Computed tomography measurement of the accuracy of component version in total hip arthroplasty

The version of the acetabular and femoral components in 111 primary total hip arthroplasties was prospectively evaluated intra operatively by the surgeon and compared with postoperative computed tomography (CT) scan measurements. Intraoperative estimations by the surgeons for acetabular and femoral components were all within 10 degrees to 30 degrees anteversion, with means of 16.0 degrees (SD = 4.0 degrees) and 16.4 degrees (SD = 3.2\degrees), respectively. However, CT scan acetabular measurements ranged from 12 degrees retroversion to 52 degrees anteversion (mean = 22.0 degrees anteversion, SD = 14.0 degrees). Similarly, femoral component version ranged from -15 degrees retroversion to 450 anteversion (mean = 16.8 degrees anteversion, SD = 11.1 degrees). According to CT calculations, only 71% of femoral and 45% of acetabular components were within the expected clinical version range. In conclusion, the intraoperative estimation of acetabular and femoral version in a total hip arthroplasty is of limited accuracy.