Biomechanical evaluation of thumb opposition transfer insertion sites

The optimal location for insertion of the transferred tendon in opposition transfer is controversial. The purpose of this study was to examine 4 commo nly used insertion sites into the thumb and determine which maximizes thumb opposition. The flexor digitorum superficialis of the ring finger was used as a donor tendon and was attached in random order to the abductor pollici s brevis (APB) tendon, the APE and extensor pollicis longus, the flexor pol licis brevis (FPB) and dorsal radial extensor hood, and the ulnar extensor hood at the base of the proximal phalanx. As normal opposition was simulate d, the minimum distance between the thumb and little finger and the pinch f orce were measured. The FPB and radial dorsal extensor hood site resulted i n the statistically highest pinch force. The FPB and radial dorsal extensor hood and the APE sites had statistically smaller minimum distances between the thumb and little finger than the ulnar extensor hood site. A subjectiv e evaluation of the 3-dimensional thumb path of motion revealed that the FP B and radial dorsal extensor hood site and the APE insertion site allowed t he closest approximation of normal thumb opposition. This biomechanical stu dy supports the use of the FPB and radial dorsal extensor hood insertion si te or APE insertion site for opposition transfers. (J Hand Surg 2001;2 6A:3 54-361. Copyright (C) 2001 by the American Society for Surgery of the Hand. ).