Biobehavioral mechanisms of work-related upper extremity disorders: a new agenda for research and practice

BACKGROUND: Epidemiological studies provide support for the role of organizational and individual psychosocial stressors in work-related upper extremity disorders (WRUEDs). Despite this evidence, the biological plausibility of a relationship between exposure to various psychosocial and work organizational stressors and WRUEDs remains unclear METHODS: The Georgetown Symposium on Biobehavioral Mechanisms of Work-Related Upper Extremity Disorders was held in Washington D.C. on November 6-7, 2000 to improve the understanding of potential biobehavioral mechanisms, identify future areas for research and discuss the implications of this body of knowledge for intervention. This meeting involved presentations and discussions by researchers and clinicians from a number of disciplines (epidemiology, occupational medicine, rheumatology, orthopedics, surgery, internal medicine, psychoneuroimmunology, occupational health psychology, behavioral medicine, psychophysiology and experimental and organizational psychology). RESULTS: The symposium generated several papers addressing the following topics: definitions and job stress models; epidemiological foundations; musculoskeletal and biomechanical models; central nervous system models of recurrent and persistent clinical pain; psychophysiology of work; and implications for intervention. These papers comprise this special issue. DISCUSSION: The present paper summarizes the various contributions to this special issue and provides direction for future research on potential biobehavioral pathways.     

Stress and work-related upper extremity disorders: implications for prevention and management

BACKGROUND: A causal link between stress and work-related musculoskeletal disorders of the upper extremities (WRUEDs) has been established, but there is less evidence for a beneficial effect of stress reduction interventions on WRUED symptoms and incidence. METHODS: Searches of Medline, Ergonomics Abstracts, and Psychlit from 1990 to 2001 identified studies that either targeted stress and measured WRUED outcomes, or described other interventions with both stress and WRUED outcomes. RESULTS: Workplace interventions, including discrete improvements in technology, work organization and ergonomics, and more comprehensive approaches can reduce levels of stress. In a few studies, these interventions have been associated with decreases in WRUED symptoms. Similar effects are noted in stress-related interventions targeting individuals before WRUEDs have appeared, and at several stages of these conditions. CONCLUSIONS: Health care providers can recognize stress-WRUED interactions through careful, directed inquiry. Both individual as well as workplace-targeted interventions, delivered in the primary care setting or workplace, may be helpful. Future research priorities include prospective studies of well-defined interventions, with ample measures of subject, intervention and workplace characteristics that can impact outcomes, and adequate follow-up to determine sustained effects.     

Psychosocial factors and the rehabilitation of patients with chronic work-related upper extremity disorders

This prospective cohort study investigated the effects of psychosocial factors on long-term employment outcome of a sample of chronic work-related upper-extremity pain disorder patients who had completed an interdisciplinary functional restoration program. Factors examined included the following: DSM-III-R Axis I and Axis II diagnoses, derived from the Structured Clinical Interview for DSM-III-R (SCID); history of childhood abuse experienced as elicited by the SCID; the Quantitated Pain Drawing, which evaluated perceived pain intensity; Million Visual Analog Scale, which measures perceived level of disability; and the Beck Depression Inventory, which assessed the level of depression. Results from univariate analyses demonstrated that return-to-work status 1 year following rehabilitation was predicted by the following psychosocial variables: The number of Axis I disorders, a past diagnosis of substance abuse, a past and/or current diagnosis of an anxiety disorder, a diagnosis of borderline personality disorder, a history of childhood abuse, self-report of depressed mood, and a moderate to high level of perceived disability. Additionally, age, race, length of disability, and prior surgical treatment predicted return-to-work rates. A multiple logistic regression further revealed that upper extremity patients who were older, Caucasian, had a current diagnosis of an anxiety disorder, and whose perception of their disability deteriorated from pre- to post-program were significantly less likely to return to work at one-year follow-up. Overall, the findings indicate that psychosocial variables influence the successful rehabilitation of patients with upper extremity disability, suggesting that these patients should be assessed and treated for psychosocial dysfunctions in conjunction with their rehabilitation so as to optimize favorable outcomes after treatment.     

Employer,physical therapist,and employee outcomes in the management of work-related upper extremity disorders

The purpose of this study was to investigate the relationship among employer, provider, and patient outcome measures and how they are related to clinical factors and other occupation-related factors. Data were obtained from a New England workplace physical therapy (PT) clinic. Successful outcomes were defined as remaining-on/returning-to preinjury job (employer); achieving PT goals (provider); and increases in the SF-36 scale scores (patient). Variation in outcomes was explored across injury regions (shoulder, elbow, wrist/hand), work categories, number of visits, and length of PT care. Employer and provider outcomes are moderately correlated (phi coefficient = 0.51). Subjects demonstrated significant improvements in the SF-36 physical functioning and bodily pain scores after physical therapy intervention. Patients with elbow disorders needed more PT care and did not improve in the SF-36 role physical domain compared to shoulder and wristgroups (p < 0.05). Our results describe the relationship between outcome measures from different perspectives and the influence from other contributing factors. The impact of workplace injury management and the selection of outcome measures warrant continued study.     

Shoulder Disorders Related to Work Organization and Other Occupational Factors among Supermarket Cashiers

Abstract

The study was designed to examine, in 210 supermarket cashiers, the cross-sectional relationships between shoulder disorders according to location and chronicity of pain as well as personal and occupational factors and store and workstation characteristics. The factors associated with shoulder disorders differed for the right and left sides. Age and psychological disorders were significant risk factors. Among occupational factors, duration of employment, job control, wage dependence on efficiency, exposure to cold, movements and postures such as stooping, working with arms above shoulder level and holding heavy loads in position, and using a laser scanner were associated with shoulder disorders, especially on the left. These results confirm the multi factorial origin of shoulder disorders, and show the importance of psychosocial work factors, movements and postures, and the laser scanner as occupational risk factors, and the need to consider right and left shoulder disorders in cashiers separately.     

Biomechanical models for the pathogenesis of specific distal upper extremity disorders

BACKGROUND: Knowledge of the pathogenesis of most disorders that occur in the distal upper extremity is generally lacking. The individual roles of postulated etiologic factors, such as biomechanical or psychosocial exposures, are poorly understood and their potential interactions even less so. This article proposes biomechanical or physiological models of pathogenesis for specific distal upper extremity disorders. METHODS: Tendon entrapment of the dorsal wrist compartments (tenosynovitis), peritendinitis, lateral epicondylitis, and carpal tunnel syndrome are common specific neuromusculoskeletal disorders of the upper extremities observed among workers. The normal anatomy and function of the targeted structures is considered the initial state; their pathology is considered the final state. Using biomechanical or physiological principles combined with clinical observations and experimental studies, pathways leading from the initial state to the final state are proposed. Each model defined a critical biomechanical or physiological attribute that was considered to best characterize 'dose.' Two temporal patterns of exposure (duration vs. repetition) were used to characterize 'dosage.' The roles of long-term exposure vs. unaccustomed work were mentioned, but not incorporated into the models. RESULTS: Compressive force transmitted to the extensor retinaculum was considered the critical factor in the model for tendon entrapment at the dorsal wrist compartments. Two models were proposed for lateral epicondylitis. One emphasized the role of eccentric exertions; the other emphasized contact pressure from the radial head. The model for peritendinitis relied on localized muscle fatigue. Seven plausible models were presented for carpal tunnel syndrome. CONCLUSIONS: It is possible to propose biologically plausible models of pathogenesis that are both coherent with current knowledge of tissue responses and consistent with clinical observations; however, more than one model was plausible for some conditions. Additional research is needed to determine which, if any, of the proposed models might be correct. Such models may be useful to health care providers and ergonomists in the context of primary, secondary, or tertiary prevention.     

Relationship between stress and pain in work-related upper extremity disorders: the hidden role of chronic multisymptom illnesses

BACKGROUND: Pain and fatigue are commonly associated with work-related upper extremity disorders. Occasionally these symptoms persist beyond a reasonable healing period. One potential explanation for prolonged symptom expression is the concurrent development of a stress-mediated illness or CMI (Chronic Multi-Symptom Illness). In such a scenario, the chronic regional pain and other symptoms that the individual is experiencing would be attributable to the CMI rather than to tissue damage or a biomechanical dysfunction of the upper-extremity. METHODS: This article critically reviews the case definitions of the new class of CMI disorders and evaluates the existing evidence supporting centrally mediated physiological changes (e.g., sensory hypervigilance, dysautonomia) that manifest as symptoms of pain and fatigue in some individuals experiencing chronic stressors. RESULTS: While explanations for prolonged pain and fatigue have historically focused on mechanisms involving peripheral pathology or psychiatric explanations, ample evidences support the role of altered Central Nervous System function in accounting for symptom manifestation in CMI. CONCLUSIONS: A model is presented that unites seemingly disparate findings across numerous investigations and provides a framework for understanding how genetics, triggering events, stressors, and early life events can affect CNS activity. Resultant symptom expression (e.g., pain and fatigue) from central dysregulation would be expected to occur in a subset of individuals in the population, including a subset of individuals with work-related upper extremity disorders. Thus when symptoms such as pain and fatigue persist beyond a reasonable period, consideration of CMI and associated assessment and interventions focused on central mechanisms may be worthwhile.     

Effects of work and rest on upper extremity signs and symptoms of workers performing repetitive tasks

The temporal relationship between work and signs and symptoms of upper extremity musculoskeletal disorders among workers at risk is relatively unexplored. The study focused on changes in upper extremity circumference, volume, sensory threshold, and reported symptoms after work and rest. All workers (N=50) performed a repetitive poultry processing task and had exhibited upper extremity signs and symptoms in baseline testing prior to this study. These workers manifested significantly increased upper extremity circumference following a period of rest, with circumferences decreasing during work. Upper extremity volume and reported swelling also decreased during work. Reports of tenderness were significantly greater after work than after rest, while reports of pain were greatest after a short rest interval. Results show that the signs and symptoms observed in these workers were manifestations of occupational cumulative trauma and that further study of the relationship between work and signs and symptoms is needed.     

Secondary prevention of work-related upper extremity disorders: recommendations from the annapolis conference

Introduction: Efforts to improve the secondary prevention of work-related upper extremity (WRUE) symptoms continue to present a challenge. As with many occupational musculoskeletal pain disorders no single, direct cause-effect relationship exists among specific exposures, pathologic processes, and symptoms. The field has yet to create truly effective and efficient interventions for these problems that are based on current epidemiological and clinical knowledge. Methods: A working conference was held in Annapolis, Maryland on September 23rd and 24th, 2005 with leaders in research and application related to upper extremity disorders to address this challenge. The intent of the meeting was to review “state of the art” evidence in epidemiology and intervention research in order to develop suggestions regarding next steps in intervention research and application. On day 2 a number of stakeholders were present to discuss what they perceived as the missing pieces in both epidemiological research and applied intervention research in order to generate more effective workplace interventions. Results: The papers in this series of the Journal of Occupational Rehabilitation indicate that scientifically sound progress has been made over the past decade in identifying ergonomic, workplace psychosocial, and individual factors in both the etiology and exacerbation of these symptoms/disorders. However, there is a gap between this knowledge and the development and practical implementation of comprehensive interventions for these problems. The conference also highlighted the paucity of economic analyses of the impact of these disorders as well as the economic study of the impact of intervention. Approaches for such evaluations were presented and are included in this special section of the journal. Conclusions: This series of papers and the summary of the invited group's discussions provided in this paper clearly emphasize the need for innovative ways to think about these problems and specific research topics that can help translate this knowledge into effective secondary prevention efforts.The opinions and assertions contained herein are the private views of the authors and not to be construed as being official or as reflecting the views of the Uniformed Services University of the Health Sciences or the Department of Defense.     

Innovative applications of epidemiology, evidenced based interventions and economic analyses of office related upper extremity disorders

In September 2005 a small working conference was held to generate potential next steps in the generation of innovative approaches to work related upper extremity symptoms and disorders among those working in office environments. This special section of the Journal includes papers written by the presenters and their collaborators. These papers provide “state of the art” summaries of research in the areas of ergonomics, biobehavioral factors and interventions, economics and integrative interventions at the workplace. Invited speakers and participants from various stakeholder groups spent a second day discussing the implications of the research presented on day one for improving the understanding and management of these disorders. Practical considerations for generating new approaches and their implementation were also discussed.This conference was supported by the Office Ergonomics Research Committee.The Annapolis Conference, Annapolis, Maryland, September 23–24th, 2005     

Occupational upper extremity conditions: a detailed analysis of work-related outcomes

While work-related upper extremity conditions (WRUECs) cause almost 25% of lost time cases in the US, little is known about their long-term occupational consequences. A self-report survey was mailed to New Hampshire workers reporting a WRUEC one year prior to the study. Of the 72 (52%) valid respondents, 60% had lost 1 week of work and 90% had returned to work. Almost 70% reported acute injury onset, and 26% had experienced a recurrence of their WRUEC. Both gradual-onset injuries and recurrences had worse outcomes. Recurrence was related to shorter job tenure, lower job satisfaction, and less satisfaction with medical care and insurer responses. Results imply that a single measure is insufficient to assess occupational outcomes subsequent to a WRUEC. The importance of secondary prevention was highlighted. There is a need for focus on gradual-onset injuries, as well as those acute-onset injuries with risk for recurrence.     

Individual and combined impacts of biomechanical and work organization factors in work-related musculoskeletal symptoms

BACKGROUND: Investigations of work-related low back (LB) and upper extremity (UE) disorders have increasingly utilized multivariable models that include biomechanical/physical and work organization factors. However, the nature of any interactive effects is not well understood. METHODS: Using questionnaires, high and low exposure groups for biomechanical/physical factors, cognitive demands, cognitive processing, interpersonal demands, participatory management, skill discretion, and time pressure for 289 individuals (U.S. Marines) were identified. Musculoskeletal symptom status was also determined by questionnaire. Individual and biomechanical-psychosocial combinations were examined in adjusted multivariable logistic regression analyses. RESULTS: Time pressure was associated with both LB and UE symptoms (odds ratio(s) (OR) range = 2.13-3.09), while higher biomechanical exposures were risk factors for LB symptoms (OR = 2.07; 95% confidence intervals (CI): 1.00-4.35) and concurrent LB and UE symptoms (OR = 2.80; CI: 1.35-5.83). Greater risks for concurrent LB and UE symptoms were indicated for combinations involving higher biomechanical exposure and: time pressure (OR = 2.21; CI: 1.19-4.10); cognitive demands (OR = 2.25; CI: 1.23-4.09); cognitive processing (OR = 2.08; CI: 1.16-3.75); interpersonal demands (OR = 2.44; CI: 1.35-4.41); participatory management (OR = 2.50; CI: 1.30-4.81). Results did not suggest any interaction between biomechanical and work organization factors. CONCLUSIONS: While no synergism was indicated, the present findings emphasize the need to consider both biomechanical factors and specific work organization factors, particularly time pressure, in reducing musculoskeletal-related morbidity.     

Occupational exposures associated with work-related asthma and work-related wheezing among U.S. workers

BACKGROUND: National estimates of occupational asthma (OA) in the United States are sparse. METHODS: Using data from the Third National Health and Nutrition Examination Survey (NHANES III) 1988-1994, we analyzed associations between occupation and work-related asthma and work-related wheezing among U.S. workers. RESULTS: This study identified several occupations that were at risk of developing work-related asthma and/or wheezing, with cleaners and equipment cleaners showing the highest risks. Other major occupations identified were farm and agriculture; entertainment; protective services; construction; mechanics and repairers; textile; fabricators and assemblers; other transportation and material moving occupations; freight, stock, and material movers; and motor vehicle operators. The population attributable risks for work-related asthma and work-related wheezing were 26% and 27%, respectively. CONCLUSIONS: This study adds evidence to the literature that identifies work-related asthma as an important public health problem. Several occupations are targeted for additional evaluation and study. Of particular interest are cleaners, which are being increasingly reported as a risk group for asthma. Future intervention strategies need to be developed for effective control and prevention of asthma in the workplace.     

Multicomponent Intervention for Work-Related Upper Extremity Disorders

Although several multidimensional models have emerged to explain the development, exacerbation and maintenance of work-related upper extremity disorders and disability, there is a paucity of data on the application of these models for the development of worksite-based prevention and management programs. Sign language interpreting is an occupation associated with increased risk for upper extremity symptoms. Ergonomic, work organization, work style, and work-related and individual psychosocial factors have been demonstrated to play a role in the exacerbation of symptoms and lost time in this group. Therefore, it was hypothesized that an intervention directed at reducing the impact of these factors would be associated with reductions in the number of upper extremity cases/year and associated lost time and health care costs in a group of full-time sign language interpreters. Subjects included 53 symptomatic and asymptomatic interpreters working at the National Technical Institute for the Deaf. The intervention (eleven 1.5-hr group sessions) was designed to 1) reduce musculoskeletal overexertion by reducing workload and biomechanical strain, while increasing flexibility and endurance through tailored exercise and preinterpreting warm ups, 2) improve the ability of workers to manage job stress and musculoskeletal pain, 3) reduce biomechanical exposure through work organization and work style changes, 4) alter organizational sources of stress by improving supervisor's managerial skills to address work related upper extremity problems and provide increased supervisor support, and 5) educate workers and supervisors regarding the optimal utilization of health care resources, given the present state of the art in terms of clinical evaluation and management. Results indicated a 69% reduction in the number of cases reporting upper extremity problems in the 3 years following the intervention. Indemnity costs were reduced by 64% and were maintained over the next 2 years. Health care costs followed a similar, although smaller magnitude, change. Despite this reduction, a partial rebound in all outcome measures was observed in Year 3 postintervention. This rebound followed a progressive increase in workload over the 3-year follow-up period.     

Multilevel nerve compression and muscle imbalance in work-related neuromuscular disorders

BACKGROUND: Work-related upper limb disorders have come under increasing scrutiny and become a frustrating problem. METHODS: A unifying hypothesis to explain the multiplicity of symptoms with work related neuromuscular disorders is outlined. This multifactorial problem includes physical, individual, and psychosocial factors. Abnormal postures and positions may compress nerves or may alter muscle length resulting in secondary compressive forces on nerves or in muscle imbalances. Evaluation should identify all nerve compression levels and muscle imbalance in the arm and cervicoscapular region. Management must include patient education, postural correction, and an exercise program to address the multiple nerve compression levels and muscle imbalance. RESULTS AND CONCLUSIONS: The etiology of work related neuromusculoskeletal disorders is multifactorial and successful management must address all contributing factors. Appropriate conservative management will relieve symptoms in most patients. Surgery should be reserved for those few patients with evidence of a specific diagnosis who have failed conservative management.     

Use of a prevention index to identify industries at high risk for work-related musculoskeletal disorders of the neck, back, and upper extremity in Washington state, 1990-1998

BACKGROUND: The prevention of work-related musculoskeletal disorders such as carpal tunnel syndrome and low back disorders has been a focus of international prevention efforts including regulation. This study examines workers compensation claims in Washington State to provide baseline data from which to assess the need and the effects of prevention activities. METHODS: Washington State Fund workers compensation claims for general and selected specific hand/wrist, elbow, shoulder, and back disorders in 1990-1998 as well as general self-insured compensable (four or more lost workdays) claims data were examined. Payroll hours were used to calculate claims incidence rates per 10,000 full-time equivalent employees (FTEs). We created a prevention index (PI) to rank industries by averaging the ranks of their number of claims and their claims incidence rate. The focus was on non-traumatic soft tissue musculoskeletal disorders (NTST-MSDs). RESULTS: Between 1990-1998, there were 392,925 State Fund accepted claims for NTST-MSDs of the neck, back, and upper extremity resulting in $2.6 billion in direct costs and 20.5 million lost workdays. The average claims incidence rate (CIR) was 355 NTST-MSDs per 10,000 FTEs. The NTST-MSD CIR decreased significantly less than that for all other claims (P = 0.05) but the CIR for upper extremity NTST-MSDs did not significantly decrease over the study period. There were no significant changes in the CIRs for sciatica (4.9 per 10,000 FTEs) and rotator cuff syndrome (15.3 per 10,000 FTEs), whereas the CIR for epicondylitis (10.6 per 10,000 FTEs) increased and for carpal tunnel syndrome (24.5 per 10,000 FTEs) decreased significantly over the study period. Based on the prevention index, the top five industries for combined State Fund and Self-Insured Compensable NTST-MSDs were Trucking and Courier Services (SIC 421), Nursing Homes (SIC 805), Masonry (SIC 174), Air Transportation (SIC 451), and Residential Construction (SIC 152). Using Washington Industrial Classes (WIC), temporary workers in assembly and administrative services were also high on the prevention index. CONCLUSIONS: NTST-MSDs continue to be a large and costly problem in Washington State. While the incidence rates for some NTST-MSDs are decreasing, the overall rate is not decreasing as fast as the rate for all other claims. In some cases, the rate is stable (sciatica, rotator cuff syndrome) or increasing (epicondylitis). Heavy manual handling and repetitive work characterize the industries with the highest risk.     

The impact of work-related musculoskeletal disorders on workers' caregiving activities

BACKGROUND: The purpose of the study was to describe and quantify the impact of work-related musculoskeletal disorders on workers' caregiving activities. METHODS: A cross-sectional study was conducted in which a telephone survey was administered to 187 lost-time workers' compensation claimants from Ontario, of whom 49.2% were women. Forty-eight percent of the injured workers were providing unpaid care prior to the injury. RESULTS: Injured workers providing caregiving reported an average reduction in time spent in caregiving activities of 5.5 hr/week, 8 months post-injury. A Sex X Return-to-work status ANCOVA was conducted with difference in caregiving hours as the dependent variable, and with the following covariates: Mean number of caregiving hours, comorbidities, site of injury, and education. Independent of weekly hours of caregiving, decreases in caregiving hours were significantly higher if the worker was a woman or had not returned to work. CONCLUSIONS: Work-related musculoskeletal disorders have a significant impact on workers' time spent in unpaid caregiving activities, an example of the social consequences of occupational injuries. Occupational and caregiving roles are limited by work-related disorders in a parallel fashion.     

Prognosis of nonspecific work-related musculoskeletal disorders of the neck and upper extremity

Reviews of work-related musculoskeletal disorders (WMD) of the neck and upper extremity have typically supplied little information on prognosis. This paper reports on the methods and results of a systematic search for evidence on clinical course and prognosis of nonspecific WMD, i.e., those without specific clinical diagnoses. Articles were deemed relevant if they provided primary data on current or former worker cases of WMD followed over time. WMD status had to be based on clinical evaluations. The 13 studies which met these criteria were evaluated using clinical epidemiological criteria for validity of prognostic studies. None of the studies was sufficiently strong across the criteria to provide more than weaker evidence on prognosis. Prognostic factors with promise include duration of symptoms and workplace demands. In order to improve the evidence on prognosis of WMD, we recommend closer attention to the following: clear operational definition of cases; documentation of prognostic factors including duration of symptoms and severity at baseline; incorporation of multiple follow-up assessments; inclusion of a range of outcomes; and analysis using stratified or multivariate methods. © 1996 Wiley-Liss, Inc.     

Validity and reliability of a new device to simulate upper extremity work demands

The device validity, intra-test reliability, and test-retest reliability of the LIDO WorkSET^TM (Loredan Biomedical, West Sacramento, California) was studied. Subjects were 30 healthy incumbent workers at a manufacturing and warehousing facility. The results of this study demonstrate a very high degree of device validity in terms of torque measurements, power, and work. In addition, the test protocols were found to be reliable on an intra-test and inter-test basis. Finally, inter-test comparisons were found to be stable over time.