Triphalangeal thumb without associated abnormalities: clinical characteristics and surgical outcomes.

Thirty-four triphalangeal thumbs of 23 patients, who had no associated anomaly in their ipsilateral hand, were reviewed to clarify the characteristics of an isolated triphalangeal thumb and its surgical outcome. There were 13 type 1 thumbs, 21 type 2 thumbs, and no type 3 thumbs. The existence of an accessory phalanx caused ulnar bending at the interphalangeal joint. Thirteen type 1 thumbs were operated on by excising an accessory phalanx. Corrective osteotomy at the epiphysis was performed on four type 2 thumbs, and partial excision of the epiphysis was performed on 11 type 2 thumbs. At follow-up examination, the average interphalangeal joint motion was 54 degrees in type 1 thumbs and 53 degrees in type 2 thumbs. More than 10 degrees of lateral bending remained in one type 1 thumb and six type 2 thumbs. Good results were observed when an early excision of the accessory phalanx with a securing collateral ligament was performed on type 1 thumbs. For type 2 thumbs, partial excision of the epiphysis provided relatively better correction than osteotomy. For good adaptation of interphalangeal joints, surgery should be performed when the patient is between the ages of 1 and 2, when the epiphysis is visible on x-rays.