Documents Silverstein, Barbara A. 10 results

"This paper presents a conceptual model for the pathogenesis of work-related musculoskeletal disorders. The model contains sets of cascading exposure, dose, capacity, and response variables, such that response at one level can act as dose at the next. Response to one or more doses can diminish or increase the capacity for responding to successive doses. The model is used as a framework for discussing the development of work-related muscle, tendon, and nerve disorders. It is intended as a beginning, to be modified to explain new findings as they become available. In research, it can help to identify areas needing additional data for the development and expression of work-related musculoskeletal disorders. Researchers can use it to design laboratory and field studies. In practice, it demonstrates the relationship between common exposure factors and different responses. This information can be used to evaluate and design jobs for the prevention of work-related musculoskeletal disorders."

The prevention of work-related musculoskeletal disorders has become a national priority in many countries. Increasingly, attempts are made to quantify those exposures that increase risk in order to set exposure limit values. This study used commonly employed field measurement methods and tools in order to perform an inter-method comparison between three primary methods of risk factor exposure assessment: self-report questionnaires, observational video analysis and direct measurement. Extreme posture duration, repetition, hand force (estimated from electromyography) and movement velocity were assessed for 18 subjects while performing each of three jobs processing tree seedlings. Results indicated that self-reports were the least precise assessment method, which consistently overestimated exposures for each of the measured risk factors. However, adjustment of the reports as psychophysical scales may increase agreement on a group level. Wrist flexion/extension duration and repetition were best measured by electrogoniometer. Electrogoniometric measures of wrist deviation duration and frequency were less precise than video analysis. Forearm rotation duration and repetition, grip force and velocity appeared to be best quantified by direct measurement as measured by electrogoniometer and electromyography (EMG) (as root-mean-square amplitude). The results highlight the fact that it is as important to consider and report estimated measurement error in order to reduce potential exposure misclassification in epidemiologic studies.

"Epidemiologic and experimental studies were reviewed to assess the role of postural factors, high handgrip and pinch forces, repetitive hand and wrist movements, external pressure, and vibration in the occurrence of carpal tunnel syndrome (CTS). Forceful repetitive work, vibration, and extreme wrist postures have been associated with CTS in several epidemiologic studies. Experimental studies have shown that certain forearm, wrist, and finger postures, even moderate hand loads and external pressure on the palm, can increase carpal tunnel pressure (CTP) at least temporarily to levels at which nerve viability is threatened. It is concluded that while more research is needed, there is sufficient information to suggest that reducing the duration, frequency or intensity of exposure to forceful repetitive work, extreme wrist postures and vibration is likely to result in a reduction of the incidence or severity of CTS in working populations."

"A two-page checklist for determining the presence of ergonomic risk factors associated with the development of upper extremity cumulative trauma disorders (e.g., repetitiveness, local mechanical contact stresses, forceful manual exertions, awkward postures, and hand tool usage) was developed and evaluated as part of a joint labour-management ergonomics intervention programme. This checklist was used by plant personnel at four work sites to assess the presence of upper extremity risk factors in 335 manufacturing and warehouse jobs. In addition, results generated by the checklist were compared to the results of ergonomic analyses performed by persons with advanced training (Masters degrees) in occupational ergonomics for a subset of 51 jobs. Most of the jobs included in the survey were found to have significant exposures to upper extremity risk factors. Awkward work postures were common, with 90% of the jobs requiring wrist deviations outside the neutral range-of-motion. The jobs were also highly repetitive and frequently required workers to exert high hand forces. Results generated by the checklist were generally in agreement with results generated by the ergonomic analysts; however, the checklist was found to be more sensitive in identifying the presence of risk factors. The checklist was found to be an effective rapid-screening instrument for identifying jobs that expose workers to potentially harmful ergonomic stresses. However, the checklist methodology did not include sufficient documentation of work methods to identify specific job attributes associated with these exposures."

Data sources for conducting surveillance of work related musculoskeletal disorders were evaluated. The data were obtained from four automotive facilities that were in the process of implementing ergonomic programs to reduce work related musculoskeletal disorders. Sources of data included workers' compensation records, sickness and accident insurance records, OSHA 200 logs, facility medical records, self administered symptoms questionnaires, professional interviews, and physical examinations. Hazard surveillance based on evaluation of job exposures to physical stressors was also considered. The highest rate of symptoms was obtained using university administered health interview data. Prevalence based on physical examination plus interview was similar to that obtained using self administered questionnaires. The lowest rate was obtained using facility medical records. Work related musculoskeletal disorder status on self administered questionnaires and on physical examination was associated with risk factor scores for different body areas. The authors conclude that symptoms questionnaires and checklist based hazard surveillance are reliable and reasonably sensitive data sources for identifying and tracking symptomatic workers and work related risk factors for musculoskeletal disorders.

"Objectives This study assessed the prevalence, incidence, and persistence of nontraumatic rotator cuff tendinitis and shoulder symptoms over a 1-year period in a working population and the predictive value of symptoms and physical findings.Methods A 1-year prospective study of 436 active workers was conducted at 12 different worksites. Detailed health interviews, psychosocial questionnaires, and physical examinations were conducted at baseline and again after 1 year, with shorter evaluations at 4 and 8 months. Individual observed exposure assessment of shoulder posture, arm–hand activity, and hand forces was conducted. Results The prevalence of rotator cuff tendinitis at baseline was 7.6% [95% confidence interval (95% CI 5.1–10.1%)] for the right and 4.8% (95% CI 3.0–7.0%) for the left, compared with shoulder symptoms of 18.6% (95% CI 14.9–22.3%) (right) and 11.2% (95% CI 8.2–14.2%) (left). The incidence of rotator cuff tendinitis was 5.5% (95% CI 2.8–6.8%) and 2.9% (95% CI 1.0–3.8%), respectively. Higher proportions of participants with current symptoms or physical findings at baseline became clinical cases after 1 year than those without symptoms or findings. The 1-year persistence of clinical case status was 31.3% (95% CI 26.9–35.7%) (right) and 31.6% (95% CI 27.2–36.0%) (left). There were significant differences at baseline between the asymptomatic participants and the clinical cases with respect to physical health on the 12-item Short-form Health Survey (P=0.0002), the perception of general health (P=0.0027), and the frequency of high hand force exposure (P=0.0177). Conclusions Considerable movement occurs between different stages of shoulder problems. Symptoms and physical findings alone appear to predict clinical case status within 1 year. Frequent follow-up is necessary to capture changes in health and exposure status in prospective studies."

"Methods Union administrative records identified 20,642 union carpenters who worked in Washington State from 1989 to 2003. The Department of Labor and Industries provided records of workers' compensation claims and associated medical care. Work-related back claims (n = 4,241) were identified by ANSI codes (back, trunk, or neck/back) or ICD-9 codes relevant to medical care consistent with a back injury. Cases (n = 738) were defined as back injury claims with >90 days of paid lost time; controls (n = 699) resulted in return to work within 30 days. Logistic regression models estimated odds ratios and 95% confidence intervals (OR, 95% CI) of delayed return to work (DRTW). Results Thirty percent of case claims and 8% of control claims were identified by an ICD-9 code. DRTW after back injury was associated with being female (2.7, 95% CI: 1.3-5.5), age 30-44 (1.2, 95% CI: 0.9-1.7) and age over 45 (1.6, 95% CI: 1.1-2.3), four or more years union experience (1.4, 95% CI: 1.1-1.8), previous paid time loss back claim (1.8, 95% CI: 1.3-2.5), and 30-day delay to medical care (3.6, 95% CI: 2.1, 6.1). Evidence of more acute trauma was also associated with DRTW. Conclusions Use of ICD-9 codes identified claims with multiple injuries that would otherwise not be captured by ANSI codes alone. Though carpenters of younger age and inexperience were at increased risk for a paid lost time back injury claim, older carpenters and more experienced workers, once injured, were more likely to have DRTW as were those who experienced acute events."

"This paper addresses the issue of quantifying forceful exertions of lifting, pushing/pulling, pinch and power griping with several commonly used methods (direct measurement, force-matching, ergonomist estimation based on observation and worker's self-report). The aims were to study differences of ergonomists in making decisions of collecting forceful exertion data, ability of the studied force quantification methods in detecting exposure differences between jobs, and relationships between measurements obtained by different methods. Seven hundred and thirty-three (733) subjects participated in the study, and 2482 forceful exertions were quantified with the selected force quantification methods. Results showed that the determination of whether a forceful exertion was considered important enough to be measured was very subjective. More objective criteria need to be developed. Although the different force quantification methods could detect exertion-level differences between different types of jobs, the sensitivity of detecting the difference varied. Direct measurement of lifting and pushing/pulling forces seems to be slightly more sensitive than ergonomists' estimates, and the force matching of grip forces may be more sensitive than workers' self-reports. Ergonomists estimations through observation seem to be a good alternative for measuring forceful exertions. Pearson correlation coefficients between force estimations obtained by the different methods were between 0.28 and 0.71. The degrees of the correlations between the different measurement methods varied. This indicates that the different methods might quantify different aspects of the forceful exertions. These methods may not necessarily be used interchangeably in job evaluation tools. Different weights and/or cut-points may need to be developed when different force quantification methods are used."

"The relationships between work organisational, biomechanical and psychosocial factors were studied using cross-sectional data from a pooled dataset of 1834 participants. The work organisational factors included: job rotation, overtime work, having second jobs and work pace. Task and job level biomechanical variables were obtained through sub-task data collected in the field or analysed in the laboratory. Psychosocial variables were collected based on responses to 10 questions. The results showed that job rotations had significant effects on all biomechanical and most psychosocial measures. Those with job rotations generally had higher job biomechanical stressors, and lower job satisfaction. Overtime work was associated with higher job biomechanical stressors, and possibly self-reported physical exhaustion. Those having second jobs reported getting along with co-workers well. Work pace had significant influences on all biomechanical stressors, but its impact on job biomechanical stressors and psychosocial effects are complicated.
PRACTITIONER SUMMARY:
The findings are based on a large number of subjects collected by three research teams in diverse US workplaces. Job rotation practices used in many workplaces may not be effective in reducing job biomechanical stressors for work-related musculoskeletal disorders. Overtime work is also associated with higher biomechanical stressors."