A combined classification system for preaxial foot polydactyly and its derived surgical strategies

Pediatric polydactyly is a relatively common congenital condition of hand and foot, affecting physical and mental development of children. Hand polydactyly has been brought into focus recently. By contrast, the studies on foot polydactyly are limited. Among the types, there is little international research on preaxial foot polydactyly since it is a relatively rare type, and the domestic research on it is fewer. The purpose of our study is to propose a new classification for guiding operation. We collected all patients with preaxial foot polydactyly who had preoperative radiographs at our hospital between 2016 and 2024, and analyzed the reported classifications, finally proposed a new classification system based on the preoperative radiographs. The 64 feet were assessed by 5 observers under the help of the kappa statistic. We operated the derived surgery on various types of the classification system, and evaluate the therapeutic efficacy through the relative imaging parameters and scale. We developed a combined classification system for preaxial foot polydactyly, describing variation of hallux in longitudinal dimension. In this classification system, we concluded duplication of distal phalanx combined with abnormal/ normal proximal phalanx, duplication of proximal phalanx combined with abnormal/ normal proximal phalanx or metatarsal, duplication of metatarsal combined with abnormal proximal phalanx and duplication of tarsal. Overall inter-observer agreements for this classification system respectively were 0.805 and 0.795 in first and second reading and intra-observer agreements for 5 observers were > 0.9. Under the derived surgery, the scale for the hallux with preaxial foot polydactyly exhibited notable improvement. The proposed new classification effectively show different features of all categories, the reliability of which was proved good. The derived surgical strategies of the combined classification system improved the surgical outcomes significantly, which can effectively correct hallux varus and prevent hallux valgus to some extent.