The difference in the anteroposterior diameter of the upper and lower endplates of adjacent vertebral bodies is a significant, and probably independent, risk factor, a study ahead of print in The Spine Journal reports.
The authors of the study, Masoud Pouriesa (Department of Radiology and Neurosciences Research Center, Imam Reza Medical Center, Tabriz University of Medical Sciences, Iran) and others wrote that in their experience, “a remarkable disproportion between the endplates of two adjacent lumbar vertebrae with relevant disc herniation could be spotted on midsagittal MRI”. They added: “The objective of this present study was to examine possible association of this disproportion with the presence of intervertebral disc herniation at the same level in a case-control setting.”
Pourisea et al, using midsagittal MRI to image the spine, calculated the difference between the anteroposterior diameter of the upper endplate and the anteroposterior diameter of the lower endplate of the vertebrae neighbouring a herniated intervertebral disc in 250 patients with confirmed primary lumbar disc herniation. They then compared these findings with the difference in endplate diameter in age- and sex-matched controls without lumbar disc herniation.
The authors found that the mean difference in endplates was significantly higher in patients with herniated discs at L4–L5 and L5–S1 levels compared with the difference in endplates at the corresponding levels (p<0.001) in the control patients. This difference between the two groups remained significant even after adjustment for the patients’ sex, age, height, weight, and body mass index. Pourisea et al reported: “Each 1mm increase of difference in endplates at L4–L5 and L5–S1 levels are associated with 53% and 56% elevation in disc herniation risk at the corresponding levels, respectively.” However, while patients with a herniated disc at level L2-L3 had a higher mean difference in endplates than control patients (at corresponding levels), this difference was marginally insignificant (p=0.07).
Summarising their findings, the authors stated: “Disproportion between two endplates was shown to be a common finding in a pair of neighbouring lumbar vertebrae adjacent to a herniated disc.” They added that this finding was prominent in lower segments, particularly at L4–S1 levels, and that the difference in endplates could be regarded as a “significant and probably independent risk factor for lumbar disc herniation”. According to Pourisea et al, “this variable could be used successfully to screen individuals at higher risk of disc herniation than the normal population.”
Study author Rohollah Fouladi, Department of Radiology and Neurosciences Research Center, Imam Reza Medical Center, Tabriz University of Medical Sciences, Iran, told Spinal News International: “The scant number of the patients with extruded herniated disc, along with no case of sequestrated herniation, in this study limited the outcome in examining any possible effect attributable to the difference of endplates on the degree of disc herniation. Furthermore, it is not yet definitely cleared that the discussed disproportion was a causative factor in the emergence of disc herniation, or just a sheer consequence of previously developed one. Thus, further studies, particularly long-term longitudinal ones, merit to be carried out in this regard. They would be appropriate for defining age- and sex-adjusted optimal cut-off points of difference in endplates for clinical purposes.”