Hip osseous morphology using computer navigation and plain radiographs

In this study, we used 3-dimensional analysis to comprehensively map the osseous morphology of the acetabulum. Human cadaveric specimens were dissected to the joint capsule for computer navigation analysis. Data points outlining acetabular anatomy-determined using optical sensors-were translated into graphical environments. A clock face template was laid over the transverse plane to determine the projections of acetabular arcs onto the transverse plane. A custom-written software program was used to compute the resulting surface area and was applied to the acetabular articular surface and the fossa. Two independent observers performed all measurements. Sixteen hips were included. Lateral center edge angle was 36.2° and femoral neck shaft angle was 131°. Mean arc lengths of the acetabular fossa from 3 o'clock (anterior) to 9 o'clock (posterior) were 26, 28, 28, 30, 29, 28, and 27 mm at 3, 2, 1, 12, 11, 10, and 9 o'clock, respectively. The smallest aspect of the acetabulum is the anterior aspect, and the largest is the superior (12 o'clock); the size increases progressively from anterior to superior. In most cases, the superior arc length, or sourcil, corresponds to the 2 o'clock position, and thus the lateral center edge angle may not necessarily correspond to the lateral aspect of the acetabulum.