Cifuentes M, Willetts J, Wasiak R.
From the Center for Disability Research at the Liberty Mutual Research Institute for Safety (Dr Cifuentes and Ms Willetts) and University of Massachusetts Lowell (Dr Cifuentes), Hopkinton, Mass; and Center for Health Economics & Science Policy at United BioSource Corporation, London, United Kingdom (Dr Wasiak).
METHOD: A total of 894 cases followed 1 year using workers’ compensation claims data. Provider types were defined for the initial episode of disability and subsequent episode of health maintenance care.OBJECTIVES: To compare occurrence of repeated disability episodes across types of health care providers who treat claimants with new episodes of work-related low back pain (LBP).
RESULTS: Controlling for demographics and severity, the hazard ratio [HR] of disability recurrence for patients of physical therapists (HR = 2.0; 95% confidence interval [CI] = 1.0 to 3.9) or physicians (HR = 1.6; 95% CI = 0.9 to 6.2) was higher than that of chiropractor (referent, HR = 1.0), which was similar to that of the patients non-treated after return to work (HR = 1.2; 95% CI = 0.4 to 3.8).
CONCLUSIONS: In work-related nonspecific LBP, the use of health maintenance care provided by physical therapist or physician services was associated with a higher disability recurrence than in chiropractic services or no treatment.
From the Full-Text Article:
Low back pain (LBP) continues to be one of the costliest work-related injuries in the United States in terms of disability and treatment costs. [1, 2] An additional, important component of the human and economic costs is the recurrence of LBP.  Recurrences of LBP are complex to study because of the difficulty in predicting recurrence and the varying definitions and measurements of recurrence. [4–9] So far, there has been little success in preventing recurrent LBP with few studies to investigate this topic. More evidence is needed to understand recurrent LBP and justify interventions to prevent recurrence.
Health maintenance care is a clinical intervention approach thought to prevent recurrent episodes of LBP. It conceptually refers to the utilization of health care services with the aim of improving health status and preventing recurrences of a previous health condition. Breen’s original definition of health maintenance care [10, 11] refers to “treatment after optimum recorded benefit was reached.” The definition of optimum is subject to interpretation, making it difficult to clearly distinguish curative treatment from health maintenance; it blends the public health concepts of secondary prevention (treatment and prevention of recurrences) with tertiary prevention (obtaining the best health condition while having an incurable disease).  Health maintenance care can include providing advice, information, counseling, and specific physical procedures. [10–12] Health maintenance care is predominantly and explicitly recommended by chiropractors, although some physical therapists also advocate health maintenance procedures to prevent recurrences.  Physicians do not use this terminology when assisting a patient that has reached an optimum level.
There have been few scientific studies to evaluate the effectiveness of health maintenance care. A 2008 review found only 13 eligible citations and did not arrive at any conclusion about its effectiveness, and the operational definitions of health maintenance care were vague at best.  None of these citations referred to work-related LBP.
In the occupational health field, sustained return-to-work is considered an important goal during injury recovery. Given the patient’s condition and context, going back out of work is considered an appropriate measurement of a recurrent condition because it reflects the non-sustainability of working and implies a failure of the return-to-work process. However, it is possible that different providers focus more on return to work (eg, chiropractors) than others (eg, physicians that could focus more on pain control). An association between specific type(s) of treatment or providers and significant recurrence of a condition (measured as recurrent work disability) could imply an important advancement in the treatment of work-related back injuries.
Work-related LBP is often treated by a combination of providers, including chiropractors, physical therapists, and physicians. Given that chiropractors are proponents of health maintenance care, we hypothesize that patients with work-related LBP who are treated by chiropractors would have a lower risk of recurrent disability because that specific approach would be used. Conversely, similar patients treated by other providers would have higher recurrence rates because the general approach did not include maintaining health, which is a key concept to prevent recurrence. Unfortunately, there is no available data that could allow direct characterization of which procedures were specifically product of the health maintenance care approach. Therefore, the present study aims to study the association between provider type during the initial period of return to work and risk of recurrence of disability due to work-related LBP.
A cohort of 894 patients suffering work-related LBP was followed from their first episode of disability through their subsequent return-to-work (health maintenance care period). A tenth of them had recurrent disability due to LBP. After controlling for demographic and severity factors, compared with receiving treatment only or mostly by chiropractors during the health maintenance care period, receiving treatment by physical therapists, physicians, or a combination of both tended to result in significantly higher HRs of recurrent disability. Similarly, when compared to patients treated only or mostly by chiropractors during the disability episode or patients who were “chiropractor loyalists” during transition from the disability episode to the health maintenance care period, patients treated by other care providers tended to have a higher hazard of recurrent disability.
In our study, after controlling for demographics and severity indicators, the likelihood of recurrent disability due to LBP for recipients of services during the health maintenance care period by all other provider groups was consistently worse when compared with recipients of health maintenance care by chiropractors. Care from chiropractors during the disability episode (“curative”), during the health maintenance care period (main exposure variable, “preventive”), and the combination of both (curative and preventive) was associated with lower disability recurrence HRs.
This clear trend deserves some attention considering that chiropractors are the only group of providers who explicitly state that they have an effective treatment approach to maintain health.
Our findings should be viewed in the context of prior research. Few studies have addressed evaluating the effectiveness of health maintenance care.  Most of the reviewed studies found no clear advantage of any health maintenance approach or reported small benefits for the chiropractor maintenance care. A clinical trial found better disability indicators for patients exposed to spinal manipulation,  but no study compared work-related LBP recurrence rate across different providers. In 1999, Carey  found that in ambulatory general practice, the rate of recurrent disabling LBP was not significantly different at 6 months for chiropractors (8%), primary care physicians (9%), orthopedic surgeons (10%), and physicians and mid-level practitioners working as health maintenance organization staff (14%). The same nonsignificant results were observed at 22 months of follow-up. However, Carey’s study did not consider time to recurrence and did not utilize a multivariate model, which might have provided different results.
SUGGESTED MECHANISM OF THE CHIROPRACTOR ADVANTAGE
Our results, which seem to suggest a benefit of chiropractic treatment to reduce disability recurrence, imply that if the benefit is truly coming from the chiropractic treatment, there is a mechanism through which care provided by chiropractors improves the outcome. It is always possible that unknown patient differences, which we were not able to control for, could be acting as unadjusted confounders and eventually explain the findings. With those caveats, we dare to speculate that for the purpose of preventing disability recurrence in cases of work-related LBP, the main advantage of chiropractors could be based on the dual nature of their practice. On one hand, it is the do-nothing approach: by visiting only or mostly a chiropractor or becoming a chiropractor loyalist, the patients do not receive other traditional medical approaches. In fact, there is a continuous struggle between chiropractors and orthopedic providers regarding the most basic principles that sustain each others’ clinical practice.  There is a growing evidence that health-care-as-usual does not necessarily improve health outcomes in nonspecific LBP. [25, 26] This hypothesis is supported by our finding that, after controlling for severity and demographics, no health maintenance care is generally as good as chiropractor care. Therefore, not as a conclusion but a hypothesis, chiropractors might be preventing some of their patients from receiving procedures of unproven cost utility value  or dubious efficacy. [25, 26]
This argument has to be tempered by the fact that the most numerous group for a continued relationship with the provider (disability episode and health maintenance care) are the switchers (55 of them) and the any other combination (163 of them) groups, which together compose approximately 24% of the study group. The reasons why a small group of patients chose to switch or to combine providers during the health care maintenance period might be related to their good outcome, which is indistinguishable from the reference group. In others words, it may be possible that those switchers and any other combination groups for some reason knew what the best health care path was for them.
On the other hand, chiropractors argue that their aim is to provide care while being centered on the whole patient. It is possible that this approach provides more opportunities for a provider–patient relationship that improves communication, and likely emphasizes the importance of return to work over symptom control, and focuses on psychosocial issues that have been demonstrated to be important in the evolution of LBP disability.  Some of the important weakness of this hypothesis is the fact that we are attributing to a whole job title attributes that vary among individual providers. Do chiropractors truly emphasize in their practice relationship quality and communication? Do patients of non-chiropractor providers who focus on personal relationship and good communication have better health outcomes than those patients whose providers do not do so? Some studies seem to point in that direction.  In addition, it is important to state that this considered mechanism is not at all a chiropractor exclusivity and other care providers may similarly think along these lines. Naturalistic studies that focus on the actual experiences of the provider–patient relationships could help to test our proposed mechanisms.