Ulnar Tunnel Syndrome - Hand

Introduction

Ulnar nerve compression neuropathy caused by direct compression in Guyon's canal
- also known as handlebar palsy (seen in cyclists)
Pathoanatomy
- causes of compression include
  - ganglion cyst (80% of nontraumatic causes)
  - lipoma
  - repetitive trauma
  - ulnar artery thrombosis or aneurysm
  - hook of hamate fracture or nonunion
  - pisiform dislocation
  - inflammatory arthritis
  - fibrous band, muscle or bony anomaly
  - congenital bands
  - palmaris brevis hypertrophy
  - idiopathic

Anatomy

Boundaries of Guyon's canal
Floor	Transverse carpal ligament, hypothenar muscles
Roof	Volar carpal ligament
Ulnar border	Pisiform and pisohamate ligament, abductor digiti minimi muscle belly
Radial border	Hook of hamate
Zones of Guyon's canal
	Location	Common Causes of Compression	Symptoms
Zone 1	Proximal to bifurcation of the nerve	Ganglia and hook of hamate fractures	Mixed motor and sensory
Zone 2	Surrounds deep motor branch	Ganglia and hook of hamate fractures	Motor only
Zone 3	Surrounds superficial sensory branch	Ulnar artery thrombosis or aneurysm	Sensory only

Deep branch of the ulnar nerve
- innervates all of the interosseous muscles and the 3rd and 4th lumbricals.
- Innervates the hypothenar muscles, the adductor pollicis, and the medial head (deep) of the flexor pollicis brevis (FPB)

Classification

Presentation varies based on location of compression within Guyon's canal and may be
- Motor only
- Sensory only
- Mixed Motor & Sensory

Presentation

Presentation varies based on location of compression within Guyon's canal and may be
- pure motor
- pure sensory
- mixed motor and sensory
Symptoms
- pain and paresthesias in ulnar 1-1/2 digits
- weakness to intrinsics, ring and small finger digital flexion or thumb adduction
Physical exam
- inspection & palpation
  - clawing of ring and little fingers
    - caused from loss of intrinsics flexing the MCPs and extending the IP joints
  - Allen test
    - helps diagnose ulnar artery thrombosis
- neurovascular exam
  - ulnar nerve palsy results in paralysis of the intrinsic muscles (adductor pollicis, deep head FPB, interossei, and lumbricals 4 and 5)
  - 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
    - IP flexion compensating for loss of thumb adduction when attempting to hold a piece of paper
    - loss of MCP flexion and adduction by adductor pollicis (ulnar n.)
    - compensatory IP hyperflexion by FPL (AIN)
  - Jeane's sign
    - a compensatory thumb MCP hyperextension and thumb adduction by EPL (radial n.)
    - compensates for loss of IP extension and thumb adduction by adductor pollicis (ulna n.)
  - Wartenberg sign
    - abduction posturing of the little finger

Imaging

Radiographs
- useful to evaluate hook of hamate fractures
CT scan
- useful to evaluate hook of hamate fractures
MRI
- useful to evaluate for a ganglion cysts
- a gradient echo MRI will also show an ulnar artery aneurysm
Doppler US or arteriogram
- useful to diagnosis ulnar artery thrombosis and aneurysm

Studies

NCS and EMG
- 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

Differential

Treatment

Nonoperative
- activity modification, NSAIDS and splinting
  - indications
    - as a first line of treatment when symptoms are mild
Operative
- local decompression
  - indications
    - severe symptoms that have failed nonoperative treatment
- tendon transfers
  - indications
    - correction of clawed fingers
    - loss of power pinch
    - Wartenberg sign (abduction of small finger)
- carpal tunnel release
  - indications
    - patients diagnosed with both ulnar tunnel syndrome and CTS

Techniques

Complications