Ulnar tunnel syndrome

Ulnar Nerve entrapment

Elbow - Cubital tunnel syndrome

• Most common cause of ulnar nerve entrapment
•  Compressive neuropathy of the ulnar nerve caused by anatomic compression in the medial elbow
• Positive Tinels sign over the cubital tunnel

Causes

• Entrapment
  • Most common sites
    • 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
• External compression
  • Trauma
  • Nerve compression, traction or friction - from leaning on the elbow or prolonged flexion.
  • Joint pathology - osteophytes, arthritis, ganglia.

Sites of entrapment

Clinical features

• Sensory symptoms in the ulnar nerve distribution including the dorsal and palmar cutaneous aspects
• Motor symptoms - weakness of the hand.

Wrist - Ulnar tunnel syndrome

• Less common
• Also referred to as Guyon’s canal syndrome
• Is ulnar neuropathy at the wrist where it passes through the Guyon’s canal.

Causes

• Trauma
• Lacerations.
• Repetitive use of tools in the workplace
• Use of a walker.
• Ganglia

Clinical features

• Typically presents with hand weakness and sensory involvement.

• The sensory involvement typically does not involve the distribution of the dorsal cutaneous nerve or palmer cutaneous branch as these are given off in the forearm.

• The clawing of digits 4 and 5 is generally worst because of the unopposed action of flexor digitorum profundus

• Guyons canal can be broken into 3 zones - depending on what zone is impinged, will depend on what symptoms the patients has

  • Zone 1 - common branch of ulnar nerve - impingement results in sensory and motor symptoms.
  • Zone 2 - impingement results in motor symptoms - deep motor branch supplies interossei, the 3rd and 4th lumbricals, and Opponens digiti minimi - paralysis causes mild hand clawing
  • Zone 3 - impingement results in sensory symptom - superficial sensory terminal branch - ulnar border of the palm and then 1.5 digits on the palmar aspect an the tip

Examination of ulnar nerve

• Look:
  • Evidence of claw hand
    • Flexed 4th and 5th metacarpals with extended proximal and distal phalangeal joints.
  • Hypothenar wasting
  • Guttering between metacarpals
• Sensation
  • 3 territories
    • dorsal cutaneous
    • superficial terminal
    • palmar cutaneous
• Strength
  • Test strength - flexion of 4th and 5th fingers (lumbricals)
  • Test interossei - abduction of fingers
  • Test adductor pollicis - patient holds paper between thumb and second finger (Froment’s test)
• Provocative tests
  • Froments Test - hold paper between thumb and radial side of 2nd digit
    • Sign presents after damage to the ulnar nerve, which innervates the adductor pollicis and interossei muscles, which provide adduction of the thumb and extension of the interphalangeal joint. The flexor pollicis longus (innervated by the median nerve), will substitute for the adductor pollicis (innervated by the ulnar nerve) and cause the thumb to go into hyperflexion.
  • Elbow Flexion Test - flex elbow for 1 minute
    • Numbness and tingling 4th and 5th digits
  • Tinels Tap
    • Can be performed at cubital tunnel and Guyon’s canal
    • Causes numbness and tingling in ulnar nerve distribution
• Ulnar paradox
  • High lesion
    • Proximal
    • Prior to innervation of FDP to 4th and 5th digit
    • Less clawing as action of FDP lost
  • Low lesion
    • Distal
    • Distal to innervation of FDP to 4th and 5th digit
    • More clawing as action of FDP remains - MCPJ hyperextension and flexion PIPJ and DIPJ for digits 4 and 5 possible
    • Still get hypothenar wasting and loss of ADD and ABD

Management

• Ulnar tunnel syndrome
  • Behavioural change:
    • wrist brace
  • Surgery - Guyon’s canal decompression
    • Ulnar nerve decompression
      • indicationsn
        • severe symptoms that have failed nonoperative treatment
    • tendon transfers
      • indications
        • correction of clawed fingers
        • loss of power pinch
        • Wartenberg sign (abduction of small finger)
• Cubital tunnel syndrome
  • Behavioral change:
    • avoid leaning on elbow
    • use of a soft foam elbow
    • wraps of the elbow to limit flexion at nightime
  • Surgery - Ulnar neurolysis
    • Indications
      • When non-operative management fails
    • Options
      • in situ ulnar nerve decompression without transposition
      • ulnar nerve decompression and anterior transposition
      • medial epicondylectomy