Thirty cases of duplication of the thumb. Operative results

Thirty cases of duplication of the thumb have been seen during a period of 8 years. Twenty-four children underwent surgery for a total of 25 operations, and these are reviewed after a follow-up of at least a year. Wassel's type IV was the most frequent type, occurring in 14 cases. There were 23 primary operations, and 2 reoperations for frontal deviation, which were secondary to operations done elsewhere. The average age at the time of operation was 16 months, the mean follow-up is 4 years (1 to 8 years). The results are analyzed according to Wassel's criteria. Regardless of the location of the duplication, function is unaffected, the structure of the thumb is good, and the parents are satisfied. However, examination revealed some loss of mobility in 10 cases, shortening of the thumb in 5 cases, instability of the collateral ligament in 3 cases and axis deviation in 10 cases. Six of these were clinodactyly at the IP, 1 a clinodactyly at the MP and 3 Z-shaped deformities at the IP and MP. The two reoperations were done to correct a significant loss of alignment, and in each the result was upgraded from "poor" to "fair". It seems that the end results are determined at the original operation which should be done before the 18th month. The thumb with the least function, usually on the radial side, is resected and the remaining component reconstructured. This includes centralization of the insertions of the extrinsic muscles, and reinsertion of the thenar muscles. Immobilization by pinning is usually done due to the need for an osteotomy during the surgery for realignment of the axis of the thumb. It must, however, always be remembered that this surgery is cosmetic rather than functional.