Clinical Findings and Treatments of a Radially Deviated Type of Thumb Polydactyly.

BACKGROUND: Patients with some thumb polydactyly subtypes are regarded as having a high risk of secondary deformities or poor treatment outcomes. Radially deviated type is one of these subtypes, but its characteristics and definitive treatment outcomes remain unclear. This study aimed to evaluate the pre- and intraoperative findings and surgical outcomes of this subtype. METHODS: We identified eight patients with unilateral and proximal phalanx-type polydactyly. The mean age at surgery was 14.6 months, and the mean follow-up period was 7.2 years. We investigated the patients' initial radiograms, surgical procedures and findings, changes in alignment of the retained thumb, and postoperative outcomes using the Japanese Society for Surgery of the Hand scoring system. RESULTS: Although the gross appearance of the thumb was a radial deviation, there was an ulnar deviation at the metacarpophalangeal joint on radiography. The ulnar proximal phalanges were delta phalanges in three patients and were connected with the radial proximal phalanges by cartilage in five patients. We retained the ulnar thumbs in all patients and corrected the alignment in seven cases; open wedge osteotomy was performed for three patients with a delta phalanx, and tendon transfers from the radial to ulnar thumb were performed for the other four. The mean outcome score was 17.6/20, with one patient with excellent, six with good, one with fair, and none with poor scores. One patient experienced recurrent radial deviation around the interphalangeal joint five years after surgery and underwent corrective osteotomy, but the other patients maintained good alignment. CONCLUSIONS: Radially deviated thumb polydactyly is not simply radially deviated; the shape of the proximal phalanx of the ulnar thumb is important to determine the surgical procedure. However, our results indicated that the alignment is almost manageable, and the surgical outcome was comparable to that of patients with a proximal phalanx-type thumb polydactyly.