Biomechanics of the human flexor tendon sheath investigated by tenography.

Tenography has been performed on eight detached fingers and two intact hands of cadavers. Bulging and overlapping of synovial pockets between the ligamentous structures during flexion, their flattening during extension and the continuous change in expansion of the proximal cul de sac suggests a possible mixing mechanism for the synovial fluid. During flexion and extension a physiological joint-type bowstringing of the flexor tendons was observed at the PIP and DIP joints. This finding supports the theory that the flexor tendon moment arm is increased at these joints.