Coordinate value of the femoral head center estimated using those of the tip of the greater trochanter and lesser trochanter.

Several studies have reported estimating the femoral head center (FC) from reference points on the pelvis; however, none have reported estimates obtained from those on the femur. In this cross-sectional study, we investigated the estimated point of FC from the coordinate value of the tip of the greater trochanter (GT) and lesser trochanter (LT) using a formula with a three-dimensional measurement technique. We used data from 92 healthy Japanese subjects without any back or knee symptoms and no abnormalities in the hip, knee, or spine on plain radiographs. In our study, the difference in the anteroposterior direction was larger than that in the other directions. We speculate that the accuracy of defining the tip of the LT is difficult in the anteroposterior direction. Moreover, the correlation coefficients were larger for women. The reason for this was unclear because the variation in the proximal femur may be similar in women. We found that the average difference between the actual and calculated values was approximately 2 mm. We considered that the coordinate value of the FC from the tip of the GT could be estimated more accurately using the regression equation compared to previous methods based on pelvic reference points.