Functional anatomy of the human digital flexor pulley system.

The anatomy of 55 cadaver digits was studied, both statistically and with simulated active motion using weights attached to the flexor tendons. The modified description of Doyle and Blythe accurately described the anatomy observed. Serial pulley sectioning showed two types of bowstringing, both of which affected the relationship of tendon excursion to joint motion. The most constant, resulting in 15% loss of motion for a fixed tendon excursion, occurred over the concave surfaces of the proximal and middle phalanges. Bowstringing at the proximal interphalangeal joint was present only after 30 degrees of flexion had occurred, because of the convexity of the phalangeal condyles.