Cubital Tunnel Syndrome - Hand

Introduction

A compressive neuropathy of the ulnar nerve
- 2nd most common compression neuropathy of the upper extremity
Sites of entrapment
- most common
  - between the two heads of FCU/aponeurosis (most common site)
  - within arcade of Struthers (hiatus in medial intermuscular septum)
  - between Osborne's ligament and MCL
- less common sites of compression include
  - medial head of triceps
  - medial intermuscular septum
  - medial epicondyle
  - fascial bands within FCU
  - anconeus epitrochlearis (anomalous muscle from the medial olecranon to the medial epicondyle)
  - aponeurosis of FDS proximal edge
- external sources of compression
  - fractures and medial epicondyle nonunions
  - osteophytes
  - heterotopic ossification
  - tumors and ganglion cysts
Associated conditions
- cubitus varus or valgus deformities
- medial epicondylitis
- burns
- elbow contracture release

Anatomy

Ulnar nerve
- pierces intramuscular septum at arcade of Struthers 8 cm proximal to the medial epicondyle as it passes from the anterior to posterior compartment of the arm
- enters cubital tunnel
Cubital tunnel
- roof
  - formed by FCU fascia and Osborne's ligament (travels from the medial epicondyle to the olecranon)
- floor
  - formed by posterior and transverse bands of MCL and elbow joint capsule
- walls
  - formed by medial epicondyle and olecranon

Presentation

Symptoms
- paresthesias of small finger, ulnar half of ring finger, and ulnar dorsal hand
  - exacerbating activities include
    - cell phone use (excessive flexion)
    - occupational or athletic activities requiring repetitive elbow flexion and valgus stress
- night symptoms
  - caused by sleeping with arm in flexion
Physical exam
- inspection and palpation
  - interosseous and first web space atrophy
  - ring and small finger clawing
  - observe ulnar nerve subluxation over the medial epicondyle as the elbow moves through a flexion-extension arc
- sensory
  - decreased sensation in ulnar 1-1/2 digits
- motor
  - loss of the ulnar nerve results in paralysis of intrinsic muscles (adductor pollicis, deep head FPB, interossei, and lumbricals 4 and 5) which leads to
    - weakened grasp
      - from loss of MP joint flexion power
    - weak pinch
      - from loss of thumb adduction (as much as 70% of pinch strength is lost)
    - Froment sign
      - compensatory thumb IP flexion by FPL (AIN) during key pinch
        
        compensates for the loss of MCP flexion by adductor pollicis (ulna n.)
        
        adductor pollicis muscle normally acts as a MCP flexor, first metacarpal adductor, and IP extensor
    - Jeanne sign
      - compensatory thumb MCP hyperextension and thumb adduction by EPL (radial n.) with key pinch
        
        compensates for loss of IP extension and thumb adduction by adductor pollicis (ulna n.)
    - Wartenberg sign
      - persistent small finger abduction and extension during attempted adduction secondary to weak 3rd palmar interosseous and small finger lumbrical
    - Masse sign
      - palmar arch flattening and loss of ulnar hand elevation secondary to weak opponens digiti quinti and decreased small finger MCP flexion
- extrinsic weakness
  - Pollock's test
    - shows weakness of two ulnar FDPs
- provocative tests
  - Tinel sign positive over cubital tunnel
  - elbow flexion test
    - positive when flexion of the elbow for > 60 seconds reproduces symptoms
  - direct cubital tunnel compression exacerbates symptoms

Studies

EMG / NCV
- helpful in establishing diagnosis and prognosis
- threshold for diagnosis
  - conduction velocity <50 m/sec across elbow
  - low amplitudes of sensory nerve action potentials and compound muscle action potentials

Treatment

Nonoperative
- NSAIDs, activity modification, and nighttime elbow extension splinting
  - indications
    - first line of treatment with mild symptoms
  - technique
    - night bracing in 45° extension with forearm in neutral rotation
  - outcomes
    - management is effective in ~50% of cases
Operative
- in situ ulnar nerve decompression without transposition
  - approach
    - elbow medial approach
  - indications
    - when nonoperative management fails
    - before motor denervation occurs
  - technique
    - open release of cubital tunnel retinaculum
    - endoscopically-assisted cubital tunnel release
      - favorable early results but lacks long-term data
  - outcomes
    - meta-analyses have shown similar clinical results with significantly fewer complications compared to decompression with transposition
    - 80-90% good results when symptoms are intermittent and denervation has not yet occurred
    - poor prognosis correlates most with intrinsic muscle atrophy
- ulnar nerve decompression and anterior transposition
  - indications
    - failed in situ release
    - throwing athlete
    - patient with poor ulnar nerve bed from tumor, osteophyte, or heterotopic bone
  - technique
    - subcutaneous, submuscular, or intramuscular transposition
  - outcomes
    - similar outcomes to in situ release but increased risk of creating a new point of compression
- medial epicondylectomy
  - indications
    - visible and symptomatic subluxating ulnar nerve
  - technique
    - in situ release with medial epicondylectomy
  - outcomes
    - risk of destabilizing the medial elbow by damaging the medial ulnar collateral ligament

Complications

Recurrence
- secondary to inadequate decompression, perineural scarring, or tethering at the intermuscular septum or FCU fascia
- higher rate of recurrence than after carpal tunnel release
Neuroma formation
- iatrogenic injury to a branch of the medial antebrachial cutaneous nerve may cause persistent posteromedial elbow pain

Questions (8)

(OBQ11.128) The physical exam finding demonstrated on the patient's right hand in the video (Figure V) is found with neuropathy of which of the following nerves? Review Topic

QID: 3551

FIGURES:

V

1

Musculocutaneous nerve

0%

(10/2736)

2

Anterior Interosseious Nerve (AIN

21%

(565/2736)

3

Radial nerve

2%

(42/2736)

4

Ulnar nerve

73%

(2005/2736)

5

Median nerve

4%

(100/2736)

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

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(OBQ10.84) Cubital tunnel syndrome is caused by compression of the ulnar nerve between what two structures as it passes posterior to the medial epicondyle? Review Topic

QID: 3172

1

Osborne's ligament and the MCL

66%

(1754/2667)

2

MCL and Arcade of Struthers

6%

(169/2667)

3

Osborne's ligament and the intermuscular septum

16%

(430/2667)

4

MCL and medial head of the triceps

1%

(36/2667)

5

Ulnar and humeral heads of the flexor carpi ulnaris muscle

10%

(265/2667)

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

(OBQ09.1) All of the following are possible sites of compression for the ulnar nerve EXCEPT: Review Topic

QID: 2814

1

arcade of Struthers

17%

(353/2093)

2

ligament of Struthers

75%

(1565/2093)

3

flexor carpi ulnaris fascia

2%

(49/2093)

4

medial intermuscular septum

3%

(73/2093)

5

Osborne's ligament

2%

(45/2093)

Select Answer to see Preferred Response

PREFERRED RESPONSE 2

(OBQ09.24) A 50-year-old man complains of numbness and tingling along his right small finger. Physical exam is notable for the finding demonstrated in Figure A. Elbow flexion reproduces the numbness and tingling. Physical therapy and splinting have failed to relieve the symptoms. Which of the following is the most appropriate surgical intervention to alleviate the symptoms while minimizing complications? Review Topic

QID: 2837

FIGURES: