Movement patterns of intrinsic minus fingers. Role of intrinsic and extrinsic muscles in finger posture control.

A detailed study of the patterns of two movements (pure metacarpophalangeal flexion and pure interphalangeal extension) in intrinsic minus fingers shows that the long extensors and long flexors produce simultaneous movement at the metacarpophalangeal and interphalangeal joints. A comparison of the patterns of these movements in totally intrinsic minus and interosseous minus fingers shows that in the latter the lumbricals are probably largely inactive during attempted pure metacarpophalangeal flexion and contribute to restrain metacarpophalangeal extension considerably during attempted pure interphalangeal extension. Active participation by the interosseous muscles appears necessary for completing these movements.