Introduction

Manual therapy has not only come of age in the era of evidenced-based medicine for the treatment of musculoskeletal disorders, but also shows intriguing promise of benefit for systemic disorders. Albeit still early in the development of an evidence base compared to other medical and therapeutic practices, progress in manual therapy research is substantial and manual therapy warrants consideration as an appropriate treatment modality in many types of disorders and pain conditions. The 2008 symposium ‘Delineating the Evidence Base for Somato-visceral Interactions and Autonomic Mechanisms of Manual Therapy’ (Osteopathic Research Center 2008), which was the impetus for this book, was a benchmark event in that it came about in part with NIH-NCCAM grant support and brought together all of the manual therapy professions (see Chapters 12–15) as well as basic scientists whose research pertained to neuromusculoskeletal mechanisms of action (see Chapters 2–10). Manual therapy is a significant portion of the services provided by osteopathic physicians and physical therapists, and is the primary modality of service for chiropractic and therapeutic massage professionals. As discussed in Chapter 12, musculoskeletal pain is the most common reason for a person to seek primary medical care in the US (United States Bone and Joint Decade [USBJD] 2009), and around the world musculoskeletal disorders are the leading cause of disability, accounting for 25% of the total cost of illness (International Bone and Joint Decade 2006).

The intention of the 2008 symposium was to examine the evidence base for the concept of somatovisceral interactions and to examine the role not only of spinal cord but also of cortical and subcortical influences on these interactions, and to examine the possible role of manual therapy on somatovisceral and visceral interactions. A fundamental belief in the practice of manual therapy is that through somatovisceral interactions the treatment of somatic structures can influence visceral function. However, it is becoming more evident not only that spinal pathways are involved in these interactions, but that supraspinal (cortical and subcortical) structures have a strong influence on the interactions between somatic and visceral domains. Basic science evidence related to the nature of somatovisceral/viscerosomatic interactions and higher-center influences is presented in detail in Chapters 2–5, 7, and 10, and discussed in Chapter 16.

Each of the clinical research chapters (Chapters 12–15) has a section on the nature of the profession, whether osteopathic medicine/osteopathy, chiropractic, physical therapy, or therapeutic massage, which is intended to give the reader unfamiliar with a particular profession an overview that places the reported research in some perspective. For the purposes of this book, the umbrella term manual therapy encompasses the services delivered by providers in the professions listed above and represented in this text. Although there are differences in the scope of practice of the manual therapy professions in the US and worldwide, the research pertaining to the effects brought about by manual therapy providers is comparable, as many of the outcome measures and the hypothesized mechanisms of action are the same.

This chapter will review and summarize the evidence base for manual therapy and highlight the most promising areas for further research.

Manual therapy in musculoskeletal disorders – axial skeleton pain

Evidence for the benefit of manual therapy for musculoskeletal pain and its applications in the treatment of musculoskeletal disorders has reached the point where there is little doubt about its efficacy for several common musculoskeletal disorders. As discussed in Chapters 12 and 13, there has been a practice guideline statement from a US federal agency (Bigos et al. 1994) and a number of meta-analyses and systematic reviews (Assendelft et al. 2004, Bronfort et al. 2008, Cherkin et al. 2003, Licciardone et al. 2005) showing the benefit of manual therapy for some types of low back pain. Other research and reviews conclude there is benefit of manual therapy for neck pain from the chiropractic literature (Hurwitz et al. 2002, 2008), the osteopathic literature (McReynolds & Sheridan 2005), and the therapeutic massage literature (Sherman et al. 2009). However, with neck pain and other musculoskeletal conditions, more clinical trials are needed to reach the level of the evidence base for some types of low back pain.

Physical therapists have historically used manual therapy to treat musculoskeletal pain along with a number of other modalities. Research by physical therapists has tended to focus on specific modalities, rather than a general study of the efficacy of physical therapist application of manual therapy. Typical of this perspective is the research reported by George in Chapter 14, which describes the benefit of manual therapy in reducing musculoskeletal pain (George et al. 2006).

From the therapeutic massage perspective, Kahn, in Chapter 15, describes the preponderance of evidence as demonstrating that massage appears effective in reducing pain and restoring function in patients with subacute and chronic nonspecific low back pain, especially when combined with exercises and education (Cherkin et al. 2001, 2009, Furlan et al. 2009, Hernandez-Reif et al. 2001, Preyde et al. 2000). Cherkin et al.’s (2009) study on massage for back pain was a randomized controlled trial (RCT) which randomized 402 subjects with chronic low back pain to one of three arms: (1) usual care; (2) relaxation massage, which was a full-body protocol of entirely Swedish massage techniques in which the therapist was told to hold in mind the intention of encouraging a generalized relaxation response; and (3) focused structural massage, which was a protocol consisting largely of myofascial and neuromuscular techniques in which the therapist was told to identify the musculoskeletal contributors to each patient’s back pain and treat those. Both forms of massage were superior to usual care for low back pain, producing short-term reductions in symptoms and longer-term improvements in function. This study is representative of the progress made in clinical research design, which is now typical in manual therapy research.

It is beyond the scope of this chapter to exhaustively review these and other published research reports supportive of the benefit of manual therapy in musculoskeletal pain and musculoskeletal disorders. However, the summary and conclusions offered in this chapter are based on an integrated review of research from all the manual therapy professions. Two publications have provided an integrated consideration of research from the manual therapy professions (Lederman 2004, Seffinger & Hruby 2007) and also suggest that there is substantial support for the application of manual therapy in the treatment of musculoskeletal pain and musculoskeletal disorders. Since the publication of those books, more research has been published, some of which is included in this book. Based on the review of the evidence from the perspective of the authors of this chapter, as stated above, the conclusion is that there is substantial evidence for the benefit of manual therapy. Furthermore, from the perspective of the individual manual therapy professions this conclusion is justified; however, the argument is even stronger when the evidence from all the manual therapy professions is considered.

Manual therapy in musculoskeletal disorders – the rest of the body and mind

A number of clinical trials reported in the clinical chapters of this book reported benefit of manual therapy for appendicular (upper and lower extremities) musculoskeletal and perispinal conditions. In Chapter 12, research was reported for the benefit of manual therapy for restricted and painful shoulder function in the elderly (Knebl et al. 2002), reduction of carpal tunnel syndrome pain, and improved wrist range of motion (Sucher 1993, Sucher & Hinrichs 1998, Sucher et al. 2005), and relief of pain in patients with fibromyalgia syndrome (Gamber et al. 2002).

Also from the osteopathic literature, Eisenhart et al. (2003) reported statistically significant reductions in pain and ankle swelling from the application of manual therapy. Osteopathic manipulation has shown benefits in the treatment of Achilles tendonitis (Howell et al. 2006) and plantar fasciitis (Wynne et al. 2006). The therapeutic massage literature reports benefit for patients with osteoarthritis of the knee (Perlman et al. 2006), as does the physical therapy literature (van den Dolder & Roberts 2006).

Albeit not an exhaustive review, the studies cited above constitute a significant body of research on the application of manual therapy for pain in appendicular skeletal structures. Manual therapy is applied to the whole body, and the tendency in reviews is to cite only those studies pertaining to axial skeleton (spinal) structures. Indeed, when the research demonstrating the benefit of manual therapy for musculoskeletal extremity disorders is added to that for axial skeleton disorders, the evidence base for the benefit on manual therapy is both broadened and strengthened.

Pregnant women also experience musculoskeletal disorders and pain. As discussed in Chapter 12, osteopathic manipulative treatment (OMT) has been shown to reduce back pain and disability during the third trimester of pregnancy (Guthrie & Martin 1982, Licciardone et al. 2010) as well as improve vagal control of heart rate after just one OMT visit (Hensel 2009). One investigation (King et al. 2003) found that pregnant women who received OMT had significantly fewer preterm deliveries and instances of meconium-stained amniotic fluid, and suggested large cost savings if the morbidity and mortality from these disorders could be reduced. The nature of these results is also suggestive of viscerosomatic interaction effects, in addition to any postural improvements alleviating pain.

As Kahn reports in Chapter 15, the application of therapeutic massage has been shown to result in reductions in state anxiety, blood pressure, and heart rate, but not in cortisol levels, and that multiple massage treatments produced reductions in pain and depression comparable to those following psychotherapy (Moyer et al. 2004). Kahn also describes the research of Hodge et al. (2002) in which therapeutic massage was applied in the workplace, and states, ‘Findings indicate that compared with those in the control group, the massage group had significant improvement in cognition scores (p < 0.001), as assessed by the Symbol Digit Modalities Test, a 90-second timed instrument providing indices of normal capacities in adults as well as improvement resulting from specific therapeutic interventions. The massage subjects also showed lower anxiety (state p < 0.009, trait p < 0.04), improved emotional control (p < 0.05), and a reduction in sleep disturbance for massage subjects on 12-hour shifts (p < 0.02).’ These results show the effects of manual therapy on cortical functions and add to the discussion by Goehler in Chapter 10.

Manual therapy effects on physiologic function and systemic disorders

Those conditions that have been systematically reviewed – asthma, vertigo, dysmenorrhea/PMS (premenstrual syndrome), infantile colic, and nocturnal enuresis – are summarized by Hawk in Chapter 13, and she quotes from her 2007 review (Hawk et al. 2007, p. 506):

We suggest that the strongest evidence for the impact of manual therapy on physiologic function and systemic disorders may be in the conditions of pneumonia, asthma, and otitis media. Although Hawk mentions them in her 2007 review article quoted above, she did not specifically review the studies on manual therapy applied to the treatment of hospitalized elderly patients with pneumonia and children with otitis media. These studies, including research in press and available only from abstracts and posters, are reviewed by King in Chapter 12 and constitute some of the strongest evidence for the impact of manual therapy on systemic disorders. As detailed in Chapter 12 the studies on manual therapy for pneumonia in the hospitalized elderly by Noll et al. (Noll et al. 1999, 2000, Noll 2009) constitute a promising line of research, with the possibility to affect standards of care for these patients if subsequently substantiated in a larger clinical trial. For the treatment of otitis media in children, the studies by Mills et al. (2003) and Degenhardt and Kuchera (2006) show strong treatment effects, and have led to a subsequent clinical trial currently in analysis.

When the pneumonia studies are taken together with the asthma studies (Chapter 13), there is a broadening of the concept of manual therapy for pulmonary function and disorders. As suggested by King in Chapter 12, immune system function mediated by improved lymphatic flow due to manual therapy may account for much of the benefit seen in asthma and pneumonia patients. Specifically, we refer to the work of Knott et al. (2005) and Hodge et al. (2007) showing increased lymphatic flow in dogs during various manual therapy pump techniques. Several other studies confirm the finding of increased immune system cell counts as a consequence of lymphatic and visceral pump techniques of manual therapy (Measel 1982, Mesina et al. 1998, Jackson et al. 1998).

Another area of research common to both the osteopathic and therapeutic massage research is that as applied to pediatrics. Besides the aforementioned osteopathic research showing the benefit of OMT for pediatric otitis media, OMT has also been shown to reduce the symptoms of infantile colic (Hayden & Mullinger 2006) and sleep apnea (Vandenplas et al. 2008). Therapeutic massage research has shown the benefit of massage for premature infants in that neonates receiving massage gained weight faster (Field 2001), were able to leave hospital sooner (Field 1995), and while still in hospital were calmer and showed fewer stress behaviors (Hernandez-Reif et al. 2007).

This section would not be complete without mention of the osteopathic literature, described in more detail in Chapter 12. OMT significantly reduced the hospital stay for patients with postoperative ileus (Crow & Gorodinsky 2009) and pancreatitis (Radjieski et al. 1998). OMT also reduced the amount of analgesia in patients who received hysterectomies (Goldstein et al. 2005), improved pulmonary funtion in hospitalized patients (Sleszynski & Kelso 1993), and improved cardiac function and oxygen saturation in patients who had just undergone coronary artery bypass surgery (Yurvati et al. 2005).

Although there have been relatively few clinical trials on the impact of manual therapy on systemic disorders and physiological functions, the results thus far are intriguing and hold the prospect of great benefit, meriting top priority for further clinical investigation. There are enough manual therapy professionals to provide a meaningful service for these and related systemic disorders. In current times, when healthcare reform is being considered in the US and elsewhere, the cost savings of manual therapy applications, both in preventive healthcare and in the reduction of hospital stays, merits serious consideration at all levels of clinical research.

The authors of this chapter contend that the manual therapy research described above more than meets the requirements of evidence-based medicine for acceptance as a valid mode of treatment for musculoskeletal disorders, and is an impressive start in the process of establishing an evidence base. However, the fact remains that more research needs to be done to provide enough evidence for systematic review statements that have the potential to affect standards of practice in the treatment of musculoskeletal disorders. Research related to the question of which specific manual therapy techniques are more effective than others for certain musculoskeletal conditions is also needed. It is recognized that different manual therapy techniques have not always been effective for certain individual patients and conditions.

Interwoven with research on the effects of manual therapy on systemic disorders and physiological functions is the question of mechanism of action for the effects. This topic is considered next.