Prediction of Surgical Outcomes of Radial Polydactyly From the Wassel-Flatt Type and Symmetry of Duplication

Abstract

Background: The Wassel classification is commonly used for cases of radial polydactyly but has not been used to predict surgical outcomes. This study aimed to investigate the predictive factors of surgical outcomes using the Wassel type and symmetry of duplication. Methods: Forty-five patients with 47 radial polydactylies were reviewed using the Japanese Society for Surgery of the Hand (JSSH) scores 4.6 years after minor thumb excision and reconstructive surgery. The symmetry index was defined as the metaphyseal width ratio of the minor thumb to the dominant thumb. The relationships between the JSSH scores and operation age, sex, side, follow-up duration, Wassel type, symmetric index, divergent angle, and joint angulation were analyzed by linear regression. Results: The mean JSSH score of the 47 thumbs was 18.3 points (range, 15–20). Five thumbs had fair or poor outcomes (scores <17), all of which were Wassel type IV. The hypoplastic type had a better JSSH score (19.4) than other Wassel types. The symmetric index had a negative relationship with JSSH scores, especially for Wassel type IV (r=−0.68, P=0.001). Linear regression revealed that the symmetric index was the only independent factor significantly associated with JSSH scores among Wassel type IV polydactylies (P<0.05). The receiver operating characteristic curve suggested a symmetric index <0.74 could predict good or excellent outcomes. Conclusion: The symmetry of the 2 duplicated thumbs is an important factor for surgical outcomes. The Wassel type IV polydactylies with a symmetric index >0.74 are at greater risk of fair or poor outcomes after excision and reconstruction, and further studies are warranted to confirm whether the Bilhaut-Cloquet procedure is a good choice. Level of Evidence: Level IV—Case-control study.