Artikel
Different patterns of lumbar intervertebral disc degeneration: a biomechanical evaluation
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Veröffentlicht: | 21. Oktober 2010 |
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Gliederung
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Objective: Degeneration of the intervertebral disc is related to progressive changes in the disc tissue structure and properties. These changes may be present separately or, more frequently, in various combinations. The different degenerative changes may have opposite effects on the spine biomechanics. Therefore, therapeutic options which allow for good clinical results in some patients may be inadequate for the treatment of other patients. This work is aimed to the investigation of the mechanical relevance of the most common degenerative changes of the intervertebral disc, when they are present in various combinations.
Methods: A poroelastic nonlinear FE model of the L4–L5 human spine segment was employed and randomly scaled to represent 10 spine segments from different individuals. Six different degenerative characteristics (condition of nucleus pulposus, annulus fibrosus and endplate cartilage; height loss; osteophyte formation; diffuse sclerosis) were modeled in 30 randomly generated models, 10 for each overall degree of degeneration (mild, moderate, severe). For each model, a daily loading cycle including 8 hours of rest, 16 hours in the standing position and 2 flexion-extension motion cycles was simulated.
Results and conlcusions: A tendency to an increase of stiffness with progressing overall degeneration was observed. Nucleus degeneration reduced the daily height change of the disc; annulus degeneration had no influence on this result. However, both parameters were significantly correlated to a decrease in the flexion-extension range of motion. Also osteophytosis, diffuse sclerosis and disc height loss induced a reduction of daily axial displacement and spine flexibility. Endplate sclerosis significantly limited the disc rehydration during the rest period. The present investigation of the biomechanical effect of different combinations of degenerative changes may help to better understand disc degeneration from a biomechanical point of view. These results may help in the choice of the appropriate treatment for degenerative disc disease on a patient-specific basis, both with conservative or surgical approaches.
Acknowledgements: This project is funded by the EU project GENODISC (HEALTH-F2-2008-201626).