Split flexor pollicis longus tendon transfer to A1 pulley for correction of paralytic Z deformity of the thumb.

PURPOSE: To test the hypothesis that split flexor pollicis longus (FPL) transfer to the A1 pulley will correct a thumb paralytic Z deformity and that the transfer can be subjected to early postoperative active mobilization protocol.

METHODS: In a prospective trial, 19 consecutive thumbs with ulnar or combined ulnar and median nerve paralysis received split FPL transfer to the thumb A1 pulley and active mobilization of transfer after 48 hours. Outcomes were assessed by correction of Z deformity during pinch, tendon transfer insertion pullout during early active mobilization, range of motion at the thumb metacarpophalangeal and interphalangeal joints, and postoperative treatment time. Data from historical records of 20 thumbs with split FPL to extensor pollicis longus (EPL) and 3 weeks' immobilization, treated before the prospective trial in the same institution, were used for comparison.

RESULTS: All 19 thumbs with split FPL to A1 pulley achieved Z deformity correction at discharge from rehabilitation. There was no incidence of transfer insertion pullout during active mobilization, and patients were discharged 22 days earlier than the controls who received transfer of FPL to EPL insertion. Seventeen thumbs were available for follow-up more than 1 year after the index procedure. Fifteen thumbs retained deformity correction, and 2 had recurrence of Z deformity. The interphalangeal joint had considerably greater active motion following split FPL to A1 pulley compared with transfer of split FPL to EPL insertion.

CONCLUSIONS: This study supports the hypothesis. Split FPL tendon transfer to thumb A1 pulley can correct paralytic thumb Z deformities and be mobilized early for transfer re-education. Improved interphalangeal joint active motion and reduced treatment time are added advantages over FPL transfer to the EPL insertion.

TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic III.