Congenital flexion deformities of the thumb.

A congenital flexion deformity of the IP joint of the thumb is usually due to a trigger finger. The diagnosis is based on the thumb being normal except for a fixed, flexed posture of the IP joint and a palpable nodule in the FPL tendon at the level of the A-1 pulley. Treatment can be postponed until after age 1, as spontaneous regression probably occurs in about 30 per cent of cases. After that age, surgical correction is the best approach to treatment and usually results in normal thumb function. Congenital soft tissue flexion deformities of the MP joint of the thumb vary from passively correctable deformities due to loss of extensor power to severe, fixed contractures involving multiple thumb structures and associated with significant anomalies of the wrists and fingers. The passively correctable deformities will frequently respond to cast immobilization in the very young but can otherwise be treated by an appropriate tendon transfer to re-institute active extension. Complex clasped thumb deformities require elucidation of the specific pathologic features of the deformity, based both on clinical evaluation and surgical exploration. These digits will require not only an extensive release to correct the fixed contracture but also reconstructive procedures to correct lax ligaments and to substitute for absent muscles and skin as appropriate. The latter deformities are often associated with a syndrome affecting numerous body structures. It is hoped that recognition of these syndromes and documentation of the pattern of pathology present in these thumbs will result in a better method of classification.