Alyssa J. Schnorenberg

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.

Biomechanical response to ladder slipping events: Effects of hand placement

Ladder falling accidents are a significant, growing and severe occupational hazard. The factors that contribute to falls from ladders and specifically those that influence the motor response from ladder falls are not well understood. The aims of this research were to determine the effects of hand placement (rung versus rail) on muscle activation onset and peak activity timing in response to slipping on a ladder and to sequence the timing of events following slip initiation. Fifteen unexpected slips from 11 experienced ladder climbers were induced with a freely spinning rung under the foot, while subjects were randomly assigned to a rung versus rail hand grasping strategy. EMG onset time and peak activity time from five bilateral muscles (semitendinosis, vastus lateralis, triceps, biceps and anterior deltoid) were analyzed. Results indicated that significantly slower muscle activation onset and peak response times occurred during rail hand placement, suggesting that grasping ladder rungs may be preferable for improving the speed of the motor response. The triceps muscle activated and reached peak activity earlier in the slip indicating that subjects may initially extend their arms prior to generating hand forces. The study also revealed that slips tended to occur around the time that a foot and hand were in motion and there were just two points of contact (one hand and the slipping foot).

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.

Poster 44: Biomechanical Analysis of Wheelchair Athletes with Paraplegia during Cross-training Exercises

Objective: To evaluate the feasibility of wearing a non-invasive near infrared spectroscopy (NIRS) sensor measuring muscle oxygenation in the intact and residual limbs of individuals with limb loss during rehabilitation. Design: Observational study Setting: Military Advanced Training Center, Department of Rehabilitation. Participants: 20 U.S. Military male service members/veterans with unilateral lower limb amputation. Interventions: NIRS sensors were secured using elastic compression bandages to left and right quadriceps and biceps in participants with unilateral transtibial or transfemoral amputations to assess the feasibility of accurately reporting muscle oxygen saturation (SMO2) from intact and residual limbs during the Single Stage Treadmill and 6-Minute Walk Tests. Main Outcome Measures: SMO2 detection in intact and residual limbs, frequency of skin contact loss, percentage of subjects able to use the sensors without impeding exercise, participant and provider satisfaction. Results: NIRS sensor recordings were generally unaffected by perspiration during physical exertion and sensors successfully collected continuous SMO2 data. Socket and prosthetic fit were unaffected by sensor positioning on the thigh in participants with transtibial amputation; participant with a transfemoral amputation experienced a loss of suction suspension and change in socket fit as a result of sensor positioning. Brief sensor slippage and loss of skin contact occurred in 8 of 20 participants. Ninety-five percent of subjects stated that the sensors did not impede their ability to exercise and 70% stated that they would use the sensors to track their progress in exercise/recovery. Patients and providers expressed high satisfaction with the ability to monitor SMO2 during rehabilitation. Conclusions: NIRS sensors that measure SMO2 can be worn by individuals with limb loss during rehabilitation. Adding thigh sleeves may improve reliability for individuals with transtibial amputation. Analysis of data indicates both high patient and provider satisfaction. Additional investigation into the use of NIRS sensors as a longitudinal rehabilitation monitoring device is warranted. Level of Evidence: Level III

Evaluation of shoulder joint kinematics and muscle activity during geared and standard manual wheelchair mobility

Manual wheelchairs often lead to reduced independent function and an increase in shoulder pain and injuries. Geared manual wheelchairs may be a promising alternative that reduces the biomechanical demands of the shoulder needed for tasks such as propulsion on ramps and carpeted floors, while maximizing function and participation. To investigate the effects of geared manual wheelchair mobility during demanding tasks such as ramp ascent, six able-bodied subjects were evaluated in this study. Subjects were asked to propel both standard and geared manual wheelchairs on a tiled level floor and on a wheelchair ADA ramp. Shoulder muscle activity and glenohumeral joint kinematics were investigated. The results indicated that using geared manual wheelchair wheels did not alter the shoulder joint kinematics, but notably affected peak and integrated shoulder muscle activity. Muscle activity results normalized by stroke distance, indicated that using geared manual wheelchairs could decrease anterior deltoid, pectoralis major and infraspinatus muscle activity during ramp ascending, but on level floor infraspinatus muscle activity may increase. These results could have clinical implications for determining the types of functional mobility tasks for which geared manual wheelchairs are beneficial.

Evaluation of Pediatric Manual Wheelchair Mobility Using Advanced Biomechanical Methods

There is minimal research of upper extremity joint dynamics during pediatric wheelchair mobility despite the large number of children using manual wheelchairs. Special concern arises with the pediatric population, particularly in regard to the longer duration of wheelchair use, joint integrity, participation and community integration, and transitional care into adulthood. This study seeks to provide evaluation methods for characterizing the biomechanics of wheelchair use by children with spinal cord injury (SCI). Twelve subjects with SCI underwent motion analysis while they propelled their wheelchair at a self-selected speed and propulsion pattern. Upper extremity joint kinematics, forces, and moments were computed using inverse dynamics methods with our custom model. The glenohumeral joint displayed the largest average range of motion (ROM) at 47.1° in the sagittal plane and the largest average superiorly and anteriorly directed joint forces of 6.1% BW and 6.5% BW, respectively. The largest joint moments were 1.4% body weight times height (BW × H) of elbow flexion and 1.2% BW × H of glenohumeral joint extension. Pediatric manual wheelchair users demonstrating these high joint demands may be at risk for pain and upper limb injuries. These evaluation methods may be a useful tool for clinicians and therapists for pediatric wheelchair prescription and training.