The effect of osteotomy inclination in the frontal plane on lateral cortex fracture in medial open wedge high tibial osteotomy procedure

Purpose: The role of thehigh tibial osteotomy technique in the treatment of medial compartment arthrosis, especially in the middle age group, is increasing day by day. Thanks to this technique, it is aimed to reduce the load on the medial compartment by regulating the axis passing over the knee joint. In our study, we will examine the effect of osteotomy inclination in the frontal plane on lateral cortex fracture, which may occur during medial open wedge high tibial osteotomy surgery. Method: Our study is a numerical study based onthe finite element analysis. Our study was done on the computer and completed in Karatay University Mechanical Engineering laboratory. On the solid tibia model created over computed tomography, osteotomies were made at different angles in the computer environment (10°, 13°, 16°, 19°, 22°) and 5 different models created. On the models, force was applied with changes of 5 N, starting from 5 N to 75 N, to the distal of the osteotomy line in the proximal tibia. Bone stresses (MPa) created by the moment formed as a result of the applied force on the lateral hinge, angle changes (°) and gap distances (mm) in the osteotomy line were recorded. Results: Correction angles were obtained as a result of the forces applied distal to the osteotomy line in the proximal tibia. When the same correction angle was reached, approximately the same lateral cortex bone tensions were obtained in all models. However, when the models under the same force were compared, higher angle changes and gap intervals were obtained in the models osteotomised with high frontal inclination. For example, it was observed that 0.26° correction angle and 1.43 mm gap distance resulted from the model osteotomised with 10° frontal inclination under 5 N force, while 0.35° angle and 1.37 mm gap distance occurred when osteotomy was performed with 22° frontal inclination. Under 75 N force, 10.81° correction angle and 14.02 mm gap distance were observed in the model osteotomised with 10° inclination, while 16.86° correction angle and 19.31 mm gap distance were observed when osteotomy was performed with 22° inclination. Conclusion: When the same degree of correction was reached, we achieved the same lateral hinge tensions in all osteotomy models. However, we observed that when osteotomy is performed more distal tothe joint line in models with the same force applied, higher degrees of correction and gap intervals can be reached. In cases requiring a higher amount of correction, we can say that by keeping the osteotomy starting point more distal to the joint line, we can achieve a faster result. Keywords: Lateral hinge fracture, Medial open-wedge high tibial osteotomy, Lateral cortex fracture, Osteotomy angle in the frontal plane, Finite element analy