Distribution of bone mineral density and bone strength of the proximal humerus.

Clinical experience led us to the hypothesis that in the proximal humerus cancellous bone beneath the top part of the head is the strongest and the bone of the humeral neck is the weakest. This hypothesis was examined on dissected proximal humeri with bone mineral densitometry and an indention test. Both dual photon absorptiometry and bone mineral analyses confirmed that the top part of the humeral head was the region with the greatest amount of bone mineral. The humeral neck had approximately one half the bone mineral density of the humeral head. The cancellous bone of the neck had only one third the mechanical strength of the humeral head on the indention test. The high degree of osteoporosis of the neck region increases the difficulty of surgical treatment for displaced humeral neck fractures.