The popliteal surface axis may define hip anteversion

OBJECTIVES: This study aims to investigate the usability and reliability of our new axis in a three-dimensional modelling work and demonstrate if it is a reproducible method for anteversion measurement that sufficiently correlates with other computed tomography (CT)-derived gold standards including trans- epicondylar axis (TEA) and posterior condylar axis (PCA). PATIENTS AND METHODS: Three-dimensional solid models were derived from left femoral CT data of 100 participants (50 males, 50 females; mean age 57 years; range, 21 to 86). The newly proposed popliteal surface axis (PSA) was compared with TEA and PCA in terms of anteversion measurement on these solid models. RESULTS: Popliteal surface axis was found as a reproducible reference axis in our study as it could be measured in 99% of our sample. The mean value of PSA based anteversion was (-) 1.8° which was 10.7° and 4.4° for PCA and TEA, respectively. Popliteal surface axis was perfectly correlated with PCA and TEA for anteversion measurements (p<0.001, r=0.92 for both). CONCLUSION: Our findings suggest that the newly defined PSA may be used as an alternative method for determination of anteversion.