Abstract

INTRODUCTION

A lot of studies in current literature described the etiology, epidemiology and clinical relevance of MCs. However, there are few studies on the correlation between MCs and Hounsfield units value of vertebral marrow and endplate.
Objectives: To evaluate the changes of Hounsfield units (HU) value in different types of Modic changes (MCs) and to analyze the correlation between the change of HU value and area ratio of MCs region, bone mineral density (BMD), and degree of intervertebral disc degeneration.
Methods: One hundred fifty-eight endplates with MCs were included and analyzed. HU values of MCs regions and adjacent vertebral corresponding regions without MCs were measured. The area ratio of MCs region was defined as the area of MCs divided by the area of endplate or the vertebral sagittal plane. BMD was measured by Dual-energy x-ray absorptiometry (DXA). Degree of intervertebral disc degeneration was evaluated based on Pfirrmann classification. According to the types of variables, descriptive statistics, Kolmogorove-Smirnov test, paired t-test, Wilcoxon signed-rank test, Independent-Samples T Test, and Pearson correlation analysis were used.
Results: The HU values in any types of MCs are significantly higher than that of adjacent vertebral corresponding regions without MCs (P< 0.001). The HU value of the type III MCs is higher than that of the type I and type II MCs.HU value was positively correlated with BMD. In the levels with Grade V disc degeneration, the area ratio of MCs region was significant increased.

DISCUSSION

In our study, all types of MCs were included to evaluate the change of HU values in different types of MCs. Our findings show that the HU values of MCs regions were significantly higher than those of the corresponding regions in adjacent vertebra without-MCs, regardless of the endplate region and bone marrow region. The HU value in type III was higher than that in type I and II. In type I and type II, we found HU values slight decreased in very few cases. As we all know, higher HU value is associated with more severe endplate sclerosis. Our results showed that osteosclerosis may coexist with fat deposition and inflammatory reactions. In addition, the consistency between axial plane and sagittal plane suggested the error of our measurement was negligible. Our study was a quantitative measurement and provided accurate information. We could infer that the pathological process of MCs might be osteosclerosis. We think that as the area ratio of MCs region gets larger, chronic lower back pain will become more severe. We also found that there was a positive correlation between the area ratio of the endplate and the area ratio of the sagittal plane, which proved that the diffusion of MCs was simultaneous to the endplate and the vertebral body.
Conclusions: HU values of the vertebral endplate and bone marrow were increased in most MCs regions with all types of MCs. HU value of endplates had a significantly positive correlation with BMD. Higher area ratio of MCs region is associated with more severe intervertebral disc degeneration.