Tendon transfers for thumb opposition: a biomechanical study of pulley location and two insertion sites

The purpose of this biomechanical study was to test 5 proximal tendon pulley sites or routes of tendon transfer and 2 distal tendon insertion sites that are used commonly for performing a thumb opposition transfer.

Five fresh-frozen cadaver arms were used to test (1) an around flexor carpi ulnaris (FCU) pulley, (2) an FCU loop pulley, (3) a Guyon's canal pulley, (4) a junction of the distal edge of the transverse carpal ligament and the ulnar border of the palmar aponeurosis (Royle-Thompson pulley), and (5) a palmar thenar subcutaneous transfer (Camitz). Two tendon insertion sites were tested: a palmar radial insertion into the abductor pollicis brevis and a dorsal ulnar insertion into the thumb proximal phalanx.

The Guyon's canal and Royle-Thompson pulleys produced the greatest amount of approximation of the thumb pulp to the fifth metacarpal head. The around the FCU pulley, FCU loop pulley, and Camitz transfer produced the greatest palmar abduction. The Guyon's canal and Royle-Thompson pulleys were the most mechanically efficient pulleys, producing the least amount of transmitted force. The palmar radial insertion site produced better thumb opposition, metacarpophalangeal joint abduction, metacarpophalangeal joint flexion, and approximation of the thumb pulp to the fifth metacarpal head.

We conclude that the choice of the proximal pulley used may depend on the needs of the transfer, and a palmar radial thumb insertion is more effective than the dorsal ulnar insertion.