Association of calcaneal pitch angle with recurrence of postoperative hallux valgus in patients with rheumatoid arthritis

Hallux valgus (HV) and flatfoot deformities are frequently seen in patients with rheumatoid arthritis (RA). This study aimed to determine whether flatfoot deformity contributes to the recurrence of HV in RA patients. This study examined 62 feet from 45 RA patients who were diagnosed with HV and underwent the first metatarsal joint-preserving surgery between November 2010 and October 2021. Recorded data included age at surgery, sex, disease duration, body mass index [BMI], RA disease duration, medical treatment of RA, Larsen grade, blood test, pre/postoperative Japanese Society for Surgery of the Foot, HV angle, M1M2 angle, M1M5 angle, calcal pitch angle, and Meary's angle. HV recurrence on radiography was defined as an HV angle exceeding 20°. HV recurrence was observed in 17 feet. Significant differences were observed due to risk factors such as BMI, disease duration, Larsen grade 4–5, and preoperative calcaneal pitch angle. Multivariate logistic regression analysis identified that lower BMI, a higher M1M2 angle, and a lower calcaneal pitch angle are preoperative risk factors for the recurrence of postoperative HV in RA patients.