Biomechanics

Biomechanics is a vast discipline within the field of Biomedical Engineering. It explores the underlying mechanics of how biological and physiological systems move. It encompasses important clinical applications to address questions related to medicine using engineering mechanics principles. Biomechanics includes interdisciplinary concepts from engineers, physicians, therapists, biologists, physicists, and mathematicians. Through their collaborative efforts, biomechanics research is ever changing and expanding, explaining new mechanisms and principles for dynamic human systems. Biomechanics is used to describe how the human body moves, walks, and breathes, in addition to how it responds to injury and rehabilitation. Advanced biomechanical modeling methods, such as inverse dynamics, finite element analysis, and musculoskeletal modeling are used to simulate and investigate human situations in regard to movement and injury. Biomechanical technologies are progressing to answer contemporary medical questions. The future of biomechanics is dependent on interdisciplinary research efforts and the education of tomorrow’s scientists

Upper Extremity Biomechanical Model for Evaluation of Pediatric Joint Demands during Wheelchair Mobility

Current methods for evaluating upper extremity (UE) dynamics during pediatric wheelchair use are limited. We propose a new model to characterize UE joint kinematics and kinetics during pediatric wheelchair mobility. The bilateral model is comprised of the thorax, clavicle, scapula, upper arm, forearm, and hand segments. The modeled joints include: sternoclavicular, acromioclavicular, glenohumeral, elbow and wrist. The model is complete and is currently undergoing pilot studies for clinical application. Results may provide considerable quantitative insight into pediatric UE joint dynamics to improve wheelchair prescription, training and long term care of children with orthopaedic disabilities

Biomechanical Model for Evaluation of Pediatric Upper Extremity Joint Dynamics During Wheelchair Mobility

Pediatric manual wheelchair users (MWU) require high joint demands on their upper extremity (UE) during wheelchair mobility, leading them to be at risk of developing pain and pathology. Studies have examined UE biomechanics during wheelchair mobility in the adult population; however, current methods for evaluating UE joint dynamics of pediatric MWU are limited. An inverse dynamics model is proposed to characterize three-dimensional UE joint kinematics and kinetics during pediatric wheelchair mobility using a SmartWheel instrumented handrim system. The bilateral model comprises thorax, clavicle, scapula, upper arm, forearm, and hand segments and includes the sternoclavicular, acromioclavicular, glenohumeral, elbow and wrist joints. A single 17 year-old male with a C7 spinal cord injury (SCI) was evaluated while propelling his wheelchair across a 15-meter walkway. The subject exhibited wrist extension angles up to 60°, large elbow ranges of motion and peak glenohumeral joint forces up to 10% body weight. Statistically significant asymmetry of the wrist, elbow, glenohumeral and acromioclavicular joints was detected by the model. As demonstrated, the custom bilateral UE pediatric model may provide considerable quantitative insight into UE joint dynamics to improve wheelchair prescription, training, rehabilitation and long-term care of children with orthopedic disabilities. Further research is warranted to evaluate pediatric wheelchair mobility in a larger population of children with SCI to investigate correlations to pain, function and transitional changes to adulthood

Biomechanics of Pediatric Manual Wheelchair Mobility

Currently, there is limited research of the biomechanics of pediatric manual wheelchair mobility. Specifically, the biomechanics of functional tasks and their relationship to joint pain and health is not well understood. To contribute to this knowledge gap, a quantitative rehabilitation approach was applied for characterizing upper extremity biomechanics of manual wheelchair mobility in children and adolescents during propulsion, starting, and stopping tasks. A Vicon motion analysis system captured movement, while a SmartWheel simultaneously collected three-dimensional forces and moments occurring at the handrim. A custom pediatric inverse dynamics model was used to evaluate three-dimensional upper extremity joint motions, forces, and moments of 14 children with spinal cord injury (SCI) during the functional tasks. Additionally, pain and health-related quality of life outcomes were assessed. This research found that joint demands are significantly different amongst functional tasks, with greatest demands placed on the shoulder during the starting task. Propulsion was significantly different from starting and stopping at all joints. We identified multiple stroke patterns used by the children, some of which are not standard in adults. One subject reported average daily pain, which was minimal. Lower than normal physical health and higher than normal mental health was found in this population. It can be concluded that functional tasks should be considered in addition to propulsion for rehabilitation and SCI treatment planning. This research provides wheelchair users and clinicians with a comprehensive, biomechanical, mobility assessment approach for wheelchair prescription, training, and long-term care of children with SCI

Upper Extremity Biomechanics of Children with Spinal Cord Injury during Wheelchair Mobility

While much work is being done evaluating the upper extremity joint dynamics of adult manual wheelchair propulsion, limited work has examined the pediatric population of manual wheelchair users. Our group used a custom pediatric biomechanical model to characterize the upper extremity joint dynamics of 12 children and adolescents with spinal cord injury (SCI) during wheelchair propulsion. Results show that loading appears to agree with that of adult manual wheelchair users, with the highest loading primarily seen at the glenohumeral joint. This is concerning due to the increased time of wheelchair use in the pediatric population and the impact of this loading during developmental years. This research may assist clinicians with improved mobility assessment methods, wheelchair prescription, training, and long-term care of children with orthopaedic disabilities

Use of a Dynamic Balance System to Quantify Postural Steadiness and Stability of Individuals with Lower-Limb Amputation: A Pilot Study

Introduction Despite rehabilitation and gait training, the gait of individuals with lower-limb amputation is often asymmetric and falls and/or fear of falling are common. Clinical assessments of balance and stability include the Berg BalanceScale and the Dynamic Gait Index. Biomechanical assessments, conducted largely in research laboratories, are more objective, quantitative, and may provide greater resolution. These biomechanical measures include postural sway during both unilateral and bilateral standing tasks and the dynamic postural response to applied or volitional perturbations. The objective of this study was to investigate the utility of a dynamic balance system, a relatively new clinical tool incorporating dual force plates similar to that used in research laboratories, to assess the postural steadiness and stability of a small, diverse population of persons with lower-limb amputation. The specific aim was to investigate whether differences in balance of persons with amputation due to changes in prosthetic componentry were reflected in the resultant data. Materials and Methods Dynamic balance testing was conducted using the Bertec Balance Advantage–Dynamic CDP system on five adult subjects with varying levels of lower-limb amputation. Trials were conducted in both the subjects\u27 current prosthesis and alternative prosthetic componentry after a 1-week acclimation period. Specific tasks included limits of stability, weight-bearing squats, and unilateral stance. Results Subjects had difficulty shifting their weight during the limits of stability task; both the maximum excursion and anteroposterior directional control varied with prosthetic componentry. Load sharing also varied with prosthetic componentry. Load sharing became more asymmetric as knee flexion increased during the weight-bearing bilateral squat tasks, with less weight supported on the prosthetic limb. Finally, the metrics for the unilateral stance task varied with prosthetic componentry. Conclusions The dynamic balance system tasks and related metrics demonstrated the potential to discern differences in balance in persons with amputation due to changes in prosthetic componentry. Further study is needed to investigate these parameters, their correlation with clinical measures of balance, and the effects of both prosthetic componentry and alignment

Motion Analysis of the Upper Extremities During Lofstrand Crutch-Assisted Gait in Children with Orthopaedic Disabilities

Background This paper presents a review of current state-of-the-art dynamic systems for quantifying the kinematics and kinetics of the joints of the upper extremities during Lofstrand crutch-assisted gait. The reviewed systems focus on the rehabilitation of children and adults with myelomeningocele (MM), cerebral palsy (CP), spinal cord injury (SCI), and osteogenesis imperfecta (OI). Forearm crutch systems have evolved from models with single- to multi-sensor hardware systems that can incorporate an increasing number of segments that are in compliance with the standards of the International Society of Biomechanics (ISB). Methods The initial system developed by our group was a single, six-axis, sensor-crutch design with an accompanying ISB-compliant, inverse dynamics model. The model consisted of seven upper body segments and two crutch segments. After thorough validation of the software and hardware, it was tested using nine children with MM. The join dynamics of the shoulder, elbow, and wrist were assessed during reciprocal and swing-through gait. Results The dynamic metrics of the upper extremeties, including the mean, range, and maximum force and moment, were found to be significantly different depending on the gait pattern. Joint forces were found to be the greatest during swing-through gait, with inferior forces reaching 50% of body weight. In order to improve upon the initial system, our group developed a four-sensor crutch system that measures the contributions of the crutch-cuff kinetics. The inverse dynamics model was enhanced by including crutch-cuff and sensor segments that also follow the ISB modeling standards. This system was used to model subjects with CP, SCI, and OI. Maximum joint forces were measured in the subject with CP, while maximum moments were measured in the subject with SCI. The subject with OI presented the smallest joint forces and moments. Discussion These novel model systems may be used to improve the quantification of joint dynamics during Lofstrand crutch-assisted gait. These methods may ultimately improve the identification of the risk factors for joint pathology and subsequent therapeutic planning and rehabilitation paradigms