A clinical study of forces generated by the intrinsic muscles of the index finger and the extrinsic flexor and extensor muscles of the hand.

A study of the forces generated by the intrinsic muscles of the index finger and coordinating muscles of the hand found that the intrinsic muscles of the index finger contributed combined forces equivalent to approximately 80% of those generated by the flexor profundus and superficialis, and to 73% of the moment for the motion of metacarpopalangeal flexion with simultaneous interphalangeal joint extension. No current tendon transfer operation can correct this deficit, though several supply sufficient force at the metacarpophalangeal joint to counterbalance the extrinsic extensors.