Construction and assessment of a computer graphics-based model for wheelchair propulsion

Upper limb overuse injuries are common in manual wheelchair using persons with spinal cord injury (SCI), especially those with tetraplegia. Biomechanical analyses involving kinetics, kinematics, and muscle mechanics provide an opportunity to identify modifiable risk factors associated with wheelchair propulsion and upper limb overuse injuries that may be used toward developing prevention and treatment interventions. However, these analyses are limited because they cannot estimate muscle forces in vivo. Patient-specific computer graphics-based models have enhanced biomechanical analyses by determining in vivo estimates of shoulder muscle and joint contact forces. Current models do not include deep shoulder muscles. Also, patient-specific models have not been generated for persons with tetraplegia, so the shoulder muscle contribution to propulsion in this population remains unknown. The goals of this project were to: (i) construct a dynamic, patient-specific model of the upper limb and trunk and (ii) use the model to determine the individual contributions of the shoulder complex muscles to wheelchair propulsion. OpenSim software was used to construct the model. The model has deep shoulder muscles not included in previous models: upper and middle trapezius, rhomboids major and serratus anterior. As a proof of concept, kinematic and kinetic data collected from a study participant with tetraplegia were incorporated with the model to generate dynamic simulations of wheelchair propulsion. These simulations included: inverse kinematics, inverse dynamics, and static optimization. Muscle contribution to propulsion was achieved by static optimization simulations. Muscles were further distinguished by their contribution to both the push and recovery phases of wheelchair propulsion. Results of the static optimization simulations determined that the serratus anterior was the greatest contributor to the push phase and the middle deltoid was the greatest contributor to the recovery phase. Cross correlation analyses revealed that 80% of the investigated muscles had moderate to strong relationships with the experimental electromyogram (EMG). Results from mean absolute error calculations revealed that, overall, the muscle activations determined by the model were within reasonable ranges of the experimental EMG. This was the first wheelchair propulsion study to compare estimated muscle forces with experimental fine-wire EMG collected from the participant investigated

Master of Science

thesisMusculoskeletal disorders, fatigue and other problems associated with the use of traditional, hand-rim wheelchairs have been documented in several studies. In response to these problems students in the Mechanical Engineering program at the University of Utah have created three alternative propulsion wheelchair prototypes. The three designs are the hand-lever, track-ball, and four-bar design. These wheelchair prototypes were designed to reduce injuries and fatigue, while maintaining safe, ergonomic function. This study tested and compared these prototypes, as well as a traditional hand-rim wheelchair. Each wheelchair propulsion system was evaluated using a wide spectrum of tests. This allowed the evaluation of each system's strengths and weaknesses. These tests included metabolic evaluation, maneuverability, usability and biomechanical modeling. The metabolic testing revealed that the upper body propulsion systems had lower energy demands than the lower body propulsion systems. Maneuverability testing found that the arm lever and hand-rim systems were the two systems which were most maneuverable. Biomechanical modeling noted that the hand-lever had lower force requirements and lowest joint moments than the hand-rim design and the four-bar had lower force requirements and lower joint moments than the trackball

One-Arm Drive Manual Wheelchair

Traditional manual wheelchairs use both arms for operation. Building upon previous projects, the goal of this project was to create an accessory, installable on a standard wheelchair, which would allow full control of a wheelchair with only one arm while addressing problems in other commercial and student designs. After preliminary analysis of three one-arm designs, a removable, lever-operated accessory was developed which could fit several popular wheelchair models. The propulsion uses one-way sprag clutches, the steering is cable based, and braking uses bicycle disc brakes. Specialized parts were used sparingly to improve manufacturability and cost. The accessory was evaluated against two other existing designs and showed marked improvement in propulsion, safety, and user comfort

Biomechanical Model of Pediatric Upper Extremity Dynamics During Wheelchair Mobility

Biomechanical analysis has been used by many to evaluate upper extremity (UE) motion during human movement, including during the use of assistive devices such as crutches and walkers. However, few studies have been conducted to examine the upper extremity kinetics during wheelchair mobility, specifically within the pediatric population. In 2000, 90% of wheelchair users (1.5 million people) in the United States were manual wheelchair users, requiring the use of their upper body to maneuver the wheelchair as well as perform other activities of daily living. Among children under the age of 18, the wheelchair was the most used assistive mobility device at 0.12% of the USA population (about 88,000 children). Of these children, 89.9% (79,000) use manual wheelchairs. Associated with the leading causes of assistive mobility device usage in children and adolescents, are severe cases of osteogenesis imperfecta (OI), cerebral palsy (CP), myelomeningocele (MM) and spinal cord injury (SCI). Once confined to a wheelchair, the upper extremities must take over the responsibilities of the lower extremities, including mobility and other activities of daily living. For many individuals who are wheelchair-bound since childhood, pain and other pathological symptoms present by their mid to late 20’s. Due to increased life expectancy and continual wheelchair use, these injuries may cause the user to have reduced, or loss of, independent function as they age, further decreasing quality-of-life. Better knowledge of upper extremity dynamics during wheelchair propulsion can improve understanding of the onset and propagation of UE pathologies. This may lead to improvements in wheelchair prescription, design, training, and long-term/transitional care. Thereby, pathology onset may be slowed or prevented, and quality of life restored. In order to better understand and model the UE joints during wheelchair mobility three main goals must be accomplished: 1. Create an upper extremity kinematic model including: additional segments, more accurate representations of segments and joint locations, consideration of ease of use in the clinical setting with children. 2. Create the corresponding kinetic model to determine the forces and moments occurring at each joint. 3. Implement the model and collect preliminary data from children with UE pathology

Structural analysis of a rugby wheelchair frame during field and laboratory tests

Structural analysis of a rugby wheelchair frame during field and laboratory tests with fem simulation and comparison between experimental and numerical resultsopenEmbargo per motivi di segretezza e/o di proprietà dei risultati e informazioni di enti esterni o aziende private che hanno partecipato alla realizzazione del lavoro di ricerca relativo alla tes

Assistive Mobility Device for an Elementary School Student with Arthrogryposis

An eight year old has Arthrogryposis, a condition which prevents him from using his arms and walking. He has access to several mobility devices; however, they are all unfit for use in a classroom setting. The student writes using his feet and works at a specialized desk. The goal of the project was to design a custom mobility device for the student’s specific needs. A device was created that could easily navigate in a classroom, while still providing a comfortable, ergonomic seat and a safe, stable platform that would allow him to work at his desk. The main features of the device include: a zero turning radius, lateral support, lockable wheels and adjustability for his growth. The device was successfully tested and met with enthusiastic acceptance from both the client and school personnel

The relationships between muscle weakness, wheelchair propulsion technique and upper extremity demand

textThere are millions of individuals throughout the world that rely on manual wheelchair propulsion as their primary method of mobility. Due to the considerable physical demand of wheelchair propulsion, these individuals are at an increased risk of developing upper extremity pain and injuries that can lead to a progressive decline in independence and quality of life. The overall goal of this research was to use a combination of experimental analyses and forward dynamics simulation techniques to gain an increased understanding of the relationships between muscle weakness, wheelchair propulsion technique and upper extremity demand. In the first study, a set of simulations was used to investigate the compensatory mechanisms that result from weakness in specific muscle groups. The simulation results suggested that the upper extremity musculature is robust to weakness in individual muscle groups as other muscles were able to compensate and restore normal propulsion mechanics. However, high stress levels and potentially harmful shifts in power generated by the rotator cuff muscles were observed. Such overuse could lead to the development of pain and injury in these muscles, suggesting that rehabilitation programs should target strengthening these muscles. In the second study, a set of objective quantitative parameters was developed to characterize kinematic hand patterns and assess the influence of propulsion speed and grade of incline on the patterns preferred by a group of 170 experienced manual wheelchair users. Increased propulsion speed resulted in a shift away from under-rim hand patterns while increased grade resulted in the hand remaining near the handrim throughout the propulsion cycle. These results identified how individuals modify their hand patterns in response to different propulsion conditions encountered in daily activities. In the third study, simulations of four commonly observed hand pattern types were generated. The simulations revealed the double loop and semi-circular patterns had the lowest overall muscle stress and total muscle power, suggesting that these hand patterns may reduce upper extremity demand. Together, the results of these studies have provided a scientific basis for designing rehabilitation and training programs aimed at reducing the prevalence of upper extremity injury and pain among individuals who use manual wheelchairs.Mechanical Engineerin

The ergonomics of wheelchair configuration for optimal sport performance

The ergonomics of wheelchair configuration for optimal sport performanc