Effects of Axial Torsion on Disc Height Distribution: An In Vivo Study

Abstract

Objectives Axial rotation of the torso is commonly used during manipulation treatment of low back pain. Little is known about the effect of these positons on disc morphology. Rotation is a three-dimensional event that is inadequately represented with planar images in the clinic. True quantification of the intervertebral gap can be achieved with a disc height distribution. The objective of this study was to analyze disc height distribution patterns during torsion relevant to manipulation in vivo. Methods Eighty-one volunteers were CT-scanned both in supine and in right 50° rotation positions. Virtual models of each intervertebral gap representing the disc were created with the inferior endplate of each ‘disc’ set as the reference surface and separated into five anatomical zones: four peripheral and one central, corresponding to the footprint of the annulus fibrosus and nucleus pulposus, respectively. Whole-disc and individual anatomical zone disc height distributions were calculated in both positions, and were compared against each other with ANOVA, with significance set at p < 0.05. Results Mean neutral disc height was 7.32 (1.59) mm. With 50° rotation, a small but significant increase to 7.44 (1.52) mm (p < 0.0002) was observed. The right side showed larger separation in most levels, except at L5/S1. The posterior and right zones increased in height upon axial rotation of the spine (p < 0.0001), while the left, anterior and central decreased. Conclusions This study quantified important tensile/compressive changes disc height during torsion. The implications of these mutually opposing changes on spinal manipulation are still unknown.

A Dynamic Radiographic Imaging Study of Lumbar Intervertebral Disc Morphometry and Deformation In Vivo

“…1a). This pattern appears consistent with disc height patterns measured in the supine and axially twisted positions 38 and may be attributed to the increased inferior endplate concavity of lower lumbar vertebrae observed in previous lumbar morphometry studies 39,40 .…”

ISSLS PRIZE IN BASIC SCIENCE 2018: Growth differentiation factor-6 attenuated pro-inflammatory molecular changes in the rabbit anular-puncture model and degenerated disc-induced pain generation in the rat xenograft radiculopathy model

“…Reference source not found. a) and averaged to determine disc height distribution (DHD) using a custom-written Microsoft Visual C++ software [24]. Within each spine segment, the normalized DHD was calculated by dividing the average DHD of punctured discs (L2/3 and L4/5) by the DHD of the non-punctured control disc (L3/4).…”

Spine biomechanical testing methodologies: The controversy of consensus vs scientific evidence

“…Clinical based imaging, such as magnetic resonance (MR) imaging, computed tomography (CT), or X‐ray, are commonly used to assess disc health and can be used to measure disc anatomy. Imaging of specimens after harvest but before testing accounts for the release of residual stresses from spinal ligaments and muscles, which may cause in vitro disc height measurements to be greater than in vivo measurements 30,98‐103 . Johnstone et al showed that fluid content of the inner annulus increases after autopsy compared to discs with the same degenerative grade during surgery, resulting in more uniform intradiscal pressure throughout the disc 104 …”

“…Imaging of specimens after harvest but before testing accounts for the release of residual stresses from spinal ligaments and muscles, which may cause in vitro disc height measurements to be greater than in vivo measurements. 30,[98][99][100][101][102][103] Johnstone et al showed that fluid content of the inner annulus increases after autopsy compared to discs with the same degenerative grade during surgery, resulting in more uniform intradiscal pressure throughout the disc. 104 Each imaging modality provides different assessments that may be important for defining mechanical testing parameters or interpreting results.…”