Comparison of measurement accuracy between two wrist goniometer systems during pronation and supination

Characterization of Musculoskeletal Injury Risk in Dungeness Crab Fishing

OBJECTIVES

Commercial Dungeness crab fishermen's manual crab pot handling activities can be done in harsh outdoor working environments at sea and can pose well-known physical risk factors associated with musculoskeletal injury including forceful exertion, repetition and awkward posture. The nonfatal injury rate in this fishing fleet is 3.4 per 1,000 full-time equivalent workers. Two-thirds of self-reported injuries in the fleet were musculoskeletal sprains and strains. To date, no objective biomechanical assessment of musculoskeletal disorder (MSD) risk has been conducted due to the challenging work environment.

METHODS

The aim of this study was to determine the feasibility of collecting objective biomechanical assessments (i.e., posture and repetition) using inertial measurement unit (IMU) sensors placed on the arms and torso of professional deckhands (n = 7) while at sea, harvesting Dungeness crab. Based on the IMU-measured posture data, fishermen's anthropometry, and crab pot weights, biomechanical loading of the low back and both shoulders was estimated.

RESULTS

The IMU sensor data showed that commercial Dungeness crab fishing is highly repetitive and poses awkward postures in the shoulders and back. The estimated static low back compression, shear force, and flexion moment about the shoulders and low back (L5/S1) indicate potential injury risk associated with harvesting crab.

CONCLUSION

The results indicate that objective biomechanical assessment using the IMU sensors is feasible in the commercial fishing environment.

Accuracy of an electrogoniometer relative to optical motion tracking for quantifying wrist range of motion

Methods for capturing wrist range of motion (RoM) vary in complexity, cost, and sensitivity. Measures by manual goniometer, though an inexpensive modality, provide neither dynamic nor objective motion data. Conversely, optical motion capture systems are widely used in three-dimensional scientific motion capture studies but are complex and expensive. The electrogoniometer bridges the gap between portability and objective measurement. Our study aims to evaluate the accuracy of a 2 degree of freedom electrogoniometer using optical motion capture as the reference for in vivo wrist motion. First, a mechanical system constructed from two plastic pipes and a universal joint mimicked a human wrist to assess the inherent accuracy of the electrogoniometer. Simulations of radial/ulnar deviation (R/U), flexion/extension (F/E) and circumduction were evaluated. Second, six subjects performed three RoM tasks of R/U deviation, F/E, and circumduction for evaluation of the in vivo accuracy. Bland-Altman analysis quantified the accuracy. The mechanical experiment reported greater accuracy than the in vivo study with mean difference values less than ±1°. The in vivo accuracy varied across RoM tasks, with mean differences greatest in the F/E task (7.2°). Smaller mean differences values were reported in the R/U deviation task (-0.8°) and the circumduction task (1.2°).

Accuracy and repeatability of wrist joint angles in boxing using an electromagnetic tracking system

The hand-wrist region is reported as the most common injury site in boxing. Boxers are at risk due to the amount of wrist motions when impacting training equipment or their opponents, yet we know relatively little about these motions. This paper describes a new method for quantifying wrist motion in boxing using an electromagnetic tracking system. Surrogate testing procedure utilising a polyamide hand and forearm shape, and in vivo testing procedure utilising 29 elite boxers, were used to assess the accuracy and repeatability of the system. 2D kinematic analysis was used to calculate wrist angles using photogrammetry, whilst the data from the electromagnetic tracking system was processed with visual 3D software. The electromagnetic tracking system agreed with the video-based system (paired t tests) in both the surrogate (< 0.2°) and quasi-static testing (< 6°). Both systems showed a good intraclass coefficient of reliability (ICCs > 0.9). In the punch testing, for both repeated jab and hook shots, the electromagnetic tracking system showed good reliability (ICCs > 0.8) and substantial reliability (ICCs > 0.6) for flexion–extension and radial-ulnar deviation angles, respectively. The results indicate that wrist kinematics during punching activities can be measured using an electromagnetic tracking system.

Kinematic Accuracy in Tracking Total Wrist Arthroplasty with Biplane Videoradiography using a CT-generated Model

Total Wrist Arthroplasty (TWA) for improving the functionality of severe wrist joint pathology has not had the same success, in parameters such as motion restoration and implant survival, as hip, knee, and shoulder arthroplasty. These other arthroplasties have been studied extensively, including the use of biplane videoradiography (BVR) that has allowed investigators to study the in-vivo motion of the total joint replacement during dynamic activities. The wrist has not been a previous focus, and utilization of BVR for wrist arthroplasty presents unique challenges due to the design characteristics of TWAs. Accordingly, the aims of this study were 1) to develop a methodology for generating TWA component models for use in BVR, and 2) to evaluate the accuracy of model-image registration in a single cadaveric model. A model of the carpal component was constructed from a CT scan, and a model of the radial component was generated from a surface scanner. BVR was acquired for three anatomical tasks from a cadaver specimen. Optical motion capture was used as the gold standard. BVR's bias in flexion/extension, radial/ulnar deviation, and pronosupination was less than 0.3°, 0.5°, and 0.6°. Translation bias was less than 0.2 mm with a standard deviation of less than 0.4 mm. This BVR technique achieved a kinematic accuracy comparable to previous studies on other total joint replacements. BVR's application to the study of TWA function in patients could advance the understanding of TWA and thus the implant's success.

Differences in typing forces, muscle activity, wrist posture, typing performance, and self-reported comfort among conventional and ultra-low travel keyboards

This study investigated the relative impact of ultra-low travel keyboards on typing force, muscle activity, wrist posture, typing performance, and self-reported comfort/preference as compared to a conventional keyboard. In a repeated-measures laboratory-based study, 20 subjects were invited to type for 10 min on each of five keyboards with different travel distances of 0.5, 0.7, 1.2, 1.6 (ultra-low travel keyboards), and 2.0 mm (a conventional keyboard). During the typing sessions, we measured typing force; muscle activity in extrinsic finger muscles (flexor digitorum superficialis and extensor digitorum communis), shoulder (trapezius) and neck (splenius capitis); wrist posture; typing performance; and self-reported comfort/preference. While using the ultra-low travel keyboards, subjects typed with less force and wrist extension, and had more ulnar deviation (p's < 0.0001) compared with conventional keyboard. However, these differences in typing forces were less than 0.5 N and less than 4° for both wrist extension and ulnar deviation. The general trend of data did not show any consistent or substantial differences in muscle activity (less than 2 %MVC) and typing performance (<5 WPM in speed; < 3% in accuracy), despite the observed statistical difference in the finger flexors and extensors muscle activity (p's < 0.19) and typing performance (p < 0.0001). However, the subjects preferred using conventional keyboards in most of the investigated self-reported comfort and preference criteria (p's < 0.4). In conclusion, these small differences indicate that using ultra-low travel keyboards may not have substantial differences in biomechanical exposures and typing performance compared to conventional keyboard; however, the subjective responses indicated that the ultra-low keyboards with the shortest key travel tended to be the least preferred.

Dynamic assessment of the wrist after total wrist arthroplasty

Our aim was to assess the outcome in patients with total wrist arthroplasty performed for end stage wrist osteoarthritis. We analysed the ranges of motion of operated and un-operated wrists using a flexible electrogoniometer during the Sollerman hand function test. We assessed grip strength with a digital dynamometer and completed patient reported outcome scores more than one year post-operatively. We reviewed 12 patients with a mean age of 64 (range 48-82) years. The flexion-extension arc was 72% and radioulnar deviation arc was 53% of the un-operated side but the total range of motion (area of circumduction) was 43% of the un-operated side and only 20% of the circumduction in age and gender-matched normal volunteers. Peak grip strength was 68% of the un-operated side. The patients reported good outcome with mean Michigan Hand Questionnaire (MHQ) scores of 56 (range 25-84) and mean Patient Evaluation Measure (PEM) scores of 39 (range 20-68). Patients completed the activities of Sollerman hand function test in twice the time (6 min) as required for a normal volunteer (2.8 min). The circumduction ellipses were narrow and central with limited radio-ulnar deviation and small mean areas of motion during activities of daily living.

Electrogoniometer measurement and directional analysis of wrist angles and movements during the Sollerman hand function test

STUDY DESIGN

Clinical measurement.

INTRODUCTION

To investigate the characteristics of wrist motion (area, axis, and location) during activities of daily living (ADL) using electrogoniometry.

METHODS

A sample of 83 normal volunteers performed the Sollerman hand function test (SHFT) with a flexible biaxial electrogoniometer applied to their wrists. This technique is accurate and reliable and has been used before for assessment of wrist circumduction in normal volunteers. A software package was used to overlay an ellipse of best fit around the 2-dimensional trace of the electrogoniometer mathematically computing the area, location, and axis angle of the ellipse.

RESULTS

Most ADL could be completed within 20% of the total area of circumduction (3686°° ± 1575°°) of a normal wrist. An oblique plane in radial extension and ulnar flexion (dart-throwing motion plane) was used for rotation (-14° ± 32°) and power grip tasks (-29° ± 25°) during ADL; however, precision tasks (4° ± 28°), like writing, were performed more often in the flexion extension plane. In the dominant hand, only 2 power tasks were located in flexion region (cutting play dough [ulnar] and pouring carton [radial]), precision tasks were located centrally, and rotation and other power tasks were located in extension region.

DISCUSSION

This study has identified that wrist motion during the ADL requires varying degrees of movement in oblique planes. Using electrogoniometry, we could visualize the area, location, and plane of motion during ADL. This could assist future researchers to compare procedures leading to loss of motion in specific quadrants of wrist motion and its impact on patient's ability in performing particular ADL. It could guide hand therapists to specifically focus on retraining the ADL that may be affected when wrist range of motion is lost after injury.

LEVEL OF EVIDENCE

Diagnostic level III.

Evaluation of Microsoft's Comfort Curve Keyboard

The purpose of this study was to determine whether there were any postural, performance or perceived comfort differences between a conventional straight keyboard and a new ergonomic concept keyboard developed by Microsoft called the Comfort Curve. The concept keyboard was designed to promote more neutral postures in the wrist using a built-in, padded wrist rest to reduce wrist extension and curved keys in alphanumeric section of the keyboard to reduce ulnar deviation. Using a repeated measures design, 26 typists from various occupations randomly used each keyboard for a period of 15 minutes. Wrist postures were measured using electrogoniometers, typing speed and accuracy was measured using typing performance software and discomfort was subjectively measured in the hands, forearms and shoulders and neck. Compared to the conventional straight keyboard, the Comfort Curve keyboard reduced ulnar deviation by 2.2 ° (p < 0.01) and wrist extension by 6.5 ° (p <0.01). There was a small differences in typing speed (50.6 vs 51.8 WPM; p = 0.03) but no differences in accuracy (93.1% vs. 93.5%, p = 0.29) between the Comfort Curve and standard keyboards respectively. Subjective discomfort ratings in all measured body locations were lower with the Comfort Curve keyboard. The results indicate that the concept keyboard achieved its design goal of reducing wrist extension, ulnar deviation and discomfort while not compromising typing speed and accuracy.

Usage Position and Virtual Keyboard Design Affect Upper-Body Kinematics, Discomfort, and Usability during Prolonged Tablet Typing

Purpose

The increase in tablet usage allows people to perform computer work in non-traditional office environments. The aim of this study was to assess the effects of changes in tablet keyboard design on postures of the upper extremities and neck, discomfort, and usability under different usage positions during prolonged touch-typing.

Methods

Eighteen healthy participants familiar with touch-screen devices were randomized into three usage positions (desk, lap, and bed) and completed six, 60-minute typing sessions using three virtual keyboard designs (standard, wide, split). Electrogoniometers continuously measured the postures of the wrists, elbow, and neck. Body discomfort and system usability were evaluated by questionnaires before and immediately after each typing session.

Results

Separate linear mixed effects models on various postural measures and subjective ratings are conducted with usage position as the between-subject factors, keyboard design and typing duration as the with-in subject factors were conducted. Using the tablet in bed led to more extended wrists but a more natural elbow flexion than the desk position. The angled split virtual keyboard significantly reduced the extent of wrist ulnar deviation than the keyboard with either standard or wide design. However, little difference was observed across the usage position and keyboard design. When the postural data were compared between the middle and end of typing sessions, the wrists, elbow, and neck all exhibited a substantially increased range of joint movements (13% to 38%). The discomfort rating also increased significantly over time in every upper body region investigated. Additionally, the split keyboard design received a higher usability rating in the bed position, whereas participants had more satisfactory experience while using the wide keyboard in the traditional desk setting.

Conclusions

Prolonged use of tablets in non-traditional office environments may result in awkward postures in the upper body that may expose users to greater risks of developing musculoskeletal symptoms. Adequate virtual keyboard designs show the potential to alleviate some postural effects and improve the user experience without changing the tablet form factors.

Wearable Goniometer and Accelerometer Sensory Fusion for Knee Joint Angle Measurement in Daily Life

Human motion analysis is crucial for a wide range of applications and disciplines. The development and validation of low cost and unobtrusive sensing systems for ambulatory motion detection is still an open issue. Inertial measurement systems and e-textile sensors are emerging as potential technologies for daily life situations. We developed and conducted a preliminary evaluation of an innovative sensing concept that combines e-textiles and tri-axial accelerometers for ambulatory human motion analysis. Our sensory fusion method is based on a Kalman filter technique and combines the outputs of textile electrogoniometers and accelerometers without making any assumptions regarding the initial accelerometer position and orientation. We used our technique to measure the flexion-extension angle of the knee in different motion tasks (monopodalic flexions and walking at different velocities). The estimation technique was benchmarked against a commercial measurement system based on inertial measurement units and performed reliably for all of the various tasks (mean and standard deviation of the root mean square error of 1:96 and 0:96, respectively). In addition, the method showed a notable improvement in angular estimation compared to the estimation derived by the textile goniometer and accelerometer considered separately. In future work, we will extend this method to more complex and multi-degree of freedom joints.

Evaluation of flat, angled, and vertical computer mice and their effects on wrist posture, pointing performance, and preference

BACKGROUND

Modern computer users use the mouse almost three times as much as the keyboard. As exposure rates are high, improving upper extremity posture while using a computer mouse is desirable due to the fact that posture is one risk factor for injury. Previous studies have found posture benefits associated with using alternative mouse designs, but at the cost of performance and preference.

OBJECTIVE

To develop new computer mouse shapes, evaluate them versus benchmarks, and determine whether there are differences in wrist posture, pointing performance, and subjective measures.

METHODS

Three concept mice were designed and evaluated relative to two existing benchmark models: a traditional flat mouse, and an alternative upright mouse. Using a repeated measures design, twelve subjects performed a standardized point-and-click task with each mouse. Pointing performance and wrist posture was measured, along with perceived fatigue ratings and subjective preferences pre and post use.

RESULTS

All of the concept mice were shown to reduce forearm pronation relative to the traditional flat mouse. There were no differences in pointing performance between the traditional flat mouse and the concept mice. In contrast, the fully vertical mouse reduced pronation but had the poorest pointing performance. Perceived fatigue and subjective preferences were consistently better for one concept mouse.

CONCLUSIONS

Increasing mouse height and angling the mouse topcase can improve wrist posture without negatively affecting performance.

Inter-rater, intra-rater and inter-instrument reliability of an electrogoniometer to measure wrist range of motion

Introduction

Assessment of the wrist is essential in hand rehabilitation. The flexible electrogoniometer has been used to measure joint range of motion in the wrist, although it has lack of reliability. The objectives of the study were to examine intra- and inter-examiner reliability, as well as inter-device reliability, of wrist range of motion obtained by a flexible electrogoniometer.

Methods

Twenty-four right-handed individuals (12 men and 12 women) took part in the study. Participants were actively and randomly subjected to radial and ulnar deviation, flexion and extension of the right wrist. The motions were measured by both the universal goniometer (CARCI®) and the electrogoniometer (MIOTEC®). Two examiners carried out three series of measurements. One of the examiners performed repeated measurement after seven days. The Intraclass Correlation Coefficient, standard error of measurement and the Bland-Altman limits of agreement were used for data analysis.

Results

Data showed excellent intra- and inter-examiner reliability for all movements with the electrogoniometer (Intraclass Correlation Coefficient > 0.90), except for the inter-examiner analysis of wrist flexion, with an Intraclass Correlation Coefficient of 0.89. The correlation between the devices was deemed to be satisfactory. Even though the excellent reliability and low standard error of measurement results were presented, Bland-Altman graphs showed some discrepant data.

Conclusion

Based on this sample, we suggest that this electrogoniometer is a reliable device regarding intra- and inter-examiner for clinical application when compared with a universal goniometry for wrist motion.

The effect of key size of touch screen virtual keyboards on productivity, usability, and typing biomechanics

OBJECTIVE

We investigated whether different virtual keyboard key sizes affected typing force exposures, muscle activity, wrist posture, comfort, and typing productivity.

BACKGROUND

Virtual keyboard use is increasing and the physical exposures associated with virtual keyboard key sizes are not well documented.

METHOD

Typing forces, forearm/shoulder muscle activity, wrist posture, subjective comfort, and typing productivity were measured from 21 subjects while they were typing on four different virtual keyboards with square key sizes, which were 13, 16, 19, and 22 mm on each side with 2-mm between-key spacing.

RESULTS

The results showed that virtual keyboard key size had little effect on typing force, forearm muscle activity, and ulnar/radial deviation. However, the virtual keyboard with the 13-mm keys had a 15% slower typing speed (p < .0001), slightly higher static (10th percentile) shoulder muscle activity (2% maximum voluntary contractions, p = .0 I), slightly greater wrist extension in both hands (2 degrees to 3 degrees, p <.01), and the lowest subjective comfort and preference ratings (p < .1).

CONCLUSIONS

The study findings indicate that virtual keyboards with a key size less than 16 mm may be too small for touch typing given the slower typing speed, higher static shoulder muscle activity, greater wrist extension, and lowest subjective preferences.

APPLICATIONS

We evaluated the effects of virtual keyboard key sizes on typing force exposures, muscle activity, comfort, and typing productivity.

New generation of wearable goniometers for motion capture systems

Background

Monitoring joint angles through wearable systems enables human posture and gesture to be reconstructed as a support for physical rehabilitation both in clinics and at the patient’s home. A new generation of wearable goniometers based on knitted piezoresistive fabric (KPF) technology is presented.

Methods

KPF single-and double-layer devices were designed and characterized under stretching and bending to work as strain sensors and goniometers. The theoretical working principle and the derived electromechanical model, previously proved for carbon elastomer sensors, were generalized to KPF. The devices were used to correlate angles and piezoresistive fabric behaviour, to highlight the differences in terms of performance between the single layer and the double layer sensors. A fast calibration procedure is also proposed.

Results

The proposed device was tested both in static and dynamic conditions in comparison with standard electrogoniometers and inertial measurement units respectively. KPF goniometer capabilities in angle detection were experimentally proved and a discussion of the device measurement errors of is provided. The paper concludes with an analysis of sensor accuracy and hysteresis reduction in particular configurations.

Conclusions

Double layer KPF goniometers showed a promising performance in terms of angle measurements both in quasi-static and dynamic working mode for velocities typical of human movement. A further approach consisting of a combination of multiple sensors to increase accuracy via sensor fusion technique has been presented.

Methodology for evaluating gloves in relation to the effects on hand performance capabilities: a literature review

The present study was conducted to review the literature on the methods that have been considered appropriate for evaluation of the effects of gloves on different aspects of hand performance, to make recommendations for the testing and assessment of gloves, and to identify where further research is needed to improve the evaluation protocols. Eighty-five papers meeting the criteria for inclusion were reviewed. Many studies show that gloves may have negative effects on manual dexterity, tactile sensitivity, handgrip strength, muscle activity and fatigue and comfort, while further research is needed to determine glove effects on pinch strength, forearm torque strength and range of finger and wrist movements. The review also highlights several methodological issues (including consideration of both task type and duration of glove use by workers, guidance on the selection and allocation of suitable glove(s) for particular tasks/jobs, and glove design features) that need to be considered in future research. Practitioner Summary: The relevant literature on the effects of protective gloves on different aspects of hand performance was reviewed to make recommendations for the testing and assessment of gloves, and to improve evaluation protocols. The review highlights research areas and methodological issues that need to be considered in future research.

Variance in direct exposure measures of typing force and wrist kinematics across hours and days among office computer workers

To determine the number of direct measurements needed to obtain a representative estimate of typing force and wrist kinematics, continuous measures of keyboard reaction force and wrist joint angle were collected at the workstation of 22 office workers while they completed their own work over three days, six hours per day. Typing force and wrist kinematics during keyboard, mouse and idle activities were calculated for each hour of measurement along with variance in measurements between subjects and between day and hour within subjects. Variance in measurements between subjects was significantly greater than variance in measurements between days and hours within subjects. Therefore, we concluded a single, one-hour period of continuous measures is sufficient to identify differences in typing force and wrist kinematics between subjects. Within subjects, day and hour of measurement had a significant effect on some measures and thus should be accounted for when comparing measures within a subject.

PRACTITIONER SUMMARY

The dose response relationship between exposure to computer related biomechanical risk factors and musculoskeletal disorders is poorly understood due to the difficulty and cost of direct measures. This study demonstrates a single hour of direct continuous measures is sufficient to identify differences in wrist kinematics and typing force between individuals.

Aging curve of neuromotor function by pronation and supination of forearms using three-dimensional wireless acceleration and angular velocity sensors

We have developed an evaluation system for pronation and supination of forearms. The motion of pronation and supination of the forearm is used as a diagnosis method of developmental disability, etc. However, this diagnosis method has a demerit in which diagnosis results between doctors are not consistent. It is hoped that a more quantitative and simple evaluation method is established. Moreover it is hoped a diagnostic criteria obtained from healthy subjects can be established to diagnose developmental disorder patients. We developed a simple and portable evaluation system for pronation and supination of forearms. Three-dimensional wireless acceleration and angular velocity sensors are used for this system. In this study, pronation and supination of forearms of 570 subjects (subjects aged 6-12, 21-100) were examined. We could obtain aging curves in the neuromotor function of pronation and supination. These aging curves obtained by our developed system, has the potential to become diagnostic criteria for a developmental disability, etc.

Wearable wrist activity monitor as an indicator of functional hand use in children with cerebral palsy

AIM

New tools that capture hand function in everyday activities and contexts are needed for assessing children with hemiplegic cerebral palsy. This study evaluates a wearable wrist monitor and tests the hypothesis that wrist extension frequency (FreqE) is an appropriate indicator of functional hand use.

METHOD

Fifteen children (four females, 11 males; age range 6-12y; mean age 10y [SD 2y]) with hemiplegia (seven at level I and eight at level II on the Manual Ability Classification System) participated in the Assisting Hand Assessment (AHA) while wearing the wrist monitor. FreqEs were captured via the wrist monitor and validated using video analysis. Correlations between FreqE and AHA scores were calculated and a multivariate linear regression was conducted to explore other measures of wrist activity.

RESULTS

Wrist extensions observed in video analyses were reliably detected by the wrist monitor (intraclass correlation coefficient, r=0.88; p<0.001) and were strongly correlated with the AHA scores (r=0.93; p<0.001). AHA scores were significantly correlated with FreqE (r=0.80; p=0.001) and the range of wrist extensions/flexions (r=0.70; p=0.008). The multivariate linear regression combining the FreqE and range of wrist extensions/flexions yielded a strong correlation with AHA scores (r=0.84; p=0.0043).

INTERPRETATION

The wearable wrist monitor may offer a convenient, valid alternative to observer reports for functional assessments of the hemiplegic hand in everyday contexts.

Surgeons' static posture and movement repetitions in open and laparoscopic surgery

BACKGROUND

There is increasing concern about the surgeon maintaining a static posture during laparoscopic surgery, which can contribute to musculoskeletal disorders. A series of studies are being conducted in Hong Kong examining the surgeons' real-time movements and electromyography in the operating theater during different operations. The present paper examines the postures and movements of surgeons during real-time open and laparoscopic procedures.

MATERIALS AND METHODS

Fourteen surgeons participated in the study (12 men, 2 women). Cervical spine movements were measured using a biaxial inclinometer attached to the surgeon's head via a headband. Biaxial electrogoniometers were attached to the surgeon's bilateral shoulder joints. Real-time joint movements in sagittal and coronal planes were recorded during open and laparoscopic surgeries for periods ranging from 30 to 80 min.

RESULTS

Surgeons generally maintained a flexed neck posture during open surgery and a more extended neck posture during laparoscopic procedures. There were statistically significant differences in mean neck posture and mean left shoulder abduction posture between the two types of surgery. Laparoscopic procedures showed a trend for longer duration in static posture in the neck, while open procedures showed trends for higher frequencies of movements.

CONCLUSIONS

This study presented a novel approach to quantify the physical workload of surgeons using biomechanical parameters to describe duration of static posture and repetitiveness of movements. Results showed that long durations of static postures in laparoscopic surgery were closely associated with low-level muscle tension, which may contribute to an increased risk of surgeons developing musculoskeletal disorders.

Qual modelo de eletrogoniômetro é mais adequado para avaliar movimentos do punho?

INTRODUÇÃO: O eletrogoniômetro é utilizado em contexto ocupacional para registro dos movimentos do punho. No entanto, diferentes tamanhos de sensores são utilizados, o que pode dificultar a comparação entre os resultados. OBJETIVO: Avaliar dois sensores de tamanho diferentes para verificar o desempenho de ambos em uma amostra com variáveis antropométricas definidas. MATERIAIS E MÉTODOS: Participaram 13 sujeitos (7 mulheres e 6 homens; idade 23 ± 2,6 anos; massa 57 ± 3,8 kg e altura 1,63 ± 4,1 m). Foram utilizados dois sensores com 65 e 110 mm de comprimento (XM65 e XM110, respectivamente) e um dispositivo de aquisição de dados (Datalog, Biometrics). Medidas antropométricas dos participantes foram registradas. Cada indivíduo realizou movimentos de flexão/extensão e desvios ulnar/radial, atingindo amplitude máxima, na posição pronada do antebraço. A ordem de realização dos movimentos e colocação dos sensores foi aleatorizada. Os dados foram analisados descritivamente e estatisticamente (análise multivariada). Foi calculada a variação entre as tentativas (variabilidade intraindividual) e entre os sensores por meio do valor RMS (root mean square). RESULTADOS: Não houve diferença significativa entre os sensores para todos os movimentos. A variabilidade intraindividual máxima foi de 2,2º. Houve diferença significativa entre os gêneros para a flexão e o desvio ulnar, sendo as mulheres as que apresentam valores maiores que os homens. A variabilidade máxima entre os sensores foi de 7,1º. CONCLUSÃO: Apesar de não identificar diferença significante entre os sensores, verificou-se que o sensor XM110 sofria abaulamento durante a extensão. Portanto, para indivíduos com altura até 1,8 m, os dados obtidos pelos diferentes sensores são comparáveis.

Thumb joint movement and muscular activity during mobile phone texting - A methodological study

PURPOSE

The extended intensive use of mobile phones and other devices for Information and Communication Technology (ICT) could expose the thumbs and fingers to operational stresses beyond their intended function which may generate pain and musculoskeletal disorders in the thumbs and the associated joints. Studies characterizing biomechanical exposures associated with mobile phone use are limited to date and the use of electrogoniometry and EMG was assessed for characterizing thumb-based activities.

SCOPE

The purpose was to investigate whether there were associations between thumb-based exposures registered with relatively easy-to-use electrogoniometric methods and more complicated EMG methods. Our hypothesis was that some outcome measures from the simpler electrogoniometric methods are related/correlated to and may be used as surrogate measure for the more complicated EMG methods.

CONCLUSIONS

Due to low associations and the complementary nature of exposures collected with electrogoniometry and EMG, the results indicated both measures are necessary for characterizing thumb exposure during mobile phone text messaging. Only in a few, selected abduction/adduction activities, could electrogoniometry be used in lieu of EMG for assessing thumb exposures.

Reliability and validity of a new ankle electrogoniometer

OBJECTIVES

To establish reliability, accuracy and concurrent validity of a new electrogoniometer (SG110A, Biometrics) for measuring ankle movement.

METHODS

The new electrogoniometer, placed at the lateral malleolus (A-perp), was compared to a customary electrogoniometer (SG110, Biometrics), placed along the Achilles tendon (A-para). Concurrent recordings were made with motion analysis. Common dance movements were performed by 17 dancers on two days. Intraclass correlation coefficients (ICC) and standard error of measurement (SEM) were calculated for sagittal angular displacements.

RESULTS

Instrument and intra-tester reliability of A-perp was high (r >or= 0.985, r >or= 0.979, respectively). Criterion and concurrent validity were also high (r >or= 0.954, r >or= 0.937). SEM ranged from 1.43 degrees to 6.99 degrees.

CONCLUSIONS

The high ICC values establish acceptable reliability and validity. Subjects found A-perp more comfortable. Although both electrogoniometers are acceptable (comparable SEM) to measure extreme ankle motions, the greater comfort and durability of the new A-perp sensor is advantageous.

Design and evaluation of a curved computer keyboard

Conventional, straight keyboards remain the most popular design among keyboards sold and used with personal computers despite the biomechanical benefits offered by alternative keyboard designs. Some typists indicate that the daunting medical device-like appearance of these alternative 'ergonomic' keyboards is the reason for not purchasing an alternative keyboard design. The purpose of this research was to create a new computer keyboard that promoted more neutral postures in the wrist while maintaining the approachability and typing performance of a straight keyboard. The design process created a curved alphanumeric keyboard, designed to reduce ulnar deviation, and a built-in, padded wrist-rest to reduce wrist extension. Typing performance, wrist postures and perceptions of fatigue when using the new curved keyboard were compared to those when using a straight keyboard design. The curved keyboard reduced ulnar deviation by 2.2 degrees +/- 0.7 (p < 0.01). Relative to the straight keyboard without a built-in wrist-rest, the prototype curved keyboard with the built-in padded wrist-rest reduced wrist extension by 6.3 degrees +/- 1.2 (p < 0.01). There were no differences in typing speed or accuracy between keyboards. Perceived fatigue ratings were significantly lower in the hands, forearms and shoulders with the curved keyboard. The new curved keyboard achieved its design goal of reducing discomfort and promoting more neutral wrist postures while not compromising users' preferences and typing performance.

Validation of an objective device for assessing circumductive wrist motion

PURPOSE

Circumduction of the wrist consists of a circular motion combining flexion, extension, and radioulnar deviation without simultaneous supination or pronation of the forearm. This pattern of flexion-extension and radial-ulnar deviation coupling is vital in common tasks; however, its evaluation in hand clinics is limited by the availability and ease of current tools. We present the construct, criterion, test-retest, and inter-rater validity of a new circumduction measurement device.

METHODS

Splint volunteers (n = 42) and hand clinic patients (n = 51) were studied to assess different aspects of validity and reliability for the circumduction jig. Known-group validation was used to assess construct validity and demonstrate the ability of the device to differentiate between patients with lesser or greater circumduction values. Criterion validity was demonstrated by comparing the circumduction measures of the device to flexion, extension, ulnar deviation, and radial deviation. Test-retest reliability was established by comparing the results of repeated circumduction measures for the hand clinic patients by 2 blinded, independent researchers, and inter-rater reliability was determined by evaluating the correlation in circumduction measures taken on the same patient by different blinded, independent researchers.

RESULTS

Circumduction measurements significantly decreased (test for trend, p < .01) across the 3 different treatments that represented progressively reduced range of motion, establishing construct validity of the device. Flexion, extension, and radioulnar deviation all correlated significantly with circumduction; the correlation values ranged from 0.46 to 0.82 (p < .01) among all subjects (93 subjects, 228 measurements). Intra-rater reliability was 0.98 (p < .01) for both evaluators, and inter-rater reliability was 0.94 (p < .01).

CONCLUSIONS

The present validation study demonstrated criterion, construct, test-retest, and inter-rater reliability for a newly designed circumduction measurement device.

Precision of measurements of physical workload during standardized manual handling part III: goniometry of the wrists

Goniometry of the wrist is a feasible method for studying wrist movements in most hand-intensive work. The precision and accuracy of the method per se is good. For the knowledge on validity of field measurements, the size of imprecision is of importance. This study evaluated this condition during standardized circumstances. Six women performed three different hand-intensive work tasks: 'materials picking', 'light assembly', and 'heavy assembly', repeated during three different days. Variance components between-days (within subjects) and between-subjects were derived for positions (flexion/extension and deviation) and movements, including angular velocities, % of time with very low velocity (<1 degree /s), as well as repetitiveness. For positions, the average standard deviations in the three tasks were, both between-days and between-subjects, 3-4 degrees . For movements, the coefficients of variation of angular velocities were about 10% between-days, and could to a great part be explained by differences in work rate. Between-subjects variability was higher, 20-40%. The variability was larger at low velocities than at high ones. The precision of the measured positions was good, expressed as small between-days and between-subjects variability. For movements, the between-days variability was also small, while there was a larger between-subjects variability. The imprecision of goniometry is consequently lower and comparable with inclinometry but lower than for EMG.

Physical exposure differences between children and adults when using standard and small computer input devices

By the age of five years, 75% of the children in the USA are using computers and at this age they are only one-half to two-thirds the size of and about one-fifth as strong as their adult counterparts. Fourteen children between five and eight years of age and their same-gender biological parents (giving a total of 28 subjects) were evaluated using both a standard and a smaller, child-proportional input device during standardised mouse and keyboard tasks. Typing and computer mouse performance were measured with tracking software, wrist posture was measured with an electrogoniometer and electromyography was used to measure finger flexor and extensor muscle activity in the right arm. With the small mouse, both children and adults performed the mouse task significantly faster and made significantly fewer errors. When using the standard-sized mouse and keyboard, children worked with significantly greater ulnar deviation and significantly less extension than their adult counterparts. When children used the smaller mouse, finger flexor muscle activity, finger extensor muscle activity and ulnar deviation significantly decreased, with little change in wrist extension compared to the standard mouse. No significant differences were observed between the standard and small keyboards for children or their parents. Compared to their adult counterparts, children had to apply twice the relative force, as a percentage of their maximum capacity, to activate the buttons and keys on the input devices. These measured differences may have application in the design of computer input devices for children.

Improving goniometer accuracy by compensating for individual transducer characteristics

Flexible goniometers are useful for direct movement measurements. Crosstalk due to rotation between the endblocks is well known. However, even without any rotation, some crosstalk can occur. The objective of this study was to elucidate the effect of, and compensate for, the inherent crosstalk in biaxial goniometers, with specific relevance for applications with one dominating movement direction. Six biaxial goniometers (M110, Biometrics Ltd., Gwent, UK) were evaluated. A precision jig, for simulating pure flexion/extension angles, was constructed. Each sensor produced a consistent and specific crosstalk pattern, when tested over a +/-100 degrees range of motion. A procedure for correction for the inherent crosstalk of individual goniometer, based on polynomial adjust, is presented. The method for compensation, which reduced the root mean square error from, on average for the six goniometers, 3.7 degrees (range 1.8-10.1 degrees) to 0.35 degrees (0.12-0.55 degrees), might be required for obtaining valid goniometer measurements, e.g. of valgus/varus of the knee during gait flexion/extension movements.

Assessment of physical demands and comparison of multiple exposure definitions in a repetitive sawmill job: board edger operator

The primary objectives of the study were to 1) describe the physical exposures in a sawmill job with a high incidence of upper extremity musculoskeletal injuries in terms of multiple measures of posture, exertion and frequency (with varying definitions) and 2) to examine the comparability of those definitions. Surface electromyography and electrogoniometry were used to quantify the muscle demands and joint motions. Fourteen board edger operators from two sawmill facilities participated. All exposure assessments, with the exception of surface EMG measurements, were performed on the production lines. EMG measurements were performed within the facility in a location removed from the production line. The measurements showed that, on average, ranges of motions of 59, 102 and 84 degrees respectively in the planes of wrist radial/ulnar deviation, flexion/extension and pronation/supination were required to perform the job. Significant differences (p < .001) were observed between ranges of motion defined by peak postures and those due to peak postures required to perform the primary task only. Performance of the primary task required an average of 32% of maximum voluntary contraction from the forearm muscles assessed. Repetitions per day ranged, on average, from 2,015 to 9,365. Incidence of reported upper extremity musculoskeletal injuries in the two facilities assessed was found to be higher with the greater total exposure. However, examination of the trend with a standardized measure of injury incidence was not possible.

Accuracy and feasibility of using an electrogoniometer for measuring simple thumb movements

The aim of this study was to determine the accuracy and feasibility of using an electrogoniometer (Model SG 110; Biometrics, Gwent, UK) for measuring simple thumb movements. Thumb disorders have been associated with the use of hand held devices such as mobile phones and these devices have become an integral part of modern life. In 15 young subjects, the measurements of eight flexion/extension (Flex/Ext) and adduction/abduction (Ad/Ab) thumb positions were compared between a thumb-mounted electrogoniometer and manual goniometer (which was taken as the benchmark). Group mean electrogoniometric measurement errors were below 4 degrees and 5 degrees for Ad/Ab and Flex/Ext measurements, respectively. During mobile phone use, the electrogoniometers measured differences in maximal joint angle postures, which appeared to be related to differences in mobile phone size. High movement velocities may increase the risk of musculoskeletal injury and the results indicated that Ad/Ab movements were twice the speed of Flex/Ext movements during mobile phone use. Electrogoniometers have utility for studying thumb movements during mobile phone use and may be used to evaluate other thumb-based input devices.

Effect of aviation snip design and task height on upper extremity muscular activity and wrist posture

Hand tools described as ergonomic in design are intended to reduce exposure to physical risk factors associated with work-related musculoskeletal disorders. Additionally, using the right tool for the job is believed to reduce exposure and, consequently, risk of disease. Sheet metal workers frequently use a cutting tool called aviation snips when fabricating and installing ductwork. The purpose of this laboratory simulation study was to determine the effect of (1) aviation snip design; and (2) work height on muscle activity, wrist posture, and user satisfaction among sheet metal workers. We hypothesized that specific aviation snips designs would be most appropriate for use at specific heights. Twenty-three sheet metal workers used three different designs of aviation snips to make curved cuts in sheet metal placed both at waist height and shoulder height. Conventional circular snips, straight snips, and an alternate design of offset snips were used. Upper extremity muscle activity was measured with surface electromyography, wrist posture was measured with electrogoniometry, and user satisfaction was rated by the participants on a survey. Statistically significant effects of snip design and task height on muscle activity, wrist posture, and user satisfaction were observed. However, no snip was preferable for all dependent variables. Work height had a greater effect on muscle activity and wrist posture than snip design. Field studies are indicated to determine the long-term effect of snip design on physical risk factors and risk of musculoskeletal disorders.

Changes in upper extremity biomechanics across different mouse positions in a computer workstation

In order to determine differences in biomechanical risk factors across different mouse positions within computer workstations a repeated measures laboratory study was completed with 30 adults (15 females 15 males). The subjects performed mouse-intensive tasks during two experiments. One experiment examined three mouse positions: a standard mouse (SM) position with the mouse directly to the right of the keyboard; a central mouse (CM) position with the mouse between the keyboard and the body, positioned in the body's mid-sagittal plane; a high mouse (HM) position, which simulated using a keyboard drawer with the mouse on the primary work surface. The second experiment compared two mouse positions: the SM position and a more central position using a keyboard without a number keypad (NM). Electrogoniometers and inclinometers measured wrist and upper arm postures and surface electromyography measured muscle activity of four forearm muscles and three shoulder muscles. The CM mouse position was found to produce the most neutral upper extremity posture across all measures. The HM position produced the least neutral posture and resulted in the highest level of muscle activity. Compared to the SM position, the NM position reduced wrist extension slightly and promoted a more neutral shoulder posture. Little difference in muscle activity was observed between the SM and NM positions. In conclusion, of these alternative mouse positions, the HM position was the least desirable, whereas the CM position reduced overall awkward postures associated with mouse-intensive computer tasks.

A laboratory study to determine the effects of universal and rotating ultrasonic inserts on wrist movement and scaling time efficiency of dental hygienists

PURPOSE

The purpose of this study was to determine if differences existed in range of wrist movements and scaling time efficiency of dental hygienists using a rotating ultrasonic insert when compared with a standard universal insert.

METHODS

A convenience sample of 32 consenting experienced dental hygienists who met inclusion criteria was invited to participate. Using a cross-over research design, the 32 participants were randomly assigned to one of the two subgroups. Subgroup A (n = 16) used the rotating universal ultrasonic insert on a typodont, rested for 15 min and the standard universal insert on a different typodont. Subgroup B (n = 16) used the standard universal ultrasonic insert on a typodont, rested for 15 min and the rotating universal ultrasonic insert on a different typodont. Each participant used the rotating and standard universal ultrasonic scaling inserts to remove 2 cm3 artificial calculus from two different typodonts for up to 15 min per insert. Scaling time efficiency was determined using a Modified Volpe-Manhold Calculus Index, measuring the amount of artificial calculus remaining after ultrasonic scaling. While scaling, each participant wore the WristSensor goniometry gloves, which determined changes in wrist movements (flexion and extension and ulnar and radial deviations), measured as a deviation from the neutral position.

RESULTS

A paired t-test (P = 0.05) using 30 subjects with useable data, revealed no statistically significant differences between the two different inserts in terms of wrist movements and scaling time efficiency. A multivariate analysis of variance revealed no statistically significant differences in the percentage of time dental hygienists were in high, medium or low-risk posture categories while using the rotating ultrasonic insert compared with the standard universal insert. Based on the results of this laboratory study, dental hygienists using a rotating ultrasonic insert appear to experience no ergonomic advantage in terms of wrist postures or timesavings over a standard insert.

Position-sensing technologies for movement analysis in stroke rehabilitation

Research has focused on improvement of the quality of life of stroke patients. Gait detection, kinematics and kinetics analysis, home-based rehabilitation and telerehabilitation are the areas where there has been increasing research interest. The paper reviews position-sensing technologies and their application for human movement tracking and stroke rehabilitation. The review suggests that it is feasible to build a home-based telerehabilitation system for sensing and tracking the motion of stroke patients.

Physical exposure of sign language interpreters: baseline measures and reliability analysis

Measurement of physical exposure to musculoskeletal disorder risk factors must generally be performed directly in the field to assess the effectiveness of ergonomic interventions. To perform such an evaluation, the reliability of physical exposure measures under similar field conditions must be known. The objectives of this study were to estimate the reliability of physical exposure measures performed in the field and to establish the baseline values of physical exposure in sign language interpreters (SLI) before the implementation of an intervention. The electromyography (EMG) of the trapezius muscles as well as the wrist motions of the dominant arm were measured using goniometry on nine SLI on four different days. Several exposure parameters, proposed in the literature, were computed and the generalizability theory was used as a framework to assess reliability. Overall, SLI showed a relatively low level of trapezius muscle activity, but with little time at rest, and highly dynamic wrist motions. Electromyography exposure parameters showed poor to moderate reliability, while goniometry parameter reliability was moderate to excellent. For EMG parameters, performing repeated measurements on different days was more effective in increasing reliability than extending the duration of the measurement over one day. For goniometry, repeating measurements on different days was also effective in improving reliability, although good reliability could be obtained with a single sufficiently long measurement period.

Measurements of wrist and forearm positions and movements: effect of, and compensation for, goniometer crosstalk

Flexible biaxial goniometers are extensively used for measuring wrist positions and movements. However, they display an inherent crosstalk error. The aim was to evaluate the effect, of this error, on summary measures used for characterizing manual work. A goniometer and a torsiometer were combined into one device. An algorithm that effectively compensated for crosstalk was developed. Recordings from 25 women, performing five worktasks, were analyzed, both with and without compensation for crosstalk. The errors in the 10th, 50th and 90th percentiles of the flexion/extension distributions were small, on average <1 degrees. The ulnar/radial deviation distributions were weakly dependent on forearm position. The flexion/extension velocity measures were, for the 50th and 90th percentiles, as well as the mean velocity, consistently underestimated by, on average, 3.9%. For ulnar/radial deviation, the velocity errors were less consistent. Mean power frequency, which is a measure of repetitiveness, was insensitive (error <1%) to crosstalk. The forearm supination/pronation angular distributions were wider, and the velocities higher, than for the wrists. Considering wrist/hand exposure in epidemiologic studies, as well as for establishing and surveillance of exposure limits for prevention of work-related upper extremity musculoskeletal disorders, the crosstalk error can, when considering other errors and sources to variation, be disregarded.

Wrist movements among females in a repetitive, non-forceful work

Wrist positions and movements were measured and a physical examination was conducted in 12 female operators in an industrial quality-control work. The handled products are of very low weight, thus, the work can be considered as non-forceful. The work was highly repetitive; 0.54Hz for the right wrist/hand and 0.41Hz for the left. The angular velocities were also high; for the right wrist/hand median value was 30 degrees /s and peak value 108 degrees /s, for the left wrist/hand 24 degrees /s and 88 degrees /s, respectively. The frequency of musculoskeletal disorders was high, especially for the right wrist/hand. Although the work was non-forceful and there were minor extreme positions in the wrists, the results are consistent with reported exposure-response relations in other high-risk jobs. Thus, the repetitiveness and the high velocities are the likely causes for the high prevalence of disorders in the wrists/hands among the operators.

Computer mouse use in two different hand positions: exposure, comfort, exertion and productivity

The aim of this study was to determine whether there are differences in exposure, comfort, exertion and productivity between a neutral and a pronated hand position when using a computer mouse. Nineteen experienced VDU workers performed a standardised text editing task with each mouse hand position. The wrist positions and movements in the working arm were registered by an electrogoniometer and the muscle activity in the shoulder, two extensors in the forearm and the first dorsal interossei (FDI) was registered by electromyography. The subjects rated perceived exertion and comfort in work with each mouse hand position. Work with the neutral hand position, compared to the pronated, gave a decreased muscle activity in the extensors of the forearm and in the FDI and a trend indicating a decrease in the frequency of deviation movements in the wrist. At the same time, the subjects showed a decreased productivity and they rated less comfort in work with the neutral hand position.