Spatial mapping of humeral head bone density

Background: Short stem humeral replacements achieve fixation by anchoring to the metaphyseal trabecular bone. Fixing the implant in high density bone can provide strong fixation and reduce the risk of loosening. However, there is a lack of data mapping the bone density distribution in the proximal humerus. The aim of the study was to investigate the bone density in proximal humerus. Methods: Eight CT scans of healthy cadaveric humeri were used to map bone density distribution in the humeral head. The proximal humeral head was divided into twelve slices parallel to the humeral anatomical neck. Each slice was then divided into four concentric circles. The slices below the anatomical neck, where short stem implants have their fixation features, were further divided into radial sectors. The average bone density for each of these regions was calculated and regions of interest were compared using a repeated measures ANOVA with significance set at p<0.05. Results: Average apparent bone density was found to decrease from proximal to distal regions with the majority of higher bone density proximal to the anatomical neck of the humerus (p<0.05). Below the anatomical neck, bone density increases from central to peripheral regions where cortical bone eventually occupies the space (p