Highlights
- Clinician-supported biopsychosocial self-management (SSM) significantly reduced low back disability over 12 months compared to standard medical care.
- Spinal manipulation therapy (SMT) alone did not show a statistically significant difference in disability or pain intensity compared to guideline-based medical care.
- Combining spinal manipulation with supported self-management did not provide additional benefits over self-management alone.
- While disability scores improved in the self-management groups, pain intensity remained largely unchanged across all treatment arms, highlighting a dissociation between functional recovery and pain relief.
Background: The Burden of Low Back Pain and the Chronicity Risk
Low back pain (LBP) remains the leading cause of years lived with disability globally. While the majority of acute LBP episodes resolve within weeks, a significant subset of patients develops chronic, disabling pain that accounts for the vast majority of healthcare costs and productivity losses. Current clinical guidelines emphasize staying active and avoiding unnecessary imaging, yet the transition from acute to chronic pain is often driven by more than just tissue pathology.
The biopsychosocial model posits that psychological factors (such as catastrophizing and fear-avoidance) and social determinants interact with biological processes to influence pain outcomes. Patients identified as being at “high risk” for chronicity—often identified via tools like the STarT Back Screening Tool—require more intensive interventions. However, the optimal first-line strategy for these patients remains a subject of intense debate. Should clinicians focus on passive physical interventions like spinal manipulation, or prioritize active, patient-centered self-management strategies? The PACBACK trial was designed to provide definitive evidence for this clinical crossroads.
Study Design: The PACBACK Factorial Framework
The Prevention of Acute to Chronic Back Pain (PACBACK) trial was a 2 × 2 factorial randomized clinical trial conducted across research clinics at the Universities of Minnesota and Pittsburgh. The study enrolled 1,000 participants between November 2018 and May 2023, with follow-up extending through June 2024.
Participants and Risk Stratification
Eligible participants were adults with acute or subacute LBP (less than 12 weeks’ duration) who were identified as being at moderate to high risk of chronicity using the STarT Back tool. This tool screens for physical and psychosocial prognostic factors, ensuring the study targeted the population most in need of specialized intervention.
The Interventions
Participants were randomized into four distinct groups for interventions lasting up to 8 weeks:
- Supported Self-Management (SSM): Delivered by physical therapists or chiropractors, this intervention focused on biopsychosocial principles, including education on pain physiology, cognitive behavioral strategies, and guided exercise.
- Spinal Manipulation Therapy (SMT): Manual therapy sessions targeting spinal joint dysfunction, a common conservative treatment for LBP.
- Combined Therapy: A combination of both SSM and SMT.
- Medical Care (MC): Guideline-based medical care, serving as the control group.
Key Findings: Disability vs. Pain Intensity
The primary outcomes were measured over one year and included the Roland-Morris Disability Questionnaire (RMDQ) for disability and a numerical rating scale (NRS) for pain intensity.
Primary Outcomes: Roland-Morris Disability Questionnaire
The omnibus test for differences across the four treatment groups was statistically significant for disability (P = .001). The results demonstrated that over the 12-month follow-up:
- SSM Group: Showed a mean disability score of 4.7. Compared to medical care (5.9), the mean difference was -1.2 (95% CI, -1.9 to -0.5), which was statistically significant.
- Combined Group: Showed a mean disability score of 4.8. Compared to medical care, the mean difference was -1.1 (95% CI, -1.9 to -0.3).
- SMT Group: Showed a mean disability score of 5.5. The difference compared to medical care (-0.4; 95% CI, -1.2 to 0.4) was not statistically significant.
Pain Intensity and Secondary Analysis
In contrast to the disability findings, the differences in pain intensity across the groups were not statistically significant (P = .16). Point estimates for pain reduction compared to medical care ranged from only -0.2 to 0 on a 10-point scale. However, when looking at the proportion of “high responders” (those achieving a 50% or greater reduction in disability), the SSM and Combined groups outperformed the others (67% and 65%, respectively, vs. 54% for both SMT and Medical Care).
Expert Commentary: Interpreting the Data
The findings of the PACBACK trial offer a nuanced view of LBP management. While the reduction in disability in the SSM group was statistically significant, the absolute difference (1.1 to 1.2 points on the RMDQ) is relatively small. Critics might argue that this does not reach the commonly cited “minimally clinically important difference” (MCID) of 2 to 3 points. However, in a population at high risk for long-term disability, even small improvements in function across a large cohort can have significant public health implications.
The Dissociation Between Pain and Function
One of the most striking results is the lack of impact on pain intensity despite improvements in disability. This aligns with modern pain neuroscience, which suggests that functional recovery (the ability to work, move, and socialize) can occur even if the sensation of pain persists. Biopsychosocial self-management aims to reduce the *impact* of pain on life, rather than just the intensity of the nociceptive signal.
The Role of Spinal Manipulation
The lack of significant benefit for SMT alone in this specific “high-risk” cohort suggests that for patients with significant psychosocial drivers of pain, passive joint mobilization may be insufficient. SMT may still have a role in acute LBP for low-risk patients or as a secondary adjunct, but the PACBACK data suggests it should not be the primary focus for those at risk of chronicity.
Strengths and Limitations
The study’s strengths include its large sample size (n=1,000), the 2×2 factorial design which allowed for the isolation of intervention effects, and high participant retention (93%). The use of the STarT Back tool ensured a clinically relevant population was studied.
Limitations include the inherent difficulty in blinding participants to physical interventions and the fact that the interventions were delivered in academic research settings, which may differ from high-volume primary care environments. Furthermore, the small effect sizes suggest that even biopsychosocial self-management is not a “silver bullet” for all patients.
Conclusion: Shifting the Paradigm in Acute Back Pain Management
The PACBACK trial provides robust evidence that clinician-supported biopsychosocial self-management is superior to standard medical care for reducing disability in high-risk acute LBP patients. It reinforces the shift away from purely biomechanical treatments toward strategies that empower patients through education, cognitive reframing, and active movement. For clinicians, the message is clear: when treating acute back pain in patients with high psychosocial risk, the conversation should move beyond the spine and toward the person as a whole.
Funding and Trial Registration
This study was funded by the National Institutes of Health (NIH) and the National Center for Complementary and Integrative Health (NCCIH). ClinicalTrials.gov Identifier: NCT03581123.
References
- Bronfort G, Meier EN, Leininger B, et al. Spinal Manipulation and Clinician-Supported Biopsychosocial Self-Management for Acute Back Pain: The PACBACK Randomized Clinical Trial. JAMA. 2025;333(1):34-45. doi:10.1001/jama.2025.21990.
- Hill JC, Whitehurst DG, Lewis M, et al. Comparison of stratified primary care management for low back pain with current best practice (STarT Back): a randomised controlled trial. Lancet. 2011;378(9802):1560-1571.
- Foster NE, Anema JR, Cherkin D, et al. Prevention and treatment of low back pain: evidence, challenges, and promising directions. Lancet. 2018;391(10137):2368-2383.