Introduction:

Modic Changes (MC) in the lumbar spine are regularly associated with clinical and histo-immunological parameters. The etiology of MC is however only minimally studied, and a causal relation is thus difficult to establish. Insufficient vascularization of the endplate is proposed as a contributor to the appearance of MC on MRI. In this study, we chose to study aorta calcification as a representation of vascularization status. The presence of aorta calcification can lead to an explanation in two ways. On the one hand, it is conceivable that calcification of this large blood vessel is a (direct) indicator of reduced blood supply in the exiting vessels (which supply the endplates). On the other hand, it is possible that the aortic calcification is representative of the patient's overall vascular condition (indirect indicator).

Methods:

We reviewed the radiological imaging results of patients operated between November 2005 and November 2013, who received instrumented surgery for lumbar degenerative disc disease. Type and severity of Modic changes were assessed by MRI, and AAC was assessed by CT or, if CT was not available, fluoroscopy of the lumbar spine. The severity of MC and AAC were scored according to the proportion of abnormal signal range in the vertebral body (MC) and the grade of arterial calcification (AAC) (0-3 points indicated increasing severity in sequence). In addition, scores were dichotomized as well and graded as minimal (0,1) or relevant (2,3). Subsequently, the correlation between MC and AAC was studied by Pearson statistical analysis of the data, in which the influence of age on both parameters was studied as well (partial correlation).

Results:

130 patients met the inclusion criteria. The mean age of patients was 59±12 years, men and women equally represented. 113 (87%) patients demonstrated MC, of which 71 had Modic type 2. The majority of patients had relevant MC (55%). Eighty-eight (68%) of the 130 patients had abdominal aorta calcification. Almost half of the patients (43%) demonstrated relevant AAC. Pearson statistical analysis showed that AAC was correlated with age (coefficient=0.544, P=0.00), but that there was no correlation between age and the presence of MC (coefficient=0.129, P=0.142). The severity of AAC was significantly correlated with the severity of MC (P=0.002), which remained significant after adjusting for age (P=0.040).

Discussion:

This study showed that the AAC and MC are associated and that it is reasonable to speculate on the causal relation. Reduced blood flow due to atherosclerotic disease may indeed play a role in the formation of endplate degeneration, represented on MRI as MC, and induce low back pathology. Future research should focus on the specific elements contributing to AAC (obesity, smoking, abnormal serum lipid levels, immobility) and their influence on low back pathology parameters.