[Enlargement of the femoral marrow cavity with aging]

Bone resorption and bone formation occur throughout life. We measured CT film from the femora of human subjects and studied how remodeling change affected the size of marrow cavities in long bones. In total of 448 subjects using the right femora ranging in age from 16 to 95 years, 293 males and 155 females were studied. The part measured was the upper one-forth of the femora. A positive correlation in regards to age, circumference, and area of marrow cavities was demonstrated in male and female subjects (p < 0.001). Marrow cavities were found to grow with age. The percentage of growth in marrow cavities was greater in female subjects than in male subjects. However, the rate of marrow cavity enlargement with age differed in male subjects compared with female subjects. We grouped our data into three categories: group 1 (under 40 years), group 2 (40-60 years), and group 3 (over 60 years). We found a large difference between group 2 and group 3 of male subjects. This difference suggests that a reduction in bone volume with age affects bone marrow enlargement. A large difference in females between group 1 and group 2 was noticed, but a difference in females between group 2 and group 3 was not observed. In female subjects, change in marrow cavity enlargement occurred in subjects in their 40's and 50's. We speculate that the reason for enlargement of the bone marrow in subjects in their 50's is due to a reduction of bone volume after postmenopausal change.