Low-back pain (LBP) is a common medical complaint and associated with high societal costs. Degeneration of the intervertebral disc (IVD) is assumed to be an important causal factor of LBP. IVDs are continuously mechanically loaded and both positive and negative effects have been attributed to different loading conditions.In order to study mechanical loading effects, degeneration-associated processes and/or potential regenerative therapies in IVDs, it is imperative to maintain the IVDs' structural integrity. While in vivo models provide comprehensive insight in IVD biology, an accompanying organ culture model can focus on a single factor, such as loading and may serve as a prescreening model to reduce life animal testing. In the current study we examined the feasibility of organ culture of caprine lumbar discs, with the hypothesis that a simulated-physiological load will optimally preserve IVD properties.Lumbar caprine IVDs (n = 175) were cultured in a bioreactor up to 21 days either without load, low dynamic load (LDL), or with simulated-physiological load (SPL). IVD stiffness was calculated from measurements of IVD loading and displacement. IVD nucleus, inner- and outer annulus were assessed for cell viability, cell density and gene expression. The extracellular matrix (ECM) was analyzed for water, glycosaminoglycan and total collagen content.IVD biomechanical properties did not change significantly with loading conditions. With SPL, cell viability, cell density and gene expression were preserved up to 21 days. Both unloaded and LDL resulted in decreased cell viability, cell density and significant changes in gene expression, yet no differences in ECM content were observed in any group.In conclusion, simulated-physiological loading preserved the native properties of caprine IVDs during a 21-day culture period. The characterization of caprine IVD response to culture in the LDCS under SPL conditions paves the way for controlled analysis of degeneration- and regeneration-associated processes in the future.

Mechanical overloading of the spine is associated with low back pain and intervertebral disc (IVD) degeneration. How excessive loading elicits degenerative changes in the IVD is poorly understood. Comprehensive knowledge of the interaction between mechanical loading, cell responses and changes in the extracellular matrix of the disc is needed in order to successfully intervene in this process. The purpose of the current study was to investigate whether dynamic and static overloading affect caprine lumbar discs differently and what mechanisms lead to mechanically induced IVD degeneration. Lumbar caprine IVDs (n = 175) were cultured 7, 14 and 21 days under simulated-physiological loading (control), high dynamic or high static loading. Axial deformation and stiffness were continuously measured. Cell viability, cell density, and gene expression were assessed in the nucleus, inner- and outer annulus. The extracellular matrix (ECM) was analyzed for water, glycosaminoglycan and collagen content. IVD height loss and changes in axial deformation were gradual with dynamic and acute with static overloading. Dynamic overloading caused cell death in all IVD regions, whereas static overloading mostly affected the outer annulus. IVDs expression of catabolic and inflammation-related genes was up-regulated directly, whereas loss of water and glycosaminoglycan were significant only after 21 days. Static and dynamic overloading both induced pathological changes to caprine lumbar IVDs within 21 days. The mechanism by which they inflict biomechanical, cellular, and extracellular changes to the nucleus and annulus differed. The described cascades provide leads for the development of new pharmacological and rehabilitative therapies to halt the progression of DDD.

Dorsal laminectomy and partial discectomy does not lead to significant spinal instability. Pedicle screw-rod fixation of L7 and S1 may be used to stabilize an unstable L7-S1 junction in dogs with degenerative lumbosacral stenosis.

No abstract

These data show that, in humans and in quadrupeds, the thoracic spine is less rotationally stable under dorsal shear loads than under ventral shear loads.

Background and purpose Bones used in mechanical studies are frequently harvested from human cadavers that have been embalmed in a buffered formaldehyde solution. It has been reported that formaldehyde fixation or freezing hardly affects the mechanical properties of bone after a storage period of several weeks. However, human cadaver bones are usually stored for longer periods of time before use. We therefore investigated the effects of long-term embalming or freezing on the mechanical properties of cortical bone.Methods After 5 different storage periods (ranging from 0 to 12 months), goat femora and humeri were used to evaluate the effect of embalming and freezing on torsion, and on bending stiffness and strength. The effect on hardness and bone mineral density (BMD) was also evaluated.Results Even after 1 year, no statistically significant differences could be found in stiffness, strength, and energy absorption when we compared embalmed or frozen bones to a fresh reference group. In addition, although we found no significant change in BMD, there appears to be a tendency to increasing hardness.Interpretation We found that there was no effect on the mechanical properties of bone after storage periods of 1 year. We conclude that embalmed or frozen bones can safely be used for mechanical testing, at least for storage periods of up to one year.

Intradiscal pressure is influenced by recent loading due to fluid flow. The correlations found in this study suggest that intradiscal pressure is important for disc height and axial compliance. These findings are relevant for mechanobiology studies, nucleus replacements, finite element models, and ex vivo organ culture systems.

No abstract