Variation of Extrinsic Tendons of the Thumb in Type IIIA Hypoplastic Thumbs.

ABSTRACT

PURPOSE: The purpose of this study was to identify the variety of anatomical abnormalities of extrinsic tendons in type IIIA hypoplastic thumbs. METHODS: We reviewed 79 thumbs in 67 patients. Opponensplasty, stabilizing of the thumb metacarpophalangeal joint, and widening of the first web space were performed in all patients. At the time of surgery, we made detailed observations of the anatomical abnormalities of the extrinsic tendons of the thumb. RESULTS: Fifty thumbs (50 of 79; 63%) had an interconnection between the flexor pollicis longus (FPL) and the extensor pollicis longus (EPL) tendons. Twenty-six thumbs (26 of 79; 33%) had bifurcations (25 [32%] bifurcated from the FPL; 1 [1%] bifurcated from the EPL). There were 25 FPL abnormalities (4 [5%] complete absence; 8 [10%] proximal absence; 2 [3%] distal absence; 11 [14%] tendon hypoplasia) and 7 EPL abnormalities (2 [3%] proximal absence; 5 [6%] tendon hypoplasia). CONCLUSIONS: Interconnections between the FPL and the EPL tendons and a duplicated FPL were observed frequently. CLINICAL RELEVANCE The present study investigates the detailed anatomy of the type IIIA hypoplastic thumbs. The data might help improve the design of surgical procedures.