Proximal humeral fractures: regional differences in bone mineral density of the humeral head affect the fixation strength of cancellous screws.

The purpose of this study was to investigate the 3-dimensional trabecular bone mineral density (BMD) in the humeral head and determine the effects of trabecular BMD on the pullout strength of cancellous screws. Five regions of interest (ROIs) were defined in the humeral head (superior- anterior, superior-posterior, central, inferior-anterior, and inferior-posterior). The trabecular BMD of each ROI was determined by use of peripheral quantitative computed tomography. Cancellous screws were inserted in each ROI and cyclically loaded. The superior-anterior ROI had a lower trabecular BMD than all other ROIs (P < .001). The central ROI had a higher trabecular BMD than the inferior-anterior ROI (P < .01), whereas no differences were found between the inferior-posterior, superior-posterior, and central ROIs. Pullout strength was lower in the superior-anterior ROI compared with all other ROIs (P < .01). The trabecular BMD and pullout strength were significantly correlated (P < .01). Placement of screws in regions with a higher trabecular BMD may help to prevent implant loosening and may improve patient outcome.