Tendon transfer for median nerve palsy

Abstract

A large number of tendon transfers have been described that restore opposition to the thumb and provide thumb and finger flexion. To provide optimal results following tendon transfers, one needs to follow the principles of tendon transfer: normal tissue equilibrium, movable joints, and a scar-free bed. Once these are present, we must look to available tables to determine an appropriate tendon transfer, matching up the lost muscle mass, fiber length, and cross-sectional area and then pick out muscle-tendon units of similar size, strenght, and potential excursion. For low median nerve palsy, we have found from our experimental and clinical studies that the FDS of the long and ring fingers or the wrist extensors (ECR or ECRL) best approximate the force and motion required for full thumb opposition and strength. These transfers are preferred in median nerve palsy or combined median ulnar nerve palsy when both strength and motion are required. In circumstances where only thumb mobility is desired, the EIP is an ideal tranfer. Also, the extensor digitorum quinti (EDQ) and ADQ have sufficient mean fiber length (muscle excursion) to provide full thumb opposition. The palmaris longus transfer (Camitz transfer) is an abduction rather than an opposition transfer and should be reserved for selected cases of long-term carpal tunnel syndrome. For high median nerve palsy, transfers of the brachioradialis or ECRL to restore lost thumb flexion (FPL) and side-to-side transfer of the FDP of the index finger are generally sufficient. A separate transfer to restore independent flexion of the index finger could be performed by utilizing the pronator teres or extensor carpi radialis ulnaris tendon muscle units. As they combine a proper direction of action, pulley location, and tendon insertion, tendon transfers for median nerve palsy are usually quite successful. In considering any of these elective procedures, however, it is important to remember that tendon transfers are muscle balance operations. The effect of transfer on restoring function must be carefully studied to assess the loss of function that such a transfer may endure.