The Treatment Of Chiari Pelvic Osteotomy For Developmental Dysplasia Of The Hip In Older Children

Part One The Clinical Application of Chiari Pelvic Osteotomy in the Treatment of Developmental Dysplasia of the Hip in Older ChildrenObjcetive:To discusse and analyze the clinical application of Chiari pelvic osteotomy in the treatment of developmental dysplasia of the hip in older children.Methods:Retrospective analysis was perfromed for 18 patients(20 hips)undergoing Chiari pelvic osteotomy in Children’s Hospital of Soochow University from January 2016 to December 2020.The clinical and imaging morphological evaluation were performed before operation and at postoperative follow-up.The clinical evaluation was performed by using the Harris hip score.The imaging morphology was evaluated by Severin hip X-ray rating at the last postoperative follow-up.The Preoperative and postoperative imaging datas were collected,imaging parameters were measured,including acetabular index,Wiberg’s central edge CE Angle,Sharp Angle,acetabular coverage,femoral neck shaft Angle,and skeletal leg length.Results:18 patients(20 hips)were followed up for an average of 21(859)months.There were 2 boys and 16 girls.There were 7 cases on the left side,9 cases on the right side,and 2 cases on both sides.The average preoperative Harris hip score was(59.4±10.9)points,and the final postoperative follow-up Harris hip score was(87.4±7.2)points,including 8 hips were excellent and 9 hips were good,with an excellent and good rate of 85%.According to Severin hip X-ray rating at the last postoperative follow-up,2 hips were excellent and 15 hips were good,with an excellent and good rate of 85%.The acetabular index,CE Angle,Sharp Angle and acetabular coverage rate were significantly improved in the last follow-up compared with preoperative ones,and P value<0.05 was used for T-test,the difference was statistically significant.Conclusion:Chiari pelvic osteotomy is an effective surgical method for the treatment of older children with developmental dysplasia of the hip,which can effectively increase the inclusion of the acetabulum to the femoral head and the stability of the hip joint.The postoperative clinical symptoms and imaging morphology are significantly improved.Part Two The Finite Element Analysis of the Biomechanics Effect of the Angle of Osteotomy Line and Degrees of Internal Displacement on the femoral head in Chiari Pelvic OsteotomyObjcetive:To investigate the biomechanical effects of different angle of osteotomy line and degrees of internal displacement on the force of femoral head by using the finite element analysis method and establishing the digital virtual model of Chiari pevic osteotomy.Methods:The hip CT scan images of an older children with developmental dysplasia of the hip was exported in DICOM format.Mimics 19.0 software was used to build the model of image data,and UG12.0 and Abaqus2018 software were used to build the three-dimensional finite element model of Chiari pelvic osteotomy.The nonlinear contact pressure analysis method was used to observe the stress distribution of femoral head with different angle of osteotomy line and degrees of internal displacement.Results:The Von Mises stress on the interface between the femoral head and the acetabulum decreased gradually with the increase of the degree of internal displacement under the same Angle osteotomy line in the condition of standing on both legs.The Von Mises stress on the femoral head decreased obviously before the degree of internal displacement was 40-60%,and then tended to be flat after 40-60%.The Von Mises stress of femoral head was the lowest when osteotomy line was 10-15°under the same degree of internal displacement.Conclusion:The Angle of osteotomy line and the degree of osteotomy can be designed in advance through finite element analysis before Chiari pelvic osteotomy,so as to make full preparation for patients to obtain satisfactory results.Under the condition of stable internal fixation,the osteotomy line of 10-15°and the degree of internal displacement of 40-60%are more appropriate choices for Chiari pelvic osteotomy,which can effectively change the negative gravity line of the body and reduce the load per unit area of the femoral head,so as to achieve a relatively satisfactory clinical effect.