Incidence and Associated Factors of 2-Legged Nitinol Staple Breakage in Foot and Ankle Surgery

BACKGROUND: Nitinol staples (NSs) are increasingly used in foot and ankle surgery; nonetheless, staple breakage incidence and determinants remain incompletely defined. This study examined NS breakage in a large consecutive series, focusing on anatomical site, implant geometry, and fixation strategy. METHODS: We retrospectively reviewed 333 patients (379 feet) who underwent foot and ankle surgery with 2-legged NS between 2021 and 2025. Overall, 702 staples were analyzed. Staple breakage was assessed on plain radiographs at a minimum follow-up of 6 months to evaluate implant integrity during the critical phase of bone union. Anatomical location, implant geometry (symmetric vs asymmetric), and fixation type (isolated vs combined) were analyzed. Multivariable logistic regression was performed to explore factors associated with breakage in the hindfoot. RESULTS: The overall breakage rate was 4.0% (28/702). Breakage rates varied by anatomical site, with higher rates in the calcaneocuboid (22.2%), talonavicular (12.5%), tibiotalar (8.9%), and other joints than in the first ray (0.37%). In the calcaneocuboid joint, isolated staple fixation showed a higher breakage rate (33.3%) than staple fixation with an adjunct screw (6.7%). In second metatarsal shortening osteotomies, asymmetric staples demonstrated a higher breakage rate (35.7%) than symmetric staples (1.0%). Although most breakages were asymptomatic, 2 patients required revision surgery for symptomatic nonunion. In the hindfoot cohort, procedure category (Chopart arthrodesis) showed an association with breakage; however, with the numbers available, no significant association could be detected for body mass index or sex. CONCLUSION: The overall breakage rate for 2-legged NS was 4.0%. Breakage was more frequent in several high-demand hindfoot joints, and in second metatarsal osteotomies using asymmetric staples. Hybrid fixation showed a lower breakage rate in the first ray and calcaneocuboid joint. These exploratory findings suggest that anatomical site, staple geometry, and fixation strategy may contribute to the risk of radiographic staple breakage.