Theoretical Schemas to Guide Back Pain Consortium (BACPAC) Chronic Low Back Pain Clinical Research.

BACKGROUND: Chronic low back pain (cLBP) is a complex with a heterogenous clinical presentation. A better understanding of the factors that contribute to cLBP is needed for accurate diagnosis, optimal treatment, and identification of mechanistic targets for new therapies. The Back Pain Consortium (BACPAC) Research Program provides a unique opportunity in this regard, as it will generate large clinical datasets, including a diverse set of harmonized measurements. The Theoretical Model Working Group was established to guide BACPAC research and to organize new knowledge within a mechanistic framework. This article summarizes the initial work of the Theoretical Model Working Group. It includes a three-stage integration of expert opinion and an umbrella literature review of factors that affect cLBP severity and chronicity. METHODS: During Stage 1, experts from across BACPAC established a taxonomy for risk and prognostic factors (RPFs) and preliminary graphical depictions. During Stage 2, a separate team conducted a literature review according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to establish working definitions, associated data elements, and overall strength of evidence for identified RPFs. These were subsequently integrated with expert opinion during Stage 3. RESULTS: The majority (∼80%) of RPFs had little strength-of-evidence confidence, whereas seven factors had substantial confidence for either a positive association with cLBP (pain-related anxiety, serum C-reactive protein, diabetes, and anticipatory/compensatory postural adjustments) or no association with cLBP (serum interleukin 1-beta / interleukin 6, transversus muscle morphology/activity, and quantitative sensory testing). CONCLUSION: This theoretical perspective will evolve over time as BACPAC investigators link empirical results to theory, challenge current ideas of the biopsychosocial model, and use a systems approach to develop tools and algorithms that disentangle the dynamic interactions among cLBP factors.

Correlation of paraspinal atrophy and denervation in back pain and spinal stenosis relative to asymptomatic controls.

OBJECTIVE: To determine the relationship among spinal stenosis, back pain, paraspinal muscle denervation, and paraspinal muscle atrophy. DESIGN: A prospective masked, double-controlled study. SETTING: A university hospital and outpatient spine clinic. PARTICIPANTS: Ten asymptomatic subjects, 10 subjects with mechanical low back pain, and 15 subjects with symptomatic spinal stenosis; age range, 55-80 years old. INTERVENTIONS: Magnetic resonance imaging measurements of minimum spinal canal diameter, paraspinal muscle cross-sectional area at the level of the L5-S1 disk, and quantified paraspinal electrodiagnostic testing (MiniPM) were performed by examiners blinded to each other's results and to the participants' clinical information. MAIN OUTCOME MEASUREMENTS: Paraspinal muscle cross-sectional area and MiniPM scores. RESULTS: A paraspinal cross-sectional area decreased significantly from asymptomatic subjects (3872 mm(2)) to subjects with low back pain (3627 mm(2)) and to subjects with spinal stenosis (2985 mm(2)). In the stenosis group, there was a trend toward increased paraspinal denervation in the subjects with severe spinal stenosis, but this was not statistically significant. CONCLUSIONS: Symptomatic spinal stenosis results in greater paraspinal muscle atrophy than low back pain alone. The extent of paraspinal atrophy was not significantly explained by the extent of denervation, thus, it may be reversible, and the role of paraspinal muscle rehabilitation in patients with spinal stenosis deserves further study.