MICROCALLUS FORMATIONS OF THE CANCELLOUS BONE - A QUANTITATIVE-ANALYSIS OF THE HUMAN SPINE

Microcallus formations are demonstrable in nearly all spongy bone by m eans of suitable preparation techniques. Histologically, these structu res are immature fibrous bone. Their genesis, frequency, and importanc e are largely unknown. To address these issues, 26 normal human spines , 11 osteoporotic spines, and different parts of the skeleton (femur h ead, iliac crest) were investigated for microcallus using a new prepar ation technique-allowing a combined 2- and 3-dimensional analysis, Acc ording to our analysis, microcallus formation occurs frequently in per sons older than 45 years of age. These formations are mainly localized in the lower thoracic and lumbar spine and are obviously more frequen t in females than in males. In individuals with a trabecular bone volu me (BV/TV) in the spine below 11%, microcallus formations occur regula rly. But the number of microcallus formations depends more on the micr oarchitecture of the cancellous bone (trabecular bone pattern factor, TBPf), than on individual trabecular parameters (trabecular number, Tb N; trabecular bone volume, BV/TV; and trabecular thickness, TbTh), In about 33% of cases microfractures are demonstrable in the center of th e microcallus formation, It is unclear whether microcallus may be the result of a nontraumatic process, In therapy studies the bone mass cou ld be misrepresented due to the amount of microcallus. Although it ind icates instability of the bone structure, microcallus formation is not only a negative mechanism, but stabilizes and regenerates the bone ti ssue. Furthermore, complete new trabeculae can be formed due to bridge s of microcallus between the remnant trabeculae, Osteoporosis is not t he result of an inability to form microcallus formations.