Longitudinal Density and Volume Changes of Periacetabular Cancellous and Cortical Bone.

Longitudinal structural bone changes within the periacetabular region have potential implications for fracture risk as well implant or arthroplasty fixation within the pelvis. This study presents the first CT-based longitudinal quantitative measurements of bone density and volume in a total of 235 patients. Each patient had a repeat pelvic CT performed > 10 years apart for various indications in South Australia's public hospitals. All slices of each scan were segmented and calibrated with Simpleware software. Cortical and cancellous bone density and volume were measured in defined periacetabular regions of interest. Pelvic bone volume remained constant with increase in age, but the volume of cortical bone decreased whilst the cancellous volume increased. Conversely, the density of cancellous bone decreased whilst cortical bone density increased with age. The patterns of bone loss correlate to bone remodeling due to preferential superomedial loading of the hip. The results also confirm reduced bone density of the anterior column with increasing age in keeping with susceptibility of the geriatric patient to anterior column acetabular fractures. The overall findings show that with time the periacetabular region develops a sclerotic thinner wall, which may be susceptible to fracture and when combined with reduced cancellous bone density potentially less amenable to implant fixation.