Weight-bearing CT Scan Analysis in Hallux Valgus Surgery: Comparison between Open (Scarf) and Minimally Invasive (MIBA) Techniques

Abstract

Category: Bunion; Midfoot/Forefoot Introduction/Purpose: Hallux valgus (HV) is one of the most prevalent foot deformities. Coronal metatarsal rotation (pronation) has been recognized as a key element in HV deformity and an important prognostic factor for recurrence. With the advent of weight-bearing CT (WBCT), accurate pronation measurement has improved. The Minimally Invasive Bosh Akin (MIBA) surgery has proven to be effective in treating HV deformity. Literature comparing MIBA radiological correction with traditional open techniques (scarf osteotomy) is lacking. Purpose: To compare the transverse and coronal plane deformity correction by WBCT in HV patients treated with open vs MIS technique. Methods: We retrospectively analyzed HV deformity in patients who underwent Scarf and MIBA surgery with preoperative and at least 3 months postoperative WBCT for comparison. Intermetatarsal angle (IMA), hallux valgus angle (HVA), and alpha angle (AA) for first metatarsal pronation was measured by 2 different observers. Pre and postoperative measurement changes were established by T-test for related samples. the p-value for statistical significance was set at < 0.05. Results: 40 feet included. The mean preop IMA in scarf was 13.1, and 13.6 in MIBA (p= 0.7). Mean postop IMA in scarf was 4.9, and 6.8 in MIBA (p < 0.05). The mean preop HVA in scarf was 25, 28.7 in MIBA (p=0.1). Mean postop HVA in scarf was 5.9, 13.1 in MIBA (p < 0.05). Mean preop AA in scarf was 8.9, 8.9 in MIBA (p= 0.6). Mean postop AA in scarf was 6.3, 6.9 in MIBA (p=0.7). All feet had a significant improvement of IMA and HVA pre and postop (p < 0,005). Scarf preop AA was 8.9 and 6.3 postop, which is a pronation change of -2.5 (p < 0.05). MIBA preop AA was 8.9 and 6.9 postop, which is a pronation change of -2 (p=0.054). Conclusion: To the best of our knowledge, this is the only study that compares WBCT correction between Scarf and MIBA surgery. Both osteotomies have a significant power to correct transverse deformity, scarf corrects significantly better than MIBA when analyzing HVA and IMA. The scarf has a significant power to correct pronation, whereas MIBA shows a strong tendency.