OBJECTIVETo analyze the accuracy of three measurements of lower extremity length during total hip arthroplasty(THA),and explore the causes that influence the accuracy.

METHODSFrom January 2010 to January 2013,145 patients underwent THA were retrospectively analyzed. There were 66 males and 79 females,ranging in age from 48 to 89 years with an average of 66.7 years. Their lower extremities were measured by three methods during operation,among them,31 cases with reference method of contralaterallegs (A method) ,63 cases with measurement method of Kirschner wire location (B method), and other 51 cases with measurement method of anatomical landmark (C method). The accuracy of the three measurements and the incidence rate of length inequality of lower extremity were analyzed.

RESULTSAll patients were followed up,there was no significant differences in the operation time and the intraoperative blood loss among three groups. The difference of lower extremity length with A,B,C method were respectively (8.7+/-5.7),(3.1+/-2.6), (5.6+/-5.3) mm after operation; there were significant difference between any two groups. The accuracy of three methods from high to low were respectively B,C,A method. The incidence rate of length inequality of lower extremity with A, B, C method were respectively 32.3%, 1.6%, 11.8%, the incidence rate with A method was higher than that other two methods ; and there was no significant difference between B method and C method.

CONCLUSIONThe measurement method of Kirschner wire location has the best accuracy in the three methods and the measurement method of anatomical landmark is the second. The measurement method of Kirschner wire location is recommended in all THA except for the patients with femoral neck fracture. And the measurement method of anatomical landmark can be used in the patients with femoral neck fracture.