Tendon Transfers for Ulnar Nerve Palsy

Abstract

Ulnar nerve injury impairs extrinsic and intrinsic hand movements along with sensory loss in the ulnar 1 and ½ digits and ulnar border of the hand. The loss of the intrinsic muscles in the hand results in severe impairment of fine motor actions including key pinch grip and fine precision movements. The loss of flexion of the little and ring distal interphalangeal joints combined with loss of the ulnar wrist flexor and loss of ulnar sensation impairs hand grasp and grip strength. There is a significant cosmetic defect with guttering between the metacarpals, flattening of the metacarpal arch and hypothenar eminence, and clawing of the metacarpophalangeal joints. This is paradoxically worse with functioning flexor digitorum profundi to the little and ring in low injuries or during the recovery phase in high lesions when these ­muscles have been reinnervated. Weak key pinch due to the loss of the first dorsal interosseous and thumb adductor is compensated for by interphalangeal joint flexion (flexor pollicis longus) and adduction (extensor pollicis longus). This is called Froment’s sign. Ulnar clawing is due to the unopposed action of the extensor digitorum communis on the metacarpophalangeal joints leading to hyperextension of these joints and the flexion of the interphalangeal joints by the long flexors. Normally, the intrinsic muscles would flex the metacarpophalangeal joint and extend the interphalangeal joints. The musculotendinous units affected in ulnar nerve palsy: Low lesion: Adductor pollicis Deep head of flexor pollicis brevis Dorsal and palmar interossei Abductor digiti minimi, opponens digiti minimi, flexor digiti minimi Lumbricals to the ring and little fingers High lesion as above plus: Flexor digitorum profundus to the little and ring finger Flexor carpi ulnaris