The Impact Of Proximal Femoral Shape On Leg Length Discrepancy After Total Hip Arthroplasty

Objective: There are many reasons for leg length difference(LLD)after total hip arthroplasty,but it has been rarely reported whether LLD is related to the morphology of the proximal femur,especially the femoral cortical index.So we investigate the effect of different proximal femoral shapes on leg length discrepancy after total hip arthroplasty.Methods: A total of 131 patients with osteoarthritis of the hip or necrosis of the femoral head who received unilateral biological total hip arthroplasty in our hospital from June2013 to June 2019 were selected.We retrospectively analyzed age,sex,side,and pelvic radiographs.There were 69 males and 62 females,57 cases of left hip and 74 cases of right hip.The age ranges from 25 to 89,with an average age of 62.There were 48 cases of osteoarthritis and 83 cases of osteonecrosis.In this study,femoral cortical index(FCI)is used as the classification of proximal femoral shape,and bilateral lower limb length differences are measured by preoperative and postoperative pelvis anteroposterior digital radiography.According to FCI and LLD,the general information of patients and LLD were statistically analyzed and compared for each cohort.One-way ANOVA and Kruskal-Wallis test were used to determine the relationship between proximal femur morphology and the different length of lower limbs after total hip replacement.Results: The postoperative average FCI was(0.56±0.08)mm and LLD was(4.53±6.73)mm.Three groups were divided according to the level of FCI,and there were no statistically significant differences in gender,age,side,diagnosis and intraoperative fracture rate distribution between each group.FCI>0.6,the average postoperative LLD was(6.24±6.14)mm.When FCI was 0.5～0.6,the postoperative LLD was(4.72±6.91)mm on average.FCI< 0.5,the average postoperative LLD was(1.81±6.41)mm.The difference between FCI and LLD was statistically significant(P<0.05).Conclusion: High FCI increases the risk of lower extremity prolongation,while low FCI reduces the risk of lower extremity prolongation.Surgeons can evaluate the proximal femoral shape of patients preoperatively,and estimate the possibility and risk of LLD after THA.