EX-000078·DNB Ortho·2023·Peripheral Nerve Injury — Sunderland Classification

Peripheral nerve injury. Describe the anatomy of ulnar nerve. Enumerate the causes of claw hand and describe the differences between low and high ulnar nerve palsy. Algorithm for management of ulnar nerve palsy

Wiki topic: Peripheral Nerve Injury — Sunderland Classification

Answer

Ulnar Nerve Palsy — Anatomy, Claw Hand and Management

DNB Orthopaedics • October 2023 • Paper I • Question 2 • 10 Marks [3+3+4]

Introduction

The ulnar nerve is the major motor nerve to the intrinsic muscles of the hand. It is derived predominantly from the C8–T1 roots through the medial cord of the brachial plexus. Injury produces characteristic weakness of intrinsic hand muscles, sensory loss along the ulnar side of the hand and, in established lesions, ulnar clawing.

The characteristic deformity is caused by paralysis of the intrinsic muscles of the ring and little fingers, producing MCP hyperextension with PIP and DIP flexion.

A. Anatomy of the Ulnar Nerve [3 Marks]

Origin

Terminal branch of the medial cord of brachial plexus
Root value: predominantly C8–T1, with variable contribution from C7

Course

MEDIAL CORD — C8, T1
        ↓
Medial side of axillary/brachial artery
        ↓
MEDIAL ARM
        ↓
Pierces medial intermuscular septum
        ↓
Posterior compartment of arm
        ↓
Behind MEDIAL EPICONDYLE
        ↓
CUBITAL TUNNEL
        ↓
Between humeral & ulnar heads of FCU
        ↓
Deep to FCU in forearm
        ↓
Travels with ulnar artery distally
        ↓
Wrist
        ↓
GUYON'S CANAL
        ↓
Superficial sensory branch
+
Deep motor branch