Friday, August 16, 2019
Do Modic changes predict long-term outcomes?
Since Modic changes (MC) were first described over 30 years ago, spine care practitioners have struggled with how to interpret the imaging finding. Their etiology remains obscure, with hypotheses ranging from inflammation to microinjury to infection. The literature on the association between MCs and low back pain (LBP) is mixed, and there is scant data on the role of MCs as long-term prognostic indicators. In order to better assess the association between MCs and long-term back pain outcomes, Dr. Udby and colleagues from Denmark studied 170 chronic LBP patients enrolled in an RCT comparing cognitive training and PT who had a baseline lumbar MRI and follow-up 13 years after the original MRI. The original study included 204 patients and found no difference in outcomes with the cognitive training and PT. At baseline, 40% of patients had MCs (the majority of which were MC Type I), the average age was 41, and just over 50% were female. There were no significant baseline differences between the MC+ and MC- groups in terms of demographic characteristics, pain, or function. At 13 year follow-up, the MC+ group had significantly better Roland-Morris Disability Questionnaire scores (7.4 vs. 9.6) and significantly fewer sick leave days related to LBP over the past year (9 vs.23). Other outcome scores were similar between the two groups, with some trends towards slightly better long-term outcomes in the MC+ group.
This is an interesting study that suggests that MCs are not a negative prognostic indicator in the long-term. A key aspect of the study to understand is that all patients had chronic LBP at baseline (reporting LBP in at least 4/12 months prior to enrollment). Most population-based studies have found at least some association between MCs and LBP, though this association seems much weaker or non-existent in the chronic LBP population. This study also did not include follow-up MRI, which the authors explained was due to changes in MRI technology, namely the use of much higher Tesla magnets over time. They felt that comparing the findings of a modern high Tesla MRI to the low Tesla magnet used in 2004-2005 would have biased the results. There is fairly good data in the literature documenting the changes in MCs over time, though how this relates to clinical outcomes is less clear. The authors hypothesized that the MC+ patients may have had somewhat better long-term outcomes as compared to the MC- patients as the inflammation associated with MCs tends to subside over time, which could result in less LBP. The MC- patients may have had a different underlying pathology which was less likely to improve spontaneously. The magnitude of the outcome differences between the two groups was relatively small, so concluding that MC+ patients have meaningfully better long-term outcomes is a bit of a stretch. However, the data strongly suggest that MCs are not a negative prognostic factor in the chronic LBP population and should probably not be used to predict outcomes or guide treatment. Thirty years after their description, the spine community still does not know what to make of MCs.
Please read Dr. Udby's paper in the September 1 issue. Does this change your view of how you consider MCs in your practice? Let us know by leaving a comment on The Spine Blog.
Adam Pearson, MD, MS
Associate Web Editor