Interactive Graphics-Based Musculotendon Modeling for Reconstructive Surgery of the Hand.

This research has been directed at studying and developing a prototype research and clinical Computer Aided Design (CAD) tool to be used for planning tendon paths in hand reconstructive surgery. Of equal importance is the goal of having an educational tool for teaching hand biomechanics to students of this specialty. The application of CAD to rehabilitative surgery of the hand is a new field of endeavor. There are currently no existing commercial products designed to assist the orthopedic surgeon in planning these complex procedures. Additionally, orthopedic surgeons are not trained in mechanics, kinematics, math modeling, or the use of computers. It was also our intent to study the mechanisms and the efficacy of the application of CAD techniques to tendon transfer surgery. Through this research the following advances have been made: (1) creation of interactive 3D tendon path definition tools. (2) creation of software to calculate tendon excursion from an arbitrary tendon path crossing any number of joints. (3) creation of a model to interactively compute and display the forces in muscle and tendon. (4) creation of an environment to help surgeons evaluate the consequences of a simulated tendon transfer operation when a tendon is lengthened, rerouted, or reattached in a new location. It also has been one of the primary concerns in this research that an interactive graphical surgical workstation must present a natural, user-friendly environment to the orthopedic surgeon user. Additionally, this workstation must ultimately aid the surgeon in helping his patient or in doing his work more efficiently or more reliably. This work therefore includes a study of the usefulness of such a workstation as perceived by the orthopedic surgery community

A feasibility study of hand kinematics for EVA analysis using magnetic resonance imaging

A new method of analyzing the kinematics of joint motion is developed. Magnetic Resonance Imaging (MRI) offers several distinct advantages. Past methods of studying anatomic joint motion have usually centered on four approaches. These methods are x-ray projection, goniometric linkage analysis, sonic digitization, and landmark measurement of photogrammetry. Of these four, only x-ray is applicable for in vivo studies. The remaining three methods utilize other types of projections of inter-joint measurements, which can cause various types of error. MRI offers accuracy in measurement due to its tomographic nature (as opposed to projection) without the problems associated with x-ray dosage. Once the data acquisition of MR images was complete, the images were processed using a 3D volume rendering workstation. The metacarpalphalangeal (MCP) joint of the left index finger was selected and reconstructed into a three-dimensional graphic display. From the reconstructed volumetric images, measurements of the angles of movement of the applicable bones were obtained and processed by analyzing the screw motion of the MCP joint. Landmark positions were chosen at distinctive locations of the joint at fixed image threshold intensity levels to ensure repeatability. The primarily two dimensional planar motion of this joint was then studied using a method of constructing coordinate systems using three (or more) points. A transformation matrix based on a world coordinate system described the location and orientation of a local target coordinate system. Future research involving volume rendering of MRI data focusing on the internal kinematics of the hand's individual ligaments, cartilage, tendons, etc. will follow. Its findings will show the applicability of MRI to joint kinematics for gaining further knowledge of the hand-glove (power assisted) design for extravehicular activity (EVA)

Ergonomic evaluation of electric hedge trimmer using digital human modeling

Maintenance of gardens in public and owned premises is becoming costlier. The traditional ways of garden trimming requiring manual labor are becoming obsolete and electric trimmers are extensively being used in maintenance of gardens. While carrying out trimming activity with electric hedge trimmer, operator undergoes various awkward posture(s) resulting into musculoskeletal disorders. The present study is undertaken to evaluate existing electric hedge trimmer workstation and suggest suitable modifications in order to reduce drudgery. The study uses anthropometric data from the literature for the user population for modeling of manikin. The concept of digital human manikin (DHM) is used for modeling and simulation purpose. Here DHM tools in CATIA software such as Rapid Upper Limb Assessment (RULA), carry analysis and biomechanics analysis are used for the analysis. Study presents ergonomic evaluation of farm worker(s) in Maharashtra state of India operating electric hedge trimmer. RULA score of 6-7 showed that existing electric hedge trimmer workstation is not safe for workers and must be changed soon or immediately. However, carry analysis depicted that existing weight of trimmer is acceptable. Biomechanics single action analysis showed considerable values of moments and forces coming on the various joints and body parts. The study suggested new improved workstation for the electric hedge trimming operation on the basis of the RULA and biomechanics analysis. The improved workstation not only reduced RULA score to acceptable limit but also significantly reduced values of moments and forces coming on the body of worker. Thus, the study explored the potential of DHM technique in the product design, especially in ergonomic design of new workstations or to improve existing workstations

Moving Away From the Traditional Desktop Computer Workstations: Identifying Opportunities to Improve Upper Extremity Biomechanics

Statement of Problem: Office computer workers have elevated risks of adverse health outcome such as musculoskeletal disorders (MSDs) associated with computer work. Although they now have many alternatives, these modern computer workstations and associated technologies require new guidelines and recommendations for proper practice. We see this as an opportunity to improve current and future computer workstation designs through an ergonomics approach by improving users’ upper extremity biomechanics while interacting with these modern technologies. Method: The dissertation first utilized a psychophysical protocol to compare users’ self-selected set ups for sitting and standing computer workstations. Users’ biomechanics and perceived comfort across different computer tasks for the two workstations are then compared. Subsequently, a hand mapping technique was developed to evaluate effects of computer pointing devices on users’ hand posture and associated forearm muscle effort using 3-D motion analysis and surface electromyography. To improve mobile device ergonomics, we investigated tablet users’ biomechanical load, comfort level and performance while performing swipe actions at different tablet locations. Results: Different selected computer workstation set ups were found for sitting and standing. Compared to sitting, users while standing kept workstation components closer to their sternum and adopted a more neutral shoulder posture while working. However, users had greater wrist extension and started reporting more low back discomfort after 45 minutes. While investigating different computer pointing devices, we found device affordance associated with significantly different hand posture and forearm muscle load. Devices that required less holding and were centrally placed associated with more neutral shoulder and hand postures, with significantly less forearm muscle load. For tablet interface, swipe locations closer to the palm had significantly smaller forearm muscle load and more neutral posture across wrist and thumb joints. Conclusion: Through empirical results described in the dissertation, we demonstrated how users’ upper extremity biomechanics can provide insights into the complex interactions between users and modern computer workstations, both as a whole and with specific components. For technology innovation, ergonomics concepts and methodologies can be used to design future generation technologies that fit users’ physical capabilities to reduce MSDs risk while promoting performance

Human factors issues in performing life science experiments in a 0-G environment

An overview of the environmental conditions within the Spacelab and the planned Space Station Freedom is presented. How this environment causes specific Human Factors problems and the nature of design solutions are described. The impact of these problems and solutions on the performance of life science activities onboard Spacelab (SL) and Space Station Freedom (SSF) is discussed. The first area highlighted is contamination. The permanence of SSF in contrast to the two-week mission of SL has significant impacts on crew and specimen protection requirements and, thus, resource utilization. These requirements, in turn impose restrictions on working volumes, scheduling, training, and scope of experimental procedures. A second area is microgravity. This means that all specimens, materials, and apparatus must be restrained and carefully controlled. Because so much of the scientific activity must occur within restricted enclosures (gloveboxes), the provisions for restraint and control are made more complex. The third topic is crewmember biomechanics and the problems of movement and task performance in microgravity. In addition to the need to stabilize the body for the performance of tasks, performance of very sensitive tasks such as dissection is difficult. The issue of space sickness and adaption is considered in this context

Monocular tracking of the human arm in 3D: real-time implementation and experiments

We have developed a system capable of tracking a human arm in 3D and in real time. The system is based on a previously developed algorithm for 3D tracking which requires only a monocular view and no special markers on the body. In this paper we describe our real-time system and the insights gained from real-time experimentation

Defining Mobile Tech Posture: Prevalence and Position Among Millennials

Background: Mobile technologies have revolutionized daily life, significantly impacting ADLs and IADLs, as well as use of the hand and upper extremity. The primary objectives of this study are to (a) provide a formal goniometric description of mobile tech posture and (b) examine the prevalence of this sub-optimal posture among a group of graduate students. Method: This study used a cross-sectional study design. Comprehensive goniometric measurements of the neck and upper extremity were taken with participants (N = 46) using their mobile devices while texting or using the Internet. Handheld usage data from the iPhone Screen Time feature (iOS 12) was collected from a sample of healthy young adults. Results: The participants spent an average of 143 min per day using mobile technology. Comprehensive goniometric measurements highlighted positions of clinical concern, including cervical spine flexion, scapular protraction, elbow flexion, and wrist ulnar deviation with thumb flexion. Discussion: Findings aligned with prior research suggesting several hr per day of handheld mobile technology use among young adults. Mobile tech posture, as described by goniometric trends, includes several positions of concern for musculoskeletal imbalance or cumulative trauma disorders (e.g., cubital tunnel syndrome; De Quervain’s tenosynovitis). Further research is recommended to examine broader societal trends and impact on occupational performance

Walker-Assisted Gait in Rehabilitation: A Study of Biomechanics and Instrumentation

While walkers are commonly prescribed to improve patient stability and ambulatory ability, quantitative study of the biomechanical and functional requirements for effective walker use is limited. To date no one has addressed the changes in upper extremity kinetics that occur with the use of a standard walker, which was the objective of this study. A strain gauge-based walker instrumentation system was developed for the six degree-of-freedom measurement of resultant subject hand loads. The walker dynamometer was integrated with an upper extremity biomechanical model. Preliminary system data were collected for seven healthy, right-handed young adults following informed consent. Bilateral upper extremity kinematic data were acquired with a six camera Vicon motion analysis system using a Micro-VAX workstation. Internal joint moments at the wrist, elbow, and shoulder were determined in the three clinical planes using the inverse dynamics method. The walker dynamometer system allowed characterization of upper extremity loading demands. Significantly differing upper extremity loading patterns were Identified for three walker usage methods. Complete description of upper extremity kinetics and kinematics during walker-assisted gait may provide insight into walker design parameters and rehabilitative strategies

Ergonomic Models of Anthropometry, Human Biomechanics and Operator-Equipment Interfaces

The Committee on Human Factors was established in October 1980 by the Commission on Behavioral and Social Sciences and Education of the National Research Council. The committee is sponsored by the Office of Naval Research, the Air Force Office of Scientific Research, the Army Research Institute for the Behavioral and Social Sciences, the National Aeronautics and Space Administration, and the National Science Foundation. The workshop discussed the following: anthropometric models; biomechanical models; human-machine interface models; and research recommendations. A 17-page bibliography is included