Importance of the dome and posterior wall as evidenced by bone density mapping in the acetabulum

BackgroundCharacterizing the distribution of bone density in the acetabulum is of importance in better understanding and guiding treatment for both osteoarthritis and trauma of the hip joint. This study aims to develop a highly automated method to quantify the pattern of subchondral bone density in the acetabulum using clinically identifiable regions.MethodsSubchondral acetabular bone density distribution maps were created bilaterally from 30 non-pathologic pelvic CT scans. The density maps were aligned orthogonal to the acetabular rim plane and divided into twelve zones. Average bone density was calculated in each of these zones and compared to investigate differences between regions within each acetabulum and between right and left sides in a given patient.FindingsIn all patients, the zones corresponding to the dome and posterior wall of the acetabulum demonstrated significantly higher average bone densities than all other regions (P < 0.01). Significant correlations (R = 0.4 to 0.76, P < 0.05) were found between corresponding regions of the left and right sides in 10 of the 12 zones.InterpretationThe pattern of subchondral bone density distribution found in this study is consistent with previously observed bone density patterns in the acetabulum. Correspondence of right and left sides suggests that the distribution of loading on the acetabulum is similar on both sides in healthy individuals, though differences may exist in load sharing. Quantifying bone density patterns using zonal density map analysis may lead to a better understanding of the impact of traumatic injuries and progression of pathologic conditions in the hip joint.