Don’t Throw the ‘Bio’ out of the Bio-Psycho-Social Model: Editorial for Spine Rehabilitation in 2022 and Beyond

1. Introduction

Spinal injuries, disorders and disabilities are among the leading causes for work loss, suffering, and health care expenditures throughout the industrialized world [1,2,3,4,5,6]. The psycho-social and economic impact of general and specific spine disorders demands continued research into the most effective types of preventative and interventional treatment strategies. Specifically, low-back-pain (LBP)- and neck-pain-related disorders are the 1st and 4th leading causes of work loss and disability in the world [1,2,3,4,5,6]. Though billions are spent annually in experimental, epidemiology, and interventional strategies, precise treatment regimens aimed towards improving, resolving, and preventing these spinal disorders are highly varied and have limited and/or only short-term efficacy [1,2,3,4,5,6]. Thus, spinal disorders and related disabilities remain a high priority research avenue within the health sciences; in particular, there is an urgent need to increase the knowledge related to the manual rehabilitation disciplines [5,6].

Pain and disability with a spinal origin have several proposed psycho-social [1,2,3,4,5,6,7,8,9] and biomechanical contributing factors [10,11] which has given rise to the well-known ‘bio-psycho-social’ model of understanding injury mechanisms leading to the development of chronic pain and disabilities. Problematically, in recent decades, many authors have begun to minimize the ‘bio’ (tissue injury, damage, anatomical disorder, etc.) component of the problem, thus favoring the ‘psycho-social’ aspects such as catastrophizing, fear/anxiety and avoidance behavior components in the development of chronic pain in the patient [1,2,3,4,5,6,7,8,9], as some authors are quite adamant that the ‘tissue injury’ component plays a rather limited role [6]. It can be argued, though, that the lack of appreciation for the tissue component of spine pain/disorders is shortsighted, based on an incomplete review of recent systematic reviews, and based on limitations with early analytical methods, whereas today’s technology and more detailed investigations have identified a significant role for the tissue component as contributing to the presence and development of chronic spine pain and disability [12,13,14,15]. Furthermore, proponents of the stronger role that the ‘psycho-social’ part of the equation plays in spine conditions often fail to acknowledge that recent systematic literature reviews with meta-analysis have identified a clear controversy regarding the quality and true impact that fear-avoidance, pain-catastrophizing (PC), and ‘psycho-social’ model elements play in individuals with chronic musculoskeletal pain (CMP) disorders [7,8,9]; for example, the following has been stated: “Despite the very low quality of the available evidence, the general consistency of the findings highlights the potential role that PC may play in delaying recovery from CMP. Research that uses higher quality study designs and procedures would allow for more definitive conclusions regarding the impact of PC on pain and function.” [7]. The current authors of this Editorial offer this perspective for context and not to dismiss the role that the psycho-social component plays in initiating and developing chronic spine related disorders.

It is often understood but understated that the ‘bio’ component in the ‘bio-psycho-social’ model also stands for biomechanics (not just biology) either segmentally or globally of the whole spine–body system [10,11]. While the mechanical causes of musculo-skeletal pain are not completely understood, they are thought to be linked to the interconnected functions of anatomical components (soft and hard tissues) of the spine where injury and pain can be caused by any incident that alters joint mechanics (kinematics, kinetics, alignment), tissue integrity, and muscle function via alterations and increases in general loading and load sharing of the various tissues [10,11]. Of interest, several authors have attempted to completely dismiss or minimize the role that biomechanics (alignment and loading) plays in the onset and development of musculoskeletal disorders [16,17,18,19,20]. For example, in a systematic review, it was concluded that “Evidence from epidemiological studies does not support an association between sagittal spinal curves and health including spinal pain.”[16]. Complicating the matter, in each of the reviews that proposed a minimization of the role that biomechanics (alignment and loading) plays in chronic spine disorders [16,17,18,19,20], serious flaws in the study design and literature reviews were identified [19,20,21,22,23,24] highlighting the controversy and confusing the situation further.

Importantly, in the past two decades, the role that biomechanics of the sagittal plane alignment of the spine and three-dimensional posture has on human performance, health, pain, disability, and diseases has been a primary research focus among spine surgical and rehabilitation specialists across the scientific literature [25,26,27,28,29,30,31,32,33,34,35,36,37]. It has been quite extensively demonstrated that sagittal plane alignment and biomechanics of the lumbo-pelvic [25,26,27,28,29,30,31,32], thoracic hyper-kyphosis [33,34,35], and cervical [36,37] spines have clear impacts on human health and well-being, musculoskeletal disorders, and chronic pain disorders. Limits of normality for a variety of sagittal spine alignment parameters have been documented, providing chiropractors, physical therapists, surgeons, and other spine specialists with standardized goals to compare patients to in both pre- and post-treatment decision-making strategies [25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40]. Furthermore, conservative interventional methods have been developed and tested for their effects on improving altered sagittal plane alignment and preliminary and promising results have been found for a multi-modal program including lumbar extension traction (LET) [38], cervical extension traction (CET) [39], thoracic extension traction (TET) [40], bracing for thoracic hyper-kyphosis [41], and various specific exercise regimens for thoracic-kyphosis [41,42]. Problematically, some authors continue to ignore the evidence for these new types of sagittal plane curve-inducing (LET and CET) and curve-reducing (TET) traction methods and spinal bracing and their role in improving the sagittal plane alignment of the spine and improving chronic musculoskeletal disorders [4].

2. Purposes of Special Issue on Spine Rehabilitation

All too familiar are approaches to spine care involving functional rehabilitation programs including exercises for strength gains, range of motion increases, generalized stretching and strengthening procedures, massage, and soft tissue manipulation techniques, as well as physiotherapeutic modalities such as ultrasound and muscle stimulation, etc. An alternative to the traditional and popular functional approaches is a structural rehabilitation approach. Structural rehabilitation involves some aspects of functional rehabilitation methods but focuses on unique types of posture and spine correction methods for the primary purpose to realign and ‘over-correct’ the spine and altered postures [43].

Although spinal bracing and postural exercise techniques have shown preliminary evidence for providing structural spine and posture realignment [41,42], one evolved technique that has laid a substantial foundation towards the structural approach to spine care is the Chiropractic Biophysics^® technique group [43]. From the mid-1990s to the mid-2000s, the Harrison research team performed a series of spine modeling studies of the sagittal spinal curves (Figure 1) [43]. This has formed the foundational spinal model to which patient comparison can be made for initial assessment of alignment abnormality and follow-up assessment to monitor treatment effects. Further, elaborate assessment and corrective treatment methods are based on the fundamental assessment of posture in terms of translations and rotations of the separate body segments in relation to each other (Figure 2 and Figure 3) [43].

Beginning in approximately 2010, Moustafa and colleagues (teaming up with Harrison and later Oakley) spearheaded the fundamental missing randomized controlled trials (RCTs) seeking to understand the efficacy and clinical utility of CET and LET methods [38,39,44,45]. These RCTs demonstrated that patients with cervical, thoracic, and lumbo-pelvic sagittal plane abnormality-related symptoms receiving spine correction via CET and LET methods achieved greater long-term health outcomes (pain, disability, mobility, etc.) versus patients who only received conventional functional based treatments that do not consistently improve spinal alignment [38,39,44,45]. Though today there are reliable and predictable means to restore the natural curvatures of the spine and improve sagittal balance and generalized posture alignment [38,39,40,41,42], the evidence is still preliminary and there are many areas for further research including the need for randomized trials on TET methods, an understanding of which sub-groups of populations with spine disorders might benefit the most, what is the ideal dose–response of treatment frequency and durations versus outcomes for different patient populations, and many other areas. Furthermore, more information from better quality case–control designs and cohort populations are needed to identify what type of effects (if any) that specific spine displacements have on musculoskeletal function, neurophysiology, and performance; in other words, more than just pain and disability outcome measures must be looked at and understood for a comprehensive understanding of the impact that altered spine/posture alignment has on spine related disorders and in improving human health and well-being. Additionally, there is a lack of information on non-sagittal spine displacements, and how these spine and posture displacements impact human health and disease needs to be comprehensively investigated. Finally, the economic impact, health benefits, and generalized awareness of full spine displacements and the newer ‘structural rehabilitation’ spine treatment methods demand continued attention from clinicians and researchers alike; the topics outlined above are the purposes of this collection of studies.

3. Special Issue Main Accepted Articles

At the time of the writing of this Editorial, there were 15 unique manuscripts accepted for publication in the Special Issue: Spine Rehabilitation in 2022 and Beyond. These manuscripts include the following categories of articles: a cross-sectional survey comparing two distinct quality of life questionnaires in adults with scoliosis [46]; a retrospective consecutive cohort investigation examining the relationship of vertebral y-axis rotation of the lumbar spine in functional scoliosis with leg length inequality to sacral shelf lateral tilt angles [47]; a profession wide survey of the chiropractic profession regarding spine radiography utilization examining clinical opinions and experience [48]; a novel clinical manual method comparing manual palpation and motion vs. diagnostic imaging to determine pathological rotational instability movement of the upper cervical spine [49]; four case–control investigations seeking to identify any correlations between spine and posture displacements and patient pain, disability, neurophysiology, and sensory–motor control variables [50,51,52,53]; one case series looking at the relationship between non-surgical sagittal plane cervical spine correction and the improvement in upper cervical spine rotational instability [54]; five randomized trials examining the relationship between correction/reduction of cervical and thoracic posture deformities and spine displacements and improvements of a variety of clinical outcome measures including pain, disability, neurophysiology, range of motion, and sensory–motor control measures [55,56,57,58,59]; and, lastly, one systematic literature review that sought to understand the differences in low back pain and disability characteristics in adults with and without scoliotic spine deformities [60].

Importantly, each one of these 15 accepted manuscripts offers unique and succinct relevant data that provide further evidence that the ‘bio’ (biology and biomechanics) component of the ‘bio-psycho-social’ model of spine care is extremely important to understanding patient pain, disability, and dysfunction and to providing enhanced treatment procedures that improve the outcomes of patient care [46,47,48,49,50,51,52,53,54,55,56,57,58,59,60]. As such, this Special Issue on spine rehabilitation provides useful, cutting-edge, relevant information that should prove to be useful to improve patient care and outcomes in populations suffering from a wide variety of spine related disorders. We thank all the authors of each of these manuscripts for their work, dedication, and insights they provided to bring their team’s data together in an effective scientific manner. We are confident that each of the manuscripts contained in this collection will be well cited and used by future clinicians from many disciplines and researchers to treat patients around the globe and to improve upon the information presented [46,47,48,49,50,51,52,53,54,55,56,57,58,59,60].

4. Conclusions

Good quality data currently exist and continue to evolve to support the ‘bio’ element in the biopsychosocial model of chronic pain disorders. This Special Issue, dedicated to ‘spine rehabilitation in 2022’, features highlights of several research avenues taking place, such as the link between altered posture and physical performance, altered posture and pathological conditions, as well as the therapeutic improvement in spine alignment and posture correlating with positive patient outcomes. These lines of research are desperately needed and, unfortunately, continue to be underrecognized. We believe a tidal wave of ‘bio’ evidence is mounting, and a better of the understanding of the biomechanics in spine care will lead to more effective treatments. We hope for the biomechanical spine literature to continue to gain a wider acknowledgement and acceptance by the chronic spine pain community.