A study of the dynamic anatomy of extensor tendons and implications for treatment.

This study correlates the excursion of the extrinsic finger extensors in zones V, VI, and VII and the extensor pollicis longus tendon in zones T IV and T V ("T" is used to designate thumb zones) with joint motion. Excursion was estimated by review of the literature, biomechanic calculations, and intraoperative observations. A simple equation determines extrinsic extensor tendon excursion in zone V, VI, and VII. This equation is substantiated by Brand's work on radians and by intraoperative studies. Guidelines are suggested for controlled motion for extrinsic finger extensors and the extensor pollicis longus tendon on the basis of our 6 years experience of treating extensor tendon injury with early passive motion.