2014-10-01 12:00 - Messages

Acute effect of topical menthol on chronic pain in slaughterhouse workers with carpal tunnel syndrome

Triple-blind, randomized placebo-controlled trial
Topical menthol gels are classified "topical analgesics" and are claimed to relieve minor aches and pains of the musculoskeletal system. In this study we investigate the acute effect of topical menthol on carpal tunnel syndrome (CTS). We screened 645 slaughterhouse workers and recruited 10 participants with CTS and chronic pain of the arm/hand who were randomly distributed into two groups to receive topical menthol (Biofreeze) or placebo (gel with a menthol scent) during the working day and 48 hours later the other treatment (crossover design). Participants rated arm/hand pain intensity during the last hour of work (scale 0-10) immediately before 1, 2, and 3 hours after application. Furthermore, global rating of change (GROC) in arm/hand pain was assessed 3 hours after application. Compared with placebo, pain intensity and GROC improved more following application of topical menthol (P = 0.026 and P = 0.044, resp.). Pain intensity of the arm/hand decreased by -1.2 (CI 95%: -1.7 to -0.6) following topical menthol compared with placebo, corresponding to a moderate effect size of 0.63. In conclusion, topical menthol acutely reduces pain intensity during the working day in slaughterhouse workers with CTS and should be considered as an effective nonsystemic alternative to regular analgesics in the workplace management of chronic and neuropathic pain.

Source: Sundstrup E, Jakobsen MD, Brandt M, et al. Rehabilitation Research and Practice, 2014.

Time trends in musculoskeletal disorders attributed to work exposures in Ontario using three independent data sources, 2004–2011

Objective: Work-related musculoskeletal disorders (MSDs) are the leading cause of work disability in the developed economies. The objective of this study was to describe trends in the incidence of MSDs attributed to work exposures in Ontario over the period 2004–2011.
Methods: An observational study of work-related morbidity obtained from three independent sources for a complete population of approximately six million occupationally active adults aged 15–64 in the largest Canadian province. We implemented a conceptually concordant case definition for work-related non-traumatic MSDs in three population-based data sources: emergency department encounter records, lost-time workers' compensation claims and representative samples of Ontario workers participating in consecutive waves of a national health interview survey.
Results: Over the 8-year observation period, the annual per cent change (APC) in the incidence of work-related MSDs was −3.4% (95% CI −4.9% to −1.9%) in emergency departments' administrative records, −7.2% (−8.5% to −5.8%) in lost-time workers' compensation claims and −5.3% (−7.2% to −3.5%) among participants in the national health interview survey. Corresponding APC measures for all other work-related conditions were −5.4% (−6.6% to −4.2%), −6.0% (−6.7% to −5.3%) and −5.3% (−7.8% to −2.8%), respectively. Incidence rate declines were substantial in the economic recession following the 2008 global financial crisis.
Conclusions: The three independent population-based data sources used in this study documented an important reduction in the incidence of work-related morbidity attributed to non-traumatic MSDs. The results of this study are consistent with an interpretation that the burden of non-traumatic MSDs arising from work exposures is declining among working-age adults.

Source: Cameron A Mustard, Andrea Chambers, Selahadin Ibrahim, Jacob Etches, Peter Smith. Occup Environ Med, 2014.

The effect of the presence and characteristics of an outlying group on exposure–outcome associations

Objectives: Physical exposures (eg, lifting or bending) are believed to be risk factors for low-back pain (LBP), but the literature is inconsistent. Exposure and LBP prevalence differ considerably between occupations, and exposure–outcome associations could be severely modified by the presence of particular occupational groups. We aimed to investigate the influence of such outlying groups on the properties of associations between exposure and LBP.
Methods: Lifting and trunk flexion were observed for 371 of 1131 workers within 19 groups. LBP was obtained from all workers during three follow-up years. Both exposure variables were associated with LBP (P<0.01) in this parent dataset. By removing the 19 groups one-by-one and performing logistic regressions analysis on the 18 remaining groups, we demonstrated that one group, mainly road workers, with outlying exposures and LBP prevalence substantially affected the exposure–outcome association in the total population. In order to further examine this phenomenon, we assessed, by simulation, the influence of realistic sizes (n=4, 8, 16, 32, 64, 128), mean exposures (e=2000, 3000, 4000 lifts and e=30, 40, 50% trunk flexion time) and LBP prevalences (p=70, 80, 90, 100%) of the outlying group on the strength and certainty of the eventual relationship between exposure and LBP. For each combination of n, e and p, 3000 virtual studies were constructed, including the simulated group together with the other 18 original groups from the parent data-set. Average odds ratios (OR), 95% confidence limits, and power (P<0.05) were calculated across these 3000 studies as measures of the properties of each virtual study design.
Results: OR were attenuated more towards 1 and power decreased with smaller values of n, e, and p in the outlying group. Changes in group size and prevalence had a larger influence on OR and power than changes in mean exposure.
Conclusions: The size and characteristics of a single group with high exposure and outcome prevalence can strongly influence both the OR point estimate and the likelihood of obtaining significant exposure–outcome associations in studies of large populations. These findings can guide interpretations of prior epidemiological studies and support informed design of future studies.

Source: Coenen P, Mathiassen SE, Kingma I, Boot CRL, Bongers PM, van Dieën JH. 2014, Scand J Work Environ Health.

Arm and Neck Pain in Ultrasonographers

Objective: The aim of this study was to evaluate the prevalence of upper-body-quadrant pain among ultrasonographers and to evaluate the association between individual ergonomics, musculoskeletal disorders, and occurrence of neck pain.
Method: A hundred and ten (N = 110) Belgian and Dutch male and female hospital ultrasonographers were consecutively enrolled in the study. Data on work-related ergonomic and musculoskeletal disorders were collected with an electronic inquiry, including questions regarding ergonomics (position of the screen, high-low table, and ergonomic chair), symptoms (neck pain, upper-limb pain), and work-related factors (consecutive working hours a day, average working hours a week).
Results: Subjects with the screen on their left had significantly more neck pain (odds ratio [OR] = 3.6, p = .0286). Depending on the workspace, high-low tables increased the chance of developing neck pain (OR = 12.9, p = .0246). A screen at eye level caused less neck pain (OR = .22, p = .0610). Employees with a fixed working space were less susceptible to arm pain (OR = 0.13, p = .0058). The prevalence of arm pain was significantly higher for the vascular department compared to radiology, urology, and gynecology departments (OR = 9.2, p = .0278).
Conclusions: Regarding prevention of upper-limb pain in ultrasonograph, more attention should be paid to the work environment and more specialty to the ultrasound workstation layout. Primary ergonomic prevention could provide a painless work situation for the ultrasonographer.
Application: Further research on the ergonomic conditions of ultrasonography is necessary to develop ergonomic solutions in the work environment that will help to alleviate neck and arm pain.

Source: Claes, Frank, Berger, Jan & Stassijns, Gäetane. Human Factors, 2014.

Psychometric properties evaluation of a new ergonomics-related job factors questionnaire developed for nursing workers

The objectives of this study were to develop a questionnaire that evaluates the perception of nursing workers to job factors that may contribute to musculoskeletal symptoms, and to evaluate its psychometric properties. Internationally recommended methodology was followed: construction of domains, items and the instrument as a whole, content validity, and pre-test. Psychometric properties were evaluated among 370 nursing workers. Construct validity was analyzed by the factorial analysis, known-groups technique, and convergent validity. Reliability was assessed through internal consistency and stability. Results indicated satisfactory fit indices during confirmatory factor analysis, significant difference (p < 0.01) between the responses of nursing and office workers, and moderate correlations between the new questionnaire and Numeric Pain Scale, SF-36 and WRFQ. Cronbach's alpha was close to 0.90 and ICC values ranged from 0.64 to 0.76. Therefore, results indicated that the new questionnaire had good psychometric properties for use in studies involving nursing workers.

Source: Orpinelli Coluci, Marina Zambon & Costa Alexandre, Neusa Maria. (2014). Applied Ergonomics, 45 (6), p. 1588-1596.

Effects of work experience on work methods during dynamic pushing and pulling

Pushing and pulling are potential risk factors for work-related low back disorders (WRLBDs). While several studies have evaluated differences in work methods related to work experience, such evidence for dynamic pushing and pulling is limited. Eight novices and eight experienced workers completed dynamic push/pull tasks using a cart weighted to 250% of individual body mass in two different configurations (preferred vs. elbow handle heights). Multiple measures [hand forces, torso kinematics and kinetics, and required coefficient of friction (RCOF)] were obtained to assess WRLBD and slip risks. Experienced workers generated higher medio-lateral hand forces, during both pulls and pushes, though with a more substantial difference during pushes (∼74%), and which involved the use of hand force components other than to move the cart in an anterior-posterior direction. Experienced workers also had lower peak torso kinematics in flexion/extension and lateral bending, and lower torso flexion/extension kinetics. The latter is suggestive of a lower risk for WRLBDs, though levels of exposures to WRLBD risk were low to moderate in both groups and were often relatively small and inconsistent across the task configurations. Group-level differences in RCOF were quite small, indicating a comparable slip risk between the two groups. Thus, it was considered inconclusive whether the work methods used by experienced workers during dynamic pushing and pulling are advantageous regarding WRLBD and slip risks.

Source: Lee, Jungyong, Nussbaum, Maury A., Kyung, Gyouhyung. (2014). International Journal of Industrial Ergonomics, 44(5), 647-653.

Lasting effects of workplace strength training for neck/shoulder/arm pain among laboratory technicians

Natural experiment with 3-year follow-up
Objectives. This study investigated long-term effects and implementation processes of workplace strength training for musculoskeletal disorders. Methods. 333 and 140 laboratory technicians from private and public sector companies, respectively, replied to a 3-year follow-up questionnaire subsequent to a 1-year randomized controlled trial (RCT) with high-intensity strength training for prevention and treatment of neck, shoulder, and arm pain. Being a natural experiment, the two participating companies implemented and modified the initial training program in different ways during the subsequent 2 years after the RCT. Results. At 3-year follow-up the pain reduction in neck, shoulder, elbow, and wrist achieved during the first year was largely maintained at both companies. However, the private sector company was rated significantly better than the public sector company in (1) training adherence, (2) training culture, that is, relatively more employees trained at the workplace and with colleagues, (3) self-reported health changes, and (4) prevention of neck and wrist pain development among initially pain-free employees. Conclusions. This natural experiment shows that strength training can be implemented successfully at different companies during working hours on a long-term basis with lasting effects on pain in neck, shoulder, and arm.

Source:  Mortensen P, Larsen AI, Zebis MK, et al. BioMed Research International, Volume 2014 (2014).

Évaluation subjective de la charge de travail

Utilisation des échelles de Borg
L'évaluation subjective est un outil précieux, précis et reproductible pour mesurer la charge de travail. Elle peut être utilisée seule(échelles d'auto-évaluation, questionnaires...) ou en parallèle aux nombreuses métrologies objectives.
Après une courte présentation de l'évaluation subjective à l'aide des échelles de Borg (RPE et CR10), des exemples d'études menées en laboratoire et en situation de travail sont présentés pour argumenter leurs utilisations et leurs apports dans un bilan des conditions de travail.

Source: J.P. Meyer. Références en santé au travail, septembre 2014, no 139, p. 105-122.

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