3D Finite Element Analysis Of Acetabular Component In Patients Of Crowe Ii-type Acetabular Dysplasia Treated By THR And Clinical The Case Reports

Objective:1. To analyse the mechanical stability and the stress distribution characteristics ofthe acetabular component with two diameter in the patients with late Crowe II-typedevelopmental dysplasia of the hip (DDH) by using the finite elementmethod(FEM),and to provide a reference for clinical hip replacement.2. A retrospective analysis was done on cases of total hip replacement(THR) intreating Crowe II-type DDH in the past5years in our hospital to evaluate theclinical efficacy.Methods:Patients with Crowe II-type DDH were selected and undergone the pelvicthin-section CT scan.The scan data was imported and reconstructedthree-dimensionally by Mimics10.01software and the three-dimensional(3D) finiteelement model of both ipsilateral and contralateral hip joint was built by using finiteelement analysis(FEA),software ABAQUS6.11. The preoperative stress distributionand displacement of the ipsilateral acetabular bone was achieved by using FEM bothin the state of simulant slow walking with one foot on ground and setting theboundary and loading conditions. Then the3D finite element model of the hipprosthesis was established by simulating THR.Through this method, thepreoperative true acetabulum diameter could be measured,according to which wasthe prosthetic acetabular cup(small cup) replaced and the large cup simulationallyreplaced respectively.In the end, the two prosthetic acetabular cup were analysed byFEM, the stress distribution of the acetabular prosthesis lining and the acetabularcomponent displacement were compared physiologically.A total of19patients(21hips) with Crowe II-type DDH who had undergone the THR were retrospectively surveyed in our hospital from Jun.2006to Oct.2011.There were5males and16females, aged from37to68years(mean,53years),withinwhom had2patients bilateral dysplasia and19patients unilateral. The mainsymptoms of them were pain and limping. The preoperative Harris score was30.49±3.2. There were15small cup replacements and6large cup replacements in21cases, bone grafting was carried out when the cover less than80%.There werethree groups:large cup replacement group,small cup replacement group,small capreplacement with bone grafting group. Harris score, follow-up X ray review andwhether there was loosening or dislocation of the acetabular prosthetic cup werecompared and analysed statistically among there groups in3months,6months,1yearand2years. The causes of postoperative recovery of joint function were analysedand compared by statistical methods of T test.Results:1.According to the data collected by thin-section CT scan,the3D finite elementmodle of ipsilateral and contralateral hip joint in adult Crowe II-type DDH functionas a replica by which we could analyse the stress distribution around the hip jointpreoperatively and postoperatively.The stress of normal and acetabular dysplasiausually distributed at the highest point of femoral head and the correspondingacetabular cartilage of the top dome, and the acetabular cartilage regional is wherethe higher stress distributed.In the normal side of the hip Von Mises stress of theweight-bearing area of the femoral head cartilage above the peak of2,105MPa, andthe acetabular cartilage top dome ministry of peak Von Mises stress of2.224MPa,and stress is mainly concentrated in the acetabular hip dysplasia side, the outeredge of the local stress reaches1.5-2times the normal side. Small prostheticacetabular replacement, lined with the Von Mises stress range distribution is morehomogeneous, mainly concentrated in the central area and outside the top peak1.970MPa, small prosthetic acetabular cup, less stress, only the front and on theDistrict scattered in the stress zone, the highest peak value2.986MPa small cupreplacement pelvic stress distribution performance out above the peak of2,936MPa, the peak stress of the femoral trochanter and the head and neck were2.98MPa and2.949MPa; large prosthetic acetabular replacement: lined with Von Mises stressdistribution in the lining most of the peripheral edge of the peak2.355MPa. Largeprosthetic acetabular cup stress concentration at the edge and the rear of the cup,peak7.415MPa, femoral stress distribution in the trochanter and neck, peaks3.140MPa pelvic stress distribution in the acetabular rim after lateral peak6.180MPa. Comparing lining large cup replacement stress increased by19.54%,40.27%increase in large prosthetic acetabular cup stress, pelvic stress increased by110.49%. The trochanteric stress makes no significant difference. Preoperativepelvic displacement of7.150, the simulation of a small cup replacement afterpelvic displacement is2.170, a more even distribution of large glass replacementpelvis displacement2.007, mainly concentrated in the acetabulum.2. All patients were followed up for6months-5years after surgery,with anaverage of3years and2months, a postoperative wound healing.There was noloosening of the prosthesis, dislocation phenomena.1case in small cup got walkingpain but released after6months.1year after3cases of cup arthroplasty in patientswith mild claudication, can achieve e a long distance walking.After2years,1large cup replacement patients could alleviate without taken time to time oralanalgesics. Other cases were satisfactory, no significant pain, limp, and can walklong distances.These patients were divided into three groups, large-cuparthroplasty Harris hip score were as follows:94.38±3.2,90.18±1.6,86.11±2.3,78.24±2.8after3months,6months,1year and2-year.Grafting small cupgroup Harris hip score were91.70±3.4,94.38±1.6,93.08±4.2,90.18±3.2after3months,6months,1year and two years,; Non-grafting Cup group Harris score were95.21±1.7,94.00The±3.4,93.28±1.6,90.46,±2.2after3months,6months,1year and2years.There is a significant difference between the large cupand the small cup+bone graft, large cups and small cups+bone graft group (P<0.05), small cup+bone graft group and the small cup without planting bonegroup were not significantly different (p>0.05), analysed by SPSS16.0.X-rayshowed that there was no lighting area, loosening and sinking around the acetabular component.Conclusion:THR treatment of adult acetabular dysplasia Crowe II-type DDH trumpetprosthetic acetabular cup around the hip joint stress and acetabular prosthetsisdisplacement has advantage over lage prosthetic acetabular cup,which is conduciveto long-term hip prosthesis stability.