Preoperative Planning Of Circumacetabular Circumferential Osteotomy

Hip dysplasia is a common bone and joint disease in adolescents and adults.The center of the acetabulum hip joint and the center of the femoral head in normal persons approximately coincide.Due to the development defect of the acetabulum,the depth of the acetabulum becomes shallower and the slope becomes larger,so that the contact area between the femoral head and the acetabulum becomes smaller and smaller.The stressed area between the acetabulum and the femoral head decreases,and the peak contact stress increases,resulting in stress concentration.Stress concentration can cause excessive wear and tear of the articular cartilage,damage the articular cartilage,reduce the space between the joints,and eventually develop into osteoarthritis of the hip.Arc periacetabular osteotomy is a new method for the treatment of hip dysplasia.At present,there is no tool or method that can provide accurate reference for doctors to rotate at the appropriate Angle in China.The success rate of surgery generally depends on doctors' clinical experience,which brings great uncertainty.In order to solve these problems,the present study firstly constructed a complete pelvic finite element model by three-dimensional reconstruction of Computed tomography scans(CT)data.The model was endowed with material properties that were most similar to cortical bone,cancellous bone and cartilage,and ligaments and muscles were added to make the model as close to reality as possible.Then,the osteotomy was simulated in the software,and the different angles of rotation required during the operation could be simulated by rotating the acetabular mass.Rotate the Angle of the femur to simulate gait movement.Finally,force was applied to the center of femoral head to complete the establishment of the model.The contact area and contact pressure of the acetabular block and the femoral head were compared at different angles of rotation to determine the best Angle of rotation of the acetabular block,so as to provide reference for doctors and achieve the function of preoperative planning.The study drew the following conclusions:(1)The modeling and simulation method used in this paper is effective.(2)Modeling only the hip bone and femur on the affected side can misjudge the size and location of the stress concentration.By comparison,the results obtained by modeling the complete pelvis and femur are more accurate and reliable.(3)When selecting the optimal rotation Angle of acetabular bone block,it is more beneficial to determine the optimal rotation Angle by considering the influence of various factors,such as acetabular deformity and lesion area.(4)According to the data obtained by comparison,the peak value of contact stress between acetabulum and LCEA is the smallest when the size of LCEA and ACEA is between 35 ° and 40°,regardless of the five stages: heel landing phase,beginning of single leg support phase,middle phase of single leg support phase,end phase of single leg support phase,and double leg support phase.Therefore,after comprehensive analysis of various factors and comparative data,35° for LCEA and 35°for ACEA were finally determined as the optimal Angle for acetabular bone block.