Abstract
Disc degeneration in the human spine is characterised by progressive fraying and dehydration of the nucleus pulposus associated with formation of clefts within the annulus fibrosus.
These have been classified on the basis of autopsy studies into radiating, circumferential and peripheral tears (rim lesions).
Outer tears allow neovascularisation of the outer third of the annulus fibrosus and ingrowth of nerve fibres.
Correlation with discographic findings had suggested the relevance of peripheral defects in the pathogenesis of discogenic pain.
Outer annular tears are likely to be linked to tensile strain onto the collagen fibres and, therefore, may have a mechanical aetiology.
In the animal model, peripheral tears of the outer annulus were proven to induce degenerative changes within the inner annulus and the nucleus pulposus.
The increased understanding of the role of discrete peripheral defects of the annulus in discogenic pain may support the potential therapeutic effects of thermal treatment using radiofrequency waves and specially designed probes.
At present, however, no in vivo studies have been able to demonstrate healing of outer annulus defects and reversibility of mechanical lesions to the intervertebral discs by thermal therapy.
While it is highly likely that discrete defects of the outer annulus may be responsible for acute episodes of self-limiting low back pain, it is unclear if annular pathology may be as relevant for chronic disabling back pain.
Recent studies using discography and other semi-invasive techniques have suggested that the main discriminating factors between benign, self limiting and chronic disabling back pain may not be anatomical but psycho-social.
The challenge remains, in the 21st Century as in the past, to devise appropriate strategies that may lessen the socio-economic burden of back pain.
Surgery, however, is highly unlikely to play a significant role in the future.
The abstracts were prepared by Professor Jegan Krishnan. Correspondence should be addressed to him at the Flinders Medical Centre, Bedford Park 5047, Australia.
