Patterns of Acetabular Femoral Head Coverage 2011-22-0018
The size and shape of the acetabulum and of the femoral head influence the injury tolerance of the hip joint. The aim of this study is to quantify changes in acetabular cup geometry that occur with age, gender, height, and weight. Anonymized computed tomography (CT) scans of 1,150 individuals 16+ years of age, both with and without hip trauma, were used to describe the acetabular rim with 100 equally spaced points. Bilateral measurements were taken on uninjured patients, while only the uninjured side was valuated in those with hip trauma. Multinomial logistic regression found that after controlling for age, height, weight, and gender, each 1 degree decrease in acetabular anteversion angle (AAA) corresponded to an 8 percent increase in fracture likelihood (p≺0.001). Age, weight, and gender were found to influence anteversion angle significantly, with each 10 years in age increasing AAA by 1.07 degrees, each 10 kg of weight decreasing AAA by 0.45 degrees, and being female resulting in 1.42 degrees greater AAA than males. Height was not found to relate significantly to AAA after other anthropometric factors were controlled for. Height, age, and weight, however, correlated with femoral head radius, thus establishing a relationship with acetabular rim size independent of rim shape. A parametric model of the 3D acetabular rim landmark points is reported, allowing for the creation of individualized acetabular geometry for any given age, gender, height, and weight. A custom-built tool to produce such geometry programmatically is also provided.