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Bone Adaptation (bone + adaptation)
Selected AbstractsBone adaptation to load: microdamage as a stimulus for bone remodellingJOURNAL OF ANATOMY, Issue 6 2002T. C. Lee Abstract Mechanical loading in the proximal radius was increased by ulnar osteotomy (Group O), altered by Steinmann pinning (Group P) or unaltered in sham operated controls (Group C) in skeletally mature female sheep, aged 2,4 years. A series of intravenous fluorochromes were given to label bone formation and fuchsin-stained microdamage assessed at intervals of up to 24 weeks. Microcracks were present in all groups and were found in the original cortex near the periosteal surface. No microcracks were found in the new, fibrolamellar bone laid down at periosteal or endosteal surfaces. Mean microcrack length (49 µm, SD 10 µm) did not differ between groups or over time. Microcrack numerical and surface densities and resorption cavity density peaked in all groups at 6 weeks, consistent with a regional acceleratory phenomenon (RAP), but the peaks were significantly greater in Group O. The density of refilling or secondary osteons peaked at 10 weeks and the mean time required for the formation of an osteon was 7.51 ± 0.59 weeks. Fatigue-induced microdamage is normally present in bone and is increased due to repetitive loading of the mechanically overloaded radius. The location and timing of microcracks, resorption cavities and secondary osteons are consistent with the activation-resorption-formation remodelling cycle and suggest that microdamage is a stimulus for bone remodelling. [source] Mechanical properties of femoral cortical bone following cemented hip replacementJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 11 2007G.X. Ni Abstract Femoral bone remodeling following total hip replacement is a big concern and has never been examined mechanically. In this study, six goats underwent unilateral cemented hip hemiarthroplasty with polymethyl methacrylate (PMMA) bone cement. Nine months later animals were sacrificed, and the femoral cortical bone slices at different levels were analysed using microhardness testing and microcomputed tomography (micro-CT) scanning. Implanted femurs were compared to contralateral nonimplanted femurs. Extensive bone remodeling was demonstrated at both the proximal and middle levels, but not at the distal level. Compared with the nonimplanted side, significant decreases were found in the implanted femur in cortical bone area, bone mineral density, and cortical bone hardness at the proximal level, as well as in bone mineral density and bone hardness at the middle level. However, no significant difference was observed in either variable for the distal level. In addition, similar proximal-to-distal gradient changes were revealed both in cortical bone microhardness and bone mineral density. From the mechanical point of view, the results of the present study suggested that stress shielding is an important mechanical factor associated with bone adaptation following total hip replacement. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:1408,1414, 2007 [source] Masticatory loading and bone adaptation in the supraorbital torus of developing macaquesAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2009K. Kupczik Abstract Research on the evolution and adaptive significance of primate craniofacial morphologies has focused on adult, fully developed individuals. Here, we investigate the possible relationship between the local stress environment arising from masticatory loadings and the emergence of the supraorbital torus in the developing face of the crab-eating macaque Macaca fascicularis. By using finite element analysis (FEA), we are able to evaluate the hypothesis that strain energy density (SED) magnitudes are high in subadult individuals with resulting bone growth in the supraorbital torus. We developed three micro-CT-based FEA models of M. fascicularis skulls ranging in dental age from deciduous to permanent dentitions and validated them against published experimental data. Applied masticatory muscle forces were estimated from physiological cross-sectional areas of macaque cadaveric specimens. The models were sequentially constrained at each working side tooth to simulate the variation of the bite point applied during masticatory function. Custom FEA software was used to solve the voxel-based models and SED and principal strains were computed. A physiological superposition SED map throughout the face was created by allocating to each element the maximum SED value from each of the load cases. SED values were found to be low in the supraorbital torus region throughout ontogeny, while they were consistently high in the zygomatic arch and infraorbital region. Thus, if the supraorbital torus arises to resist masticatory loads, it is either already adapted in each of our subadult models so that we do not observe high SED or a lower site-specific bone deposition threshold must apply. Am J Phys Anthropol, 2009. © 2008 Wiley-Liss, Inc. [source] The effects of total hip arthroplasty on the structural and biomechanical properties of adult boneAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2009Joshua J. Peck Abstract The responsiveness of bone to mechanical stimuli changes throughout life, with adaptive potential generally declining after skeletal maturity is reached. This has led some to question the importance of bone functional adaptation in the determination of the structural and material properties of the adult skeleton. A better understanding of age-specific differences in bone response to mechanical loads is essential to interpretations of long bone adaptation. The purpose of this study is to examine how the altered mechanical loading environment and cortical bone loss associated with total hip arthroplasty affects the structural and biomechanical properties of adult bone at the mid-shaft femur. Femoral cross sections from seven individuals who had undergone unilateral total hip arthroplasty were analyzed, with intact, contralateral femora serving as an approximate internal control. A comparative sample of individuals without hip prostheses was also included in the analysis. Results showed a decrease in cortical area in femora with prostheses, primarily through bone loss at the endosteal envelope; however, an increase in total cross-sectional area and maintenance of the parameters of bone strength, Ix, Iy, and J, were observed. No detectable differences were found between femora of individuals without prostheses. We interpret these findings as an adaptive response to increased strains caused by loading a bone previously diminished in mass due to insertion of femoral prosthesis. These results suggest that bone accrued through periosteal apposition may serve as an important means by which adult bone can functional adapt to changes in mechanical loading despite limitations associated with senescence. Am J Phys Anthropol 2009. © 2008 Wiley-Liss, Inc. [source] | ||||||||||