Clinical Outcome of Modified Wassel-Flatt Type IV Radial Polydactyly: Analysis of Subtype and Morphology

This study assessed the differences in clinical outcomes among the subtypes of type IV radial polydactyly and evaluated the distribution of the duplication range according to subtype.

This retrospective study included 85 patients with 89 affected thumbs, who were treated at a single center from October 2017 to May 2023. The patients were classified according to the modified Wassel-Flatt classification, and only those with type IV radial polydactyly were included. The collected data included demographics, surgical techniques, clinical outcomes, and radiological outcomes. Clinical outcomes were analyzed using the Japanese Society for Surgery of the Hand (JSSH) scoring system.

The most common subtype of radial polydactyly was IV-B, accounting for 50 patients. Types IV-C and IV-D accounted for 17 and 22 patients, respectively. The median age at the time of surgery was 10 months, and the median follow-up was 24 months. Type IV-D demonstrated significantly lower total JSSH scores and functional parameter scores than types IV-B and IV-C. Regarding functional parameters, type IV-D exhibited significantly poorer outcomes in terms of interphalangeal joint stability and alignment, as well as range of motion; however, metacarpophalangeal joint stability and alignment were similar among the types. Type IV-D also exhibited significant differences in the distribution of the duplication range compared with type IV-B and IV-C. It had a more distal duplication level.

Type IV-D radial polydactyly requires more complex surgical interventions and has less favorable outcomes than types IV-B and IV-C. It exhibits poorer functional outcomes, particularly in the interphalangeal joint and range of motion assessments. Furthermore, type IV-D exhibits differences in the duplication range compared with other subtypes, and has a more distal duplication level.

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