Three-dimensional Finite Element Analysis Of The Stress Distribution In Periacetabular Osteotomy Area Of The Children With DDH

BackgroundDevelopment dislocation of the hip (DDH) is a common disease in pediatricdepartment of orthopedics, which is high incidence, high morbidity but can be cured. Ifthe conservative treatment is invalid, the children will need operation treatment to getfemoral head and acetabulum concentric relationship. Making clear children’s pelvisbiomechanics of DDH can guide the design and evaluation of operation scheme. Thestructure of pelvis which is with irregular shapes and composition is complex. The stress,strain and biomechanical analysis of pelvis are difficult to use the traditional experimentalto study. The traditional research methods used in biomechanical study include clinicalobservation and cadaveric, the former is difficult to control and obtain limited information,which need more samples to control the differences among individuals; the latter isexpensive for the high requirements of experimental equipment and technology. As a newbiomechanical research method, three-dimensional finite element method has theadvantages of low cost, comparable advantages, access to comprehensive information. Therefore, to establish an effective finite element model of DDH of children’s pelvis hasimportant significance in the design and evaluation of operation scheme of DDH.ObjectiveEstablish the3D digital model of children with DDH. Simulate the periacetabularosteotomy operation based on the children’s DDH3D digital model,3D digital model andfinite element model is built after the operation.. we used the result of the Biomechanicalanalysis of the finite element model to guide the establishment of acetabular osteotomyand bone grafting.MethodBased on CT images of children’s unilateral DDH, we employ the Mimics11.0software for modeling, Geomagic10.0software for model optimization and Hypermesh10.0for finite element meshing. The material properties are given by mechanical materialproperties of the anatomical hip and hip articular cartilage, cortical bone, cancellous boneand ligament. Establish the analysis model of hip joint dislocation of children’s DDH forAnsys software. Through the analysis of mechanics of dislocation acetabulum side withthe normal hip joint before surgery, using the analysis method of finite element linear faceto face contact to analyse bilateral force of preoperative acetabular judgment. Use thesimulation module of Mimics software to simulate the operation, around hip acetabularosteotomy operation, which changed in CE angle setting into the bone block thickness,depth. Simulation operation to establish7different postoperative hip joint models andmechanical analysis of acetabulum, the three-dimensional finite element model of theacetabulum and the area around the stress magnitude and distribution on the basis of themodel, mechanical distribution evaluation of the best sites osteotomy and bone grafting.ResultThe study established the finite element analysis model of children with DDH. Wesimulated the operation to got the post operation model and had the finite element analysison the model. The normal acetabular uniform stress distribution with single leg standingshow that the acetabulum had no stress concentration point and dislocation of lateral stressconcentration at the rim of the acetabulum and femoral head and acetabular contact part, acetabular edge stress is higher than that of acetabulum center stress. Comparison ofpreoperative and postoperative model model under the single leg standing condition, theacetabulum and femoral head stress distribution near the normal side when the CE anglefrom24°to33°, the stress concentration region shifted from the acetabular rim center;With the condition of stand on two legs, the acetabulum and femoral head stressdistribution is close to normal side when the CE angle from24°to30°, in which the24°CE angle is the best. By comparing7groups post operation models, acetabular bestmatching after operation and uniform stress distribution when the CE angle from24°to30°, which is conducive to children’s femoral head and acetabular development and caneffectively reduce the acetabulum and the femoral head bad stress load.ConclusionEstablishment of three-dimensional finite element model of DDH of hip joint inchildren can provide digital reference for children’s DDH mechanics research andoperation treatment. Periacetabular osteotomy for DDH can effectively improve theacetabulum and the femoral head of the contact stress. The correct choice of periacetabularosteotomy area bone sites can make hip acetabular the best matching and uniform stressdistribution.