Shoulder Musculoskeletal Disorders Research Articles

Ranking the effects of cycle time parameters, shoulder posture and load, on shoulder discomfort in a single experiment using Taguchi methods

AbstractThe purpose of this study was to use the Taguchi Design of Experiments approach to investigate the effects of five risk factors on ratings of shoulder discomfort in a single study. The development of shoulder MusculoSkeletal Disorders is complex as they are caused by several risk factors occurring simultaneously. In this study, five independent variables were tested (shoulder flexion, shoulder horizontal abduction, duty cycle regime, repetition rate, and load), each at four levels. Signal to noise ratio analysis was performed on the data to rank the magnitude of effects of the risk factors on shoulder discomfort. The results indicated repetition was first, with load second, flexion third, W/R regime fourth and abduction fifth. Therefore, the results indicated that repetition had the strongest effect on discomfort, while shoulder abduction had the least effect, for the combinations and levels of treatments studied.

3D peak and cumulative low back and shoulder loads and postures during greenhouse pepper harvesting using a video-based approach.

In agricultural field work many tasks have been cited as high priority risk factors for the development of work-related musculoskeletal disorders (WRMDs). Although video-based biomechanical approaches have been effective in documenting the physical demands and risks associated with various occupational and non-occupational tasks, to date, this method has yet to be used to document jobs such as crop harvesting in a greenhouse environment. To document and assess the postural characteristics and 3D peak and cumulative low back and shoulder loads associated with greenhouse pepper harvesting using a video-based posture sampling approach. Nine male (28.2 (4.1) years) pepper harvesters from a greenhouse in Southwestern Ontario, Canada were videotaped during a normal shift. 3DMatch was used to document working trunk and shoulder postures, from which 3D peak and cumulative forces and moments were quantified. On average, workers spent the majority of their time in neutral trunk postures (lateral bend: 99.1%; axial twist: 59.9%; flexion: 89.8%). Consistent results were found for the left and right shoulder, with the arms held in a neutral flexion posture 50% of the time or more. Four participants experienced peak L4/L5 compression forces (between 4116.3 N and 5937.0 N) which exceeded the NIOSH Action Limit (3400 N) during the cart pushing/pulling task, but remained below the threshold during picking. Mean cumulative L4/L5 extension and shoulder flexion moments ranged in magnitude from 18.5 Nm to 28.2 Nm, and between 19.4 Nm and 23.2 Nm, respectively, across all tasks. The postural characteristics and biomechanical loads associated with greenhouse pepper harvesting were quantified with a video-based biomechanical approach. Further investigations of the physical risk factors for low back and shoulder musculoskeletal disorders is warranted in pepper harvesting, given the postures and loads documented in this study.

Upper trapezius fatigue in carpet weaving: the impact of a repetitive task cycle

Introduction. Shoulder disorders are one of the most prevalent musculoskeletal disorders among carpet weavers. The most important cause of these disorders is muscle fatigue. The aim of the present study is to investigate the effect of carpet weaving characteristics on upper trapezius (UTr) muscle fatigue during a task cycle. Method. In this cross-sectional study, 9 women and 3 men participated. During an 80-min cycle of carpet weaving, a times-series model was applied to assess electromyography amplitude and frequency changes. Result. According to the joint analysis of electromyogram spectrum and amplitude method, the participants experienced 0% force decrease, 0.9% recovery, 18% force increase and 72% fatigue in the left UTr. Furthermore, the rates of force decrease, recovery, force increase and fatigue in the right UTr were 18%, 18%, 18% and 45%, respectively. Fatigue in the right and the left UTr was reported to be the dominant state during one carpet weaving task cycle. Conclusion. Task cycle appears to have a significant impact on UTr fatigue in participants, and UTr fatigue can be considered a serious risk factor in shoulder musculoskeletal disorders. Hence, further studies should focus on better workstations and work–rest periods during various subtasks.

Risk Factors for Upper Extremity Musculoskeletal Disorders Among Office Workers in Qom Province, Iran.

BackgroundThe identification of the risk factors for musculoskeletal disorders (MSDs) is the first step in designing effective preventive interventions.ObjectivesTo investigate the association between individual, organizational, physical, and psychological factors and upper extremity MSDs (i.e., shoulder, elbow and hand/wrist).Materials and MethodsIn this cross-sectional study, the study population was comprised of office workers from Qom Province, Iran. Of the 1630 Iranian office workers who were selected via a random multistage cluster sampling method, 1488 completed a comprehensive data collection form designed to investigate the individual, organizational, physical, and psychological factors related to MSDs (response rate: 91.3%).ResultsThe predictors of shoulder MSDs in the past 12 months were uncomfortable sitting posture (β = 0.42, P = 0.04), limited rest breaks (β=0.73, P = 0.012), and no access to adjustable desks (β = 0.43, P = 0.018). Working on a computer for more than five hours (β = 0.61, P = 0.004) and an uncomfortable sitting posture (β = 0.79, P = 0.001) predicted hand/wrist symptoms.ConclusionsVarious risk factors in the workplace may contribute to MSDs in different upper extremities. Preventive interventions should hence include ergonomic and office equipment modifications.

Exposure–response relationships for work-related neck and shoulder musculoskeletal disorders – Analyses of pooled uniform data sets

There is a lack of quantitative data regarding exposure–response relationships between occupational risk factors and musculoskeletal disorders in the neck and shoulders. We explored such relationships in pooled data from a series of our cross-sectional studies.We recorded the prevalence of complaints/discomfort (Nordic Questionnaire) and diagnoses (physical examination) in 33 groups (24 female and 9 male) within which the workers had similar work tasks (3141 workers, of which 817 were males). In representative sub-groups, we recorded postures and velocities of the head (N = 299) and right upper arm (inclinometry; N = 306), right wrist postures and velocities (electrogoniometry; N = 499), and muscular activity (electromyography) in the right trapezius muscle (N = 431) and forearm extensors (N = 206). We also assessed the psychosocial work environment (Job Content Questionnaire).Uni- and multivariate linear meta-regression analysis revealed several statistically significant group-wise associations. Neck disorders were associated with head inclination, upper arm elevation, muscle activity of the trapezius and forearm extensors and wrist posture and angular velocity. Right-side shoulder disorders were associated with head and upper arm velocity, activity in the trapezius and forearm extensor muscles and wrist posture and angular velocity.The psychosocial work environment (low job control, job strain and isostrain) was also associated with disorders. Women exhibited a higher prevalence of neck and shoulder complaints and tension neck syndrome than men, when adjusting for postures, velocities, muscular activity or psychosocial exposure.In conclusion, the analyses established quantitative exposure–response relationships between neck and shoulder disorders and objective measures of the physical workload on the arm. Such information can be used for risk assessment in different occupations/work tasks, to establish quantitative exposure limits, and for the evaluation of preventive measures.

Miniscalpel-Needle Treatment Is Effective for Work-Related Neck and Shoulder Musculoskeletal Disorders.

Background. Work-related musculoskeletal disorders (MSDs) are a group of painful disorders of muscles, tendons, and nerves, such as neck and shoulder MSD. This study was designed to use miniscalpel-needle (MSN) technique as an intervention for work-related MSDs. Methods. Thirty-one patients with work-related MSDs and 28 healthy subjects were enrolled as controls in this study. The MSD symptoms of each patient were assessed by visual analog scale (VAS) and neck disability index (NDI). Blood samples were collected from control subjects and MSD patients before and after treatment. Serum levels of C-reactive protein (CRP) and tumor necrosis factor (TNF) were measured using ELISA. Results. Prior to MSN treatment, serum levels of CRP and TNF were significantly higher in the MSD patients than the healthy controls. Serum CRP levels correlated with VAS and NDI scores, and serum TNF levels correlated with NDI scores. Compared to pretreatment, VAS and NDI scores were significantly lower in MSD patients after MSN treatment, while serum CRP and TNF levels were significantly lower compared with the healthy control levels. Conclusions. Our results indicate that MSN may be an effective intervention for work-related MSDs and be associated with lower serum levels of inflammatory biomarkers.

Comparison of epidemiological and clinical characteristics of shoulder musculoskeletal disorders between diabetic and nondiabetic populations

The non-traumatic shoulder pains are frequent. These diseases include preferentially tendinitis of the rotator cuff and retractile capsulitis described with diabetes. Our study aims to analyze musculoskeletal disorders by comparing the characteristics of these disorders between diabetics and non-diabetics patients. It is a cross-sectional, descriptive, analytical study comparing diabetic ( n = 34) and non-diabetic patients ( n = 48) seen from January to December 2013 at the Department of Physical Medicine and Rehabilitation of University Hospital Ibn Rochd, Casablanca, Morocco. The average age of our patients was 56.4 in diabetic vs. 54.1 years in non-diabetic patients, mostly women, 70.6% vs. 81.3% respectively. Pain was chronic in diabetic and acute in non-diabetic subjects. In both groups, the dominant member was significantly affected. Tendinitis of the rotator cuff was higher (65.2%) in non-diabetic patients while partial ruptures, calcified tendinitis and apsulitis were predominant in the diabetic group. These disorders generated an important functional limitation. We conclude that musculoskeletal disorders of the shoulder evolve and spread differently in diabetic patients compared to non-diabetic persons with consequent restriction of capabilities and limitations of participation.

Effect of a worktable position on head and shoulder posture and shoulder muscles in manual material handling.

According to a recent research, manual working with high levels of static contraction, repetitive loads, or extreme working postures involving the neck and shoulder muscles causes an increased risk of neck and shoulder musculoskeletal disorders. We investigated the effects of the forwardly worktable position on head and shoulder angles and shoulder muscle activity in manual material handling tasks. The forward head and shoulder angles and the activity of upper trapezius, levator scapulae, and middle deltoid muscle activities of 15 workers were measured during performing of manual material handling in two tasks that required different forward head and shoulder angles. The second manual material task required a significantly increased forward head and shoulder angle. The upper trapezius and levator scapulae muscle activity in second manual material task was increased significantly compared with first manual material task. The middle deltoid muscle activity in second manual material task was not significantly different compared with first manual material task. Based on this result, the forward head and shoulder angles while performing manual work need to be considered in selection of the forward distance of a worktable form the body. The high level contractions of the neck and shoulder muscles correlated with neck and shoulder pain. Therefore, the forward distance of a worktable can be an important factor in preventing neck and shoulder pain in manual material handling workers.

Evaluation of Shoulder Stability During Forceful Arm Exertions

Shoulder musculoskeletal disorders (MSDs) are a major cause of morbidity and pain in the modern working population. Epidemiological literature suggests that forceful arm exertions pose an increased risk for shoulder MSD development. The majority of shoulder MSDs involve the glenohumeral joint. The glenohumeral joint is characteristically unstable and stabilized by concavity compression mechanism. In this study a biomechanical model of shoulder complex was used to examine the concavity compression mechanism. Mechanical loading of the glenohumeral joint during forceful arm exertions was analyzed to quantify the angular position of the resultant muscle force vector in 3D space. The resultant muscle force vectors were almost always directed anteriorly, medially, and inferiorly, independent of the magnitude and the direction of the external force application. The knowledge gained in this study could possibly be used to quantify strain imposed on the shoulder muscles during forceful arm exertions.

Psychosocial Work Factors and Musculoskeletal Pain: A Cross-Sectional Study among Swedish Flight Baggage Handlers.

Objective. Flight baggage handlers sort and load luggage to airplanes. This study aimed at investigating associations between psychosocial exposures and low back and shoulder musculoskeletal disorders (MSDs) among Swedish flight baggage handlers. Methods. A questionnaire addressing MSDs (Standardized Nordic Questionnaire) and psychosocial factors (Copenhagen Psychosocial Questionnaire, COPSOQ) was answered by 525 baggage handlers in six Swedish airports. Results. Low back (LBP) and shoulder pain (SP) were reported by 70% and 60%, respectively. Pain was reported to interfere with work (PIW) by 30% (low back) and 18% (shoulders), and intense pain (PINT) occurred in 34% and 28% of the population. Quality of leadership was the most dissatisfying psychosocial factor, while the most positive was social community at work. Low ratings in the combined domain Work organization and job content were significantly associated with PIW in both low back and shoulders (Adjusted Hazard Ratios 3.65 (95% CI 1.67–7.99) and 2.68 (1.09–6.61)) while lower ratings in the domain Interpersonal relations and leadership were associated with PIW LBP (HR 2.18 (1.06–4.49)) and PINT LBP and SP (HRs 1.95 (1.05–3.65) and 2.11 (1.08–4.12)). Conclusion. Severity of pain among flight baggage handlers was associated with psychosocial factors at work, suggesting that they may be a relevant target for intervention in this occupation.

Predictors of Occupational Exposure to Neck and Shoulder Musculoskeletal Disorders among Sewing Machine Operators of Garment Industries in Ethiopia

Background: Occupational health problems related to upper limp musculoskeletal disorders were the major issue among sewing machine operators of garment industries in Ethiopia. The aim of this study was to assess the prevalence and associated risk factors of work related neck and shoulder musculoskeletal disorders among sewing machine operators of garment industries in Galan City, Oromia Regional State. Methods: A cross-sectional study was conducted from April 1 to 30, 2013. A total of 422 study subjects were included in this study. Standard Nordic Musculoskeletal Questionnaire was used to collect detailed information on musculoskeletal symptoms, socio demographic data, and factors associated with the problems through face to face interview. Results: From a total of 422 sewing machine operators included in the study 370 (87.7%) were females and 306 (72.5%) were in the age group of 16 years of service were about four times more likely to develop neck and shoulder musculoskeletal disorders than those who had short (1–5 years) year of services [AOR = 3.55, 95% CI: 1.24–10.16], medical history of systemic illness [AOR = 2.04, 95% CI: 1.02–4.08], and methods of payment [AOR = 2.04, 95% CI: 1.27–3.29], factors significantly associated with this disorders. Conclusion: Work related neck and shoulder musculoskeletal disorders were high among sewing machine operators in selected garment industries. Moreover, personal and environmental factors were identified as the potential risk factors related to neck and shoulder musculoskeletal disorders among the study group. Therefore, government and the owner of the garment industries should give special attention to prevent and control the problems through proper occupational health and safety policy implementation in the country.

Underreporting of musculoskeletal disorders in 10 regions in France in 2009.

Underreporting of occupational diseases (OD) has been quantified, in particular in the United States, but little information is available in other countries. The aim of this study was to evaluate underreporting of musculoskeletal disorders (MSD) in France in 2009. We calculated an indicator that approximated the underreporting rate of MSD in 10 regions of France. Two databases were used: data on OD compensated by insurance funding and data from the surveillance program for uncompensated work-related diseases. Analyses were performed for carpal tunnel syndrome (CTS) and elbow, shoulder, and lumbar spine MSD. The underreporting rate was estimated at 59% (range 52-64%) for CTS, 73% (range 67-79%) for elbow MSD, 69% (range 63-74%) for shoulder MSD, and 63% (range 50-76%) for lumbar spine MSD. This study revealed that MSD are substantially underreported in France, as in the United States, despite the differences in workers' compensation systems.

Shoulder disorders in female working-age population: a cross sectional study

BackgroundMusculoskeletal disorders (MSDs) are among the most common pathologies in the general population. However, research into the prevalence of upper arm MSDs is hampered by a lack of uniformity in case definition, and by the absence of a gold standard for measurement. Furthermore, some sectors of the population have benefited from extensive research whilst others have largely been ignored. Study Design: Cross-sectional study. Objectives: to investigate the prevalence of shoulder MSDs in a working age female population not exposed to specific occupational risk factors such as heavy and/or repetitive work, assessing the differences in prevalence recorded by using three different standard measurement tools.Methods302 working aged women were enrolled in this study (age 20–55 years). Each subject underwent three different assessments: standardized questionnaires for symptoms and disability and the SF36 health survey, a clinical assessment performed by a blinded orthopaedic specialist, and an imaging assessment by means of ultrasound (US) and Magnetic Resonance (MR) if indicated.ResultsAccording to the questionnaire 77 subjects (25.5%) complained of shoulder pain whilst 225 (74.5%) were asymptomatic. According to the clinical examination, 31 subjects (10.3%) resulted positive, whereas 271 subjects (89.7%) had normal shoulders. According to the imaging findings, 26 subjects (8.6%) had alterations to the anatomical structures of the shoulder, whilst 276 subjects (91.4%) had no detectable abnormalities in either shoulder. In all assessments, the prevalence increased with age (p = 0.001).ConclusionDepending on the outcome measure used, the prevalence of reported MSDs of the shoulder varies considerably. There is a striking difference between the prevalence of subjective reported symptoms and the standardized clinical/imaging examinations. However, the results of all the assessments did concur in one aspect; there was a significant trend of increased prevalence of shoulder MSDs with age. When looking at reported prevalence, this study shows the importance of noting the measurement method used before making comparisons, as it can vary considerably. The epidemic of shoulder pain reported is not indicative of an epidemic of shoulder pathology.

4륜 운반차 수직형 손잡이에서 인간공학적 최적 높이 및 간격 결정

Among various manual materials handling tasks, pushing/pulling was known to be one of the risk factors for the low back and shoulder musculoskeletal disorders (MSDs). This study was conducted to find out an optimal solution set of the handle height and distance for 4-wheel cart with two vertical handles. Ten male college students participated in the pushing force measurement experiment. The face-centered cube design, one of the central composite designs, was applied for the experiment, and the isometric voluntary pushing force was measured in 9 treatment conditions. The second order response surface model was predicted by using the pushing strength as a response variable, and the handle height and distance as independent factors. According to the 2nd order response model, the handle height and distance showed nonlinear relationship with the isometric pushing strength. To maximize the 2nd order response model (pushing force), the handle height and distance were optimized. The optimal handle height was 'xyphoid process height - stature', and the optimal handle distance was '<TEX>$1.25{\times}shoulder$</TEX> width'. When calculated using the anthropometric data of the subjects of this study, the optimal handle height was <TEX>$115.4{\pm}3.4$</TEX> cm, slightly higher than the elbow height, and the handle distance was <TEX>$52.9{\pm}2.3$</TEX> cm.

Patient's Body Size Influences Dental Hygienist Shoulder Kinematics

OCCUPATIONAL APPLICATIONS This study found that dental hygienists are exposed to higher shoulder elevation angles when treating a simulated big-girth patient versus a simulated average-girth patient. These differences in motion patterns may increase dental hygienists’ susceptibility to shoulder musculoskeletal disorders. Ergonomic interventions may be needed to facilitate solutions to problems associated with treating patients who are overweight or obese. Ergonomics and human factors practitioners should educate dental hygienists to be more aware of their body posture, specifically shoulder position, while working on patients with big chest girth. TECHNICAL ABSTRACT Background: Dental hygienists suffer from musculoskeletal disorders of the upper extremities, and the prevalence of these disorders increases with years of occupation. Furthermore, the prevalence of overweight and obese individuals in the United States has been rapidly increasing for both adults and children in recent years. This may increase the involvement of dental hygienists with obese patients, which may result in an increased prevalence of shoulder musculoskeletal disorders. The effect of patient's body size on the three-dimensional humeral and scapular kinematics of dental hygienists, however, is currently unknown. Purpose: The aim of the current study was to measure the influence of patient girth on the shoulder kinematics of dental hygienists during teeth instrumentation in a simulated work environment. Method: Sixteen female dental hygienists participated in a lab-based study that simulated a dental hygienist workplace. Three-dimensional kinematic data were collected for the right and left scapula and humerus using the Polhemus Liberty magnetic tracking system (Colchester, VT, USA). To quantify differences in humeral and scapular kinematics and exposure variables, two independent variables with two levels were chosen: handedness and body type size. Separate two-way ANOVAs with repeated measures were conducted. Results: Dental hygienists sustained significant higher mean humeral elevation angles and higher mean scapular upward rotation angles for the dominant and non-dominant hands while instrumenting a simulated patient with big girth chest. Furthermore, dental hygienists spent significantly more time above 30° and 60° of humeral elevation for the dominant and non-dominant hands while instrumenting this simulated patient. Conclusion: This study provided evidence that dental hygienists alter their shoulder kinematics while instrumenting patients having a larger girth. Consequently, working with patients who are obese, or with a larger body size, may increase dental hygienist susceptibility to shoulder musculoskeletal disorders.

The Prevalence of Work-Related Neck, Shoulder, and Upper Back Musculoskeletal Disorders among Midwives, Nurses, and Physicians: A Systematic Review

The Prevalence of Work-Related Neck, Shoulder, and Upper Back Musculoskeletal Disorders among Midwives, Nurses, and Physicians: A Systematic Review

The Prevalence of Work-Related Neck, Shoulder, and Upper Back Musculoskeletal Disorders Among Midwives, Nurses, and Physicians: A Systematic Review

The Prevalence of Work-Related Neck, Shoulder, and Upper Back Musculoskeletal Disorders Among Midwives, Nurses, and Physicians: A Systematic Review

Cortical mapping of the infraspinatus muscle in healthy individuals

BackgroundWhile cortical representations of intrinsic hand muscles have been extensively studied in healthy individuals, little is known about the representation of proximal upper limb muscles. Improving our understanding of normal shoulder function is important, given that shoulder musculoskeletal disorders affect approximately 20% of the population and are suspected to involve changes in central motor representations. The purpose of the study is to describe the motor representation (motor evoked potentials (MEP) amplitude at the hotspot, map area, normalized map volume and center of gravity) of the infraspinatus muscle in healthy individuals, and to explore the potential influence of hand dominance on this representation (i.e. symmetry of the excitability and of the location of motor map between sides), as well as the effect of age and gender on motor excitability.ResultsFifteen healthy participants took part in this study. No significant asymmetry between sides was observed for motor excitability (p = 0.14), map area (p = 0.73) and normalized map volume (p = 0.34). Moreover, no side x intensity interaction was found (p = 0.54), indicating similar stimulus response properties. No difference between sides was found in the location of infraspinatus motor representation, either in the mediolateral or anteroposterior axis (p > 0.10). Neither age nor gender influenced aMT (p > 0.58) or MEP size (p > 0.61).ConclusionsAs the cortical representation of infraspinatus muscles was found to be symmetric between sides, both in terms of excitability and location, comparisons between the intact and affected side could be performed in clinical studies, regardless of whether the dominant or non-dominant side is affected. The next step will be to characterize corticospinal excitability and map parameters in populations with shoulder disorders.

Shoulder muscle fatigue during repetitive tasks as measured by electromyography and near-infrared spectroscopy.

The objective of this study was to quantify shoulder muscle fatigue during repetitive exertions similar to motions found in automobile assembly tasks. Shoulder musculoskeletal disorders (MSDs) are a common and costly problem in automotive manufacturing. Ten subjects participated in the study. There were three independent variables: shoulder angle, frequency, and force. There were two types of dependent measures: percentage change in near-infrared spectroscopy (NIRS) measures and change in electromyography (EMG) median frequency. The anterior deltoid and trapezius muscles were measured for both NIRS and EMG. Also, EMG was collected on the middle deltoid and biceps muscles. The results showed that oxygenated hemoglobin decreased significantly due to the main effects (shoulder angle, frequency, and force). The percentage change in oxygenated hemoglobin had a significant interaction attributable to force and repetition for the anterior deltoid muscle, indicating that as repetition increased, the magnitude of the differences between the forces increased. The interaction of repetition and shoulder angle was also significant for the percentage change in oxygenated hemoglobin. The median frequency decreased significantly for the main effects; however, no interactions were statistically significant. There was significant shoulder muscle fatigue as a function of shoulder angle, task frequency, and force level. Furthermore, percentage change in oxygenated hemoglobin had two statistically significant interactions, enhancing our understanding of these risk factors. Ergonomists should examine interactions of force and repetition as well as shoulder angle and repetition when evaluating the risk of shoulder MSDs.

Trastornos músculo-esqueléticos del hombro en atención primaria. Estudio de prevalencia en un centro de la Agencia Valenciana de Salud

IntroductionMusculoskeletal shoulder problems are a common cause of morbidity in the general population and can lead to occupational and domestic functional alterations. The main objective of this study is to calculate the prevalence of musculoskeletal shoulder disorders in the health care setting. Material and methodWe conducted a cross-sectional study to calculate the prevalence of shoulder disorders in a primary health care setting. To acquire information, interconsultation documents and the statistical records from a Basic Rehabilitation Unit, concerning the years 2009 and 2010, were employed. ResultsA total of 1,565 patients were attended in the medical centre during the study period, 268 cases of which were included in the study. Prevalence of shoulder problems was 17.12% which peaked between the ages of 50 and 59. The most frequent diagnosis categories were “non-specific” and “subacromial syndrome”, while the least represented was “acromioclavicular syndrome”. DiscussionThe population characteristics (gender distribution and mean age) coincide with those presented in other studies done in a health care setting. Distribution per age group follows a similar pattern to that detected in a health care setting. The prevalence figures tend to show high variability due to the methodological differences found among the different studies. It can be concluded that musculoskeletal shoulder disorders affect one fifth of the study population.