Introduction
Physicians dealing with the evaluation and treatment of patients with chronic painful and disabling conditions can expect to be called on from time to time to formally assess the disability of their patients. Recent estimates indicate that more than 40 to 50 million persons are currently living with potentially disabling conditions, and these numbers are likely to increase in the next few decades with our aging generation of baby boomers. Continued advancements in medical and surgical technologies enable increased survival after catastrophic injuries and illnesses and may help mitigate the disabling consequences of the same, as well as allow an increased prevalence of disability within our society. As the face of our disabled population changes, treating physicians can adapt their practice to better address the needs of patients associated with these changes by gaining greater familiarity with and understanding of the concepts and terminology of disablement and the practices of impairment rating and disability evaluation.
This chapter is intended to provide pain specialists with a practical vocabulary of the terminology and definitions unique to the emerging field of disability medicine, to provide a brief historical and conceptual overview of models of disablement and U.S. disability systems, to familiarize pain specialists with the processes and tools available for impairment rating and disability determination, and to examine the medical-legal pitfalls and ramifications of these clinical activities.
Working Terminology and Definitions
The following terms and definitions are frequently applied to the evaluation and reporting of disablement:
Aggravation : A circumstance or event that permanently worsens a preexisting or underlying and susceptible condition
Exacerbation : A circumstance or event that temporarily worsens a preexisting or underlying and susceptible condition
Apportionment: A determination of the percentage of impairment directly attributable to preexisting or resulting conditions and directly contributing to the total impairment rating derived
Causality : An association between a given cause (an event capable of producing an effect) and effect (a condition that can result from a specific cause) within a reasonable degree of medical probability. Causality requires determining that
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An event took place.
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The claimant experiencing the event has the condition (i.e., pathology, impairment).
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The event could cause the condition (biologic plausibility, etc.).
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Within medical probability the event did cause the condition.
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Impairment : A significant deviation, loss, or loss of use of any body structure or function in an individual with a health condition, disorder, or disease
Maximum medical improvement (MMI): The point at which a condition (impairment) has stabilized and is unlikely to change (improve or worsen) substantially in the next year with or without treatment. MMI is thought to occur when the following criteria have been satisfied:
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A sufficient healing period has transpired (usually based on an analysis that includes consideration of the natural course of disease for the specific pathology, which in some cases may be days, months, or rarely even years.
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The medical condition (impairment) has fully resolved or has reached a static and stable status (plateau), after which no further reasonable progress occurs or is expected to occur in the next 12 months toward resolution of the pathology.
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MMI does not preclude any deterioration of a condition that is expected to occur with the passage of time (i.e., beyond 12 months), nor does it preclude allowances for ongoing follow-up or maintenance medical care should such care be indicated based on current evidence-based practice generally accepted by the scientific community.
Working Terminology and Definitions
The following terms and definitions are frequently applied to the evaluation and reporting of disablement:
Aggravation : A circumstance or event that permanently worsens a preexisting or underlying and susceptible condition
Exacerbation : A circumstance or event that temporarily worsens a preexisting or underlying and susceptible condition
Apportionment: A determination of the percentage of impairment directly attributable to preexisting or resulting conditions and directly contributing to the total impairment rating derived
Causality : An association between a given cause (an event capable of producing an effect) and effect (a condition that can result from a specific cause) within a reasonable degree of medical probability. Causality requires determining that
- •
An event took place.
- •
The claimant experiencing the event has the condition (i.e., pathology, impairment).
- •
The event could cause the condition (biologic plausibility, etc.).
- •
Within medical probability the event did cause the condition.
- •
Impairment : A significant deviation, loss, or loss of use of any body structure or function in an individual with a health condition, disorder, or disease
Maximum medical improvement (MMI): The point at which a condition (impairment) has stabilized and is unlikely to change (improve or worsen) substantially in the next year with or without treatment. MMI is thought to occur when the following criteria have been satisfied:
- •
A sufficient healing period has transpired (usually based on an analysis that includes consideration of the natural course of disease for the specific pathology, which in some cases may be days, months, or rarely even years.
- •
The medical condition (impairment) has fully resolved or has reached a static and stable status (plateau), after which no further reasonable progress occurs or is expected to occur in the next 12 months toward resolution of the pathology.
- •
MMI does not preclude any deterioration of a condition that is expected to occur with the passage of time (i.e., beyond 12 months), nor does it preclude allowances for ongoing follow-up or maintenance medical care should such care be indicated based on current evidence-based practice generally accepted by the scientific community.
Models and Classification of Disablement
Models of Disability
The “medical model” of disability was the paradigm for understanding disablement throughout much of the 19th and 20th centuries, during which causation of disability was directly viewed in terms of the underlying pathology (impairment) arising through illness or disease. Management of disability was closely linked to diagnosis and treatment of the underlying pathology, long considered the purview of the physician examiner, who then became empowered to rate, as well as to diagnose and treat, the disabling condition (impairment). Anatomic and physiologic objectivity is the conceptual lynchpin of the medical model of disability. This model worked well for conditions in which the diagnosis was unambiguous and the pathology was well understood and in which treatment strategies and end points were often well established and also clearly understood. Today, the medical model still serves as the basis for Social Security disability determinations (see later).
The “social model” of disability grew out of the disability advocacy movement of the 1970s and 1980s and was founded on the notion that society imposes disability on individuals with impairments by failing to address their special needs in terms of priority awareness, environmental access, and infrastructural accommodation for major life activities. The resulting disability was viewed in terms of restrictions imposed on the impaired individual ranging from individual and institutional prejudicial thinking and discrimination, architectural and other physical barriers to access and transportation, educational segregation, and lack of accommodation in the workplace. An understanding of the social model has helped foster strategies to better neutralize social barriers to individuals with impairments, thereby enabling them and minimizing their disability.
The “biopsychosocial model” of disability is now widely accepted as the preferred conceptual model of disablement. It simultaneously recognizes the contributions of medical, social, personal, and psychological determinants of disability. The biologic component refers to the physical and mental aspects of an individual’s health condition, the psychological component recognizes personal and psychological factors that are affecting that individual’s functioning, and the social component recognizes contextual and environmental factors that may also have an impact on functioning in each particular case.
Classifications of Disablement
The most commonly used, contemporary, internationally accepted definitions, terminology, and classification of disablement have been created by the World Health Organization, the origins of which can be traced to the work of Bertillon’s Classification of Causes of Death (1893), which later was expanded into the International Statistical Classification of Diseases, Injuries and Causes of Death ( ICD ). In 1948 the World Health Organization took over this effort, which ultimately led to creation of the International Classification of Impairments, Disabilities and Handicaps ( ICIDH ) in 1980. This system applied a model of disablement with four ordinal domains linked in a linear relationship as follows ( Fig. 17.1 ):
Pathology —“a disease or trauma acting at a tissue anatomical or physiological level to potentially alter the structure and/or function of an organ.”
Impairment —“any loss or abnormality of psychological, physiological or anatomical structure or function and resulting from a pathology.” Impairment occurs at an organ system level.
Disability —“any restriction or lack (resulting from impairment) of ability to perform an activity in the manner or within the range considered normal for a human being.” Disability is commonly conceptualized in terms of limitations in activities within one’s personal sphere, including mobility (transfers and ambulation) and self-care (activities of daily living [ADLs]).
Handicap —“a disadvantage for an individual that limits or prevents fulfillment of a role that is normal (depending on age, sex, social and cultural factors) for that individual.”
There were several shortcomings of the ICIDH system. It was rooted in the medical model of disease, whose limitations are described above. The linearity of the system implies a unidirectional and causal relationship among its elements, which may not always be the case. It inadequately accounted for various modifiers (e.g., personal, environmental) that could influence the magnitude of disability ; for example, other work showed that environmental factors play a key role in determining outcomes of disability, which could be studied independently. Subsequent work by the Institute of Medicine (IOM) and the National Center for Medical Rehabilitation Research (NCMRR) expanded on the view that the resulting disability was the product of the individual with an impairment interacting with the environment in each specific case. Additional attention was given to the role of personal modifiers (e.g., lifestyle choices, belief systems, entitlement, and coping abilities) affecting the outcomes of disability for individual cases.
The International Classification of Functioning, Disabilities and Health: ICF is depicted in Figure 17.2 .
The ICF has replaced the ICIDH and portrays an interactive (as opposed to linear) association between an individual with a health condition, the functional consequences of the impairment, and contextual factors of a personal and environmental nature. The ICF classification system embraces the biopsychosocial model of disease described earlier by taking into account environmental and personal modifiers of functional outcomes in any given case.
The components of disablement according to the ICF classification system include the following:
Body functions and body structures : physiologic functions and body parts, respectively
Activity : execution of a task or action by an individual (typically within that person’s personal sphere)
Participation : involvement in a life situation (typically within a social sphere)
Impairments : problems in body function or structure such as a significant deviation or loss
Activity limitations : difficulties that an individual may have in executing activities
Participation restrictions : problems that an individual may experience in involvement in life situations
Within this conceptual framework the disabling consequences of impairment may be amplified or mitigated by factors unique to the individual with a health condition, by interaction with the environment, and by personal choice. To illustrate the importance of environmental factors, consider Vignette 1:
A farmer in rural Iowa suffers a unilateral medium-length transradial amputation of the forearm in a combine accident. He would probably have immediate access to level 1 trauma services on an emergency basis and receive timely and appropriate surgical and medical care to repair and heal the residual limb. He would benefit from rehabilitation and most likely from fitting with a body-powered upper limb prosthesis with an appropriate industrial-grade terminal hook device. With proper training and motivation, he could recapture the majority of his “baseline” functional activities—independent ADLs, household activity, community activity, and work (with some limitations). If need be, he might also be fitted with a myoelectric or cosmetic hand, or both, thereby maximizing his full functional potential. Alternatively, a similar clinical scenario in a “third world” country could have a significantly less favorable functional outcome. Consider a transradial amputation in a local Haitian resident following the devastating earthquake in 2009, where the availability of timely medical and surgical care was compromised by local destruction of the existing medical infrastructure and access to rehabilitative care and adaptive technology was scarce or nonexistent. In such a scenario the less fortunate individual might be left with one functioning upper limb and be destined to manage ADLs with one-handed techniques indefinitely.
To illustrate the importance of personal choice, consider Vignette 2:
A long-term smoker with advanced chronic obstructive disease has measurable pulmonary impairment as noted by a significant reduction in forced expiratory volume in 1 second (FEV 1 ) on pulmonary function testing. The probability of the symptoms worsening and a further decline in FEV 1 over time is directly linked to the amount and duration of continued smoking, and consequently, the impairment can be substantially mitigated or worsened simply by making a personal choice to adopt or reject permanent smoking cessation.
Despite its superiority as a classification system, shortcomings of the ICF can be noted. The distinctions between activities and participations are often blurred, and inadequate attention has thus far been given to measures of quality of life (QOL) (e.g., life satisfaction, burden of care) in the model itself.
Measuring Disability for Compensation Purposes
Social justice requires that individual group members contribute productively to the common good of the whole. Provisions must be made, however, to exempt this requirement and to support members who are incapable of such productivity by virtue of age, illness, or disability. A related expectation is that individuals who incur loss or disablement as a result of illness or injury are thereby entitled to some compensation for their loss.
Within our social system there exist a number of different disability systems (see later) designed to compensate individuals for such loss. They share a common conceptual and operational platform in which the initial estimate of physical or psychological loss (or both) can be translated into an estimate of functional and economic loss expressed in monetary terms.
By convention, the severity of physical and psychological loss is operationally defined and measured in terms of a medical impairment rating at an organ system level that is typically expressed as a percentage of regional loss of the affected body part or parts and that can be further extrapolated to the body as a whole. The severity of functional and hence economic loss associated with this impairment percentage is further estimated in terms of a disability rating expressed as a percentage of the economic worth of the “whole person.” The disability rating is operationally derived from the impairment percentage and is at once intended to reflect direct economic losses, noneconomic losses, and negative impact on QOL in terms of a monetary sum. The whole person value and the magnitude of awards vary according to the disability system in question, and disability payments may be awarded as a lump sum or on an annuity basis.
The IOM recently developed a generalized model to demonstrate the essential features common to all disability systems. Individuals seeking compensation and meeting the criteria for entitlement must demonstrate losses according to five domains of interest (see Fig. 17.3 ).
The first of these, medical impairment , traditionally carries the most weight for several reasons. It is largely anatomically and physiologically based and hence can readily be measured in objective terms. Objectivity enables codification of the disability and fosters standardization, reliability, and reproducibility of measurement according to some uniform scale. Impairment can be measured and expressed in terms of anatomic or functional losses.
The second domain of interest, functional limitations , can be expressed and measured in terms of basic ADLs or instrumental (advanced) activities of daily living (IADLs), or both. ADLs include such basic activities of self-care as feeding, toileting, grooming, bathing, hygiene, and dressing—activities that generally occupy our personal sphere. IADLs require greater cognitive and physical capacity and include such activities as meal preparation, driving, and managing finances, medications, and one’s daily routine.
The third domain, work disability , can be understood in terms of loss of earning capacity (an actuarial determination of negative impact on employability and earnings brought about by work restrictions because of the impairment and other considerations such as age, baseline employment and earnings history, availability of accommodation and alternative job opportunities, and other local factors). It can also be understood in terms of actual loss of earnings directly attributable to the impairment.
A fourth domain, nonwork disability , includes losses in terms of inability to visit friends and relatives and to engage in communal activities, hobbies, or other recreational pursuits because of barriers to access or performance attributable to the impairment.
A fifth domain, quality of life , includes losses attributable to diminished life satisfaction and self-esteem and increased burden of care in terms of treatment compliance and caregiver support.
The metrics whereby each of these constructs is defined and measured vary and remain incompletely understood. This is partly due to the persisting confusion in terminology, definitions, and criteria for impairment and disability across the various systems and the continuing emphasis on objective, medically determined impairment as the prime determinant of disablement.
Unfortunately, there is also lack of agreement on the metrics whereby the impairment ratings themselves are determined between and even within the various disability systems of interest. For example, U.S. workers’ compensation (WC) jurisdictions show considerable variability in terms of their acceptance or rejection of standard and uniform impairment rating guides, and those that mandate or recommend use of the same vary in the choice of reference; even in the case of the American Medical Association Guides to the Evaluation of Permanent Impairment (AMA Guides), the actual edition chosen for reference varies from state to state. The same is true for international use of the AMA Guides, where in many countries (e.g., Australia, the Netherlands, South Africa), the various editions are used for individuals in motor vehicle accidents and with other personal injury claims to determine the severity of injury (a threshold) before access to benefits for general damage (nonpecuniary, noneconomic losses) is granted.
The importance of the impairment rating to cash awards also varies within and between the various disability systems, as a closer examination of the U.S. WC system illustrates. Operationally, the WC system awards cash benefits according to three basic approaches: the first of these, the impairment approach , awards benefits in direct relation to the percentage-of-impairment rating; the second, the loss of earning capacity approach , requires that the injured worker have an impairment rating but then bases the actual amount of cash benefits on the estimate of associated loss of earning capacity; the third approach, the actual wage loss approach , requires the worker to have both an impairment and loss of earning capacity and then bases the amount of cash benefits on demonstration of the actual loss of workers’ earnings.
The mechanism by which WC cash benefits are awarded is further complicated by distinguishing between various types of injuries as scheduled versus unscheduled. Scheduled injuries are those typically affecting the upper or lower extremities and listed as percentage of the extremity; unscheduled injuries affect the spine, nervous system, or other organ systems and are awarded as percentage of the “whole person.”
Although the impairment rating is the common factor in determination of disability for cash benefits, it is not the sole factor. In practice, however, many jurisdictions implement procedural shortcuts whereby the impairment rating percentage becomes a direct surrogate for the disability rating according to a predetermined formula that multiplies the impairment percentage times a number of weeks’ wages (up to a cap) times a percentage (generally ⅔ to ¾) of the average weekly wage (up to a cap) to determine a lump sum payout. The adequacy of applying the impairment rating as an operational surrogate measure of disability continues to be a subject of debate.
Implications for pain sufferers can be noted as follows: the metrics for the medical impairment rating clearly favor and emphasize objective over subjective criteria. Accordingly, painful entities such as headache, fibromyalgia, and low back pain often occur in the absence of objective verifiable pathology or may occur in a setting in which objective clinical findings are most consistent with normal anatomic variation and the aging process and may be of little or no clinical significance to the individual’s actual complaints. Impairment ratings in such cases are ineffective, at best, since minimal or no rating percentage is currently allowed for any apparent (and often profound) negative impact that these conditions may be having on ADLs. The disablement and ensuing loss in such cases potentially become more evident if viewed in terms of QOL. Well-respected psychometric instruments are now available to measure QOL; notable examples include the Quality of Well Being (QWB) scale, the WHOQOL-100, and the Quality of Life Index (QLI). Unfortunately, such metrics are not familiar tools to the typical rating physician and are not routinely taken into account by the rating systems per se; consequently, losses in terms of QOL remain largely unaccounted for by the rating practice summarized above.
U.S. Disability Systems Compared ( Table 17.1 )
Workers’ Compensation
WC law is determined by jurisdictional statutes, which vary from state to state and may differ in terms of the definition of an employee-employer relationship and the exemptions that may apply. WC is a no-fault system whereby the injured employee forgoes the right to sue the employer for damages in most cases in exchange for coverage when eligibility requirements are met. A causality determination must be made that the injury or illness arose out of and in the course of employment and occurred while the employee was at work and actively participating in work activity (job-related social and recreational activities generally do not qualify). Coverage is established in accordance with jurisdictional statutes, and to qualify for wage loss benefits, the injured employee’s condition must persist beyond a statutory waiting period that typically extends from 0 to 7 days; the injury or illness must also be reported to the employer within 30 days of onset and a claim filed within 1 year for disability and 2 years for death.
| Eligible Individuals | Adjudicating Body | Rating Schedule | Employability Status | Benefits | Maximum Monthly Benefit | |
|---|---|---|---|---|---|---|
| Workers’ compensation | Nonfederal workers injured out of and in the course of employment | Individual state, jurisdictional statutes | AMA Guides in many states; special schedules in Fla, Minn, Calif Utah has its own supplemental rating guide | Unable to work in one’s own occupation or in modified duty if available | Survivor benefits, medical and rehabilitation expenses, wage loss benefits. Tort immunity for the employer | Determined by statute |
| Social Security | Workers <65 yr or survivors who are or have contributed to the SS Trust Fund (SSDI); needy disabled children, aged, disabled and blind adults (SSI) | Social Security Administration | Disability Evaluation Under Social Security (listing of impairments) | Unable to engage in substantial gainful employment that pays $500/mo for >12 mo | Monthly stipend | |
| Disability insurance | Those covered by a group or individual long-term disability plan after a period of short-term disability defined by the policy | Long-term disability carrier | None | Inability to engage in own occupation up to 2 yrs or in any occupation thereafter, depending on the individual plan | Wage compensation | Generally 60-70% of employment income |
| Federal Employees’ Compensation Act (FECA) | Federal employees, including U.S. Postal Service workers | Office of Workers’ Compensation Programs (OWCP) in the U.S. Department of Labor (USDOL) | AMA Guides, 6th ed | Loss of earnings (no schedule loss) because of disability resulting from personal injury sustained while in the performance of duty | 66.6-75% of wages, reasonable medical care. Lump sums not available | 75% of wages if the worker is married or has dependents |
| Longshore and Harbor Workers’ Compensation Program | Maritime employees such as seamen, longshoremen, harbor workers, ship workers (not seamen) | Office of Workers’ Compensation Programs in the U.S. Department of Labor | AMA Guides, 6th ed | Wage loss and schedule loss benefits for injuries arising out of and in the course of employment | Full medical care, death benefits, lump sum awards, 66.6% of weekly wages | 200% of the current national average weekly wage |
| Railroad Workers’ and Seamen | Railroad workers and seamen | Railroad Retirement Board | None | Sickness and unemployment benefits from the Railroad Retirement Board | Railroad workers and seamen must pursue action for damages under the Federal Employers’ Liability Act | |
| Black Lung Benefits Program | Coal miners | Office of Workers’ Compensation Programs in the U.S. Department of Labor | CXR, PFTs, ABGs, and physical examination | Total disability because of pneumoconiosis | ||
| Veterans Disability Programs | Honorable or general discharge from the armed forces or a survivor of a veteran | Adjudication Division of the Compensation and Pension Service of the Veterans Benefits Administration | VA Schedule for Rating Disabilities (VASRD) | Wage loss and schedule loss for the average person unable to follow a substantially gainful occupation | Disability pension, death benefits, hospitalization, medical care, orthotics, prosthetics, durable medical goods, adaptive modifications | $1989 as of 1999 |
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