Low back pain (LBP) is among the most common reasons to visit a physician and up to 25% of Americans report an incidence of back pain within the previous three months [1]. Combined direct and indirect costs for LBP are reported to be between $85 billion and $238 billion, and expenditures for back pain are rising more quickly than overall health expenditures [1-3]. While the vast majority of LBP episodes resolve within 2–4 weeks, 25% of patients will experience recurrent episodes within one year and the prevalence of chronic LBP has been reported to be on the rise [4,5].

The Military Health System (MHS) is responsible for providing health care to 10 million active duty and retired military personnel and their dependents, representing one of the largest single payer health systems in the United States. Prevalence estimates for LBP within the MHS are similar to the rest of society [6]. High costs of treatment for LBP and its impact on readiness of active duty members make LBP a particular concern for the MHS. LBP is the leading cause of medical discharge across all military services [7] and has been associated with high rates of medical evacuation from deployment [8]. Back pain in active duty members, as in civilian populations, is often accompanied by psychological distress, [9] increasing the risk for persistent pain and disability. Opioid medications are also frequently overused as an initial strategy for managing pain conditions such as LBP, a particular concern for the MHS, [10]. The need to improve the management of patients with pain has become a priority for the MHS [11].

Recommendations in clinical guidelines for acute, non specific LBP in both military and civilian settings are to avoid opioids as a first-line medication and avoid advanced imaging procedures such as MRI or CT scan [12-16]. However, research conducted mostly in civilian settings demonstrate clinical practice remains inconsistent with these recommendations, [17] with excess use of unendorsed care early in the care process contributing to the high costs of managing LBP, adverse events, and increasing risk of chronicity [4,17]. Several guidelines suggest a delay in referral to physical therapy for 2–4 weeks to allow for spontaneous recovery, [12,15,16] but emerging research with civilian populations has found cost savings when referrals to physical therapy occur early in the care process for patients with acute LBP symptoms, particularly if the physical therapy care provided focuses on active treatment approaches [18,19].

Further research is needed to delineate optimal LBP care pathways for comprehensive single payer settings such as the MHS that could be a model for other health care delivery systems and payment models [20]. Therefore, our goal in this study was to evaluate the impact of both the timing and adherence of physical therapy for individuals with LBP within the MHS alone and in combination on health care costs and utilization of advanced imaging, spine injections, surgery, or opioid use. We also sought to determine if the results seen in civilian payer environments with respect to timing and adherence would be observed in the MHS, and given the robust size of the MHS claims database, evaluate the interactions of these factors on outcomes. The issue of optimal care pathways for costly conditions in single payer systems is especially important given that the potential direction of pending health care reform favors consolidation in the United States [21].

This study included a large sample of patients newly consulting a primary care physician for LBP in the MHS and extends our knowledge in several important ways on the implications of timing of care and adherence to practice guidelines for LBP. Unlike previous studies that have examined timing and adherence separately, [18,19] our large sample size examined the implications of both factors. Of particular interest, the 24% of patients who received early physical therapy that was also adherent to practice guidelines had the lowest utilization and costs compared to any of the other 3 possible combinations of timing and adherence. Early and adherent physical therapy was associated with significantly lower utilization of advanced imaging, lumbar spinal injections, lumbar spine surgery, and use of opioids. Given the enormous burden of excessive and unnecessary care for patients with LBP on society, cost savings from early guideline adherent physical therapy has important implications for single payer health care systems to design optimal care process models for LBP.

Compared to delayed and adherent physical therapy, patients receiving early and adherent physical therapy had 60% lower total LBP-related costs during the 2-year follow-up period (Table 4). Non-LBP healthcare and inpatient costs were also 13% and 24% lower, respectively, with early and adherent care, suggesting accretive health benefits from physical therapy that extend beyond the primary reason for seeking treatment (Table 4). In fact, when considering the various combinations, a dose–response relationship appears to exist in the sense that the results show a progressive increase in subsequent utilization and costs as care shifts from being classified as early and adherent compared to late and non-adherent care.

Although speculative, there are several possible explanations for why this may be the case. When following guideline based treatment, physical therapists provide patients with an active management approach that counter-balances management strategies that foster a sense of dependency in the patient [23]. For example, if physical therapists can assist in developing self-efficacy, it is reasonable to expect that the benefits of doing so would have the greatest impact when implemented early compared to late in the course of care, especially before negative expectations are reinforced and entrenched within the patient’s beliefs. This is in contrast to evidence that early use of advanced imaging, for example, reduces a patient’s sense of self efficacy and optimism for recovery, thus increasing the risk of subsequent procedures such as injection, surgery, and opioid medication [24,25]. For example, providing information on MRI results to patients with acute LBP has been shown to diminish a patient’s sense of well-being [26,27].

Although significant emphasis is being given to the importance of adherence to practice guidelines for costly conditions such as LBP, our results emphasize the importance of better aligning processes of care on two dimensions. However, there may be questions on the weighting of timing and guideline adherence in environments where both factors cannot be manipulated. In this case it seems that timing of referral may be more important. For example, recent studies involving Medicare [19] and commercial insurance samples [18] have demonstrated that early access to physical therapy regardless of adherence was strongly associated with a reduction in subsequent health care utilization and costs, evidenced by reduced risks of advanced imaging, surgery, spinal injections, and opioid use. This reduction in utilization translated into 67% lower total LBP-related costs during the 2-year follow-up (Table 2), reinforcing the notion that, given the inability to effect change in both timing and adherence, optimal timing for seeking care for LBP may overshadow the importance of guideline adherence, at least when studies have considered this factor in isolation. However, as results from this study indicated, there is additional benefit from guideline adherence, and the combination of these factors should be the goal for health care systems wanting to improve outcomes and decrease unwarranted utilization from LBP.

Our results extend the findings from civilian settings by demonstrating an association between early guideline adherent care and utilization and costs in a single payer health system. The MHS is a potential proxy for examining the implications of a single payer system in universal health care, thus the results are important to consider in light of the broader health care reform debate currently taking place in the United States. The fact that all patients had the same payer also mitigates potential differences in outcome based on level of insurance benefit and access to care, which is a common source of confounding in health economics research. Due to this environment, this study also has the advantage of being able to exclude financial incentives as having influenced referral to and utilization of physical therapy. Therefore, it is imperative to examine current guideline recommendations for managing LBP in light of these results.

Most clinical practice guidelines recommend only advice and education for all patients with non-specific LBP during the initial weeks of management, with consideration of psychosocial factors and referral to physical therapy recommended only when recovery is delayed. Psychosocial factors have been identified as risk factors that act as “obstacles to recovery” and increase the risk of developing chronic disability. Our study is unable to determine which patients benefit most from early referral versus those patients for whom self-management is adequate. It is likely that referring all patients with LBP is unnecessary and could increase overall costs. Recent research has demonstrated that targeted interventions to address the individual’s specific modifiable psychosocial prognostic indicators reduces disability, increases quality of life, and lowers health care costs [28]. Additionally, despite guideline recommendations to delay physical therapy, approximately 60% of patients who utilized physical therapy did so within the first few weeks after initial consultation with their primary care provider. A similar pattern has been reported in a commercial claims database in which 53% who went to physical therapy did so within 2 weeks after the primary care visit [18] and Medicare enrollees with a new consultation for LBP in which 75% received care within 4 weeks [19]. Given our current results and emerging evidence from multiple studies across federal and commercial payers that early access to a physical therapist is associated with significant reductions in subsequent health care utilization and overall costs of care, [18,19] recommendations in clinical practical guidelines to delay referral to physical therapy need to be re-examined.

The results of this study should be examined in light of the following limitations. Given the favorable natural history of LBP, many patients improve regardless of treatment. Those referred to physical therapy early are also more likely to have a shorter duration of pain, thus the potential for selection bias to have influenced these results. We accounted for a number of co-morbidities available in the data set and excluded patients with prior visits for LBP to mitigate against this possibility. However, the retrospective observational design of this study imposes limitations on extending the associations we observed to causation. Although we attempted to exclude patients with a specific spinal pathology, it is possible that a few patients may have been inadvertently included in the data set, in which case advanced imaging may be indicated. Additionally, although our results support that early physical therapy which adheres to practice guidelines may be less resource intense, we cannot conclude without patient-centered clinical outcomes (i.e., pain, function, disability, satisfaction, etc.) that the care was more cost effective. Further, it may be that the standard we used to judge adherence to practice guidelines (CPT codes) was not sufficiently sensitive to determine whether care is consistent with clinical practice guidelines. We also did not account for indirect or out-of-pocket costs for treatments such as complementary care, which is common for LBP [29]. However, it is likely that the observed effects on total costs would have been even larger had these costs been considered.

Initial management decisions following a new episode of LBP have profound implications for clinical outcomes and downstream utilization and costs. In this study early referral to guideline adherent physical therapy was associated with lower utilization of advanced imaging, lumbar spinal injections, lumbar spine surgery, and use of opioids. Cost savings from early guideline adherent physical therapy has important implications for designing optimal care process models in single payer systems. Future research is necessary to examine which patients with LBP benefit early physical therapy and determine strategies for providing early guideline adherent care. Randomized controlled studies are also needed to evaluate whether such observational findings are causative before definitive policy recommendations can be made.