Relationships and Mechanisms Between Occupational Risk Factors and Distal Upper Extremity Disorders

Ancient Egyptian scribes and specific skeletal occupational risk markers (Abusir, Old Kingdom)

Men with writing proficiency enjoyed a privileged position in ancient Egyptian society in the third millennium BC. Research focusing on these officials of elevated social status ("scribes") usually concentrates on their titles, scribal statues, iconography, etc., but the individuals themselves, and their skeletal remains, have been neglected. The aim of this study is to reveal whether repetitive tasks and maintained postures related to scribal activity can manifest in skeletal changes and identify possible occupational risk factors. A total of 1767 items including entheseal changes, non-metric traits, and degenerative changes were recorded from the human remains of 69 adult males of well-defined social status categories from the necropolis at Abusir (2700-2180 BC). Statistically significant differences between the scribes and the reference group attested a higher incidence of changes in scribes and manifested themselves especially in the occurrence of osteoarthritis of the joints. Our research reveals that remaining in a cross-legged sitting or kneeling position for extended periods, and the repetitive tasks related to writing and the adjusting of the rush pens during scribal activity, caused the extreme overloading of the jaw, neck and shoulder regions.

A follow-up study of vibration-induced injuries in workers exposed to transient and high frequency vibrations

BACKGROUND

In a previous study from 2018, 38 wheel loader assembly workers were examined, showing high exposures to transient and high-frequency vibrations. After the investigation, preventive measures were immediately implemented to reduce the vibration exposure. In 2022, a follow-up study was carried out to examine the effect of these measures.

METHODS

The follow-up study included 35 (27 men and 8 women) of the original 38 workers. They were divided into two groups, 24 workers with ongoing vibration exposure and 11 workers, not vibration exposed since 2018. All participants completed a questionnaire and underwent a thorough examination, including several neurophysiological tests and a comprehensive assessment of musculoskeletal symptoms. The questionnaire responses and on-site vibration level measurements formed the basis for the individual vibration exposure assessment.

RESULTS

In 2018, clear differences were noted between the two groups regarding vibration perception thresholds (VPT), needle test, 2-PD (2-point discrimination), and monofilament test with deviating results in the unexposed group. The difference between the two groups was significantly smaller at the follow-up examination in 2022, where differences remained for VPT and monofilament tests, with deviating test results in the unexposed group. When comparing variable values between 2018 and 2022 within the exposed and unexposed groups, respectively, the unexposed group showed mostly unchanged values, while a deterioration was observed for VPT, needle test and temperature sensitivity test among the exposed workers during follow-up. The prevalence of VWF (Vibration white fingers) was around 30-40% and neuropathy around 75% among exposed workers during follow-up compared to about 60% and 85% respectively, in the unexposed group.

CONCLUSION

The overall categorization of white fingers and neuropathy, according to the Stockholm Workshop Scale, remained largely unchanged in both study groups from 2018 to 2022. The introduction of cost-effective and relatively simple preventive measures may have contributed to this result. Throughout the follow-up period, the number of exposed workers who developed musculoskeletal disorders and newly reported cases of vibration injuries at the factory decreased. Without this preventive program, increased vascular and nerve symptoms would most likely have occurred during follow-up due to continued vibration exposure.

Biomechanical requirements of meat cutting tasks: A pilot study quantifying tasks sustainability and assistance required at the wrist

The meat processing industry is particularly affected by distal upper limb musculoskeletal disorders. This pilot study aims at proposing a methodology able to quantify biomechanical requirements of meat cutting tasks at butchers' dominant wrist and, when necessary, at estimating the assistance needed to reach sustainability. Six professional butchers repeatedly cut pieces of pork. Joint angles were recorded using a motion capture system, cutting forces using an instrumented knife. Sustainability was computed by the maximal acceptable effort method. Assistance requirements were computed for isolated stressful exertions and for overall work cycle sustainability. Five butchers exceeded the sustainability threshold for wrist flexion. Ulnar or radial deviation torques were excessive for 2 and 3 of them, respectively. Extension torques were sustainable. The peak assistive torque for isolated exertions was at most 1.1Nm, 1.6Nm and 1.1Nm, and the percentage of assistance for overall sustainability was at most 60%, 56% and 56% for wrist flexion, ulnar and radial deviation, respectively.

Design of a wearable shoulder exoskeleton robot with dual-purpose gravity compensation and a compliant misalignment compensation mechanism

This paper presents the design and validation of a wearable shoulder exoskeleton robot intended to serve as a platform for assistive controllers that can mitigate the risk of musculoskeletal disorders seen in workers. The design features a four-bar mechanism that moves the exoskeleton's center of mass from the upper shoulders to the user's torso, dual-purpose gravity compensation mechanism located inside the four-bar's linkages that supports the full gravitational loading from the exoskeleton with partial user's arm weight compensation, and a novel 6 degree-of-freedom (DoF) compliant misalignment compensation mechanism located between the end effector and the user's arm to allow shoulder translation while maintaining control of the arm's direction. Simulations show the four-bar design lowers the center of mass by  cm and the kinematic chain can follow the motion of common upper arm trajectories. Experimental tests show the gravity compensation mechanism compensates gravitational loading within  Nm over the range of shoulder motion and the misalignment compensation mechanism has the desired 6 DoF stiffness characteristics and range of motion to adjust for shoulder center translation. Finally, a workspace admittance controller was implemented and evaluated showing the system is capable of accurately reproducing simulated impedance behavior with transparent low-impedance human operation.

Influence of Force-Length Relationship and Task-Specific Constraints on Finger Force-Generating Capacities

Grip strength loss in extended and flexed wrist postures has been explained by reduced force-generating capacities of extrinsic finger flexor resulting from non-optimal length, owing to the force-length relationship. Recent works suggested that other muscles, especially wrist extensors, participate in this grip strength loss. The objective of this study was to clarify the role of the force-length relationship in finger force production. 18 participants performed maximal isometric finger force production during pinch grip (Pinch) and four-finger pressing (Press) tasks in four different wrist postures (extended, flexed, neutral, spontaneous). The maximum finger force (MFF), finger and wrist joint angles, as well as activation of four muscles were determined using dynamometry, motion capture, and electromyography. The force and length of the four muscles were estimated from joint angles and muscle activation using a musculoskeletal model. MFF decreased for flexed wrist during Pinch but remained stable across wrist postures during Press. The results suggested that the loss of pinch grip force in deviated wrist posture is partially related to force-length relationship of finger extensors. In opposition, MFF during Press was not influenced by the modulation of muscle capacities but was probably first limited by mechanical and neural factors related to finger interdependence.

Electromyography-informed musculoskeletal modeling provides new insight into hand tendon forces during tennis forehand

Lateral epicondylitis, also known as tennis elbow, is a major health issue among tennis players. This musculo-skeletal disorder affects hand extensor tendons, results in substantial pain and impairments for sporting and everyday activities and requires several weeks of recovery. Unfortunately, prevention remains limited by the lack of data regarding biomechanical risk factors, especially because in vivo evaluation of hand tendon forces remains challenging. Electromyography-informed musculo-skeletal modeling is a noninvasive approach to provide physiological estimation of tendon forces based on motion capture and electromyography but was never applied to study hand tendon loading during tennis playing. The objective of this study was to develop such electromyography-informed musculo-skeletal model to provide new insight into hand tendon loading in tennis players. The model was tested with three-dimensional kinematics and electromyography data of two players performing forehand drives at two-shot speeds and with three rackets. Muscle forces increased with shot speed but were moderately affected by racket properties. Wrist prime extensors withstood the highest forces, but their relative implication compared to flexors depended on the player-specific grip force and racket motion strategy. When normalizing wrist extensor forces by shot speed and grip strength, up to threefold differences were observed between players, suggesting that gesture technique, for example, grip position or joint motion coordination, could play a role in the overloading of wrist extensor tendons. This study provided a new methodology for in situ analysis of hand biomechanical loadings during tennis gesture and shed a new light on lateral epicondylitis risk factors.

Utilizing Motion Capture Systems for Instrumenting the OCRA Index: A Study on Risk Classification for Upper Limb Work-Related Activities

In the search to enhance ergonomic risk assessments for upper limb work-related activities, this study introduced and validated the efficiency of an inertial motion capture system, paired with a specialized platform that digitalized the OCRA index. Conducted in a semi-controlled environment, the proposed methodology was compared to traditional risk classification techniques using both inertial and optical motion capture systems. The inertial method encompassed 18 units in a Bluetooth Low Energy tree topology network for activity recording, subsequently analyzed for risk using the platform. Principal outcomes emphasized the optical system's preeminence, aligning closely with the conventional technique. The optical system's superiority was further evident in its alignment with the traditional method. Meanwhile, the inertial system followed closely, with an error margin of just ±0.098 compared to the optical system. Risk classification was consistent across all systems. The inertial system demonstrated strong performance metrics, achieving F1-scores of 0.97 and 1 for "risk" and "no risk" classifications, respectively. Its distinct advantage of portability was reinforced by participants' feedback on its user-friendliness. The results highlight the inertial system's potential, mirroring the precision of both traditional and optical methods and achieving a 65% reduction in risk assessment time. This advancement mitigates the need for intricate video setups, emphasizing its potential in ergonomic assessments.

Correlations between Ratings and Technical Measurements in Hand-Intensive Work

An accurate rating of hand activity and force is essential in risk assessment and for the effective prevention of work-related musculoskeletal disorders. However, it is unclear whether the subjective ratings of workers and observers correlate to corresponding objective technical measures of exposure. Fifty-nine workers were video recorded while performing a hand-intensive work task at their workplace. Self-ratings of hand activity level (HAL) and force (Borg CR10) using the Hand Activity Threshold Limit Value^® were assessed. Four ergonomist observers, in two pairs, also rated the hand activity and force level for each worker from video recordings. Wrist angular velocity was measured using inertial movement units. Muscle activity in the forearm muscles flexor carpi radialis (FCR) and extensor carpi radialis (ECR) was measured with electromyography root mean square values (RMS) and normalized to maximal voluntary electrical activation (MVE). Kendall's tau-b correlations were statistically significant between self-rated hand activity and wrist angular velocity at the 10th, 50th, and 90th percentiles (0.26, 0.31, and 0.23) and for the ratings of observers (0.32, 0.41, and 0.34). Significant correlations for force measures were found only for observer-ratings in five of eight measures (FCR 50th percentile 0.29, time > 10%MVE 0.43, time > 30%MVE 0.44, time < 5% -0.47) and ECR (time > 30%MVE 0.26). The higher magnitude of correlation for observer-ratings suggests that they may be preferred to the self-ratings of workers. When possible, objective technical measures of wrist angular velocity and muscle activity should be preferred to subjective ratings when assessing risks of work-related musculoskeletal disorders.

Biomechanical Risk Factors of the Upper Limbs' Musculoskeletal Disorders among Carpet Weavers in Tunisia: Semi-Quantitative Ergonomic Assessment

Background

Musculoskeletal disorders are one of the most common occupational health problems and one of the leading causes of temporary disability. This study aimed to assess the biomechanical constraints of upper limb musculoskeletal disorders associated with Tunisian weavers' tasks.

Methodology

An ergonomic approach was adopted with a representative sample of Tunisian weavers. First, the activity was observed mainly for identifying tasks and sub-tasks. Then, the biomechanical constraints were assessed based on the Borg scale and the software analyses and encoding of the 2,000 images extracted from the activity video recordings. These analyses were done with the ERGOROM software.

Results

Four main tasks were identified (warping of the loom, weaving itself, beating up, and finishing). As for the subtasks, the six most important were thread coiling, shedding and picking, beating up the weft, knotting, cutting, and shearing. Semi-quantitative analysis revealed that weavers spent most of their working time in the constrained neck and upper limb postures. Shoulders were in flexion/abduction during 68.6% of the activity and pinch grip was spread over 83.3% of the working time. Furthermore, elbows and wrists were highly concerned by elevated gestural variability scores. The estimated deployed strength was "medium" to "strong" in 50% to nearly 80% of cases.

Conclusion

According to the results, in carpet weavers, exposure to biomechanical constraints at risk of musculoskeletal disorders was high for the various joints and parts of the upper limbs. It is, therefore, necessary to carry out interventional studies for the development of ergonomic hand tools and workstations adapted to the traditional weaver activity.

Effects of sex and age on work-related upper extremity musculoskeletal disorders in Ontario, Canada

BACKGROUND

Effective targeting of workplace upper extremity musculoskeletal disorder (MSD) prevention strategies requires the identification of demographic groups most at risk. Workers' compensation data provides an effective means of surveillance of MSDs at the population level.

OBJECTIVE

The primary purpose of this study was to identify the effects of age and sex on rates of tendon injuries of the wrist and hand, carpal tunnel syndrome (CTS), epicondylitis, and soft tissue shoulder injuries in Ontario, Canada between 2000-2019 using workers' compensation data from the Association of Workers Compensation Boards of Canada (AWCBC).

METHODS

Age and sex specific rates of lost-time injury claims from the four identified injury categories as well as "non-specific" upper extremity MSDs which did not fit into the four categories were calculated by standardizing injury claim totals with "at-risk" population estimates from the Canada Labour Force Survey. A multiple regression analysis was used to analyze the effects of age and sex on rates of specific injury claims.

RESULTS

Statistically significant age and sex effects were identified for rates of claims from tendon injuries of the wrist and hand, CTS, and shoulder injuries, while only age effects were significant for epicondylitis. Between 2000-2019, rates of claims from the four injury categories studied and the magnitude of the age and sex effects declined substantially over time.

CONCLUSION

Detailed surveillance of workplace ergonomic hazards in Ontario workplaces is needed to determine what is causing rates of upper extremity claims to decline.

The prevalence and risk factors of work related musculoskeletal disorders among electronics manufacturing workers: a cross-sectional analytical study in China

OBJECTIVES

To describe the prevalence of self-reported musculoskeletal disorders among workers in the electronics manufacturing industry and to investigate the relations between work-related musculoskeletal disorders (WMSDs) and work-related variables.

METHODS

An interview-based questionnaire survey was carried out in thirty electronics manufacturing factories in China in 2018. The prevalence of WMSDs was estimated using the modified Nordic Musculoskeletal Questionnaire (NMQ). A multivariate logistic regression model was applied to evaluate the effects of risk factors on WMSDs on multiple body parts.

RESULTS

The 12-month prevalence of WMSDs among participants was 40.6%, and the common body sites affected were the neck (26.8%), shoulder (22.8%), upper back (14.9%), and lower back (14.8%). The results of logistic regression showed that female adults, > 5 job tenure and work-related factors (including awkward posture, lifting or carrying weights, excessive repetition, prolonged sitting, monotonous work and working under conditions of cold or temperature variations) led to a higher risk of WMSDs on most body parts. Upper back, wrist/hand and elbow pain levels were significantly higher for workers with vibration. However, more frequently, physical exercise was a protective factor against WMSDs on most body parts except the upper back, leg and knee.

CONCLUSIONS

The study indicates a high prevalence of musculoskeletal pain among the electronics manufacturing industry in China. Different personal and work factors are related to the occurrence of WMSD on different body parts. Preventive measures should be implemented based on the characteristics of WMSD in the electronic manufacturing industry. Furthermore, the training and intervention guidance of ergonomic hazards in the workplace need to be strengthened by understanding the impact of bad posture, avoiding long-term sitting posture and increasing physical activities.

The effect of rigid tape on wrist postures during tree planting

Taping has been suggested to reduce the incidence of tendinopathy in tree planters. However, the ability of taping to reduce wrist postures during planting has not yet been formally evaluated. The primary aim was to test the effect of rigid taping on wrist postures during tree planting tasks. Eleven tree planters planted up to 50 trees in three conditions: no-tape (NT), tape-on-the-dorsum-of-the-hand (T1) and tape-on-the-thumb (T2) in a randomised cross-over, within-participant, repeat-measures design. Electrogoniometers (EG) recorded continuous wrist postures. Digital video recordings were used to segment EG traces of each planting cycle (one planted tree) into 4 kinematically distinct Phases. The tree and shovel wrist were analysed separately. Tree-wrist peak ulnar deviation and frequency of shovel-wrist awkward frontal plane postures were significantly reduced in the T2 condition. Taping may be effective at reducing non-neutral postures and should be researched further to determine its effectiveness in reducing tree planting injuries.Practitioner summary: The effect of rigid taping on wrist postures during tree planting has not yet been formally evaluated. A randomised cross-over, within-participant, repeat measures design was used to evaluate the effect of rigid taping on wrist postures during planting. Thumb rigid taping appeared to reduce wrist range of motion during planting. KEY POINTSTaping of the thumb reduced peak ulnar deviation of the tree wrist and frequency of awkward frontal plane postures of the shovel wrist.While taping of the dorsum of the hand appeared to be more restrictive, it did not significantly reduce wrist movement; this is likely because only its effect on sagittal plane posture was assessed which had a higher variance.Upon application, tape appeared to restrict voluntary movement patterns, decreased voluntary grip force exertion and physically restrain wrist movement.Overall, rigid tape was found to be an acceptable intervention for the tree planting occupation, with financial costs and perceived effort identified as the primary barriers to acceptability.

Reliability Analysis of Observation-Based Exposure Assessment Tools for the Upper Extremities: A Systematic Review

(1) Background: The objectives of this systematic review were to (i) summarize the results of studies evaluating the reliability of observational ergonomics exposure assessment tools addressing exposure to physical risk factors associated with upper extremity musculoskeletal disorders (MSDs), and (ii) identify best practices for assessing the reliability of new observational exposure assessment tools. (2) Methods: A broad search was conducted in March 2020 of four academic databases: PubMed, Science Direct, Ergonomic Abstracts, and Web of Science. Articles were systematically excluded by removing redundant articles, examining titles and abstracts, assessing relevance to physical ergonomics and the upper extremities, and article type. (3) Results: Eleven articles were included in the review. The results indicated no singular best practice; instead, there were multiple methodological approaches researchers chose to use. Some of the significant variations in methodologies include the selection of reliability coefficients, rater and participant selection, and direct vs. digital observation. (4) Conclusion: The findings serve as a resource summarizing the reliability of existing observational risk assessment tools and identify common methods for assessing the reliability of new observational risk assessment tools. Limitations of this review include the number of databases searched, the removal of truncation symbols, and the selection of keywords used for the initial search.

Facing symptoms and limitations: a qualitative study of women with carpal tunnel syndrome

BACKGROUND

Carpal tunnel syndrome (CTS) is a neuropathic pain condition characterised by pain, paresthesia, loss of strength and disability.

OBJECTIVE

To explore the experiences of women with CTS regarding the management of symptoms and limitations.

METHODS

A qualitative phenomenological study was conducted. Women with a clinical and electromyographic diagnosis of CTS recruited from the Neurology Department of a Public Hospital were included. Purposeful sampling was performed. Data were collected using in-depth interviews and researchers' field notes. Analysis proposed by Giorgi was used.

RESULTS

A total of 18 women with CTS were included. Two themes emerged: a) Living with CTS symptoms and limitations: describing the symptoms experienced, triggers of their symptoms and how they define CTS. Also, describing the difficulties that they experience on a daily basis, at home when handling tools, communicating, driving, and at work; and b) developing daily strategies for managing limitations: developing potential daily strategies to overcome daily limitations and/or compensate for them, and seeking professional help.

CONCLUSIONS AND SIGNIFICANCE

Current results provide insight on how symptoms and daily limitations are experienced by a group of women with CTS. These findings could help occupational therapists to understand the day-to-day difficulties and the reasons for developing certain strategies.

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.

Anthropometrics and electromyography as predictors for maximal voluntary isometric wrist torque: Considerations for ergonomists

The purpose of this study was to evaluate anthropometry and forearm muscle activity as predictors of maximal isometric wrist torque. Thirteen anthropometric measures, forearm electromyography from flexor carpi radialis (FCR) and extensor carpi radialis (ECR), and maximal isometric wrist flexion/extension torque were obtained from 25 male participants. Pearson correlation coefficients assessed relationships between peak isometric torque and: (1) anthropometrics, (2) FCR and ECR activation, (3) FCR/ECR antagonist/agonist coactivation ratios. Based on significant correlations, linear regression equations were developed (SPSS v.25; p < 0.05). Hand thickness, forearm circumference and ECR activation or hand thickness, elbow circumference, FCR activation and body weight were most highly correlated with extension or flexion torque, respectively. Hand thickness, forearm circumference, and ECR activation (R² = 54.5%; p = 0.001) and hand thickness, elbow circumference, FCR activation (R² = 68.3%; p < 0.001) explained similar variance in torque regressions as did the addition of body weight to extension (R² = 58.0%; p = 0.001) and flexion (R² = 69.9%; p < 0.001) torque regression equations, respectively. Circumference measurements, a pseudo for muscle size, and activation amplitude influenced wrist force output more than limb length or coactivation.

Repetitive and forceful movements of the hand as predictors of treatment for pain in the distal upper extremities

Objective

To investigate repetitive movements and the use of hand force as causes of treatment for distal upper extremities musculoskeletal disorders

Methods

A cohort of 202 747 workers in a pension health scheme from 2005 to 2017 in one of 17 jobs (eg, office work, carpentry, cleaning) was formed. Representative electro-goniometric measurements of wrist angular velocity as a measure for repetition and expert-rated use of hand force were used in a job exposure matrix (JEM). Job titles were retrieved from the Danish registers. Outcome was first treatment in the distal upper extremities. In a Poisson regression model, incidence rate ratios (IRRs) of treatment were adjusted for age, calendar-year, diagnosis of rheumatoid arthritis and arm fractures. In further analyses, wrist velocity or hand force was added.

Results

In men, wrist velocity had an IRR of 1.48 (95% CI 1.15 to 1.91) when the highest exposure level was compared with the lowest but with no clear exposure-response pattern. The effect became insignificant when adjusted for hand force. Hand force had an IRR of 2.65 (95% CI 2.13 to 3.29) for the highest versus the lowest exposure with an exposure-response pattern, which remained after adjustment for wrist velocity. Among women, no increased risk was found for hand force, while wrist velocity showed a significantly protective association with treatment.

Conclusions

In men, occupational exposure to hand force more than doubled the risk of seeking treatment. The results for exposure to repetition were less clear. In women, we could not find any indications of an increased risk neither for force nor for repetition.

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.

Effect of Force, Posture, and Repetitive Wrist Motion on Intraneural Blood Flow in the Median Nerve

OBJECTIVES

Pinching, deviated wrist postures, and repetitive motion are risk factors for carpal tunnel syndrome. Hypervascularization of the median nerve and increased intraneural blood flow proximal to the carpal tunnel result in finger force and deviated wrist postures. The purpose of this study was to determine the effects of pinching with and without force, wrist posture, and repetitive wrist motion on intraneural blood flow in the median nerve.

METHODS

Eleven healthy and 11 carpal tunnel syndrome-symptomatic individuals completed 3 sections of this study: 15 pinch posture force trials, 3 repetitive wrist motion trials, and 3 static wrist posture trials. Intraneural blood flow (centimeters per second) was measured with pulsed wave Doppler ultrasound during each trial. Transverse B-mode images obtained from static trials were used to calculate the median nerve cross-sectional area and circumference.

RESULTS

An analysis of variance statistical analysis revealed significant main effects of pinch posture force (F_4,80 = 21.397; P < .001) and wrist posture (F_2,40 = 14.545; P < .001). Intraneural blood flow velocities were significantly greater when 6 N of force was applied by the thumb, finger, or pinch compared to no applied force in the same postures. Intraneural blood flow velocities were higher at 30° wrist flexion (mean ± SD, 2.24 ± 0.42 cm/s) than neutral (2.06 ± 0.45 cm/s) and 30° wrist extension (1.97 ± 0.46 cm/s). No changes were found in response to repetitive wrist motion.

CONCLUSIONS

Flexed wrists as well as applied finger and thumb forces increase median nerve blood flow at the entry to the carpal tunnel, which may negatively affect the median nerve.

Prevalence and risk factors of self-reported wrist and hand symptoms and clinically confirmed carpal tunnel syndrome among office workers in China: a cross-sectional study

Background

Carpal tunnel syndrome (CTS) is a common cause of pain, numbness and tingling in the wrist and hand region and is associated with repetitive wrist and hand use in office workers. However, scarce knowledge exists about the epidemiology of clinically confirmed CTS among Chinese office workers. This study aimed to investigate the prevalence of wrist/hand symptoms and CTS in office workers in China and to identify associated risk factors.

Methods

A cross-sectional survey was carried out in a metropolitan city in China involving 969 respondents (aged 17–49 years) from 30 workplaces. A questionnaire was distributed to each participant to collect their demographic, work-related physical and psychosocial factors, and wrist and hand symptoms. The wrist and hand pain/numbness symptoms were marked on a body chart and the nature and intensity of symptoms, nocturnal symptoms, as well as aggravating activities were also recorded. Clinically confirmed CTS cases were screened based on the history, Phalen’s test, Tinel Sign and skin sensation testing among symptomatic respondents. Logistic regression was employed to estimate the odds ratio (OR) and 95% confidence interval (95% CI) for the occurrence of self-reported wrist and hand symptoms and clinically confirmed CTS.

Results

The clinically confirmed CTS prevalence was 9.6%. The prevalence of wrist and hand symptoms were 22 and 15%, respectively. Frequently working in pain was associated with higher odds of CTS. Multivariate modelling adjusted for age and gender showed that prolonged computer use time and working without breaks were associated with presence of wrist/hand symptoms (adjusted ORs: 1.11 (95% CI 1.02–1.22) and 1.88 (95% CI 1.12–3.14)). Educational level was inversely associated with CTS and smoking was associated with wrist/hand complaints (adjusted OR: 2.20 (95% CI 1.19–4.07)).

Conclusions

The prevalence of work-related clinically confirmed CTS symptoms among young office workers in China is high. Frequently working in pain is closely associated with clinically confirmed CTS. Intense computer use and no breaks at work are associated with wrist and hand symptoms.

Development of a musculoskeletal model of the wrist to predict frictional work dissipated due to tendon gliding resistance in the carpal tunnel

Carpal tunnel syndrome is an entrapment neuropathy that has been associated with the aggravation of tendon gliding resistance due to forceful, high velocity, awkwardly angled, and repetitive wrist motions. Cadaveric and epidemiological studies have shown that combinations of these risk factors have a more than additive effect. The aim of the current study was to develop a musculoskeletal model of the wrist that could evaluate these risk factors by simulating frictional work dissipated due to the gliding resistance of the third flexor digitorum superficialis tendon. Three flexion angle zones, three extension angle zones, five levels of task repetitiveness, and five levels of task effort were derived from ergonomic standards. Of the simulations performed by systematically combining these parameters, the extreme wrist flexion zone, at peak task repetitiveness and effort, dissipated the most frictional work. This zone dissipated approximately double the amount of frictional work compared to its equivalent zone in extension. For all motions, a multiplicative effect of the combination of task repetitiveness and effort on frictional work was identified by the musculoskeletal model, corroborating previous epidemiological and experimental studies. Overall, these results suggest that the ergonomic standards for wrist flexion-extension may need to be adjusted to reflect equivalent biomechanical impact and that workplace tasks should be designed to minimise exposure to combinations of highly repetitive and highly forceful work, especially when the wrist is highly flexed.

Upper-extremity musculoskeletal disorders: how many cases can be prevented? Estimates from the COSALI cohort

Objective:

This study aimed to estimate the proportion and number of incident upper-extremity musculoskeletal disorders (UEMSD) cases attributable to occupational risk factors in a working population.

Methods:

Between 2002−2005, occupational physicians randomly selected 3710 workers, aged 20–59, from the Pays de la Loire (PdL) region. All participants underwent a standardized clinical examination. Between 2007−2010, 1611 workers were re-examined. This study included 1246 workers who were free of six main clinically diagnosed UEMSD at baseline but were diagnosed with at least one of these UEMSD at follow-up [59% of men, mean age: 38 (standard deviation 8.6) years]. Relative risks and population-attributable fractions (PAF) were calculated using Cox multivariable models with equal follow-up time and robust variance. The total number of incident UEMSD in the PdL region was estimated after adjustment of the sample weights using 2007 census data. The estimated number of potentially avoidable UEMSD was calculated by multiplying PAF by the total number of incident UEMSD in PdL.

Results:

At follow-up, 139 new cases of UEMSD (11% of the study sample) were diagnosed. This represented an estimated 129 320 incident cases in the PdL in 2007. Following adjustment for personal factors, 26 381 (20.4% of all incident UEMSD) were attributable to high physical exertion, 16 682 (12.9%) to low social support, and 8535 (6.6%) to working with arms above shoulder level.

Conclusions:

A large number and important proportion of incident UEMSD may be preventable by reducing work exposures to physical exertion and working with arms above shoulder level as well as improving social support from co-workers/supervisors.

Development and Usability Testing of a Web-Based and Therapist-Assisted Coping Skills Program for Managing Psychosocial Problems in Individuals With Hand and Upper Limb Injuries: Mixed Methods Study

Background

Ineffective coping has been linked to prolonged pain, distress, anxiety, and depression after a hand and upper limb injury. Evidence shows that interventions based on cognitive behavioral therapy (CBT) may be effective in improving treatment outcomes, but traditional psychological interventions are resource intensive and unrealistic in busy hand therapy practices. Developing web-based, evidence-based psychological interventions specifically for hand therapy may be feasible in clinical practice and at home with reduced training and travel costs. Hand Therapy Online Coping Skills (HOCOS) is a program developed to supplement traditional hand therapy with therapist-assisted coping skills training based on principles from CBT and the Technology Acceptance Model.

Objective

This study aimed to describe the development and assess the usability of HOCOS to support hand therapists in the management of psychosocial problems.

Methods

The ADDIE model (Analysis, Design, Development, Implementation, and Evaluation) of system design was applied to create HOCOS. The usability testing of HOCOS involved a 2-stage process. In the first step, heuristic testing with information and communications technology (ICT) experts was completed using two sets of heuristics: Monkman heuristics and the Health Literacy Online (HLO) checklist. The second step involved user testing with hand therapists performing a series of online and face-to-face activities, completing 12 tasks on the website using the think-aloud protocol, completing the system usability scale (SUS) questionnaire, and a semistructured feedback interview in 2 iterative cycles. Descriptive statistics and content analyses were used to organize the data.

Results

In total, 4 ICT experts and 12 therapists completed usability testing. The heuristic evaluation revealed 15 of 35 violations on the HLO checklist and 5 of 11 violations on the Monkman heuristics. Initially, hand therapists found 5 tasks to be difficult but were able to complete all 12 tasks after the second cycle of testing. The cognitive interview findings were organized into 6 themes: task performance, navigation, design esthetics, content, functionality and features, and desire for future use. Usability issues identified were addressed in two iterative cycles. There was good agreement on all items of the SUS. Overall, therapists found that HOCOS was a detailed and helpful learning resource for therapists and patients.

Conclusions

We describe the development and usability testing of HOCOS; a new web-based psychosocial intervention for individuals with a hand and upper limb injuries. HOCOS targets psychosocial problems linked to prolonged pain and disability by increasing access to therapist-guided coping skills training. We actively involved target users in the development and usability evaluation of the website. The final website was modified to meet the needs and preferences of the participants.

Proportion of upper extremity musculoskeletal disorders attributable to personal and occupational factors: results from the French Pays de la Loire study

BACKGROUND

Upper extremity musculoskeletal disorders (UEMSD) are one of the most common and costly occupational health problems. We aimed to assess the population-attributable fraction (PAF) of personal and occupational risk factors associated with incident UEMSD in a working population.

METHODS

From 2002 to 2005, a random sample of 3710 workers from the Pays de la Loire region in France, aged 20-59 were included by occupational physicians (OPs). Between 2007 and 2010, 1611 workers were re-examined by their OPs. Subjects free from UEMSD at baseline were included in this study (1275 workers, mean age: 38.2 years). Cox regression models with equal follow-up time and robust variance estimates were used to estimate age-adjusted and multivariable-adjusted relative risks (RRs) and their 95% confidence intervals (CIs). Based on multivariable models, PAF associated with each factor included in the models was estimated.

RESULTS

During the follow-up period, 143 (11%) cases of UEMSD were diagnosed. PAFs for factors associated with the incident UEMSD risk were 30% (7 to 51) for high physical exertion (RPE Borg scale ≥12), 12% (- 0.2 to 24) for low social support, 7% (- 3 to 17) for working with arms above shoulder level (≥2 h/day), 20% (12 to 28) for age group ≥45, 13% (3 to 22) for the age group 35-44, and 12% (0.3 to 24) for female gender.

CONCLUSIONS

Our study suggests that an important fraction of UEMSD can be attributed to occupational exposures after the contributions of personal and other work-related factors are considered. In terms of public health, our findings are in agreement with the ergonomic literature postulating that a high proportion of UEMSD are preventable through modifying workplace risk factors. Such information is useful to help public health practitioners and policy makers implement programs of prevention of UEMSD in the working population.

A Pilot Study of Five Types of Maximum Hand Strength among Manufacturing Industry Workers in Taiwan

Background: The purpose of this study is to collect five types of maximum hand strength among workers in the manufacturing industry in Taiwan. Methods: This study is a cross sectional study with a stratified and convenient sample of workers on the production line in manufacturing industries in Central Taiwan. In total, we recruited 198 healthy subjects to participate in this study. Five types of hand strength were measured in both hands three times with 3 min rests between trials. Results: The strength of females for these five types of hand exertions were 52.0% to 67.6% of the strength of males (p < 0.001). For both genders, there was a main effect for the types of hand strength for the right hand (p < 0.001) and the left hand (p < 0.001). In general, the hand strength in U.S. and EU countries was 1.2 to 1.7 times greater than the strength among the three types of hand exertions in this study. Conclusion: These results can be used to evaluate the musculoskeletal burdens on the upper extremities in the manufacturing industry and could also be used for tool and job design and job modifications.