Changes in scapular bone density vary by region and are associated with age and sex.

Background: Decreases in bone density of the scapula due to age and disease can make orthopedic procedures such as arthroplasty and fracture fixation challenging. There is limited information in the literature regarding the effect of age and sex on the patterns of these density changes across the bone. Characterizing these changes could assist the surgeon in planning optimal instrumentation placement.

Methods: Ninety-seven 3-dimensional models of the scapula were segmented from routine clinical computed tomography scans, and an opportunistic quantitative computed tomography approach was used to obtain detailed calibrated bone density measurements for each bone model. The effects of age and sex on cortical and trabecular bone density were assessed for the entire scapula. Specific regions (eg, scapular spine) where these factors had a significant effect were identified. Three-dimensional models were generated to allow clear visualization of the changes in density patterns.

Results: Cortical bone loss averaged 1.0 mg/cm and 0.3 mg/cm per year for female and male subjects, respectively, and trabecular bone loss averaged 1.6 mg/cm and 1.2 mg/cm, respectively. However, several regions had loss rates several times greater. Areas that were significantly affected by age included the acromion, scapular spine, base of the coracoid, inferior glenoid neck, and glenoid vault. Areas that were significantly affected by sex were the scapular spine and body.

Conclusions: These findings provide evidence that the bone density distribution across the scapula changes non-uniformly because of factors including sex and age. Despite overall trends of bone loss, there remains significant variability between individuals, and subject-specific tools for planning surgical procedures in which scapular fixation is required may be beneficial.