Cortical and cancellous bone: age-related changes in morphologic features, fluid spaces, and calcium homeostasis in dogs.

The changes in cortical and cancellous bone that occur with aging were studied by measuring morphologic and physiologic variables for both types of bone in dogs. The percentage area of cortical and cancellous bone, rate of bone formation, vascular volume, bone water, and volume of distribution of calcium tracer all showed statistically significant changes at the time of bone maturity. Canine cortical bone cell volume progressively decreased with advancing age, and cancellous bone cell volume significantly decreased between adult and old dogs. The volume of distribution technique can be used to determine the relative contributions of cortical and cancellous bone to the total body exchangeable calcium ion pool.