Abstract: BACKGROUND: Ulnar impaction syndrome is a common wrist disorder, and ulnar shortening osteotomy is one of the definitive surgical interventions for its treatment. Although various ulnar shortening osteotomy techniques exist, numerous clinical comparative studies have focused on pairwise comparisons, while biomechanical simulations comparing the efficacy of different osteotomy methods via finite element analysis remain unreported. 
OBJECTIVE: To simulate and compare the biomechanical characteristics of ulnar impaction syndrome under different osteotomy treatment modalities employing finite element method so as to provide references and evidence for clinical decision-making.
METHODS: CT data of the intact ulna and radius from a healthy adult male volunteer were utilized. Modeling and finite element software platforms — Mimics 19.0, Geomagic Studio 2013, SolidWorks 2019, and Ansys 17.0 — were sequentially applied to construct five ulnar osteotomy models: (1) distal ulnar V-shaped osteotomy; (2) distal ulnar transverse osteotomy; (3) ulnar metaphysis transverse osteotomy; (4) distal ulnar trapezoidal osteotomy; (5) distal ulnar oblique osteotomy. Following experimental design and internal fixation principles, plates and screws were assembled. Three simulated wrist motion states (axial compression, pronation, and supination) were applied to each model with corresponding constraints and loads. Stress and displacement nephograms, along with quantitative data at the osteotomy sites and fixation devices, were analyzed and compared against experimental benchmarks to draw relevant conclusions.
RESULTS AND CONCLUSION: (1) Under three different motion patterns (different loads), all five ulnar shortening osteotomy models demonstrated comparable stability at the osteotomy sites, with no significant relative differences. (2) Variations in stress deformation of internal fixation devices among the five different ulnar shortening osteotomy methods were observed across three simulated motions: Transverse metaphyseal osteotomy fixation plates exhibited fracture risks during pronation and deformation risks during supination. (3) The V-shaped distal ulnar osteotomy fixation demonstrated superior stability in stress distribution and displacement across all three simulated conditions.

Key words: ulnar impaction syndrome, shortening osteotomy, finite element, stress, displacement