ULNAR NERVE ENTRAPMENT
CUBITAL TUNNEL SYNDROME
Epidemiology
 Elbow most common site for ulnar nerve entrapment
 2nd most common compressive neuropathy after carpal tunnel
 Bilateral in 12%
 F>M 3-8:1
 medial aspect of the elbow has 2-19 times more fat content in women than in
men
Aetiology
1. Constricting fascial bands
2. Subluxation of ulnar nerve over epicondyle
 friction generated with repeated subluxation may cause inflammation within
the nerve, and in the subluxed position, the nerve may be more susceptible to
inadvertent trauma.
 Present in 16% of normal population
3. Cubitus valgus
4. Bony spurs
5. heterotrophic ossification – secondary to burns, head injury
6. Aberrant muscle - anconeus epitrochlears( 9-30% of patients undergoing surgery
for cubital tunnel; bilateral in 12%). This muscle arises from the medial humeral
condyle and inserts on the olecranon, crossing superficially to the ulnar nerve,
where it may cause compression.
7. Synovitis
8. Tumors
9. Ganglions
10. Direct compression


Repetitive work related activities have been shown to aggravate condition but no
evidence to support a causal role.
Proximal compression of a nerve trunk, such as occurs with cervical radiculopathy
or thoracic outlet syndrome, may lead to increased vulnerability to compression of
the nerve in a distal segment. This double crush syndrome can affect the ulnar
nerve and results from disruption in normal axonal transport.
Pathophysiology
1. Compression
 As the elbow moves from extension to flexion, the distance between the
medial epicondyle and the olecranon increases 5 mm for every 45 degrees
of elbow flexion.
 Shape of the cubital tunnel changes from a round to an oval tunnel with a
2.5-mm loss of height

Loss in height with flexion results in a 55% volume decrease in the canal,
which further results in the mean ulnar intraneural pressure increasing
from 7 mm Hg to 14 mm Hg.
 A combination of shoulder abduction, elbow flexion, and wrist extension
results in the greatest increase in cubital tunnel pressures, with an increase
in intraneural pressure 6 times normal.
2. Traction
 ulnar nerve elongates 5-8 mm with elbow flexion. If it doesn’t elongate
because of inflammation, cause increase in intraneural pressure
3. Excursion
 With full range of motion (ROM) of the elbow, the ulnar nerve undergoes
10mmm of longitudinal excursion proximal to the medial epicondyle and
5mm of excursion distal to the epicondyle.
Anatomy
Course of Ulnar nerve at arm
 Medial cord (C7-T1)
 Starts posterior to the vessels, piercing medial intermuscular septum
 No branches in arm
 First branch is to FCU
Sites of entrapment at elbow (Posner 1998)
1. Arcade of Struthers
a. musculofascial band about 8 cm proximal to the medial epicondyle
b. formed by attachments of
i. internal brachial ligament (between insertion of
coracobrachialis and intermuscular septum)
ii. fascia and superficial fibers of medial head of triceps laterally
iii. intermuscular septum anteriorly
c. present in 70% of specimens
d. beware posterior branch of medial cutaneous nerve of forearm –
crosses over nerve between 6cm proximal to 4cm distal to epicondyle
(90% at or proximal to epicondyle)
2. medial epicondyle and epicondylar groove
a. from previous fractures (tardy ulnar palsy), arthritic spurs
b. A congenitally shallow groove or a torn fibrous roof can allow the
nerve to chronically subluxate or dislocate, causing neuritis and palsy.
3. Cubital tunnel
a. Fibrous band, 4mm wide – extends from medial epicondyle to tip of
olecranon (remnant of the anconeus epitrochlear muscle.)
b. Tight in elbow flexion
c. Roof = arcuate ligament of Osborne, floor = elbow capsule and
medial collateral ligament (posterior and transverse component)
4. Flexor-pronator mass
a. As the nerve exits the flexor carpi ulnaris, it perforates a fascial layer
between the flexor digitorum superficialis and the flexor digitorum
profundus 3cm distal to the cubital tunnel and 5cm distal to the
medial epicondyle
Blood supply of ulnar nerve
 Extrinsic blood supply
 segmental and involves 3 vessels.
1. superior ulnar collateral artery – branch from brachial 16cm above elbow
2. posterior ulnar recurrent artery – branch from ulnar artery 7cm below
elbow
3. the inferior ulnar collateral artery, (minor)
 Typically, the inferior ulnar collateral artery, and often the posterior ulnar
recurrent artery, is sacrificed with anterior transposition.
 At the level of the medial epicondyle, the inferior ulnar collateral artery is the
sole blood supply to the ulnar nerve.
 In an anatomic study, no identifiable anastomosis was found between the
superior ulnar collateral artery and the posterior ulnar recurrent arteries in 20
of 22 arms. Instead, communication between the 2 arteries occurred through
proximal and distal extensions of the inferior ulnar collateral artery.
 Intrinsic
 An interconnecting network of vessels that run along the fascicular branches
and along each fascicle of the ulnar nerve.
 Shown to be significant, allowing safe proximal and distal dissection over a
long distance
Clinical
History
 Onset of symptoms insidious, average duration of symptoms 6 months to 1 year
 Sensory
 numbness ulnar one and a half fingers
 numb dorsoulnar aspect
 Motor
 weakness of grip, pinch strength and fine dexterity
 activities when torque applied to tool
 Symptoms worse with elbow flexion or resting elbow on table
Examination
 Start at neck
 Spurling’s test for cervical root compression
 Axial compression of the head with slight extension to the right or left
 Suspect thoracic outlet syndrome if
 Dysaesthesia of ulnar nerve + medial cutaneous nerve of arm + medial
cutaneous nerve of forearm
 Look for elbow deformities
 Palpate ulnar nerve in flexion and extension for subluxation
 Check elbow ROM
 Examine hand
 Tinels test – positive in 24% of asymptomatic patients
 Elbow flexion test
 Maximally flex elbow in forearm supination and wrist extension
 Positive test if symptoms in <1 minute



Sensation – Semmes Weinstein (innervation density test)
Intrinsic muscle sparing may occur with Martin-Gruber anastamosis (7.5%)
FDP/FCU usually spared – innervation may branch off proximal to cubital tunnel
or axons are in deeper fascicles in the tunnel
Investigations
 Xray
 elbow (arthritis, history of trauma) - approximately 20% to 29% of patients
with cubital tunnel syndrome had abnormalities, compared with 6% of
controls
 CXR (pancoast tumor, cervical rib) and cervical spine xray as indicated
 Electrophysiology
 Nerve conduction
 focal slowing of ulnar nerve segment across elbow
 considered positive for cubital tunnel syndrome when the motor
conduction velocity across the elbow is less than 50 m/s or the difference
between the motor conduction velocity across the elbow and that below
the elbow is greater than 10 m/s.
 During the test, it is important to stimulate the nerve over 2-cm intervals to
precisely localize the area of entrapment.
 80% of patients with mild symptoms and 47% with severe symptoms will
have normal conduction velocities
 Postoperative velocities often fail to correlate with clinical outcomes
 EMG
 1st dorsal interossei most commonly affected
 test APB to exclude C8-T1 root lesion
 MRI
 sensitive and specific in the diagnosis of ulnar nerve entrapment at the elbow.
 may be useful if the patient has previously undergone an anterior transposition
of the ulnar nerve.
 increased signal intensity in the nerve is more sensitive than enlargement for
entrapment of the nerve.
 Disadvantage: expense

Classification
Nonoperative Treatment
1. Splinting at 45 flexion
a. studies have shown that the intraneural and extraneural pressures
within the cubital tunnel are lowest at 45 degrees of flexion.
2. Protective elbow pads
3. Recommend decreasing activities of repetition that may exacerbate the
patient's symptoms
 Nonperative measures should be tried for 3-6 months in those with mild
symptoms (velocities >40ms)
 Urbaniak believes patients with the following traits should undergo a trial of
conservative treatment:
1. early symptoms, intermittent episodes
2. mild paresthesias without significant pain
3. minimal physical findings (slight numbness), with normal motor examination
Operative Treatment
1. In situ decompression


May relieve traction problems by improving excursion of ulnar nerve
Advantages
1. simple and easy to perform
2. low morbidity.
3. In contrast to other methods, avoids damage to the vascular supply of the
nerve.
4. requires minimal or no postoperative immobilization.
5. documented results are equally successful to those of other decompression
procedures
 Disadvantage
 Inability to relieve dynamic stresses on the nerve
 Indications
1. Mild ulnar nerve compression (McGowan 1)
2. Non subluxing nerve
3. Absence of pain around medial epicondyle
4. Normal osseous anatomy
5. Findings at surgery consistent with compression under fibrous arcade
 Technique
 10cm incision centred between medial epicondyle and olecranon
 beware medial brachial and forearm nerves
 ulnar nerve is not disturbed in its bed
 if nerve subluxates – transpose or epicondylectomy
2. Medial epicondylectomy
 best indication - nonunion of an epicondyle fracture with ulnar nerve
symptoms.
 Other indications are a poor bed for the ulnar nerve in the retrocondylar
groove or ulnar nerve subluxation.
 Compared to a simple decompression, the possibility of elbow stiffness or an
elbow flexion contracture developing is greater
 A poor choice for athletes who throw because of the significant stresses placed
on the medial aspect of the elbow joint
 Advantages
 Less dissection than anterior transposition
 Disadvantages
 Elbow joint instability
 Bone tenderness
 Flexor forearm weakness
 Ectopic bone formation
 Technique
 15cm incision over nerve
 CTR released but nerve left in bed
 medial epicondyle exposed subperiosteally
 flexor-pronator origin detached and reflected distally
 osteotome thru epicondyle, preserving UCL
 Muscle mass reinserted in elbow extension
3. Anterior transposition
 Indications



1. unsuitable bed for the nerve secondary to the presence of osteophytes, a
tumor, a ganglion, an accessory anconeus epitrochlears muscle,
heterotopic bone, significant bursal tissue or other mass.
2. significant tension on the ulnar nerve as implicated with a positive elbow
flexion test result
3. subluxation of the ulnar nerve with elbow flexion
4. deformity at the elbow secondary to a valgus elbow or a tardy ulnar palsy
Advantages
1. moves the ulnar nerve from an unsuitable bed to one that is less scarred.
2. nerve is effectively lengthened a few centimeters with transposition.
Disadvantages
1. Technically more demanding
2. Higher complications
3. Risk of devascularising the ulnar nerve
Variations
1. Subcutaneous transposition
 Procedure of choice for throwing athletes, during operative reduction
of an acute fracture, elbow arthroplasty, and neurorrhaphy.
 Disadvantage is the superficial location of nerve and blood supply
concerns
 Technique: creation of a dermofascial sling or myofascial sling to hold
nerve in position
2. Intramuscular transposition
 yields the fewest excellent results and the most recurrences with severe
ulnar nerve compression
 Advantage - it buries the nerve deeply, yet provides a tunnel for the
nerve to pass through. It also allows the nerve to be entirely
surrounded by vascularized muscle tissue.

Disadvantages: it is a complicated procedure. It involves significant
soft tissue dissection. Risk of perineural scar is increased, and the
procedure may expose the nerve to repeated muscular contractions.
 Technique: create 5mm deep channel in pronator, and repair flexorpronator aponeurosis over the nerve
3. Submuscular transposition
 offers the best results with the fewest recurrences with severe ulnar
nerve compression
 best salvage procedure when previous surgery has failed because it
places the nerve in an unscarred bed.
 Also works well for patients who are very thin, in whom a
subcutaneous transposition may result in an area of hypersensitivity
over the transposed nerve.
 Many consider it the procedure of choice for symptomatic athletes who
throw.
 Contraindications : significant scarring or distortion of the elbow joint
capsule, such as in a malunited fracture or in a patient who has
undergone excisional arthroplasty.
 Disadvantages:
1. Technically demanding procedure.
2. Higher morbidity
3. Increased pain
4. Prolonged splintage
5. risk of elbow flexion contracture is 5-10%.
6. extensive scar formation from the procedure
7. difficult procedure to revise if the patient has a recurrence.
4. Transmuscular transposition
 Mackinnon describes a variation of submuscular transposition  step-lengthening incision in the flexor-pronator mass is used to
develop fascial flaps, and a transmuscular tunnel is created through the
muscle
Literature Review
Treatment from Dellon’s review of 50 reports 1989
1. McGowan Grade 1 – 50% success with nonoperative measures, >90% success
with any surgical options
2. McGowan Grade 2 – submuscular transposition gave the best results with fewest
recurrences
3. McGowan Grade 3 – Submuscular transposition gave the best results and
intramuscular the worst
Biggs Neurosurg 2006
Randomised study: In-situ release vs submuscular transposition
 Both procedures equally effective but transposition had higher complications
(wound infection)
Bartels Neurosurg 2005
Randomised study: In-situ release vs subcutaneous transposition
 Both procedures equally effective but transposition had higher complications
Post Operative
 Ensure early mobility exercises at elbow to prevent tethering of the nerve
 Dellon recommends 8 days of immobilization
 Mackinnon recommends that all patients begin range-of-motion exercises for
the hand, wrist, elbow, and shoulder within 2 to 3 days after surgical treatment
Complications
 Recurrence
 Often due to incomplete release of the medial intermuscular septum
(secondary compression point) or at the flexor-pronator mass (Mackinnon)
 Lack of recovery of intrinsics or sensation is not an indication to reoperate – it
may be that recovery will never be complete in these severe cases. Should
document electrophysiologic deterioration compared to preoperative levels.
 Medial cutaneous nerve of forearm injury (20%)
 Hyperalgesia of this nerve may give a false positive Tinels sign and may lead
to reoperation
 Test by superficially blocking the nerve
 Treated by excising neuroma and burying it proximally in muscle
 FCU weakness with injury to its branches
 Perineural fibrosis with devascularisation
 recurrent ulnar nerve subluxation
 elbow flexion contracture
 most common after submuscular transposition (5-10%)
 Medial epicondylitis can occur from detachment of the flexor pronator mass or as
a result of a medial epicondylectomy.
 Medial elbow instability
 According to O'Driscoll et al, excision of more than 20% (1-4 mm) of the
width of the medial epicondyle in the coronal plane violates the important
anterior band of the MCL
ULNAR TUNNEL SYNDROME
 Compressive neuropathies in the canal of Guyon are less common, but they can
also result in significant disabilities.
Aetiology
1. Space occupying lesions (32-48%)
 Ganglia, ulnar artery aneurysms,synovitis
2. Muscle anomalies (16%)
 Most arise from antebrachial fascia of the forearm.
 Thought to be an accessory abductor digiti minim
3. Trauma – hamate fractures, distal radius fractures with marked dorsal
displacement of distal fragments
Anatomy
 Guyons canal - interaponeurotic space about 4 cm in length with discrete
anatomical limits and boundaries.
 It extends from the proximal edge of the palmar carpal ligament, which is the
distal extent of the antebrachial fascia, to the fibrous edge of the hypothenar
muscles
 Ulnar artery lies radial and volar to the nerve
 Boundaries
o Radial: hook of hamate, junction of the roof, including the palmaris brevis
muscle, to the flexor retinaculum
o Ulnar: Flexor carpi ulnaris, the pisiform, and the abductor digiti minimi
constitute the ulnar wall
o Roof: proximally is composed of the palmar carpal ligament which
blends with the tendinous insertion of the flexor carpi ulnaris into the
pisiform bone. Distally, the palmaris brevis muscle, hypothenar fat and
fibrous tissue form the roof
o Floor: floor is made up of the pisohamate ligament centrally, fibres of the
transverse carpal ligament and the opponens digiti minimi radially, and
fibres of the pisometacarpal ligament distally and ulnarly

Compression can occur in 1 of 3 zones. (Gross and Gelberman)
1. Zone 1 is in the most proximal portion of the canal, where the nerve is a single
structure consisting of motor and sensory fascicles
o Boundaries
1. Dorsal – FDP and TCL
2. Volar/radial – palmar carpal ligament
3. Medial – pisiform and FCU
o Compression by ganglions, hook fracture and anomalous muscles
2. Zones 2 - motor branch
o Boundaries
1. Dorsal –pisometacarpal and pisohamate ligaments. Triquetrohamate
joint, opponens digiti minimi
2. Volar – palmaris brevis, fibrous arch insertion of flexor digiti minimi
over hook of hamate Radial - TCL, flexor digiti minimi, hook of
hamate
3. Ulnar – abductor digiti minimi, Sensory branch
o Path – leaves the tunnel between abductor and flexor digiti minimi,
pierces opponens digiti minimi and then curves radially and dorsally
around the hook of hamate under fibrous arch (pisohamate tunnel)
o Compression caused by hook fractures and ganglions
3. Zone 3 - superficial branch
o Boundaries
1. Dorsal – hypothenar fascia
2. Volar – Palmaris brevis and ulnar artery
3. Radial – motor branch
4. Ulnar – abductor digiti minimi
o Compression by ulnar artery lesion (thrombosis, aneurysm), anomalous
abductor digiti minimi, synovitis
Clinical
 Pain is less a feature
 Often worse with sustained hyperextension and hyperflexion of wrist
 Weakness in hand
 Examine for masses
 Percussion test
 Allen’s test – for confirmation of ulnar collateral circulation; thrombosis or
aneurysm of the ulnar artery can be a cause of ulnar neuropathy, which may be
predicted if Allen’s test shows slowed circulation from the ulnar artery
Management
 Surgery indicated for fractures and space occupying lesions, and failure of
conservative management
 Landmark – nerve lies ulnar side of 4th ray
 Some surgeons release carpal tunnel at the same time
 Incision for Guyon canal release
 Start 3cm proximal to crease at radial border of FCU
 Cross wrist at 60 and continue in between pisiform and hook of hamate
 Angle radially parallel to proximal transverse palmar crease
 If compression was located in zone 2, after releasing Guyon's canal the fibrous
arcade of the pisohamate tunnel is cut and the deep branch of the ulnar nerve was
released distally