The Effect Of "Y" Line In Reducing The Leg Length Discrepancy After Total Hip Arthroplasty And Its Influencing Factors

Objective:to investigate the effect of "Y" line technique on leg length discrepancy after total hip arthroplasty and the influencing factors of "Y" line technique.Methods:according to the inclusion and exclusion criteria,a total of 300 patients who underwent the first unilateral THA in Qianfoshan Hospital of Shandong Province from June 2017 to July 2020 were selected,including 153 males and 147 females,with an average age of 59.51±11.39 years.Among them,group A used "Y" line technique to control the leg length discrepancy,and group B used unarmed methods such as knee flexion touch measurement,Shuck test measurement and touching tensor fascia lata tension instead of using "Y" line to control the leg length discrepancy.The positive X-ray films of bilateral hip joints were performed in both groups before and after operation,and the leg length discrepancy were measured on postoperative plain films.The following data were recorded in both groups:general data of patients.Age,sex,name,height,weight and data related to operation:the leg length discrepengcy after operation.According to the data collected by the two groups of patients,statistical analysis was carried out.And analyze the causes of postoperative LLD>10mm in group A.Results:(1)the proportion of patients with postoperative LLD greater than 10mm in group A was 5.97%(8/134),14.3%in group B(24/166).The difference between the two groups was statistically significant(chi-square test,P<0.05).(2)The distribution of LLD in group A and group B was better than that in group B,and the difference was statistically significant(chi-square test of grade data,P<0.05).(3)The postoperative LLD in group A was 4.76mm(4.20),5.85mm in group B(4.60),and the difference was statistically significant(rank sum test of measurement data,P<0.05).(4)After analyzing the preoperative and postoperative X-ray radiographs of 8 patients in group A with postoperative LLD>10mm,3 cases were related to the mismatch between the prosthesis and the patient,and 5 cases were related to the nonstandard preoperative hip joint orthographic film shooting.Conclusion:In total hip arthroplasty,The use of rasp holder with "Y" line can control postoperative LLD more effectively than unarmed method.The insufficient internal rotation of the lower extremities and the low projection position in the bilateral hip X-ray film taken before LLD,is an important factor affecting the accuracy of the Y-line technique.