The Clinical Changes And Influencing Factors Of Leg Length After Total Hip Arthroplasty

Objective:A group of total hip arthroplasty were followed up to investigate the clinical changes of leg length,then get the rate of LLD. In order to improve the consistency of the leg lengththe, relevant factors which may led to LLD were analysised.Methods:A series of117patients (152hip joints) from January2009to June2011were followed up routinely. Before the operation there were35cases whose lower limbs were defined as the equal length,82cases were unequal length.The artificial joint of all cases were cementless prosthesis.The leg length before and after the operation(within a week) were measured, and the leg length discrepancy after total hip arthroplasty were calculated. Leg length discrepancy less than or equal10mm were regarded as equal length.All postoperative measurement within1week were measured on hip anteroposterior X-ray film. The measurement after THA which were the leg length, the reserved calcar length, the length of calcar-prosthesis intersection to the prosthesis remote, the width of prosthesis atcalcar-prosthesis intersection perpendicular to the femoral shaft longitudinal axis, the vertical distance and horizontal distance from the acetabular center of rotation to the ipsilateral teardrop connection, theeccentric moment of the hip prosthesis, the angle of the prosthesis-femoral neck-shaft, the distance of the hip center of rotation to the base of prosthesis neck. The length of the femoral head prosthesis neck which were implanted in patients were counted based on implant labels within Medical Records. The measured and counted data grouped by different postoperative lower limb length, and the various sets of data were analysised using statistical methods to detect whether there exist differences between the various groups.Results:In all the117cases(152hips), there were116cases whose lower limbs were equal length,among which108cases(92.31%) whose lower-limbs’discrepancy were0mm,5cases(4.27%) whose LLD’s range were in5mm,and3cases (2.56%) were5mm～10mm.There were1case whose leg length difference is11mm.1case complaint about the operative side lower limb longer than the contralateral limb.All cases LLD’s mean±standard were0.46mm±1.83mm, harris hip score’s mean±standard were74.43±12.40.Between the various postoperative lower limb length groups, the statistical analysis showed that after THA there were statistically significant in the reserved calcar length, in the length of calcar-prosthesis intersection to the prosthesis remote, and in the vertical distance from the acetabular center of rotation to the ipsilateral teardrop connection. There were no statistically significant in the width of prosthesis at calcar-prosthesis intersection perpendicular to the femoral shaft longitudinal axis, in the length of the femoral head prosthesis neck which were implanted in patients, in the horizontal distance from the acetabular center of rotation to the ipsilateral teardrop connection, in the eccentric moment of the hip prosthesis, in the angle of the prosthesis-femoral neck-shaft,in the distance of the hip center of rotation to the base of prosthesis neck. Between the various postoperative lower limb length groups, within1week, there were no statistically significant in the harris hip score.Conclusion:Factors that affect the postoperative leg length after THA are the reserved calcar length, the length of calcar-prosthesis intersection to the prosthesis remote, and the vertical distance from the acetabular center of rotation to the ipsilateral teardrop connection. They are the important intraoperative measures to adjust limb leg length. The various intraoperative methods of measuring leg length can significantly reduce the incidence of postoperative leg length discrepancy.