High-Resolution Tomography-Based Quantification of Cortical Porosity and Cortical Thickness at the Surgical Neck of the Humerus During Aging.

Fractures of the proximal humerus are highly related to age and osteoporotic bone remodeling. Previous studies have highlighted the cortex as a major side of the bone loss, but the microstructural changes of the humerus have not been evaluated entirely. Sixty-four (n = 64) humeri of a representative collective (18-100 years) were scanned with high-resolution peripheral quantitative computed tomography (82 µm). Bone mineral density (BMD), trabecular bone volume fraction (Tb.BV/TV), cortical thickness (Ct.Th), and cortical porosity (Ct.Po) were determined with respect to four age groups. The BMD (r = -0.42), Ct.Th (r = 0.57), and Tb.BV/TV (r = 0.68) showed an age group-related decrease, while the Ct.Po increased (r = -0.55). The oldest group (80-100 years) revealed an extensively higher Ct.Po of +87% compared to the youngest group (18-44 years), while the Ct.Th and Tb.BV/TV were significantly lower by -35 and -49% (p < 0.05). The main cortical bone loss occurred after 65 years with the Ct.Th (-34%) and Tb.BV/TV (-40%) being clearly lower and the Ct.Po (+93%) clearly higher compared to the youngest group. In summary, osteoporosis leads to an age-related higher Ct.Po and reduced Ct.Th at the humeral cortex of the surgical neck. The bone loss of the cortex predominantly occurs around the age of 65 years and is very likely to reduce the mechanical strength and highly increases the fracture risk.