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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 topic
    • 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
 

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Questions (4)

(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:
1

Musculocutaneous nerve

0%

(4/2012)

2

Anterior Interosseious Nerve (AIN

18%

(372/2012)

3

Radial nerve

1%

(27/2012)

4

Ulnar nerve

75%

(1511/2012)

5

Median nerve

5%

(91/2012)

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PREFERRED RESPONSE 4

The video demonstrates Froment's sign on the patient's right hand, which is characterized by interphalangeal (IP) flexion during attempted key pinch, and is found in patients with ulnar neuropathy. Therefore it can be found with ulnar nerve compression in the cubital tunnel (Cubital Tunnel Syndrome) or in Guyon's Canal (Ulnar Tunnel Syndrome).

Froment's sign is performed by having the patient pinch a piece of paper with the thumb IP joint extended against resistance (pulling paper away). It should be done with both hands side by side to compare them to each other.

In a hand with a ulnar neuropathy, adductor pollicis (ulnar n.) is deficient, and can not flex the MCP joint to give pinch strength with an extended IP joint. The thumb compensates by recruiting the FPL (median n.) to flex the IP joint to give pinch strength. The result is, in a positive Froment's sign, the IP joint will flex (buckle) to try to give increased strength to the pinch.

Illustration V shows a demonstration of the Froment's sign.

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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

64%

(1042/1635)

2

MCL and Arcade of Struthers

6%

(105/1635)

3

Osborne's ligament and the intermuscular septum

18%

(289/1635)

4

MCL and medial head of the triceps

1%

(23/1635)

5

Ulnar and humeral heads of the flexor carpi ulnaris muscle

10%

(170/1635)

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PREFERRED RESPONSE 1

The ulnar nerve passes posterior to the medial epicondyle and medial to the olecranon, then enters the cubital tunnel. The roof of the cubital tunnel is primarily made up of Osborne's ligament, and the floor consists of the medial collateral ligament.

These soft tissue structures can cause narrowing of the tunnel, especially with elbow flexion, leading to ulnar nerve compression and cubital tunnel syndrome. This is shown in Illustration A. The Arcade of Struthers is a band of deep fascia that attaches to the intermuscular septum and covers the ulnar nerve 8 cm proximal to the medial epicondyle. The intramuscular septum is continuous from the medial epicondyle to the coracobrachialis muscle. The ulnar nerve travels through the two heads of the FCU distal to the cubital tunnel. These anatomic landmarks are shown in Illustration B.

Morrey evaluated 26 patients with post-traumatic contracture of the elbow who were treated with either operative release alone, or operative release and distraction arthroplasty. Twenty-four (96%) of the patients had improved elbow function and two had persistent ulnar neuritis treated with nerve transposition.

Cheung et al discuss the various surgical approaches to the elbow and the indications for each.

Video V is an educational lecture that discusses common nerve entrapment diagnosis and managment.

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(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%

(306/1847)

2

ligament of Struthers

75%

(1389/1847)

3

flexor carpi ulnaris fascia

2%

(42/1847)

4

medial intermuscular septum

3%

(63/1847)

5

Osborne's ligament

2%

(41/1847)

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PREFERRED RESPONSE 2

There are five sites of potential ulnar nerve entrapment around the elbow: arcade of Struthers, medial intermuscular septum, medial epicondyle, cubital tunnel, and deep flexor pronator aponeurosis.

The ulnar nerve emerges from the medial intermuscular septum, under the arcade of Struthers, and lies on the medial head of the triceps. At the level of the elbow, the ulnar nerve continues distally toward the posterior aspect of the condylar groove, passing between the medial epicondyle and olecranon to enter the cubital tunnel. The roof is formed by the arcuate (Osborneā€™s) ligament. This ligament blends distally with the antebrachial fascia superficial to the aponeurosis and connects the ulnar and humeral heads of the FCU. The ligament of Struthers is a fibrous band extending from the supracondylar process of the humerus to the medial epicondyle which can cause compression of the median nerve.

Elhassan et al discuss the pathogenesis, evaluation, and treatment of entrapment neuropathy of the ulnar nerve.

Illustration A shows the various site of compression at the elbow. Illustration V shows a submuscular ulnar nerve transposition performed Dr. Susan E. Mackinnon

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(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:
1

Simple ulnar nerve decompression at the cubital tunnel

77%

(1161/1512)

2

Ulnar nerve decompression at the cubital tunnel with anterior submuscular transposition

10%

(158/1512)

3

Ulnar nerve decompression at the cubital tunnel with anterior subcutaneous transposition

12%

(177/1512)

4

Open carpal tunnel release

0%

(7/1512)

5

Endoscopic carpal tunnel release

0%

(2/1512)

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PREFERRED RESPONSE 1

The patient's clinical presentation and physical exam are consistent with cubital tunnel syndrome. The clinical photograph demonstrates Froment's sign; compensatory IP hyperflexion of FPL (AIN) to compensate for the loss of adductor pollicis (ulnar nerve) during key pinch. Simple decompression of the ulnar nerve is less invasive and achieves clinical outcomes equivalent to decompression with transposition.

Zlowodzki et al conducted a meta-analysis evaluating anterior transposition and simple decompression of the ulnar nerve. No difference in motor nerve-conduction velocities or clinical outcome scores was found.

Bartels performed a prospective randomized trial (included in the Zlowodski meta-analysis) on 152 patients comparing simple decompression to transposition. No difference in clinical results at 1 year were reported, but a significantly higher complication rate occurred in the transposition group (31%) compared to simple decompression (9.6%).

Nabhan et al performed a level 1 study randomizing 66 patients to simple decompression or subcutaneous ulnar nerve transposition. No differences were found with respect to clinical outcome or nerve conduction velocities.

Illustration V is an educational presentation discussing ulnar nerve transposition at the elbow.

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