Navigated femoral anteversion measurements: a new intraoperative technique

To evaluate and compare the accuracy of using the femoral neck axis and the greater trochanter with navigation to determine femoral anteversion.

Eight human femora with midshaft fractures were used. Real anteversion (AV) values were first measured on a movable fixation system, with digital images imported to software. Second, a navigation system determined the femoral AV with fluoroscopic images of hip, fracture site and femoral condyles. AV I: the centre of the femoral head to the femoral neck axis, the lateral distal femoral condyles and the distal fragment were marked. AV II: the centre of femoral head to the centre of the greater trochanter was marked by the same method.

Actual femoral AV ranged from 1.0 degrees to 9.0 degrees . Head-neck landmarks revealed a mean difference of 1.4 degrees . The greater trochanter-femoral head landmarks revealed a mean difference of 0.3 degrees , significantly less than the head-neck measurements.

Compared with the reliable methods of determining femoral rotation postoperatively, intraoperative measurement is difficult. We found that the centre of the tip of the greater trochanter is easier to identify than the centre of the femoral neck and gives more precise results. This requires analysis of the contralateral limb, which may be feasible with newer non-invasive registration methods.