Hallux Valgus Pronation Correction by Scarf Osteotomy: Prospective Case Series with WB-CT Scan

Abstract

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: Hallux valgus is one of the most prevalent foot deformities. Coronal metatarsal rotation (pronation) has been recognized as a key element in hallux valgus deformity and an important prognostic factor for recurrence. New surgical techniques have been developed in order to specifically address pronation deformity but tend to be technically demanding. With the advent of weight bearing CT (WBCT), accurate pronation measurement has improved. Deformity correction by means of metatarsal osteotomies has been an effective way to correct transverse plane deformity but its capacity for pronation correction is not well established. Purpose: Assess transverse and coronal plane rotation deformity correction by WBCT in hallux valgus patients after scarf osteotomy. Methods: We prospectively analyzed hallux valgus deformity in patients who underwent Scarf osteotomy for symptomatic hallux valgus with preoperative and at least 3 month postoperative WBCT for comparison. Intermetatarsal angle (IMA), hallux valgus angle (HVA) and alpha angle (AA) for first metatarsal rotation (pronation) was measured by 3 different observers. The intraclass correlation was determined. Pre and postoperative measurement change was established by T-test and Wilcoxon for related samples. Results: 40 feet in 25 patients were included. The interclass correlation between observers was 0.9 for AA (pronation), 0.92 for IMA and 0.95 for HVA in preoperative evaluation and 0.94 for AA, 0.65 for IMA and 0.82 for HVA in postoperative evaluation. The mean preoperative and postoperative AA of the first metatarsal was 8.9 degrees (range -8.83-24,40, SD 6.8) and 6.3 degrees (range -10.7-28.4, SD 8.3) respectively, resulting in a significant first ray pronation change of -2.5 degrees (P =.006). The media preoperative and postoperative IMA was 13.1 degrees (SD 2.9) and 4.9 degrees (SD 2.0) respectively, demonstrating a significant change (P <.001). The media preoperative and postoperative HVA was 25 degrees (SD 6.7) and 5.9 degrees (SD 4.2) respectively, demonstrating a significant change (P <.001) Conclusion: The Scarf osteotomy for hallux valgus deformity has a significant power to correct both transverse and coronal plane (pronation) deformity.