Three dimensional finite element analysis of biomechanics of osteotomy ends with three different fixation methods after hallux valgus minimally invasive osteotomy.

PURPOSE Biomechanical study of fixation methods post hallux valgus minimally invasive osteotomy using finite element technology hasn't been reported. This study aimed to compare maximum displacement and stress distribution of osteotomy ends after minimally invasive osteotomy fixed by bandage, Kirschner wire, Herbert screw. METHODS Foot CT images of a patient with mild-moderate hallux valgus were collected. Three-dimensional finite element model of hallux valgus was established through CT image. This study simulated bandage, Kirschner wire and Herbert screw fixation, and analyzed maximum displacement and stress distribution of osteotomy ends in plantar flexion position of foot after fixation. RESULTS Maximum equivalent stress of osteotomy end fixed with bandage, Kirschner wire, Herbert screw was 7.8615, 14.253, 8.3156 MPa, respectively. Total displacement of osteotomy end fixed by bandage, Kirschner wire, Herbert screw was 0.26,896, 0.022,779, 0.029,195 mm, respectively. Maximum stress of Kirschner wire and Herbert screw near osteotomy end was 154.7 and 46.404 MPa, respectively. Fixation strength and stability of Kirschner wire and Herber screw were better than bandage. Kirschner wire had stress concentration phenomenon, with potential fracture risk. Stress of Herbert screw was evenly distributed around osteotomy end, and there was a certain stress concentration, playing an important role in maintaining fracture end stability. CONCLUSIONS Herbert screw showed good fixation strength and stability, and stress distribution was uniform, which can well maintain stability of minimally invasive osteotomy ends. Findings of this study would provide a theoretical basis for selection of fixation methods after clinical minimally invasive osteotomy for hallux valgus.