Variability and misclassification of worker estimated hand force

Ergonomic studies often use worker estimated hand force reproduced on a dynamometer to quantify force exposures but this method has not been well-studied in real work settings. This study evaluated the validity of worker estimates of hand force in a field study and determined the misclassification of worker estimated hand force exposures compared to directly measured forces. Eight experienced sheet metal assemblers completed ¼-inch diameter fastener installations using 6 different pneumatic tools. Grip forces were recorded by a pressure mat and were compared to worker estimated forces demonstrated on a dynamometer. Directly measured and worker estimated readings showed moderate correlations (0.53-0.67) for four installation tools and fair to moderate for two tools. The coefficient for variation of force estimates was 65% within repeated subject trials and 78% between averaged subject trials but 69% between subject trials during actual tool installations. Misclassification of worker estimated exposures varied by two cut-points: 29% using 4.0 kg and 49% using 6.0 kg. The force match procedure may provide adequate differentiation of high and low exposures in some settings, but is likely to result in substantial misclassification in other settings.

Diagnostic strategies using physical examination are minimally useful in defining carpal tunnel syndrome in population-based research studies

OBJECTIVE

We evaluated the utility of physical examination manoeuvres in the prediction of carpal tunnel syndrome (CTS) in a population-based research study.

METHODS

We studied a cohort of 1108 newly employed workers in several industries. Each worker completed a symptom questionnaire, a structured physical examination and nerve conduction study. For each hand, our CTS case definition required both median nerve conduction abnormality and symptoms classified as "classic" or "probable" on a hand diagram. We calculated the positive predictive values and likelihood ratios for physical examination manoeuvres in subjects with and without symptoms.

RESULTS

The prevalence of CTS in our cohort was 1.2% for the right hand and 1.0% for the left hand. The likelihood ratios of a positive test for physical provocative tests ranged from 2.0 to 3.3, and those of a negative test from 0.3 to 0.9. The post-test probability of positive testing was <50% for all strategies tested.

CONCLUSION

Our study found that physical examination, alone or in combination with symptoms, was not predictive of CTS in a working population. We suggest using specific symptoms as a first-level screening tool, and nerve conduction study as a confirmatory test, as a case definition strategy in research settings.

Do workers with self-reported symptoms have an elevated risk of developing upper extremity musculoskeletal disorders three years later?

OBJECTIVES

Few prospective studies have evaluated outcomes of workers with self-reported symptoms of upper extremity musculoskeletal disorders (UEMSD). The objective was to study the three-year outcomes of workers with self-reported symptoms, with or without a positive physical examination.

METHODS

In 1993-4, 598 subjects highly exposed to repetitive work filled out a Nordic-style questionnaire. They underwent a standardised physical examination at that time and again in 1996-7 by the same occupational physician. The three-year outcomes (based on physical examination) of workers with a self-administered questionnaire positive at baseline for UEMSD, with or without a positive physical examination, were studied.

RESULTS

The three-year incidence rate was 44.1%; one third of these incident cases had self-reported symptoms in 1993-4. Workers with a positive questionnaire had a significantly higher risk of UEMSD at physical examination three years later (80.1% UEMSD cases with positive questionnaires n = 354, vs 44.2% cases without positive questionnaires n = 69, p<0.001). Moreover, workers with positive questionnaires but without UEMSD diagnosed in 1993-4 (n = 177) also had a significantly higher risk of UEMSD at physical examination three years later (60.5% cases with positive questionnaires n = 26, vs 38.8% cases without positive questionnaires n = 52, p = 0.01). Results were similar when gender and age were taken into account.

CONCLUSION

Workers highly exposed to repetitive movements have a high risk of developing UEMSD and should be followed closely in surveillance programmes. Workers with self-reported symptoms without UEMSD diagnosed in physical examination represented only one third of new cases three years later. However, their risk of developing UEMSD was significantly increased, compared with those without symptoms.

Why are manual workers at high risk of upper limb disorders? The role of physical work factors in a random sample of workers in France (the Pays de la Loire study)

OBJECTIVE

To investigate the reasons for the excess risk of upper limb musculoskeletal disorders among manual workers compared with other workers in a random sample of 2656 French men and women (20-59 years old) participating in a study on the prevalence of work related upper limb disorders conducted by France's National Institute of Health Surveillance.

METHODS

Prevalence ratios (PR) of physician-diagnosed musculoskeletal disorders of the shoulder, elbow, wrist, and hand (any of six leading disorders, rotator cuff syndrome, carpal tunnel syndrome) in manual versus non-manual workers were calculated using Cox regression models with a constant time of follow up and robust variance.

RESULTS

11.3% of men and 15.1% of women were diagnosed with an upper limb disorder. The risk was especially high in manual workers (PRs: 1.40 to 2.10). Physical work factors accounted for over 50% of occupational disparities overall, 62% (men) to 67% (women) for rotator cuff syndrome, and 96% (women) for carpal tunnel syndrome. The authors calculated that under lower levels of physical work exposures, up to 31% of cases among manual workers could have been prevented.

CONCLUSIONS

In working men and women, upper limb musculoskeletal disorders are frequent. Physical work exposures, such as repetitive and forceful movements, are an important source of risk and in particular account for a large proportion of excess morbidity among manual workers.

Physical activity, psychological complaints, and occupational health

Commentary on the paper by Bernaards et al (see page 10)

Prevalence of parkinsonism and relationship to exposure in a large sample of Alabama welders

OBJECTIVE

To estimate the prevalence of parkinsonism in welders in Alabama and to compare this prevalence with that in a general population sample.

METHODS

The authors screened 1,423 welders from Alabama who were referred for medical-legal evaluation for Parkinson disease (PD). Standardized videotaped assessments using the Unified Parkinson's Disease Rating Scale motor subsection 3 (UPDRS3) were obtained. Patients provided information regarding exposure to welding fumes and job titles. Job titles were matched with Department of Labor Standard Occupational Codes (SOCs). Diagnoses were assigned based on quantitative criteria for the diagnosis of PD using two thresholds for diagnosis. With use of the number of active welders in this screening with parkinsonism as the numerator and the age-adjusted number of welders in each SOC as the denominator, the prevalence of parkinsonism in Alabama welders was estimated using conservative assumptions and compared with general population data from Copiah County, MS.

RESULTS

With use of conservative and liberal case definitions of parkinsonism, the estimated prevalence of parkinsonism among active male welders age 40 to 69 statewide was 977 to 1,336 cases/100,000 population. The prevalence of parkinsonism was higher among welders vs age-standardized data for the general population (prevalence ratio = 10.19, 95% CI 4.43 to 23.43).

CONCLUSION

The estimated prevalence of parkinsonism was higher within a sample of male Alabama welders vs the general population of male residents of Copiah County, MS.

Use of mechanical patient lifts decreased musculoskeletal symptoms and injuries among health care workers

OBJECTIVE

To evaluate the effectiveness of mechanical patient lifts in reducing musculoskeletal symptoms, injuries, lost workday injuries, and workers' compensation costs in workers at a community hospital.

DESIGN

Pre-post intervention study.

SETTING

Three nursing units of a small community hospital. Patients or

SUBJECTS

Nursing personnel.

INTERVENTIONS

Mechanical patient lifts were made available and nursing staff trained in their use between August 2000 and January 2001.

MAIN OUTCOME MEASURES

Workers completed symptom surveys at baseline and six months after lift training. Pre-intervention and post-intervention rates of injuries and lost workday injuries using Occupational Safety and Health Administration logs of the three study units, from the period July 1999 through March 2003 were analyzed. Injuries potentially related to lifting patients were included in the analyses. Using workers' compensation data from the same time period, the compensation paid ($ per full time equivalent [FTE]) due to injuries during the pre-intervention and post-intervention period was calculated.

RESULTS

Sixty one staff members were surveyed pre-intervention; 36 (59%) completed follow up surveys. Statistically significant improvements in musculoskeletal comfort (p<0.05) were reported for all body parts, including shoulders, lower back, and knees. Injury rates decreased post-intervention, with a relative risk (RR) of 0.37 (95% confidence interval (CI) 0.16 to 0.88); decreased injury rates persisted after adjustment for temporal trends in injury rates on non-intervention units of the study hospital (RR = 0.50, 95% CI 0.20 to 1.26). Adjusted lost day injury rates also decreased (RR = 0.35, 95% CI 0.10 to 1.16). Annual workers' compensation costs averaged $484 per FTE pre-intervention and $151 per FTE post-intervention.

CONCLUSION

Reductions were observed in injury rates, lost workday injury rates, workers' compensation costs, and musculoskeletal symptoms after deployment of mechanical patient lifts. Strengths of this study include the community hospital setting and the inclusion of a variety of different outcomes. Limitations include the pre-post study design and the small sample size.

An evaluation of a "best practices" musculoskeletal injury prevention program in nursing homes

OBJECTIVE

To conduct an intervention trial of a "best practices" musculoskeletal injury prevention program designed to safely lift physically dependent nursing home residents.

DESIGN

A pre-post intervention trial and cost benefit analysis at six nursing homes from January 1995 through December 2000. The intervention was established in January 1998 and injury rates, injury related costs and benefits, and severity are compared for 36 months pre-intervention and 36 months post-intervention.

PARTICIPANTS

A dynamic cohort of all nursing staff (n = 1728) in six nursing homes during a six year study period.

INTERVENTION

"Best practices" musculoskeletal injury prevention program consisting of mechanical lifts and repositioning aids, a zero lift policy, and employee training on lift usage.

MAIN OUTCOME MEASURES

Injury incidence rates, workers' compensation costs, lost work day injury rates, restricted work day rates, and resident assaults on caregivers, annually from January 1995 through December 2000.

RESULTS

There was a significant reduction in resident handling injury incidence, workers' compensation costs, and lost workday injuries after the intervention. Adjusted rate ratios were 0.39 (95% confidence interval (CI) 0.29 to 0.55) for workers' compensation claims, 0.54 (95% CI 0.40 to 0.73) for Occupational Safety and Health Administration (OSHA) 200 logs, and 0.65 (95% CI 0.50 to 0.86) for first reports of employee injury. The initial investment of $158 556 for lifting equipment and worker training was recovered in less than three years based on post-intervention savings of $55 000 annually in workers' compensation costs. The rate of post-intervention assaults on caregivers during resident transfers was down 72%, 50%, and 30% based on workers' compensation, OSHA, and first reports of injury data, respectively.

CONCLUSIONS

The "best practices" prevention program significantly reduced injuries for full time and part time nurses in all age groups, all lengths of experience in all study sites.

Reduction in injury rates in nursing personnel through introduction of mechanical lifts in the workplace

BACKGROUND

Health care workers incur frequent injuries resulting from patient transfer and handling tasks. Few studies have evaluated the effectiveness of mechanical lifts in preventing injuries and time loss due to these injuries.

METHODS

We examined injury and lost workday rates before and after the introduction of mechanical lifts in acute care hospitals and long-term care (LTC) facilities, and surveyed workers regarding lift use.

RESULTS

The post-intervention period showed decreased rates of musculoskeletal injuries (RR = 0.82, 95% CI: 0.68-1.00), lost workday injuries (RR = 0.56, 95% CI: 0.41-0.78), and total lost days due to injury (RR = 0.42). Larger reductions were seen in LTC facilities than in hospitals. Self-reported frequency of lift use by registered nurses and by nursing aides were higher in the LTC facilities than in acute care hospitals. Observed reductions in injury and lost day injury rates were greater on nursing units that reported greater use of the lifts.

CONCLUSIONS

Implementation of patient lifts can be effective in reducing occupational musculoskeletal injuries to nursing personnel in both LTC and acute care settings. Strategies to facilitate greater use of mechanical lifting devices should be explored, as further reductions in injuries may be possible with increased use.

Retrograde versus antegrade nailing of femoral shaft fractures

OBJECTIVES

To compare union rates and complications of retrograde intramedullary nailing of femoral shaft fractures with those of antegrade intramedullary nailing.

DESIGN

Retrospective.

SETTING

Level I trauma center.

PATIENTS

Two hundred eighty-three consecutive adult patients with 293 fractures of the femoral shaft who underwent stabilization with antegrade or retrograde inserted femoral nails were studied. There were 140 retrograde nails and 153 antegrade nails. Twelve fractures in twelve patients were excluded (three in patients who died early in the postoperative period, three in patients because of early amputation, four in patients who were paraplegic, and two in patients who fractured through abnormal bone owing to metastatic carcinoma), leaving 134 fractures treated with retrograde nails and 147 treated with antegrade nails. One hundred four femurs treated with retrograde nails (Group R) and ninety-four femurs treated with antegrade nails (Group A) had sufficient follow-up and served as the two study groups. The average clinical follow-up was twenty-three months (range 6 to 66 months) for Group R and twenty-three months (range 5 to 64 months) for Group A. Both groups were comparable with regard to age, gender, number of open fractures, degree of comminution, mode of interlocking (i.e., static or dynamic), and nail diameter (p > 0.05).

INTERVENTION

Retrograde intramedullary nails were inserted through the intercondylar notch of the knee, and antegrade nails were inserted through the pirformis fossa using standard techniques.

MAIN OUTCOME MEASURES

Union, delayed union, nonunion, malunion, and complication rates.

RESULTS

After the index procedure there were no significant differences in healing or incidence of malunion between Group R and Group A (p > 0.05). Healing after the index procedure occurred in ninety-one (88 percent) of the femurs in Group R and in eighty-four (89 percent) of the femurs in Group A. In Group R, there were seven delayed unions (7 percent) and six nonunions (6 percent). In Group A, there were four delayed unions (4 percent) and six nonunions (6 percent). Healing ultimately occurred in 100 (96 percent) femurs from Group R and in ninety-three (99 percent) femurs from Group A. In Group R, there were eleven malunions (11 percent), and in Group A, there were twelve malunions (13 percent). When patients with ipsilateral knee injuries were excluded, the incidence of knee pain was significantly greater for Group R patients (36 percent) than for Group A patients (9 percent) (p < 0.001). When patients with ipsilateral hip injuries were excluded, the incidence of hip pain was significantly greater for Group A patients (10 percent) than for Group R patients (4 percent) (p < 0.05).

CONCLUSIONS

Retrograde and antegrade nailing techniques provided similar results in union and malunion rates. There were more complications related to the knee after retrograde nailing and more complications related to the hip after antegrade nailing.

Angular malalignment after intramedullary nailing of femoral shaft fractures

OBJECTIVES

To determine factors associated with angular malalignment of femoral shaft fractures treated with intramedullary nails and to determine differences in the incidence of angular malalignment based on fracture location, fracture comminution, and method of treatment (i.e., antegrade or retrograde).

DESIGN

Retrospective.

SETTING

Level I trauma center.

PATIENTS

Three hundred sixty patients with 374 femoral shaft fractures were identified from a prospectively obtained orthopaedic trauma database. Complete sets of immediate postoperative anteroposterior and lateral radiographs were available for 355 (95 percent) of the 374 fractures.

INTERVENTION

Patients were treated with antegrade (183 cases) or retrograde (174 cases) intramedullary femoral nailing.

MAIN OUTCOME MEASURE

Goniometric measurements were made on all immediate postoperative radiographs to determine the coronal plane and sagittal plane angular alignments. A multiple linear regression statistical analysis was used to determine factors associated with increasing angular malalignment. The incidence of malalignment was determined using more than 5 degrees of deformity in any plane as the definition of malalignment.

RESULTS

Proximal fracture location, distal fracture location, and unstable fracture pattern were associated with increasing fracture angulation (p < 0.001). Fracture location in the middle third, stable fracture pattern, method of treatment (i.e., antegrade or retrograde), and nail diameter were not associated with increasing fracture angulation (p > 0.05). The incidence of malalignment was 9 percent for the entire group of patients, 30 percent when the fracture was of the proximal third of the femoral shaft, 2 percent when the fracture was of the middle third, and 10 percent when the fracture was of the distal third. The incidence of malreduction was 7 percent for patients with stable fracture patterns and 12 percent for those with unstable fracture patterns.

CONCLUSIONS

Patients with fractures of the proximal third of the femoral shaft treated with intramedullary nails are at highest risk for malalignment. Proximal fracture location, distal fracture location, and unstable fracture pattern are associated with increasing fracture angulation.

Use of a questionnaire to improve occupational and environmental history taking in primary care physicians

New patient charts were reviewed before and after the introduction of a self-administered questionnaire, designed to elicit occupational and environmental (OE) information from patients. The Occupational Health Risk Assessment questionnaire (OHRA) was expected to prompt primary care physicians to make further inquiries into OE health issues. Chart reviews determined the amount and type of information detailed in the primary care physicians' notes. Twenty-three percent of completed OHRAs indicated a job-related health problem. Despite a high prevalence of self-reported work-related symptoms and exposures, the mean number of notations regarding OE exposures was less than one item per patient chart. A comparison of mean OE notations per chart before versus after introduction of the OHRA indicated a decline in notations after introduction of the OHRA (1.03 vs 0.72, P = 0.02). We detail the type of OE issues that patients presented to a primary care practice and the resulting information contained in primary care providers' notes. Suggestions are made to improve a self-administered patient questionnaire to better diagnose, prioritize, and formulate treatment plans related to OE issues.

Compliance with universal precautions among emergency department personnel caring for trauma patients

STUDY OBJECTIVE

Emergency department personnel are at high risk of occupational infection with bloodborne pathogens. The objective of this study was to observe and analyze the use of barrier precautions among ED personnel caring for trauma patients.

METHODS

This observational study used videotapes of trauma cases seen at an urban Level I trauma center. Study participants were ED and trauma team personnel. Trained observers scored breaks in the use of barrier precautions during the first 15 minutes of 88 videotaped Level I trauma cases. "Major" breaks were scored when ED personnel performed invasive procedures without gloves, mask, gown, and adequate eye protection. "Minor" breaks were scored when ED personnel were adjacent to a trauma patient (within 1 m) without wearing these items.

RESULTS

We observed 1 or more major breaks in 33.6% of 304 invasive procedures. The most common major break was failure to wear a mask (32.2% of procedures), followed by inadequate eyewear (22.2%), no gown (5.6%), and no gloves (3.0%). We observed minor breaks during 55.5% of 752 patient encounters. Large and statistically significant variations were seen in use rates of barrier precautions among different groups of personnel; surgery residents were most likely to use precautions, whereas attending surgeons were least likely.

CONCLUSION

Compliance with universal precautions is poor in this high-risk clinical setting. These data provide a baseline for measuring the effectiveness of interventions to improve compliance. Videotaped observations are a novel and effective tool in this setting.

Consensus criteria for the classification of carpal tunnel syndrome in epidemiologic studies

Criteria for the classification of carpal tunnel syndrome for use in epidemiologic studies were developed by means of a consensus process. Twelve medical researchers with experience in conducting epidemiologic studies of carpal tunnel syndrome participated in the process. The group reached agreement on several conceptual issues. First, there is no perfect gold standard for carpal tunnel syndrome. The combination of electrodiagnostic study findings and symptom characteristics will provide the most accurate information for classification of carpal tunnel syndrome. Second, use of only electrodiagnostic study findings is not recommended. Finally, in the absence of electrodiagnostic studies, specific combinations of symptom characteristics and physical examination findings may be useful in some settings but are likely to result in greater misclassification of disease status.

Evaluation of selective wrist arthrography of contralateral asymptomatic wrists for symmetric ligamentous defects

OBJECTIVE

The objective of this investigation was to study the role of selective wrist arthrography of the asymptomatic wrists of patients with unilateral wrist pain and the efficacy of three-compartment and selective-compartment injections of contrast medium into the asymptomatic wrist in demonstrating symmetric and asymmetric intercarpal ligament and triangular fibrocartilage communicating defects.

SUBJECTS AND METHODS

Wrist arthrography with bilateral three-compartment injections was performed for 62 patients with unilateral wrist pain. The numbers of bilateral intercarpal ligament and triangular fibrocartilage communicating defects were recorded. The results obtained with three-compartment injections in each wrist of these patients were compared with those obtained with single-compartment injections.

RESULTS

Bilateral three-compartment injections identified 110 communicating defects (59 in the symptomatic and 51 in the asymptomatic wrists). Midcarpal injections showed all 36 scapholunate and lunatotriquetral ligament defects that were also shown by three-compartment injections in asymptomatic wrists. However, only 26 (72%) of these 36 ligament defects were shown by radiocarpal injections. No single-compartment injection showed all triangular fibrocartilage defects that were shown by three-compartment injections. Ten bilateral symmetric triangular fibrocartilage communicating defects were shown by three-compartment injections. All 10 triangular fibrocartilage communicating defects in asymptomatic wrists were shown by radiocarpal injections. However, only five of the 10 triangular fibrocartilage communicating defects in asymptomatic wrists were shown by injection of the distal radioulnar joints.

CONCLUSION

Selective midcarpal injection of an asymptomatic wrist showed all matching defects in that wrist when only intercarpal ligament defects were found in the symptomatic wrist. Similarly, selective radiocarpal injection of an asymptomatic wrist showed all matching defects of the triangular fibrocartilage in that wrist. In either situation, routine injection of all three compartments of the asymptomatic wrist should not be necessary.

Increased risk of esophageal cancer among workers exposed to combustion products

Alcohol and tobacco habits have been identified as strong risk factors for esophageal cancer. Increased risks of esophageal cancer have also been reported to be associated with occupational exposure to asbestos and various metals, among vulcanization workers, asphalt workers, and workers in the petrochemical industry. Mortality and cancer incidence were investigated in a series of studies of workers exposed to combustion by-products, i.e., chimney sweeps, waste incinerator workers, gas workers, and bus garage workers exposed to diesel exhausts. The SMRs for esophageal cancer ranged from 150-386 in these cohorts, and a combined SMR of 289 (95% C.I. 174-452) was obtained. Available data on smoking habits and indirect indicators of alcohol consumption show that the excess cannot be attributed solely to these factors. It seems likely that occupational exposure to combustion products is associated with an increased risk of esophageal cancer.

Psychiatric diagnoses and perceived health problems in a sample of working Swedes treated with psychoactive medications

Findings of formal and subjective mental health problems among Swedish employees are presented as well as reviews of current Swedish policies on substance abuse and drug screening in the workplace. The focus is on the potential violation of medical confidentiality for employees with legitimate psychoactive drug medications and the lack of evidence linking the detection of various substances with impaired work performance. Data are drawn from a study of a sample of working Swedes, which revealed that approximately 3% reported taking psychoactive medications regularly. This was correlated with increases in long-term sick leave, periods of unemployment, and frequent job changes by both sexes. These workers also scored high for neuroticism, and had high rates of inpatient psychiatric treatment and suicide. With these high rates of formal mental health problems among employees who self-medicate with psychoactive drugs, discriminatory personnel management, including drug screening, jeopardizes confidentiality of treatment and civil rights.