Fig. 4.

Summary of the effects of hibernation on bear cortical and trabecular bone strength, structure, composition, and turnover. Cortical bone properties have been quantified in the femoral midshaft, and trabecular bone properties have been quantified in the distal femoral metaphysis and distal femoral epiphysis (pictured here), as well as in the ilium. In contrast with humans and other animals, bears prevent cortical and trabecular bone loss during disuse. Cortical and trabecular bone remodeling decrease (↓), but bone resorption and bone formation remain balanced in hibernating bears. This likely explains why bone structure (geometry, architecture) and strength are not different (↔) between hibernating and active bears. The decrease in cortical bone turnover probably explains why porosity is decreased and bone mineral content is elevated (↑) in hibernating bears.