New Classification System for Radially Deviated Thumb Polydactyly.

PURPOSE: Radially deviated thumb polydactyly (RDTP) is a risk factor for secondary deformities but lacks comprehensive characterization. We developed a new classification system for RDTP based on the preoperative radiographic appearance that should inform surgical approaches: (1) D-shaped, (2) bell-shaped, (3) radial-concave phalanges, and (4) asymmetric Wassel III-like.

METHODS

Radially deviated thumb polydactyly patients evaluated from January 2015 to December 2021 were classified into four types based on their preoperative radiographs. Reliability of the classification was assessed, and patient demographics, radiographic measurements, and intraoperative findings were retrospectively reviewed.

RESULTS

Twenty-nine patients with RDTP (29 affected thumbs) were included and classified as follows: type I (n = 9), type II (n = 10), type III (n = 8), and type IV (n = 2). The interobserver and intraobserver kappa values for the classification system were 0.928 and 0.963, respectively.

CONCLUSIONS

Our proposed RDTP classification system is reliable and may offer surgical guidance for the treatment of patients with RDTP.

TYPE OF STUDY/LEVEL OF EVIDENCE: Prognostic IV.