The total number of publications on the effects of osteopathy included, although small compared to the number of publications usually included in a bibliometric analysis for CAM in general [16, 17], is comparable to other bibliometric analysis for a particular CAM approach such as yoga (n = 486) [19]. This first bibliometric analysis of osteopathic research highlights a broad range of study designs, osteopathic approaches and outcomes. As shown in Fig. 1, empirical osteopathy-related trial publications doubled every 5 years in the first twenty-five years. This is more rapid than the overall scientific literature, where publications have been shown to double every 23 years [23]. This suggests a substantial increase overtime in documenting the efficacy of common interventions, and reflecting the rise of this profession around the world. Similar trends of accelerated development of scientific production followed by stabilization of rates of output are observed in the scientific productions for other complementary and integrative fields of medical practice [17, 18, 21]. Possible explanations for the increase in osteopathic scientific publication could be the growing number of osteopaths pursuing graduate studies in research, the need for a more evidence-based practice, as well as the development of initiatives to better structure, support, and stimulate osteopathic research capacity and international collaborations [24,25,26,27]. This particularly pertains to countries such as United States, United Kingdom and Australia, where regulation and university-based osteopathic education are well established [2]. For the same reasons, funding to conduct osteopathy-related research might be easier to obtain in those jurisdictions, thus leading to greater numbers of publications and facilitating international collaborations for those scholars. It is worth noting that more than half of the studies considered in this study originated from the United States, where osteopathy is considered to be a branch of biomedicine; whereas it is considered a complementary approach in all other jurisdictions [2].
According to our bibliometric analysis, research designs are polarized between low and high levels of evidence in the classical biomedical pyramid of evidence classification [28, 29]. Indeed, our analysis shows in Table 3 that other than case reports, the randomized control trial (many being characterized as pilot studies by authors) is the most common research design. The proportion of RCTs in osteopathic research is comparable to that reported in bibliometric analyses of other complementary and alternative medical practices [30]. Our research design observations are consistent with the conclusions of several systematic reviews of efficacy of osteopathic interventions, that indicate needs for more robust and larger studies of osteopathic efficacy [31,32,33,34,35,36,37,38,39,40]. Similar recommendations have emerged indicating needs for further research into mechanisms of action behind osteopathic interventions [41,42,43,44]. Such understanding of physiological mechanisms would also help to establish objective and measurable outcomes [45] and in turn support design of rigorous clinical trials [46].
The focus on RCT study design and systematic review, particularly in a relatively new and developing field, may limit understanding of the effects of a given approach. Understanding of the mechanisms of action and the impact of non-specific effects of a holistic approach using RCTs is a challenge in complementary and alternative medicine research since treatment is often complex and personalized [47, 48]. Thus, considering the evolution of the osteopathy body of knowledge, it would be strategic to encourage and take into account other research designs, including case studies and case reports. These research designs are the preferred strategies to investigate “how” and “why” questions about an intervention. Non-RCT studies may contribute useful descriptive data that are sensitive to the contexts within which the experiences take place [49] and can lead to a better understanding of the potential effects of osteopathic approach in order to design robust RCTs. Knowledge syntheses on the effects of osteopathy could therefore be more inclusive of other research designs, possibly presented as narrative reviews, until publication volume has increased and larger scale research is available.
The bibliometric analysis offers an innovative insight into the alignment of research efforts with clinical practice. The body regions and systems most often studied in osteopathic research (Table 4), i.e. the spine and pelvis, the thoracic, abdominal and pelvic visceral areas and systems, the extremities and finally the head and face region, are consistent with the regions and systems most frequently addressed in the clinical practice of osteopaths regardless of the healthcare system or regulation of osteopathy [4, 7, 50]. In addition, most of the often-cited scientific publications address the effects of osteopathic manual treatment on low back pain; the condition (along with cervical pain) recognized as the most common reason for osteopathic consultations [3, 4, 6,7,8, 51]. The musculoskeletal techniques most frequently reported in the scientific literature – namely myofascial release, muscle energy, HVLA, soft tissue and articulatory or mobilization techniques – are aligned with what are observed to be the preferred or most used techniques in practice [6,7,8, 11, 12, 50, 51]. The same is noted regarding less common techniques in what is termed the visceral osteopathic field, insofar as the two most frequently used techniques (lymphatic, and organ mobilization techniques) correspond to the proportion of the osteopaths using it in clinical practice [8]. In the cranial field of osteopathy, suboccipital decompression technique, non-specific cranial techniques, balanced membranous tension and cranio-sacral techniques were investigated in 43.4% of included studies; this information can help to document the contribution of cranial techniques used from a quarter [8, 12, 50, 51] to half [6, 7] of osteopaths in clinical practice. The very low percentage of studies using exclusively cranial (3.9%) or exclusively visceral (1.3%) techniques highlights the irrelevance of trying to study compartmentalized techniques of osteopathy. In fact, nearly half of the studies (48.1%) used techniques of at least two and sometimes all of the classical fields of osteopathy (musculoskeletal, visceral and cranial), which reflects the essence of this multi-system approach, and the concept that the person is a dynamic functional unit in which all parts are interrelated [1].
Finally, as shown in Table 1, more than half of the publications were published in the three classic journals for osteopathy: Journal of American osteopathic medicine (JAOA), American Academy of osteopathy Journal (AAO) and the International Journal of osteopathic medicine (IJOM). These journals target a limited, discipline-focused readership, but were more likely to support the publication of study designs at the lower end of the evidence continuum. The transfer of knowledge between research and practice therefore remains highly disciplinary and focused on practitioners with interested in research. Besides, publications in this bibliometric study have been published in relatively low impact factor journals, which might impede the capacity of scholars to reach the overall healthcare community. Broader and better dissemination of research results through open access publications and various media can improve the reach to both patients and practitioners [46], for a greater impact in the healthcare field, including medical researchers, health care insurers, government agencies, and the media; the media is noted to exert considerable influence over public opinion and, potentially over policy [52, 53].
