Operative Technique in Plastic Surgery – Kevin C.Chung

(TECH FIG 1A).
■ Using a no. 15 blade, carefully incise the TCL, using a controlled “push,”
rather than a slicing motion.
■ Once the median nerve is visualized, complete as much of the release of the
TCL under direct visualization with the use of a scalpel blade.
■ Then use tenotomy scissors to spread both superficial and deep to the TCL,
being careful to separate the median nerve (which can be quite adherent)
from the deep surface of the TCL. Insert one tine of the tenotomy scissors
and divide the TCL distally until the palmar fat surrounding the superficial
vascular arch of the palm is reached (TECH FIG 1B,C).
■ Attention should now be turned toward dividing the proximal TCL and
contiguous antebrachial fascia. The surgeon should change positions so that
he or she is now seated at the end of the hand table for optimal visualization.
Extend the skin incision proximally if necessary (TECH FIG 1D).
■ Again dissect both superficial and deep to the TCL, separating the median
nerve from the deep surface of the TCL. Under direct visualization, release
the proximal end of the TCL.
■ Continue spreading and dissecting proximally, exposing the deep
antebrachial fascia. It is important for the surgical assistant to use two Senn
retractors to lift away the skin and subcutaneous tissue to expose the
antebrachial fascia proximally. Use tenotomy scissors to release the
antebrachial fascia proximally for at least 1 cm proximal to the distal wrist
crease.
■ Consider lifting the flexor tendons in the carpal tunnel using a Ragnell
retractor, and inspect for any mass lesions, such as ganglia, within the tunnel.
■ Inject bupivacaine (0.25% with epinephrine) locally into the incision.
■ Deflate the tourniquet while holding pressure on the incision.
■ Attain meticulous hemostasis.
■ Close the incision with 4-0 nylon simple interrupted or horizontal mattress
sutures.
■ Apply a soft, bulky dressing consisting of nonstick gauze, fluffs, and Kerlix
or Ace wrap. Allow for immediate postoperative motion.

TECH FIG 1 • Open carpal tunnel release. A. A small
self-retaining retractor and a Ragnell retractor provide
exposure of the TCL. B. After bluntly spreading above
and below the TCL, it is divided with the tenotomy
scissors. C. Distal division of the TCL has been
completed to the level of the distal palmar fat. D. The
proximal antebrachial fascia is exposed by bluntly
spreading above and below and then divided with the
tenotomy scissors.
■ Endoscopic Carpal Tunnel Release
Preparation and Incision
■ To avoid fogging of the lens, the lens can be placed in warm water or saline
for several minutes prior to use. Otherwise, defogging solution can be applied
to the lens immediately prior to use.

■ Position the monitor at the distal end of the hand table. Assemble the
blade/scope unit and then white-balance the camera (can use a white surgical
sponge). Test the camera and endoscopic device blade prior to proceeding.
Have defogging solution available on a sponge to defog the lens, if needed.
Place a folded OR towel under the wrist to extend it.
■ Mark a transverse incision approximately 1 to 1.2 cm in length at the distal
transverse wrist crease, slightly ulnar to the palmaris longus (if present)
(TECH FIG 2).
■ Exsanguinate the arm with an Esmarch bandage, and inflate the tourniquet to
250 to 300 mm Hg (or 100 mm Hg over systolic blood pressure).
Accessing the Carpal Tunnel
■ Incise the skin with a 15 blade, and use bipolar cautery to coagulate small
subcutaneous vessels.
TECH FIG 2 • A,B. Incision marking for endoscopic
carpal tunnel release. The palmaris longus tendon
(when present) is often palpable when the thumb and
small finger are opposed and the wrist flexed. The
incision is marked transversely in the distal flexion
crease of the wrist, slightly ulnarly translated over
palmaris longus (PL, Palmaris longus).
■ If excessive fatty tissue is present, perform a direct subcutaneous
lipectomy.
■ Use tenotomy scissors to release the superficial antebrachial fascia.
■ Two Ragnell retractors are then used to bluntly spread through the
subfascial tissue to expose the TCL.

■ Pick up the TCL with Adson forceps distally (TECH FIG 3A), and make a
small transverse fasciotomy with a no. 15 blade scalpel until the underlying
nerve is visualized.
■ Once the fascial incision is large enough to insert the tips of tenotomy
scissors, use the scissors to extend the fasciotomy transversely with a single,
large spreading motion.
■ Then, make a longitudinal fascial incision along the ulnar aspect of the
fasciotomy for about 5 mm to create an L-shaped flap.
■ Use a small double-skin hook to lift the L-shaped flap of the proximal TCL
(TECH FIG 3B).
■ With a synovial elevator, using gentle pushing motions (not scraping), clear
off the deep surface of the TCL, which helps to effectively push the oft-
adherent median nerve away from the TCL.
■ Advance the elevator until it can be passed into the palm and palpated there
with your left hand. This should be done in line with the ring finger (TECH
FIG 3C,D).
■ Sequentially introduce two progressively larger sound dilators into the
dissected space between the median nerve and the TCL (TECH FIG 3E,F).
■ Take the light off standby, and again check the blade engagement mechanism
and make sure the blade recedes back into the blade sheath upon trigger
release.
Inserting and Advancing the Endoscope
■ Insert the assembled scope and blade in line with the ring finger.
■ Rotate the blade sheath slightly ulnarly while introducing it beneath the L-
shaped fascial flap.
■ If using hot water to eliminate fogging of the camera, after placing the
blade/endoscope unit deep to the TCL, remove the scope from the sheath and
immerse it in hot water. Rub it dry with a 4 × 4 Raytec gauze. Turn the room
lights down, and reintroduce the scope into the blade unit.

TECH FIG 3 • Accessing the carpal tunnel. A. Once
exposed, the TCL is grasped with forceps, and a small
transverse nick is made with a no. 15 blade. Next, a
blunt spread of the tenotomies under the TCL clears
the median nerve from its undersurface, and the
incision is extended longitudinally along the ulnar
aspect to create an L-shaped flap. B. A small double
hook is used to retract the L-shaped flap. C. From top
down: synovial elevator, small dilator, large dilator; to
be used in that sequence. D. Using the synovial
elevator, gentle pushing motions (not pulling) clear the
synovium from the deep surface of the TCL. E,F. The
smaller dilator is then passed through the carpal
tunnel, followed by the larger dilator. The tunnel is now

prepared for insertion of the endoscopic device.
TECH FIG 4 • Endoscopic view showing the TCL
forming the roof of the carpal tunnel, predivision. Note
that it has been cleared of adherent synovium. Also
note the palmar fat visible at the distal extent of the
tunnel.
■ If using defogging solution, this step can be skipped.
■ Advance the scope until the distal aspect of the TCL is visualized, usually
corresponding to the 3.5-cm measurement on the sheath.
■ While watching the video monitor, the surgeon’s hand that is not controlling
the scope can be used to push on the palm repeatedly to determine where the
distal edge of the TCL is located, since the tight TCL will minimize motion
of the tissues even upon deep palpation.
■ However, the tissue distal to the TCL will “bounce” more easily with
palpation (TECH FIG 4).
Releasing the Carpel Tunnel and Completion
■ Ensure that the hand is completely flat against the towel (with the thenar

eminence firmly pushed down by the assistant) to tighten the TCL while
moving the nerve as far away from the blade as possible.
■ Engage the blade and slowly pull the scope proximally to cut the distal end
of the TCL, stopping at approximately halfway (TECH FIG 5A).
■ Disengage the blade and readvance the scope to visualize the distal aspect
of the TCL, ensuring no uncut bands remain distally. Any residual fibers
can be cut at this time (TECH FIG 5B).
■ The scope is pulled proximally again, and the blade is engaged again just
before reaching the proximal, uncut edge of the TCL.
■ Continue pulling the device proximally to divide the remainder of the
ligament while applying pressure to the palm with the hand not controlling
the scope, which “pushes” the TCL into closer approximation with the
blade.
■ The scope can be reintroduced to visualize any residual fibers of TCL,
though after release of the TCL, the superficial fat can obscure the view seen
on the monitor.
■ Remove the scope.
■ Introduce closed tenotomy scissors under the cut TCL (superficial to the
nerve).
■ Using a bimanual palpation technique, the tips of the tenotomy scissors can
be gently run along the deep surface of the palm to determine if any fibers
of TCL remain while the surgeon’s other hand follows the tips of the
tenotomy scissors on the surface of the palm.
■ Attention should now be turned toward dividing the proximal antebrachial
fascia, which is a very important part of the endoscopic carpal tunnel release.
■ The surgeon should change positions to be seated at the end of the hand
table for optimal visualization.
■ Retract the skin and fat above the proximal superficial and deep antebrachial
fascia using a Ragnell retractor, and divide the antebrachial fascia proximally
with tenotomy scissors for approximately 2 cm.
■ The incision can be approximated with 4-0 nylon suture in a simple or
horizontal mattress fashion.
■ Infiltrate a 0.25% bupivacaine with epinephrine into the incision, along with
the area of the released TCL and antebrachial fascia.
■ Apply a soft dressing of fluffs and a 4-in. Kling wrap.
■ Apply firm pressure at the incision site through the dressing while deflating

the tourniquet.
TECH FIG 5 • A. With the blade engaged, division
begins at the distal extent of the TCL by slowly
withdrawing the device. B. Following the initial pass of
the blade, much of the TCL has been divided,
exposing the overlying pink palmar fascia. Note the
band of intact TCL that must be divided with a second
pass.
■ Hypothenar Fat Flap
■ In cases of recurrent or recalcitrant carpal tunnel syndrome (CTS), excessive
scar formation may contribute to entrapment of the nerve. The hypothenar fat
flap is a technique to interpose healthy, vascularized tissue over the nerve to
prevent recurrence from aggressive scar formation.
■ Exsanguinate the arm with an Esmarch bandage, and inflate the tourniquet to
250 mm Hg (or 100 mm Hg over systolic blood pressure).
■ Make a linear incision just radial to the hypothenar eminence, and carry
dissection down to the carpal tunnel to identify the median nerve.
■ Typically, the hypothenar fat flap is used for the treatment of recalcitrant
CTS, so the incision can be made through the previous surgical scar
(TECH FIG 6A).
■ Perform external neurolysis of the median nerve.

■ Using sharp dissection, develop a subdermal plane over the adipose tissue of
the hypothenar region, being cautious not to make the cutaneous flap too thin.
Carry this dissection to the dermal insertion of the palmaris brevis12 (TECH
FIG 6B).
■ Perform deep dissection under the fat pad, directly over the hypothenar
musculature, until the ulnar nerve and artery are visualized.
■ Check if the flap has been sufficiently mobilized to be advanced to the radial
wall of the carpal tunnel (TECH FIG 6C,D).
■ If not, carefully perform additional dissection, being careful to preserve the
vascular pedicles of the flap and the ulnar neurovascular structures.
■ Retract the carpal tunnel contents ulnarly, and place the hypothenar fat pad
flap volar to the median nerve and deep to the radial leaf of the TCL. Place
horizontal mattress sutures through the flap and into the radial wall of the
carpal tunnel. Tag these sutures and sequentially tie them once all have been
placed.
■ Irrigate the wound and deflate the tourniquet. Achieve meticulous
hemostasis.
■ Approximate the skin using 4-0 nylon suture in a simple interrupted or
horizontal mattress fashion. Apply dressings as described above.

TECH FIG 6 • Hypothenar fat pad flap. A. The carpal
tunnel has been released, the median nerve has been
neurolysed, and a subdermal plane has been
developed over the adipose of the hypothenar region.
B. The hypothenar fat pad flap must be mobilized
sufficiently to reach the radial wall of the carpal tunnel.
The subdermal plane is developed to the dermal
insertion of palmaris brevis, and the deep dissection is
carried out just over the musculature until the ulnar
neurovascular bundle is visualized. C. The elevated
hypothenar fat pad flap, prior to inset.
PEARLS AND PITFALLS

Incomplete
release
■ Be sure to adequately release the distal TCL in the palm to the level
of the palmar fat pad, and the antebrachial fascia for 1–2 cm in the
forearm. In endoscopic CTR, check for bands of undivided TCL by
palpating with closed tenotomy scissors.
Palmar
cutaneous
branch
injury
■ Make incision ulnar to axis of ring finger. Look out for ulnar
cutaneous branch variant.
Recurrent
motor
branch
injury
■ Subligamentous and transligamentous variants are at increased risk
specifically with endoscopic CTR. Rare variant that exits median
nerve ulnarly and curves distally around TCL is highest risk.2
Superficial
palmar arch
injury
■ Located 2–26 mm from the distal edge of TCL, contained in palmar
fat pad15
Radially
located
ulnar artery
■ In some patients, the ulnar artery is located radial to the hook of
hamate, making it vulnerable during CTR.15
Visualization
on
endoscopy
■ Watch the monitor closely at all times while the endoscopic device
is entering, exiting, or within the carpal tunnel.
Anesthesia
■ Endoscopic release is very difficult with local anesthesia, as the
liquid anesthetic obscures visualization.
POSTOPERATIVE CARE
■ We do not use postoperative splinting, but rather a soft dressing that the patient
removes after 24 to 48 hours. We encourage use of the hand right away to
encourage nerve gliding and prevent adhesion formation.
■ We do not routinely refer our patients to hand therapy postoperatively.
Therapy can be useful in specific cases such as desensitization for abnormal
postoperative hypersensitivity or if there is stiffness or immobility.
OUTCOMES
■ A Cochrane systematic review found that both surgical and nonoperative
treatments of CTS are effective, but surgery produces a longer-lasting relief of

symptoms than nonoperative therapies.
■ Surgical release yields continued improvement for around 12 months
postoperatively, whereas improvements from nonoperative therapies plateau at
around 3 months.1
COMPLICATIONS
■ Postoperative recurrence has been reported in 3% to 20% of cases.16,17
■ Etiologies of persistence or recurrence include incompletely released TCL,
abundant scar formation from a number of causes, neuropathy of other etiology
(eg, polyneuropathy), and psychosocial factors.16
■ Serious complications are rare but include injury to the median nerve,
recurrent motor branch, or palmar cutaneous branch.
■ Other complications include painful or hypertrophic scar, hematoma, infection,
and wound healing problems.
REFERENCES
1. Shi Q, MacDermid JC. Is surgical intervention more effective than non-
surgical treatment for carpal tunnel syndrome? A systematic review. J Orthop
Surg Res. 2011;6:17.
2. Lanz U. Anatomical variations of the median nerve in the carpal tunnel. J
Hand Surg [Am]. 1977;2:44-53.
3. Stevens JC, Smith BE, Weaver AL, et al. Symptoms of 100 patients with
electromyographically verified carpal tunnel syndrome. Muscle Nerve.
1999;22:1448-1456.
4. Robinson LR. Electrodiagnosis of carpal tunnel syndrome. Phys Med Rehabil
Clin N Am. 2007;18(4):733-746.
5. Durkan JA. A new diagnostic test for carpal tunnel syndrome. J Bone Joint
Surg Am. 1991;73(4):535-538.
6. Robinson LR. Entrapment neuropathies of the median and ulnar nerves.
AANEM Course. 2011;27-30.
7. Robinson LR. Role of neurophysiologic evaluation in diagnosis. J Am Acad
Orthop Surg. 2000;8:190-199.
8. Sears ED, Swiatek PR, Hou H, Chung KC. Utilization of preoperative
electrodiagnostic studies for carpal tunnel syndrome: an analysis of national
practice patterns. J Hand Surg Am. 2016;41(6):
665-672.e1.
9. Blazar PE, Floyd WE, Han CH, et al. Prognostic indicators for recurrent

symptoms after a single corticosteroid injection for carpal tunnel syndrome. J
Bone Joint Surg. 2015;97:1563-1570.
10. Mackinnon SE, Hudson AR, Gentili F, et al. Peripheral nerve injection injury
with steroid agents. Plast Reconstr Surg. 1982;69:482-490.
11. Osei DA, Calfee RP, Stepan JG, et al. Simultaneous bilateral or unilateral
carpal tunnel release? A prospective cohort study of early outcomes and
limitations. J Bone Joint Surg. 2014;96:889-896.
12. Strickland JW, Idler RS, Lourie GM, Plancher KD. The hypothenar fat pad
flap for management of recalcitrant carpal tunnel syndrome. J Hand Surg
[Am]. 1996;21:840-848.
13. Agee JM, McCarroll HR, Tortosa RD, et al. Endoscopic release of the carpal
tunnel: a randomized prospective multicenter study. J Hand Surg
[Am].1992;17:987-995.
14. Chow JC. Endoscopic carpal tunnel release: two-portal technique. Hand Clin.
1994;10:637-646.
15. Cobb TK, Knudson GA, Cooney WP. The use of topographical landmarks to
improve the outcome of Agee endoscopic carpal tunnel release. Arthroscopy.
1995;11:165-172.
16. Louie D, Earp B, Blazar P. Long-term outcomes of carpal tunnel release: a
critical review of the literature. Hand. 2012;7:242-246.
17. Cobb TK, Amadio PC. Reoperation for carpal tunnel syndrome. Hand Clin.
1996;12:313-323.

27
CHAPTERUlnar Tunnel Syndrome
Mary Claire Manske and Jason H. Ko
DEFINITION
■ Ulnar tunnel syndrome, first described by DuPont et al. in 1965, is a
compressive neuropathy of the ulnar nerve at the wrist that presents with a
variable constellation of sensory and motor symptoms, depending on the site of
nerve compression within the ulnar tunnel.1
■ The ulnar tunnel is commonly referred to as Guyon canal after Jean Casimir
Felix Guyon, a French surgeon who first described this anatomic space in
1861.2
ANATOMY
■ The ulnar tunnel is a fibro-osseous canal that extends from the proximal edge
of the volar carpal ligament to the hook of the hamate and the fibrous arch of
the hypothenar muscles distally.
■ Medially, it is bordered by the pisiform, flexor carpi ulnaris (FCU), and
abductor digit minimi; laterally, it is limited by the hook of the hamate,
transverse carpal ligament, and extrinsic flexor tendons.
■ The roof of the ulnar tunnel is composed of the volar carpal ligament, palmaris
brevis, and hypothenar fascia; the floor is formed by the transverse carpal
ligament, pisohamate ligament, pisometacarpal ligament, and opponens digiti
minimi3 (FIG 1A).
■ The contents of the ulnar tunnel include the ulnar nerve, ulnar artery and venae
comitantes, and fat. The ulnar nerve is ulnar and dorsal to the ulnar artery.
■ In the distal forearm, the ulnar nerve travels volar to the flexor retinaculum
before entering the ulnar tunnel. Although variations exist,4 the ulnar nerve
bifurcates within the tunnel into superficial and deep branches approximately 6

mm distal to the distal pole of the pisiform.
■ The superficial branch innervates the palmaris brevis and then continues as a
sensory nerve, providing sensation to the hypothenar eminence, small finger,
and ulnar side of the ring finger.
FIG 1 • A. Anatomy of the ulnar tunnel. The ulnar tunnel
is defined dorsally by the transverse carpal ligament;
volarly by the volar carpal ligament; ulnarly by the
pisiform, FCU, and ADM; and radially by the hook of the
hamate. B. Anatomy of the ulnar nerve in the ulnar
tunnel. The dorsoulnar fibers of the ulnar nerve become
the deep motor branch innervating the intrinsic hand
muscles, while the volar-radial fibers provide sensory
fascicles to the small finger and ulnar side of the ring
finger.
■ After passing through the ulnar tunnel, the deep motor branch of the ulnar
nerve runs through the pisohamate hiatus just distal to the ulnar tunnel, which
is bordered by the pisohamate ligament dorsally and by the fibrous arch of the
hypothenar fascia volarly. The deep motor branch curves around the hook of
the hamate to innervate the abductor digiti minimi (ADM), flexor digiti
minimi, opponens digiti minimi, interossei, third and fourth lumbricals,
adductor pollicis, and flexor pollicis brevis (FIG 1B).

■ The ulnar nerve at the wrist has been divided into three zones, which can be
used to correlate clinical symptoms to the site of compression.2,5,6
■ Zone I: From the proximal edge of the volar carpal ligament to the
bifurcation of the ulnar nerve into motor and sensory branches. Compression
in zone I results in intrinsic muscle weakness and sensory deficits over the
hypothenar eminence and small and ring fingers.
■ Zone II: From just distal to the bifurcation to the fibrous arch of the
hypothenar muscles and contains the deep motor branch of the ulnar nerve.
Compression in this zone presents with ulnar-innervated intrinsic motor
weakness and intact sensation in the ulnar nerve sensory distribution.
■ Zone III: Also begins just distal to the bifurcation and includes the sensory
branch of the ulnar nerve. Compression at this level results in diminished
sensation in the volar aspect of the small finger and volar ulnar ring finger.
PATHOGENESIS
■ Many cases of ulnar tunnel syndrome are idiopathic.7 Space-occupying
lesions, aberrant musculature, carpal tunnel syndrome, and acute and chronic
trauma have also been implicated in the pathogenesis of ulnar nerve
compression at the wrist.
■ Space-occupying masses in the ulnar tunnel are reported to cause
compression of the ulnar nerve or its branches, including ganglia, lipomas,
ulnar artery thrombosis, ulnar artery pseudoaneurysm, hemangioma,
osteoarthritis and rheumatoid arthritis, edema, proliferative synovitis, and
bony deformity.
■ Hypertrophic hypothenar muscles or anomalous muscles (hypothenar
adductor) may cause ulnar nerve compression.
■ Carpal tunnel syndrome may cause compression of the ulnar nerve distally, as
increased pressure in the carpal tunnel is transmitted to the adjacent ulnar
tunnel.
• Seventy-one percent of patients with ulnar tunnel syndrome have a
concomitant diagnosis of carpal tunnel syndrome.7
■ Fractures and dislocations
• Hook of hamate fractures: Fracture displacement or associated hematoma
and edema may compress the ulnar nerve.
• Dorsally displaced distal radius fractures and other carpal fractures can
cause ulnar nerve palsies secondary to traction on the ulnar nerve or edema.
■ Chronic compression

• “Handlebar palsy” in long-distance cyclists who place prolonged pressure
on the hypothenar area
■ Chronic repetitive microtrauma or vibration
• “Hypothenar hammer syndrome” in patients who use high-impact vibratory
equipment with the wrist extended (eg, jackhammer) results in direct trauma
to the ulnar artery leading to thrombosis, which may compress the ulnar
nerve and/or cause ischemia.
PATIENT HISTORY AND PHYSICAL FINDINGS
■ History and physical examination findings may be purely sensory, purely
motor, or mixed sensory and motor, depending on the location of pathology.
■ History
■ Sensory complaints: numbness and/or paresthesias in small and ring finger
• Patients with ulnar tunnel syndrome do not present with sensory disturbance
over the dorsal aspect of the hand, given that the dorsal sensory branch of
the ulnar nerve supplying this area branches from the ulnar nerve proximal
to the ulnar tunnel.
• Cold intolerance or pain in the ring and small fingers
■ Motor deficits: clumsiness, loss of coordinated hand function, weakness of
pinch and grasp, clawing
■ History of trauma
• Acute: direct blow or sports injury (consider fractures, dislocation)
• Chronic: use of power tools, cycling (consider ulnar artery thrombosis,
pseudoaneurysm, or compression)
■ Comorbid medical conditions: rheumatoid arthritis, osteoarthritis, diabetes
mellitus, carpal tunnel syndrome
■ Physical Examination
■ Inspection: intrinsic muscle atrophy/wasting or clawing; mass or fullness;
ecchymosis, swelling, or other evidence of trauma; compare to contralateral
upper extremity
■ Palpation: tenderness may indicate fracture; identify presence of a mass
(ganglia, lipomas)
■ Sensory exam: decreased sensation to light touch in small and ulnar ring
finger; Semmes-Weinstein monofilament or two-point discrimination test
■ Motor exam: intrinsic motor weakness, index finger abduction (assessment of
the first dorsal interosseous muscle), or the cross-finger test (asking the

patient to cross the middle finger over the index finger to assess the first volar
and second dorsal interossei)
■ Special motor tests
• Froment sign: Positive test when patient is unable to use adductor pollicis
for lateral pinch. Instead, patients compensate with the median nerve
innervated flexor pollicis longus to flex the thumb interphalangeal joint.
Positive test indicates dysfunction of ulnar nerve motor fibers, although it
does not localize the site of the lesion.
• Jeanne test: Test is positive, indicating ulnar motor neuropathy, when the
patient hyperextends the metacarpophalangeal joint to compensate for weak
adductor pollicis during lateral pinch.
• Wartenberg sign: Inability to adduct the small finger secondary to paralysis
of the third palmar interosseous muscle. Positive test indicates an ulnar
motor neuropathy.
■ Vascular exam: palpation of radial and ulnar artery pulses, bruits, or thrills;
Doppler examination of radial and ulnar artery; Allen test to assess ulnar
artery patency
■ Provocative tests: Tinel and Phalen test over pisiform (Phalen test over
pisiform is more sensitive than Tinel for ulnar tunnel syndrome)8
■ Must rule out alternative sites of nerve compression: cubital tunnel
syndrome, carpal tunnel, cervical radiculopathy, thoracic outlet syndrome
IMAGING
■ Electrodiagnostic studies are indicated in nearly all patients with a suspected
diagnosis of ulnar tunnel syndrome. The need for additional imaging is
determined by the suspected structural etiology of the patient’s ulnar tunnel
symptoms; bony pathology requires x-ray and/or CT scan; vascular pathology
should be evaluated with ultrasound or contrast arteriography; soft tissue
masses should be worked up with an MRI. In addition, elbow or cervical spine
imagine (x-rays, MRI) may be indicated if there is concern for more proximal
pathology.
■ Electrodiagnostic studies are useful to confirm and localize ulnar nerve
entrapment.
• Conduction velocity of the ulnar nerve across the elbow and the wrist can
determine the location of ulnar nerve entrapment (elbow, wrist, zone I, II, or
III).
• The most sensitive electrodiagnostic study for ulnar tunnel syndrome is the

distal motor latency to the first dorsal interosseous combined with
conduction velocity across the wrist (90% sensitivity).9
• Zone I lesions are characterized by decreased sensory responses and
prolonged latency to the first dorsal interosseous and ADM. Zone II lesions
show prolonged latency to the first dorsal interosseoi (and possibly
hypothenar muscles) with normal sensory findings. Zone III lesions show
only decreased ulnar sensory responses without motor deficits.10
■ Radiographic studies
■ Posteroanterior, lateral, and oblique views of the wrist are useful when
fracture or dislocation is the suspected etiology of the patient’s ulnar nerve
symptoms.
■ A 30-degree supinated oblique view with the thumb abducted or carpal
tunnel view is useful when there is clinical concern for pisotriquetral joint
pathology or hook of the hamate fracture, respectively.
■ The indication for obtaining a CT scan in the setting of ulnar tunnel symptoms
is similar to that for x-rays. CT scan is particularly useful in detecting hook of
hamate fractures.
■ Magnetic resonance imaging is useful for identifying and localizing soft tissue
masses, aberrant musculature, vascular anomalies, and hook of hamate
fractures.
■ Ultrasound has similar indications to MRI but is less costly.11
■ Arteriography serves as the standard for evaluated ulnar artery pathology (eg,
thrombosis, pseudoaneurysm).12
DIFFERENTIAL DIAGNOSIS
■ Cubital tunnel syndrome or proximal compression of the ulnar nerve
■ Carpal tunnel syndrome
■ Cervical radiculopathy
■ Neuromuscular disorders (Charcot-Marie-Tooth, amyotrophic lateral sclerosis)
■ Malignant peripheral nerve sheath tumors
■ C8-T1 brachial plexopathy
■ Central nerve system lesion
■ Poliomyelitis
NONOPERATIVE MANAGEMENT
■ Nonoperative management consisting of activity modification, rest, and a short

course of bracing in a neutral wrist splint may be considered in patients without
motor symptoms.
■ Activity modification for ulnar tunnel symptoms secondary to hypothenar
eminence compression. Cyclists with handlebar palsy may modify the
position of their handlebars to prevent the compression of the ulnar base of
the palm.
■ Patients with hypothenar hammer syndrome without thrombosis and
symptoms of digital ischemia may attempt nonoperative intervention,
consisting of the following:
• Smoking cessation, avoidance of trauma, protective gloves, change of
occupation, cold avoidance, and calcium channel blockers13
■ Cortisone injections are not indicated for ulnar tunnel syndrome because
inflammation is rarely the cause of ulnar tunnel syndrome and there is a high
risk of neurovascular injury when injecting into this confined space.
SURGICAL MANAGEMENT
■ Indications:
■ Failure of nonoperative intervention
■ Loss of two-point discrimination
■ Presence of intrinsic muscle weakness or atrophy
■ Severe electrodiagnostic abnormalities
■ Operative intervention for ulnar tunnel syndrome consists of ulnar nerve
decompression through the distal ulnar tunnel. Additional procedures may be
performed as needed to address the causative pathology.
■ Space-occupying mass requires mass excision in addition to ulnar nerve
decompression in the ulnar tunnel.
■ Ulnar artery thrombosis or aneurysm should be treated with artery
reconstruction and ulnar nerve decompression.
■ Ulnar tunnel syndrome secondary to carpal tunnel syndrome often improves
with carpal tunnel release alone, and additional release of the ulnar tunnel is
not recommended.
■ Optimal outcomes are achieved when all sources of pathology are addressed.
Preoperative Planning
■ Indications for operative intervention include failure of nonoperative
intervention, motor weakness or loss of two-point sensibility in the ulnar nerve
distribution due to ulnar nerve compression distally, or severe electrodiagnostic

changes involving the ulnar nerve at the wrist.
■ Electrodiagnostic studies should be reviewed to confirm the precise location of
ulnar nerve compression and appropriate site of decompression.
■ Relevant imaging studies must be reviewed to allow the surgeon to address all
etiologies of ulnar nerve symptoms.
Positioning
■ Patients are positioned supine on a well-padded operating table with the
affected limb on a hand table.
■ The operating table is turned so that the hand table faces the center of the
room.
■ A nonsterile tourniquet is applied to the affected upper extremity.
Approach
■ A volar approach to the ulnar nerve at the wrist is the most direct approach and
allows accesses to the relevant pathology.
T E C H N I Q U E S
■ Ulnar Tunnel Release and Ulnar Nerve
Decompression
Exposure
■ Operative limb is elevated and exsanguinated with an elastic bandage
immediately prior to tourniquet elevation.
■ Alternatively, or in addition to a tourniquet, 0.25% bupivacaine with
epinephrine can be injected into the planned incision site for postoperative
comfort and intraoperative hemostasis.
■ Identify landmark for incisions: The pisiform is easily palpated in the ulnar
base of the palm. The hook of the hamate is located 1 cm distal and 1 cm
radial to the pisiform and can be palpated.
■ A no. 15 blade scalpel is used to make a 4-cm longitudinal or curvilinear
incision through the skin paralleling the thenar crease between the pisiform
and hook of the hamate, approximately 6 mm ulnar to the thenar crease
(TECH FIG 1).

■ To extend proximally into the forearm, the incision should cross the wrist
crease obliquely and may continue proximally adjacent to the flexor carpi
ulnaris tendon.
■ To extend the incision distally into the palm, the incision may be extended
in a zigzag or Bruner fashion.
Dissection
■ Tenotomy scissors are used to dissect through the subcutaneous tissue, and
gentle skin retraction is provided by two double-prong skin hooks.
TECH FIG 1 • Incision for ulnar tunnel release. In the
palm, a longitudinal incision is centered between the
pisiform and hook of the hamate. The incision crosses
the wrist flexion crease obliquely before extending
proximally adjacent to the flexor carpi ulnaris (FCU)

tendon. P, pisiform; H, Hook of hamate.
TECH FIG 2 • In the forearm, the ulnar neurovascular
bundle is identified deep to the antebrachial fascia
between the FCU tendon and tendons of the finger
flexors. At this location, the ulnar nerve is deep and
ulnar to the artery.
■ A cutaneous branch of the ulnar nerve crosses the distal aspect of the
incision in 15% of patients. Care must be taken to identify and protect this
nerve to avoid a painful neuroma if injured.
■ Dissection continues until the volar carpal tunnel and palmaris brevis are
identified.
■ Proximally in the forearm, the ulnar neurovascular bundle is identified deep
to the antebrachial fascia between the flexor carpi ulnaris and the finger
flexor tendons. The ulnar nerve is located ulnar and deep to the ulnar artery
(TECH FIG 2).
Ulnar Nerve Decompression
■ The ulnar nerve is carefully dissected from proximal to distal, through the
ulnar tunnel.
■ The volar carpal ligament and palmaris brevis (roof of the ulnar tunnel) are
incised, staying ulnar to the hook of the hamate, so as not to inadvertently

enter the carpal tunnel.
■ Within the ulnar tunnel, the ulnar nerve is gently retracted medially to
identify and decompress the deep motor branch.
■ To identify the deep motor branch, locate the oblique fibers of the proximal
edge of the hypothenar fascia. Immediately proximal to this leading edge, 1
to 2 mm of the deep motor branch is visible as it dives deep to the hypothenar
fascia to enter the pisohamate hiatus and curves around the hook of the
hamate.
■ A small blunt elevator may be placed deep to the proximal edge of
hypothenar fascia to protect the deep motor branch, and this fascia is then
released (TECH FIG 3A).
■ The deep motor branch is then followed around the hook of the hamate, and
all tendinous bands of the hypothenar musculature must also be divided
(TECH FIG 3B).
■ If the deep motor branch is compressed more distally in the palm, it may be
followed along the interosseous fascia (deep to the flexor tendons and
superficial palmar arch) to its terminus in the adductor pollicis.
TECH FIG 3 • A. A Freer elevator has been placed
beneath the leading edge of the hypothenar fascia. B.
The sensory branch and deep motor branch of the
ulnar nerve have been decompressed.
■ Within the canal, care must be taken to protect the small vessels running
with the motor branch.
■ After releasing the ulnar nerve and the deep motor branch, the floor of the
ulnar tunnel is evaluated for masses or anomalous muscles, which are then

excised. In the case of a ganglion cyst, the stalk of the cyst is identified and
ablated at its origin.
■ After the ulnar nerve and its distal branches have been decompressed, the
wound is thoroughly irrigated with sterile saline and the tourniquet deflated.
Meticulous hemostasis is achieved with bipolar electrocautery.
Wound Closure and Dressing
■ The incision is closed with 4-0 nylon suture in a horizontal or simple
interrupted fashion.
■ If local anesthetic, such as 0.25% bupivacaine, has not previously been
injection, it may be injected into the incision site at this time for
postoperative comfort.
■ A nonadherent dressing is applied directly to the wound, and a sterile, bulky
soft dressing is placed.
■ Typically, a splint is not needed, unless a ganglion cyst was excised or the
dissection was extensive.
PEARLS AND PITFALLS
Diagnosis
Evaluate for extrinsic sources of compression based on suspected
pathology.
■ Osseous pathology: radiographs, CT
■ Vascular pathology: Ultrasound, contrast arteriogram
■ Soft tissue mass: MRI
Incision
■ Fifteen percent of patients have a cutaneous branch of the ulnar
nerve in the distal aspect of this incision. Avoid injury to the nerve
here to prevent a painful neuroma.
Entering the
ulnar tunnel
■ Stay ulnar to the hook of the hamate to avoid entering the carpal
tunnel.
Identification
of the deep
motor branch
■ Identify the oblique fibers of the hypothenar fascia at the proximal
edge of the hypothenar muscles and carefully release these fibers
to expose and decompress the ulnar motor branch.
Release of
■ Ensure complete nerve decompression, including complete release

the deep
motor branch
of the tendinous bands of the hypothenar muscles.
Hemostasis
■ Preserve the small vessels running with the deep motor branch to
avoid having to cauterize vessels adjacent to the nerve.
POSTOPERATIVE CARE
■ Apply a soft bulky dressing to the wrist postoperatively, and active range of
motion can be initiated immediately to minimize scarring around the nerve.
■ The bulky surgical dressing is removed on postoperative day 1 or 2 and
replaced with a clean gauze dressing or bandage, if necessary.
■ Night splinting with the wrist in a neutral position may be used for 2 weeks for
patient comfort.
■ Strengthening exercises may be initiated at 4 to 6 weeks. Patients may
gradually increase activities as tolerated at this time.
OUTCOMES
■ There are limited data on the outcome of ulnar tunnel release and
decompression.
■ Murata et al. retrospectively reported their outcomes in 31 patients with ulnar
tunnel syndrome with a variety of causes treated with ulnar tunnel
decompression.7
■ The authors reported improvement in subjective symptoms and two-point
discrimination in all patients (from a preoperative mean of 7.0 and 6.9 mm in
the ring and small fingers, respectively, to 5.4 and 5.3 mm postoperatively),
although no statistical analysis was provided.
■ Five patients had persistent symptoms in the ring and/or small fingers.
COMPLICATIONS
■ There are few studies reporting the type and incidence of complications of
ulnar tunnel release.
■ Potential complications include the following:
■ Incomplete relief of symptoms (persistent numbness, weakness)
■ Iatrogenic injury to the ulnar nerve or artery branches, especially to the deep
motor branch as it enters the pisohamate hiatus
■ Hematoma resulting from injury to vascular plexus around the ulnar nerve
branches and failure to achieve hemostasis prior to wound closure

■ Wound infection
■ Wound dehiscence
■ Meticulous hemostasis, careful dissection, and knowledge of the ulnar nerve
and artery branching anatomy and its variations are helpful in avoiding
complications.
REFERENCES
1. Dupont C, Cloutier GE, Prevost Y, Dion MA. Ulnar tunnel syndrome at the
wrist. J Bone Joint Surg Am. 1965;47:757-761.
2. Maroukis BL, et al. Guyon canal: the evolution of clinical anatomy. J Hand
Surg [Am]. 2015;40(3):560-565.
3. Chen S, Tsai T. Ulnar tunnel syndrome. J Hand Surg [Am]. 2014;39(3):
571-579.
4. Murata K, Tamai M, Gupta A. Anatomic study of variations of hypothenar
muscles and arborization patterns of the ulnar nerve in the hand. J Hand Surg
[Am]. 2004;29(3):500-509.
5. Shea JD, McClain EJ. Ulnar-nerve compression syndromes at and below the
wrist. J Bone Joint Surg Am. 1969;51(6):1095-1103.
6. Gross MS, Gelberman RH. The anatomy of the distal ulnar tunnel. Clin
Orthop Relat Res. 1985;(196):238-247.
7. Murata K, Shih J, Tsai T. Cause of ulnar tunnel syndrome: a retrospective
study of 31 subjects. J Hand Surg [Am]. 2003;28(4):647-651.
8. Grundberg AB. Ulnar tunnel syndrome. J Hand Surg Eur Vol. 1984;9(1):72-
74.
9. Seror P. Electrophysiological pattern of 53 cases of ulnar nerve lesion at the
wrist. Clin Neurophysiol. 2013;43:95-103.
10. Earp BE, Floyd WE, Louis D, et al. Ulnar nerve entrapment at the wrist. J Am
Acad Orthop Surg. 2014;22(11):699-706.
11. Kowalska B, Sudoł-Szopińska I. Ultrasound assessment on selected
peripheral nerve pathologies. Part I: Entrapment neuropathies of the upper
limb—excluding carpal tunnel syndrome. J Ultrason. 2012;12(50):307-318.
12. Higgins JP, McClinton MA. Vascular insufficiency of the upper extremity. J
Hand Surg [Am]. 2010;35(9):1545-1553.
13. Yuen JC, Wright E, Johnson LA, Culp WC. Hypothenar hammer syndrome:
an update with algorithms for diagnosis and treatment. Ann Plast Surg.
2011;67(4):429-438.

28
CHAPTERCubital Tunnel Syndrome
Mary Claire Manske and Jason H. Ko
DEFINITION
■ Cubital tunnel syndrome is symptomatic ulnar nerve dysfunction resulting
from a combination of compression, traction, friction, and nerve instability at
or near the elbow.
■ The cubital tunnel is a fibro-osseous canal through which the ulnar nerve
passes at the level of the medial elbow and is thought to be the most common
site of nerve pathology.
ANATOMY
■ The ulnar nerve is composed of fibers from the C8 and T1 nerve roots,
although additional contributions from the C5, C6, C7, or T2 roots are
common.
■ It arises from the medial cord of the brachial plexus and enters the arm by
passing deep to the pectoralis major muscle, medial to the brachial artery.
■ At 8 to 10 cm proximal to the medial epicondyle, the nerve pierces the medial
intermuscular septum from anterior to posterior and descends through the arm
along the posterior aspect of the medial intermuscular septum.
■ At this location, there is often a thick fascial band (the internal brachial
ligament) spanning from the medial intermuscular septum to the medial head
of the triceps, commonly referred to as the arcade of Struthers (FIG 1).
■ The ulnar nerve travels posterior to the elbow via the cubital tunnel to enter the
anterior forearm. The cubital tunnel is a fibro-osseous space bordered by the
medial epicondyle anteriorly, the olecranon posteriorly, the oblique and
posterior bands of the ulnar collateral ligament medially (the “floor” of the
tunnel), and Osborne (or arcuate) ligament laterally (the “roof” of the tunnel).

Within the cubital tunnel, the ulnar nerve commonly provides articular
branches to the elbow and motor branches to the flexor carpi ulnaris (FCU)
(between 1 and 4 branches, arising from 4 cm proximal to the elbow to 10 cm
distal to the medial epicondyle). The ulnar nerve provides motor branches to
the ulnar two flexor digitorum profundi, which arise approximately 3 cm distal
to the medial epicondyle.
■ After passing though the cubital tunnel, the ulnar nerve travels deep to the
fibrous aponeurosis of the FCU to pass between the two heads of the FCU and
into the forearm along the undersurface of the FCU into the distal forearm.
FIG 1 Anatomy of the cubital tunnel.
PATHOGENESIS
■ Four pathogenic mechanisms have been implicated in cubital tunnel
syndrome: compression, traction, friction, and instability.
■ Compression: The ulnar nerve may be compressed anywhere along its
course, but the most common clinical sites of compression are the arcade of
Struthers, the median intermuscular septum, medial epicondyle, anconeus
epitrochlearis (if present), the cubital tunnel, and the deep flexor-pronator
aponeurosis

• The cubital tunnel is round and spacious with elbow extension but narrows
and becomes elliptical with the elbow flexed, decreasing the volume of the
tunnel by 55%.1,2
• Decreased cubital tunnel volume results in a four- to fivefold increase in
extra- and intraneural pressure of the ulnar nerve.3
• Both blood flow and axonal transport are impaired with external nerve
compression; as pressure increases, the nerve tissue thickens and nerve
conduction is impaired.1,4–6
• Less common sources of ulnar nerve compression include soft tissue masses
(eg, ganglia, tumors), hypertrophic synovium, cubitus valgus, and
osteophytes.
■ Traction7: The course of the ulnar nerve around the medial epicondyle places
tension on the ulnar nerve where it crosses the elbow and enters the forearm.
• The ulnar nerve elongates by 4 to 8 mm when the elbow is flexed. This
stretch is further increased with the shoulder abducted and the wrist
extended.
• Stretch of the ulnar nerve results in both reduced blood flow and impaired
conduction.
■ Friction: Although the nerve naturally experiences some traction and
excursion with elbow motion, repetitive elbow motion or subluxation of the
nerve can cause traction neuritis, inflammation, and endoneurial edema,
decreasing the nerve’s ability to glide smoothly.1
■ Instability: Subluxation of the ulnar nerve out of the cubital tunnel or over the
medial epicondyle may result in elbow pain, a snapping sensation, numbness,
or intrinsic motor weakness.
PATIENT HISTORY AND PHYSICAL FINDINGS
■ Sensory
■ Numbness and paresthesia in the ring and small finger
■ Dorsoulnar hand numbness helps differentiate cubital tunnel
syndrome/proximal ulnar nerve compression from ulnar tunnel syndrome at
the wrist.
■ Presence of numbness or paresthesia in the medial forearm distinguishes C8
radiculopathy from cubital tunnel syndrome.
■ Depending on severity and chronicity, numbness may be intermittent or
constant.

■ Motor
■ Hand clumsiness, loss of dexterity
■ Weakness of pinch and grip
■ Inability to adduct or abduct the fingers
■ Intrinsic muscle atrophy, clawing of the ulnar two digits, with severe ulnar
nerve compression
■ Pain in the medial elbow or forearm
■ Physical exam
■ Inspection: Intrinsic muscle atrophy/wasting or clawing; compare to
contralateral upper extremity
■ Palpation: Medial elbow tenderness; subluxation or perching of ulnar nerve
over medial epicondyle with elbow flexion and extension
■ Sensory exam: Decreased sensation to light touch in small and ulnar ring
finger; decreased sensation over dorsoulnar hand. Semmes-Weinstein
monofilament or 2-point discrimination test
■ Motor exam: Intrinsic motor weakness indicates compromise of ulnar motor
nerve fibers. Assess by testing index finger abduction (first dorsal
interosseous muscle) or performing the cross-finger test (asking the patient to
cross the middle finger over the index finger to assess the first volar and
second dorsal interossei).
■ Additional motor tests:
• Froment sign: Positive test when patient is unable to use adductor pollicis
for lateral pinch. Instead, patients compensate with the flexor pollicis
longus, which is innervated by the median nerve, to flex the thumb
interphalangeal joint. Positive test indicates dysfunction of ulnar nerve
motor fibers, although it does not localize the site of the lesion.
• Jeanne test: Test is positive, indicating ulnar motor neuropathy, when the
patient hyperextends the metacarpophalangeal joint to compensate for weak
adductor pollicis during lateral pinch.
• Wartenberg sign: Inability to adduct the small finger secondary to paralysis
of the third palmar interosseous muscle. Positive test indicates an ulnar
motor neuropathy.
■ Provocative tests:
• Tinel sign at elbow: Percussion over ulnar nerve at medial epicondyle
reproduces paresthesias in ring and small finger in patients with cubital
tunnel syndrome.

• Elbow flexion test: Elbow flexion, forearm supination, and wrist extension
for 3 minutes elicit paresthesia in ulnar nerve distribution in patients with
cubital tunnel syndrome.
• Pressure provocation test: Manual pressure over ulnar nerve in cubital
tunnel elicits ulnar nerve paresthesia.
• Scratch collapse test8: Examiner scratches the skin over the compromised
ulnar nerve while the patient performs sustained resisted shoulder external
rotation with the arms adducted and the elbow flexed. A positive test is
indicated by brief loss of ability to maintain resisted external resistance (ie,
collapse).
■ Must rule out alternative sites of nerve compression:
• Guyon canal (tenderness over hook or hamate or pisiform)
• Cervical radiculopathy (neck pain, Spurling test, more proximal motor and
sensory involvement)
• Carpal tunnel syndrome (thenar atrophy or weakness; sensory disturbance in
radial-sided digits; Tinel, Phalen, Durkan test positive over carpal tunnel)
• Lower brachial plexus lesion
• Thoracic outlet syndrome (Roos test, Adson maneuver)
IMAGING
■ Electrodiagnostic testing is useful to confirm a diagnosis of ulnar nerve
dysfunction, localize the site of compression, and quantify the severity.
■ The following criteria are used to diagnose cubital tunnel syndrome
electodiagnostically9:
• Absolute conduction velocity less than 50 m/s
• Decreased conduction velocity of greater than 10 m/s across the elbow
• Decreased amplitude of at least 20%
• Absent sensory response
• Evidence of motor atrophy
■ X-rays should be obtained selectively when there is clinical concern for an
osseous abnormality causing ulnar nerve compression.
■ Elbow radiographs are useful in suspected cases of elbow osteoarthritis,
rheumatoid arthritis, trauma, or cubitus valgus deformity
■ Chest radiographs may identify a cervical rib causing thoracic outlet
syndrome or a Pancoast tumor (suspected in patients with ulnar nerve

symptoms, shoulder pain, and history of smoking)
■ On ultrasound, patients with cubital tunnel syndrome have an increased cross-
sectional area of the ulnar nerve compared to patients without cubital tunnel
syndrome.
■ Ulnar nerve cross-sectional area of 0.10 cm2 or higher on ultrasound of the
ulnar nerve within 4 cm of the medial epicondyle is 93% sensitive and 98%
specific for cubital tunnel syndrome.10
■ Morphologic and signal changes in the ulnar nerve have been observed on
MRI in cubital tunnel syndrome.
■ MRI has been reported to be both sensitive and specific in diagnosing cubital
tunnel syndrome but is not routinely used.11,12
DIFFERENTIAL DIAGNOSIS
■ Cervical radiculopathy
■ Ulnar tunnel syndrome
■ Lower brachial plexopathy
■ Motor neuron disease (eg, amyotrophic lateral sclerosis, Charcot-Marie-Tooth)
■ Guillain-Barré syndrome
■ Diabetic neuropathy
NONOPERATIVE MANAGEMENT
■ Initial treatment of cubital tunnel syndrome in patients without constant
numbness or motor atrophy is nonoperative.
■ Nonoperative treatment consists of patient education, activity modification
(discontinue triceps exercises, pad medial elbow when resting on a hard
surface), postural modification (avoidance of prolonged elbow flexion or
resting medial elbow on a hard surface), night splinting (to prevent the elbow
from flexing beyond 40 to 50 degrees during sleep), and/or nerve gliding
exercises.13
■ The recommended duration of nonoperative treatment is 3 months in patients
with mild or moderate symptoms and 6 weeks in patients with severe
symptoms.
■ A comprehensive course of nonoperative intervention has been shown to
resolve symptoms in 42% of patients with mild cubital tunnel syndrome, 34%
of patients with moderate symptoms, and 20% of patients with severe
symptoms.14

■ Steroid injection is not recommended, as this has not been shown to provide
any benefit in the treatment of cubital tunnel syndrome and presents a risk of
nerve injury.15
SURGICAL MANAGEMENT
Preoperative Planning
■ Indications for operative intervention include failure of nonoperative
intervention, muscle atrophy or weakness, loss of two-point sensibility in the
ulnar nerve distribution, or severe electrodiagnostic changes involving the
ulnar nerve in the proximity of the elbow.16
■ Assess stability of ulnar nerve preoperatively, as this guides surgical
intervention; patients with ulnar nerve instability are not candidates for in situ
decompression.
Positioning
■ Patients are positioned supine on a well-padded operating table or stretcher.
■ The operative extremity is positioned on a hand table. The patient’s shoulder
should be placed as close to the hand table as possible.
■ We recommend against the use of a nonsterile tourniquet, as this may encroach
upon the surgical field when anterior transposition is required.
Approach
■ A direct approach to the ulnar nerve on the medial side of the elbow is utilized.
T E C H N I Q U E S
■ In Situ Cubital Tunnel Decompression
■ After the operative limb is prepped and draped, a surgical marking pen is
used to mark the medial epicondyle, olecranon, and medial intermuscular
septum. If a tourniquet is used, a sterile tourniquet should be applied to the
upper extremity as proximally as possible. An alternative to the tourniquet is
to inject the planned incision subcutaneously with local anesthetic containing
epinephrine.
■ If a tourniquet is used, the extremity is exsanguinated with an elastic

bandage and the tourniquet elevated to 250 mm Hg.
■ A 3- to 5-cm incision along the course of the ulnar nerve midway between
the medial epicondyle and olecranon is made with a scalpel just through the
dermis (TECH FIG 1A).
■ The subcutaneous tissues are dissected with tenotomy scissors in line with
the skin incision down to the level of the deep brachial fascia proximally and
the antebrachial fascia distally.
■ Care must be taken to identify and protect branches of the medial
antebrachial cutaneous (MABC) nerve, which lie within the subcutaneous fat
just over the muscle fascia from 6 cm proximal to 6 cm distal to the medial
epicondyle.17
■ The ulnar nerve is identified proximally, deep to the deep brachial fascia and
posterior to the medial intermuscular septum.
■ The fascia overlying the ulnar nerve proximally is released, beginning 8 cm
proximal to the medial epicondyle (TECH FIG 1B).
■ The nerve is followed distally, releasing the overlying fascia bands to
decompress the nerve. Specific structures released include the arcade of
Struthers, deep brachial fascia, Osborne ligament, and deep flexor-pronator
aponeurosis. Care is taken not to dissect around the ulnar nerve
circumferentially.
■ The deep flexor-pronator aponeurosis should be released for a minimum of 4
cm distal to where the ulnar nerve enters the forearm between the two heads
to the flexor carpi ulnaris (FCU).
■ With blunt digital dissection, a finger should be passed along the course of
the ulnar nerve as it passes deep to the flexor-pronator mass to ensure that all
constricting bands of the deep flexor-pronator aponeurosis have been
released (TECH FIG 1C).
■ Following decompression, the ulnar nerve is not displaced from its bed, nor
is a neurolysis performed.
■ The elbow is taken through its full arc of motion, and the stability of the
ulnar nerve is assessed.
■ If the nerve subluxates or perches on the medial epicondyle, an anterior
transposition should be performed.
■ In addition, evaluation for any residual points of ulnar nerve compression
should be performed. In particular, the medial intermuscular septum should
be examined to ensure the nerve does not kink on the septum with elbow

range of motion; if it does, that section of the medial intermuscular septum
should be excised, with care to cauterize or ligate the branches of the
profunda brachii artery that cross the septum.
■ If a tourniquet has been used, it is released and meticulous hemostasis
obtained with bipolar electrocautery.
■ The skin may be injected with local anesthetic if this was not performed
previously.
■ The dermis is closed with a 3-0 absorbable suture in a buried interrupted
fashion. The skin is closed with an absorbable monofilament suture.
■ A bulky soft dressing is applied and elbow range of motion is initiated
within the first few days postoperatively. Patients are permitted to perform
light activities of daily living (eg, dressing, self-care, feeding) but no heavy
lifting or sports for 2 weeks.
TECH FIG 1• A. A 3- to 5-cm incision is made along
the course of the ulnar nerve centered between the
medial epicondyle and the olecranon. B. The fascia
overlying the ulnar nerve proximally is released,

beginning 8 cm proximal to the medial epicondyle (red
arrow) and proceeding distally. C. The deep
aponeurosis of the flexor-pronator mass is released
over the ulnar nerve, as it dives between the two
heads of the FCU (red arrow). (Proximal is to the left
and distal to the right in all parts.)
■ Transposition of the Ulnar Nerve
■ Typically, in situ decompression of the ulnar nerve is the first-line treatment
for cubital tunnel syndrome.
■ However, if there is subluxation of the ulnar nerve, subcutaneous or
submuscular transposition of the ulnar nerve may be indicated at the time of
decompression.
■ For the treatment of recurrent cubital tunnel syndrome, subcutaneous or
submuscular transposition of the ulnar nerve is the treatment of choice.
■ Submuscular transpositions are usually reserved for patients who have
failed previous subcutaneous transposition.
■ The operative extremity is prepped and draped in the usual sterile fashion.
■ A sterile tourniquet may be applied to the operative extremity as proximally
as possible. An alternative to the tourniquet is to inject the planned incision
with local anesthetic containing epinephrine.
■ A surgical marking pen is used to mark the anatomic landmarks: medial
epicondyle, olecranon, and medial intermuscular septum.
■ If a tourniquet is used, the limb is exsanguinated with an elastic bandage and
the tourniquet is elevated to 250 mm Hg.
■ A 10-cm incision is made over the course of the ulnar nerve centered
between the medial epicondyle and olecranon. Proximal to the medial
epicondyle, the incision is made along the palpable course of the medial
intermuscular septum. Distally, the incision follows the course of the ulnar
nerve as it travels between the two heads of the FCU.
■ An ulnar nerve decompression is performed as described above for in situ
ulnar nerve decompression.
■ A half-inch latex-free Penrose drain is placed around the nerve to allow it to
be manipulated atraumatically. The ends of the Penrose drain are sutured

together with 4-0 nylon suture.
■ We recommend against using a vessel loop around the nerve or placing a
hemostat clamp on the Penrose drain, as both of these may cause
unnecessary trauma to the nerve and increase the likelihood of a
neurapraxic injury.
■ Using tenotomy scissors, the ulnar nerve is circumferentially dissected to
free it from surrounding tissues and the bed in which it rests.
■ The longitudinally running superior ulnar collateral vessels that accompany
the nerve should remain with the nerve as distally as possible, but it is
necessary to ligate the vessels as they penetrate the FCU muscle belly.
■ To avoid compression of the nerve by the medial intermuscular septum after
it is transposed, the distal segment of the medial intermuscular septum should
be excised from its insertion on the humerus. Branches of the profunda
brachii artery cross the septum, and these need to be ligated or cauterized.
Submuscular Transposition of the Ulnar Nerve
■ The subcutaneous tissues are elevated off the flexor-pronator fascia.
■ A step-cut is made in the flexor-pronator fascia, such that the anterior
musculofascial flap is distally based and the posterior fascial flap is
proximally based on the medial epicondyle.
■ The flaps should be approximately 3 cm in length to avoid compression on
the ulnar nerve when the flaps are coapted (TECH FIG 2A).
■ The posterior fascial flap is carefully and sharply elevated from the
underlying muscle with a scalpel or tenotomy scissors, with care not to
disrupt the base of the fascial flap.
■ The anterior musculofascial flap is elevated full-thickness, including the
superficial head of pronator teres and the common flexor tendon, using
monopolar cautery.
■ This allows the anterior musculofascial unit to slide distally, creating a
trough for the ulnar nerve, once transposed.
■ Within the muscle of the flexor-pronator mass, there are stout fascial septa
that need to be excised to prevent them from compressing the ulnar nerve
when it is transposed.
■ Care must be taken to identify FCU motor branches of the ulnar nerve that
may cross these septa.
■ Monopolar electrocautery is used to dissect through the flexor-pronator

muscle in line with the elevated posterior flap to provide a deep muscular bed
in which the ulnar nerve may rest.
■ Using the Penrose drain, the nerve is gently transposed anteriorly and laid in
the previously created muscle trough (TECH FIG 2B).
■ If the nerve is tethered by motor branches to the FCU, these branches may
be separated from the main nerve for up to 6 to 8 cm to allow greater
excursion of the ulnar nerve as it is transposed.
■ The entire course of the ulnar nerve is examined to ensure there are no points
of nerve compression or crimping after it has been transposed.
■ In particular, ensure that all soft tissues proximally have been released, that
the nerve is not kinked as it crosses the medial intermuscular septum, and
that it is not bending over the superficial or deep flexor-pronator fascia
distally.
■ Stout, nonabsorbable braided suture is used to coapt the ends of the flaps that
were raised from the flexor-pronator fascia, effectively lengthening the
musculofascial unit.
■ Figure-of-eight or horizontal mattress suture can be used (TECH FIG 2C).
■ The elbow is taken through a range of motion from full extension to full
flexion.
■ The nerve is inspected to ensure it does not fall out of its bed in the muscle
or subluxate posterior to the medial epicondyle.
■ Any dynamic points of compression are also identified and released as
necessary.
■ If a tourniquet is used, it is now deflated. Meticulous hemostasis is obtained
with electrocautery.

TECH FIG 2• A. A step-cut is made in the flexor-
pronator fascia to create an anterior distally based
myofascial flap and a posterior proximally based
fascial flap. White arrows indicate medial antebrachial
cutaneous nerve. B. Full-thickness myofascial flaps
are elevated to create a trough in the muscle bed into
which the ulnar nerve is transposed. C. The ends of
the fascial flaps are sutured together to prevent
posterior subluxation of the ulnar nerve and effectively
lengthening the musculofascial unit. (Distal is to the
left and proximal to the right in all parts.)
■ The wound is thoroughly irrigated with normal saline.
■ The wound is closed with deep dermal buried interrupted sutures using an
absorbable suture material. The skin is closed with a running subcuticular
absorbable monofilament suture or a nonabsorbable monofilament in a
simple or horizontal mattress fashion.
■ A sterile soft dressing is applied to the wound, followed by either a soft

compression dressing or a posterior slab long-arm plaster splint, which
remains in place for 2 weeks.
■ It is important for the patient to be able to perform gentle active range of
motion of the elbow in the immediate postoperative period.
Anterior Subcutaneous Transposition of the Ulnar Nerve
■ The subcutaneous tissues are elevated off the flexor-pronator fascia.
■ An anteriorly based flap of flexor-pronator fascia is sharply elevated from
the medial epicondyle and underlying musculature with a scalpel blade or
tenotomy scissors.
■ The fascial flap should be approximately 3 cm in length to avoid
compression of the ulnar nerve (TECH FIG 3A,B).
■ Using the Penrose drain, the nerve is gently transposed anteriorly and
positioned superficial to the fascial flap (TECH FIG 3C).
■ If the nerve is tethered by motor branches to the FCU, these branches may
be separated from the main nerve for up to 6 to 8 cm to allow greater
excursion of the ulnar nerve as it is transposed.
■ The entire course of the ulnar nerve is examined to ensure there are no points
of nerve compression or crimping after it has been transposed. In particular,
ensure that all soft tissues surrounding the nerve proximally have been
released, that the nerve is not kinked as it crosses the medial intermuscular
septum, and that the nerve is not compressed by the flap in its transposed
position.
■ The fascial flap is approximated to the deep dermis on the underside of the
anterior skin flap, and that point on the superficial surface of the skin can be
marked with a marking pen (TECH FIG 3D; VIDEO 1).
■ Stout, nonabsorbable braided suture is used to suture the free end of the
fascial flap to the deep dermis on the underside of the anterior skin flap.
Figure-of-eight or horizontal mattress suture may be used.
■ The flap is approximated quite anteriorly so that when the anterior skin
flap is then brought down for closure, the fascial flap acts as a “hammock”
for the ulnar nerve, keeping it anterior to the medial epicondyle (TECH
FIG 3E).

Ulnar nerve B Ulnar nerve E

TECH FIG 3• A. An anteriorly based flap of flexor-
pronator fascia is designed to form a sling for the
transposed ulnar nerve. B. The fascial flap then
elevated from the medial epicondyle and underlying
musculature. C. The ulnar nerve is transposed
anteriorly over the fascial flap. D. The fascial flap is
sutured to the dermis of the anterior skin flap to
function as a “hammock” for the transposed ulnar
nerve to prevent posterior subluxation. E. The nerve is
evaluated throughout the full range of motion of the
elbow to ensure that the nerve does not kink,
subluxate, or become compressed in its transposed
position. (Distal is to the left and proximal to the right
in all parts.)
■ The elbow is taken through a range of motion from full extension to full
flexion.
■ The nerve is inspected to ensure it does not fall out of its bed in the muscle
or subluxate posterior to the medial epicondyle.
■ Any dynamic points of compression are also identified and released as
necessary (Video 2).
■ If a tourniquet is used, it is now deflated. Meticulous hemostasis is obtained
with electrocautery.
■ The operative field is thoroughly irrigated with normal saline.
■ The incision is closed with deep dermal, buried, interrupted sutures using an
absorbable suture material.
■ The skin is closed with a running subcuticular absorbable monofilament
suture or a nonabsorbable monofilament in a simple or horizontal mattress
fashion.
■ If an absorbable subcuticular suture is used, Steri-Strips are applied to the
incision.
■ A sterile bulky soft dressing is applied to the incision, which remains in
place for 2 days.
■ After postoperative day 2, it is important that the patient continue to use a

compression dressing to minimize postoperative edema.
■ Patients are instructed that they may gently move their elbow and use the
extremity for activities of daily living.
PEARLS AND PITFALLS
Superficial
dissection
■ Care should be taken to preserve branches of the medial
antebrachial cutaneous nerve to avoid causing a painful neuroma.
These branches cross the medial arm from 6 cm proximal to 6 cm
distal to the medial epicondyle.
Deep
dissection
■ A Penrose drain is loosely looped around the ulnar nerve to
manipulate it atraumatically during dissection and transposition.
Hemostasis
■ Meticulous hemostasis must be obtained to prevent a hematoma,
which could compress the ulnar nerve or lead to wound dehiscence.
Iatrogenic
compression
■ Secondary points of compression may be introduced after ulnar
nerve transposition if care is not taken to release them; in particular,
the medial intermuscular septum, the deep septa of the flexor-
pronator musculature (with submuscular transposition), and the
fascial flaps holding the nerve transposed should be inspected to
ensure no compression is present.
Nerve
stability
■ Inspect the position of the ulnar nerve throughout the full range of
motion of the elbow to ensure the nerve does not rest on or
subluxate posterior to the medial epicondyle.
POSTOPERATIVE CARE
■ In situ decompression or subcutaneous ulnar nerve transposition
■ Patients are placed in a bulky soft dressing, which may be removed on
postoperative day 2. They may begin showering at that point, but it is
important to continue the use of a compression wrap to minimize
postoperative edema.
■ Patients may move the operative extremity and perform activities of daily
living postoperatively. Heavier activities (ie, more than “coffee cup” weight
bearing) are prohibited. Patients may move the elbow and forearm as pain
permits. Patients are encouraged to move their wrist, hand, and digits to

prevent postoperative edema and stiffness.
■ Submuscular transposition
■ The use of a bulky soft dressing vs a long-arm splint is at the discretion of the
surgeon.
■ It is important for gentle range of motion of the elbow to begin immediately
in the postoperative period to minimize scarring along the ulnar nerve.
■ If a long-arm splint is used, it remains in place for 2 week postoperatively.
Patients are encouraged to move and use their digits while the splint is in
place.
■ If a soft dressing is used, it should remain in place for 2 weeks.
■ When the incision is well healed (usually around 2 weeks postoperatively),
sutures may be removed if nonabsorbable suture were used. Patients whose
incisions are closed with subcuticular absorbable sutures and Steri-Strips are
instructed that the Steri-Strips will fall off on their own.
■ All patients may allow the incision to get wet in the shower but are restricted
from immersing the incision in baths and pools for another week.
■ Patients may engage in unrestricted activities as tolerated at 2 weeks
postoperatively as long as the incision is well healed.
OUTCOMES
■ In situ decompression, subcutaneous transposition and submuscular
transposition have all been shown to be effective in the treatment of cubital
tunnel syndrome.
■ Most patients experience objective and subjective improvement in sensation,
strength, and pain, although persistent subjective sensory abnormalities are
common, regardless of surgical technique.
■ Patients express high satisfaction with the outcome of surgical intervention
with all procedures.
■ Multiple meta-analyses have demonstrated no difference in outcome in terms
of clinical outcomes or conduction velocities.
COMPLICATIONS
■ New elbow pain
■ Scar tenderness
■ Medial elbow and forearm numbness
■ Hematoma
■ Infection

■ Persistent or recurrent symptoms
■ The rate of revision surgery following in situ decompression is reported
between 3% and 19%.18,19
REFERENCES
1. Szabo RM, Kwak C. Natural history and conservative management of cubital
tunnel syndrome. Hand Clin. 2007;23;311-318.
2. Apfelberg DB, Larson SJ. Dynamic anatomy of the ulnar nerve at the elbow.
Plast Reconstr Surg. 1973;51(1);79-81.
3. Gelberman RH, Yamaguchi K, Hollstien SB, et al. Changes in interstitial
pressure and cross-sectional area of the cubital tunnel and of the ulnar nerve
with flexion of the elbow: an experimental study in human cadavers. J Bone
Joint Surg Am. 1998;80(4):492-501.
4. Aziz W, Firrell JC, Ogden L, et al. Blood flow in a chronic entrapment
neuropathy model in the rabbit sciatic nerve. J Reconstr Microsurg.
1999;15(1);47-53.
5. Dahlin LB, Rydevik B, McLean WG, et al. Changes in fast axonal transport
during experimental nerve compression at low pressures. Exp Neurol.
1984;84(1);29-36.
6. Lundborg G, Dahlin LB. The pathophysiology of nerve compression. Hand
Clin. 1992;8(2);215-227.
7. Wojewnik B, Bindra R. Cubital tunnel syndrome: review of current literature
on causes, diagnosis and treatment. J Hand Microsurg. 2009;1(2);76-81.
8. Cheng CJ, Mackinnon-Patterson B, Beck JL, Mackinnon SE. Scratch collapse
test for evaluation of carpal and cubital tunnel syndrome. J Hand Surg [Am].
2008;33(9);1518-1524.
9. American Association of Electrodiagnostic Medicine, American Academy of
Neurology, American Academy of Physical Medicine and Rehabilitation.
Practice parameter for electrodiagnostic studies in ulnar neuropathy at the
elbow: summary statement. Muscle Nerve. 1999;22(3);408-411.
10. Wiesler ER, Chloros GD, Cartwright MS, et al. Ultrasound in the diagnosis of
ulnar neuropathy at the cubital tunnel. J Hand Surg [Am]. 2006;31(7):1088-
1093.
11. Patel VV, Heidenreich FP Jr, Bindra RR, et al. Morphological changes in the
ulnar nerve at the elbow with flexion and extension: a magnetic resonance
imaging study with 3-dimensional reconstruction. J Shoulder Elbow Surg.
1998;7(4);368-374.

12. Britz GW, Haynor DR, Kuntz C, et al. Ulnar nerve entrapment at the elbow:
correlation of magnetic resonance imaging, clinical, electrodiagnostic, and
intraoperative findings. Neurosurgery. 1996;38(3);458-465.
13. Shah CM, Calfee RP, Gelberman RH, Goldfarb CA. Outcomes of rigid night
splinting and activity modification in the treatment of cubital tunnel syndrome.
J Hand Surg [Am]. 2013;38(6);1125-1130.
14. Dellon AL, Hament W, Gittelshon A. Nonoperative management of cubital
tunnel syndrome: an 8 year prospective study. Neurology. 1993;43(9);1673-
1677.
15. Hong CZ, Long HA, Kanakamedala RV, et al. Splinting and local steroid
injection for the treatment of ulnar neuropathy at the elbow: clinical and
electrophysiological evaluation. Arch Phys Med Rehabil. 1996;77(6);573-577.
16. Boone S, Gelberman RH, Calfee RP. The management of cubital tunnel
syndrome. J Hand Surg [Am]. 2015;40(9);1897-1904.
17. Dellon AL, Mackinnon SE. Injury to the medial antebrachial cutaneous nerve
during cubital tunnel surgery. J Hand Surg Br. 1985;10:33-36.
18. Krogue JD, Aleem AW, Osei DA, et al. Predictors of surgical revision after in
situ decompression of the ulnar nerve. J Shoulder Elbow Surg. 2015;24;634-
639.
19. Gaspar MP, Kane PM, Putthiwara D, et al. Predicting revision following in
situ ulnar nerve decompression for patients with idiopathic cubital tunnel
syndrome. J Hand Surg [Am]. 2016;41(3);427-435.
SUGGESTED READINGS
Biggs M, Curtis JA. Randomized, prospective study comparing ulnar neurolysis
in situ with submuscular transposition. Neurosurgery. 2006; 58(2):296-304.
Watts AC, Bain GI. Patient-rated outcome of ulnar nerve decompression: a
comparison of endoscopic and open in situ decompression. J Hand Surg Am.
2009;34A:1492-1498.

29
CHAPTER
Radial Tunnel
Decompression
Joseph Pirolo and Jason H. Ko
DEFINITION
■ Radial tunnel syndrome (RTS) is a pain syndrome caused by compression of
the radial nerve and its branches in the proximal forearm.
■ Generally characterized by lack of muscle weakness and electrodiagnostic
findings
ANATOMY
■ The radial tunnel is the space through which the radial nerve and its branches
pass in the proximal forearm.
■ The tunnel extends approximately 5 cm from the radiocapitellar joint to the
proximal edge of the supinator muscle.1–3
■ Tunnel boundaries1–3
■ Radial: brachioradialis (BR), extensor carpi radialis longus (ECRL), and
extensor carpi radialis brevis (ECRB)
■ Ulnar: brachialis, biceps tendon
■ Floor: radiocapitellar joint capsule, supinator
■ Radial nerve branches and sites of compression
■ The radial nerve branches proximal to the superior border of the supinator
and forms the radial sensory nerve (RSN) and the posterior interosseous nerve
(PIN).
■ The PIN has multiple potential entrapment sites2,4–6
• Arcade of Frohse (proximal tendinous edge of supinator)
• Proximal edge of ECRB
• Radial recurrent vessels (leash of Henry)

• Radiocapitellar joint capsule and osteophytes
• Supinator distal edge
PATHOGENESIS
■ Compression of the radial nerve, PIN, or SBRN by one or more anatomic
structures at the radial tunnel, which can be secondary to aberrant anatomy,
mass effect, trauma, arthrosis, or idiopathic
■ Pathogenesis and pathophysiology of RTS is poorly understood and
controversial owing to the fact that it is a compressive neuropathic pain
syndrome with no reliably identifiable motor, radiologic, or electrodiagnostic
findings.
■ Although the PIN is a motor nerve, it does contain group IIA and IV fibers,
which have been associated with temperature and nociception.7 Given that
these are not evaluated in standard electrodiagnostic testing, one possibility is
that they may contribute to the pain syndrome even though nerve conduction
velocities remain normal.
■ Occupations that require heavy tool use in full elbow extension have been
identified as a risk factor for development of RTS.8,9
PATIENT HISTORY AND PHYSICAL FINDINGS
■ History
■ Patients complain of pain and fatigue in the proximal dorsal forearm.
■ Pain may radiate and can be aggravated by activities loading a rotated
forearm or extended wrist.1
■ Muscle weakness is either absent or secondary to pain.10
■ Sensory disturbances are usually absent.
■ Physical exam
■ The primary finding is localized tenderness over the radial nerve 5 cm distal
to the lateral epicondyle.11
■ Provocative tests include pain with resisted forearm supination and/or
resisted active extension of the middle finger.10
■ The “rule of nines” test has been proposed to help localize tenderness to the
radial tunnel and help differentiate from other nearby sources of pain. In this
test, the proximal volar forearm is divided into nine squares and tenderness
with the lateral column marking out the radial tunnel.12
■ Examination must take into consideration several other possible sources of
proximal forearm pain, especially lateral epicondylar tendinopathy, in which