INTRODUCTION

After most surgical and nonoperative primary and secondary treatment approaches have been exhausted, the majority of patients with occupational musculoskeletal disorders have returned to work and decreased their health utilization. Depending on the US state or federal workers’ compensation venue and musculoskeletal area, an average of about 10% of patients persist with workers’ compensation disability 3–4 months postinjury. The range is about 5–25%, with a smaller (but growing) group of patients persisting in ‘perpetual limited duty’ (or partial disability) in conjunction with the recent advocacy for ‘keeping patients on the job.’ In time, unless such patients are unable to return to full duty or significantly modified jobs, they too go on to persistent work adjustment problems with employers and increasing disability behaviors.

Certain musculoskeletal disorders have a predilection for becoming chronic disabling problems. Spinal disorders, particularly those affecting the low back, usually beginning as ‘sprains and strains,’ are more highly represented among chronic pain/disability work-related injuries than other musculoskeletal areas. Upper extremity non-neurocompressive complaints, particularly those termed repetitive motion or cumulative trauma disorders (CTD) also have a higher rate of developing chronicity, and CTD claims are known to be 1.8 times more expensive than non-CTD claims.^1–7 By contrast, lower extremity injuries, particularly if they involve fractures, tend to resolve more completely within a usual tissue healing period. In many ways, the more subjective the diagnosis and mechanism of injury, the greater the likelihood of symptom persistence.

Chronic spinal disorder (CSD) pain is not merely a function of incomplete healing after injury. Traditional medical efforts to treat and rehabilitate chronic back pain have often been met with poor outcomes. Past failed efforts to identify the source of, or treat, CSDs have resulted in the identification of ‘psychogenic’ or ‘functional’ pain, terms attributed to pain for which no physical substrate could be found and, therefore, for which psychological or ‘nonorganic’ causes were suspected. Back pain has been found to be subject to diverse influences including psychological difficulties (e.g. anxiety, substance use, depression), and social losses (e.g. inability to work, family role changes, financial stresses). Turk and Rudy⁸ set forth the biopsychosocial model of pain asserting that pain is engendered not only by physical insult, but also by cognitive, affective, psychosocial, and behavioral influences. Based on this biopsychosocial theory, CSD treatment considerations now go beyond the physical source of the pain to consider psychological and socioeconomic variables as well.

Much controversy exists regarding the development of chronic pain/disability syndromes after work-related musculoskeletal injuries. A variety of psychosocial host factors, secondary gain and socioeconomic predictors have been variably reported in the literature. Clinicians tend to focus on the nonphysiological aspects of pain persistence, regardless of the diagnosis, because of the reasonable assumption that bones, joints, and soft tissues have healed completely, even if imperfectly, in a finite period of time. While there may be persistent bony malalignment, joint degenerative arthritis or soft tissue scar, these changes are deemed ‘set in stone.’ They may result in some degree of permanent impairment. However, while the majority of injured workers (and a perceived greater percentage of patients without compensation) seem to recover in a timely fashion, a disturbingly large and costly group of chronic disability patients remain disabled and refractory to treatment over a substantial period of time. These patients tend to demand a significant preponderance of indemnity and medical costs, and if followed in most federal social systems for 15–20 years, represent the largest number of patients in every industrialized country who become permanently disabled for the longest periods of time. This is because the average age of work-related musculoskeletal injury developing permanent disability is in the mid-30s, much earlier than any other diagnostic entity producing such disability (with the possible exception of the much less common psychiatric disorders). For these chronic pain/disability patients, repeated passive therapy, manipulation, or surgical intervention has commonly been tried, but has failed to relieve symptoms and overcome disability. These patients tend to produce the most significant cost to society in terms of medical care, disability payments, and loss of productivity. As such, they provoke a great deal of concern and interest. It is this difficult group of patients, failures of ‘conservative care’ and/or surgery, for whom spinal functional restoration is intended.

Economic globalization may create dislocations of local economies. In industrialized countries such as the US, these dislocations cause major shifts in demand for workers in different labor-intensive industries. There are pressures on workers to develop skills to shift jobs within the changing job markets. Industry is incentivized to reject those workers unable to make the transition. There are similar incentives to minimize the appearance of unemployment and job dislocations by ‘disappearing’ less flexible employees from the national economy. When chronic disabling musculoskeletal disorders lead to long-term re-employment problems, employers may find it more convenient to convert them to ‘throwaway workers.’ This creates pressure to compensate such patients with public, rather than private financing. Since the 1960s, Social Security Disability Insurance (SSDI), more recently linked to medical benefits through Medicare, has been provided to such individuals under certain circumstances. There has been a recent exponential growth in acceptance of younger and potentially more able-bodied workers onto this national insurance scheme, which was initially intended for retirees. Although musculoskeletal problems have decreased as the reason for acceptance onto SSDI rolls, they remain above 35% of all accepted claims. The combination of musculoskeletal and mental health ‘stress claims,’ which are often intertwined, have become the majority of acceptances onto SSDI. Because of the young age (30–45 years) at which many of these workers are accepted for long-term payments, Social Security actuaries have referred to the problem as one of ‘early, early retirement.’ Current costs are US$100 billion/year for SSDI, up 150% since 1980. There are now nearly 9 million ‘disabled’ pre-retirement Americans on Social Security, more than double the number in 1980.⁹ There is huge variance from state to state, with twice as many claims accepted in the disability determination process, and three times as many after the administrative hearing process, in the high-acceptance states (New Hampshire, Maine) compared to low-acceptance states (District of Columbia, Texas). The younger the patient accepted, the more likely there is a musculoskeletal basis, and low back pain is the single largest cause of musculoskeletal disability. With disability payments currently representing 5% of the entire US budget, such payments are becoming an increasing drain on the Social Security funds that were initially intended solely for retirees. Failure of tertiary rehabilitation for chronic occupational spinal disorders leads inevitably to patients departing the employment statistics and transitioning to insurance schemes such as SSDI in ever-increasing numbers. Thus, tertiary rehabilitation becomes the leading prevention strategy against permanent loss of productivity and high social cost in US spinal disorder medical care.

Because of the multifactorial and subjective nature of chronic pain, traditional therapy has been less than fully effective in treating and rehabilitating CSD patients. As a result, medical approaches have evolved to accommodate this costly and complex phenomenon. There are several risk factors that can be used to guide the treatment of spinal disorders and pain based on the levels of treatment described below. The severity of the dysfunction must be considered. The severity of a musculoskeletal dysfunction is related more to the patient’s chronicity and level of disability than to the presumed causative event. While diagnoses (e.g. degenerative disc disease, facet arthropathy, disc disruption, segmental instability) may be important in identifying surgically treatable pathology, their relevance fades in chronic pain conditions in which patients have generally failed to respond to invasive procedures, or have been deemed unsuitable for surgery. In addition to the psychological factors, inactivity and disuse may play a major role. They may lead to the deconditioning syndrome, in which the injured spinal region becomes a ‘weak link’ connecting the body’s functional units. Deficits of motion, strength, and endurance interfere with physical performance of otherwise unaffected joints and muscles.^10–14 While the need for spine surgery is rarely so imminent that a trial of nonoperative therapy is not indicated, there is often a limited understanding of the levels and purposes of such care as a function of the severity of the problem.

No one has yet managed to identify the unique structural ‘pain generator’ in the majority of CSD patients. Description of such a site has eluded basic scientists, surgeons, internists, and psychologists, and probably will continue to do so. The obvious reason for this is that pain is a subjective central experience of multifactorial origin. With the source of the pain deeply submerged and inaccessible to visual inspection (similar to headache and chronic abdominal pain) the spine is subject to diverse influences such as psychological difficulty, social losses, and financial uncertainties. These ‘secondary phenomena’ tend to be ignored by the health provider who has no mechanism available to deal with these problems. As a consequence, a critical part of our understanding of spinal disability is lost. Since interdisciplinary experience is not usually part of most physician training, lack of conceptualization and resolution in the area of chronic spinal disability is to be anticipated.