Nail-based reconstruction strategies for Wassel-Flatt type IVh thumb polydactyly with a floating ulnar digit: A preliminary report with 63 thumbs.

Purpose: To present a surgical regimen based on nail morphology for Wassel-Flatt type IVh thumb polydactyly with a floating ulnar digit.

Methods: Cases within six years were retrospectively analyzed and followed up for an average of 18 months. Three types of classifications were defined based on nail morphology ‒ ulnar nail dominant type with two subtypes of nail lateral fold symmetric or asymmetric, radial nail dominant type, and equal nail size type. One out of three procedures, on-top plasty (Ⅰ), soft tissue augmentation (Ⅱ), and the combination of the above two (Ⅲ), was performed. The Tada scoring system was used to evaluate the results.

Results: Sixty-three thumbs were enrolled, forty-one of better ulnar nail type underwent top transposition, and in cases of asymmetric nail lateral fold subtype, the result of procedure Ⅲ was better than that of procedure Ⅰ, thirteen of the radial nail dominant type and nine of equal nail size type both had procedure Ⅱ. The equal nail size type was the least effective among groups, with an average Tada of four points. Six cases underwent secondary revision surgery. According to the Tada scoring system, the results were excellent in 61, fair in two.

Conclusions: Classifications based on the morphology of the nail can guide surgical planning. On-top plasty is suitable for symmetric nail lateral fold subtype. Soft tissue augmentation is ideal for radial nail dominant type and equal nail size type, and the combination of the two procedures is a better option for asymmetric nail lateral fold subtype.