Clinical Effectiveness and Efficacy of Chiropractic Spinal Manipulation for Spine Pain
A comprehensive review of spinal manipulative therapy's effectiveness and efficacy in managing neck and low back pain.
Abstract
Spine pain is a highly prevalent condition affecting over 11% of the world's population. It is the single leading cause of activity limitation and ranks fourth in years lost to disability globally, representing a significant personal, social, and economic burden. For the vast majority of patients with back and neck pain, a specific pathology cannot be identified as the cause for their pain, which is then labeled as non-specific. In a growing proportion of these cases, pain persists beyond 3 months and is referred to as chronic primary back or neck pain. To decrease the global burden of spine pain, current data suggest that a conservative approach may be preferable. One of the conservative management options available is spinal manipulative therapy (SMT), the main intervention used by chiropractors and other manual therapists. The aim of this narrative review is to highlight the most relevant and up-to-date evidence on the effectiveness (as it compares to other interventions in more pragmatic settings) and efficacy (as it compares to inactive controls under highly controlled conditions) of SMT for the management of neck pain and low back pain. Additionally, a perspective on the current recommendations on SMT for spine pain and the needs for future research will be provided. In summary, SMT may be as effective as other recommended therapies for the management of non-specific and chronic primary spine pain, including standard medical care or physical therapy. Currently, SMT is recommended in combination with exercise for neck pain as part of a multimodal approach. It may also be recommended as a frontline intervention for low back pain. Despite some remaining discrepancies, current clinical practice guidelines almost universally recommend the use of SMT for spine pain. Due to the low quality of evidence, the efficacy of SMT compared with a placebo or no treatment remains uncertain. Therefore, future research is needed to clarify the specific effects of SMT to further validate this intervention. In addition, factors that predict these effects remain to be determined to target patients who are more likely to obtain positive outcomes from SMT.
Keywords: low back pain, neck pain, spinal manipulative therapy, manual therapy, placebo
Background
Pain affecting the spine not only has a significant impact on the individual's health and functional ability but also carries considerable costs to the economy and society at large, mostly derived from treatment expenses and work absenteeism (1, 2). Back and neck pain combined are the number one cause of years lived with disability and the fourth leading cause of years lost to disability globally (2, 3). At any time, over 11% of the world population suffers from pain in the spine (4, 5). The prevalence has been increasing over the past decade (2), particularly among working-age females in high-income countries (5, 6). Chronic cases where pain lasts for more than 3 months significantly contribute to the increasing burden of spine pain (1, 2). Likewise, pain affecting the spine affects more than 50% of patients with chronic pain (1, 7), a condition whose estimated direct and indirect costs are hundreds of billions of dollars (8). The frequent use of inappropriate and invasive clinical interventions has been suggested as one of the main reasons for this increasing burden (1, 8, 9).
Throughout the past decade, recommendations for the evaluation and treatment of back pain have shifted toward less invasive, non-pharmacologic approaches. This is partly the consequence of the opioid use epidemic in North America, largely driven by high rates and doses of opioid prescriptions for non-cancer pain (10–12). The Lancet series on low back pain (LBP) highlighted an overreliance on secondary care, imaging, opioids, spinal injections, and surgery (9, 13). Instead, currently available data provide stronger support for the use of conservative interventions and self-management strategies (9, 13–15). This is reflected in the recent publication of systematic reviews and clinical practice guidelines exclusively devoted to summarizing the evidence and recommendations for non-invasive treatments for neck pain (NP) and LBP (16–18). Among these interventions, manual therapy is frequently recommended as one of many front-line options for spine pain (13–19).
Chiropractic is a health care profession concerned with the management of neuromusculoskeletal conditions and, more specifically, disorders affecting the spine (20). Arguably, chiropractors' area of expertise lies within the field of spine care and in the application of manual therapy (21, 22). Most chiropractic patients seek care for spine-related conditions (23–25). Likewise, people with back pain frequently visit chiropractors in high-income countries (23, 26, 27). Chiropractors strongly rely on the use of manual therapy, particularly spinal manipulation (SM), which is the main form of care they provide (24, 26). In the United States, where data are available, chiropractors perform a large proportion of all SM treatments (28, 29). Chiropractic SM is sometimes referred to as a chiropractic or spinal adjustment in the literature (30). Typically, a spinal adjustment consists of the application of a high-velocity, low-amplitude controlled thrust force to a spinal segment. For the purpose of this review, all interventions relying on the application of such thrust forces to the spine will be considered under the common terms SM and SMT (spinal manipulative therapy). The clinical indication of chiropractic SM has been the subject of controversy (31). However, SM provided by chiropractors for spine pain was recently demonstrated to be cost-effective and rarely inappropriate (32, 33). Furthermore, accumulating evidence on the effectiveness of SMT for the treatment of acute and chronic back and neck pain has rendered it an acceptable management option (8, 27).
Recent research on SMT suggests that chiropractic care may be evolving from the field of complementary and alternative medicine toward becoming a mainstream option for spine pain (22, 34). However, there is a need to summarize the most up-to-date research in the field for a better understanding of this evolution. Here, we aimed to review the most recent randomized clinical trials on the effectiveness and efficacy of SM and SMT for the management of NP and LBP, mostly published in the past decade. In addition, recommendations from state-of-the-art clinical practice guidelines will be presented, as well as a perspective on challenges and future directions for research on chiropractic SMT and spine pain. While the narrative review will be informed not exclusively by studies where chiropractors apply SM, this is done to inform chiropractic clinical practice with the best current available evidence.
Methods
For the purpose of this review, the literature search was limited to SMT and manual therapy, when it comprised SM. Studies were included if they concerned the effectiveness and efficacy of SM, with no selection criteria for the professionals performing the intervention. Among these studies, only those published in English language between January 1st, 2009 and October 1st, 2019 were considered during the original selection. Relevant studies published after 2019 were added to the original selection during the publication process.
The following Databases were searched: Pubmed or Medline, Cochrane, CINAHL and the Index to Chiropractic Literature (ICL). The key search terms used for efficacy and effectiveness studies were: “spinal manipulation,” “spinal manipulative therapy,” “manual therapy,” “chiropractic” AND “efficacy,” or “effectiveness.” The results were filtered, and articles were selected with the key terms “lumbar” or “low back.” Since most studies concerned the lumbar spine, the terms “cervical,” “neck,” and “thoracic” were added to search literature on neck pain.
To narrow the search in line with the research question, clinical studies on the shoulder, upper extremity, chest pain, headache, dizziness, fibromyalgia, dysmenorrhea, or visceral conditions were excluded. Studies on pediatric populations were also excluded. The selection only included randomized controlled trials, systematic reviews, and clinical practice guidelines. Relevant articles were screened using the title and abstract. Two reviewers performed the search independently using these same criteria. After duplicates were eliminated, disagreements about inclusion were resolved through discussion and consensus.
A distinction needs to be made between effectiveness and efficacy, as these concepts refer to different levels of clinical evidence for an intervention (35). Effectiveness studies assess the outcomes of a treatment usually under circumstances that more closely resemble clinical practice. To do so, the intervention is commonly compared to another active treatment, such as standard care provided for the condition investigated (35). In contrast, efficacy studies are usually conceived as randomized clinical trials that are run under ideal and highly controlled experimental conditions. The treatment to be explored is preferably compared to an inactive comparator with known inertness, such as a sham or placebo (35). The most up-to-date evidence regarding the effectiveness of SMT for spine pain will be reviewed first, followed by a presentation of studies discussing its efficacy below.
Effectiveness of Spinal Manipulative Therapy for Neck Pain
Nonspecific NP is defined as pain between the skull and the first thoracic vertebra in the absence of a specific pathology or neurological sign (36, 37). Most cases of NP have been described as being of mechanical origin (38), which categorizes them as non-specific (36). In at least 10% of patients, non-specific symptoms persist beyond 3 months and can become chronic (38). In these cases, the condition is now defined as chronic primary (neck) pain (39, 40). The effectiveness of SMT has been examined in several studies on chronic primary NP as well as on acute and subacute non-specific NP. Most studies aimed to compare the effectiveness of a treatment based on SM to another active treatment, while fewer data are available concerning the efficacy of SMT compared to placebo (37, 41, 42). The most frequent active comparators used against SMT were other interventions commonly used for the management of NP, such as exercise or physical therapy modalities (43–50). Additional studies compared the application of SM to that of mobilization techniques or examined the effect of different SM application sites (cervical vs. thoracic) (51–58). However, these trials often measured short-term effects after short periods of care, which may not be as informative to clinical practice. All studies assessed pain intensity, the main outcome of interest for the present review, as measured with a numerical rating scale (NRS) or a visual analog scale (VAS). The second outcome measure of interest is the level of disability caused by NP, more commonly measured by the neck disability index (NDI) or the Northwick Park Neck Pain Questionnaire (NPQ). Outcomes may be assessed at variable follow-up times according to the study design. For both NP and LBP, a follow-up period of 1 month or less is generally considered short-term, intermediate-term is ~6 months and long-term follow-up after 1 year (59, 60). Figure 1 provides an illustration of the main results from the studies that are discussed below.
