Posterior lesser trochanter line should not be used as reference for assessing femoral version in CT scans: a retrospective reliability and agreement study.

Background The estimation of femoral version in preoperative planning of total hip arthroplasty and to assess complications after total hip arthroplasty is crucial. Recent studies have recommended the posterior lesser trochanter line as an intraoperative reference for estimating femoral version. We hypothesized, that if there is a correlation, the posterior lesser trochanter line could be used to assess femoral version in computed tomography (CT) scans. Purpose To evaluate the correlation between the posterior lesser trochanter line and the posterior femoral condyle axis. Material and Methods CT scans of 126 patients after unilateral total hip arthroplasty were analyzed by means of a newly developed digital planning software for CT scans. Both hips were measured, the angle between the posterior lesser trochanter line and the posterior femoral condyle axis was determined, and the relationship between both lines was evaluated. Results We found significant differences between male and female patients ( P < 0.001) and between left and right femora ( P = 0.001). There was no significant difference between healthy hips and hips with osteoarthritis after total hip arthroplasty ( P = 0.901). Conclusion There is no reliable correlation between posterior lesser trochanter line and posterior femoral condyle axis. Therefore, posterior lesser trochanter line should not be used to assess femoral version in CT scans. As a consequence, the gold standard for measuring femoral version should still be a three-dimensional CT scan of the whole femur.