INTRODUCTION: Disc degeneration is related to progressive changes in tissue composition and morphology, such as water loss, height loss, endplate sclerosis, osteophytes. They are usually present in various combinations and may have different effects on the segment biomechanics. We investigated a wide range of clinical scenarios, in which the most common degenerative changes are present in various combinations using finite element models.
METHODS: A poroelastic FE model of the L4‐L5 human segment was employed and scaled to represent 10 spine segments from different individuals. We generated 30 models with six degenerative changes (condition of nucleus pulposus, annulus fibrosus and endplate cartilage; height loss; osteophytes; diffuse sclerosis), 10 for each degree of degeneration (mild, moderate, severe). A daily loading cycle including 8 hours of 200 N compression representing the night and 16 hours of 500 N modeling the day was considered. Two flexion‐extension cycles were also simulated, directly after the application of the 500 N load and before its removal.
RESULTS: A tendency to an increased stiffness with progressing overall degeneration was observed. Thus, instability for mild degeneration was not predicted. Nucleus degeneration reduced the daily disc height change; annulus degeneration had no influence. However, both parameters significantly correlated to a decrease in the flexion‐extension range of motion. Also osteophytes, sclerosis and height loss induced a reduction of daily disc height change and spine flexibility. Endplate sclerosis significantly limited the disc rehydration during the night.
DISCUSSION: These finding may help to get a better understanding of which parameter of disc degeneration we should look for with bio‐imaging methods. This may support the development of new tools to improve diagnostic value. Acknowledgments: This project is funded by the EU project GENODISC (HEALTH‐F2‐2008‐201626).