-
Journal of Musculoskeletal & Neuronal... 2005The idea of bone quality is well-established in the literature and represents a real conundrum in the treatment of osteoporosis. On the one hand, there are measurements... (Review)
Review
The idea of bone quality is well-established in the literature and represents a real conundrum in the treatment of osteoporosis. On the one hand, there are measurements for patients that predict fracture risk for the population as a whole, but between individual patients, one will fracture but another will not, despite the fact that all of the technical measurements we use to predict fracture risk are the same. There are, of course, many aspects of bone mechanical properties that cannot yet be measured in patients. The session began with a discussion of what bone quality is, then the speakers presented work on novel aspects of bone properties that could help explain why fracture prediction in vivo is inexact.
Topics: Animals; Biomechanical Phenomena; Bone Matrix; Bone and Bones; Fractures, Bone; Humans; Osteoporosis
PubMed: 16340121
DOI: No ID Found -
The Angle Orthodontist Feb 2004By 1892, Julius Wolff and others realized that mechanical loads can affect bone architecture in living beings, but the mechanisms responsible for this effect were... (Review)
Review
By 1892, Julius Wolff and others realized that mechanical loads can affect bone architecture in living beings, but the mechanisms responsible for this effect were unknown, and it had no known clinical applications. In 2003 we know how this effect occurs and some of its applications. Our load-bearing bones (LBBs) include tibias, femurs, humeri, vertebrae, radii, mandibles, maxillae, wrists, hips, etc (so LBBs are not limited to weight-bearing ones). The strength of such bones and their trabeculae would represent their most important physiologic feature but in the special sense of relative to the size of the typical peak voluntary loads on them. The biologic "machinery" that determines whole-bone strength forms a tissue-level negative feedback system called the mechanostat. Two thresholds make a bone's strains determine its strength by switching on and off the biologic mechanisms that increase or decrease its strength. Equally, two thermostats can determine a room's temperature by switching on and off the room's heating and cooling systems. General features show that the largest voluntary loads on LBBs determine most of their strength after birth. These loads come from muscle forces so muscle strength strongly influences the strength of our LBBs. This process affects, in part, the healing of fractures, bone grafts, osteotomies, and arthrodeses; the bone's ability to endure load-bearing joint and dental endoprostheses; why healthy bones are stronger than the minimum needed to keep voluntary loads from breaking them suddenly or from fatigue; some general functions and disorders of bone modeling and basic multicellular unit-based bone remodeling; some limitations of in vitro data and of pharmaceutical actions; and the fact that many bone-active humoral and local agents have permissive roles in a bone's adaptations and healing, instead of forcing them to occur.
Topics: Biomechanical Phenomena; Bone Remodeling; Bone and Bones; Humans; Muscle, Skeletal; Weight-Bearing
PubMed: 15038485
DOI: 10.1043/0003-3219(2004)074<0003:AUOBPA>2.0.CO;2 -
International Journal of Oral Science Dec 2012Micromotion and fretting damages at the dental implant/bone interface are neglected for the limitation of check methods, but it is particularly important for the initial... (Review)
Review
Micromotion and fretting damages at the dental implant/bone interface are neglected for the limitation of check methods, but it is particularly important for the initial success of osseointegration and the life time of dental implant. This review article describes the scientific documentation of micromotion and fretting damages on the dental implant/bone interface. The fretting amplitude is less than 30 µm in vitro and the damage in the interface is acceptable. While in vivo, the micromotion's effect is the combination of damage in tissue level and the real biological reaction.
Topics: Biomechanical Phenomena; Bone and Bones; Dental Implants; Humans; Mechanical Phenomena; Movement; Osseointegration; Stress, Mechanical; Surface Properties
PubMed: 23258381
DOI: 10.1038/ijos.2012.68 -
Journal of Bone and Mineral Research :... Jun 2017Increases in fracture risk beyond what are expected from bone mineral density (BMD) are often attributed to poor "bone quality," such as impaired bone tissue strength....
Increases in fracture risk beyond what are expected from bone mineral density (BMD) are often attributed to poor "bone quality," such as impaired bone tissue strength. Recent studies, however, have highlighted the importance of tissue material properties other than strength, such as fracture toughness. Here we review the concepts behind failure properties other than strength and the physical mechanisms through which they cause mechanical failure: strength describes failure from a single overload; fracture toughness describes failure from a modest load combined with a preexisting flaw or damage; and fatigue strength describes failure from thousands to millions of cycles of small loads. In bone, these distinct failure mechanisms appear to be more common in some clinical fractures than others. For example, wrist fractures are usually the result of a single overload, the failure mechanism dominated by bone strength, whereas spinal fractures are rarely the result of a single overload, implicating multiple loading cycles and increased importance of fatigue strength. The combination of tissue material properties and failure mechanisms that lead to fracture represent distinct mechanistic pathways, analogous to molecular pathways used to describe cell signaling. Understanding these distinct mechanistic pathways is necessary because some characteristics of bone tissue can increase fracture risk by impairing fracture toughness or fatigue strength without impairing bone tissue strength. Additionally, mechanistic pathways to failure associated with fracture toughness and fatigue involve multiple loading events over time, raising the possibility that a developing fracture could be detected and interrupted before overt failure of a bone. Over the past two decades there have been substantial advancements in fracture prevention by understanding bone strength and fractures caused by a single load, but if we are to improve fracture risk prevention beyond what is possible now, we must consider material properties other than strength. © 2017 American Society for Bone and Mineral Research.
Topics: Biomechanical Phenomena; Bone and Bones; Fractures, Bone; Humans
PubMed: 28067411
DOI: 10.1002/jbmr.3078 -
Molecules and Cells Feb 2004Bone is a dynamic tissue that provides mechanical support, physical protection, and enables movement. Bone also serves as a storage site for minerals and is where blood... (Review)
Review
Bone is a dynamic tissue that provides mechanical support, physical protection, and enables movement. Bone also serves as a storage site for minerals and is where blood cells are produced. Bone homeostasis is regulated by the balance between bone formation and resorption, and involves the coordinated action of osteoblasts and osteoclasts. Osteoblasts are bone-forming cells that secrete organic matrix molecules, while osteoclasts are derived from hematopoietic precursors and resorb bone matrix. Although osteoblasts and osteoclasts are the major regulators of bone metabolism and are regulated by the local microenvironment, it has recently come to be appreciated that skeletal system homeostasis is greatly influenced by components of the immune system. For example, some pathological bone resorption observed under inflammatory conditions has been shown to be due, in part, to direct and indirect effects of activated T cells on osteoclasts. In this regard, we would like to review current progress and perspectives in "osteoimmunology", an interdisciplinary research principle governing the cross-talk between the bone and immune systems. Better understanding of how the osteoimmune system operates in normal and pathological situations is likely to lay the groundwork for future therapies for the variety of diseases that affect both bone and the immune system.
Topics: Allergy and Immunology; Animals; Bone and Bones; Humans; Immune System; Inflammation; Models, Biological; Signal Transduction
PubMed: 15055519
DOI: No ID Found -
Cells Sep 2020Bone infections, also known as infectious osteomyelitis, are accompanied by significant inflammation, osteolysis, and necrosis. Osteoclasts (OCs) are the bone-resorbing... (Review)
Review
Bone infections, also known as infectious osteomyelitis, are accompanied by significant inflammation, osteolysis, and necrosis. Osteoclasts (OCs) are the bone-resorbing cells that work in concert with osteoblasts and osteocytes to properly maintain skeletal health and are well known to respond to inflammation by increasing their resorptive activity. OCs have typically been viewed merely as effectors of pathologic bone resorption, but recent evidence suggests they may play an active role in the progression of infections through direct effects on pathogens and via the immune system. This review discusses the host- and pathogen-derived factors involved in the in generation of OCs during infection, the crosstalk between OCs and immune cells, and the role of OC lineage cells in the growth and survival of pathogens, and highlights unanswered questions in the field.
Topics: Animals; Bacteria; Bone Resorption; Bone and Bones; Cell Lineage; Humans; Immunomodulation; Osteoclasts
PubMed: 32987689
DOI: 10.3390/cells9102157 -
Genomics, Proteomics & Bioinformatics Mar 2008Weight-bearing bone is constantly adapting its structure and function to mechanical environments. Loading through routine exercises stimulates bone formation and... (Review)
Review
Weight-bearing bone is constantly adapting its structure and function to mechanical environments. Loading through routine exercises stimulates bone formation and prevents bone loss, but unloading through bed rest and cast immobilization as well as exposure to weightlessness during spaceflight reduces its mass and strength. In order to elucidate the mechanism underlying unloading-driven bone adaptation, ground-based in vitro and in vivo analyses have been conducted using rotating cell culturing and hindlimb suspension. Focusing on gene expression studies in osteoblasts and hindlimb suspension studies, this minireview introduces our recent understanding on bone homeostasis under weightlessness in space. Most of the existing data indicate that unloading has the opposite effects to loading through common signaling pathways. However, a question remains as to whether any pathway unique to unloading (and not to loading) may exist.
Topics: Adaptation, Physiological; Animals; Bone and Bones; Hindlimb Suspension; Humans; Osteoblasts; Weightlessness
PubMed: 18558381
DOI: 10.1016/S1672-0229(08)60016-9 -
Journal of Biomechanics 1987In 1961, Evans and King documented the mechanical properties of trabecular bone from multiple locations in the proximal human femur. Since this time, many investigators... (Review)
Review
In 1961, Evans and King documented the mechanical properties of trabecular bone from multiple locations in the proximal human femur. Since this time, many investigators have cataloged the distribution of trabecular bone material properties from multiple locations within the human skeleton to include femur, tibia, humerus, radius, vertebral bodies, and iliac crest. The results of these studies have revealed tremendous variations in material properties and anisotropy. These variations have been attributed to functional remodeling as dictated by Wolff's Law. Both linear and power functions have been found to explain the relationship between trabecular bone density and material properties. Recent studies have re-emphasized the need to accurately quantify trabecular bone architecture proposing several algorithms capable of determining the anisotropy, connectivity and morphology of the bone. These past studies, as well as continuing work, have significantly increased the accuracy of analytical and experimental models investigating bone, and bone/implant interfaces as well as enhanced our perspective towards understanding the factors which may influence bone formation or resorption.
Topics: Biomechanical Phenomena; Bone and Bones; Humans; Tensile Strength
PubMed: 3323197
DOI: 10.1016/0021-9290(87)90023-6 -
Bone Dec 2006Observations that dual-energy X-ray absorptiometry (DXA) measures of areal bone mineral density cannot completely explain fracture incidence after anti-resorptive... (Review)
Review
Observations that dual-energy X-ray absorptiometry (DXA) measures of areal bone mineral density cannot completely explain fracture incidence after anti-resorptive treatment have led to renewed interest in bone quality. Bone quality is a vague term but generally refers to the effects of skeletal factors that contribute to bone strength but are not accounted for by measures of bone mass. Because a clinical fracture is ultimately a mechanical event, it follows then that any clinically relevant modification of bone quality must change bone biomechanical performance relative to bone mass. In this perspective, we discuss a framework for assessing the clinically relevant effects of bone quality based on two general concepts: (1) the biomechanical effects of bone quality can be quantified from analysis of the relationship between bone mechanical performance and bone density; and (2) because of its hierarchical nature, biomechanical testing of bone at different physical scales (<1 mm, 1 mm, 1 cm, etc.) can be used to isolate the scale at which the most clinically relevant changes in bone quality occur. As an example, we review data regarding the relationship between the strength and density in excised specimens of trabecular bone and highlight the fact that it is not yet clear how this relationship changes during aging, osteoporosis development, and anti-resorptive treatment. Further study of new and existing data using this framework should provide insight into the role of bone quality in osteoporotic fracture risk.
Topics: Aging; Biomechanical Phenomena; Bone Density; Bone and Bones; Fractures, Bone; Humans
PubMed: 16876493
DOI: 10.1016/j.bone.2006.06.001 -
Journal of Bone and Mineral Research :... Oct 2017In postmenopausal osteoporosis, switching from teriparatide to denosumab results in continued bone mineral density (BMD) gains whereas switching from denosumab to...
In postmenopausal osteoporosis, switching from teriparatide to denosumab results in continued bone mineral density (BMD) gains whereas switching from denosumab to teriparatide results in BMD loss. To assess the effects of these transitions on bone microarchitecture and strength, we performed high-resolution peripheral QCT (HR-pQCT) at the distal tibia and radius in postmenopausal osteoporotic women who received 24 months of teriparatide 20 μg daily followed by 24 months of denosumab 60 mg every 6 months, 24 months of denosumab followed by 24 months of teriparatide, or 24 months of both medications followed by 24 months of denosumab. The 77 women who completed at least one post-switch visit are included in this analysis. Tibial cortical volumetric BMD (vBMD) increased between months 24 and 48 in the teriparatide-to-denosumab (net 48-month change -0.8% ± 2.4%) and combination-to-denosumab groups (net 48-month changes +2.4% ± 4.1%) but decreased in the denosumab-to-teriparatide group (net 48-month change -3.4% ± 3.2%, p < 0.001 for all between-group comparisons). Changes in total vBMD, cortical thickness, and estimated stiffness (by micro-finite element analysis [µFEA]) followed a similar pattern, as did changes at the radius. Conversely, tibial cortical porosity remained stable between months 24 and 48 in the teriparatide-to-denosumab and combination-to-denosumab groups (net 48-month changes +7.2% ± 14.8% and -3.4% ± 12.1%, respectively) but increased in the denosumab-to-teriparatide group (net 48-month change +16.2% ± 11.5%, p < 0.05 versus other groups). Trabecular vBMD changes did not differ among groups. Together, these findings demonstrate that in women treated with denosumab, switching to teriparatide is associated with a reduction in total and cortical vBMD, cortical thickness, and estimated strength, whereas switching to denosumab from teriparatide or combination therapy results in improvements in these parameters with the greatest improvements observed in women treated with combined therapy followed by denosumab. These findings strongly suggest that the use of teriparatide after denosumab should be avoided and that the use of combined teriparatide/denosumab followed by denosumab alone may be a useful treatment strategy in those with severe osteoporosis. © 2017 American Society for Bone and Mineral Research.
Topics: Aged; Biomechanical Phenomena; Bone Density; Bone and Bones; Cancellous Bone; Denosumab; Humans; Intention to Treat Analysis; Porosity; Radius; Teriparatide; Tibia; Tomography, X-Ray Computed
PubMed: 28608571
DOI: 10.1002/jbmr.3198