Flexor Digitorum Superficialis Opposition Transfer for Augmenting Function in Types II and IIIA Thumb Hypoplasia

Purpose To report the functional outcomes associated with the flexor digitorum superficialis (FDS) opposition transfer for types II and IIIA thumb hypoplasia and determine if there is any noteworthy difference in the outcome dependent on the pulley used. Methods We included patients who underwent a ring FDS opposition transfer and had at least 2 years follow-up. The study group consisted of 36 patients with 40 treated thumbs. All patients underwent follow-up examination and standardized testing. Outcome functional measures were recorded using the Pediatric Outcomes Data Collection Instrument (PODCI). There were 9 type II and 31 type IIIA hypoplastic thumbs. All patients underwent a ring FDS opposition transfer and a 4-flap z-plasty for first web space deepening. The pulley for opposition was flexor carpi ulnaris in 19 and the transverse carpal ligament in 21. Thirty-six thumbs had ulnar collateral ligament reconstructions, with 5 of the 36 undergoing combined ulnar collateral ligament/radial collateral ligament stabilizations. Average follow-up was 7.6 years (range, 2-16 years). Results Average postoperative Kapandji score was 8 (range, 4-10). Grip, lateral pinch, and tripod pinch strengths averaged 46%, 49%, and 48% of age- and sex-matched normal controls, respectively. There was no significant difference between surgical pulleys used. The Pediatric Outcomes Data Collection Instrument global was 91 (range, 53-100), and PODCI happiness was 87 (range, 15-100). Conclusions We found the ring FDS opposition transfer to be an effective method for providing opposition for both type II and IIIA thumb hypoplasia. At follow-up, excellent opposition function and PODCI scores were noted, with no difference related to the type of pulley used. Type II thumbs had significantly greater grip and pinch strengths when compared with type IIIA thumbs. Type of study/level of evidence Therapeutic IV.