Hand and arm injuries associated with repetitive manual work in industry: a review of disorders, risk factors and preventive measures

Force Control Strategy of Five-Digit Precision Grasping With Aligned and Unaligned Configurations

OBJECTIVE

To investigate the digit force control during a five-digit precision grasp in aligned (AG) and unaligned grasping (UG) configurations.

BACKGROUND

The effects of various cylindrical handles for tools on power grasp performance have been previously investigated. However, there is little information on force control strategy of precision grasp to fit various grasping configurations.

METHOD

Twenty healthy young adults were recruited to perform a lift-hold-lower task. The AG and UG configurations on a cylindrical simulator with force transducers were adjusted for each individual. The applied force and moment, the force variability during holding, and force correlations between thumb and each finger were measured.

RESULT

No differences in applied force, force correlation, repeatability, and variability were found between configurations. However, the moments applied in UG were significantly larger than those in AG.

CONCLUSION

The force control during precision grasp did not change significantly across AG and UG except for the digit moment. The simulator is controlled efficiently with large moment during UG, which is thus the optimal configuration for precision grasping with a cylindrical handle. Further research should consider the effects of task type and handle design on force control, especially for individuals with hand disorders.

APPLICATION

To design the handle of specific tool, one should consider the appropriate configuration according to the task requirements of precision grasping to reduce the risk of accumulating extra loads on digits with a cylindrical handle.

Temperature Asymmetry Analysis between Left and Right Wrist with Sensory and Infrared Thermography

This article reports a thermal analysis of the wrists to analyze the behavior and recovery of skin temperature after 20 min when performing a highly repetitive movement, and two thermography methods (sensory and infrared) and research groups were compared. The tests were carried out with 44 participants who performed a repetitive task for 10 min and integrated into two groups, of which 22 were trained workers from a maquiladora company and were analyzed with sensory thermography, and the other 22 were in the laboratory with infrared thermography with undergraduate students. The study area is the left and right hand, specifically the wrists. The proposed hypothesis is that people with some musculoskeletal problems have a decrease in temperature when starting repetitive tasks and thermal asymmetries, which measurements were recorded at 0, 10, 15, and 20 min after the task was finished. Findings indicate that the temperatures in both wrists behave similarly. The workers reached higher temperatures, and the centigrade degrees of asymmetry difference were also higher. The variable with influence on the temperature was fractured in the arm. After thermally analyzing the temperature behavior between the wrists of both hands, it is concluded that there is an increase in temperature after finishing a repetitive task, and it does not stabilize after 20 min. Both thermography methods observed that the asymmetries are greater than 0.5 °C, detecting the possible pathology of carpal tunnel syndrome.

Acute physiological and functional effects of repetitive shocks on the hand-arm system - a pilot study on healthy subjects

PURPOSE

Exposure to hand-transmitted shocks is a widespread phenomenon at the workplace. Separate risk assessments for shocks do not exist in current international hand-arm vibration regulations, leading to a potential underestimation of associated health risks.

METHODS

In a pilot study approach, N = 8 healthy males were exposed to sets of 3×5 minutes of repetitive shocks and 1×5 minutes of random vibration, controlled at a weighted vibration total value of 10 m/s² respectively. Baseline and post-exposure measurements of vibration perception thresholds, finger skin temperature, maximal grip / pinch force and the Purdue Pegboard test were conducted. Muscle activity was monitored continuously by surface electromyography.

RESULTS

Shock exposures evoked a temporary increase of vibration perception thresholds with high examination frequencies. A decrease of skin temperature was hinted for 1 s^-1 and 20 s^-1 shocks. Electromyographical findings indicated an additional load on two forearm muscles during shock transmission. Maximum grip force and manual dexterity were not affected, pinch force only partially reduced after the exposures.

CONCLUSION

Physiological effects from shock exposure conform to those described for hand-arm vibration exposure in principle, although some divergence can be hypothesized. Randomized designs are required to conclusively assess the need of occupational health concepts specifically for hand-transmitted shocks.

Multi-task exposure assessment to infer musculoskeletal disorder risk: A scoping review of injury causation theories and tools available to assess exposures

Exposure assessment is critical for understanding musculoskeletal disorder (MSD) risk. Previous reviews summarized the tools available for single-task exposure assessment, however no reviews summarize tools available to assess the accumulation or aggregation of exposure associated with the performance of multiple tasks (i.e., multi-task assessment). We address this gap by using a scoping review methodology to: 1) summarize the theories explaining how multi-task exposures may lead to MSDs, and 2) summarize the models and tools available to assess multi-task exposures, stratified based on prevailing theories. Using a systematic search strategy, 3230 articles were identified, of which 34 were retained for data extraction. Of the retained articles, 13 described MSD causation theories, 12 described mathematical models (not yet accessible as tools), six described readily accessible tools, and three described both theories and a model or tool. We summarized the state-of-the-art in multi-task exposure assessment and highlight the need for more tools that assess muscle fatigue and inform on recovery.

Occupational ergonomic assessment of MSDs among the artisans working in Bagh hand block printing industry in Madhya Pradesh, India

PURPOSE

Hand block printing technique practiced in Dhar District of Madhya Pradesh (M.P.) involves highly repetitive tasks with awkward posture, which contribute to the development of musculoskeletal disorders (MSDs) among the artisans, The aim of this study was to determine the prevalence of MSDs and the risks factors involved. Materials and methods: an observational study and a self-reported questionnaire study were conducted with a sample of 70 artisans. The working postures of the artisans were analyzed using Rapid upper limb assessment (RULA) and Occupational repetitive actions method (OCRA). p ≤ 0.05 was considered significant throughout the study.

RESULTS

MSDs in the neck, shoulders, elbows, wrist/forearm, Lower back, and Hips/Thighs were found to be highly prevalent among artisans of age greater than 31 and experience greater than 11. Most complaints were reported in the wrist, neck and lower back region.

CONCLUSION

From the findings, it was evident that artisans working in Bagh printing are at high risk of the development of MSDs; thus, an immediate intervention is needed to eliminate the ergonomic risks among the artisans.

Aberrant Neuronal Activity in a Model of Work-Related Upper Limb Pain and Dysfunction

Work-related musculoskeletal disorders associated with intense repetitive tasks are highly prevalent. Painful symptoms associated with such disorders can be attributed to neuropathy. In this study, we characterized the neuronal discharge from the median nerve in rats trained to perform an operant repetitive task. After 3-weeks of the task, rats developed pain behaviors and a decline in grip strength. Ongoing activity developed in 17.7% of slowly conducting neurons at 3-weeks, similar to neuritis. At 12-weeks, an irregular high frequency neuronal discharge was prevalent in >88.4% of slow and fast conducting neurons. At this time point, 8.3% of slow and 21.2% of fast conducting neurons developed a bursting discharge, which, combined with a reduction in fast-conducting neurons with receptive fields (38.4%), is consistent with marked neuropathology. Taken together, we have shown that an operant repetitive task leads to an active and progressive neuropathy that is characterized by marked neuropathology following 12-weeks task that mainly affects fast conducting neurons. Such aberrant neuronal activity may underlie painful symptoms in patients with work-related musculoskeletal disorders. PERSPECTIVE: Aberrant neuronal activity, similar to that reported in this study, may contribute to upper limb pain and dysfunction in patients with work-related musculoskeletal disorders. In addition, profiles of instantaneous frequencies may provide an effective way of stratifying patients with painful neuropathies.

Evaluation of a New Simplified Inertial Sensor Method against Electrogoniometer for Measuring Wrist Motion in Occupational Studies

Wrist velocity is an important risk factor for work-related musculoskeletal disorders in the elbow/hand, which is also difficult to assess by observation or self-reports. This study aimed to evaluate a new convenient and low-cost inertial measurement unit (IMU)-based method using gyroscope signals against an electrogoniometer for measuring wrist flexion velocity. Twelve participants performed standard wrist movements and simulated work tasks while equipped with both systems. Two computational algorithms for the IMU-based system, i.e., IMU_norm and IMU_flex, were used. For wrist flexion/extension, the mean absolute errors (MAEs) of median wrist flexion velocity compared to the goniometer were <10.1°/s for IMU_norm and <4.1°/s for IMU_flex. During wrist deviation and pronation/supination, all methods showed errors, where the IMU_norm method had the largest overestimations. For simulated work tasks, the IMU_flex method had small bias and better accuracy than the IMU_norm method compared to the goniometer, with the MAEs of median wrist flexion velocity <5.8°/s. The results suggest that the IMU-based method can be considered as a convenient method to assess wrist motion for occupational studies or ergonomic evaluations for the design of workstations and tools by both researchers and practitioners, and the IMU_flex method is preferred. Future studies need to examine algorithms to further improve the accuracy of the IMU-based method in tasks of larger variations, as well as easy calibration procedures.

Occupational ergonomic assessment of hand pain symptoms among Bagh hand block print artisans of the handicraft textile industry in Madhya Pradesh, India

Objectives. Hand block printing is a highly repetitive and precision job involving tasks such as hitting the wooden hand block with the hands as a hammer, causing chronic mechanical trauma to the ulnar side of the palm. This study aimed to determine the prevalence of work-related hand symptoms, to identify ergonomic risks and musculoskeletal disorders (MSDs) and evidence of mechanical trauma among artisans working in Bagh print of Madhya Pradesh. Methods. Occupational risk involved in the artisan's wrist area was identified using the modified Dutch musculoskeletal questionnaire (MDMQ) and modified Boston hand evaluation questionnaire. The Boston hand evaluation questionnaire helps in the measurement of the severity of the symptoms. A direct observation study was performed to identify the chronic effects of mechanical trauma (CEMT) on artisan's hands. Results. Symptoms like pain, weakness, numbness and tingling were highly prevalent among the artisans, those with experience <3 years were more likely to report pain during working hours (p < 0.001) and those with experience >13 years were more likely to report numbness (p < 0.001) and tingling (p < 0.001). Conclusion. This study supports the evidence that the new artisans are at higher risks of reporting pain and CEMT, including fever and body pain, ultimately causing job loss.

The effects of pistol grip power tools on median nerve pressure and tendon strains

Objectives. Tendonitis and carpal tunnel syndrome are common cumulative trauma disorders that can occur with repetitive usage of pistol grip power tools. The role of reaction torque resulting in a forceful rotary displacement of the tool handle, as well as the role of applied grip force, is not clear in the development of these disorders. This study aimed to quantify the flexor tendon strains and median nerve pressure during a typical power tool operation securing a threaded fastener. Methods. Six fresh-frozen cadaver arms were made to grip a replica pistol grip power tool using static weights to apply muscle forces. A 5-Nm torque was applied to the replica power tool. The median nerve pressure and strains in the flexor digitorum profundus and superficialis tendons were measured using a catheter and strain gauges, at three wrist flexion angles. Results. The peak tendon strains were between 1.5 and 2% and were predominantly due to the grip force more than the transmitted torque. Median nerve pressure significantly increased with the wrist flexed versus extended. Conclusion. The results indicate that the contribution of the grip force to the tendon strain and median nerve pressure was greater than the contribution from the reaction torque.

Infrared thermal imaging monitoring on hands when performing repetitive tasks: An experimental study

The monitoring of infrared thermal images is reported to analyze changes in skin temperature in the hand fingers when repetitive work is performed to know which finger has a greater risk of injury, besides, the recovery time is analyzed regarding the initial temperature and its relationship with age, sex, weight, height if practice sports, and Body Mass Index (BMI) per individual. For the above, an experimental test was carried out for 10 minutes on a repetitive operation that takes place in the telecommunications industry and 39 subjects participated in which an infrared thermal image of the dorsal and palmar part of both hands was taken in periods of 5 minutes after the 10-minute test has elapsed. The results show that none of the participants recovered their initial temperature after 10 minutes of the experimental test. In addition, it was found that there is a relationship between skin temperature and sex, and that age influences the recovery of temperature. On the other hand, the thumb, index, and middle fingers have a higher risk of injury in the analyzed task. It is concluded that performing repetitive work with all the fingers of the hand does not show that all they have the same risk of injury, besides that, not all the variables studied affect the recovery of temperature and its behavior.

Forearm muscular strength and performance fatigability in orthopaedic surgeons when performing bone screw fixations

This study investigated the muscle strength and performance fatigability of the forearms in eight male orthopaedic surgeons when performing bone screw fixations. Each surgeon performed an eight-bone screws operations in a porcine femur model to simulate fractural fixation using plating technique. The pre- and post-fatigue maximum isometric forces and corresponding electromyography responses were measured to assess the forearm muscle strength loss and fatigue due to screwing. Results showed that after eight bone screws were inserted, the maximal grip force, maximal driving torque and maximal push force losses were approximately 29%, 20% and 23%, respectively. While the grip force and/or driving torque acting, both the brachioradialis and extensor carpi ulnaris had a higher percentage change of EMG than the biceps brachii. The driving forces decreased with the number of screw insertions; however, the insertion time increased parabolically with the number of screws and significantly decreased the insertion rate of the screws, indicating that forearm muscle fatigue may occur in surgeons who treat fracture fixation using more than eight bone screws.

Lean meeting buyer's expectations, enhanced supplier productivity and compliance capabilities in garment industry

Purpose

Investigate the potential of using “lean” in garment supplier factories to enhance productivity and compliance capability, so as to fulfill a buyer's expectation of lower price, shorter lead time, and higher occupational health and safety (OHS) standards.

Design/methodology/approach

By means of an intervention, lean tools integrated with OHS elements were introduced in four Bangladeshi key garment suppliers of a Danish buyer. By employing a qualitative approach, both quantitative and qualitative techniques were used to collect data on productivity, OHS, and buyer–supplier efforts.

Findings

This study demonstrates that lean tools, integrated with OHS elements, can be used to improve the productivity and compliance capabilities of supplier firms, which meet a buyers' changing demands for lower prices, shorter lead times, and higher compliance standards. This study suggests that the improvement of productivity and OHS in supplier firms through lean implementation could be a better choice for buyers than switching to new suppliers with uncertainties in productivity and delivery, as well as OHS compliance problems.

Practical implications

The findings of this study suggest that garment suppliers can benefit from implementing lean, thereby improving their capacity to meet buyers' expectations. Therefore, both suppliers and buyers have a mutual interest in the application of lean in suppliers' production facilities.

Originality/value

By considering both buyer and supplier perspectives, this research is a unique attempt to investigate the possibilities of lean implementation at the shop-floor level to meet the market challenges in the context of a developing country.

Complex couplings between joints, muscles and performance: the role of the wrist in grasping

The relationship between posture, muscle length properties and performance remains unclear, because of a lack of quantitative data. Studies on grasping tasks suggested that wrist position could favour the extrinsic finger flexor in regards to their length to maximise grip force performance. The present study aimed at providing quantitative evidence of the links between wrist posture, muscle capacities and grip capabilities. It combines experimental measurements and a musculoskeletal model including the force-length relationship of the four prime muscles used in grasping. Participants exerted their maximum grip force on a cylindrical dynamometer in four different wrist postures, including one freely chosen by participants (spontaneous). A musculoskeletal model computed the muscle force level and length from motion capture and muscle activation. Results revealed that participants exerted maximum grip force spontaneously, with a loss of force when using other postures. At muscle force and length level, grip force variation seems to be associated with all the muscles under study. This observation led to a first quantitative link between power grip, posture and muscle properties, which could provide more insight into neuromechanical interaction involved when grasping. The design of ergonomic devices could also benefit from this quantification of the relationship between wrist angle and muscle length properties.

Reorganized Force Control in Elbow Pain Patients During Isometric Wrist Extension

INTRODUCTION

Reorganized force control may be an important adaptation following painful traumas. In this study, force control adaptations were assessed in elbow pain patients. Increasing the contraction demand may overcome pain interference on the motor control and as such act as an internal control. It was hypothesized that elbow pain patients compared with controls would present greater change in the direction of force when increasing the demand of the motor task.

METHODS

Elbow pain patients (n=19) and asymptomatic participants (n=21) performed isometric wrist extensions at 5% to 70% of maximum voluntary contraction. Pressure pain thresholds were recorded at the lateral epicondyle and tibialis anterior muscle. Contraction force was recorded using a 3-directional force transducer. Participants performed contractions according to visual feedback of the task-related force intensity (main direction of wrist extension) and another set of contractions with feedback of the 3 force directions. Going from the simple to the detailed force feedback will increase the demand of the motor task. Force steadiness in all 3 dimensions and force directions were extracted.

RESULTS

Compared with controls, elbow pain patients presented lower pressure pain thresholds at both sites (P<0.05). Force steadiness was not significantly different between groups or feedback methods. The change in force direction when providing simple visual feedback in contrast with feedback of all force components at all contraction levels was greater for patients compared with controls (P<0.05).

CONCLUSION

The larger change in force direction in pain patients implies redistribution of loads across the arm as an associated effect of pain.

Evaluation of effects of anti-vibration gloves on manual dexterity

The purpose of this study was to evaluate the effects of anti-vibration gloves on manual dexterity and to explore factors affecting the manual dexterity. The manual dexterity of ten different gloves was investigated with 15 adult male subjects via performing two different dexterity tests, namely ASTM F2010 standard test and Two-Hand Turning and Placing Minnesota test. Two-factor repeated-measures analysis of variance was conducted to evaluate the main effects of glove type, test method and their interaction effect on manual dexterity. Results suggested that glove type yielded significant effect on manual dexterity (p < .001), while no significant difference was observed between test methods (p = .112). The interaction effect of glove type and test method also revealed a significant difference (p = .009). The manual dexterity decreased nearly linearly with increase in the glove thickness, which further showed a moderately significant difference on the number of drops during the tests. Practitioner Summary: Anti-vibration gloves may adversely affect manual dexterity and work precision, which may discourage their usage. This article presented a study of manual dexterity performance of anti-vibration gloves and the design factors affecting the manual dexterity. The results were discussed in view of a design guidance for improved hand dexterity, which would encourage the use of anti-vibration gloves in the workplace.

A pilot study: Exploring the musculoskeletal risk exposure associated with drying laundry using the public housing pipe-socket system amongst women in Singapore

BACKGROUND

The biomechanics of homemakers has been minimally studied. The way laundry-drying is performed in Singapore public-housing, using the pipe-socket-system (PSS), could expose the homemakers to musculoskeletal disorder risk.

OBJECTIVE

This study aims to quantify the musculoskeletal risk exposure (MRE) associated with laundry-drying amongst female homemakers using the PSS in Singapore public-housing.

METHODS

Using snowball sampling approach, five female homemakers familiar with the described laundry-drying method were recruited. The postures of the participants were analysed from video-recorded data and scored using the Rapid Entire Body Assessment (REBA).

RESULTS

This pilot study revealed very strong evidence (p = 0.001) that the participants were exposed to medium risk (REBA score 4.3) when performing this housework task.

CONCLUSIONS

Extreme awkward postures and repetitive motions were observed from the participants during the analysis. High REBA scores were frequently associated with the awkward postures adopted due to constraints of physical work space.

Evaluation of vibrant muscles over the shoulder region among workers of the hand screen printing industry

This study focuses on evaluation of the muscle activities associated with shoulder pain among workers of the hand screen printing (HSP) industry. Activities of three major muscles which showed higher muscle activity for a HSP job were observed for fatigue using surface electromyography (SEMG). The anatomical sites were chosen on the basis of a statistical survey and a visual inspection conducted before the experiment. Activities of the deltoid, teres major and infraspinatus were recorded using SEMG and the nature of muscle activities was studied for about 50 m of cloth printing. Data collected were processed using LabVIEW 2014 and the activities were analyzed using statistical tests and regression analyses. The results showed an increased risk of shoulder disorders with an increase in working time. Some of the risks which might cause disorders were predicted from the results; inspection and possible mitigations were suggested.

Confirmatory Factor and Rasch Analyses Support a Revised 14-Item Version of the Organizational, Policies, and Practices (OPP) Scale

Background The long version of the organizational, policies and practices (OPP) had a high burden and short versions were developed to solve this drawback. The 11-item version showed promise, but the ergonomic subscale was deficient. The OPP-14 was developed by adding three additional items to the ergonomics subscale. The aim of this study is to evaluate the factor structure using confirmatory factor and Rasch analyses in healthy firefighters. Methods A sample of 261 firefighters (Mean age 42 years, 95 % male) were sampled. A confirmatory factor and Rasch analyses were used to assess the internal consistency, factor structure and other psychometric characteristics of revised OPP-14. Results The OPP-14 demonstrates sound factor structure and internal consistency in firefighters. Confirmatory factor analysis confirmed the consistency of the original 4-domain structure (CFI = 0.97, TLI = 0.96, and RMSEA = 0.053). The 5 items showing misfit initially with disordered thresholds were rescored. The four subscales satisfied Rasch expectations with well target and acceptable reliability. Conclusions The OPP-14 scale shows a promising factor structure in this sample and remediated deficits found in OPP-11. This version may be preferable for musculoskeletal concerns or work applications where ergonomic indicators are relevant.

Refined clothespin relocation test and assessment of motion

BACKGROUND

Advancements in upper limb prosthesis design have focused on providing increased degrees of freedom for the end effector through multiple articulations of a prosthetic hand, wrist and elbow. Measuring improvement in patient function with these devices requires development of appropriate assessment tools.

OBJECTIVES

This study presents a refined clothespin relocation test for measuring performance and assessing compensatory motion between able-bodied subjects and subjects with upper limb impairments.

STUDY DESIGN

Comparative analysis.

METHODS

Trunk and head motions of 13 able-bodied subjects who performed the refined clothespin relocation test were compared to the motion of a transradial prosthesis user with a single degree of freedom hand.

RESULTS

There were observable differences between the prosthesis user and the able-bodied group. The assessment used provided a clear indication of the differences in motion through analysis of compensatory motion.

CONCLUSION

The refined clothespin relocation test provides additional benefits over the standard clothespin assessment and makes identification of compensatory motions easily identifiable to the researcher. While this article establishes the method for the new assessment, further validation will need to be performed with more users. Clinical relevance The refined test provides a more defined structure for the trajectory of the hand/terminal device than the standard protocol for the clothespin relocation test. This will help researchers interested in motion studies of limb segments to efficiently compare and analyse motion between able-bodied and prosthesis user groups.

Categorization of compensatory motions in transradial myoelectric prosthesis users

BACKGROUND

Prosthesis users perform various compensatory motions to accommodate for the loss of the hand and wrist as well as the reduced functionality of a prosthetic hand.

OBJECTIVES

Investigate different compensation strategies that are performed by prosthesis users.

STUDY DESIGN

Comparative analysis.

METHODS

A total of 20 able-bodied subjects and 4 prosthesis users performed a set of bimanual activities. Movements of the trunk and head were recorded using a motion capture system and a digital video recorder. Clinical motion angles were calculated to assess the compensatory motions made by the prosthesis users. The video recording also assisted in visually identifying the compensations.

RESULTS

Compensatory motions by the prosthesis users were evident in the tasks performed (slicing and stirring activities) as compared to the benchmark of able-bodied subjects. Compensations took the form of a measured increase in range of motion, an observed adoption of a new posture during task execution, and prepositioning of items in the workspace prior to initiating a given task.

CONCLUSION

Compensatory motions were performed by prosthesis users during the selected tasks. These can be categorized into three different types of compensations. Clinical relevance Proper identification and classification of compensatory motions performed by prosthesis users into three distinct forms allows clinicians and researchers to accurately identify and quantify movement. It will assist in evaluating new prosthetic interventions by providing distinct terminology that is easily understood and can be shared between research institutions.

The BASE-Program-A Multidimensional Approach for Health Promotion in Companies

Multidimensional assessments for conducting interventions are needed to achieve positive health effects within companies. BASE is an acronym, consisting of B = "Bedarfsbestimmung" (requirements); A = "Arbeitsplatzorganisation" (organisation of work); S = "Schulung des belastungsverträglichen Alltagshandelns" (coaching preventive behaviour at work); E = "Eigenverantwortung und Selbstwirksamkeit" (self-responsibility and self-efficacy). It is a prevention program designed to avoid and reduce work-related musculoskeletal diseases. It was developed to support prevention strategies within companies. It comprises aspects of health protection, ergonomics, exercise and self-efficacy. A comprehensive assessment will identify strain e.g., musculoskeletal discomforts due to body positions or psychological stress. Moreover, the general health status, preferences and barriers for participating in health promotion programs are evaluated. This analysis leads to practical and goal-oriented recommendations and interventions which suit the needs of companies and employees. These are executed onsite in real workplace situations and involve the introduction of first-hand experience in behavioural change. Therefore, this practical approach enhances the employees' acceptance and self-efficacy for health promotion. This can result in long-term health promoting behaviour. This article presents the outcome and sustainability effects of BASE in three different application fields (logistic, industrial and office workers).

CTDs and Ergonomics in Ohio

The Ohio Bureau of Workers' Compensation (BWC) provides insurance to about two-thirds of Ohio's workforce. At $17.7 billion, Ohio's workers' compensation system has the largest exclusive state fund in the nation and is the second largest underwriter of workers' compensation insurance in the country. The purpose of this paper is to 1) describe the nature and costs of cumulative trauma disorders (CTDs) in Ohio and to 2) discuss BWC's programmatic efforts to reduce the incidence and severity of the State's CTDs.

Hand therapy versus corticosteroid injections in the treatment of de Quervain's disease: A systematic review and meta-analysis

STUDY DESIGN

Systematic review with meta-analysis.

INTRODUCTION

Although corticosteroid injections are often cited as best practice in the treatment of de Quervain's disease, no reviews have compared their effectiveness to a multimodal definition of hand therapy.

PURPOSE

To compare the effectiveness of corticosteroid injections with that of i) hand therapy alone and ii) combined hand therapy/corticosteroid injection approaches in the treatment of de Quervain's disease.

METHODS

Searches of key databases were performed to identify experimental studies published between January 1950 and November 2014. Outcome measures included treatment success, pain, quality of life, and function.

RESULTS

Both corticosteroid injections and hand therapy improved pain and function from baseline, but between-group differences were not significant (across 6 studies). However, significantly more participants were treated successfully when combined orthosis/corticosteroid injection approaches were compared to i) orthoses (RR 0.53, 95% CI 0.35-0.80) and ii) injections alone (RR 0.76, 95% CI 0.64-0.89).

CONCLUSION

Combined orthosis/corticosteroid injection approaches are more effective than either intervention alone in the treatment of de Quervain's disease.

LEVEL OF EVIDENCE

1a.

Wrist rotations about one or two axes affect maximum wrist strength

Most wrist strength studies evaluate strength about one axis, and postural deviations about that same axis. The purpose of this study was to determine if wrist posture deviations about one axis (e.g. flexion/extension), or two axes (e.g. flexion/extension and pronation/supination), affect the strength about another axis (e.g. ulnar deviation). A custom-built instrumented handle was used to measure maximum static isometric torque exertions at 18 wrist postures (combinations of flexion/extension, radial/ulnar deviation, and pronation/supination). Ulnar deviation torques were highest when the wrist was in neutral. This pattern was not maintained for the other torque directions; the generated torque tended to be highest when the wrist posture was not neutral. The effects were similar for male and female subjects, although male subjects exerted significantly larger torques in all directions. This study illustrates that there is a complex relationship between wrist posture and maximal wrist torques.

A review of the current state of digital plate reading of cultures in clinical microbiology

Digital plate reading (DPR) is increasingly being adopted as a means to facilitate the analysis and improve the quality and efficiency within the clinical microbiology laboratory. This review discusses the role of DPR in the context of total laboratory automation and explores some of the platforms currently available or in development for digital image capturing of microbial growth on media. The review focuses on the advantages and challenges of DPR. Peer-reviewed studies describing the utility and quality of these novel DPR systems are largely lacking, and professional guidelines for DPR implementation and quality management are needed. Further development and more widespread adoption of DPR is anticipated.

MUSCLES IMPULSES USING TOP-LOADER TYPE OF WASHING MACHINE WITH DIFFERENT ENTRANCE HEIGHTS AND DRUM DEPTHS

This study was conducted to evaluate impulses in muscles during washing using top-loader type of washing machine and to predict the risk of musculoskeletal disorders. Experimental and virtual three-dimensional motion analyses were performed repeatedly with six healthy females using a top-loader type of washing machine at different entrance heights and drum depths. We calculated impulses of muscles from the motion data. Impulses of the latissimus dorsi and erector spinae muscles were the highest of those in the muscles.

Comparative study of upper limb load assessment and occurrence of musculoskeletal disorders at repetitive task workstations

This study explored the relationship between subjectively assessed complaints of pain in the arm, forearm and hand, and musculoskeletal load caused by repetitive tasks. Workers (n=942) were divided into 22 subgroups, according to the type of their workstations. They answered questions on perceived musculoskeletal pain of upper limbs. Basic and aggregate indices from a questionnaire on the prevalence, intensity and frequency of pain were compared with an upper limb load indicator (repetitive task index, RTI) calculated with the recently developed Upper Limb Risk Assessment (ULRA). There was relatively strong correlation of RTI and general intensity and frequency of pain in the arm, and general intensity and frequency of pain in the arm and forearm or prevalence of pain in the arm. Frequency and intensity of pain in the arm were weakly correlated. An aggregate indicator of evaluation of MSDs, which was calculated on the basis of the prevalence, intensity and frequency of pain, was to a higher degree associated with the musculoskeletal load of a task than basic evaluative parameters. Thus, such an aggregate indicator can be an alternative in comparing subjectively assessed MSDs with task-related musculoskeletal load and in establishing limit levels for that load.

Safety climate, hardiness, and musculoskeletal complaints: a mediated moderation model

This study explores the mechanisms linking the psychosocial characteristics of the workplace with employees' work-related musculoskeletal complaints. Poor safety climate perceptions represent a stressor that may elicit frustration, and subsequently, increase employees' reports of musculoskeletal discomforts. Results from an employee sample supported that when employees' perceived safety was considered a priority, they experienced less frustration and reported fewer work-related upper body musculoskeletal symptoms. Psychological hardiness, a personality trait that is indicative of individuals' resilience and success in managing stressful circumstances, moderated these relationships. Interestingly, employees with high hardiness were more affected by poor safety climate.

Analysis of the musculoskeletal loading of the thumb during pipetting--a pilot study

Previous epidemiological studies indicate that the use of thumb-push mechanical pipettes is associated with musculoskeletal disorders (MSDs) in the hand. The goal of the current study was to analyze the loading in the muscle-tendon units in the thumb during pipetting. The hand is modeled as a multi-body linkage system and includes four fingers (index, long, ring, and little finger), a thumb, and a palm segment. Since the current study is focused on the thumb, the model includes only nine muscles attached to the thumb via tendons. The time-histories of joint angles and push force at the pipette plunger during pipetting were determined experimentally and used as model input; whereas forces in the muscle-tendon units in the thumb were calculated via an inverse dynamic approach combined with an optimization procedure. Results indicate that all nine muscles have force outputs during pipetting, and the maximal force was in the abductor pollicis brevis (APB). The ratio of the mean peak muscle force to the mean peak push force during the dispensing cycle was approximately 2.3, which is comparable to values observed in grasping tasks in the literature. The analysis method and results in the current study provide a mechanistic understanding of MSD risk factors associated with pipetting, and may be useful in guiding ergonomic designs for manual pipettes.

Linear modeling of human hand-arm dynamics relevant to right-angle torque tool interaction

OBJECTIVE

A new protocol was evaluated for identification of stiffness, mass, and damping parameters employing a linear model for human hand-arm dynamics relevant to right-angle torque tool use.

BACKGROUND

Powered torque tools are widely used to tighten fasteners in manufacturing industries. While these tools increase accuracy and efficiency of tightening processes, operators are repetitively exposed to impulsive forces, posing risk of upper extremity musculoskeletal injury.

METHODS

A novel testing apparatus was developed that closely mimics biomechanical exposure in torque tool operation. Forty experienced torque tool operators were tested with the apparatus to determine model parameters and validate the protocol for physical capacity assessment.

RESULTS

A second-order hand-arm model with parameters extracted in the time domain met model accuracy criterion of 5% for time-to-peak displacement error in 93% of trials (vs. 75% for frequency domain). Average time-to-peak handle displacement and relative peak handle force errors were 0.69 ms and 0.21%, respectively. Model parameters were significantly affected by gender and working posture.

CONCLUSION

Protocol and numerical calculation procedures provide an alternative method for assessing mechanical parameters relevant to right-angle torque tool use. The protocol more closely resembles tool use, and calculation procedures demonstrate better performance of parameter extraction using time domain system identification methods versus frequency domain.

APPLICATION

Potential future applications include parameter identification for in situ torque tool operation and equipment development for human hand-arm dynamics simulation under impulsive forces that could be used for assessing torque tools based on factors relevant to operator health (handle dynamics and hand-arm reaction force).

The musculoskeletal loading profile of the thumb during pipetting based on tendon displacement

Strong evidence indicates that highly repetitive manual work is associated with the development of upper extremity musculoskeletal disorders (MSDs). One of the occupational activities that involves highly repetitive and forceful hand work is manual pipetting in chemical or biological laboratories. In the current study, we quantified tendon displacement as a parameter to assess the cumulative loading exposure of the musculoskeletal system in the thumb during pipetting. The maximal tendon displacement was found in the flexor pollicis longus (FPL) tendon. Assuming that subjects' pipetting rates were maintained constant during a period of 1 h, the average accumulated tendon displacement in the FPL reached 29 m, which is in the lower range of those observed in other occupational activities, such as typing and nail gun operations. Our results showed that tendon displacement data contain relatively small standard deviations, despite high variances in thumb kinematics, suggesting that the tendon displacements may be useful in evaluating the musculoskeletal loading profile.

Occupational diseases in Poland--an overview of current trends

INTRODUCTION

The number of occupational diseases (OD) recorded in Poland in the 1990's rapidly increased, and the number of recognized cases has steadily decreased until now. Hence, it was decided to demonstrate the trends of selected pathologies which in Poland are "underestimated" in comparison to other countries. The presented data may constitute a basis for further research into the dependence of OD on socio-economic factors.

MATERIALS AND METHODS

Occupational Disease Reporting Forms, completed and sent obligatorily by the state health inspectors to the Central Register of Occupational Diseases were used as source documents for analysis. This work analyzes changes in the incidence of chronic poisonings, asbestosis, voice organ diseases, cancers, viral hepatitis, asthma and the musculoskeletal disorders over the years 1998-2011.

RESULTS

In 1998, the total number of registered diseases reached the maximum - 12,017 cases, which fell in the subsequent years to 2,562 cases in 2011. During that period, the incidence rate decreased by 6 cases per year per 100,000 employees. A considerable decrease, exceeding 90% of cases, was observed in voice organ disorders, hearing loss, chronic poisonings and viral hepatitis. The abovementioned changes, as well as improved detection of asbestos-related diseases through implementing a medical examination program of former asbestos processing plant workers, are advantages of the current situation in the epidemiology of OD. However, the disadvantages include underestimation, in comparison to other countries, of asthma, cancer and pathologies of the musculoskeletal system.

CONCLUSION

The reported data indicates the need to assess the occupational fraction of the underestimated pathologies present in the work environment in Poland, as well as the need for studies aimed at clarifying the effect of systemic factors on identifying their occupational background.

Wrist postures and forces in tree planters during three tree unloading conditions

The aims of this study were to investigate wrist postures and forces while operating the shovel during tree planting and to determine if different tree unloading techniques result in variations in wrist postures and forces. Experienced tree planters performed the planting task in a laboratory environment for three conditions: (1) symmetric tree unloading, and asymmetric unloading resulting in (2) right-loaded planting bags and (3) left-loaded planting bags. An optoelectric system and a shovel instrumented with strain gauges captured wrist posture and forces at the wrist, respectively. Wrist extension of up to 45° was observed, and this posture, in combination with varying degrees of wrist deviation, may be a primary risk factor for musculoskeletal pain. Average resultant forces at the wrist were moderately high (>30 N) for each unloading condition, indicating increased risk for the development of repetitive strain injuries such as carpal tunnel syndrome. No significant differences in wrist posture or forces existed between unloading conditions.

PRACTITIONER SUMMARY

Wrist pain is a major musculoskeletal complaint among tree planters. This study measured wrist postures and forces at the wrist while operating the shovel during tree planting. The wrist extension observed, in combination with deviation, may be a key risk factor for musculoskeletal pain. Forces at the wrist indicate increased risk for repetitive strain injuries.

Exposure-response relationships in work-related musculoskeletal disorders in elbows and hands - A synthesis of group-level data on exposure and response obtained using uniform methods of data collection

There is a serious lack of quantitative data regarding exposure-response relationships between occupational risk factors and musculoskeletal elbow and hand disorders. This paper explores such relationships in group-level data from our earlier cross-sectional studies. Prevalence of complaints (Nordic Questionnaire) and diagnoses (physical examination) were recorded in 19 groups of female workers (1891 individuals), and 8 groups of male workers (761 individuals), with highly similar work tasks within each group. Linear regression was performed on the group means of wrist postures and angular velocity (obtained by electrogoniometers), as well as muscular load (obtained using electromyography), recorded in representative sub-samples, and psychosocial exposure (Job Content Questionnaire). To tackle within-group variations in physical exposure, sensitivity analyses were performed by bootstrapping simulations, rendering confidence intervals. The sex-adjusted slope of the regression line (β) for wrist angular velocity vs. complaints during the past 7 days was 0.6%/(°/s), (95% CI 0.3-0.9), and for carpal tunnel syndrome (CTS) 0.2%/(°/s), (0.1-0.3). For palmar flexion, p50, β over the past 7 days was 0.8%/° (0.4-1.2); for CTS 0.3%/° (0.1-0.5); β for muscular activity p90: 0.9%/%MVE (0.3-1.6), and 0.3%/%MVE (-0.03-0.6) respectively and finally β for muscular rest: -1.2%/%time (-2.4-0.03) and -0.5%/%time (-0.9 to -0.01). Relationships were also demonstrated for low job control, job strain and isostrain. Women exhibited a higher prevalence of complaints than men. In conclusion, we have established quantitative exposure-response relationships between physical work load and elbow/hand disorders. Wrist angular velocity was the most consistent risk factor.

A comparative ergonomic study of work-related upper extremity musculo skeletal disorder among the unskilled and skilled surgical blacksmiths in West Bengal, India

OBJECTIVE

The main aim of the study was to determine the nature and extent of work-related upper extremity musculoskeletal disorders (MSDs) and physiological stress among the blacksmiths involved in surgical instrument industry.

MATERIALS AND METHODS

In the present investigation, 50 male blacksmiths of each skilled and unskilled groups of the forging section had been selected. For the symptom survey, a questionnaire on discomfort symptoms was performed. Repetitiveness of work and hand grip strength of both the groups were measured.

RESULTS

It was revealed that upper limb MSD was a major problem among both group of blacksmith, primarily involving the hand, wrist, fingers, and shoulder. From this study it was found that 66% (33) skilled and 80% (40) unskilled blacksmith workers are feeling discomfort. The most commonly affected regions among the skilled and unskilled blacksmith workers were lower back (skilled 65% and unskilled 80%), neck (skilled 60% and unskilled 80%), and hand (skilled 50% and unskilled).

Force, frequency and gripping alter upper extremity muscle activity during a cyclic push task

Factors, such as high repetition, high force and gripping play a role in the development of upper extremity work-related musculoskeletal disorders. The purpose of this study was to systematically examine the effects of push load and frequency on muscle activity with and without concurrent gripping. A total of 10 men and 10 women performed a cyclic bimanual pushing task. All combinations of three push loads (1 kg, 2 kg, 4 kg), three frequencies (4/min, 8/min, 16/min) and two grip conditions (no required grip and 30% of maximum grip force) were performed in randomised order. The muscle activity of the upper arm and shoulder complex reflected both frequency and load, often with significant interactions, thus may be better described by workload, the product of force and frequency. In the forearm, muscle activities were generally low but adding a submaximal grip superseded the effects of push load, with the activity reflecting frequency and grip.

PRACTITIONER SUMMARY

Force and frequency are important risk factors for upper extremity disorders. We found that upper extremity muscle activity responds to workload (force × frequency) in a complex way which may be superseded if a grip is present. This electromyographic study provides physiological insights to muscular loading as basis for a variety of workplace disorders.

Evaluation of the ShapeTape for studying biomechanics in the workplace

Motion capture systems may be difficult to use in harsh environments such as a poultry plant, and therefore should be self-contained, portable, unobtrusive, and not interfere with or be degraded by plant machinery or processes. The purpose of this study was to evaluate the validity, reliability and accuracy of the ShapeTape system as a potential solution. This was accomplished by comparing kinematic data from the ShapeTape against the Vicon system. Subjects performed cyclical movements along a plane angled 45° up from the horizontal using their right arms. Results revealed that the ShapeTape kinematic data was significantly larger than the Vicon data, yet statistically reliable.

Effects of computer keyboarding on ultrasonographic measures of the median nerve

BACKGROUND

Keyboarding is a highly repetitive daily task and has been linked to musculoskeletal disorders of the upper extremity. However, the effect of keyboarding on median nerve injuries is not well understood. The purpose of this study was to use ultrasonographic measurements to determine whether continuous keyboarding can cause acute changes in the median nerve.

METHODS

Ultrasound images of the median nerve from 21 volunteers were captured at the levels of the pisiform and distal radius prior to and following a prolonged keyboarding task (i.e., 1 hr of continuous keyboarding). Images were analyzed by a blinded investigator to quantify the median nerve characteristics. Changes in the median nerve ultrasonographic measures as a result of continuous keyboarding task were evaluated.

RESULTS

Cross-sectional areas at the pisiform level were significantly larger in both dominant (P = 0.004) and non-dominant (P = 0.001) hands following the keyboarding task. Swelling ratio was significantly greater in the dominant hand (P = 0.020) after 60 min of keyboarding when compared to the baseline measures. Flattening ratios were not significantly different in either hand as a result of keyboarding.

CONCLUSION

We were able to detect an acute increase in the area of the median nerve following 1 hr of keyboarding with a computer keyboard. This suggests that keyboarding has an impact on the median nerve. Further studies are required to understand this relationship, which would provide insight into the pathophysiology of median neuropathies such as carpal tunnel syndrome.

Mudanças nas formas de produção na indústria e a saúde dos trabalhadores

Buscou-se identificar possíveis determinantes de efeitos na saúde dos trabalhadores em indústrias plásticas. Descreve-se a organização da produção, trabalhadores e maquinário das áreas de produção e manutenção de catorze indústrias plásticas da Região Metropolitana de Salvador. Coletaram-se dados sobre política de desenvolvimento de cada empresa, mercado, procedimentos operacionais, exigências de produção e de qualidade e as regras formais da organização do trabalho. Implementam-se técnicas de gestão com forte exigência de redução do tempo da produção. O aumento do ritmo do trabalho, a redução de pausas e uma situação de alta demanda cognitiva impõem aos trabalhadores posturas anômalas para execução das tarefas com movimentos repetitivos. Demandas físicas e psicossociais (trabalho repetitivo, baixo controle dos trabalhadores sobre suas tarefas, pressão de tempo e insatisfação no trabalho) compõem um universo de condições desfavoráveis para a saúde de trabalhadores. Mudanças na gestão da produção, de pessoal e dos negócios impõem novas exigências aos trabalhadores no desenvolvimento das tarefas, configurando novos fatores de risco para a saúde dos trabalhadores.

Tarefas repetitivas sob pressão temporal: os distúrbios musculoesqueléticos e o trabalho industrial

Realizou-se estudo ergonômico a fim de caracterizar as tarefas repetitivas e as demandas psicossociais no trabalho industrial em empresa do ramo plástico da Região Metropolitana de Salvador (BA). Realizaram-se observações globais das tarefas nas primeiras visitas à empresa, visando conhecer a organização geral, o funcionamento da produção e os determinantes das tarefas. Observaram-se nesta etapa que as exigências temporais na execução das tarefas implicavam demandas psicossociais e demandas físicas, em especial, os movimentos repetitivos. Na segunda etapa, realizaram-se observações sistemáticas, com entrevistas simultâneas. Mediu-se a duração dos ciclos básicos das tarefas na moldagem/acabamento das embalagens e registrou-se a ocorrência de perturbações que exigiam das trabalhadoras sua regulação. Identificaram-se variabilidades do trabalho, evidenciando como são geradas as demandas extras e como as exigências cognitivas e físicas podem ser exacerbadas pela pressão temporal. A insuficiência dos meios de trabalho, as exigências temporais da gestão da produção e uma organização do trabalho caracterizada pelo baixo controle conformam uma situação em que a continuidade da produção apenas é possível à custa de hipersolicitação do corpo das trabalhadoras.

Upper limb discomfort profile due to intermittent isometric pronation torque at different postural combinations of the shoulder-arm system

Twenty-seven right-handed male university students participated in this study, which comprised a full factorial model consisting of three forearm rotation angles (60% prone and supine and neutral range of motion), three elbow angles (45 degrees , 90 degrees and 135 degrees ), three upper arm angles (45 degrees flexion/extension and neutral), one exertion frequency (15 per min) and one level of pronation torque (20% maximum voluntary contraction (MVC) relative to MVC at each articulation). Discomfort rating after the end of each 5 min treatment was recorded on a visual analogue scale. Results of a repeated measures analysis of covariance on discomfort score, with torque endurance time as covariate, indicated that none of the factors was significant including torque endurance time (p = 0.153). An initial data collection phase preceded the main experiment in order to ensure that participants exerted exactly 20% MVC of the particular articulation. In this phase MVC pronation torque was measured at each articulation. The data revealed a significant forearm rotation angle effect (p = 0.001) and participant effect (p = 0.001). Of the two-way interactions, elbow*participant (p = 0.004), forearm*participant (p = 0.001) and upper arm*participant (p = 0.005) were the significant factors. Electromyographic activity of the pronator teres and biceps brachii muscles revealed no significant change in muscle activity in most of the articulations. Industrial jobs involving deviated upper arm postures are typical in industry but have a strong association with injury. Data from this study will enable better understanding of the effects of deviated upper arm postures on musculoskeletal disorders and can also be used to identify and control high-risk tasks in industry.

Repetitive task indicator as a tool for assessment of upper limb musculoskeletal load induced by repetitive task

A unified repetitive task indicator (RTI) has been proposed, characterizing the upper limb load resulting from repetitive work. Within RTI, the work task is described using parameters which refer to the duration of particular sequences of the work cycle and force exerted, taking into account the posture of the upper limb. On the basis of theoretical and experimental studies, undertaken by the author and on the basis of results of experimental studies conducted in other international research laboratories, available in the literature, an analysis was conducted with the aim of developing and verifying the RTI. A comparison of the RTI with indicators of internal load was performed for eight published study cases. The experimental study cases used for verification purposes were conducted for various variants of load (various types and levels of the external force and duration of cycle periods) and for various physiological indicators of internal load. Strong correlations between RTI and indicators of internal load expressed by the unified indicator (IL), showed considerable credibility of the RTI. Results of the verification are noteworthy, given the wide range of cases examined, differing in terms of the conditions under which they were done, the population examined and internal load indicators used. Thus, this analysis indicates that the proposed RTI reflects well the upper limb load occurring as a result of performing repetitive work.