What is Ulnar Nerve Injury its treatment

Introduction

Ulnar nerve is the largest branch of the medial cord of the brachial plexus with root value of C8-T1

It arises at the level of pectoralis minor muscle, run through the axilla and lie in the ,medial compartment of the arm

And further pierce the medial intermuscular septum at the level of coracobrachialis and lie in the posterior compartment of the arm

It passes over the posterior aspect of the medial epicondyle and enters in forearm through the two heads of flexor carpi ulnaris via the elbow.

Lies beneath the flexor carpi ulnaris muscle within the forearm

At the junction of middle and lower one-third of forearm it gives a dorsal sensory branch,

which winds round the forearm and passes dorsally to supply the dorsum of the ulnar border of the hand, the little finger, and median half of ring finger

Injuries of the ulnar nerve are usually either near the wrist or near the elbow, although open wounds may damage it at any level.

Causes of ulnar nerve injury

Local causes are more important and could be in the following areas:

CAUSES AT THE AXILLA

  1. Crutch pressure in axilla
  2. aneurysm of the axillary vessels

CAUSES IN THE ARM :

  1. Fracture shaft of humerus
  2. Gunshot and penetrating injuries

CAUSES AT THE ELBOW :

  1. Compression by the accessory muscle
  2. Fracture of lateral epicondyle of humerus
  3. Repeated occupational strain
  4. Compression by the osteophytes as in rheumatoid and osteoarthritis
  5. Cubitus valgus deformity due to various causes results in repeated friction of the nerve giving rise tardy (late) ulnar nerve palsy

CAUSES IN THE FOREARM

  1. Fracture of both the bones in forearm
  2. Incised wounds, penetrating injuries of the forearm

CAUSES AT THE WRIST AND HAND

  1. Compression by osteophytes
  2. Fracture hook of the hamate
  3. Compression by ganglion
  4. Blunt trauma
  5. Penetrating injuries
  6. Ulnar nerve injuries give rise to claw hand deformity either true type or ulnar claw hand

Features

There is numbness of the ulnar one and a half fingers

The hand assumes a typical posture in response that is the claw hand deformity with hyperextension of the metacarpophalangeal joints of the ring and little fingers, due to weakness of the intrinsic muscles.

Hypothenar and interosseous wasting may be obvious by comparison with the normal hand.

Finger abduction is weak and this, together with the loss of thumb adduction, makes pinch difficult.

FROMENT’S SIGN is tested : The individual is asked to grip a sheet of paper forcefully between thumbs and index fingers while the examiner tries to pull it away

powerful flexion of the thumb interphalangeal joint signals weakness of adductor pollicis and first dorsal interosseous with overcompensation by the flexor pollicis longus.

‘Ulnar neuritis’ may be caused by compression or entrapment of the nerve in the medial epicondylar (cubital) tunnel,

especially where there is severe valgus deformity of the elbow or prolonged pressure on the elbows in anaesthetized or bed-ridden patients

Treatment

Exploration and suture of a divided nerve are well worthwhile, and anterior transposition at the elbow permits closure of gaps up to 5 cm. While recovery is awaited, the skin should be protected from burns.

Hand physiotherapy keeps the hand supple and useful.

When nerve division occurs without recovery, it significantly impairs hand function.

Diminished grip strength results from the loss of primary metacarpophalangeal flexors, leading to poor pinch due to weakened thumb adduction and index finger abduction, and affecting fine, coordinated finger movements.

Extensor carpi radialis longus to intrinsic tendon transfers (Brand) or looping a slip of flexor digitorum superficialis around the opening of the flexor sheath (Zancolli procedure) can improve metacarpophalangeal flexion.

Index abduction is improved by transferring extensor pollicis brevis or extensor indicis to the interosseous insertion on the radial side of the finger

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