Segmental Uncoverage Ratio Analysis Of Crowe Type-? Developmental Dysplasia Of The Hip Via 3-Dimensional Implantation Simulation

Objective:To study the segmental uncoverage ratio[UCR] of standard cup model placed in true acetabulum of Crowe type-IV developmental dysplasia of the hip via 3-Dimensional[3-D] implantation simulation.Methods:Qualified CT imaging data of 26 patients(30hips)with Crowe type-IV DDH were imported into Mimics software(version 19.0,materialise)and reconstructed,then a 44 mm standard cup model was placed in true acetabulum then replaced by eggshell cup model to evaluate UCRs.We divided the cup into 4 segments by setting acetabular quadrants to measure segmental UCRs.We measured acetabular height by using Matlab software(version 2016,mathworks),and measured acetabular anterior-posterior diameter on 3-D model.Statistic analysis were performed by SPSS software(version 20.0,IBM).Results:Posterior-superior[P-S] segment had the greatest UCR(0.1012±0.0435,95%confidence interval[CI],0.0152 to 0.1914)as well as the most significant positive correlation with total uncoverage ratio[TUCR](pearson correlation=0.889,p < 0.01.Linear regression R2=0.791).Similarly posterior-inferior[P-S] and anterior-superior[A-S] segments showed significant positive correlation with TUCR.Yet,anterior-inferior uncoverage ratio[A-IUCR] showed no correlation with either total or other segmental UCRs.P-SUCR showed significant positive correlation with P-IUCR(pearson correlation=0.644,p <0.01.Linear regression R2=0.415).Acetabular height,A-P diameter showed no correlation with TUCR.Conclusion:P-SUCR contributed the greatest to TUCR as well as had the best correlation with TUCR.A-IUCR was independent of TUCR.There was correlation between P-SUCR and P-IUCR.Thus during surgery we should pay more attention to P-SUCR than A-IUCR,and we need to see the half posterior cup as a whole.A-P diameter didn't affect all UCRs we measured.