Figure 3. Head-neck junction concavity measurements.

The alpha angle was defined as the acute angle between Lines AB and BD. Line AB was formed by connecting the center of the femoral head (Point B) and the point where the cortical surface of the head-neck junction first exited a perfect circle drawn around an ideally spherical femoral head (Point A)²¹; Line BD represented the neck axis. Similarly, beta angle was defined as the acute angle between Lines BC and BD, gamma angle was defined as the acute angle between Lines EF and FH and delta angle was defined as the acute angle between Lines FG and FH.