Relationships Between The Femoral Neck-preserving Ratio And Radiologic And Clinical Outcomes In Patients Undergoing Total-hip Arthroplasty With A Collum Femoris-preserving Stem

Objective:The femoral neck-preserving ratio is crucial in arthroplas ty with a collum femoris-preserving(CFP)stem.The aim of our study was to analyze the relationships between the neck-preserving ratio and t he short-term radiologic and clinical outcomes of patients who underwen t total-hip arthroplasty(THA)with a CFP stem。Methods:The data of 325 hips from January 2015 to December 2016 were retrospectively reviewed.The demographic and radiologic data before and after surgery were obtained from patients.The neck-preservi ng ratio was defined as the ratio of the preserved femoral neck length t o the preoperative femoral neck length.Correlations between the neck-pr eserving ratio and the radiologic and clinical outcomes of patients were analyzed.Results:The mean neck-preserving ratio was 66.38±6.91%in the c urrent study.We divided patients into 3 groups according to the neck-pr eserving ratio:group A(neck-preserving ratio 60.00%),group B(60.00%<neck-preserving ratio<70.00%),group C(neck-preserving ratio≥70.00%).Radiologic features,including the neck-shaft angle ratio(0.96±0.05),canal fill ratio(0.64±0.07),anterior-posterior offset ratio(1.04±0.10),an d lateral offset ratio(2.55±1.56)(ratios of the postoperative values to the preoperative values),and the prevalence of complications was significant ly different among the groups(x~2=21.173,P<0.001).In the correlation a nalysis,we found a moderate negative correlation between the neck-pres erving ratio and neck-shaft angle ratio(r=-0.308,P<0.001)and a slight positive correlation of the neck-preserving ratio with the anterior-posterio r offset ratio(r=0.415,P<0.001)and the lateral offset ratio(r=0.164,P=0.003).In the linear regression analyses,the neck-preserving ratio was s ignificantly linearly correlated with the neck-shaft angle ratio(B=0.232,95%confidence interval[CI]=-0.311to-0.154,P<0.001),anterior-posterior of fset ratio(B=0.589,95%CI=0.447–0.730,P<0.001),and lateral offset ra tio(B=3.693,95%CI=1.256–6.131,P=0.003).However,there was no si gnificant linear correlation between the neck-preserving ratio and the can al fill ratio(B=0.073,95%CI=-0.033 to 0.180,P=0.174).Logistic regressi on analyses also showed that a sufficient neck-preserving ratio was a pr otective factor for periprosthetic femoral fractures(odds ratio[OR]=0.924,95%CI=0.859–0.994,P=.035),dislocations(OR=0.892,95%CI=0.796–0.999,P=0.048),and thigh pain(OR=0.886,95%CI=0.818–0.960,P=0.003).Conclusions:For CFP stems,an insufficient neck-preserving ratio i s significantly correlated with poor radiologic and clinical outcomes.The refore,surgeons should be cognizant to preserve an enough femoral nec k length during surgery to improve the outcomes for patients undergoin g THA with CFP stems.