Vertebral Endplate Defect as Initiating Factor in Intervertebral Disc Degeneration Strong Association Between Endplate Defect and Disc Degeneration in the General Population

Study Design. Cross-sectional study of spine magnetic resonance in a population, predominantly female, sample. Objective. To determine the relationship between vertebral endplate defect and intervertebral disc degeneration (DD) in general population. Summary of Background Data. Precise understanding of the mechanisms leading to DD development is lacking. In a degenerating disc, mechanical and structural changes lead to further worsening of disc integrity. Increasing attention has been paid to vertebral endplate defects as having a possible role in the etiopathogenesis of DD. Methods. The study population comprised 831 twin volunteers from TwinsUK (mean age 54 +/- 8 yr, 95.8% female). Lumbar T2-weighted magnetic resonance images were coded for endplate defects from 8310 endplates into six grades. Total endplate score (TEP score) was achieved by summing both endplate defect grades from the same disc level. DD was evaluated using two different classifications; Pfirrmann grading, and a quantitative trait for DD based on a 4-point grading system. Multivariable regression analysis was used to determine relationships between the traits of interest and the known risk factors for DD, age, and body mass index (BMI). A receiver operator curve for TEP score predicting DD was generated, and survival analysis paired with Cox proportional hazards models analysis performed. Results. There was statistically significant association between DD and age and BMI. These associations lost significance when TEP score was included as predictor in multivariable model. TEP score was strongly and independently associated at every lumbar disc level with DD (Pfirmann P <= 0.001; 4-point grading systems P < 1e-16). A cut-off point score of 5 for TEP score was found above which there was a higher DD prevalence. Across all age subgroups, probabilities of having DD were significantly increased in those considered TEP score positive (>= 5). Conclusion. Our large, population-based study has shown that endplate defect was strongly and independently associated with DD at every lumbar disc level. These results provide a mechanism by which increasing age and BMI predispose to DD.