Increase in bone volume fraction precedes architectural adaptation in growing bone

Abstract

In mature trabecular bone, both density and trabecular orientation are adapted to external mechanical loads. Few quantitative data are available on the development of architecture and mechanical adaptation in juvenile trabecular bone. We studied the hypothesis that a time lag occurs between the adaptation of trabecular density and the adaptation of trabecular architecture during development. To investigate this hypothesis we used ten female pigs at 6, 23, 56, 104, and 230 weeks of age. Three-dimensional morphological and mechanical parameters of trabecular bone samples from the vertebra and proximal tibia were studied using microcomputed tomography and micro-finite element analysis. Both bone volume fraction and stiffness increased rapidly in the initial growth phase (from 6 weeks on), whereas the morphological anisotropy started increasing only after 23 weeks of age. In addition, the anisotropy reached its highest value much later in the development than did bone volume fraction. Hence, the alignment of trabeculae was still progressing at the time of peak bone mass. Therefore, our hypothesis was supported by the time lag between the increase in trabecular density and the adaptation of the trabecular architecture. The rapid increase of bone volume fraction in the initial growth phase can be explained by the enormous weight increase of the pigs. The trabeculae aligned at later stages when the increase in weight, and thus the loading, was slowed considerably compared with the early growth stage. Hence, the trabecular architecture was more efficient in later years. We conclude that density is adapted to external load from the early phase of growth, whereas the trabecular architecture is adapted later in the development.

The Effects of Trabecular-Bone Loading Variables on the Surface Signaling Potential for Bone Remodeling and Adaptation

“…5(A)]. The overshoot in VF that was observed in morphological studies of bone development in growing pigs 38 did not occur, however. From that stage on formation and resorption were balanced (remodeling).…”

“…4(B), relative to VS-gradient as the mechanical feedback variable. With 38 proceeding time the structure became coarser until finally homeostasis was reached, with less, but thicker, trabeculae, aligned with the external loads. Initially VF rose sharply in modeling and later stabilized to a final, mature value of 0.28 [ Fig.…”

Bone loss dynamics result in trabecular alignment in aging and ovariectomized rats

“…A similar process of ongoing trabecular adaptation after cessation of growth has been observed in pigs. 23 Traditionally, age-related bone loss in humans has been assumed to be due to secondary hyperparathyroidism and the related increase in bone remodeling, 5 although hyperparathyroidism might, at least partially, be induced by estrogen deficiency. 24 When female rats age, their estrous cycle becomes irregular and estrogen serum levels are lowered.…”

RANK/RANKL/OPG Expression in Rapid Maxillary Expansion

“…Mechanical stimulation, such as orthodontic/orthopedic treatment, may start and promote bone remodeling (1). Rapid maxillary expansion (RME) is usually used in the treatment of maxillary skeletal constriction.…”