Anomalies of the intrinsic muscles in camptodactyly.

Our observations support the view of Millesi that camptodactyly is due to an imbalance between the flexor and extensor forces acting upon the proximal interphalangeal joint. In 21 consecutive operations the insertion of the lumbrical muscle was abnormal. The muscle inserted into either the superficialis tendon (in three cases), the capsule of the metacarpophalangeal joint (in 15), or the extensor expansion of the adjacent finger (in four). The fourth palmar interosseous muscle was examined in the last 10 patients and was abnormal in five. It was absent in two patients, small in one, and inserted into the extensor expansion of the ring finger in two patients. Therefore, it is suggested that camptodactyly is an intrinsic minus deformity. It follows that treatment should consist of soft tissue release, as necessary, to correct the flexion deformity, followed by a tendon transfer to restore intrinsic action and maintain correction of the deformity.