Bulletin of prosthetics research最新文献

A study was conducted to investigate the pressure relief patterns under the ischial tuberosities in group of 12 paraplegic subjects. A small electrical pressure transducer was taped over each ischial tuberosity, and each subject had a thermistor taped near one tuberosity. The subjects were instrumented in the morning and allowed to go about their normal activities for the day sitting on a 4-inch foam cushion. The subjects sat at pressures greater than 150, greater than 90, and greater than 30 mmHg for 17.6 percent, 53.5 percent, and 91.8 percent of the time, respectively. The subjects sat on the average for 10.1 min without doing a pushup with a duration greater than 1 sec and sat on the average for 29.6 min without doing a pushup with a duration greater than 5 sec. Two of the subjects sat for periods greater than 60 min for greater than 75 percent of the time (ignoring pushups less than 5 sec) and greater than 65 percent of the time ignoring pushups less than 1 sec. The average time between pushups was within the generally accepted limits to prevent ulcers--10-30 minutes. A few of the subjects had occasional long periods of uninterrupted pressure greater than what is thought to be required to produce ulcers--and did not develop them.

This report describes an attempt to conduct (in 1978 during a period of one week) an intensive, thorough, and objective evaluation of a prosthetic control system in such a manner that the evaluation avoids what are seen as shortcomings common among evaluation procedures described in the literature. The evaluation, in terms of benefits to patients, involved consideration on an interdisciplinary basis among an engineering team, prosthetics team, and therapy team. Nine below-elbow and two forequarter amputees participated. The device evaluated was the University of New Brunswick 3-state myoelectric control system, in the 12-volt version designed in 1975. This system is intended for use where there are not enough control sites to permit use of an Otto Bock or similar control system, and permits on/off control of a powered hand or other device in two directions from a single muscle. Observations on each patient by the 14-person evaluation team are summarized, and an Appendix presents questionnaires with summarized responses of the subjects and their families.

Detection of deviations in lower-limb joint movements derived during locomotion testing may be enhanced by displaying as a function of the gait cycle the algebraic difference between actual performance and a synthetic waveform. A synthetic waveform for a joint movement may be generated by applying Fourier series coefficients derived from a statistical treatment of test data characterizing the performance of normal healthy individuals walking at various velocities. Application of waveform specifics related to velocity yields a synthetic pattern serving as the criterion at the specific velocity demonstrated by a patient. The deviations, when plotted for the gait cycle, show the manner in which the actual waveform differs from the synthetic. At any increment of the gait cycle, the magnitude of the deviation and whether it is positive or negative can be determined. A positive deviation means that an expected angular position was exceeded, while a negative deviation means that an expected angular position was not reached. Individual signatures may be identified by the shape of the deviation pattern. Detection of the presence of oscillatory components in joint movements may be enhanced. Deviation patterns, developed from joint movements monitored bilaterally, often reveal compensatory activity with regard to the relative performances of the ipsilateral and contralateral limbs. Deviation amplitudes exceeding statistically determined boundaries for the synthetic waveform (e.g., two standard deviations) at specific zones of the support or wing phases facilitate identification of dysfunction. This paper describes the technique for deriving the deviation pattern, and touches upon its potential utility in evaluating locomotory performance of patients.

Prosthetics Research Study has developed a computerized automated system for the volumetric analysis of the residual limbs of amputees. Basically, this system utilizes the same principles as does normal, clinical fluid displacement volumetric analysis, with the addition of the following--if an object is suspended in a vertical cylinder into which water is being injected at a constant rate, then the rate of rise of the water will vary proportionally, at any point, with the cross-sectional area of the object. In this system, water is pumped into a Plexiglas cylinder of appropriate size so as to immerse a residual limb within a time frame of under ten seconds while a microcomputer records the water depth as a function of time. The rate of water depth rise is recorded for 256 levels during a measurement. These results are then analyzed comparatively, on a level-for-level basis, with similar rates generated with fluid pumped into the empty cylinder, thus generating 256 discrete cross-sectional-area parameters. These are then processed (in groups of eight) into 32 actual cross sections and displayed, graphed, or stored for purposes of comparison. Possible clinical application for this kind of device includes measurement of edema and other extremity volume changes with time, and measurement of muscle activity related to axial movements of muscle bulk.

Traditional studies of human movement by photographic methods require tedious, error-prone, and expensive data reduction. Various optoelectronic methods have been designed. A commercially available system, SELSPOT, purchased for the Cleveland VAMC Motion Study Laboratory, is described. Sequentially pulsed light-emitting-diode targets on the subject are observed, with data fed into a computer for combination with force plate data (Cohen, Orin, and Marsolais, Technical Note, BPR 10-33). Calibration methods, errors, and practical difficulties are described. Though problems remain after revisions (see progress reports in BPR), it is believed that SELSPOT offers potential for clinically useful real-time acquisition and analysis of three-dimensional data.

The extent of locomotion assistance gained through cane usage by those with hip disorders is assayed. Employing as a standard the propulsive impulse delivered by each lower limb of a healthy young male, the cane is shown to supply about one-fifth the equivalent impulse, aside from other possible benefits. Full test values are given for nine handicapped subjects.

Stresses developed within flesh in contact with a cushion are examined analytically. Compressive, tensile, and shear stresses within flesh in proximity to a bone are given as a function of cushion stiffness (major parameter) and the overall Poisson's ratio of flesh (minor parameter). It is shown that an individual already sitting on a soft cushion receives relatively minor benefit when a still softer cushion is substituted. This result follows from the fairly flat (saturated) trend of both shear and tensile stress with respect to cushion stiffness, once the soft cushion domain (less than 10 PSI) is entered. Only flesh normal stress (compression) responds significantly to incremental changes of stiffness within the soft cushion range; reducing the cushion stiffness 50 percent will typically reduce local compressive stress by roughly 20 percent. While such a gain is real, it is also modest.