Restoration of femoral offset in total hip arthroplasty

Abstract

To explore the factors effecting restoring femoral offset and the relation between femoral offset and hip abductor strength during total hip arthroplasty (THA). Ninety-nine THA for 81 patients were performed from March 1998 to January 2002. And follow-up was finished. There were 53 women and 28 men and the average age was 57 years (29 to 80). The right hip had been replaced in 28 cases, the left in 35 cases and the bilateral in 18 cases. The mean duration of clinical and roentgenographic follow-up was 36.8 months (range, 19 approximately 66 months). A posterolateral approach was used in all THA. The femoral offset and the abductor lever arm were measured from each radiograph. The measurement of the hip abduction strength was made for some THA by the Cybex machine. Statistical data analysis was performed by SPSS10.0 software. Femoral offset correlated positively with the length of the abductor lever arm (r = 0.613; P < 0.001). Simple regression analysis showed that femoral offset was significantly and positively related to the length of femoral neck and neck-shaft angle (r = 0.451, P = 0.001; r = 0.567, P < 0.001). There was a highly significant and positive correlation between femoral offset (and consequently abductor lever arm) and hip abductor strength (r = 0.500, P = 0.009; r = 0.477, P = 0.014). It is very important to template both sides of hip preoperatively for restoring femoral offset in THA. Femoral component with more anatomical neck-shaft angle will be used with the increase in the femoral neck length.