Camptodactyly resulting from paradoxical action of an anomalous lumbrical muscle.

A 17 year old girl presented with camptodactyly resulting from an anomalous insertion of the lumbrical muscle into the flexor digitorum superficialis tendon. The fourth anomalous lumbrical muscle paradoxically caused flexion of the proximal interphalangeal (PIP) joint of the little finger when the patient extended the fingers fully. She was operated on, and the lumbrical tendon was cut at its insertion into the flexor digitorum superficialis tendon. The tight fascial band and skin contracture at the PIP joint were released, and the skin defect covered with a transposed flap. She made a good recovery and eight months after operation had only 40 degrees residual flexion deformity with full flexion of the PIP joint of the little finger.