Vital biomechanics: Proposed general concepts for skeletal adaptations to mechanical usage

Hm, Frost

doi:10.1007/bf02556327

Cited by 326 publications

(207 citation statements)

References 35 publications

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“…The geometric deformation of bone in response to applied stress is called strain [66], defined quantitatively as the change in length as a percentage of the unloaded length. Strains due to normal activity generally range from 200 to 2,500 μstrain [96] and the ultimate strength (fracture threshold) of healthy, young lamellar bone is approximately 25,000 μstrain (equal to 2.5% change in length) [93], leaving a sizable safety margin for volitional activities. Strains of about 1,500 to 2,500 μstrain trigger the mobilization of osteoclast and osteoblast drifts at bone surfaces (a process called modeling [90]), leading to enhancements in cortical thickness [78,[97][98][99][100] and (to a lesser degree) trabecular BMD [78,97,99].…”

Section: Bone Response To Trainingmentioning

confidence: 99%

Muscle and bone plasticity after spinal cord injury: Review of adaptations to disuse and to electrical muscle stimulation

Dudley-Javoroski

Shields

2008

JRRD

161

141

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Abstract-The paralyzed musculoskeletal system retains a remarkable degree of plasticity after spinal cord injury (SCI). In response to reduced activity, muscle atrophies and shifts toward a fast-fatigable phenotype arising from numerous changes in histochemistry and metabolic enzymes. The loss of routine gravitational and muscular loads removes a critical stimulus for maintenance of bone mineral density (BMD), precipitating neurogenic osteoporosis in paralyzed limbs. The primary adaptations of bone to reduced use are demineralization of epiphyses and thinning of the diaphyseal cortical wall. Electrical stimulation of paralyzed muscle markedly reduces deleterious post-SCI adaptations. Recent studies demonstrate that physiological levels of electrically induced muscular loading hold promise for preventing post-SCI BMD decline. Rehabilitation specialists will be challenged to develop strategies to prevent or reverse musculoskeletal deterioration in anticipation of a future cure for SCI. Quantifying the precise dose of stress needed to efficiently induce a therapeutic effect on bone will be paramount to the advancement of rehabilitation strategies.

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Section: Bone Response To Trainingmentioning

confidence: 99%

Muscle and bone plasticity after spinal cord injury: Review of adaptations to disuse and to electrical muscle stimulation

Dudley-Javoroski

Shields

2008

JRRD

161

141

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“…The trabeculae in this matrix constitute the actual loadcarrying construction. The material properties of the trabeculae, in combination with their architecture, determine the strength and stiffness of trabecular bone Under loading, these properties determine the strains at microstructural levels that are believed to regulate the biological adaptive processes in trabecular bone (Frost, 1987;Martin and Burr, 1989). In spite of their importance, little is known about the microstructural properties and loading of the individual trabeculae.…”

Section: Introductionmentioning

confidence: 99%

A new method to determine trabecular bone elastic properties and loading using micromechanical finite-element models

Rietbergen¹

1995

Journal of Biomechanics

186

249

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Abstract--The apparent mechanical behavior of trabecular bone depends on properties at the tissue or trabecular level. Many investigators have attempted to determine trabecular tissue properties and loading. However, accuracy and applicability of all methods reported are limited. The small size of the trabeculae and a possible size effect are complicating factors when using traditional testing methods on single trabeculae. Other methods reported, using models that describe the trabecular structure, are of limited value because they consider bone as a repetitive structure in order to describe a reasonably large region of bone.The present study introduces a new finite-element method strategy that enables analysis of reasonably large regions of trabecular bone in full detail. The method uses three-dimensional serial reconstruction techniques to construct a large-scale FE model, by directly converting voxels to elements. A 5 mm cube of trabecular bone was modeled in this way, resulting in a FE model that consists of 296,679 elements. Special strategies were developed to solve the set of equations that results from the FE approach.Using this model in combination with experimental apparent data taken from the literature, the upper and lower boundaries for the tissue modulus were calculated to be 10.1 and 2.23 GPa, respectively. From the local stress and strain distributions it was concluded that the deformation mode of the trabeculae in the present cube was predominantly in bending. It was concluded that the method developed offers new perspectives for the study of trabecular bone.

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“…Bone homeostasis is particularly sensitive to both gravitational and mechanical stimuli, which play a very important role in determining bone structure and influencing related metabolic and catabolic processes [Frost, 1988]. Bone turnover depends on the balance of bone formation by osteoblasts and bone resorption by osteoclasts.…”

mentioning

confidence: 99%

Modeled gravitational unloading triggers differentiation and apoptosis in preosteoclastic cells

et al. 2006

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Gravity acts permanently on organisms as either static or dynamic stimulation. Understanding the influence of gravitational and mechanical stimuli on biological systems is an intriguing scientific problem. More than two decades of life science studies in low g, either real or modeled by clinostats, as well as experimentation with devices simulating different types of controlled mechanical stimuli, have shown that important biological functions are altered at the single cell level. Here, we show that the human leukemic line FLG 29.1, characterized as an osteoclastic precursor model, is directly sensitive to gravitational unloading, modeled by a random positioning machine (RPM). The phenotypic expression of cytoskeletal proteins, osteoclastic markers, and factors regulating apoptosis was investigated using histochemical and immunohistochemical methods, while the expression of the corresponding genes was analyzed using RT-PCR. A quantitative bone resorption assay was performed. Autofluorescence spectroscopy and imaging were applied to gain information on cell metabolism. The results show that modeled hypogravity may trigger both differentiation and apoptosis in FLG 29.1 cells. Indeed, when comparing RPM versus 1 Â g cultures, in the former we found cytoskeletal alterations and a marked increase in apoptosis, but the surviving cells showed an osteoclastic-like morphology, overexpression of osteoclastic markers and the ability to resorb bone. In particular, the overexpression of both RANK and its ligand RANKL, maintained even after return to 1 Â g conditions, is consistent with the firing of a differentiation process via a paracrine/autocrine mechanism. J. Cell. Biochem. 98: 65-80, 2006. ß 2005 Wiley-Liss, Inc.Key words: weightlessness; preosteoclastic differentiation; apoptosis; bone resorption; osteoporosis; gene expressionThe importance of gravity in modulating some biological processes, such as plant gravitropism and the adaptation of the vertebrate skeleton in relation to its load-bearing function, has long been known. Nevertheless, the role of gravity and other mechanical factors in biological processes is far from clear. A weightless environment is a powerful tool for understanding this role and for studying the related cellular and molecular mechanisms. Several investigations conducted in space laboratories and with instruments averaging the gravity vector, and thus simulating conditions of reduced gravity, have shown that isolated cells may change their behavior under altered gravitational conditions. Loss of cell activation [Cogoli et al., 1984], perturbation of signal transduction [Schmitt et al., 1996;Hashemi et al., 1999] and modification of genetic expression [Walther et al., 1998;Hammond et al., 1999] have been described. This suggests that some of the mechanisms at the roots of the systemic effects observed in weightlessness, such as depression of the immune system [Gmü nder and Cogoli, 1996]

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Vital biomechanics: Proposed general concepts for skeletal adaptations to mechanical usage

Cited by 326 publications

References 35 publications

Muscle and bone plasticity after spinal cord injury: Review of adaptations to disuse and to electrical muscle stimulation

Muscle and bone plasticity after spinal cord injury: Review of adaptations to disuse and to electrical muscle stimulation

A new method to determine trabecular bone elastic properties and loading using micromechanical finite-element models

Modeled gravitational unloading triggers differentiation and apoptosis in preosteoclastic cells

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