Restoration of active palmar abduction of the thumb in tetraplegia by tendon transfer of the extensor digiti minimi to abductor pollicis brevis

Abstract

We describe a method to restore active palmar abduction of the thumb and report its functional impact in tetraplegia. At 54.2 (SD 42.8) months after cervical spinal cord injury (12 traumatic, 3 nontraumatic), the extensor digiti minimi (EDM) tendon was transferred to the abductor pollicis brevis (APB) through the interosseous membrane in 15 tetraplegic patients (age range 19–70 years) in addition to a mean 3.2 procedures to restore key pinch. According to International Classification, the operated upper extremities were in the OCu4 to OCu8 (1 patient X) group. The maximum distance between thumb and index finger tips during active or passive opening of the hand, maximum angle of palmar abduction, grip and key pinch strength, and active finger range of motion were measured. All patients were re-examined after 38.4 (SD 22.7) months. The active thumb-index opening increased significantly from 2.5 (SEM 1.0) cm before to 9.0 (SEM 0.8) cm after surgery. Nine patients without previous active opening of the first web space recovered a mean thumb-index opening of 9.1 (SEM 1.7) cm, whereas this distance increased by an average of 2.9 (SEM 0.8) cm in six patients who had active thumb index distance of 6.3 (SEM 1.6) cm before surgery. All but one patient were able to direct and coordinate key pinch and perform tasks using the restored APB function, including five patients whose EDM strength was rated as grade 3 before transfer. This EDM-to-APB transfer meets the theoretical requirements of architecture matching between donor and recipient muscles, the principles of tendon transfer, and our surgical expectations. We strongly recommend that an active EDM is transferred to the APB to restore opening of the hand and help in key pinch control in patients with tetraplegia.