To evaluate the accuracy and reliability of method for prediction of rotationally neutral state of the femur by comparing with contra-lateral lesser trochanter.

The rotationally neutral state of the femur was measured by comparing the shape of the opposite side of the lesser trochanter in a normal group of 100 adult. Each examination was performed independently by three observers. The observers predicted a position presumed to be neutral by comparing the shape of lesser trochanter with that of contra-lateral side previously recorded by the C-arm image intensifier. We evaluated the mean angular discrepancy that is different from the neutral point and assessed the inter-observer variations.

The mean angular discrepancy (SD) was 3.4 degree(±2.4); 3.5 degree(±2.4) by observer-1,3.5 degree (±2.8) by observer-2, 3.2 degree(±2.2) by observer-3. There was no inter-observer variation (p=0.87). 77% of all observers indicated below 4 degree and no one over 15 degree.

The method of comparing the shape of both lesser trochanters is considered to be effective in determining the rotational status of the femur. It could be used as a practical method in the operation of the femoral fracture for prevention of rotational deformity intra-operatively