Structural alterations of the disc are accompanied by changes in disc tissue structure and composition during degeneration processes. Fissures and cracks appear in the disc some times extending from the outer annulus to the nucleus. Animal studies have shown that when a rim lesion was introduced in the annulus, progressive failure on the inner annulus was observed (1). From a macroscopic study on lumbar motion segments originating from regular autopsies it was shown (2) that nuclear clefts precede annular tears. Within the annular tears, rim lesions follow the radial and concentric tears. These age-related changes in disc tissue decrease the structural integrity of the disc contributing to the progression of degeneration. The effect of existing cracks and fissures in the lumbar discs on the biomechanics of the disc is an area where there is very little information currently in the literature.

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