In the two Danish population-based reports, by Kjaeret al8 and Bendix et al,7 participants were asked whether they had had “trouble with the lowest part of the back” during the past 7 days, past month, or past 12 months. In a report of an occupational cohort of men which included ambulance men, hospital porters, car production workers, draymen, and office personnel by Savage et al,17 participants were divided into the following four groups: (1) no LBP ever, (2) LBP in the past, but not the 12 months preceding the MRI scan, (3) LBP in the 12 months preceding the MRI examination, but not every month, (4) LBP at least once a month in the 12 months preceding the MRI scan. Although we selected only those who had responded that they had LBP during the past 12 months, it is not clear that respondents experienced pain consistently during that time. The two other studies more clearly indicated back pain duration as longer than 3 months.18,19 No additional information on the duration or frequency of episodes of pain was provided. The presence or absence of leg pain and the characteristics of that leg pain (radicular or not) were not clearly reported in most studies.
Patient characteristics which might influence the presence of CLBP (e.g., physical activity, body mass index) and demographic information were poorly reported in most studies. The population-based study was among 40-year-olds8 and one study in military personnel reported a mean age of 19.8 years for participants.18 In the occupation-based study, 52.3% of participants were 20 to 30 years old.17 Paajanen et al19 reported on the following multiple age groups: 10 to 14 years old (4.7%), 15 to 19 years old (33%), 20 to 29 years old (32%), 30 to 39 years old (12.5%), and 40 to 49 years old (16.8%).
The MRI systems used in all, but one of the studies, were lower-resolution systems of 0.2 T or less.7,8,18,19 Only one study (Savage et al17) used a higher-resolution system (1.5 T).
The odds of CLBP given the presence of disc degeneration ranged from 1.8 to 2.8 across the four reports (Figure 3).8,17–19 In the population-based study of 40-year-olds in Denmark (n = 412), the presence of disc degeneration was associated with significantly increased odds of LBP (OR = 2.6, 95% CI: 1.6–4.1).8 In a separate analysis of the same study population, which used different criteria to define disc degeneration, the odds of CLBP was 0.5 (95% CI: 0.4–0.9) if the patient had gray discs but no black discs. The odds of CLBP in patients with black discs without gray discs was 2.1 (95% CI: 1.0–4.9), and the odds of CLBP in patients with both black and gray discs was 2.1 (95% CI: 1.3–3.5).7
Among the occupational cohort studies, the association between CLBP and disc degeneration was significant in the study among young military personnel (OR: 2.8, 95% CI: 1.4–5.5)18 but not significant in the other study which included a range of occupations.17 This latter study did not provide sufficient data to determine the associations between CLBP and degenerative MRI changes for individual occupations.
Paajanen et al19 reported on the presence of CLBP and disc degeneration by MRI for various age groups. Estimates of the association between disc degeneration and CLBP stratified by age were statistically significant in all age groups.19 The odds of CLBP with degenerative discs for those 10 to 19 years old and those 20 to 29 years old were similar (OR: 2.3, CI: 1.0–4.7) but were higher (OR: 3.9, CI: 1.3–14.1) for those 30 to 49 years old. However, the CI for this group was wide (Figure 4; see Supplemental Digital Content 1, http://links.lww.com/BRS/A537).
Two studies reported the prevalence of disc protrusion8,18; however, the definitions differed substantially between these studies as did the participant populations (Figure 5). In the largest of these studies (N = 412)—which was population-based and consisted of 40-year-olds—the presence of abnormal disc contour (including disc protrusion, extrusion, or sequestration) was associated with a nonsignificantly increased odds of CLBP (OR = 1.3, 95% CI: 0.7–2.2).8 In the other study, among 19- to 20-year-old military personnel, the presence of disc protrusion (defined as symmetric bulging of disc beyond the margins of vertebral body, having lost normal concavity) was associated with significantly increased odds of CLBP (OR = 3.2, 95% CI: 1.4–7.4).18
The population-based study by Kjaer et al8 reported on the prevalence of several additional MRI abnormalities among subjects with and without CLBP (Figure 6). The presence of reduced disc height, annular tear, high-intensity zone, and modic changes were each independently associated with significantly increased odds of CLBP (reduced disc height: OR = 2.5, 95% CI: 1.6–4.0; annular tear: OR = 2.0, 95% CI: 1.3–3.3; high-intensity zone: OR = 2.5, 95% CI: 1.5–4.0; modic changes: OR = 4.2, 95% CI: 2.1–9.2). This study reported no association between the presence of endplate changes or Z-joint degeneration and CLBP (see Supplemental Digital Content 1, http://links.lww.com/BRS/A537).
In the Absence of Deformity or Symptomatic Neural Compression, Is the Surgical Treatment of Degenerative MRI Changes Associated With Different Outcomes Compared With Nonsurgical Treatment?
There were no studies, which directly compared outcomes of surgical and nonsurgical treatment of individuals based only on degenerative MRI changes as specified for this review (Figure 7).
The strength of the overall body of evidence based on application of GRADE16 is summarized in Table 2. It was considered to be “insufficient” regarding the association between disc degeneration and CLBP. MRI findings of disc degeneration do not appear to represent a direct link to the presence of CLBP. Degenerative MRI changes may be present in patients without CLBP and may not be present in patients with CLPB. In addition, LBP definitions were broad and varied in the studies; there were variations in how disc degeneration was defined, and the populations were very different across studies. Moreover, cross-sectional studies do not allow for causal inference.
The strength of the overall body of evidence was considered to be “insufficient” with regard to the association between disc degeneration on MRI and CLBP for specific age groups because only one study was available (Table 3).
The strength of the overall body of evidence was considered to be “insufficient” with regard to the association between MRI findings of disc protrusion and CLBP. There is some inconsistency and imprecision as well as indirectness. One study was among 40-year-old military personnel, the other in 19-year-old military personnel.
The strength of the overall body of evidence was considered to be “insufficient” with regard to whether surgical treatment of degenerative MRI changes (as defined by the inclusion/exclusion criteria) is associated with different outcomes compared with nonsurgical treatment. No studies that directlycompared these treatment options in the same underlying population were found to specifically address this question.
Degenerative MRI changes are present in both patients with CLBP and in patients without it. Although the data do suggest that patients with back pain tend to have a higher prevalence of degenerative changes on MRI, it is unclear if these degenerative changes are indeed the cause of the back pain based on these cross-sectional studies. Even with the observed associationof certain degenerative MRI changes with CLBP, it is not an absolute direct link. Furthermore, obtaining an MRI to discover such degenerative changes does not necessarily result in alteration of treatment. However, it should be emphasized that clinical suspicion of such worrisome pathologies as infection or neoplasm, based on a thorough history and physical examination should not preclude obtaining an MRI. In addition, the presence of neurologic symptoms should warrant an MRI, depending upon clinical presentation, and patients with neurologic symptoms should not be treated in the same category as patients with CLBP. In the absence of other clinical factors that would raise the suspicion for other pathologic processes, the yield of routine MRI for CLBP is low.
Although there have been studies evaluating the surgical treatment of LBP, there is no study that has based this surgical treatment exclusively on MRI findings. Many of these studies also included discography, computed tomography (CT), or plain radiographs to evaluate criteria for surgical treatment. Since our systematic review focused specifically on degenerative MRI findings, we excluded all of these studies. This is reflective of both the difficulty in identifying a cause of CLBP and the limitations of MRI in this setting.
Strengths of this study include the systematic approach to searching for and evaluating relevant studies to answer a well-defined clinical question. Combined with use of specified inclusion/exclusion criteria defined a priori, this approach enhances the validity of this report and facilitates identification of specific gaps in understanding if degenerative MRI changes are associated with CLBP.
This review suggests that findings of degenerative disc changes on MRI may be associated with CLBP. However, several limitations must be kept in mind. First, the included studies were cross-sectional, and in such studies it is not possible to know how long the MRI findings would have been present relative to the timing (or real duration) of the back pain. In other words, the temporal sequence of findings and symptoms(or symptom duration) is not known; thus, no causal inference can be made. Second, the definitions of CLBP varied across studies and the presence, absence, or characteristics of any associated leg pain were poorly reported. Concerns related to definitions of CLBP and inclusion of two articles were resolved by consensus. The first article, by Savage et al,17 had a heterogeneous group of patients with differing times of back pain, separated into four groups. Group number 4 was defined as patients having back pain for the past 12 months at least once a month. This last group met our definition of CLBP and these data could be culled from the manuscript separately. The second article, by Kjaer et al,8 included patients with back pain in the, “past 7 days,” “past month,” and “past 12 months.” Only data from the later group were included in these analyses as this definition was most likely to capture those with CLBP. However, it is possible that those with more acute LBP were among the respondents in this group. It appears that the OR estimates and CI ranges for this group (Figure 3) are reasonably consistent with other studies whose definitions were more closely aligned with our CLBP definition. This may suggest that the group is likely to have captured those with CLBP. The primary strength of the article by Kjaer et al8 is that it is population-based and includes a broad spectrum of people, allowing for a better determination of the true prevalence of CLBP in this population of 40-year-olds. It was the only population-based study found that had a group that was likely to include CLBP and that had evaluated the association between degenerative MRI changes and CLBP; it was therefore retained. Even though a statistically significant association between various MRI changes and back pain was observed for the Kjaer et al8 data, it is unclear how much of this association may be attributable to those with CLBP as defined in our article.
Definitions of CLBP that appeared to most closely reflect the inclusion/exclusion criteria for this review were chosen. However, a degree of misclassification of individuals (in all studies) with regard to those criteria is likely because those definitions still lacked the precision needed to explicitly delineate persons with CLBP as defined for this article. Similarly, there were differences in how MRI findings were defined. The terms used for degeneration were not consistent across all studies. Another factor relates to the resolution of the MRI equipment used in most studies; all but one study used MRI strengths of 0.2 T or less. The extent to which this may influence the delineation of specific MRI findings is not clear. Finally, the prevalence ORs presented are crude and do not adjust for potential confounding factors which may be associated with both CLBP and degenerative MRI changes. We are not able to calculate adjusted ORs since subject-level data on potential confounders was not provided by any study. None of the studies presented adjusted estimates, but one did stratify results by age group.
The absence of comparative studies evaluating outcomes of surgical treatment compared with nonsurgical treatment in patients with degenerative MRI changes precludes us from making any conclusions on the efficacy of such surgical treatment. Many noteworthy studies have been published regarding surgical versus nonsurgical studies for back pain; however, these do not exclusively base their inclusion criteria on MRI, which is our specific clinical question.20 Many of these studies included discography, plain radiographs, or CT to identify possible pain generators; such studies did not exclusively use MRI for preoperative evaluation.
Many papers, which have evaluated degenerative MRI changes and CLBP or CLBP and surgical treatment failed to meet our inclusion criteria for various reasons. For instance, in a recent study by Ohtori and coworkers,21 participants with discogenic LBP of at least multiyear duration, specific MRI findings of degenerative disease, and positive discogram or discoblock were randomized to surgery or minimal treatment. In this small study (N = 41) of highly selected patients, at 2 years posttreatment, surgical patients had significantly improved visual analog scale, Japanese Orthopedic Association, and Oswestry Disability Index scores.21 These results may not be generalizable to patients who did not have positive discogram or discoblock. Because our review excluded discography and only focused on MRI changes, we did not include this manuscript. In addition, other studies, which have shown improvement in patient outcomes after the surgical treatment of LBP, did not base treatment exclusively on MRI changes (discography and CT were also used).20 Several articles reported estimates of the prevalence of MRI abnormalities among healthy individuals without LBP4,6,22,23; however, they did not provide comparison prevalence estimates among individuals with CLBP, precluding calculation of a prevalence odd ratio. In addition, the prevalence of MRI abnormalities in persons without LBP in these studies was high:
- Kanayama et al: MRI abnormalities in up to 60% to 80%; up to 50% of discs had evidence of herniation, Schmorl's nodes in 4.0% to 9.5% and high-intensity zone in 10% to 24% of discs, up to 35% had herniation.4
- Jensen et al: Sixty-four percent had abnormalities at one or more level; 52% had bulge at one or more level, 27% had protrusion, 1% had extrusion; 19% Schmorl's nodes.6
- Boden et al: Twenty-eight percent had a substantial abnormality; 24% had herniated disc.22
- Borenstein et al: At baseline 36% had one or more abnormal MRI finding (16% herniation, 8% stenosis, 12% disc bulge, 4% degeneration).23
Other recent studies not only evaluated the association of degenerative MRI changes and back pain but also failed to meet our inclusion criteria. Cheung et al3 reported MRI changes and back pain in more than 1000 individuals. This study was excluded, however, because back pain was defined as, “pain in the low back of more than 2 weeks duration,” which does not meet our criteria of CLBP (defined as LBP for 3 months or more). Carragee et al24 also reported a study evaluating the association between back pain and MRI changes. This study followed patients for 5 years to see if first time episodes of back pain were associated with MRI changes. Their definition of back pain was pain more than 1-week duration, which failed to meet our definition of CLBP.24 Jarvik et al25 evaluated back pain in initially asymptomatic for 3 years. In those 3 years, 67% of patients had an incidence of pain; however, they included radiculopathy in their definition of pain. Moreover, 20% had either stenosis or spondylolisthesis. Thus, because of the radicular nature and deformity (spondylolisthesis) of many of these patients, it failed to meet our inclusion criteria of CLBP and was excluded.25 Finally, Takatalo et al5 reported on the association between disc degeneration and LBP. They found that although there is more of an association of back pain with moderately degenerated discs than mildly degenerative discs, one-third of asymptomatic patients had degenerated discs. Moreover, the patients were categorized by cluster analysis, and this did not allow us to extract the data to evaluate the association between degenerative MRI changes and CLBP based on definitions set forth in the methods.5
Although a statistically significant association was noted between the presence of disc degeneration on MRI and CLBP, it is questionable if the estimates accurately represent the association. This is largely due to the overall quality of studies found and the lack of a direct link between degenerative MRI changes and CLBP. In addition, heterogeneity across studies with regard to the imaging and clinical phenotypes, definitions of MRI findings, populations, and sampling methods need to be considered. This heterogeneity, combined with concerns regarding study quality and design, precluded meaningful statistical pooling of data. Despite the observation of a statistical association between some MRI changes and CLBP in the included studies, the clinical significance of degenerative findings is unclear. These considerations prevented us from advocating routine MRI use in patients with CLBP based on the current evidence.
Only limited conclusions based on the association of degenerative MRI findings and CLBP are possible in this study because all studies were cross-sectional in design; thus causal relationships cannot be assessed. Methodologically rigorous longitudinal prospective studies (preferably population-based) that use precise definitions of CLBP and predefined criteria for MRI changes need to be conducted to confirm and better define the relationship between specific MRI changes and development of CLBP. Similarly, rigorous studies that compare the outcomes of patients from the same underlying population who are treated surgically with those who are treated nonsurgically are needed to delineate the relative benefits and risks of treating patients with degenerative MRI changes. This study should raise awareness regarding the need for more standardized phenotypic definitions of CLBP and their inclusion as part of methodologically rigorous studies.
- There may be an association between degenerative MRI changes and CLBP, but this association must be considered within the context of study quality and the lack of a direct link between degenerative MRI findings and the presence of CLBP.
- In the absence of deformity or symptomatic neural compression, there is no evidence to demonstrate that surgical treatment of degenerative MRI changes leads to improved outcomes over nonoperative care.
- Strong recommendations are made against routinely using MRI for the workup for CLBP and against the surgical treatment of CLBP based solely upon degenerative MRI changes.
Supplemental digital contents are available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.spinejournal.org).
The authors thank Ms. Nancy Holmes, RN, for her administrative assistance.
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