Effect Of The Prosthesis Position On Reconstructed Hip Function After Total Hip Arthroplasty

Objective A group of patients who had undergone unilateral total hip arthroplasty were followed up clinically and radiologically to explore the effect of the prosthesis position on reconstructed hip function after total hip arthroplasty and provide a basis to evaluate clinical practice.Patients and Methods A series of 30 patients were followed up. Patients who had any functional ,neurological or morphological disorders affecting gait were not included in this study. Each patient underwent clinical evaluation according to the Harris hip score,and 30 patients were divided into excellent(Harris hip score more than 90 and between 80 and 89) and non-excellent (Harris hip score between 70 and 79 and less than 70) 2 groups. The average Harris hip score of the excellent group which included 22 cases was 88.3,and the average Harris hip score of the non-excellent group which included 8 cases was 66.0. The anteversion angle and the abduction angle of acetabular cup,the migration of the acetabular component,the position of the femoral head center , the femoral offset , the body-weight lever arm , the neck-shaft angle and angulation of the stem were measured from the radiograph , with Osiris419.pc. The results were statistically analyzed by SPSS11.5 ,with a P value less than 0.05 indicating significant difference.Results 1. The non-excellent group had a greater abduction angle of acetabular cup than the excellent group,reached statistical significance. The two groups had similar acetabular anteversion angle and neck-shaft angle. 2. The vertical position of the femoral head center of excellent group was significantly lower than that of non-excellent group;the ratio of operated FO to the BWLA and ratio of operated FO to the unoperated FO in the excellent group were significantly greater than those in non-excellent group. There was no significant difference in horizontal position of the femoral head center between the excellent group and the non-excellent group. 3. The incidence of the migration of acetabular component and stem angulation >3°varus or valgus were not significantly different between the two groups.Conclusion Based on the results of the study , the abduction angle of acetabular cup,the vertical position of the femoral head center,the femoral offset should be considered as the most important factors ,which affect the reconstructed hip function after total hip arthroplasty. We believe that the position of the prosthesis should be controlled appropriately : the abduction angle in the range from 40°to 55°,the anteversion angle in the range from 10°to 20°,the appropriate position of the femoral head center and the appropriate femoral offset.