Quantification of carpal tunnel morphology using centroid-to-boundary distance shape signatures.

Morphology analysis is valuable to understanding risk factors and the etiology of carpal tunnel (CT) syndrome. The objective of this study was to investigate morphology changes along the length of the CT using shape signatures (SS). Analysis was performed on ten cadaveric specimens in neutral wrist posture. Centroid-to-boundary distance SS were generated for proximal, middle, and distal CT cross-sections. Phase shift and Euclidean distance were quantified relative to a template SS for each specimen. Medial, lateral, palmar, and dorsal peaks were identified on each SS to generate metrics of tunnel width, tunnel depth, peak amplitude, peak angle. Width and depth measures were also performed using previously reported methods to serve as a basis of comparison. The phase shift revealed twisting of 21° between the ends of the tunnel. Distance from the template and width varied significantly over the length of the tunnel, while depth did not. Measures of width and depth using the SS method were consistent with previously reported methods. The SS method afforded the advantage of peak analysis with overall trends of peak amplitude indicating flattening of the tunnel at the proximal and distal ends relative to a rounder shape in the middle.

Predicting Wrist Posture during Occupational Tasks Using Inertial Sensors and Convolutional Neural Networks.

Current methods for ergonomic assessment often use video-analysis to estimate wrist postures during occupational tasks. Wearable sensing and machine learning have the potential to automate this tedious task, and in doing so greatly extend the amount of data available to clinicians and researchers. A method of predicting wrist posture from inertial measurement units placed on the wrist and hand via a deep convolutional neural network has been developed. This study has quantified the accuracy and reliability of the postures predicted by this system relative to the gold standard of optoelectronic motion capture. Ten participants performed 3 different simulated occupational tasks on 2 occasions while wearing inertial measurement units on the hand and wrist. Data from the occupational task recordings were used to train a convolutional neural network classifier to estimate wrist posture in flexion/extension, and radial/ulnar deviation. The model was trained and tested in a leave-one-out cross validation format. Agreement between the proposed system and optoelectronic motion capture was 65% with κ = 0.41 in flexion/extension and 60% with κ = 0.48 in radial/ulnar deviation. The proposed system can predict wrist posture in flexion/extension and radial/ulnar deviation with accuracy and reliability congruent with published values for human estimators. This system can estimate wrist posture during occupational tasks in a small fraction of the time it takes a human to perform the same task. This offers opportunity to expand the capabilities of practitioners by eliminating the tedium of manual postural assessment.

Carpal tunnel volume distribution and morphology changes with flexion-extension and radial-ulnar deviation wrist postures.

Non-neutral wrist postures have been reported to cause decreased carpal tunnel volume (CTV) contributing to impingement of the median nerve and development of carpal tunnel syndrome. Recent analysis found CTV did not change with ±20° flexion-extension (FE), however, CTV decreased with ulnar deviation over the range of -5° to 15° radial-ulnar deviation (RUD). These findings suggest CTV may be too coarse of a measure to reflect the effects of slight non-neutral postures, or that volume is conserved and redistributed due to changes in tunnel morphology with posture. The objective of this study was to assess volume distribution along the length of the carpal tunnel and to quantify regional morphology changes with deviated wrist postures in both FE and RUD. Analysis was performed on a dataset of computed tomography scans collected on ten cadaveric specimens (5 male, 5 female, mean age = 80.7 ± 10.9 years) over a range of FE and RUD postures. The carpal tunnel of each scan was divided into four quartiles of equal length along the tunnel to quantify volume distribution. Volume within the carpal tunnel was seen to redistribute with both FE and RUD. Decreased volume in the distal aspect of the tunnel with flexion and proximal aspect of the tunnel with ulnar deviation may contribute to localized compression of the medial nerve. Measures of mean cross-sectional area, width and depth by quartile provided an indication of the morphology changes associated volume redistribution. Morphology analysis also revealed twisting between the proximal and distal aspects of the tunnel which increased with flexion and ulnar deviation and may further contribute to strain on the median nerve.

Effects of slight flexion-extension and radial-ulnar deviation postures on carpal tunnel volume.

BACKGROUND: Non-neutral wrist postures are a commonly reported risk factor for carpal tunnel syndrome. It is unclear how slight flexion-extension and radial-ulnar deviation postures affect the carpal tunnel. The objective was to determine the effects of slight non-neutral postures by quantifying carpal tunnel volume. METHODS: Computed tomography images were collected on ten cadaveric specimens in target postures of -20°, -10°, -5°, 0°, 5°, 10°, and 20° of flexion and - 10°, -5°, 0°, 5°, and 10° of radial-ulnar deviation. Surface meshes of the carpal tunnel, carpal bones, radius, and third metacarpal were generated with manual segmentation. Carpal tunnel volume was calculated as the volume between proximal and distal boundaries defined with anatomical landmarks and the orientation of the tunnel. The precise wrist posture of each scan was determined with inertial-based coordinate systems of the radius and third metacarpal. FINDINGS: Through multiple linear regression it was determined that, over the observed range of postures, flexion-extension angle does not have a significant effect (p = 0.99) while radial-ulnar deviation angle has a significant effect of -5.9 mm3/degree (p = 0.003). The findings were consistent with previous studies of postural effects on carpal tunnel pressure. INTERPRETATION: For the treatment and prevention of carpal tunnel syndrome, results suggest that attention should be given to slight radial-ulnar deviation postures (<10°), while slight flexion-extension postures (<20°) are of lesser consequence to carpal tunnel volume.

Accuracy of a Low-Cost 3D-Printed Wearable Goniometer for Measuring Wrist Motion.

Wrist motion provides an important metric for disease monitoring and occupational risk assessment. The collection of wrist kinematics in occupational or other real-world environments could augment traditional observational or video-analysis based assessment. We have developed a low-cost 3D printed wearable device, capable of being produced on consumer grade desktop 3D printers. Here we present a preliminary validation of the device against a gold standard optical motion capture system. Data were collected from 10 participants performing a static angle matching task while seated at a desk. The wearable device output was significantly correlated with the optical motion capture system yielding a coefficient of determination (R2) of 0.991 and 0.972 for flexion/extension (FE) and radial/ulnar deviation (RUD) respectively (p < 0.0001). Error was similarly low with a root mean squared error of 4.9° (FE) and 3.9° (RUD). Agreement between the two systems was quantified using Bland-Altman analysis, with bias and 95% limits of agreement of 3.1° ± 7.4° and -0.16° ± 7.7° for FE and RUD, respectively. These results compare favourably with current methods for occupational assessment, suggesting strong potential for field implementation.

Design and validation of a novel 3D-printed wearable device for monitoring knee joint kinematics.

Gait analysis provides an important tool for the study and clinical evaluation of conditions which affect knee joint biomechanics. Collection of knee joint kinematics in real world environments during locomotor activities of daily living could provide quantitative evidence to help understand functional impairment. Unfortunately, the high cost and necessary technical expertise associated with current commercially available systems for kinematic monitoring serve as an impediment to their adoption outside of specialized research groups. We have developed a low-cost, custom wearable device to address these shortcomings. The 3D printed device is capable of measuring knee flexion/extension (F/E) and adduction/abduction (AD/AB) angles. Here, we present a gold standard validation of the novel device against an optoelectronic motion capture system (MCS). Data were collected during a treadmill walking task from 8 participants on 2 separate occasions. Agreement with the MCS was quantified via root mean squared error (RMSE), coefficients of multiple correlation (CMC), paired dependent t-tests and Bland-Altman analyses. The wearable device had an overall RMSE of 3.0° and 2.7° and a CMC of 0.97 and 0.91 in F/E and AD/AB respectively. Wearable device error showed no significant differences between test occasions, and Bland-Altman analyses showed low bias with narrow limits of agreement. These results demonstrate the capability of the device to accurately and reliably monitor knee F/E and AD/AB angles showing strong potential for field implementation.

Effect of fatigue on muscle latency, muscle activation and perceived discomfort when exposed to whole-body vibration.

Whole-body vibration and muscle fatigue have both been shown to delay the trunk muscle reflex response and increase trunk muscle activation, leading to an increased risk of low back injuries. However, the effects of whole-body vibration on previously fatigued trunk muscles have never been tested, despite studies showing that prolonged exposure to whole-body vibration can lead to muscle fatigue. The purpose of this research was to investigate the effects of muscle fatigue on muscle latency, muscle activation and perceived discomfort when exposed to whole-body vibration. The results showed that a fatigued muscle state resulted in increased muscle latency, muscle activation and perceived discomfort, which all escalate the risk of low back injuries. Additionally, the ISO 2631-1 comfort ratings did not increase with fatigue, showing a disconnect between these comfort ratings and the perceived discomfort ratings in a fatigued muscle state. Practitioner summary: When exposed to whole-body vibration, fatigued back muscles result in delayed muscle contraction, higher overall muscle activation and increased perceived discomfort, all of which are known to increase low back injury risk. ISO 2631-1 comfort ratings are unable to increase with fatigue, showing a disconnect with perceived discomfort ratings. Abbreviations: EMG: electromyography; EO: external oblique; IO: internal oblique; LE: lumbar erector spinae; LEO: left externaloblique; LIO: left internal oblique; LLE: left lumbar erector spinae; LTE: left thoracic erector spinae; MVC: maximum voluntarycontraction; REO: right external oblique; RIO: right internal oblique; RLE: right lumbar erector spinae; RTE: right thoracicerector spinae; SEAT: Seat Effective Amplitude Transmissibility; TE: thoracic erector spinae; WBV: whole body vibration.

Quantification of the transverse carpal ligament elastic properties by sex and region.

BACKGROUND: The transverse carpal ligament is an integral factor in the etiology of carpal tunnel syndrome. The purpose of this study was to report the biomechanical properties of this ligament and quantify sex-based differences and regional variation in tissue response. We hypothesized that the mechanical response would not be uniform across the surface, and that female ligament properties would have higher strain profiles and lower mechanical properties. METHODS: Uniaxial testing of twelve (six males, six females) human fresh frozen cadaveric transverse carpal ligaments was carried out using an Instron Materials Testing Machine. Strain was measured via a non-contact optical method. FINDINGS: The following biomechanical properties of the transverse carpal ligament were reported in this work: failure strain (male: 9.2 (SD 5.0), female: 15.5 (SD 7.1)%), strength (male: 4.9 (SD 1.5), female: 4.5 (SD 1.6) MPa), and modulus of elasticity (male: 52.9 (SD 19.6), female: 38.2 (SD 21.9) MPa). The radial side displayed significantly more strain at failure compared to ulnar (P<0.0001). INTERPRETATION: The results of this study provide evidence that manipulative treatments should focus stretching on the radial half of the tissue, which experiences larger strains under uniform loading conditions. In addition, this work suggests possible sex-based differences in mechanical properties of the transverse carpal ligament, which could provide a basis for the development of improved non-surgical treatment methods for carpal tunnel syndrome. The results can also be applied to generate more accurate computational models of the wrist.

Selecting seats for steel industry mobile machines based on seat effective amplitude transmissibility and comfort.

OBJECTIVE: The purpose of this work was to help a steel industry partner select the most appropriate of three high end heavy equipment seats to retrofit a number of their heavy mobile machines used in the steel making process. PARTICIPANTS: The participants included 8 males (22.3 ± 2.0 yrs.) and 8 females (23.5 ± 1.8 yrs.) with no experience operating heavy mobile equipment. METHODS: Previously recorded 6-DOF chassis acceleration data from a Pot Hauler (a machine which picks up and transports pots of slag) were used to extract six, 20 second representative profiles for implementation on a lab-based heavy machine simulator (6-DOF Parallel Robotics System Corporation robot). Subjects sat on three heavy equipment seats (BeGe7150, Grammar MSG 95G1721, and a 6801 Isringhausen with the seat pan cushion retrofitted with a Skydex cushion) mounted on the simulator. Each subject completed three trials for each combination of seat (n=3) and vibration profile (n=6). Chassis and operator/seat interface vibration were measured by 2, 6-DOF vibration transducers. Variables included Seat Effective Amplitude Transmissibility (SEAT) (X,Y,Z,Roll,Pitch,Yaw,6DOF Vector Sum) to determine if the seat was attenuating or amplifying the vibration, 6-degree of freedom (DOF) vibration total value weighted predicted comfort (Avc) (according to ISO 2631-1) and operator reported comfort (ORC). RESULTS: Factorial ANOVAs revealed significant differences (p < or = 0.05) between seats for all SEAT variables but different seats performed better than others depending on the axis. Significant differences between males and females were observed for SEAT in X,Y, and Pitch as well as for Avs. As expected there were significant differences between vibration profiles for all assessed variables. A number of interaction effects were observed, the most frequently occurring of which was between seat and vibration profile. CONCLUSIONS: Based upon the number of seat and vibration profile interactions, results suggest that a single seat is not suited for all tested conditions. However, SEAT values for all of the seats tested were extremely low (e.g., 6-DOF SEAT < 30%) indicating that all of the seats were capable of providing good vibration attenuation.

Behavioral and cardiovascular responses to frustration during simulated driving tasks in young adults with and without attention disorder symptoms.

OBJECTIVE: The present study examined the role of negative emotions on driving performance in relation to ADHD, by comparing young adults scoring high on measures of ADHD (n = 20) with a control group (n = 22). METHOD: The authors used cardiorespiratory physiological measures, simulated driving behavior, and self-report to examine how participants with high and low ADHD symptoms responded to frustration and to determine how frustration affected simulated driving performance. RESULTS: Groups did not differ in operational driving skills, but participants with high ADHD symptoms reported more frustration and exhibited more impairment at the tactical level of driving performance than the controls. There was significant suppression of respiratory sinus arrhythmia from resting baseline during tasks, but it did not differ between groups during driving. CONCLUSION: This article proposes that remedial driver training for ADHD populations should focus more on the control of negative emotions rather than on attention or fundamental driving skills.

Fibre bundle element method of determining physiological cross-sectional area from three-dimensional computer muscle models created from digitised fibre bundle data.

Physiological cross-sectional area (PCSA) is used to compare force-producing capabilities of muscles. A limitation of PCSA is that it cannot be measured directly from a specimen, as there is usually no area within the muscle traversed by all fibres. Traditionally, a formula requiring averaged architectural parameters has been used. The purpose of this paper is to describe the development of a fibre bundle element (FBE) method to calculate PCSA from digitised fibre bundle data of five architecturally distinct muscles and compare the FBE and PCSA formula. An FBE method was developed that used a serially arranged set of cylinders as the volumetric representation of each fibre bundle, and PCSA was computed as the summation of the cross-sectional area of each FBE. Four of five muscles had significantly different PCSA between FBE and formula methods. The FBE method provides an approach that considers architectural variances while minimising the need for averaged architectural parameters.

A systematic approach to simulating field-based occupational whole-body vibration exposure in the lab using a 6df robot.

BACKGROUND: Whole-body vibration is a significant workplace risk factor for discomfort and injury in many work sectors. The current approach for evaluating vibration exposures typically involves field studies of seatpan acceleration while the operators perform typical workplace activities. These vibration exposures are then compared to international standards to evaluate the risk of discomfort or injury. This approach does not enable systematic and controlled study of specific workplace factors such as the effect of seating, and it is difficult and expensive to perform. APPROACH TO PAPER: We have developed a systematic approach for studying whole-body vibration in the laboratory setting. This approach involves field studies of occupational exposures measuring the 6 degree of freedom chassis accelerations (translational and rotational) and replication of these exposures in the laboratory. FINDINGS: To date, as a research team, we have collected chassis vibration data from specific vehicles in the forestry (skidders), mining (load-haul-dump vehicles), and construction (scrapers) sectors. We have processed these exposures to develop a library of representative vibration motions, and have replicated these motions in the laboratory using a robotic platform. CONCLUSIONS: This systematic approach of combining field- and laboratory-based measures has facilitated research into specific relevant questions such as the effects of multi axis vibrations on the physical risks to operator health and direct evaluation of the vibration attenuation properties of industrial seats.

A new laser reflectance system capable of measuring changing cross-sectional area of soft tissues during tensile testing.

Determination of the biomechanical properties of soft tissues such as tendons and ligaments is dependent on the accurate measurement of their cross-sectional area (CSA). Measurement methods, which involve contact with the specimen, are problematic because soft tissues are easily deformed. Noncontact measurement methods are preferable in this regard, but may experience difficulty in dealing with the complex cross-sectional shapes and glistening surfaces seen in soft tissues. Additionally, existing CSA measurement systems are separated from the materials testing machine, resulting in the inability to measure CSA during testing. Furthermore, CSA measurements are usually made in a different orientation, and with a different preload, prior to testing. To overcome these problems, a noncontact laser reflectance system (LRS) was developed. Designed to fit in an Instron 8872 servohydraulic test machine, the system measures CSA by orbiting a laser transducer in a circular path around a soft tissue specimen held by tissue clamps. CSA measurements can be conducted before and during tensile testing. The system was validated using machined metallic specimens of various shapes and sizes, as well as different sizes of bovine tendons. The metallic specimens could be measured to within 4% accuracy, and the tendons to within an average error of 4.3%. Statistical analyses showed no significant differences between the measurements of the LRS and those of the casting method, an established measurement technique. The LRS was successfully used to measure the changing CSA of bovine tendons during uniaxial tensile testing. The LRS developed in this work represents a simple, quick, and accurate way of reconstructing complex cross-sectional profiles and calculating cross-sectional areas. In addition, the LRS represents the first system capable of automatically measuring changing CSA of soft tissues during tensile testing, facilitating the calculation of more accurate biomechanical properties.

Determining physiological cross-sectional area of extensor carpi radialis longus and brevis as a whole and by regions using 3D computer muscle models created from digitized fiber bundle data.

Architectural parameters and physiological cross-sectional area (PCSA) are important determinants of muscle function. Extensor carpi radialis longus (ECRL) and brevis (ECRB) are used in muscle transfers; however, their regional architectural differences have not been investigated. The aim of this study is to develop computational algorithms to quantify and compare architectural parameters (fiber bundle length, pennation angle, and volume) and PCSA of ECRL and ECRB. Fiber bundles distributed throughout the volume of ECRL (75+/-20) and ECRB (110+/-30) were digitized in eight formalin embalmed cadaveric specimens. The digitized data was reconstructed in Autodesk Maya with computational algorithms implemented in Python. The mean PCSA and fiber bundle length were significantly different between ECRL and ECRB (p < or = 0.05). Superficial ECRL had significantly longer fiber bundle length than the deep region, whereas the PCSA of superficial ECRB was significantly larger than the deep region. The regional quantification of architectural parameters and PCSA provides a framework for the exploration of partial tendon transfers of ECRL and ECRB.