Ulnar Nerve Compression

Elbow – Cubital Tunnel Syndrome

Anatomical Sites of Compression

  1. Medial Intermuscular Septum
  2. Arcade of Struthers (80% of people, 8 cm above medial epicondyle)
  3. Medial Head of Triceps
  4. Medial Epicondyle
  5. Osborne’s Ligament (roof of cubital tunnel)
  6. Anconeus Epitrochlearis (anomalous muscle)
  7. Heads of FCU
  8. Flexor Pronator Aponeurosis

Non-Anatomical Causes

  1. Subluxating Ulnar nerve
  2. Cubitus valgus
  3. Rheumatoid arthritis
  4. Ganglions
  5. Tumors
  6. Direct pressure

Diagnosis

History

  • Duration of symptoms
  • Weakness
  • History of trauma/exacerbating factors
  • Associated pain

Examination

  • Neck
  • Deformity
  • Scars
  • Wasting
  • Clawing
    • Ulnar paradox – Less clawing with proximal lesion

Sensory Deficit

  • Volar aspect of the palm
  • Ulnar border of forearm
  • Dorsum of hand (ulnar aspect)

Motor Tests

  • Froment’s sign – Weak thumb adduction
  • ECU function
  • FDP to little and ring fingers

Special Tests

  • Tinel’s sign
  • Wartenberg’s sign
    • Persistent abduction of little finger on attempted adduction
    • Due to unopposed EDM pull
  • Elbow flexion provocation test
  • Sensation over dorsum of hand (dorsal cutaneous branch)

Differential Diagnosis

  • Thoracic Outlet Syndrome (TOS)
    • Pain in the entire hand, proximal symptoms
    • X-ray may show cervical rib
  • Pancoast Tumor
    • Similar to TOS but CXR shows tumor
  • C8/T1 Radiculopathy
    • Pain is a feature, neck symptoms present
    • Spurling’s sign positive, MRI for confirmation

Investigations

  • NCS – Quantifies denervation and rules out proximal cause
  • MRI – Of spine to rule out radiculopathy
  • X-ray – If deformity or OA, check for mechanical compression

Management

General Points

  • Try non-operative management first if sensory symptoms only
  • Address non-anatomical causes if necessary
  • Explain that recovery may not be complete, especially if motor deficit present
  • Clawing may increase during recovery, as FDP recovers first
  • Best results occur before motor neuropathy develops

Non-Operative

  • Activity modification, splinting, padding
    • Splint with elbow at 45° flexion
  • Always attempt for sensory-only cases for 6-8 weeks

Operative

  • Decompression – For sensory-only cases
  • Transposition – If motor involvement or another compressive cause
    • Combine with medial epicondylectomy if OA evidence
  • Subcutaneous vs. Submuscular Transposition
    • No definitive evidence favoring one over the other
    • Transposition is better than none for motor involvement

Problems with Transposition

  • Devascularization of the ulnar nerve can occur
  • Not a blanket procedure for all patients
  • Full release needed to avoid kinking
  • Submuscular transposition may aid vascularity but has longer recovery

Compression at the Wrist – Guyon’s Canal Syndrome

Guyon’s Canal Boundaries

  • Floor – Transverse carpal ligament
  • Roof – Forearm fascia and piso-hamate ligament
  • Radial Border – Hook of hamate
  • Ulnar Border – Pisiform

Contents

  • Ulnar nerve (superficial and ulnar to median nerve at wrist level)
  • Ulnar artery (medial to the nerve)
  • No branches within Guyon’s canal

Ulnar Nerve Anatomy Around the Wrist

Four branches:
1. Dorsal Cutaneous Branch – Proximal to Guyon’s, crosses distal ulna
2. Palmar Cutaneous Branch – Just distal to Guyon’s, medial palm
3. Deep Motor Branch – Hypothenar muscles, interossei, adductor pollicis
4. Superficial Sensory Branch – Little and ring fingers’ digital nerves

Sites of Compression (Divided into Zones)

  • Zone 1 – Proximal to bifurcation (within or before Guyon’s)
    • Mixed motor & sensory involvement
  • Zone 2 – Around Deep Motor Branch
    • Pure motor involvement
  • Zone 3 – Around Superficial Sensory Branch
    • Pure sensory involvement

Typical Causes

  1. Pisotriquetral OA
  2. Hook of Hamate Fracture
  3. Pisotriquetral Ganglion
  4. Ulnar Artery Aneurysm/Thrombosis
  5. Direct Pressure (e.g., cyclists)

Diagnosis

  • History and examination as for elbow compression
  • Define level and likely cause
  • Rule out proximal lesion (neck, thorax, brachial plexus)

Key Features of Wrist Compression

  • Preservation of dorsal hand nerve and forearm innervation
  • Increased Clawing (ulnar paradox)
  • Preservation of FDP power in ring and little fingers
  • Motor or sensory-only involvement defines the zone of compression

Investigations

  • NCS
  • MRI – Especially useful if ganglion suspected
  • X-ray – Rule out OA

Management

Non-Operative

  • Activity modification, splinting, etc.

Operative

  • Explore and decompress Guyon’s canal
  • Address any mechanical compressive lesions
  • Divide piso-hamate ligament if needed
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