Classification Based on a Phase Model of Work-Disability

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Veröffentlichungsreihe der Forschungsgruppe Gesundheitsrisiken und Präventionspolitik Wissenschaftszentrum Berlin für Sozialforschung

KSN-0935-8137

P93-207

W ork-Disability and Low Back Pain:

A New Classification M odel fo r R esearch and In terv en tio n

von Niklas K rause

Berlin, September 1993

Dr. med. Niklas Krause M.P.H. ist wissenschaftlicher Mitarbeiter an der School of Public Health, University of California, Berkeley

Publications series of the research group

"Health Risks and Preventive Policy"

Wissenschaftszentrum Berlin für Sozialforschung D -10785 Berlin, Reichpietschufer 50

Tel.: 030/25491-577

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ABSTRACT

Bemühungen auf dem Gebiet der Erforschung und Prävention rückenschmerzbedingter Arbeitsunfähigkeit wurden bislang durch die Verwendung inadäquater Klassifikationen des Rückenschmerzes behindert. Die Notwendigkeit eines neuen Klassifi

zierungssystems wird daher zunehmend anerkannt. Das hier vorgeschlagene neue Klas

sifizierungssystem basiert auf einem Phasenmodell von Arbeitsunfähigkeit, das die Be

grenztheiten statischer medizinischer Rückenschmerz-Modelle übenvindet und die Be

sonderheit und Dynamik der sozialen Umstände des Arbeitsunfähigkeits-Prozesses re

flektiert.

Die Einfachheit dieses in erster Linie auf der Arbeitsunfähigkeits-Dauer und weniger auf klinischen Kategorien basierenden Klassifikationssystems gestattet es allen, die mit Arbeitsunfähigkeit befaßt sind - Forschern ebenso wie Praktikern -, Rückenprobleme zu analysieren und abzuschätzen. Gleichzeitig ist das Modell ausreichend flexibel und er

weiterbar, um detaillierte Erkenntnisse, die der Biomedizin und den Sozialwis

senschaften, der klinischen wie auch der Arbeitsschutz-Perspektive entspringen, einzu

beziehen. Dieses Arbeitsunfähigkeits-Modell kann für die Wissenssystematisierung ebenso nützlich sein wie für die Anleitung zu rechtzeitiger Untersuchung und Interven

tion.

Das vorliegende Papier entstand im Rahmen des Projekts "Arbeitsweltbezogene Präven

tion und Gesundheitsförderung am Beispiel von Rückenschmerzen - Präventionspoliti

sche Konstellationen für Entwurf und Umsetzung zielgerichteter Interventionen" (Bear

beiter: Rolf Rosenbrock, Thomas Elkeles, Uwe Lenhardt) im Berliner Forschungsver

bund Public Health, gefördert vom BMFT (Förderkennzeichen: 07 PHF 01).

ABSTRACT

Attempts to study and prevent disability due to low back pain (LBP) have been hampered by the use of inadequate classifications of LBP, and it is increasingly acknowledged that a new classification system is needed. The new classification system proposed is based on a phase model of occupational disability that overcomes the limitations of static medical models of LBP and that reflects the unique and dynamic social circumstances of the disabling process.

The simplicity of this classification system which is primarily based on duration of work- disability rather than clinical categories, allows the study of and assessment of back problems by all people dealing with work-disability - researchers as well as practitioners.

At the same time the model is flexible and expandable enough to include detailed knowledge originating from the biomedical or social sciences and from the clinical as well the occupational health and safety perspective. It is hoped that this model of disability will be useful in organizing knowledge as well as in guiding timely investigation and intervention.

This paper was written within the scope of the research project "Reducing Low Back Pain by Prevention and Health Promotion at the Worksite - Policy Constellations for Design and Implementation of Targeted Interventions" (project group: Rolf Rosenbrock, Thomas Elkeles, Uwe Lenhardt), which is part of the Berlin Public Health Research Association (Berliner Forschungsverbund Public Health). This research is supported by a grant of the Federal Ministry of Research and Technology (BMFT) (FKZ: 07 PHF 01).

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Introduction

Impact and Determinants of Disability

Low back pain (LBP) is the leading cause of disability for people under age 451 and it is the second leading cause of industrial absenteeism.2 About 60% of all employees experience some LBP at some time in their employment career.3 While 90% of these employees experience relatively short episodes of incapacitation, 10% develop long-term (more than 4 weeks) or permanent disability due to LBP.

This latter group is responsible for about 80% of all costs due to LBP.4 Disability due to LBP increased at a rate 14 times population growth from 1957 to 1976, much faster than disability due to other causes5 (see graph 1).

In order to prevent chronic cases of disabling LBP it is important to know not only why some employees experience LBP in the first place, but why some get better after a short period of time while others do not. Despite four decades of research on spinal disorders, the determinants of long-term disability associated with LBP are essentially unknown. While a large and complex literature exists for risk factors associated with acute LBP, until recently little attention has been paid to factors leading to the persistence of symptoms and to the development of disability due to LBP. The studies that have been done however, share one result: Physical examinations, biomechanical factors or medical diagnosis have little predictive value with regard to return to work, but a range of psychosocial factors seems to be significantly involved in the disabling process.6' 10 One of these studies also indicates that the impact of specific risk factors for return to work depends on the duration of work-disability.8

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N iklas K rause: W ork-D isability and Low B ack Pain p. 2

Current classifications of LBP patients are based primarily on medical diagnosis. They do not reflect the progression of occupational disability, which in turn alters the nature of the condition. The lack of a widely accepted standard classification system for LBP and its sequelae, such as work-disability, hampers researchers as well as practitioners in their attempt to understand and to prevent long-term disability due to LBP. Those whose job it is to stop or reverse the increase of disability due to LBP are in great need of a systematic classification scheme that allows them both to understand the factors leading to disability and also to design and implement sound interventions taking into account the length of time off w ork.

This paper proposes a phase-model of occupational disability associated with LBP that is intended to provide researchers and practitioners with a tool to communicate and organize knowledge about risk factors and interventions aimed at the reduction of work-disability due to LBP.

The proposed criteria of classification and model of disability are not limited to low back pain but apply to other spinal disorders as well. One might also detect similar patterns and phases in the development of musculoskeletal disorders not related to the spine. However, this paper discusses the applicability of the model in the circumscribed area of LBP because disorders of the lower back are of great importance in occupational health. In addition, a critical body of literature about LBP exists to determine strengths and weaknesses of the model.

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N iklas Krause: W ork-D isability and Low B ack Pain p. 3

Current Classifications of Spinal Disorders

Along with changes in medical beliefs about the etiology of disease in general, and of LBP in particular, the classification schemes for LBP have changed dramatically over the past hundred years.11 Currently, the most widely used classification system is the ninth revision of the International Classification of Diseases (ICD)12, which bases some diagnoses on etiology, others on pathologic processes, and others purely on clinical manifestation. In the ICD classification of dorsopathies, radiologic changes are emphasized, with a specific section reserved for both ankylosing spondylitis and spondylosis. The section "Intervertebral Disc Disorders" covers lumbago and sciatica due to disc displacement, whereas the section "Other and Unspecified Disorders of the Back" covers stenosis, lumbago, and sciatica without disc displacement, as well as backache and other unspecific back disorders. This classification of back disorders is satisfactory for ordinary clinical purposes and for directing health care resources, but it is difficult to use for an evaluation of the effects of various forms of intervention, it is too ambiguous for research on etiology, and — most important in our context — it is not suitable for understanding the disabling process since it makes no reference either to duration of illness or disability.

A number of classification schemes have been proposed to deal with the perceived inadequacies of the ICD. From the 1950's to the 1970's, proposed classifications differed mainly by diagnostic categories: (i) Hult13 divided back symptoms observed in a large field survey into "insufficientia dorsi" (fatigue or pain of more or less intermittent character in the low back, symptoms frequently provoked only by certain forms of exertion, particularly work in a forward-bending position); "lumbago" (aching and pain of various types in the low back - in a typical

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attack of acute lumbago the person can scarcely move because of pain); and

"sciatica" (occasional pain, which radiates into either leg), (ii) Lockshin and co

workers14 gave short and clear definitions of the three entities they used: "probable lumbar disc disease" (history of back pain radiating to the leg, for which medical treatment was sought and prescribed); "possible lumbar disc disease" (history of low-back pain not radiating to the leg, for which medical treatment was sought and prescribed); and "low-back syndrome" (low-back pain necessitating bed rest, medical treatment not sought), (iii) The Arthritis and Rheumatism Council of Great B rita in 15 adopted the following definition for disc disease to determine its prevalence: "Pain in the back or neck which was either recurrent or of more than 6- week duration, and which could be accurately localized, as well as a history of pain radiating along the distribution of a spinal nerve root at some time, though not necessarily at every attack", (iv) Kelsey16 in her case-reference study of herniated lumbar intervertebral discs used definitions for "surgical cases", "probable cases", and "possible cases" that are even more complicated than those adopted by the Arthritis and Rheumatism Council, and are based on radiological examination, interview, clinical examination, and hospital charts.

Since the 1980's, classification schemes began to utilize duration of symptoms as an additional category : (i) Nachemson and Andersson17 suggested a classification of low back pain for screening purposes based on the patient's own description of symptoms, mode of onset (immediate, gradual) and duration of symptoms (acute, subacute, chronic, recurring), (ii) Scandinavian experts on work- related back disease18 have agreed on a series of questions on back symptoms for use in occupational health which focus on activity limitations and health care utilization, without providing any classification scheme, (iii) The Quebec Task Force on Spinal Disorders19 suggested a classification system for 13 spinal disorders in

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N iklas Krause: W ork-D isability and L ow B ack Pain p. 5

which the main categories are clinical diagnoses primarily based on medical history and physical examination (see table 1). The classification includes 3 subcategories for duration of symptoms from onset (acute = 1-7 days, subacute = 1 - 7 weeks, and chronic = >7 weeks) and 2 subcategories for work status (working, idle). These subcategories are applicable to the most common spinal disorders only, yielding altogether 28 clinical categories. The Quebec model is a significant step towards a classification of LBP that might be helpful for occupational disability since it reflects to some extent different stages of the disease (acute, subacute and chronic) and one important social variable (work status). However, these categories are too broad to reflect the distinct phases of occupational disability and they are subordinated to the main categories which are remain based on medical examinations and clinical diagnoses.

None of the classification systems described has won general approval in the scientific community. More importantly, the current classification systems for LBP fall short in helping us understand the development of occupational disability.

There are at least three reasons for this.

(1) Current classification systems require medical information that is often unreliable, unavailable or non-existent.

(2) Duration of occupational disability, the major feature in occupational LBP, is not accounted for by any existing classification system. (Although reference to duration of symptoms is made in some new classifications systems, duration of symptoms is difficult to determine and does not necessarily represent duration of work-disability.)

(3) Currently used categories are primarily medical and therefore do not characterize an ultimately social phenomenon like long-term occupational disability.

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Social Dimension of Occupational Disability

It is impossible to adequately describe disability exclusively in medical categories. While a medical condition is necessary for the development of a disability, disability (especially of long duration) is never solely the result of pathology or functional limitation but is essentially a social phenomenon.20 Specifically, disability is "the inability or limitation in performing socially defined activities and roles expected of individuals within any social and physical environment."21’ 22 According to this definition, work-disability is any limitation or inability in performing the working role defined by occupation or other economic pursuits. In the case of disability due to low back pain, descriptions based on biomedical models have failed for several reasons:

First, there is no consensus within the medical professions on how to diagnose or classify patients with disability due to low back pain.17- 23- 24 In most cases, a specific cause or lesion for LBP cannot be determined.25- 26 In a study of acute LBP seen by general practitioners in London, England, no specific reason for the pain could be found in 79% of first episodes in men and 89% of first episodes in women25. Among working-age men and women in Sweden sick-listed because of back pain, 51% had no objective signs of back trouble; the proportion without clinical evidence increased with the length of absenteeism, from 40% of workers out for seven days to 70% of those out for three months or longer.26 Similarly, recommended treatment approaches vary widely among clinicians and most common therapeutic approaches either lack scientific evidence for effectiveness or have been proven ineffective.19 Although it is important to standardize methods of diagnosis and treatment of LBP, it is questionable if a standardized medical

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N iklas Krause: W ork-D isability and Low B ack Pain P- 7

approach alone could significantly enhance our understanding of the disabling process.

Second, diagnostic subgroups of LBP have little predictive value with regard to the development of disability. For example, the diagnosis of radiographically verified degenerative changes of the spine does not predict the development of future LBP.27 Several recent studies demonstrate that physical examinations, biomechanical factors or medical diagnosis do not predict return to work, while a range of psychosocial factors seems to be significantly involved in the disabling process.6"10

Third, common medical treatment procedures have little impact on outcome.

For instance, among those seeking care for LBP from family physicians almost half improve within a week and almost 70-90 % improve within a month, regardless of treatment.28

These facts, and the rapidly increasing number of disabled individuals (graph 1)29"31, support the hypothesis that factors other than the spine itself play an important role in the disabling process. An increasing body of literature suggests that occupational disability is a result of multiple risk factors that are related to the individual, the work environment, the non-occupational social environment, the medical system, the legal system, the systems of workers' compensation, disability insurance, and the economic environment including social security and welfare (graph 3).7

A recently published prospective study of 3000 Boeing employees, for example, examined a wide range of workplace and individual physical,

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demographic and psychosocial factors as predictors of industrial back pain reports.

Among the most notable findings was a strong association between workplace perceptions, psychological factors and back injury reporting.32 In comparison, a variety of physical factors once suspected as risk indicators were not associated with reporting back pain in this setting.33"36

Developmental Character of Disability

Another, and perhaps the most important, reason why biomedical models have failed to adequately describe disability is that classic clinical diagnostic codes assume a fixed status of the condition. In fact, there is much evidence for an evolving disabling process with distinct phases.21* 22> 37-39 which determine vulnerability to certain risk factors depending on the time from onset of the condition. Specific risk factors can be relevant or not, depending on the phase of disability. For example, it had been reported that claimants who have retained a lawyer are less likely to return to work than those who have not. 40 However, it is important to notice that virtually no appeals are filed within 90 days of the claimant's date of injury and less than one fourth within one year.41 This suggests that litigation is not a risk factor for work-disability within the first three months following the injury but might play a role only after chronicity has been established.

Another example of the phase-dependency of risk factors are emotional factors.

Anxiety, depression, hypochondria, and neuroticism have been shown to be associated with LBP.7*42 Although initially they often appear to be a consequence of the prolonged pain syndrome rather than a risk factor 43* 44 once these secondary conditions are present, they seem to have a negative influence on the course of the disease if they are not treated.45 Gallagher and co-workers recently demonstrated an interaction between length of time off work and the impact of

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specific risk factors for return to work.8 Clearly, research efforts to determine causal factors need to account for the duration of work-disability.

The major impact of LBP in industrialized nations stems from associated work-disability. Little is known of the determinants of occupational disability. To develop prevention programs for LBP, we first need to identify the risk factors of work-disability due to LBP, and for this, it would be useful to have a more appropriate classification system.

Classification Based on a Phase Model of Work-Disability

We suggest that a more useful classification of occupational LBP would be organized within a framework of work-disability that takes the social and developmental character of disability into account. Other authors have proposed phase models of disability. These models have either focused on psychological issues37’ 39 or on physiological changes22 21; none have considered duration of work-disability. We base our classification system of LBP on a model of occupational disability consisting of 8 distinct phases that describe consecutive steps from the occurrence of non-disabling LBP to the development of permanent work-disability (see graph 4). The phases are defined primarily by the presence and duration of work-disability.

A critical feature of this model is that each phase involves a different set of interactions with the social environment, and especially with the medical system and the system of worker's compensation. Worker's compensation and other social services influencing the course of disability differ between states and countries.20

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The phase model tries to embrace these differences, although, for the sake of consistency, the situation in North America is the preferred example for the convergence of medical and social parameters in the disabling process throughout the text.

In the following pages, each phase is described in terms of definition by working status, its significance and frequency, measurement methods, medical status (including a range of normal healing periods for common underlying medical conditions—separately for surgical and non-surgical cases), and insurance policies (worker's compensation).The chance of return to work is illustrated by graph 2. In addition, some comments on possible or implemented interventions for each phase will be made.

The frequency data presented stem from different insurance systems in different societies and need therefore be perceived with caution. However, the average healing time for a work-related back injury has been reported to be quite similar in industrialized countries, i.e.36 days in Scandinavia46, 28.6 days in the U.S., and 32.6 days in Great Britain3, indicating commonalities in the course of disabling LBP despite differences in social policies.

Phase 1: Non-Disabling Low Back Pain Episodes

Definition: Phase 1 refers to the occurence of any pain experienced in the

lower back during any period prior to the formal report of a back injury. LBP is defined as pain, ache or discomfort experienced in the lumbar and sacral region of the back. This broad definition of LBP includes subgroups of back pain syndromes

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like sciatica where the pain is radiating down from the lower back into one or both legs.

In Phase 1, work-disability has not yet occurred. While there is no absence from work, the pain might have interfered in other ways with the job, such as reduced performance, reduced quality of work, postponement or avoidance of certain tasks, or delegating work to others. One might view these interferences as a less severe form of work-disability, but for the sake of simplicity and for the purpose of comparability with labor statistics we restrict the definition of work-disability to actual absence from work.

Significance: The occurrence of non-disabling low back pain is a

predisposing condition for the development of disability and may result in some limitation in how work is conducted.

Frequency: There are no reliable data on the frequency of non-disabling

LBP episodes. From the surveys that have been done, however, it might be estimated that about 50% of working-age adults experience back symptoms each year.47'49

Measurement: Surveillance using questionnaires, interviews, or medical records.

Medical status: Only a minority of cases seek medical advice during phase

1. Although previous episodes of LBP are a known risk factor for the occurrence of LBP50, recurrent episodes of non-disabling LBP do not present a different clinical picture than do first episodes.19

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Worker's compensation: No regulations or compensation exist.

Interventions: The main risk factors for the occurrence of LBP are well

established; they include low education, low income, poor conditioning, poor general health, previous LBP, heavy manual labor, heavy lifting, whole body vibration, driving motor vehicles, prolonged sitting, short time on the job, poor job satisfaction, high work stress, poor supervisory rating, and mental stress.7

Interventions during phasel need to be more general than in later_phases for two reasons. First, since about half the working-age adults are likely to have some back problem each year, programs in this phase have to be directed to basically every employee. Second, unless specific problem areas are recognized, interventions would have to address a wide variety of risk factors including such psychosocial factors as job satisfaction. Faced with these broad needs on the one hand and with economic considerations on the other hand, most reported interventions use an (relatively low capital-intensive) educational approach focusing on information and safe working technics, sometimes combined with fitness trainings. Underrepresented are engineering solutions which sometime require more capital investment: In his review of 19 intervention studies Wickström51 mentions only one study actually aimed at an alteration of mechanical work conditions.52

Even though they are potentially beneficial, broader strategies, including organizational changes such as implementation of autonomous work groups or job enrichment, are not reported in the back pain literature, probably because the outcomes of interest have been productivity or quality of work rather than health.53 However, the literature on other musculoskeletal diseases representing cumulative trauma disorders54 and many non-scientific reports by government and industry 55 indicate a definite potential for the design of cost-effective primary prevention

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programs that are aimed at worker and management training and/or the redesign of the physical and organizational work environment.

Prevention of LBP in form of pre-employment screening has not been successful.56 Physical examinations, x-rays, fitness or strength tests have not been demonstrated to be effective. Safety considerations disqualify routine x-rays and some fitness or strength tests as a screening tool. A medical history of previous LBP, though of some predictive value, is not easy to obtain from job aspirants prior to employment and it would lead to an unfeasable major reduction of the potential workforce.

According to Himmelstein and Anderson56 all of the available methods for predicting low back pain and disability in a currently asymptomatic population have serious technical, ethical and legal limitations. From a technical point of view, none of the predictive tests appear to have sufficient sensitivity or specificity to justify routine usage. The most sensitive indicator (a past history of low back pain) lacks reliability (workers may not admit the history during a preemployment screening) and specificity (many people without any future LBP will be prevented from being hired). From a legal point of view, all of the techniques described hold potential for significant discrimination against legally protected groups. Making employment decisions with regard to a past history of LBP or on the basis of an x-ray will lead to systematic age discrimination and discrimination against the handicapped. The use of muscle strength-testing will systematically discriminate against women and certain ethnic groups.

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Niklas Krause: Work-Disability and Low Back Pain p. 14

Phase 2: Formal Report of Work-Related Injury or Illness

Definition: Phase 2 begins with the first formal report to the employer or the

worker's compensation administration of a work-related injury or illness affecting the lower back. Phase 2 ends with the first day or shift off work due to LBP.

Significance: The placement of phase 2 between non-disabling and disabling LBP

describes the majority of cases, but some employees delay filing a claim until after work-disability has already occurred. Other employees— regardless of whether their LBP is work-related or not—never file a claim and stay either in Phase 1 or enter subsequent phases without going through Phase 2. They comprise a subgroup of workers with non-compensable LBP who are not eligible for worker's compensation, and who typically do not show up in labor statistics or scientific publications, which are often based on worker's compensation data. Self- employed and non-employed people form two other subgroups of patients not eligible for worker's compensation. All three subgroups might enter the following phases, but differ with regard to insurance policies as described in the sections on worker's compensation.

Many studies of risk factors for LBP are based on filed reports as the only indicator for LBP. Since only a small proportion of afflicted employees report LBP, the identified factors might predict reporting behavior rather than LBP. For this reason risk factors for reported LBP in Phase 2 might differ from risk factors of non- reported LBP in Phase 1.

Frequency: Of all working adults experiencing LPB, 5-10% file formal reports of work-related injury or illness.57’ 58

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Measurement: First Reports of a Work-related Injury or Illness including the lower back.

Medical status: After a formal report the worker may be referred for an initial

medical evaluation either paid for by worker's compensation or at the direct expense of the employer. Free choice of the treating physician is often restricted. In California, for instance, employees may be free to consult a physician of their choice for up to 30 days post injury if they requested such procedure before the injury happened. In Germany, depending on severity of the injury, industrial accident insurance requires an initial examination by a physician certified for that purpose by a certain amount of training in surgery ("Durchgangsarzt").

Worker's compensation: Filing a report is a necessary condition to become

eligible for compensation. After a report has been filed the employee and employer are contacted by representatives of worker's compensation. This process, called claim adjustment, might be handled primarily as an administrative matter, but it might also include personal interactions as well as work-site inspections and other activities. A primary goal of the claim adjustment process is to determine whether the reported injury was work-related. In Germany, the majority of occupational LBP (comprising a cumulative trauma disorder) has until very recently not been handled within the industrial accident insurance system but rather within the health and disability insurance system, therefore no comparable reporting experience exists at this time.

Worksite inspections are an exception in the United States because workers' compensation is not formally involved in work-site prevention. In G erm any, w here in d u stria l accident insura nce c a rrie rs (e.g.

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Berufsgenossenschaften) operate under a legal mandate to ensure a safe work place, worksite inspections are a routinely performed after serious accidents.

Interventions: There are two types of intervention strategies. The first strategy

tries to reduce or postpone the reports of LBP in an attempt to lower the frequency of claims. The second strategy tries to facilitate an early report of LBP regardless of origin, combined with some early intervention program in order to prevent the development of costly long-term disability.

The first strategy might employ very different approaches. The classic approach is to deny risk factors in the work environment and to discourage reporting of back injury. This might be achieved through norms and sanctions at the workplace or by means of restrictive regulations at the political level. The latter was the case in Germany until 1993, where LBP had not been eligible for being handled within the industrial accidence insurance system as a work-related illness.

A different approach within the first strategy is primary prevention by redesigning the job of employees at risk. The classic example is ergonomic solutions reducing physical loads on the spine, which have been successfully employed in material

handling industries. Such job redesign approaches are basically the same as in phase 1, but from phase 2 on, limited resources can be used more efficiently by targeting high risk groups (which can be identified by number or costs of filed claims).

An example for the second strategy, i.e. encouraging early report and early intervention, is the Chelsea back program at American Biltrite in Cambridge.59 After exhausting traditional health and safety measures, a program had been developed that changed management's attitudes toward the back pain sufferer towards empathy and trust and encouraged early reporting of back pain. Every employee who reported back pain received on-site physical therapy for 8-10 days

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Niklas Krause: Work-Disability and Low Back Pain _{p. 17}

including one-to-one education while keeping the employee on the job, on light duty if necessary. The results of this program revealed an important paradox: While the incidence rate of low back cases increased, the frequency of lost-time low back injuries decreased. Within 2 years, reports of work-related LBP injuries increased by over 100%, while the rate of disabling LBP was reduced by 50%. At the same time, compensation costs were reduced by 9O%.60 This demonstrates not only the potential cost-effectiveness of early intervention programs, but also the necessity of using outcome measures for LBP other than the number of formal reports for evaluating intervention methods, namely compensation costs or duration of work- disability (which are related to each other).

Phase 3: Short-term Disability (<1 Week)

Definition: This is the first phase where absence of work occurs as a result of

LBP. Phase three is defined as absence from work due to LBP for up to six consecutive work days.

Significance: Phase 3 is distinguished from Phase 4 in the number of

consecutive days of work lost, that is 1-6. A common feature of most insurance systems in both the U.S. and in Europe is that it is during this time that a medical examination is required if a worker wants to be eligible for wage replacement, even though the exact timing of this requirement as well as the type of insurance carrier may vary. However, by the end of one week (i.e. the beginning of Phase 4) virtually every individual has now established contact with the medical system in addition to the insurance system, regardless of the local differences in policy.

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Niklas Krause: Work-Disability and Low Back Pain p. 18

Frequency: From data reported in a prospective Swedish study of all sick-

listed patients among 49,000 subjects in Gothenburg, one can calculate that about 7.5% of working-age adults were disabled for up to one week because of LBP during a one year period.61 Not all patients who report an occupational injury or illness enter this phase, though the percentage of people who report an injury but do not stay away from work has not been published.

Measurement: Our operational definition of work-disability requires a

minimum of one work-day or one shift of not being able to perform the pre-injury job. The same definition is used by the U.S. Department of Labor Bureau of Labor Statistics.62 Assessment is not always straightforward. Four major alternatives exist:

(i) Work-disability defined as absence from work can be determined from payroll records. However, in order to link absenteeism with low back pain, an additional database is needed to determine the reason for absenteeism, (ii) When all employees are covered by health insurance and when the health insurance or the employer provide wage replacement payments based on a physician's diagnosis (regardless of whether the condition is work-related or not-as is the case in many European countries, Australia and in Canada-) the diagnosis might be available from health insurance records. However in the U. S., where health insurance typically does not substitute lost wages and where many employees are not covered by any health-care plan at all, the reason for work-disability has to be obtained through direct contact with the employee (self-report) or from the medical records maintained in the worker's compensation system, (iii) Retrospective self- report is not a reliable method to determine time off work.63 (iv) An assessment of work-disability based on worker's compensation data is more reliable but introduces a conservative bias, since LBP has to be perceived and formally

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reported by the employee as a work-related injury or illnesses in order to show up in the records.

Medical status: Short-term disability lasts about as long as the normal

healing period of uncomplicated acute LBP injury (minor strains and sprains, low impact injuries). Clinically, Phase 3 corresponds to acute LBP, which is considered to last no longer than one week by most clinicians.19 The employee may rely on self-treatment, medical care or alternative health care.

Worker's compensation: If the injury was reported, and if the injury was

judged to be work-related, any medical costs are reimbursed through worker's compensation in North America. In most U.S. systems the employee is not eligible for indemnity payments through worker's compensation during the first week. In European countries and New Zealand wage replacement takes place through health or disability insurance from day one on, regardless of whether the injury is work-related or not.

Interventions: It is during phase 3 when the injured employee experiences

first reactions from co-workers, supervisors or family members and makes first contact with the claim-adjuster as well as with the attending physician or nurse. It is conceivable that the quality of these initial contacts sets the tone for further communication and the mutual perception of involved parties, however, no data on risk factors or interventions specific to phase three have been published.

One intervention, although not limited to phase 3, did start in phase 3 and is therefore mentioned here: The Very Early Intervention Project carried out by the West Virginia Worker's Compensation Fund among coal miners.64 The study was based in part on the insight that intervention programs within one or two weeks

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Niklas Krause: Work-Disability and Low Back Pain _{p. 20}

after injury could not be accomplished using the formal written report of injury.

Therefore an early telephone contact was chosen as the alternative means for recruiting individuals into the intervention group. (A control group was handled the in the customary way) A trained nurse would visit the employee, evaluate his condition and with a questionnaire assess the risk for long-term disability. For people at high risk for long-term disability a nurse and a counselor would then offer counseling and guidance, and coordinate primary care, medical specialty and physical therapy services, and psychological_services if necessary. This form of improved case management beginning during week one after injury did not lower disability or any immediate costs compared to the normal administration of services. However, the researchers note, the intervention was hampered by lack of resources such as physical therapy in the rural area. Furthermore, the initial evaluation of every employee who had been out of work for up to 7 days might not be cost-effective, because most of them would have been expected to recover spontaneously. However, after one year, the medical costs of the intervention group stabilized in contrast to still increasing costs in the control group.

Phase 4: Timely Intervention (1-7 Weeks)

Definition: Phase 4 is defined by work-disability of 1-7 weeks duration. The

label "timely intervention" is programmatic rather than descriptive and refers to timely medical, ergonomic, and administrative action.

Significance: Conservative medical interventions as well as so-called early

intervention programs (which often address medical and non-medical factors) are designed for this phase and are of limited value in later phases. If treatment has failed, Canadian experts recommend a medical evaluation by a specialist or a

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team of specialists no later than 4-6 weeks after onset of disability.19 Other authors advocate an independent medical evaluation after 2 weeks of continuous work- disability.65

Frequency: From the population based Swedish study mentioned above,

one can estimate that about 2.5% of working-age adults were disabled for up to six weeks because of LBP during a one year period. 61 Of ail formally reported occupational back-pain episodes, about 50-60% enter this phase.46’ 66

Medical status: Phase 4 disability lasts about as long as the normal healing

period of severe LBP (e.g. LBP radiating down one or both legs labeled sciatica;

heavy impact injuries; minor fractures). Clinically, phase 3 corresponds to

"subacute" LBP as defined by the Quebec Task Force on Spinal Disorders.19 The employee may rely on self-treatment, primary medical care, treatment by medical specialists and/or by other health-care providers. Although not uncommon, surgical treatment is not warranted in most instances during the first month of LBP, unless progressive neurological impairments occur such as paralysis of the leg or foot, or fecal or urinary incontinence.67

Worker's compensation: In most industrialized countries documentation of

medical evaluation is required after 3-7 days of consecutive work-disability in order to become eligible for wage replacement, regardless whether the insurance carrier is worker's compensation, a national health plan, or disability insurance. The amount and duration of payments the employee is entitled to, as well as the actual time of receiving the payments, varies considerably between states and carriers.

However, as a general rule, payments depend on a medical evaluation and coverage starts with the beginning of phase 4.

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Interventions: During phase 4 medical and/or paramedical treatment or

rehabilitation, i.e. secondary and tertiary prevention, have their greatest potential.

In the previous phases the necessity for medical treatment and its effectiveness is rather questionable.25’ 26> 28 This is true also in later phases (5-8) where the potential benefit of medical interventions decreases rapidly.19*65

The lack of a specific diagnosis and the inconsistency of medical care may contribute to a longer duration of disability and a poorer prognosis for the injured w o rker.68 Wiesel and colleagues69 applied a standardized diagnostic and treatment protocol to two industrial settings involving over 29,000 employees. In one, the patients were seen weekly at an orthopedic clinic, while in the other they were seen only once. In both settings, the evaluation and treatment of workers with back injuries were standardized according to a flow sheet made available to all health care providers, and any deviation was scrutinized and corrected by the investigators. In both settings, treatment costs and disability were reduced, leading to the conclusion that consistency through the use of a standardized care algorithm may improve the prognosis for LBP in the workplace.

In order to demonstrate the potential benefit of both such programs, some specific results of the Wiesel et al study are presented here: The number of LBP patients at site one (weekly evaluations) decreased 29% in the first year and 44%

the second; days lost from work decreased 51% the first year and 89% the second;

low back surgery dropped 88% the first and 76% the second year. Results for the other site (one evaluation after one week of disability) demonstrated a decrease in the number of LBP patients by 41%, in days lost from work by 60%, and in financial costs by 55%.

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Phase 5: Long-term Disability (>7-12 Weeks)

Definition: Phase 5 is defined as work-disability of more than 7 and up to 12 weeks.

Significance: According to Hendler's stages of pain it is around the second

month of continuing pain that the patient's expectation to get well fades.38 This development is one reason why the right timing of possible interventions matters. If at all indicated, surgical procedures should be executed at the beginning of this phase-after 6 weeks of conservative care and/or job modification. Post-surgical rehabilitation including reconditioning will normally require the remainder of that phase for surgical cases. Non-surgical cases entering phase 5 should raise a red fiag: Single-handed case management by a primary care physician is considered insufficient in this phase and should to be supplemented by supervision from a specialist and /or a multidisciplinary team who employ a comprehensive rehabilitation effort.19

Frequency: Less than 10 % of all reported cases of LBP enter this phase.28-

66

Medical Status: (Conservative care) Long-term disability reflects an

abnormal duration of LBP if the disorder was not treated surgically. Clinically, LBP in phase 5 would be considered "chronic" LBP according to the Quebec classification.19 Other authors consider LBP as chronic if it lasts longer than four weeks67 or three months.17,23 Specialists in the treatment of pain, however, talk of a "chronic pain syndrome" regardless of the underlying medical condition, if the pain lasts longer than 6 months. (Here the term "chronic" is reserved for Phase 7,

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which describes the second half year of disability, and which is called "chronic disability"). If not performed during the previous phase, a specialist team effort is advised to rule out any rare pathology affecting the spine.

(Surgical Care) For patients who undergo spinal surgery, a minimum of 6-12

weeks of restricted activity after the operation is considered a normal healing period for most procedures. Including a recommended course of conservative treatment of about 6 weeks duration before surgical intervention, Phase 5 reflects the minimum duration of work-disability to be expected for patients with surgical treatment.

Worker's compensation: Same as during Phase 4. It is noteworthy that

within the first three months after the report of injury virtually no claims have been appealed (in the State of Washington).41

Interventions: For a minority of patients elective surgical treatment is the

treatment of choice at this phase. For the vast majority of patients (including those who underwent an operation) a conservative active rehabilitation program is needed, although, at present, availability of high quality rehabilitation is often limited. Major components of rehabilitation programs are one-to-one physical therapy, back education, counseling, functional restoration, and work hardening in conjunction with light duty, job redesign, or vocational retraining. A combination or series of these approaches might be appropriate for an individual person, however, research is still needed to determine who will benefit the most from which approach.

Equally important is to address psychological and social issues before the disabled role becomes a habitual way of life.70 In the literature on the psychology of low back pain many attempts are made to describe methods for predicting which

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individuals are at significant risk of failure to respond to either conservative and/or surgical care.6, 8> 9> 71‘74 However, experienced clinicians claim that the current models have not helped to predict either who will get better, who will need help, or what kind of help will be required. Anderson and Moskowitz39, who have performed psychiatric evaluations on over 1500 patients with chronic disabling low back pain, describe the psychological issues encountered by the those patients as a cyclical process of recovery that involves three distinct phases which they named

"the threat, the pit , and the renewal". For them, the "formation of a consoling relationship" is central and seems to improve outcome. The authors assign the psychiatrist the following role: "The patient's developmental history, especially as it relates to past and present attachment behavior, should be explored. The meaning of illness to each individual must be examined to help with acceptance and adaptation during and after the healing process. The psychiatrist has to be an active part of the overall multidisciplinary treatment team, not allowing the patient to be dismissed as a 'psychiatric case.'... The treatment may utilize adjunctive antidepressant therapy, hypnotherapy, behavioral therapy, strategic therapy, insight oriented therapy, supportive therapy, couples or family therapy." However, much more research is needed in this area. As the authors state in their conclusion:

"More intensive study of those that do get well in a timely manner with long-term follow-up is extremely important to avoid the bias of a_disability based model. The role of social expectations of the family, the work environment, the medical profession, and the third party payers toward the person with spine pain needs further investigation. A more comprehensive model of those actually at risk for chronic disability is extremely important. The model needs to be tested by therapeutic interventions consistent with the model's theory."39

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Phase 6: Late Rehabilitation Phase (3-6 Months)

Definition: Disability in Phase 6 is defined as not being able to perform the

pre-injury job at levels of regular pre-injury working hours for 3-6 months.

Employees assigned to another job on a temporary basis, employees working at a permanent job less than full time (e.g. within the context of a light duty program), and employees who have not resumed any work yet, constitute three different subgroups of this phase.

Significance: This phase is labeled "rehabilitation phase" indicating a

definite shift in required case management. Medical treatment modalities designed for acute pain and for structural pathology are generally not appropriate in this phase anymore (with the exception of occasional flare control) and should be replaced by active rehabilitation programs. The attribute "late" indicates that concepts for "early rehabilitation" exist which focus on earlier phases in an attempt to prevent long-term and chronic disability.

Frequency: Studying a randomized sample of 40-47 year old men and 38-

64 year old women in Göteborg, Sweden, Andersson and Svensson reported that 4% of the men and 3.5% of the women had been off work for more than 3 months.3 Less than 10% of all formally reported cases of LBP enter this phase.66

Medical status: (conservative care) Phase 6 disability reflects an abnormal

duration of LBP if the disorder was not treated surgically. Clinically, LBP in phase 6 would be considered "chronic" by everyone treating LBP, although some authors exclude surgical cases from this categorization if the pain does not persist longer than six months post-operative.19

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(Surgical care) For patients who undergo spinal surgery, overall work-

disability of 3 to 6 months is considered normal. A normal course of conservative treatment of 4 to 7 weeks duration before surgical intervention, a postoperative healing period of 6 to 12 weeks, and a postoperative rehabilitation program with increasing activity for 4 to 6 weeks add up to a normal rehabilitation period of 14 to 25 weeks for patients with spine surgery.

Worker's compensation: Most worker's compensation systems establish a

so-called "light duty" program where after three continuous months of disability the employee may return to work on reduced hours. Worker's compensation pays the lost wages. The employee is also eligible for rehabilitation programs like work

hardening, counseling, vocational retraining etc. (California law requires that the employee is offered rehabilitation after three months of consecutive work- disability).

Interventions: One major goal of interventions in this phase is to recondition

the disabled worker. According to rehabilitation specialists75 interventions have to take into consideration that the long-term disabled employee faces problems on several fronts. Without a diagnosis, cure, or clear prognosis, the patient may pass from one practitioner to another in search of "the answer". In the meantime, the individual's role within the family, community, and work group may be profoundly altered. Often encouraged by physician and family alike, the patient may avoid activities that he fears might cause reinjury. A progressive pattern of self-limitation from previous work and recreational activities often results in a general

"deconditioning syndrome".76

Work hardening, work simulation and functional restoration programs are designed to recondition the disabled employee using a multidisciplinary approach.

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The core team usually consists of a physical therapist, occupational therapist, vocational therapist, and psychologist.

The characteristic that distinguishes work hardening from previous treatment approaches is its use of work simulation on a graded basis. In late 1988 more than 500 programs in the United States identified themselves as providing work

hardening services.77 Although success of work-hardening with regard to return to work has been reported78' 80, no study has provided a control group for comparison. In addition, length of time of disability varies considerably between programs and between participants. Although reports of program effectiveness should be presented in terms of initial patient characteristics, such data are not currently available. Variation in patient populations may account for the wide range of work-hardening program outcomes reported by Niemeyer and Jacobs.80

Functional restoration is the most recent programmatic development for workers with chronic back pain disability. Although functional restoration programs integrate behavioral modification and work-hardening techniques, they are distinguished by repeated measurement of strength, flexibility, and general fitness as objective guidelines for therapy and occupational planning.75 They have been tested among workers with long-term disability, however the majority of patients have been in later phases81 76 and examples will be described for phase 8.

Phase 7: Chronic Disability (>6-18 Months)

Definition: Chronic disability is defined as not being able to perform the pre

injury job at levels of regular pre-injury working hours for more than 6 months up to 18 months. People who do not resume any work and those who perform their previous job during reduced daily hours in the context of a light-duty program constitute two different subgroups of this phase.

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Significance: The significance of the Chronic Disability Phase is that after six

months of work-disability, treatment and rehabilitation programs geared towards the spine alone are inappropriate and have to be supplemented or replaced by interventions focusing on the pain experience itself, psychosocial and/or occupational factors.

Frequency: About 7% of all cases of reported LBP enter this phase.30

Medical status: In Phase 7 the underlying condition of the spine cannot be

considered the primary cause for the persistence of pain in most patients. The diagnosis "chronic pain syndrome" is sometimes used in this situation. This diagnosis is based solely on the presence of continuous disabling pain for more than six months and does not refer to any specified pathology of any organ system.

Some psychologists82 maintain that this pain represents a behavior reaction, whereas neurophysiologists lean toward the hypothesis that nervous structures irritated for a prolonged period develop new mechanisms of pain generation.19 Chronic pain has also been described as a variant of depression.83 While the

"chronic pain syndrome" is sometimes associated with objective signs (i.e., limitation of motion, hyperesthesia, muscular weakness, etc.), in the majority (70- 80%) of patients, there is no evident major objective sign.26

The diagnosis "chronic pain syndrome" is not appropriate for patients with painful iatrogenic alterations of the spine due to unsuccessful, complicated or repeated surgery. The major chronic "side-effects" of spinal surgery are spinal instability and scar tissue formation, which are considered mechanical causes for chronic back pain and which may affect 2-5% of all surgical cases.67

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The diagnosis "chronic pain syndrome" is also inappropriate in situations in which the failure to improve an unhealthy job environment causes the recurrence of symptoms whenever the patient tries to resume his work. Thus patients with

"chronic pain syndrome" do fall into Phase 7, but the Chronic Disability Phase also includes those patients suffering from surgical complications as well as those patients experiencing recurrent symptoms due to the neglect of job-redesign that do not qualify for the medical diagnosis of a chronic pain syndrome.

Worker's compensation: Basically unchanged. However, during this period

litigation is more common than in earlier phases. The analysis of 2318 claims of back sprain or strain with more than 90 days work time lost in Washington State demonstrated that about one third of chronic claims are eventually appealed, however, no appeals were filed within 90 days of the claimant's date of injury and less than one fourth within one year.41 Legal and economic considerations influence the behavior of the patient as well as that of health care providers, insurance carriers and other players, but the effect on return to work remains controversial.84"86

Interventions: In the past 20 years more than 1000 pain clinics have been

developed in the United States for the treatment of patients with chronic pain. Even among professionals , there is a great deal of misunderstanding about the goal of

"pain clinics", which is to change a chronic pain patient into a person with chronic pain.87 This requires restoring function and decreasing disability, not necessarily eliminating pain. The patient's goal, however, is usually quite different. It is relief of pain. The patient knows only an acute pain model in which pain means tissue damage and therefore continuing pain means continuing damage. The different

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goals may lead to disappointment and misunderstanding unless they are clarified at the onset of treatment.

Pain clinic programs include a wide variety of passive therapies, such as ultrasound, manipulation, massage, acupuncture, electrical stimulation, and facet and epidural injections. Many programs share a reliance on behavioral modification. The fundamental goal of most behavioral approaches is the reduction of disability through behavioral change rather than the direct diminution of pain.

With or without the above-mentioned passive modalities, pain centers use such techniques as group and individual counseling, hypnosis, stress-management, biofeedback, educational classes, and family sessions. The intensity of these programs ranges from occasional outpatient treatment to intensive inpatient programs. Some authors recommend the use of active reconditioning like functional restoration within the setting of a pain clinic.87 As the content of these programs varies, so does the disciplinary representation by medical sub

specialists, counselors, physical and occupational therapists, and so on. However, in contrast to work hardening programs, physicians are core staff members of pain clinics.

The efficacy of the pain center approach to chronic back pain rehabilitation is controversial.88’ 89 Differences in program content and pre-treatment patient characteristics defy generalizations of therapeutic effectiveness. To date, there does not appear to be conclusive evidence that isolated aspects of pain center programs reduce subjective reports of pain, though improvements in activity level, medication use, and other pain related behaviors have been reported.89 Detoxification, particularly from narcotic analgesics, is usually more appropriate in a pain clinic setting than in less medically oriented programs.

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Phase 8: Permanent Disability (>18 Months)

Definition: Mier 18 months duration, work-disability is considered permanent based on the low chance of return to work in this phase (see graph 2).

Significance: Permanent disability typically results in early retirement,

unemployment or entrance into a different profession. However, permanent separation from the pre-injury workplace happens in any of these ways at earlier phases too.

Frequency: About 4.5% of all claimants enter this state of permanent (partial or total) disability.90

Medical status: In Phase 8 major improvements in the ability to work based

on medical interventions are no longer anticipated by either the patient, medical professionals or others. A few patients may sign up for repeated heroic surgical procedures. Some live dependent on technical devices such as braces or TENS- devices (transcutaneous electrical nerve stimulation). Many patients are drug- dependent or suffer from other secondary psychiatric disorders including severe depression. A minority of patients receive interdisciplinary care in specialized pain clinics, some will be treated by alternative health care providers, and many will suffer silently. No data exist to describe the full personal and institutional disaster experienced by patients and care givers during this last phase.

Worker's compensation: In this phase worker's compensation claims are closed. Multiple medical reports and often litigation are conducted for a final decision about compensation. If the disability is accepted as work-related and if the

Classification Based on a Phase Model of Work-Disability

Contents

Introduction

Classification Based on a Phase Model of Work-Disability