Biomechanical evaluation of plate positioning in ulnar shortening osteotomy for nonunion prevention

Ulnar shortening osteotomy (USO) is a commonly used technique for treating ulnar impaction syndrome (UIS), but nonunion remains a non-negligible complication. Currently, there is still no consensus on the best surgical protocol to prevent nonunion. There are limited studies on plate placement, which is a key factor influencing the mechanical environment at the osteotomy site. In this study, finite element analysis (FEA) was used to investigate the biomechanical differences between volar and dorsal plate fixation in USO. The results showed that the volar-side plate model demonstrated superior initial stability with significantly lower interfragmentary strain than the dorsal-side plate model, particularly under axial (48.6% reduction) and extension (38.3% reduction) loading. The von Mises stress analysis demonstrated the biomechanical superiority of the volar-side plate over dorsal-side plate in ulnar shortening osteotomy, as evidenced by lower stress values under four loadings, and more favorable stress distribution patterns, especially reduced stress concentrations at critical locations. These findings suggested that volar-side plate fixation would provide better initial stability for healing, providing insights into optimizing surgical strategies for USO.