The Influence of Concordant Complex Posture and Loading Rate on Motion Segment Failure: A Mechanical and Microstructural Investigation.

Study Design: Microstructural investigation of compression-induced herniation of a lumbar disc held in a concordant complex posture.

Objective: To explore the significance of loading rate in a highly asymmetric concordant posture, comparing the mechanisms of failure to an earlier study using a nonconcordant complex posture.

Summary Of Background Data: A recent study with a nonconcordant complex posture (turning in the opposite direction to that which the load is applied) demonstrated the vulnerability of the disc to loading that is borne by one set of oblique-counter oblique fiber sets in the alternating lamellae of the annulus, and aggravated by an elevated loading rate.

A more realistic disc herniation model incorporating compression, flexion and facet-constrained shear: a mechanical and microstructural analysis. Part II: high rate or 'surprise' loading.

Purpose: Part I of this study explored mechanisms of disc failure in a complex posture incorporating physiological amounts of flexion and shear at a loading rate considerably lower than likely to occur in a typical in vivo manual handling situation. Given the strain-rate-dependent mechanical properties of the heavily hydrated disc, loading rate will likely influence the mechanisms of disc failure. Part II investigates the mechanisms of failure in healthy discs subjected to surprise-rate compression while held in the same complex posture.

A more realistic disc herniation model incorporating compression, flexion and facet-constrained shear: a mechanical and microstructural analysis. Part I: Low rate loading.

Purpose: To date, the mechanisms of disc failure have been explored at a microstructural level in relatively simple postures. However, in vivo the disc is known to be subjected to complex loading in compression, bending and shear, and the influence of these factors on the mechanisms of disc failure is yet to be described at a microstructural level. The purpose of this study was to provide a microstructural analysis of the mechanisms of failure in healthy discs subjected to compression while held in a complex posture incorporating physiological amounts of flexion and facet-constrained shear.

A Microstructural Investigation of Disc Disruption Induced by Low Frequency Cyclic Loading.

Study Design: Microstructural investigation of low frequency cyclic loading and flexing of the lumbar disc.

Objective: To explore micro-level structural damage in motion segments subjected to low frequency repetitive loading and flexing at sub-acute loads.

Summary Of Background Data: Cumulative exposure to mechanical load has been implicated in low back pain and injury.

ISSLS Prize Winner: Vibration Really Does Disrupt the Disc: A Microanatomical Investigation.

Study Design: Microstructural investigation of vibration-induced disruption of the flexed lumbar disc.

Objective: The aim of the study was to explore micro-level structural damage in motion segments subjected to vibration at subcritical peak loads.

Summary Of Background Data: Epidemiological evidence suggests that cumulative whole body vibration may damage the disc and thus play an important role in low back pain.

ISSLS Prize Winner: A Detailed Examination of the Elastic Network Leads to a New Understanding of Annulus Fibrosus Organization.

Study Design: Investigation of the elastic network in disc annulus and its function.

Objective: To investigate the involvement of the elastic network in the structural interconnectivity of the annulus and to examine its possible mechanical role.

Summary Of Background Data: The lamellae of the disc are now known to consist of bundles of collagen fibers organized into compartments.

A detailed microscopic examination of alterations in normal anular structure induced by mechanical destabilization in an ovine model of disc degeneration.

Study Design: Microstructural investigation of anular structure.

Objective: To reveal the effect of mechanical destabilization on the anular architecture both locally and distantly.

Summary Of Background Data: Several longitudinal ovine-induced disc degeneration studies have documented degenerative changes in disc components using histologic, biomechanical, and biochemical approaches; however, changes in intervertebral disc (IVD) microstructure have largely remained neglected.

How age influences unravelling morphology of annular lamellae - a study of interfibre cohesivity in the lumbar disc.

Although age- and degeneration-related changes in the morphology and biochemistry of the annulus fibrosus have been extensively reported, studies of tensile strength changes show only a weak correlation with maturity. Given that the disc is a tissue system in which significant levels of deformation occur with normal physiological loading, there may be structure-related properties that provide a better indicator of the influence of ageing on its function. This study is a morphological investigation of lamellar interfibre cohesivity with respect to maturity.

A microstructural investigation of intervertebral disc lamellar connectivity: detailed analysis of the translamellar bridges.

Little is known about the complex forces acting on the deformable multi-layered annulus at a microstructural level as the spine is compressed, flexed and twisted. The recently described translamellar bridging network radially linking many lamellae at discrete locations around the disc wall could be expected to play a significant biomechanical role. In this study, segments of annular wall that were sectioned at a range of angles (oblique, in-plane, sagittal and transverse) were examined using differential interference contrast microscopy to fully elucidate the fibrous detail of the translamellar bridging structures.

ISSLS prize winner: microstructure and mechanical disruption of the lumbar disc annulus: part I: a microscopic investigation of the translamellar bridging network.

Study Design: Microstructural investigation of interlamellar connectivity.

Objective: To reveal the macro and micro structure of the translamellar bridging network in the lumbar annulus.

Summary Of Background Data: Contrary to the view that there is minimal interconnection between lamellar sheets, experimental data reveal a significant contribution to the material behavior of the annulus from interactions between fiber populations of alternating lamellae.