Anisotropy of osteoporotic cancellous bone

Abstract

To investigate the mechanism underlying femoral neck fracture, it is necessary to determine the various mechanical properties, including the bone strength, of the primary compressive group. We investigated the mechanical anisotrophy of the primary compressive group by comparing differences in its mechanical properties, depending on the loading direction. Twenty-three femoral heads of 20 female and 3 male patients with femoral neck fracture were studied. The mean age of these patients was 79.9 years (range, 63-98 years). A total of 82 cubic specimens (6.5 mm in length) were obtained (one to six specimens from each femoral head). The specimens obtained from each femoral head were randomly assigned into two groups: parallel and perpendicular. The parallel group included 43 specimens, and the perpendicular group included 39 specimens. A compressive load was applied either parallel or perpendicular to the primary compressive group of the specimens in each respective group. Three parameters were obtained: compressive stiffness, maximum stress, and maximum energy. We calculated the regression of three parameters against the square of the apparent dry density. These mechanical properties were compared between the two groups by testing the difference of the slopes in two regression lines by using analyses of covariance, in which two main effects of group (nominal value) and the square of the apparent dry density (continuous value) and an interaction between two factors were modeled. Three parameters were significantly correlated with the square of the apparent dry density in both groups. In all three measurements, the difference of the slopes between two regression lines was significantly different. This means that all three measurements decreased in the parallel group more than in the perpendicular one, as apparent dry density decreased. We consider that the bone strength of the proximal femur decreases more when stress is applied in the longitudinal direction (as in walking) and less when stress is applied in the transverse direction (as in a fall) when bone density decreases.

Diffusion tensor imaging and magnetic resonance spectroscopy assessment of cancellous bone quality in femoral neck of healthy, osteopenic and osteoporotic subjects at 3T: Preliminary experience

“…We may hypothesize that with the development of the osteoporosis the environment probed by water restricted between fat and bone becomes more isotropic due to the structural rearrangement of the endosteum cell lines or of the trabeculae surface. On the other hand, using a different length scale of the order of millimeters, trabecular bone anisotropy increases with osteoporosis, as well documented in literature [48,49]. Our findings suggest that, with the development of osteoporosis, both of these mechanisms occur, at different length scales.…”

Application of micro-ct assessment of 3-d bone microstructure in preclinical and clinical studies

“…Anisotropy is constituted under the influence of strengths applied to bone and permits establishing resistance to these strengths in a given preferential direction. Sugita et al [16] observed variations in bone strength following the loading directions. These variations were interpreted as an anisotropic feature of the bone strength, and trabecular anisotropy might be considered to predict the fracture risk.…”

“…An important microarchitecural property of trabecular bone is the anisotropy of the structure, defined by the existence of preferential direction(s) in the trabecular organization. Anisotropy of trabecular bone tissue primarily involves the preferential orientation(s) of trabeculae and is also reflected by the oriented values of bone strength [16]. Anisotropy is constituted under the influence of strengths applied to bone and permits establishing resistance to these strengths in a given preferential direction.…”

Effect of oligofructose or dietary calcium on repeated calcium and phosphorus balances, bone mineralization and trabecular structure in ovariectomized rats

“…Mineral content was analysed in femora and lumbar vertebrae as representing predominantly cortical and trabecular bone, respectively. Furthermore, these bones are characterised by different physical loading and mechanical anisotropy (Sugita et al 1999), which may be important factors for determining the target of mineralization. The hypothesis was that oligofructose impedes ovariectomy-induced loss of bone mineral content and preserves bone architecture due to stimulated apparent Ca absorption.…”