Identifying Risk Factors for Nonunion of the Modified Lapidus Procedure for the Correction of Hallux Valgus

CATEGORY: Bunion; Midfoot/Forefoot INTRODUCTION/PURPOSE: There is a paucity of literature attempting to characterize risk factors for nonunion of the modified Lapidus procedure for correction of hallux valgus. The purpose of this study was to evaluate several patient factors to determine which may contribute to increased odds of nonunion. METHODS: Patients who underwent modified Lapidus procedure between 2009 to 2018 were retrospectively reviewed. Patient age, sex, body mass index (BMI), history of previous bunionectomy, history of tobacco use, fixation method, presence of diabetes mellitus (DM), and presence of hypothyroidism were recorded along with changes in radiographic parameters. A multiple logistic regression analysis was implemented to estimate the odds of nonunion. RESULTS: Of the 222 patients who met inclusion criteria, nonunion with modified Lapidus procedure was observed in 20 patients (9.01%). Odds of nonunion with modified Lapidus procedure were greater for patients as BMI increased (OR=1.101, 95% CI: 1.029 to 1.177), tobacco users (OR=3.511, 95% CI: 1.182 to 10.425), had a change in intermetatarsal angle (IMA) (OR=1.313, 95% CI: 1.099 to 1.569), a change in Meary's angle (OR=1.133, 95% CI: 1.024 to 1.255), and a change in calcaneal pitch (OR=1.192, 95% CI: 0.997 to 1.426), but lower for patients who had a change in hallux valgus angle (OR=0.912, 95% CI: 0.846 to 0.983). Compared with the union group, patients with nonunion had lesser mean degrees correction of IMA (4.25° vs. 7.02°) and greater mean degrees correction of Meary's angle (1.62° vs. 0.46°) and calcaneal pitch (1.09° vs. 0.38°). No increased odds of nonunion were found between fixation methods. CONCLUSION: Predicted odds of nonunion with modified Lapidus procedure increased in patients with high BMI, smokers, and increased change in intermetatarsal angle, calcaneal pitch, and Meary's angle pre and postoperatively.