Caroline K. Smith

Rotator cuff syndrome: personal, work-related psychosocial and physical load factors.

Objective: To identify factors associated with rotator cuff syndrome (RCS) among active workers. Methods: Seven hundred thirty-three workers in 12 worksites participated in a cross-sectional study with individual structured physical and psychosocial health interviews, physical examinations, and exposure assessments of biomechanical factors. Work organization, including job content or structural constraints, was assessed at the departmental level. Multivariable logistic modeling was used. Results: Fifty-five subjects (7.5%) had RCS. Cases were more likely to report low job security (P < 0.04) and to have very high job structural constraints (P < 0.03). Age and body mass index were marginally significant. Upper arm flexion ≥ 45° ≥ 15% of time and either duty cycle of forceful exertions ≥9% time (odds ratio = 2.43, 95% CI = 1.04 to 5.68) or forceful pinch >0% [odds ratio = 2.66, 95% CI = 1.26 to 5.59] were significant risk factors. Conclusions: Long duration of shoulder flexion and forceful exertion (especially pinch) in a job are significant risk factors for RCS. Work organization may impact physical and psychosocial exposures and should be further explored.

Quantitative exposure-response relations between physical workload and prevalence of lateral epicondylitis in a working population.

BACKGROUND Lateral epicondylitis is a common work-related musculoskeletal disorder. The objective of this study was to identify risk factors associated with lateral epicondylitis among active workers. METHODS Seven-hundred thirty-three workers in 12 Washington worksites participated in structured interviews, physical examinations, and individual exposure assessments of biomechanical and psychosocial factors. Multivariable logistic modeling was used. RESULTS Thirty-eight subjects (5.2%) had lateral epicondylitis. Age (36-50 years-old), being female, and low social support at work were significant risk factors. Frequency of forceful exertion (> or =5 vs. < 1 times/min (OR 5.17, 95%CI 1.78-15.02), and > or =1 to <5 vs. <1 (OR 4.47, 95%CI 1.57-13.71)) and forearm supination at > or =45 degrees for > or =5% of the time with high lifting force (OR = 2.98, 95% CI 1.18-7.55) were significant physical load factors. CONCLUSIONS Frequency of forceful exertion or a combination of forearm supination and forceful lifting were significant physical factors and should be considered for prevention strategies.

Assessing Validity of the QuickDASH and SF-12 as Surveillance Tools among Workers with Neck or Upper Extremity Musculoskeletal Disorders

The purpose of this article was to assess validity of the regional Disabilities of Arm, Shoulder, and Hand (QuickDASH) and Short-Form 12 (SF-12) for surveillance purpose. We compared the predictive, discriminate, and concurrent validity of the QuickDASH and SF-12 among 231 workers with specific clinical diagnoses of neck or upper extremity musculoskeletal disorders (UEMSDs) and 175 workers with symptoms only. Compared to those with symptoms only, the odds of being any neck or UEMSD case were 1.45 (95% confidence interval [95% CI]: 1.24-1.70) and 0.66 (95% CI: 0.48-0.91) with every 10-point increase in QuickDASH disability and physical component scale (PCS-12) scores, respectively. The clinical cases had significantly higher QuickDASH disability (23.0 vs. 14.3, p<0.0001) and lower PCS-12 scores (44.8 vs. 47.3, p=0.0133) than those with symptom only. The QuickDASH disability scores were moderately correlated with the PCS-12 scores (rho=-0.40) among the clinical cases. Either QuickDASH or PCS-12 can be used as a simple surveillance tool in an active working population.

Reliability and validity assessment of the hand activity level threshold limit value and strain index using expert ratings of mono-task jobs.

This study evaluated two subjective assessment methods for physical work-related musculoskeletal disorder (WMSD) risk factors. A total of 567 participants from 12 companies in the manufacturing and health care industries were evaluated using the hand activity level (HAL) threshold limit value (TLV) and the Strain Index. Inter-rater reliability comparisons were performed on 125 selected cyclic tasks, with one novice and three experienced raters. Predictive validity was assessed by evaluation of relationships between measured exposure parameters and diagnosed WMSDs of the hand/wrist and elbow. HAL hand repetition ratings had a Spearman r value of 0.65 and a kappa value of 0.44 between raters. Subjective force (0–10 scale) estimates had a Spearman r = 0.28 and were not significantly different between raters (p > .05). The rating comparison for the four subjective components of the Strain Index had Spearman r correlations of 0.37–0.62 and kappa values of 0.25–0.44. The Strain Index and HAL TLV agreed on exposure categorization 56% of the time. Logistic regression showed, after adjustment for age, gender, and body mass index, that higher peak hand force estimates (odds ratio [OR] 1.14, confidence interval (CI) 1.02–1.27), most common force estimates (OR 1.14, CI 1.02–1.28), hand/wrist posture rating (OR 1.71, CI 1.15–2.56), and Strain Index scores ≥ 7 (OR 1.82, CI 1.04–3.18) were associated with distal upper extremity disorders in the dominant hand. HAL repetition ratings ≥ 4 (OR 2.81, CI 1.40–5.62) and hand/wrist posture ratings (OR 1.59, CI 1.01–2.49) were associated with disorders in the nondominant hand. These findings show moderate to good inter-rater agreement and significant relationships to health outcomes for the identified measures.

Psychosocial Factors and Shoulder Symptom Development Among Workers

BACKGROUND Shoulder injuries are a common cause of pain and discomfort. Many work-related factors have been associated with the onset of shoulder symptoms. The psychosocial concepts in the demand-control model have been studied in association with musculoskeletal symptoms but with heterogeneous findings. The purpose of this study was to assess the relationship between the psychosocial concepts of the demand-control model and the incidence of shoulder symptoms in a working population. METHODS After following 424 subjects for approximately 1 year, 85 incident cases were identified from self-reported data. Cox proportional hazards modeling was used to assess the associations between shoulder symptoms and demand-control model quadrants. RESULTS Cases were more likely to be female and report other upper extremity symptoms at baseline (P < 0.05). From the hazard models, being in either a passive or high strain job quadrant was associated with the incidence of shoulder symptoms. Hazard ratios were 2.17, 95% CI 1.02-4.66 and 2.19, 95% CI 1.08-4.42, respectively. CONCLUSIONS Using self-reporting to determine demand-control quadrants was successful in identifying subjects at risk of developing work-related shoulder symptoms. Research is needed to determine if this relationship holds with clinically diagnosed shoulder and other upper extremity musculoskeletal disorders. This may be part of a simple tool for assessing risk of developing these UEMSDs.

Responsiveness of the QuickDASH and SF-12 in Workers with Neck or Upper Extremity Musculoskeletal Disorders: One-Year Follow-Up

Introduction Questionnaires that measure functional status such as the Disability of the Arm, Shoulder and Hand (QuickDASH) and the Medical Outcomes Study 12-item Short-Form Health Survey (SF-12) can quantify the impact of health on performance. Little is known about whether these questionnaires can be used as a tool for measuring disabilities among workers. We compare the responsiveness of these two functional status questionnaires to changes in clinical outcomes of neck or upper extremity musculoskeletal disorders (UEMSD) among active workers in a longitudinal study. Methods We evaluated the effect size (ES) and standardized response means (SRM) of the QuickDASH and the SF-12 for 148 workers who were divided into four subgroups based on the diagnosis status change between baseline and 1-year visit. Results The ES and SRM for QuickDASH scores were 0.6/0.6 for the 50 subjects who became incident symptomatic neck or UEMSD cases, 1.3/1.0 for the 18 subjects who became incident clinical cases of neck or UEMSD, −1.0/−1.1 for the 46 subjects who recovered from having neck or UEMSD symptoms, and −1.1/−1.1 for the 34 subjects who recovered from being neck or UEMSD clinical cases. The correspondent ES/SRM for the QuickDASH work module were 0.4/0.3, 0.7/0.5, −0.6/−0.4, and −1.0/−0.8, respectively. The correspondent ES/SRM for the physical component scores of SF-12 (PCS12) for the four subgroups were 0.2/0.2, −0.9/−0.6, 0.3/0.2, and 0.3/0.3, respectively. Conclusions The QuickDASH scores were responsive to changes among active workers who were neck or UEMSD symptomatic or clinical case. PCS12 scores were sufficient only for use in clinical case status change.

Evaluation of a symptom diagram for identifying carpal tunnel syndrome

BACKGROUND Hand symptom diagrams (HSDs) for rating the distribution of paraesthesias are proposed for use in epidemiological studies of carpal tunnel syndrome (CTS). AIM To assess the validity of HSDs in a working population of manufacturing and service workers participating in a prospective study of musculoskeletal disorders. METHODS Assessment of each subject involved completing a HSD, a heath assessment and electrodiagnostic studies (EDSs). HSDs were rated for CTS blinded to the health assessment and EDS results. The validity assessments of HSD used EDS as the sole confirmatory standard for CTS. RESULTS A total of 733 subjects (65% of those eligible) participated in the study and 720 underwent EDSs. Dominant hand prevalence of a positive HSD and delayed nerve conduction studies in this working population was 9.2 per 100 workers. The sensitivity of a positive HSD for all workers was 0.28. By restricting the population to those workers with any current hand symptoms or to any worker with neuropathic hand symptoms, the sensitivities of HSD improved to 0.61 and 0.79, respectively. The positive predictive value of a HSD, with our study prevalence, was 0.48. CONCLUSIONS The HSD classification schema has poor validity when applied to a general working population but improves when applied to workers with current neuropathic symptoms. The high number of false-negative HSDs in the general study population is most likely to be due to the inadequacies of using EDS as the confirmatory test. With a low prevalence of CTS, the positive predictive value for HSDs is poor.

Predicting work-related incidence of lateral and medial epicondylitis using the strain index.

BACKGROUND The Strain Index (SI) has been developed to evaluate the risk for developing a distal upper extremity disorder. The objective of this study is to determine if the SI predicts incidence cases of work-related lateral, medial, or any epicondylities (LEPI, MEPI, and EPI). METHODS Six hundred seven workers were followed for up to 3.5 years, 70 developed EPI on the dominant side (44 LEPI, 13 MEPI, and 13 both). Survival analyses were conducted adjusting for demographic, psychosocial, and work organizational factors, with the SI as time-dependent variable. RESULTS High exposure (SI > 5), older age, and self-perceived poor general health were associated with incidence of LEPI and EPI, but not MEPI. There was a significant relationship between higher scores of SI and LEPI, hazard ratio (HR) 2.00 (95% CI 1.04-3.87) for SI 5.1-12, HR 2.12 (95% CI 1.11-4.05) for SI > 12. CONCLUSIONS The SI can effectively identify jobs with increased risk of developing incidence of LEPI.

Physical Exposure Assessment in a Large Prospective Upper Extremity Musculoskeletal Disorders Study

This paper describes a battery of physical exposure assessment methods used in a large prospective upper extremity musculoskeletal disorders study. Different from some previous prospective studies, this study collects health and physical exposure data for each study subject rather than at a group level. Subjects are recruited from different job categories based on their hand activity exposure categories. Multiple exposure assessment methods are used to measure job physical exposures such as force, repetition, and work posture. This will allow us to compare the sensitivity of different exposure assessment methods in predicting the risk for upper extremity musculoskeletal disorders. Procedures have also been taken to monitor inter-observer reliability for some observational analyses. During the first year of the study, baseline exposure measurements have been collected from 607 volunteers at 11 different worksites. Follow-up measurements have also been collected in these worksites. Whenever a participant has a significant job change, a new exposure assessment is conducted at the new job. This paper will primarily discuss the various exposure assessment methods used in this study, and use some preliminary results to demonstrate some of the data reduction methods.