Studies on Structural Changes in the Lumbar Annulus Fibrosus

Hirsch, Carl; Schajowicz, Fritz

doi:10.3109/17453675208989006

Cited by 264 publications

(86 citation statements)

References 27 publications

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“…During discography, it is not uncommon to reveal a centrally located radial tear that deviates circumferentially at its peripheral terminus [21,42,43]. Such tears have been reported as a common finding during the transverse sectioning of cadaveric lumbar discs [12,44]. Previous observations indicate that nuclear material may readily move circumferentially within the outer posterior annulus [17], which may possess weak interlamellar cohesion [18], and is prone to circumferential tearing [45].…”

Section: Discussionmentioning

confidence: 99%

“…Using finite element analysis, Schmidt et al [11] found that under this same loading combination, flexion plus left axial rotation, the fibres of the inner right posterolateral annulus experience the largest shear strain. It is possible that the combination of flexion and torsion may act to drive a herniation posterolaterally, contributing to the radial tears and herniations that occur in this region, as documented in cadaveric studies [12,13] and clinical practice [14][15][16].…”

Section: Introductionmentioning

confidence: 99%

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The influence of torsion on disc herniation when combined with flexion

2010

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The role of torsion in the mechanical derangement of intervertebral discs remains largely undefined. The current study sought to investigate if torsion, when applied in combination with flexion, affects the internal failure mechanics of the disc wall when exposed to high nuclear pressure. Thirty ovine lumbar motion segments were each positioned in 2°axial rotation plus 7°fl exion. Whilst maintained in this posture, the nucleus of each segment was gradually injected with a viscous radioopaque gel, via an injection screw placed longitudinally within the inferior vertebra, until failure occurred. Segments were then inspected using micro-CT and optical microscopy in tandem. Five motion segments failed to pressurize correctly. Of the remaining 25 successfully tested motion segments, 17 suffered vertebral endplate rupture and 8 suffered disc failure. Disc failure occurred in mature motion segments significantly more often than immature segments. The most common mode of disc failure was a central posterior radial tear involving a systematic annulus-endplate-annulus failure pattern. The endplate portion of these radial tears often propagated contralateral to the direction of applied axial rotation, and, at the lateral margin, only those fibres inclined in the direction of the applied torque were affected. Apart from the 2°of applied axial rotation, the methods employed in this study replicated those used in a previously published study. Consequently, the different outcome obtained in this study can be directly attributed to the applied axial rotation. These inter-study differences show that when combined with flexion, torsion markedly reduces the nuclear pressure required to form clinically relevant radial tears that involve cartilaginous endplate failure. Conversely, torsion appears to increase the disc wall's resistance to radial tears that do not involve cartilaginous endplate failure, effectively halving the disc wall's overall risk of rupture.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The influence of torsion on disc herniation when combined with flexion

2010

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“…Concentric and radial tears were found to be frequent in young discs as well as in specimens harvested from elderly donors. However, studies showed that the presence of radial tears increases with ageing [28,30]. Rim lesions and endplate separations had higher incidence in the 50-80 age group [69].…”

Section: Structural Changesmentioning

confidence: 98%

Ageing and degenerative changes of the intervertebral disc and their impact on spinal flexibility

et al. 2014

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Purpose Degeneration of the intervertebral disc is associated with various morphological changes of the disc itself and of the adjacent structures, such as reduction of the water content, collapse of the intervertebral space, disruption and tears, and osteophytes. These morphological changes of the disc are linked to alterations of the spine flexibility. This paper aims to review the literature about the ageing and degenerative changes of the intervertebral disc and their link with alterations in spinal biomechanics, with emphasis on flexibility. Methods Narrative literature review. Results Clinical instability of the motion segment, usually related to increased flexibility and hypothesized to be connected to early, mild disc degeneration and believed to be responsible for low back pain, was tested in numerous in vitro studies. Despite some disagreement in the findings, a trend toward spinal stiffening with the increasing degeneration was observed in most studies. Tests about tears and fissures showed inconsistent results, as well as for disc collapse and dehydration. Vertebral osteophytes were found to be effective in stabilizing the spine in bending motions. Conclusions The literature suggests that the degenerative changes of the intervertebral disc and surrounding structures lead to subtle alteration of the mechanical properties of the functional spinal unit. A trend toward spinal stiffening with the increasing degeneration has been observed in most studies.

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“…Previous authors have discussed the mucinous degeneration or annular disorganization occurring in the annulus before the appearance of concentric annular tears. 9,16 It is also possible that nonradial tears may weaken areas along the annulus, making it more prone to further injury and probable conversion to radial tears at a later date. More longitudinal studies will be needed to explore this further.…”

Section: Discussionmentioning

confidence: 99%