Objective: The purpose of the present study was to find the anatomical landmarks used as a reference for restoration of the femoral head center in hip arthroplasty patients.
Material and Method: One hundred anterior-posterior digital radiographs of the hip with no magnification were analyzed to measure the correlation between the distance from the center of the femoral head to the most prominent part of lesser trochanter and the femoral head diameter, and the relationship between the level of tip of the greater trochanter and the level of femoral head center.
Results: The authors found the linear correlation between the distance from the femoral head center to the lesser trochanter and the femoral head diameter (Pearson’s correlation coefficient = 0.95) with the average ratio of 1.023. The level of tip of the greater trochanter was found 75% higher than the femoral head center, 15% below the femoral head center, and 10% at the same level. The average level of the tip of greater trochanter was 8 mm above the femoral head center.
Conclusion: The distance from the center of the femoral head to the most prominent part of the lesser trochanter is approximately equal to the diameter of the femoral head. The use of the level of the tip of greater trochanter as a reference point for the level of the femoral head center should be carefully evaluated because of the variability of anatomy.

Keywords: Radiographic measurement, Femoral head diameter, Lesser trochanter, Tip of greater trochanter, Hip arthroplasty, Limb length discrepancy