Internal Displacement Distribution from In Vitro Loading of Human Thoracic and Lumbar Spinal Motion Segments: Experimental Results and Theoretical Predictions

Direct measurement of intervertebral disc maximum shear strain in six degrees of freedom: Motions that place disc tissue at risk of injury

“…The use of beads to measure tissue deformation has been previously employed in 2-D radiography studies of internal disc motion (Krag et al, 1987, Seroussi et al, 1989. These methodologies assume that the metallic markers track tissue strain.…”

“…Disc tissue internal deformation and strain have been estimated from displacements of markers in the mid-sagittal plane (Krag et al, 1987;Seroussi et al, 1989), and in the mid-transverse plane (Tsantrizos et al, 2005) during compression and bending loading. These studies were limited to 2-dimensions and while they provided useful insights into the internal behavior of the disc in compression and bending motions, axial rotation (Shirazi-Adl, 1989;Steffen et al, 1998) and shear loading (Marras et al, 2001;Mcgill et al, 2000;Norman et al, 1998) have been linked to increased back injury rates and these motions warrant investigation.…”

Dynamic stabilization devices in the treatment of low back pain

“…[21] Disc degeneration alters the isotropic nature of the disc. [28] In vivo stress profilometry studies also confirm that load distribution across the endplate becomes uneven after disc degeneration, with areas of high spot loading, particularly associated with certain positions ( Figure 2C). Such irregular load distribution was found to be a strong predictor of pain reproduction by provocative discography [27] .…”

The myth of lumbar instability: the importance of abnormal loading as a cause of low back pain

“…Another important consequence of the uniformity of distribution of load transmission across the surface of the disc is that it transmits load to the annulus, producing a tension in the annulus, and converting it into a loadbearing structure. It is established that disc degeneration alters the isotropic nature of the disc [19,27] and, as a consequence, load transmission over the endplate becomes irregular, leading to high spot-loading, particularly associated with certain positions. It will be appreciated that the degree of disc degeneration itself will not affect to the loading pattern, as the anatomy of the degenerate disc is so varied.…”