Biomechanics of the human intervertebral disc: a review of testing techniques and results
01 May 2017-Journal of The Mechanical Behavior of Biomedical Materials (Elsevier)-Vol. 69, pp 420-434
TL;DR: An overview of the studies conducted and their contribution to the current understanding of the biomechanics and function of the IVD is presented in a way that should prove useful to experimentalists and computational modellers.
Abstract: Many experimental testing techniques have been adopted in order to provide an understanding of the biomechanics of the human intervertebral disc (IVD). The aim of this review article is to amalgamate results from these studies to provide readers with an overview of the studies conducted and their contribution to our current understanding of the biomechanics and function of the IVD. The overview is presented in a way that should prove useful to experimentalists and computational modellers. Mechanical properties of whole IVDs can be assessed conveniently by testing ‘motion segments’ comprising two vertebrae and the intervening IVD and ligaments. Neural arches should be removed if load-sharing between them and the disc is of no interest, and specimens containing more than two vertebrae are required to study ‘adjacent level’ effects. Mechanisms of injury (including endplate fracture and disc herniation) have been studied by applying complex loading at physiologically-relevant loading rates, whereas mechanical evaluations of surgical prostheses require slower application of standardised loading protocols. Results can be strongly influenced by the testing environment, preconditioning, loading rate, specimen age and degeneration, and spinal level. Component tissues of the disc (anulus fibrosus, nucleus pulposus, and cartilage endplates) have been studied to determine their material properties, but only the anulus has been thoroughly evaluated. Animal discs can be used as a model of human discs where uniform non-degenerate specimens are required, although differences in scale, age, and anatomy can lead to problems in interpretation.
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TL;DR: Quantitative estimates improve the understanding of composition of human connective tissues, providing insights into their function in physiology and pathology.
Abstract: The function of connective tissues depends on the physical and biochemical properties of their extracellular matrix (ECM), which are in turn dictated by ECM protein composition. With the primary objective of obtaining quantitative estimates for absolute and relative amounts of ECM proteins, we performed a systematic review of papers reporting protein composition of human connective tissues. Articles were included in meta-analysis if they contained absolute or relative quantification of proteins found in the ECM of human bone, adipose tissue, tendon, ligament, cartilage and skeletal muscle. We generated absolute quantitative estimates for collagen in articular cartilage, intervertebral disk (IVD), skeletal muscle, tendon, and adipose tissue. In addition, sulfated glycosaminoglycans were quantified in articular cartilage, tendon and skeletal muscle; total proteoglycans in IVD and articular cartilage, fibronectin in tendon, ligament and articular cartilage, and elastin in tendon and IVD cartilage. We identified significant increases in collagen content in the annulus fibrosus of degenerating IVD and osteoarthritic articular cartilage, and in elastin content in degenerating disc. In contrast, collagen content was decreased in the scoliotic IVD. Finally, we built quantitative whole-tissue component breakdowns. Quantitative estimates improve our understanding of composition of human connective tissues, providing insights into their function in physiology and pathology.
126 citations
TL;DR: It is believed that the salutary effects of MSCs from different sources are not alike in terms of repairing or reformation of injured skeletal tissues, so differential identification of M SCs’ secretome enables us to make optimal choices in skeletal disorders considering various sources.
Abstract: Skeletal disorders are among the leading debilitating factors affecting millions of people worldwide. The use of stem cells for tissue repair has raised many promises in various medical fields, including skeletal disorders. Mesenchymal stem cells (MSCs) are multipotent stromal cells with mesodermal and neural crest origin. These cells are one of the most attractive candidates in regenerative medicine, and their use could be helpful in repairing and regeneration of skeletal disorders through several mechanisms including homing, angiogenesis, differentiation, and response to inflammatory condition. The most widely studied sources of MSCs are bone marrow (BM), adipose tissue, muscle, umbilical cord (UC), umbilical cord blood (UCB), placenta (PL), Wharton’s jelly (WJ), and amniotic fluid. These cells are capable of differentiating into osteoblasts, chondrocytes, adipocytes, and myocytes in vitro. MSCs obtained from various sources have diverse capabilities of secreting many different cytokines, growth factors, and chemokines. It is believed that the salutary effects of MSCs from different sources are not alike in terms of repairing or reformation of injured skeletal tissues. Accordingly, differential identification of MSCs’ secretome enables us to make optimal choices in skeletal disorders considering various sources. This review discusses and compares the therapeutic abilities of MSCs from different sources for bone and cartilage diseases.
101 citations
TL;DR: An overview on various current diagnostic and treatment options are provided and the interplay between each arms of these scientific and treatment advancements are discussed, hence providing an outlook of their potential future developments and collaborations in the management of intervertebral disc diseases.
Abstract: With an aging population, there is a proportional increase in the prevalence of intervertebral disc diseases. Intervertebral disc diseases are the leading cause of lower back pain and disability. With a high prevalence of asymptomatic intervertebral disc diseases, there is a need for accurate diagnosis, which is key to management. A thorough understanding of the pathophysiology and clinical manifestation aids in understanding the natural history of these conditions. Recent developments in radiological and biomarker investigations have potential to provide noninvasive alternatives to the gold standard, invasive discogram. There is a large volume of literature on the management of intervertebral disc diseases, which we categorized into five headings: (a) Relief of pain by conservative management, (b) restorative treatment by molecular therapy, (c) reconstructive treatment by percutaneous intervertebral disc techniques, (d) relieving compression and replacement surgery, and (e) rigid fusion surgery. This review article aims to provide an overview on various current diagnostic and treatment options and discuss the interplay between each arms of these scientific and treatment advancements, hence providing an outlook of their potential future developments and collaborations in the management of intervertebral disc diseases.
99 citations
21 Feb 2018
TL;DR: The significance of endplate cartilage and bone within a herniation was examined in 21 patients with and without SRS using H&E, Toluidine blue, Giemsa, and Masson-trichrome stains as mentioned in this paper.
Abstract: IntroductionHerniated disc tissue removed at surgery is mostly nucleus pulposus, with varying proportions of annulus fibrosus, cartilage endplate, and bone. Herniated nucleus swells and loses proteoglycans, and herniated annulus is invaded by blood vessels and inflammatory cells. However, little is known about the significance of endplate cartilage and bone within a herniation.MethodsHerniated tissue was removed surgically from 21 patients (10 with sciatica, 11 without). 5-μm sections were examined using H&E, Toluidine blue, Giemsa, and Masson-trichrome stains. Each tissue type in each specimen was scored for tears/fissures, neovascularisation, proteoglycan loss, cell clustering, and inflammatory cell invasion. Proportions of each tissue type were quantified using image analysis software.ResultsHerniations from patients with sciatica had greater nerve and blood vessel invasion (P<0.05), and a greater proportion contained cartilage endplate (7/10 vs 3/11, p<0.05). Cartilage fragments were generally small (...
54 citations
TL;DR: The current state of the art in the field of biomaterial‐based regeneration or repair for the nucleus pulposus, annulus fibrosus, and total disc transplantation in animals and humans is summarized, and essential suggestions for the development and clinical translation of biommaterials for disc regeneration are provided.
Abstract: A biomaterial-based strategy is employed to regenerate the degenerated intervertebral disc, which is considered a major generator of neck and back pain. Although encouraging enhancements in the anatomy and kinematics of the degenerative disc have been gained by biomaterials with various formulations in animals, the number of biomaterials tested in humans is rare. At present, most studies that involve the use of newly developed biomaterials focus on regeneration of the degenerative disc, but not pain relief. In this review, we summarise the current state of the art in the field of biomaterial-based regeneration or repair for the nucleus pulposus, annulus fibrosus, and total disc transplantation in animals and humans, and we then provide essential suggestions for the development and clinical translation of biomaterials for disc regeneration. It is important for researchers to consider the commonly neglected issues instead of concentrating solely on biomaterial development and fabrication.
54 citations
Cites background from "Biomechanics of the human intervert..."
...On the other hand, the biomaterials and their degradable products should not worsen the harsh microenvironment in the degenerated IVD, which is characterised by hypoxia, low nutrition, acidic pH, high mechanical loading, high osmolarity, and complicated proteases and cytokines network (Gilbert, Hodson, Baird, et al., 2016; Huang et al., 2013; Huang et al., 2014; Newell et al., 2017; Risbud & Shapiro, 2014; Schmidt, Reitmaier, Graichen, et al., 2016)....
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...3 MPa while weight carrying in a flexed position (Neidlinger‐Wilke, Galbusera, Pratsinis, et al., 2014; Newell et al., 2017)....
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References
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TL;DR: Disc degeneration can be graded reliably on routine T2-weighted magnetic resonance images using the grading system and algorithm presented in this investigation.
Abstract: Study design A reliability study was conducted Objectives To develop a classification system for lumbar disc degeneration based on routine magnetic resonance imaging, to investigate the applicability of a simple algorithm, and to assess the reliability of this classification system Summary of background data A standardized nomenclature in the assessment of disc abnormalities is a prerequisite for a comparison of data from different investigations The reliability of the assessment has a crucial influence on the validity of the data Grading systems of disc degeneration based on state of the art magnetic resonance imaging and corresponding reproducibility studies currently are sparse Methods A grading system for lumbar disc degeneration was developed on the basis of the literature An algorithm to assess the grading was developed and optimized by reviewing lumbar magnetic resonance examinations The reliability of the algorithm in depicting intervertebral disc alterations was tested on the magnetic resonance images of 300 lumbar intervertebral discs in 60 patients (33 men and 27 women) with a mean age of 40 years (range, 10-83 years) All scans were analyzed independently by three observers Intra- and interobserver reliabilities were assessed by calculating kappa statistics Results There were 14 Grade I, 82 Grade II, 72 Grade III, 68 Grade IV, and 64 Grade V discs The kappa coefficients for intra- and interobserver agreement were substantial to excellent: intraobserver (kappa range, 084-090) and interobserver (kappa range, 069-081) Complete agreement was obtained, on the average, in 838% of all the discs A difference of one grade occurred in 159% and a difference of two or more grades in 13% of all the cases Conclusion Disc degeneration can be graded reliably on routine T2-weighted magnetic resonance images using the grading system and algorithm presented in this investigation
3,048 citations
"Biomechanics of the human intervert..." refers background in this paper
...Published criteria allow IVD degeneration to be graded on the basis of MRI (Johannessen et al., 2006; Pfirrmann et al., 2001; Schneiderman et al., 1987), radiographic appearance (Gordon et al., 1991), or simply from visual appearance of IVDs sectioned in the sagittal or transverse plane (Galante, 1967; Thompson et al., 1990)....
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...Published criteria allow IVD degeneration to be graded on the basis of MRI (Johannessen et al., 2006; Pfirrmann et al., 2001; Schneiderman et al., 1987), radiographic appearance (Gordon et al....
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...Published criteria allow IVD degeneration to be graded on the basis of MRI (Johannessen et al., 2006; Pfirrmann et al., 2001; Schneiderman et al., 1987), radiographic appearance (Gordon et al., 1991), or simply from visual appearance of IVDs sectioned in the sagittal or transverse plane (Galante,…...
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TL;DR: To suggest how intervertebral disc degeneration might be distinguished from the physiologic processes of growth, aging, healing, and adaptive remodeling, and to simplify the issue of causality.
Abstract: and Introduction Abstract Study Design: Review and reinterpretation of existing literature. Objective: To suggest how intervertebral disc degeneration might be distinguished from the physiologic processes of growth, aging, healing, and adaptive remodeling. Summary of Background Data: The research literature concerning disc degeneration is particularly diverse, and there are no accepted definitions to guide biomedical research, or medicolegal practice. Definitions: The process of disc degeneration is an aberrant, cell-mediated response to progressive structural failure. A degenerate disc is one with structural failure combined with accelerated or advanced signs of aging. Early degenerative changes should refer to accelerated age-related changes in a structurally intact disc. Degenerative disc disease should be applied to a degenerate disc that is also painful. Justification: Structural defects such as endplate fracture, radial fissures, and herniation are easily detected, unambiguous markers of impaired disc function. They are not inevitable with age and are more closely related to pain than any other feature of aging discs. Structural failure is irreversible because adult discs have limited healing potential. It also progresses by physical and biologic mechanisms, and, therefore, is a suitable marker for a degenerative process. Biologic progression occurs because structural failure uncouples the local mechanical environment of disc cells from the overall loading of the disc, so that disc cell responses can be inappropriate or aberrant. Animal models confirm that cell-mediated changes always follow structural failure caused by trauma. This definition of disc degeneration simplifies the issue of causality: excessive mechanical loading disrupts a disc's structure and precipitates a cascade of cell-mediated responses, leading to further disruption. Underlying causes of disc degeneration include genetic inheritance, age, inadequate metabolite transport, and loading history, all of which can weaken discs to such an extent that structural failure occurs during the activities of daily living. The other closely related definitions help to distinguish between degenerate and injured discs, and between discs that are and are not painful.
1,463 citations
"Biomechanics of the human intervert..." refers background in this paper
...They allow the vertebral column to bend and twist (Bogduk, 2005; Humzah and Soames, 1988), and distribute compressive loading on the adjacent vertebral bodies (Adams and Roughley, 2006)....
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...…are important because human lumbar IVDs are often physically disrupted (Vernon-Roberts et al., 1997), which may give rise to degenerative changes (Adams and Dolan, 2012; Adams and Roughley, 2006; Ferguson and Steffen, 2003) and to chronic back pain (Cheung et al., 2009; de Schepper et al., 2010)....
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..., 1997), which may give rise to degenerative changes (Adams and Dolan, 2012; Adams and Roughley, 2006; Ferguson and Steffen, 2003) and to chronic back pain (Cheung et al....
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TL;DR: It is cautiously concluded that the intradiscal pressure during sitting may in fact be less than that in erect standing, that muscle activity increases pressure, that constantly changing position is important to promote flow of fluid to the disc, and that many of the physiotherapy methods studied are valid, but a number of them should be re-evaluated.
Abstract: Study design We conducted intradiscal pressure measurements with one volunteer performing various activities normally found in daily life, sports, and spinal therapy. Objectives The goal of this study was to measure intradiscal pressure to complement earlier data from Nachemson with dynamic and long-term measurements over a broad range of activities. Summary of background data Loading of the spine still is not well understood. The most important in vivo data are from pioneering intradiscal pressure measurements recorded by Nachemson during the 1960s. Since that time, there have been few data to corroborate or dispute those findings. Methods Under sterile surgical conditions, a pressure transducer with a diameter of 1.5 mm was implanted in the nucleus pulposus of a nondegenerated L4-L5 disc of a male volunteer 45-years-old and weighing 70 kg. Pressure was recorded with a telemetry system during a period of approximately 24 hours for various lying positions; sitting positions in a chair, in an armchair, and on a pezziball (ergonomic sitting ball); during sneezing, laughing, walking, jogging, stair climbing, load lifting during hydration over 7 hours of sleeping, and others. Results The following values and more were measured: lying prone, 0.1 MPa; lying laterally, 0.12 MPa; relaxed standing, 0.5 MPa; standing flexed forward, 1.1 MPa; sitting unsupported, 0.46 MPa; sitting with maximum flexion, 0.83 MPa; nonchalant sitting, 0.3 MPa; and lifting a 20-kg weight with round flexed back, 2.3 MPa; with flexed knees, 1.7 MPa; and close to the body, 1.1 MPa. During the night, pressure increased from 0.1 to 0.24 MPa. Conclusions Good correlation was found with Nachemson's data during many exercises, with the exception of the comparison of standing and sitting or of the various lying positions. Notwithstanding the limitations related to the single-subject design of this study, these differences may be explained by the different transducers used. It can be cautiously concluded that the intradiscal pressure during sitting may in fact be less than that in erect standing, that muscle activity increases pressure, that constantly changing position is important to promote flow of fluid (nutrition) to the disc, and that many of the physiotherapy methods studied are valid, but a number of them should be re-evaluated.
1,378 citations
"Biomechanics of the human intervert..." refers background in this paper
...In a healthy lumbar disc, in vivo pressures in the nucleus are between 460 and 1330 kPa in the seated position, 500 and 870 kPa in the standing position, and 91 and 539 kPa when lying either prone or supine (Nachemson and Morris, 1964, 1963; Sato et al., 1999; Wilke et al., 1999)....
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...The highest pressure in the nucleus (2300 kPa) was recorded in a standing subject who was flexing forwards holding a 20 kg mass (Wilke et al., 1999)....
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TL;DR: In this paper, the most important of these mechanisms appears to be decreasing nutrition of the central disc that allows accumulation of cell waste products and degraded matrix molecules, impairs cell nutrition, and causes a fall in pH levels that further compromises cell function and may cause cell death.
Abstract: Human intervertebral discs undergo age-related degenerative changes that contribute to some of the most common causes of impairment and disability for middle aged and older persons: spine stiffness, neck pain, and back pain. Potential causes of the age-related degeneration of intervertebral discs include declining nutrition, loss of viable cells, cell senescence, post-translational modification of matrix proteins, accumulation of degraded matrix molecules, and fatigue failure of the matrix. The most important of these mechanisms appears to be decreasing nutrition of the central disc that allows accumulation of cell waste products and degraded matrix molecules, impairs cell nutrition, and causes a fall in pH levels that further compromises cell function and may cause cell death. Although aging changes of the disc appear to be inevitable, identification of activities and agents that accelerate these changes may help decrease the rate and severity of disc degeneration; and recent work suggests that methods can be developed that will regenerate disc tissue.
1,162 citations