Immediate Thumb Opposition Following Extensor Indicis Proprius Opponensplasty Using the Wide-Awake Approach

Abstract

Background: The wide-awake approach enables surgeons to adjust tendon transfer tension during active movement. Objective: To examine the proximity of the index finger to the thumb in the motor network of the brain during extensor indicis proprius (EIP) opponensplasty, performed under local anesthesia, for restoration of thumb opposition in patients with thenar paralysis caused by advanced carpal tunnel syndrome. Methods: Between April 2009 and October 2013, seven patients underwent wide-awake opponensplasty of the EIP in conjunction with carpal tunnel release. Under local anesthesia (lidocaine with epinephrine), the EIP tendon was routed subcutaneously, around the distal ulna and across the palm to the abductor pollicis brevis tendon. Results: Immediately after severing the EIP tendon over the metacarpophalangeal joint of the index finger, patients exhibited varying degrees of retraction of the proximal end of the EIP tendon into the dorsal subcutaneous space when asked to perform thumb opposition while maintaining active flexion of the index finger. All patients were able to perform palmar abduction of the thumb via the EIP following opponensplasty. Discussion: The intraoperative data suggest that single, individuated movements of the thumb opposition activate both the thenar muscle and the EIP. Additionally, these phenomena may be explained by activation of a pre-existing neural network, and overlap between the thumb and index finger in the motor cortex. Conclusion: Achievement of immediate thumb opposition without re-education suggests that the index finger and thumb are in close proximity in the motor network of the brain.