May 30, 2024

Ulnar nerve compression occurs mainly at the elbow and wrist as cubital tunnel syndrome and Ulnar tunnel syndrome

A. Cubital Tunnel Syndrome

Compressed at the cubital tunnel which is the second most common compression neuropathy at the wrist

Anatomy

Roof: Formed by FCU fascia and Osborne ligament (travel from the medial epicondyle to olecranon)

Floor: Formed by posterior and transverse bands of MCL and elbow joint capsule

Walls: Formed by medial epicondyle and olecranon

Anatomy of Cubital tunnel
Anatomy of Cubital tunnel

Sites of compression

Compressed in a cubital tunnel

Bony abnormalities, ganglion, hypertrophic synovium, and distal transverse fibers of the arcade of Struthers (8 cm proximal to medial epicondyle)

Proximal to cubital tunnel

Formed by the arcade of stuthers and medial intermuscular septum

Distal to cubital tunnel

Through 2 heads of FCU (Osbourne canal) and Osborne fascia

Sometimes stretched by cubital valgus deformity or elbow flexed for a long period

Clinical features

Investigation

NCV: Conduction velocity of less than 50m/sec across the elbow is typical threshold for diagnosis; larger decrease signifies worse prognosis

Treatment Options

Conservative measure

  • Modification of postures
  • Splinting of the elbow (mid-extension at night)
  • FCU stretching
  • NSAIDs

Operative measures

Indications for surgery:

  • Intrinsic wasting
  • Symptoms persistance

Options:

  • A simple release of the roof of a cubital tunnel (In situ decompression)
  • Anterior transposition of the nerve into a subcutaneous/ submuscular/Intramuscular plane or medial epicondylectomy

B. Ulnar Tunnel Syndrome

Compression in Guyon’s canal of ulnar nerve

Anatomy

Floor: Transverse carpal ligament, hypothenar muscle

Roof: Volar carpal ligament

Ulnar border: Pisiform and pisi-hamate ligament, abductor digiti minimi muscle belly

Radial border: Hook of hamate

Zones of Guyon's canal
Zones of Guyon’s canal

Zones of Guyon’s canal

ZonesLocationCompressionNeurology
Zone 1Proximal to the bifurcation of nerveGanglia and hook of hamateMixed motor and sensory
Zone 2Surrounds deep motor branchGanglia and hook of hamate
Motor only
Zone 3Surrounds superficial sensory branchUlnar artery thrombosis/ aneurysmSensory only

Deep motor branches

  • Innervates all intercostal muscles and 3/4 lumbricals
  • Adductor pollices, Hypothenar muscle, Medial head of FPB

Treatment Options

Non-operative

Activities modification, NSAIDs, and splinting

Operative

  • Local decompression followed by addressing of underlying cause
  • Tendon transfer:
    • Indications:
      • Correction of clawed finger
      • Loss of power pinch
      • Wartenberg sign (abduction of the small finger)
  • Carpal tunnel release
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