Split flexor pollicus longus tendon transfer for stabilization of the thumb interphalangeal joint: A cadaveric and clinical study

The split flexor pollicus longus (FPL) tendon transfer is a surgical techni que using the radial half of the FPL tendon rerouted dorsally and inserted into the extensor pollicis longus tendon for correction of Froment's sign. A cadaveric model was designed to investigate the effects of the split FPL tendon transfer on pinch strength. Pinch strength was compared for extrinsi c thumb flexion (1) without the split FPL and (2) with the split FPL, tensi oned at 3 different positions (0 degrees flexion, 30 degrees flexion, and 6 0 degrees flexion). We report the clinical results of key pinch strength us ing split FPL tendon transfer as part of thumb reconstruction for 12 thumbs in 10 patients at an average follow-up time of 2 years. The cadaveric stud y showed no significant difference in pinch force between specimens with or without split FPL transfer or when comparing tensioning at 0 degrees versu s 30 degrees versus 60 degrees. Froment's sign was reproduced in all cadave rs with pinch activation without split FPL transfer and was eliminated in a ll specimens after the split FPL transfer. In the clinical portion of this study 12 transfers in 10 patients had an average follow-up pinch strength o f 33.7 N (range, 18-80 N) and no evidence of Froment's sign. We conclude th at the split FPL tendon transfer is an effective method for correction of F roment's sign due to intrinsic paralysis of the thumb. (J Hand Surg 1999;24 A:1303-1310. Copyright (C) 1999 by the American Society for Surgery of the Hand.).