Abductor Pollicis Longus Tendon Abnormalities and Release in Children With Congenital Clasped Thumb

Background: Congenital clasped thumb is associated with deficient thumb extensor tendons. Reconstruction includes tendon transfer. Here, we describe a variant of the abductor pollicis longus (APL) tendon, not previously reported, contributing to the flexion deformity. The purpose of this study is to report examples of and offer surgical repair techniques for APL variants identified in patients with clasped thumb. Methods: We reviewed records of 11 consecutive patients undergoing reconstruction for clasped thumb. Surgical anatomy of the APL tendon was evaluated in all patients, followed by release of aberrant APL attachments. Participants were invited to return for an in-person assessment with a certified hand therapist. Data were collected regarding intraoperative findings, surgical techniques for reconstruction, postoperative thumb motion, and patient and caregiver satisfaction. Results: Eleven children (12 thumbs) underwent aberrant APL release and rerouting between 2019 and 2021. Preoperatively, all thumbs were passively correctible to 0° of extension. In all patients, the APL was found to terminate palmar to the metacarpophalangeal (MCP) joint, creating an MCP flexion moment when tensioned. The average age at surgery was 7 years (range: 1-15 years), and the average follow-up was 14.2 months (range: 1-21 months). The mean postoperative thumb radial abduction was 55° (range: 20°-75°). Conclusions: When reconstructing clasped thumbs, surgeons should explore the presence of APL abnormalities. Release and centralization of the APL can improve thumb position and function. This technique may avoid the need for extra-anatomical tendon transfer in patients with clasped thumb.