Encouraging students with disabilities to pursue careers in bioengineering.
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Biomedical Engineering↗
Biomedical subjects
M L Boninger
Publications and source records attributed to M L Boninger.
Displacement between the seating surface and hybrid test dummy during transitions with a variable configuration wheelchair: a technical note.
Changing seating posture can extend the amount of time a person can safely remain seated without damaging tissue or becoming fatigued. The Excelsior is an electrically powered wheelchair that utilizes sit-to-stand (STS) and sit-to-recline (STR) motions to aid in pressure relief. The motion of the wheelchair seating system must closely follow anatomical paths or ulcers may develop from the resulting shear forces. Displacement between the person and the wheelchair seating surface is one measure of these shear forces. The displacement between a Hybrid II 50th percentile anthropometric test dummy (ATD) and the seating surface of the Excelsior wheelchair was examined during STS and STR with two cushions, a Jay Active and a low-profile Roho cushion. The difference between the backrest and ATD back angles were 4.29 degrees +/- 2.13 degrees and 1.78 degrees +/- 1.73 degrees for the Roho and Jay cushions respectively during STS and 3.32 degrees +/- 4.21 degrees and 10.71 degrees +/- 6.20 degrees during STR. These were statistically significant at p<.05. During STS, shear displacement between the Hybrid II back and Excelsior backrest did not exceed 1.5 cm for either cushion. ATD thigh-to-seat displacements were 2.5 cm for the Jay and 3.0 cm for the Roho cushion. STR produced dummy thigh-to-seat displacements of 1.5 cm and 3.5 cm for the Jay and Roho cushions respectively. Shear displacement in the ATD back was about 3.5 cm for the Roho and 6 cm for the Jay. The latter displacement should be reduced; however, the other conditions are marginal or acceptable. Hysteresis was acceptable or better for all cushion/motion combinations, with the highest net displacement of about 2.5 cm.
Biomechanical Phenomena↗
Dynamic calibration of a wheelchair dynamometer.
The inertia and resistance of a wheelchair dynamometer must be determined in order to compare the results of one study to another, independent of the type of device used. The purpose of this study was to describe and implement a dynamic calibration test for characterizing the electro-mechanical properties of a dynamometer. The inertia, the viscous friction, the kinetic friction, the motor back-electromotive force constant, and the motor constant were calculated using three different methods. The methodology based on a dynamic calibration test along with a nonlinear regression analysis produced the best results. The coefficient of determination comparing the dynamometer model output to the measured angular velocity and torque was 0.999 for a ramp input and 0.989 for a sinusoidal input. The inertia and resistance were determined for the rollers and the wheelchair wheels. The calculation of the electro-mechanical parameters allows for the complete description of the propulsive torque produced by an individual, given only the angular velocity and acceleration. The measurement of the electro-mechanical properties of the dynamometer as well as the wheelchair/human system provides the information necessary to simulate real-world conditions.
Calibration↗
Predictive factors for successful early prosthetic ambulation among lower-limb amputees.
OBJECTIVE: To predict successful prosthetic ambulation for patients immediately transferred to an inpatient rehabilitation facility after amputation surgery. METHODS: Seventy-five individuals with lower-limb amputation were studied at a tertiary acute care and rehabilitation facility. Successful prosthetic ambulation, defined as the ability to ambulate with a prosthesis at least 45 m, was measured in addition to other key demographic and medical factors. RESULTS: Sixty-eight percent were successful prosthetic ambulators at rehabilitation discharge. The absence of residual-limb contracture and a longer length of stay during rehabilitation showed a significant relationship to successful prosthetic ambulation with regression analysis. Younger age was modestly correlated to outcome. There were no significant differences when comparing success of the early rehabilitation program with surgical level or etiology of amputation. For successful prosthetic users, mean wear time at rehabilitation discharge was 5.7 hours with a mean distance walked of 67 m. Of those who failed this approach, 70% were related to a failure of wound healing. CONCLUSIONS: In this cohort, 68% of patients who were selected for a trial of early prosthetic rehabilitation ambulated using a prosthesis at rehabilitation discharge. This approach appears to be more effective for younger patients without contractures who are medically stable to participate in the rehabilitation process.
Adult↗
Shoulder imaging abnormalities in individuals with paraplegia.
Shoulder pain and rotator cuff tears are highly prevalent in individuals with paraplegia (PP). The purpose of this study was to use magnetic resonance imaging (MRI), plain radiographs, questionnaires, and physical examination to gain insight into the prevalence of shoulder disorders in individuals with PP. A total of 28 individuals with PP was recruited (mean age=35; mean year from injury=11.5). Each subject completed a questionnaire designed to identify arm pain, had a standard physical examination focusing on the shoulder, and underwent imaging studies (radiographic and MRI). Nine of the thirty-two subjects (36 percent) experienced shoulder pain in the month prior to testing. The MRI studies documented only one rotator cuff tear. Five subjects showed osteolysis of the distal clavicle by plain radiographic study. In two subjects this was seen bilaterally. Although no relationship was seen between pain and imaging abnormalities, stepwise linear regressions found a statistically significant positive relationship between imaging abnormalities and body mass index (BMI) (radiographic: beta= 0.56, p<0.01; MRI: beta=0.52, p<0.01). This study found a low prevalence of rotator cuff tears and a high prevalence of distal clavicle osteolysis in a sample of relatively young individuals with PP. Although there was only one tear identified by MRI, a number of subclinical abnormalities were seen and found to correlate with BMI.
Adolescent↗
Analysis of vibrations induced during wheelchair propulsion.
Little is known about how dynamic acceleration affects wheelchair-rider comfort. The current study was to test both the operation of an instrumented wheelchair by a wheelchair user over a Simulated Road Course (SRC) and the operation of the same instrumented wheelchair during normal daily activities (a field test) by test subjects. Sixteen subjects participated in the protocol. A SRC allowed collection of data from wheelchair users traversing obstacles similar to those experienced by a typical wheelchair user. The SRC consisted of eight obstacles fixed rigidly to a flat concrete surface. The field test began after the conclusion of the SRC test. Transfer functions were derived for all 16 subjects. It is clear from the results that for the SRC, the acceleration at the wheelchair frame exceeded the 8-h "fatigue-decreased performance boundary." A vertical acceleration resonant peak was evident for eight of the subjects. The average for these peaks, when present, was 8.1 Hz. This frequency is higher than the 4-6 Hz resonant peak presented in the literature for a seated human subject. This discrepancy could be due to different levels of trunk control between wheelchair users in this study and ambulatory subjects used in the literature. Subjects and their wheelchairs were exposed to a few, high-acceleration events rather than consistent, small-magnitude accelerations during the field test. This study indicates that vibration may be a contributing factor to fatigue among manual wheelchair users, which could lead to injury.
Acceleration↗