS, Goodrich D, Watanabe K, et al. Anatomic landmarks for
selected nerves of the head, neck, and upper and lower limbs. In:
Tubbs RS, ed. Nerves and Nerve Injuries. New York, NY: Elsevier;
2015:575–588. This chapter provides a comprehensive and illustrative
review of peripheral nerve anatomy in relation to surface landmarks, a
practical guide to surgeons treating nerve entrapment syndromes.
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137. Dellon AL. Partial dorsal wrist denervation: resection of the distal
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CHAPTER 24 • Nerve entrapment syndromes
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143. Lundborg G. Peripheral Nerve Injury and Repair. New York, NY:
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144. Sarhadi NS, Korday SN, Bainbridge LC. Radial tunnel syndrome:
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145. Eaton CJ, Lister GD. Radial nerve compression. Hand Clin.
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146. Hashizume H, Nishida K, Nanba Y, et al. Non-traumatic paralysis
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147. Simon Perez C, Garcia Medrano B, Rodriguez Mateos JI, et al.
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148. Huisstede B, Miedema HS, van Opstal T, et al. Interventions for
treating the radial tunnel syndrome: a systematic review of
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149. Jalovaara P, Lindholm RV. Decompression of the posterior
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150. Artico M, Telera S, Tiengo C, et al. Surgical anatomy of the radial
nerve at the elbow. Surg Radiol Anat. 2009;31:101–106.
151. Adolfsson LE, Nettelblad H. Radial nerve entrapment in the upper
arm as a cause of lateral arm pain: a report of four cases. Scand J
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152. Streib E. Upper arm radial nerve palsy after muscular effort:
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153. Ng AB, Borhan J, Ashton HR, et al. Radial nerve palsy in an elite
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154. Sebastian D. Triangular interval syndrome: a differential diagnosis
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155. Robinson LR. Role of neurophysiologic evaluation in diagnosis.
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156. Ishima T, Usui M, Satoh E, et al. Quadrilateral space syndrome
caused by a ganglion. J Shoulder Elbow Surg. 1998;7:80–82.
157. Francel TJ, Dellon AL, Campbell JN. Quadrilateral space
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158. Amin MF, Berst M, el Khoury GY. An unusual cause of the
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159. McClelland D, Paxinos A. The anatomy of the quadrilateral space
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160. McAdams TR, Dillingham MF. Surgical decompression of the
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161. Monteleone G, Gismant M, Stevanato G, et al. Silent deltoid
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162. Curtin C, Hagert CG, Hultling C, et al. Nerve entrapment as a cause
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163. Cahill BR, Palmer RE. Quadrilateral space syndrome. J Hand Surg
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164. Bredella MA, Tirman PF, Fritz RC, et al. Denervation syndromes of
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165. Linker CS, Helms CA, Fritz RC. Quadrilateral space syndrome:
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166. Cothran RL Jr, Helms C. Quadrilateral space syndrome: incidence
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167. Chen H, Narvaez VR. Ultrasound-guided quadrilateral space
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168. Brown SA, Doolittle DA, Bohanon CJ, et al. Quadrilateral space
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172. Ma H, Van Heest A, Glisson C, et al. Musculocutaneous nerve
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173. Swain R. Musculocutaneous nerve entrapment: a case report. Clin
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177. Podgorski M, Topol M, Sibinski M, et al. New parameters
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practical guide to surgeons treating nerve entrapment syndromes.

SECTION IV • Congenital Disorders
25 
Congenital hand I: Embryology,
classification, and principles
Michael Tonkin and Kerby Oberg
SYNOPSIS
■ Consistency of terminology is necessary for optimal communication.
■ Limb outgrowth and patterning are controlled by specific signaling
centers within the developing limb bud via the activation and
interaction of molecular messengers.
■ Anomalies of limb development result from:
• spontaneous mutation of genetic material
• inheritance of abnormal genes
• subtle or gross insult to the limb bud.
■ The anomaly may be isolated or syndromic.
■ The International Federation of Societies for Surgery of the Hand
(IFSSH) has recommended that the Swanson classification (previously
approved by the IFSSH) be replaced by the Oberg, Manske, Tonkin
(OMT) classification, which separates malformations from
deformations and dysplasias. Malformations are further sub-divided
according to the axis of limb development that is primarily involved
and whether the insult affects the whole of the upper limb or the hand
plate only. This classification incorporates our increasing understanding
of the molecular basis of limb development.
■ Assessment and treatment are specific for each child and family but
are based on a detailed understanding of the processes of limb
development, the psychological and physical effects of limb anomalies,
and simple surgical principles.
Introduction
Limb development
The upper limb bud appears during the fourth week of devel­
opment as an outgrowth on the sides of the embryo. Cells of
the somatic lateral plate mesoderm form the skeletal frame­
work of the limb, while mesoderm from the somite migrates
in to form the muscular component and contributes to the
limb’s vascular network. Over the next 4 weeks, growth
and differentiation transform the limb bud into an elegant
asymmetric organ that is one of the defining features of the
human species. The limb bud growth and differentiation are
under the control of signaling centers, specialized areas within
the limb that dictate, in concert, the appropriate sequential
events of development.
The establishment of signaling centers and their subsequent
behavior are under genetic control. The genes and the mor­
phogens (proteins) they encode control the process of limb
growth and differentiation and act as messengers between
signaling centers and developing cells.
As knowledge of the process of limb development becomes
more sophisticated, an understanding of the causation of limb
anomalies becomes clearer.
Genetic mutations can disrupt the molecular function of a
number of proteins orchestrating limb development, includ­
ing secreted proteins (ligands), ligand receptors, and tran­
scription factors. The mutation may be inherited or may arise
spontaneously. Environmental factors, such as thalidomide,
which resulted in an epidemic of limb malformations during
the 1960s, radiation, nutritional defects, and infections may
affect the molecular pathways of development or be respon­
sible for a more gross insult resulting in tissue hemorrhage
and/or necrosis. For example, if such direct damage occurs
obliterating the apical ectodermal ridge (AER), an important
signaling center that directs limb outgrowth, transverse trun­
cation will result.
Classification
Congenital anomalies in the hand demand a reproducible and
consistent terminology, a universal language that allows dis­
cussion of complex clinical entities, indications for treatment,
and comparisons of results.
Swanson’s classification was adopted by the IFSSH in 1976
as the standard system by which congenital hand anomalies
were described.1 It is derived from ideas existing in the
1960s regarding limb embryology and is largely based on
morphological appearance. Knight and Kay2 have presented
an extended version, attempting to incorporate a list of all
  Access video content for this chapter online at expertconsult.com

550
SECTION IV
CHAPTER 25 • Congenital hand I: Embryology, classification, and principles
congenital anomalies. Regrettably, this classification is intrin­
sically unsuited to alterations based on causation and etiology
at a molecular level.
In 2014, the IFSSH Scientific Committee for Congenital
Conditions recommended that the Oberg, Manske, Tonkin
(OMT) classification replace that of Swanson.3 This system
utilizes dysmorphological terminology, separating congenital
upper limb anomalies into malformations, deformations, and
dysplasias. Malformations, the majority of encountered anoma­
lies, are further sub-divided according to which axis of forma­
tion and differentiation is primarily affected and whether the
consequence affects primarily the hand plate alone or the
whole upper limb. It is probable that the causation of some
anomalies will confound our attempts to assign a specific site
in the molecular pathway and/or the anatomical site in the
limb bud and the time at which the aberration occurs.
However, the OMT system would appear to be a more logical
approach to classification.
Assessment and principles of treatment
It is clear that the terminology applied to congenital anomalies
should reflect a language common to, and understood by, the
geneticist, the anatomist, the pathologist, and the surgeon. For
this reason, these authors have chosen to link the terminology
of embryology of the limb bud at the molecular level, the
terminology of dysmorphology, and the terminology of clas­
sification. This consistency would appear to provide less
controversy in a rapidly changing field of knowledge. Fur­
thermore, such an approach is of benefit when attempting to
explain to parents how the limb normally forms and how any
particular anomaly may occur. This process plays a vital role
in the assessment of any specific anomaly and leads to a
sensible plan of management.
Limb development (embryology)
Overview of upper limb morphogenesis
Around day 26 (4 weeks) after fertilization (Carnegie stage
12), the upper limb bud appears as an oblong ventrolateral
bulge on the body wall between somites 9–12 (C5–8) (Fig.
25.1).4 The emerging limb bud is composed of somatic lateral
plate mesoderm covered by ectoderm. Subsequent limb bud
growth and differentiation are described in terms of three
coordinate axes: proximodistal, dorsoventral (dorsovolar),
and anteroposterior (or radioulnar) (Fig. 25.2), each controlled
by distinctive regions – signaling centers.
The ectoderm overlying the distal edge of the limb bud at
the dorsovolar boundary thickens and forms a distinct ridge
of stratified ectoderm, the AER.5 The thickened AER is critical
for proximodistal outgrowth and also adds mechanical rigid­
ity to the distal rim of the limb bud, flattening it along the
dorsovolar axis. Excision of the AER in chicken embryo limb
buds prevents further proximodistal outgrowth and results in
limb truncation.6 Underlying the AER, the distal undifferenti­
ated mesoderm has been termed the progress zone (PZ). Cells
in the PZ ultimately differentiate into specific cell types and
are directed to specific positions within the limb.
The dorsal ectoderm is a critical signaling center for direct­
ing formation of dorsal and volar characteristics of the limb.
Excision and rotation of dorsal ectoderm cause the formation
of dorsal structures on the limb ventral surface.7 Another
collection of mesodermal cells at the distal ulnar (posterior)
margin is called the zone of polarizing activity (ZPA).
Although not morphologically distinct, these cells direct
radioulnar patterning and coordinate asymmetric limb pat­
terning with the other signaling centers during development.
Removal of the ZPA in animal models leads to loss of the ulna
and the ulnar digits.8 Conversely, transplantation of these cells
to the anterior (radial) aspect of limb buds of chicken embryos
will result in formation of a mirrored complement of ulnar
digits radially.9
Over the next week, the limb bud expands and elongates,
particularly along the proximodistal axis (Table 25.1). By day
33 of development (Carnegie stage 14), differential growth
and programmed cell death transform the distal portion into
a paddle-shaped hand plate. There is also progressive meso­
dermal condensation along the proximodistal axis, forming a
tripartite skeleton composed of a proximal section, the stylo­
pod (humerus), a middle section, the zeugopod (radius and
ulna), and a distal section, the autopod (hand). The joints
become fully evident about day 51 (Carnegie stage 20) when
the elbow and wrist joints flex, and by day 56 (end of the
eighth week, Carnegie stage 23), the major morphologic fea­
tures of the limb are complete (see Fig. 25.1).
The molecular control of limb outgrowth
and patterning
During early embryonic development, Hox transcription
factors set up a segmental body plan along the cranial–caudal
axis.10 By the fourth week of development the presumptive
upper limb fields are established, triggering the expression of
Tbx5, which initiates limb formation and determines forelimb
identity.11 Tbx5 upregulates Fgf10 in the limb mesoderm and
Wnt3 in the distal ectoderm.12,13 Mesodermal Fgf10, in con­
junction with ectodermal Wnt3, TP63, Dlx5/6, and radical
fringe (R-fng), transform the distal ectodermal at the dorso­
volar boundary into the thickened AER.14–17 Formation of the
AER initiates the expression of AER-related Fgf proteins
(including Fgf2/4/8/9/17),18–19 which, in turn, act on the
mesoderm just underneath the AER to sustain Wnts and Fgf10
expression in the PZ. This reciprocal loop of ectodermal and
mesodermal Fgf/Wnt proteins promotes progressive proxi­
modistal outgrowth20,21 (Fig. 25.3). In the absence of Wnt3 or
Table 25.1  Timing of hand formation
Time after fertilization
Hand development
27 days
Development of arm bud
28–30 days
Further development of arm bud
34–36 days
Elongation of arm bud
34–38 days
Formation of hand paddle
38–40 days
Early separation of digits
44–46 days
Digits separated
Week 9–10
Formation of fingernails begins
(Reproduced from Gupta A, Kay SPJ, Scheker LR (eds). The Growing Hand:
Diagnosis and Management of the Upper Extremity in Children. London: CV
Mosby; 2000:25.)

551
Limb development (embryology)
Fig. 25.1  Upper limb and hand development. (A) Human embryo at Carnegie stage 13 (about 28 days of development), showing early limb buds. (B) Close-up dorsal
view of the arm bud. The anterior or radial (Rad) aspect is cranial and the posterior or ulnar (Uln) aspect is caudal. (C) Cross-section through an upper limb bud at 32 days
of development (Carnegie stage 14), showing dorsal (Do)–ventral (Ve) limb bud flattening and the thickened apical ectodermal ridge at the distal tip of the limb bud (that
runs along the dorsal–ventral border from anterior to posterior). Pr, proximal; Di, distal. (D) The hand plate at 41 days of development (Carnegie stage 17). The scalloped
edge conforms to the condensing digital mesenchyme. (E) Limb at 46 days of development (Carnegie stage 19). Separate fingers are evident. The proximal limb skeleton is
well developed and ossification has begun in the humerus and shoulder girdle. (F) The embryo at 49 days of development (Carnegie stage 20), showing ossification
centers in the upper limb, lower limb, and face. Note that upper limb development is more advanced than lower limb development. (G) Upper limbs at week 8 (Carnegie
stage 22). The fingers are completely separate and ossification centers have developed in the forearm, i.e., radius and ulna. (H) The upper limb at week 9 (Carnegie stage
23). Metacarpal and distal phalangeal ossification has begun. (I) The upper limb at week 11. Ossification in proximal and middle phalanges is now evident in addition to
distal phalanges and metacarpals. (J) The hand at week 12, showing developing nail fields (nails become visible during week 16). (Portions redrawn from England MA. A
Colour Atlas of Life Before Birth. London: Year Book Medical Publications; 1983.)
Clavicle
Maxilla
Mandible
Clavicle
Humerus
Scapula
Femur
Humerus
Scapula
Condensed
mesoderm
Ossification
sites:
Ossification
centers:
Medial rotation
of arms, formation
of elbow
Hands meet
and cross
Lateral view
Day 41
Day 46
Day 49
(Week 7)
Week 8
Week 9
Week 11
Week 12
Ulna
Radius
Ve
Di
Do
Pr
Distal
phalanges
Proximal
and middle
phalanges
Metacarpals
Nail fields
Maxillary
process
Eye
Leg bud
Heart
Arm bud
3rd
pharyngeal
arch
Hyoid arch
Ear hillocks
Cranial
Rad
Uln
Apical
ectodermal
ridge (AER)
Heart
Mandibular
process
Somites
Day 28
Day 28
Day 32
A
B
C
D
F
E
G
H
I
J
Fgf10, limbs fail to develop and tetra-amelia results.22,23 Appli­
cation of Fgfs to the distal chick limb bud after AER removal
will return proximodistal limb outgrowth.19 Within the PZ,
mesodermal cells persist in an undifferentiated or receptive
state, allowing the signaling centers to direct their fates.
The ZPA in the posterior (ulnar) limb mesoderm secretes
a potent morphogen, sonic hedgehog (Shh), that regulates
radioulnar patterning24 (see Fig. 25.3). Shh induces posterior
(ulnar) proliferation of the limb bud expanding its width.25,26
Moreover, Shh posteriorizes (ulnarizes) the developing

552
SECTION IV
CHAPTER 25 • Congenital hand I: Embryology, classification, and principles
Fig. 25.2  Limb bud coordinate axes and signaling centers:
(A) The forelimb (boxed region) of a Carnegie stage 13 embryo
depicting the three coordinate axes – each with its own
signaling center: the apical ectodermal ridge (AER) coordinating
proximodistal (Pr–Di) outgrowth and differentiation; dorsovolar
(Do–Vo) asymmetry is regulated by dorsal ectoderm; radioulnar
asymmetry is controlled by the zone of polarizing activity (ZPA).
Within the progress zone (PZ) the fate of mesodermal cells is
determined by these signaling centers. The axes and signaling
centers are shown in three different orientations: (B) dorsal
view, (C) lateral, end-on view, and (D) axial cross-section.
(Modified from Oberg KC, Greer LF, Naruse T. Embryology of the
upper limb: the molecular orchestration of morphogenesis.
Handchir Mikrochir Plast Chir. 2004;36:98–107.)
Dorsal ectoderm
Do
Pr
Vo
Di
PZ
AER
AER
AER
Do
Rad
Vo
ZPA
Uln
Pr
Rad
PZ
ZPA
Uln
Di
PZ
Somites
Forelimb
Carnegie Stage 13 Embryo
Eye
Heart
A
B
C
D
Fig. 25.3  Morphologic impact of signaling centers.
Upper panel: Role of apical ectodermal ridge (AER)-
related Fgfs (orange) on skeletal outgrowth (humerus,
blue; radius and ulna, green; hand, magenta). Middle
panel: Role of Shh secretion from the zone of polarizing
activity (ZPA): influence on the forearm and digits
(depicted in purple). Lower left panel: Role of Wnt7a
(medium green) and Lmx1b (light green), from the dorsal
ectoderm and mesoderm respectively, in tendon and
ligament formation in a digit. Do, dorsal; Vo, volar; Pr,
proximal; Di, distal; PZ, progress zone. Lower right panel:
Illustration depicting communication between signaling
centers – reciprocal Shh–Fgf loop (black bidirectional
arrow). Wnt7a influence on Shh expression (black
unidirectional arrow). Rad, Radial; Uln, ulnar.
Stage 13
Stage 15
Fgfs
(AER)
AER
AER
Vo
ZPA
Uln
Shh
(ZPA)
Wnt7a
Lmx1b
Do
Pr
Vo
Di
Pr
Rad
PZ
PZ
ZPA
Uln
Di
PZ
AER
Stage 17
Stage 13
Stage 17
Stage 21
Proximodistal asymmetry
Radioulnar asymmetry
Dorsovolar asymmetry
Fgfs
(AER)
Rad

553
Limb development (embryology)
digits. First, Bmps induce programmed cell death or apoptosis
via discrete interdigital signaling centers, in part by repress­
ing Fgf expression in the overlying AER.41–43 In addition, Bmps
play a role in completing digital identity via the phalanx-
forming region, a region overlying the distal digital anlagen
that regulates Sox9 expression and chondrogenesis.44
Applying a Bmp-laden bead or transplanting Bmp-expressing
interdigital tissue from the third interdigital space to the
second transforms the second digit into a third digit.41 The
phalanx-forming region also maintains digit-associated Fgf
expression in the overlying AER for continued digital out­
growth.44 With regression of the phalanx-forming region and
loss of overlying Fgf, the terminal phalanges form at the distal
tip of each digit, invoking a unique mechanism of ossification
that includes membranous ossification in addition to anlagen
formation.45,46 The terminal phalanx is also demarcated by
persistent expression of Msx1 in the mesoderm, and Sp8 in
the ectoderm.47
The development/differentiation of
specific tissues
Limb bud formation and the progressive morphologic changes
evident externally are accompanied by differentiation of
various tissues internally that are regulated by the coordinate
signaling centers described above. Differentiation of these
tissues is coincident, but will be discussed separately to add
clarity and to relate timing of formation to tissue-specific
malformations.
Limb vasculature
As the limb bud grows, nutrients and oxygen are needed to
maintain rapid cell proliferation and the secretory activity of
forearm and defines the identity of the ulnar four digits.
In a naturally occurring chicken mutant, limb-specific Shh
expression is lacking and the upper limbs develop without
ulnas and without digits.27 Application of exogenous Shh to
the posterior (ulnar) aspect of the limb bud can fully recover
normal limb morphology. Furthermore, application of Shh to
the anterior margin produces mirrored duplication of ulnar
digits radially.24
The AER and the ZPA are also closely linked by a reciprocal
feedback loop that maintains Shh expression at the distal
posterior (ulnar) border of the limb bud adjacent to the AER
during progressive outgrowth.28–30 Removal of the AER causes
regression of Shh expression and ablation of the ZPA induces
a loss of Fgf signaling.29 Secretion of Wnt7a from the dorsal
ectoderm induces the homeodomain transcription factor
Lmx1b in the underlying mesoderm and asymmetrically
dorsalizes the developing limb31,32 (see Fig. 25.3). Wnt7a also
contributes to the maintenance of Shh secretion from the
ZPA,33 linking the dorsovolar and radioulnar axes. Removal
of dorsal ectoderm reduces Shh expression and disrupts
posterior (ulnar) patterning.34 Thus, Shh plays a pivotal role
during limb development linking dorsovolar, proximodistal,
and radioulnar axes during outgrowth.34
Around the end of the fifth week of development, the hand
plate becomes visible. Current data suggest that digit number
is established by an intrinsic Turing-type pattern generator
within the hand plate using reciprocal activator (Bmps) and
inhibitor (Wnt) interactions to define the alternating digit
and interdigit pattern35,36 (Fig. 25.4). Interplay between Hox
transcription factors (particularly Hoxd9–13 and Hoxa9–13)
and the Shh/Gli3 pathway subsequently establishes digit
morphology37–40 (Fig. 25.5). Shh also induces an ulnar to radial
(posterior to anterior) gradient that appears to involve Bmps
in at least two roles in the formation and differentiation of
Fig. 25.4  Determining the number of digits. An intrinsic
Turing-like patterning mechanism for digit formation has
been proposed using computational modeling and
experimental evidence.35,36 In the upper left-hand corner is
a diagram of a diffusion-driven instability model proposed
by Turing. In the limb, evidence suggests that Bmp (red) is
the activator while Wnt (yellow) is the inhibitor of
diffusion-driven instability. Both factors are regulating the
expression of Sox9 (blue), the precursor of cartilage
formation. Fgfs and the Hox/Gli pathway modulate the
relative influence of the activator and inhibitor. Fgfs from
the apical ectodermal ridge (AER) determine digit length
and in concert with the distal Hox/Gli pathway limit digit
number (green bar/gradient on the right). In addition, Fmn1
restricts Bmp expression and mutations in Fmn1 cause
increased levels of Bmp with disruption of normal forearm
(radioulnar synostosis) and hand (oligosyndactyly)
patterning.143,144 The bottom of the illustration has a series
of hand plates (note hand plate development remains static
in this illustration to aid in illustrating features of the
model) that show the progression from fluctuating
activator-inhibitor interactions (noise) to a stabilized 5-digit
pattern. On the right, progressive loss of digit suppressing
HOX/GLI transcription factors (green bar) causes an
increase in the number of digits patterned by the
autonomous patterning mechanism. (Modified from Oberg
KC, Ros MA, Goldfarb CA. New Insights on upper limb
development: digitizing the hand. IFSSH Ezine.
2014;4(2):16–22.)
Fmn1
Fgf
Hox/Gli
Activator
(Bmp)
Digital pattern
Hox/Gli
Inhibitor
(Wnt)
Sox9
Cartilage
formation
Activator (Bmp)
Inhibitor (Wnt)
Stabilization of activator–inhibitor interaction
Digit anlagen (Sox9)

554
SECTION IV
CHAPTER 25 • Congenital hand I: Embryology, classification, and principles
into the posterior cardinal system.50 In addition to vasculogen­
esis, angiogenesis, i.e., vessel sprouting from a preformed
vessel, also contributes to the definitive architecture of the
limb vasculature.
Construction of the vascular pattern is under the direction
of the coordinate signaling centers and involves the regulation
of specific VEGF family members and VEGFR3 receptors.52–54
The final vascular pattern progresses from proximal to distal
(Fig. 25.6) – with formation of the axillary artery by stage 17
and the brachial and major forelimb branches by stage 19. The
median artery is prominent in the forearm.55 Distally the capil­
lary plexus persists. Ulnar differentiation precedes radial
differentiation and is evident distally by the radial artery
merging with an extensive primitive capillary plexus radially,
while the ulnar side of the axis is already forming the palmar
arch which communicates with the ulnar associated capillary
plexus.56 The median and interosseous arteries decrease in
size. The median artery degenerates, providing blood supply
to the median nerve only.55
the signaling centers. Induction of a primitive vascular system
in the limb begins with transformation of mesoderm into
angioblasts, cells that express the basic helix–loop–helix
transcription factor Tal-1 and the vascular endothelial growth
factor (VEGF) receptor Flk1.48 A dense meshwork of primitive
vascular channels forms de novo from angioblasts in the limb
mesoderm.49,50 Angioblasts formed in nearby somites also
migrate into the limb bud and contribute to the formation
of new limb vessels through continued vasculogenesis.51 As
angioblasts aggregate, differentiate into endothelium, and
form primitive vascular tubes, new vascular markers emerge.
Flk1 persists to allow further remodeling by VEGF, Tal-1
diminishes and VE-cadherin, a cell–cell adhesion molecule, is
upregulated.
The primitive vascular network undergoes significant
remodeling as the limb develops. By stage 13, the vascular
channels coalesce proximally to form a central artery (subcla­
vian) that connects to the dorsal aorta via the seventh inter­
segmental artery52 and two peripheral veins form that drain
Fig. 25.5  Hand plate development. After the digit number has been established by intrinsic Turing patterning, the Shh pathway (with Gli3 repressor counter gradients)
defines dependent/independent domains (boundaries indicated by dashed line) that determine digit morphologies. Interdigital mesoderm (ID1–ID5) regulates regression of
the overlying apical ectodermal ridge (AER; orange) and digit morphologies of the adjacent anterior condensing digit via the phalanx-forming region (PFR; magenta)
capping the distal tip of each anlagen. The PFR, in concert with the AER, determines phalanx size, length and joint position. The interdigital tissue subsequently undergoes
Bmp-mediated programmed cell death (speckled regions). As the AER overlying the digit regresses, the distal or ungual phalanx forms and is demarcated by expression of
mesodermal Msx1 (blue) and ectodermal Sp8 (green). (Image adapted from Oberg KC, Feestra JM, Manske PR, et al. Developmental biology and classification of congenital
anomalies of the hand and upper extremity. J Hand Surg [Am]. 2010;35:2066–2076.)
Digit specification
Anlagen formation
Digit differentiation
Digit tip formation
Gli3R
Shh
ShShh dependant/Independant boundary
Phalanx-forming region
Programmed cell death
Msx1
Sp8
ID5
ID4
ID3
ID2
ID1
ID5
ID4
ID3
ID2
ID1
Fig. 25.6  Vasculogenesis of the developing upper
limb. Progressive vascular remodeling from Carnegie
stage 13 through 21, showing: subclavian artery (S),
axillary (A), brachial (B), median (M), radial (R), ulnar
(U), interosseous (i), palmar arches (PA), and digital
(D) arteries (red). Note the primitive vascular plexuses
persist distally on the radial aspect at stage 19. The
veins have also remodeled during this period, from a
distal sinus and anterior (radial) and posterior (ulnar)
marginal veins, into the distinctive veins of the limb
(illustrated in blue).
S
S
A
B
R
D
PA
I
U
S
A
A
R
B
U M
I
Stage 13
Stage 15
Stage 17
Stage 19
Stage 21

555
Limb development (embryology)
Fig. 25.7  Skeletogenesis of the developing upper limb. By
Carnegie stage 17 there is partial rotation of the humerus (Hu,
blue) at the shoulder and the elbow joint is starting to form.
Radius (Rad, green); ulna (Uln, green); hand, magenta.
Uln
Rad
Hu
Stage 13
Stage 19
Stage 15
Stage 17
Stage 21
The vascular network must include arteries, capillaries,
and veins. The diameter of each is dictated by blood flow,
blood pressure, shear stress, and the accumulation of vascular
smooth muscle around the vessel.49 Formation of vascular
smooth muscle around limb arteries lags behind vessel forma­
tion by about 2 days. It is unclear whether these muscle cells
are derived from the endothelial cells or are condensations of
the surrounding mesoderm. Furthermore, the mechanism
underlying differential smooth-muscle accumulation in arter­
ies and veins is unknown. Arteries are also differentiated from
veins by the expression of Ephrin B2, a membrane-bound
ligand, while the Eph-B4 receptor highlights veins. Presump­
tive capillaries will be negative to both Ephrin B2 and the
Eph-B4 receptor.
By stage 21, the major vessel architecture is complete. The
majority of vascular anomalies arise between stages 17 and
21, i.e., between days 41 and 52 or largely within the seventh
and early eighth week of development. Lymphatics follow a
similar course, albeit less well delineated, and are also com­
posed of angioblasts that migrate into the limb from somitic
mesoderm.51 A defining molecular difference in lymphatic
vessels is the coexpression of PROX-1 and LYVF-1.57
Skeletogenesis
Under the influence of the limb signaling centers, Sox9, a
high-mobility group transcription factor, is upregulated in a
targeted population of limb mesoderm.58 Sox9 transforms
these cells into chondrogenic precursors and induces conden­
sation, the first step in limb skeletogenesis.59,60 Chondrogenesis
occurs in a proximal to distal progression (Fig. 25.7). The
expression of Sox5 and Sox6 is required for further differentia­
tion of chondrogenic precursors into chondrocytes to form
cartilage anlagen.61
At precise locations within the forming skeletal anlagen,
synovial joints form. Hoxa transcription factors (Hoxa9–13)
exhibit expression patterns along the proximodistal axis that
correlate with skeletal segmentation.61 In addition, several
molecules are known to participate in the process of joint
formation, including Wnt14 and Gdf5. The first morphologic
evidence of joint formation is the compact cellular condensa­
tion called the interzone that expresses Wnt14.62 In addition,
Gdf5 is induced in the proximal portion of the interzone,
covering the distal end of the proximal anlagen.63,64 The central
region of the interzone begins to expand, accumulates hyal­
uronan, and becomes hypocellular in a process termed cavita­
tion.65,66 The two cellular regions of the interzone begin to
differentiate into the opposing articular cartilage surfaces.
Patterning signals and movement work in concert to shape
the joint into its definitive morphology64 (Fig. 25.8). Mesoderm
surrounding the developing joint condenses to form the joint
capsule.67
Endochondral ossification converts the cartilage anlagen
into the skeletal framework of the growing limb. This process
is under precise regulation and involves Runx2, Twist1, Fgfs,
Indian hedgehog (Ihh), and vascular endothelial growth
factors (Vegfs).60 Chondrocytes are induced to proliferate,
undergo hypertrophy, and then die, leaving an extracellular
cartilage matrix. This matrix is subsequently invaded by
blood vessels, osteoclasts, and differentiating osteoblasts.
Osteoblast differentiation is also under the control of Runx2
and Osterix (Osx), a bone-specific transcription factor.68 Ossi­
fication begins within the diaphysis of anlagen at the primary
ossification center during early fetal development. Subse­
quently, vascular invasion of the proximal epiphysis occurs,
followed by the distal epiphysis forming secondary ossifica­
tion centers later in development. Each metacarpal and digital
phalanx has two ossification centers, a primary center within
the diaphysis and a single secondary center that develops
postnatally.
Bony malformations are most likely to involve the disrup­
tion of Sox9 and the progressive proximal to distal anlagen
formation, i.e., radiohumeral synostosis would occur earlier
in development than polydactyly or syndactyly.
Myogenesis
Muscular development of the upper limb is a coordinated
effort between segment-specific tendon primordium, migrat­
ing myocytes, and migrating motor neurons.69,70 There are

556
SECTION IV
CHAPTER 25 • Congenital hand I: Embryology, classification, and principles
emanating from the lateral plate mesoderm and then later
from other sites, including the PZ. Scatter factor acts as a
chemoattractant to promote myocyte precursor migration. A
population of the myocyte precursors further differentiates
into limb-specific precursors, demarcated by Lbx1 expression73
(Fig. 25.9).
During embryonic myogenesis, limb-specific myocytes
migrate into the proximal limb bud, initially as dorsal and
ventral masses (Fig. 25.9). Continued migration, however, is
not haphazard; rather, myocyte precursors are directed into
muscle anlagen by the tendon primordium, e.g., the ventral
mass migrates into the biceps and brachialis under the direc­
tion of the PTP (Fig. 25.10, Carnegie stage 15). With continued
proliferation and differentiation, the myocytes upregulate
MyoD and Myogenin, declaring their commitment as myo­
cytes. These myocytes will then coalesce to form fibers and
three phases to myogenesis.71 Embryonic myogenesis estab­
lishes the primary myotubes and the basic muscle layout.
Later, a second wave of myogenesis occurs with secondary
myofibers surrounding primary myofibers and contributing
to the bulk of the muscle mass present at birth. Finally, satel­
lite cells that take up residence in the basal lamina surround­
ing myofibers will contribute to postnatal growth and muscle
regeneration.72
During early limb bud formation, limb mesoderm con­
denses to form the proximal tendon primordium (PTP),
establishing a target and an initial scaffold for migration of
myocytes.69 Myocyte precursors of the limb arise from the
dorsolateral aspect of associated somites (the dermomyo­
tome subdivision) and express the Pax3 transcription factor.
Muscle precursors for the limb and body wall express c-Met,
a surface receptor that is modulated by scatter factor initially
Fig. 25.9  Early neuromuscular development in the upper limb. (A) Dorsovolar view of presumptive myocyte migration into the limb from the lateral aspect of the
dermomyotome (DM) – molecular markers listed in gray box. (B) Motor and sensory projection of processes into the developing limb. SK, Sclerotome; SF, scatter factor;
Do, dorsal; Vo, volar; Pr, proximal; Di, distal; Cut, cutaneous; Proprio, proprioception.
DM
Do
SK
SF
Di
Di
Pax3, c-Met
Pax3, c-Met, Lbx1
Motor
Dorsal Hb9, FoxP1, Lhx1
Ventral Hb9, FoxP1, Isl1
Vo
Pr
Do
Vo
Pr
Sensory
Cut Ngn1/2, Brn3a, Runx1
Proprio Ngn1/2, Brn3a, Runx3
A
B
Fig. 25.8  Joint formation. (Modified from Pacifici M, Koyama
E, Iwamoto M. Mechanisms of synovial joint and articular
cartilage formation: recent advances, but many lingering
mysteries. Birth Defects Res C Embryo Today.
2005;75:237–248.)
Interzone
Joint
capsule
Distal
anlage
Artciular
cartilage
Synovial
cavity
Joint
formation
Morphogenesis
Cavitation
Chondrogenic precursors
Chondrocytes
Joint site
determination
Interzone
formation
+
Chondrocyte
differentiation
Proximal
end
Distal
end
Proximal
anlage

557
Limb development (embryology)
the hand (see Fig. 25.10). The intrinsic muscles arise from five
embryonic muscle layers, which differentiate and fuse in a
complex but logical manner.76,77 Following embryonic myo­
genesis, a second wave of myocyte precursors migrate into
the limb and coalesce around primary myofibers, forming
secondary myofibers and adding bulk to the muscle masses
as the fetus grows. It is during this secondary or fetal myo­
genesis that formation of motor endplates occurs and neuro­
muscular communication begins, further differentiating the
forming muscle with slow and fast fiber types.78,79
Innervation
Outgrowth of nerves into the limb bud lags behind muscle
migration (Fig. 25.11) and involves both motor and sensory
neurons.80 Motor neurons are specified early during spinal
cord development by exposure to Shh, initially from the
notochord and later from the floor plate of the developing
begin to produce myosin filaments. Satellite cells, important
for later growth and muscle regeneration, take up residence
just under the basal lamina of the developing myofibers.72
Concurrently, the tendon primordia further define the shape
of specific muscles with discrete tendinous attachments. For
example, expression of Lmx1b within the dorsal tendons
directs the unique pattern of extensor attachments74 and it is
likely that each upper limb muscle is shaped by a unique
combination of patterning factors.75
As in other aspects of upper limb development, there is
progressive differentiation from proximal to distal. Thus, as
the muscles of the upper arm take shape, migrating myocytes
invade the forearm to associate with the PTP and a new
mesodermal condensation forming at the presumptive wrist,
the intermediate tendon primordium. In the forearm, the
superficial muscles differentiate before the deep muscles. By
Carnegie stage 17, the distal tendon primordia form and
associate with migrating myocytes destined to be muscles of
Fig. 25.10  Muscular development in the upper limb.
Progressive myocyte migration and muscle formation
between Carnegie stages 13 through 21 showing the
ventral or volar surface. Note the resting flexed position
of the upper limb in the stage 21 embryo rotates the
upper arm so that the elbows shift from dorsal to
caudal and the forearm rotates medially at the elbow.
The palmaris longus and flexor carpi radialis are not
shown. PTP, Proximal tendon primordium; ITP,
intermediate tendon primordium; DTP, distal tendon
primordium; Bi, biceps; Tri, triceps; B, brachialis; BR,
brachioradialis; PL, flexor pollicis longus; FDP, flexor
digitorum profundus; FCU, flexor carpi ulnaris; FDS,
flexor digitorum superficialis.
Stage 13
Stage 15
Stage 17
Stage 19
Stage 21
PTP
ITP
DTP
Bi
PL
FDP
FCU FDS
BR
Fig. 25.11  Nervous development in the upper limb.
Progressive innervation of the upper limb and formation of
the brachial plexus. Rt, Nerve roots; T, trunks; U, upper; M,
middle; L, lower; C, cords; Lat, lateral; Med, medial; Pst,
posterior; A, axillary; Mc, musculocutaneous; R, radial; Md,
median; U, ulnar.
Rt
Stage 13
Stage 15
Stage 19
Stage 21
Stage 17
Lat
A
Mc
Md
U
R
Med Pst
T
C
U
M
T1
C4
C5
C6
C7
C8
L

558
SECTION IV
CHAPTER 25 • Congenital hand I: Embryology, classification, and principles
normal tissue. Dysplasia is a lack of normal organization of
cells into tissue. Dysmorphologists describe a fourth term,
disruption. As this process involves alteration of tissue that is
already formed, for the purposes of classification it is reason­
able to include those conditions that are considered to be
disruptions alongside those considered to be deformations.
Although the pathogenesis of some specific anomalies remains
obscure, the concept of separating malformations, deforma­
tions, and dysplasias provides a sound structure for categoriz­
ing congenital upper limb anomalies.
Ideally, a classification of congenital hand anomalies would
be based on etiology, with such a classification indicating the
site in the molecular pathway and/or the anatomical site in
the limb bud at which the aberration occurs, and one that also
is indicative of the timing of the causative disruption.
The first classification was probably that of Isidore St.
Hilaire in 1832.85 This introduced terms such as “phocomele”
(seal limb), “hemimele” (part of the limb missing), and
“ectromele” (limb absence). Frantz and O’Rahilly based their
classification on skeletal appearance.86 They introduced the
concepts of terminal and intercalary defects, subsequently
adding the subcategories of transverse and longitudinal
deficiencies and including the involvement of pre- or postaxial
position within the limb.86 Kelikian has summarized the
contributions of many authors in his classic text, Congenital
Deformities of the Hand and Forearm, but acknowledged that
“We have not as yet attained enough latitude of knowing
about congenital hand anomalies to formulate a comprehen­
sive classification.”87
Subsequently, the currently accepted surgical classification
of upper limb anomalies was that based on the proposals of
Swanson et al. in 1968,88 refined by Swanson and colleagues
in 19761 and 1983,89 accepted by the IFSSH and then expanded
by Knight and Kay in 20002 and Upton in 200690 to encompass
all anomalies. Although this system served us well, an increas­
ing number of surgeons, pathologists, and geneticists working
in the field of congenital limb anomalies began to question the
adequacy of this classification and have suggested alternative
approaches.91–94
Problems of the Swanson classification
The Swanson classification was derived from an understand­
ing of normal embryological development that was available
in the 1960s and 1970s. The system is based upon clinical
and radiological assessments that describe failures in certain
anatomical structures. The two major groupGs of this clas­
sification do offer an indication of the timing of the causative
insult by separating “failure of formation” from “failure of
differentiation”. However, formation and differentiation occur
together, and it may be impossible to determine whether any
specific anomaly is one or the other. Furthermore, the need
to create separate groups for “duplication”, “undergrowth”,
and “overgrowth” is illustrative of the inherent limitations of
using these descriptive terms as components of a classifica­
tion system, as these anomalies could also be considered as
failures of formation and/or differentiation.
A system based on appearance is unable to incorporate
changes based on our increasing understanding of etiology
and causation at a molecular level. Attempts to do so create
contradictions that are difficult to resolve. A consideration
of central clefting and symbrachydactyly is illustrative. The
neural tube.81,82 Motor neurons begin to express a combination
of transcription factors (e.g., Hb9/Mnx1, Lhx3/4) that promote
motor neuron migration into discrete columns within the
spinal cord and direct their axons to specific muscle groups.70
Within the limb fields (specified by Hox6 in the forelimb and
Hox10 in the hindlimb), a Hox accessory factor, FoxP1, is
expressed that assists in deciphering the subsequent Hox-
specific code within the limb for appropriate axon targeting.83
As the axons of the motor neurons enter the limb, those
expressing Lim1 (Lhx1) will project into the dorsal Lmx1b-
expressing compartment of the limb to target dorsal extensor
muscle groups. The remaining axons express Isl1 and will
enter the ventral compartment to target flexor muscles of the
limb.
Sensory processes accompany the axons of motor neurons
into the limb. The cell bodies of sensory neurons reside within
the dorsal root ganglion (DRG), which is derived from neural
crest cells. Specification of sensory neurons within the DRG is
characterized by upregulation of neurogenin1 and 2 (Ngn1/2)
and brain-specific homeobox/POU domain protein 3A
(Brn3a). Furthermore, cutaneous sensory neurons also express
a runt homeodomain transcription factor 1 (Runx1), while
neurons involved in proprioception express Runx2.
The nerve roots, containing motor and sensory processes
from C4 to T1, coalesce to form a meshwork or plexus that
eventually leads to the formation of three major trunks in the
upper limb – upper, middle, and lower (see Fig. 25.11, Carn­
egie stage 15). The segregation of dorsal and ventral processes
as the nerves project into the limb divides the plexus into
dorsal (posterior) and ventral (anterior) divisions, which form
the posterior, lateral, and medial cords, whose names relate
to their anatomic positions in the adult. The posterior cord
gives rise to the axillary and radial nerves. The lateral cord
gives rise to the musculocutaneous nerve and contributes to
the median nerve. The medial cord forms the ulnar nerve and
combines with processes from the lateral cord to form the
median nerve.
The initial trajectory of processes is independent of neuro­
muscular communication and instead depends on a combina­
torial expression of transcription factors that guide processes
to targets expressing specific patterning factors within the
limb.80 However, during secondary or fetal myogenesis, pat­
terning factors, motor endplate formation, and neuromuscular
communication are required for fiber-type differentiation and
survival of both muscles and nerves70,73,78
Anomalies of limb development and
their classification
Background
Congenital anomalies in the hand and upper limb demand a
reproducible and consistent terminology, a universal language
that allows discussion of complex clinical entities, indications
for treatment, and comparisons of results. The terminology of
dysmorphology offers a basis for understanding the etiology
of congenital limb anomalies.84 A malformation is an abnormal
formation of tissue resulting from abnormal cell formation.
Deformation differs from a malformation as the insult is to cells
that have already formed normally. It is a deformation of

559
Anomalies of limb development and their classification
deficiency in the forearm could be considered as an abnormal
induction of forearm radial structures. Whether any particular
condition is a failure of formation, a failure of differentiation,
or an abnormal induction is probably a dated and unhelpful
concept, the differences being those of semantics.
In the search for evidence to support the suggestion that
syndactyly, central polydactyly, and clefting should be classi­
fied within a single and new group, it is helpful to review the
conditions with these characteristics that have a known
genetic basis. Synpolydactyly (syndactyly type II) is caused
by an identified gene – HoxD13 – mapped to a known chro­
mosomal locus – 2q31–32.98 Clefting has not been described
as an association of this genetic abnormality. Central longitu­
dinal deficiency (clefting or split-hand/foot malformation) is
also inherited in an autosomal-dominant manner. Its locus is
known and differs from that of the synpolydactyly gene
mutation. Type I syndactyly, in which there is non-separation
of digits 3 and 4 in the hands, often accompanied by non-
separation of digits 2 and 3 in the feet, also involves an
abnormal gene, not yet identified, but which has been mapped
to yet another locus.99 From this, it becomes apparent that a
particular phenotype may result from abnormalities in several
genes at different chromosomal loci in one or many of the
complex pathways involved in normal hand development,
rather than from one constant gene abnormality. There may
also be variations in phenotypic expression of single-gene
mutations. It would appear that complex interactions involv­
ing formation of extra digits and joining of those digits are
associated with cleft formation.100 However, it is less certain
that an inexorable teratogenic sequence obligatorily links
isolated cases of polydactyly and syndactyly with clefting.101
The separation of symbrachydactyly from brachydactyly,
noted above, also imposes apparent contradictions. The
JSSH considers symbrachydactyly to be synonymous with
Swanson classification places central clefting of the hand
within the “failure of formation” group as a “central longitu­
dinal deficiency”. However, many would not view this condi­
tion as a longitudinal deficiency in the manner of radial and
ulnar longitudinal deficiencies for the following reasons: the
limb anomalies are usually confined to hands and feet; the
terminology erroneously suggests the presence of a central
axis within the developing limb; the elegant experimental
work and clinical observations of Miura,95 Ogino,96 and others
have drawn attention to the association of clefting with syn­
dactyly and polydactyly (Fig. 25.12). Consequently, the Japa­
nese Society for Surgery of the Hand (JSSH) introduced an
extra group within the Swanson classification, this being an
“abnormal induction of rays”.97 Although the introduction of
this new group was attractive and well based, such modifica­
tions of the IFSSH classification introduced significant
contradictions.
In this new subclassification of the JSSH, central polydac­
tyly became an “abnormal induction of rays”. However, radial
and ulnar polydactyly remained under the group “duplica­
tion”. Morphologically, the process of duplication, be it
central, radial, or ulnar, appears to be similar (Fig. 25.13). All
could be considered as an “abnormal induction of rays”.
Syndactyly, be it simple or complex with phalangeal
synostosis, was moved from “failure of differentiation” to
“abnormal induction” (Fig. 25.14). Yet under the system pro­
posed by the JSSH, symbrachydactyly, which has a component
of syndactyly, became a “transverse failure of formation”.
Brachydactyly, which may include symbrachydactyly as
a subcategory, remained within group 5, “undergrowth”.
Carpal synostoses and symphalangism remained within
“failure of differentiation”, although they both occur com­
monly in symbrachydactyly. All could be considered as an
“abnormal induction of rays”. Indeed, a longitudinal radial
Fig. 25.12  (A,B) Clinical and radiological
appearance of the association of clefting,
syndactyly, and polydactyly.
A
B

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SECTION IV
CHAPTER 25 • Congenital hand I: Embryology, classification, and principles
represents an appearance only and is unable to embrace the
above concepts.
The groups documented as “duplication”, “overgrowth”,
and “constriction ring syndrome” suffer from similar limita­
tions. It became clear that increasing problems with the
Swanson classification demanded an alternative approach.
The OMT classification
Oberg, Manske and Tonkin developed a classification system
that incorporated newer knowledge of the etiology, molecular
genetics, and developmental biology of congenital limb
anomalies,93,94 which was presented in the third edition of this
text.104 This system has undergone three major objective
assessments, which have resulted in some modifications.105–107
“transverse failure of formation” and therefore suggested that
symbrachydactyly be moved from group 5, “undergrowth”,
to group 1 of the Swanson classification.97,102 This necessitates
combining transverse deficiencies, in which terminal ectoder­
mal elements are absent, with symbrachydactyly, in which the
initial deficiency is middle phalangeal and, even in severe
cases, terminal elements – nail and terminal phalangeal rem­
nants – remain (Fig. 25.15). The Japanese allow for this by
adding a “peripheral hypoplasia type” to the five types of
the symbrachydactyly subclassification, so that all transverse
deficiencies are included as a form of symbrachydactyly.
Others consider this to be contradictory, believing symbrachy­
dactyly to be a distinct entity, and to have a clear definition
of intersegmental failure, which does not encompass terminal
transverse deficiencies.103 Regardless, the term “undergrowth”
A
B
C
Fig. 25.13  (A–C) Clinical and (D–F) radiological appearance of central, radial, and ulnar polydactyly at the proximal phalangeal level.
D
E
F

561
Anomalies of limb development and their classification
1). This classification scheme does not attempt to separate an
abnormal formation from an abnormal differentiation. Mal­
formations are subdivided according to whether the insult
affects the upper limb as a whole or the hand plate alone, and
whether it primarily involves one of the three axes of growth
and patterning described in the preceding section of this
chapter. This approach incorporates an understanding of the
mechanism of insult and the site within the developing limb
that is primarily affected.93,94 Symbrachydactyly, for instance,
is an example of abnormal tissue formation and differentia­
tion within the proximal–distal axis, as are the other transverse
failures of formation (Fig. 25.16). Radial longitudinal defi­
ciency involves primarily the radial–ulnar axis (Fig. 25.17)
and loss of dorsalization of hand and upper limb structures
in nail–patella syndrome involves the dorsal–ventral axis. In
all of these anomalies, the whole of the upper limb may be
involved, e.g., thumb hypoplasia with radial aplasia. Duplica­
tions that affect the whole of the upper limb, such as ulnar
dimelia, are malformations with abnormal axial patterning
The main alteration involves those conditions that were previ­
ously placed separately as not primarily involving one of the
three specific axes (unspecified axis). These have been incor­
porated into the two main malformation subgroups – upper
limb and hand plate alone. Other more minor modifications
and additions are included in Table 25.2. The reviews have
confirmed the efficacy of the OMT classification with good
inter- and intra-observer reliability.
All anomalies are placed within one of three groups defined
at the beginning of this section: group 1, malformations; group
2, deformations; and group 3, dysplasias (see Table 25.2).
The anomalies that were documented under groups 1, 2, 3,
and 5 in the Swanson scheme become malformations (group
Fig. 25.14  Syndactyly in association with (A) symbrachydactyly short finger type; (B) mitten hand; (C) ulnar longitudinal deficiency; (D) Greig cephalopolysyndactyly
syndrome.
A
B
C
D
Fig. 25.15  Symbrachydactyly monodactylous type with terminal ectodermal
elements.
Fig. 25.16  Symbrachydactyly with short arm, hand, and fingers.

562
SECTION IV
CHAPTER 25 • Congenital hand I: Embryology, classification, and principles
Table 25.2  Modified classification of congenital anomalies of the hand and upper limb (updated January 28, 2015)
I. Malformations
A. Abnormal axis formation/differentiation – entire upper limb
1. Proximal–distal axis

i. Brachymelia with brachydactyly

ii. Symbrachydactyly

a) Poland syndrome

b) Whole limb excluding Poland syndrome

iii. Transverse deficiency

a) Amelia

b) Clavicular/scapular

c) Humeral (above elbow)

d) Forearm (below elbow)

e) Wrist (carpals absent/at level of proximal carpals/at level of
distal carpals) (with forearm/arm involvement)

f) Metacarpal (with forearm/arm involvement)

g) Phalangeal (proximal/middle/distal) (with forearm/arm
involvement)

iv. Intersegmental deficiency

a) Proximal (humeral – rhizomelic)

b) Distal (forearm – mesomelic)

c) Total (phocomelia)

v. Whole limb duplication/triplication
2. Radial–ulnar (anterior–posterior) axis

i. Radial longitudinal deficiency – thumb hypoplasia (with
proximal limb involvement)

ii. Ulnar longitudinal deficiency

iii. Ulnar dimelia

iv. Radioulnar synostosis

v. Congenital dislocation of the radial head

vi. Humeroradial synostosis – Elbow ankyloses

vii. Madelung deformity
3. Dorsal–ventral axis

i. Ventral dimelia

a) Furhmann/Al-Awadi/Raas–Rothschild syndromes

b) Nail–patella syndrome

ii. Absent/hypoplastic extensor/flexor muscles
4. Unspecified axis

i. Shoulder

a) Undescended (Sprengel)

b) Abnormal shoulder muscles

c) Not otherwise specified

ii. Arthrogryposis
B. Abnormal axis formation/differentiation – hand plate
1. Proximal–distal axis

i. Brachydactyly (no forearm/arm involvement)

ii. Symbrachydactyly (no forearm/arm involvement)

iii. Transverse deficiency (no forearm/arm involvement)

a) Wrist (carpals absent/at level of proximal carpals/at level of
distal carpals)

b) Metacarpal

c) Phalangeal (proximal/middle/distal)
2. Radial–ulnar (anterior–posterior) axis

i. Radial deficiency (thumb – no forearm/arm involvement)

ii. Ulnar deficiency (no forearm/arm involvement)

iii. Radial polydactyly

iv. Triphalangeal thumb

v. Ulnar dimelia (mirror hand – no forearm/arm involvement)

vi. Ulnar polydactyly
3. Dorsal–ventral axis

i. Dorsal dimelia (palmar nail)

ii. Ventral (palmar) dimelia (including hypoplastic/aplastic nail)
4. Unspecified axis

i. Soft tissue

a) Syndactyly

b) Camptodactyly

c) Thumb in palm deformity

d) Distal arthrogryposis

ii. Skeletal deficiency

a) Clinodactyly

b) Kirner’s deformity

c) Synostosis/symphalangism (carpal/metacarpal/phalangeal)

iii. Complex

a) Complex syndactyly

b) Synpolydactyly – central

c) Cleft hand

d) Apert hand

e) Not otherwise specified
II. Deformations
A. Constriction ring sequence
B. Trigger digits
C. Not otherwise specified
III. Dysplasias
A. Hypertrophy
1. Whole limb

i. Hemihypertrophy

ii. Aberrant flexor/extensor/intrinsic muscle
2. Partial limb

i. Macrodactyly

ii. Aberrant intrinsic muscles of hand
B. Tumorous conditions
1. Vascular

i. Hemangioma

ii. Malformation

iii. Others
2. Neurological

i. Neurofibromatosis

ii. Others
3. Connective tissue

i. Juvenile aponeurotic fibroma

ii. Infantile digital fibroma

iii. Others
4. Skeletal

i. Osteochondromatosis

ii. Enchondromatosis

iii. Fibrous dysplasia

iv. Epiphyseal abnormalities

v. Others

563
Anomalies of limb development and their classification
Fig. 25.17  Radial longitudinal deficiency affecting arm, forearm, hand, and digits
of both limbs in brothers with Holt–Oram syndrome.
within the radial–ulnar axis. All of these are classified within
group 1A, according to the axis involved, unless the axis is
unspecified.
Alternatively, the primary defect may reside within the
hand plate alone and not involve proximal limb components.
It may affect one of the axes of development or be of unspeci­
fied axis. This approach allows incorporation of Swanson
group 3 “duplications”, radial and ulnar polydactyly, into a
group that indicates intuitively the anatomical site and the
axis in which the aberration occurs (Fig. 25.18). The triphalan­
geal thumb may best be included in this group. Dorsal dimelia
of the little finger is an example of hand plate involvement
involving the dorsal–ventral axis (Fig. 25.19). All of these
conditions are classified within group 1B. The cleft hand
complex, isolated syndactyly, and central synpolydactyly are
examples of hand plate conditions of unspecified axis. This
satisfies the concern that cleft hand complex is not a longitu­
dinal deficiency but rather a primary insult to the hand plate
(Figs. 25.12 & 25.20).
Group 2 in Table 25.2 allows the classification of amniotic
band sequence (constriction ring syndrome) as a deformation,
separating it from the malformations of group 1. The insult
affects a part already formed (Fig. 25.21).
Group 3, dysplasias, includes many otherwise difficult-to-
classify conditions that have previously been listed according
to their appearance. Limb hypertrophy and macrodactyly that
is consequent upon tumor formation are examples (Fig. 25.22),
as are the other tumorous conditions. All of these were previ­
ously classified either as a “failure of differentiation” (tumor­
ous conditions) or purely as a descriptive term – “overgrowth”
for macrodactyly or limb hypertrophy. There may be dissent
as to whether these conditions are in fact malformations or
deformations instead of dysplasias. Indeed, increasing knowl­
edge may demand their future transfer to either group 1 or
group 2. This system allows such adjustments.
This classification has the advantages of allowing inclusion
of all groups within a logical framework; of utilizing a common
terminology; and of indicating a site of anatomical insult in
IV. Syndromes*
A. Specified
1. Acrofacial dysostosis 1 (Nager type)
2. Apert
3. Al-Awadi/Raas–Rothschild/Schinzel phocomelia
4. Baller–Gerold
5. Bardet–Biedl Carpenter
6. Beales
7. Catel–Manzke
8. Constriction band (amniotic band sequence)
9. Cornelia de Lange (types 1–5)
10. Crouzon
11. Down
12. Ectrodactyly–Ectodermal Dysplasia–Clefting
13. Fanconi pancytopenia
14. Fuhrmann
15. Goltz
16. Gorlin
17. Greig Cephalopolysyndactyly
18. Hajdu–Cheney
19. Hemifacial Microsomia (Goldenhar syndrome)
20. Holt–Oram
21. Lacrimoauriculodentodigital (Levy–Hollister)
22. Larsen
23. Leri–Weill Dyschondrosteosis
24. Moebius sequence
25. Multiple synostoses
26. Nail–patella
27. Noonan
28. Oculodentodigital dysplasia
29. Orofacialdigital
30. Otopalataldigital
31. Pallister–Hall
32. Pfeiffer
33. Pierre Robin
34. Poland
35. Proteus
36. Roberts–SC phocomelia
37. Rothmund–Thomson
38. Rubinstein–Taybi
39. Saethre–Chotzen
40. Thrombocytopenia absent radius
41. Townes–Brock
42. Trichorhinophalangeal (types 1–3)
43. Ulnar–mammary
44. VACTERLS association
B. Others
*The specified syndromes are those considered most relevant; however, many other syndromes have a limb component categorized under “B. Others”.
VACTERLS, vertebral defects, anal atresia, cardiac defects, tracheo-esophageal fistula, renal anomalies, and limb abnormalities.
(Source: )
Table 25.2  Modified classification of congenital anomalies of the hand and upper limb (updated January 28, 2015)—cont’d

564
SECTION IV
CHAPTER 25 • Congenital hand I: Embryology, classification, and principles
Fig. 25.18  (A,B) Radial and ulnar
duplications demonstrate involvement of
radial and ulnar axial abnormalities within
the hand.
A
B
Fig. 25.19  (A,B) Dorsal dimelia of the
little finger.
A
B