The evaluation of two references for restoring proximal femoral anatomy during total hip arthroplasty

The morphologic features of the proximal femur are used in preoperative planning prior to total hip arthroplasty (THA). In this study we evaluated two references that have been widely used during THA to restore the normal anatomy of the proximal femur: (1) the distance from the lesser trochanter to the center of femoral head and (2) the anatomic relationship between the greater trochanter and the center of femoral head. We used digital photographs to compare 200 cadaveric femora in individuals who died prior to 40 years of age. Preoperative measurement of the distance from lesser trochanter to the center of femoral head from the contralateral hip is accurate to predict the measurement on the operated hip with correlation coefficients (r(2)) of 0.87. The ratio between femoral head diameter and distance from the lesser trochanter to the center of femoral head was consistent and reliable between genders and sides with an average value of 1.01 +/- 0.12. Thus, when the distance from the lesser trochanter to the center of femoral head is not discernible, this ratio can be used as a guide to determine proximal femoral geometry. Conversely, only 59% of the specimens had femoral head centers within 5 mm of the tip of greater trochanter. The correlation between sides of the relationship between the greater trochanter and the center of femoral head was moderate (r(2) = 0.46). Therefore, this relationship should not be used as the sole method to determine the normal anatomy of proximal femur.