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G F Harris

Publications and source records attributed to G F Harris.

12 recordsLinked to original sources
PubMed1991

A microprocessor-based data-acquisition system for measuring plantar pressures from ambulatory subjects.

We have developed a portable microprocessor-based data-acquisition system to measure discrete plantar pressures within the shoe from ambulatory subjects. The system offers improved accuracy, repeatability, portability, and flexibility not available in current commercial systems. It consists of 14 conductive polymer pressure sensors, 14 analog amplifiers, an 8-bit analog-to-digital converter, a microprocessor, 120 kbytes of memory space, and a parallel I/O interface. Seven pressure sensors are embedded within each insole and located at the posterior heel, anterior heel, the four metatarsal heads, and hallux of each foot. The system is capable of continuously sampling 14 channels of pressure data for 7 min at a 20-Hz sample rate. The recorded data are downloaded into a microcomputer for further processing, analysis, and display. Foot pressures have been acquired from a sensate subject during multiple walking trials.

Diagnosis, Computer-Assisted↗
PubMed1991

Foot pressure distribution during walking and shuffling.

The insensate foot is vulnerable to tissue damage from areas of repetitive, excessive pressures. It has been previously stated that a shuffling gait with short steps would increase the period of foot flat and thus minimize any excessive local plantar pressures. This theory was quantitatively evaluated with a portable, in-shoe pressure data-acquisition system. Seven pressure sensors were located in the left and right insoles under the metatarsal heads, hallux, and posterior and anterior heels. Plantar pressure data were acquired from ten able-bodied subjects during four minutes of continuous shuffling and walking at a metronome-controlled cadence. Peak pressures, foot-to-floor contact durations, and pressure-time integrals under each sensor during shuffling and walking were analyzed and compared. Peak pressures were decreased at all sensor sites during a shuffling gait. The greatest decreases were noted at the first and second metatarsals (up to 57.8%) and hallux (up to 63.2%). A 41.6% decrease in overall summated peak plantar pressures during shuffling was found. Foot-to-floor contact durations during shuffling were increased from 22.0% to 76.9% at all 14 sensor locations. Pressure-time integrals during shuffling were increased at the heels (up to 78.9%) and decreased at the metatarsal heads and great toes (up to 26.7%). There was a 3.3% increase in the overall summated pressure-time integral during shuffling. Our findings are consistent with the hypothesis that a shuffling gait increases the period of foot flat and the area of weight bearing, resulting in lower peak plantar pressures on any one area.

Adult↗
PubMed1989

Analysis of neuroelectric implant integrity.

A 10-year follow-up study of neuroelectric implant integrity has been completed for 27 subjects who were treated for movement disorders associated with cerebral palsy. Data used for analysis included X-ray material, clinical data, and results from electrophysiological testing. Of the 21 subjects with subcutaneous receivers placed in the thoracic region, 81% experienced wire (67%) or receiver (14%) failure. Of the 6 subjects with subcutaneous receivers placed in the occipital region, there were no wire failures and one (17%) receiver failure. The occipital units lasted a minimum of 5.2 years without complications, whereas the thoracic units failed as early as 6 months after surgery, and lasted an average of 3.8 years. All wire fractures occurred between C1 and T1. Two types of fracture occurred, one consisting of a clean break and the other consisting of a scenario of bending and kinking, then thinning and fraying, and finally progressive multiple fragmentation. With a few exceptions the clean breaks occurred between C1 and C3, while the fraying scenario occurred between C6 and T1. Mechanisms for failure are discussed, as are results from material tests of wire samples.

Adolescent↗
PubMed1989

Posteromedial release for idiopathic talipes equinovarus. A long-term follow-up study.

Eighteen children with 26 idiopathic talipes equinovarus deformities were treated by postermedial release (PR) in the interval between 1975 and 1980 and investigated retrospectively. Evaluations included physical examination, functional evaluation, roentgenographic evaluation, and evaluation of foot track tracing pattern. The average follow-up period was 8.2 years. Thirty percent had had previous tendo Achilles lengthenings and 15% had had previous lengthenings plus posterior capsulotomies. Based on Turco's criteria, the results of PR were graded 38.9% excellent, 26.9% good, 15.6% fair, and 18.6% failure.

Achilles Tendon↗
PubMed1987

Thoracic suspension: quantitative effects upon seating pressure and posture.

Seating pressure in 10 subjects using a thoracic suspension orthosis was studied quantitatively. Anterior, posterior, and ischial pressures were measured bilaterally both unsuspended and during a 90 to 120 minute interval while suspended. Significant decreases in seating pressure were noted following suspension, with a mean decrease of 59.8%. Significant changes in lateral support were noted with suspension, as was a reduction in both the absolute pressure and relative distribution of pressure to the ischial areas. Relative redistribution of pressure in the anterior-posterior direction was related to leg support condition. All subjects who presented with pressure sores healed subsequent to thoracic suspension. Those with spinal curvature showed a 10 to 20 degree correction immediately following suspension. This correction generally was not maintained, however, in a temporal analysis. The data indicates that thoracic suspension can effectively reduce seating pressure and alter lateral posture, while leg support condition has a greater effect upon anterior-posterior pressure distribution. The use of a seat cushion to prevent subject swinging while suspended did not adversely affect the overall suspended pressures in this study, although the subjects without seat cushions showed lower overall suspended pressures.

Adolescent↗
PubMed1987

A multichannel PWM telemetry system for kinematic gait analysis.

A multichannel biotelemetry system using pulse-width modulation-frequency modulation (PWM-FM) is described in detail for laboratory construction. Its application in a kinematic gait-analysis system is demonstrated, employing minimally encumbering electrogoniometry and foot-contact switches. The triaxial electrogoniometers sense rotational joint motion, and four foot-switches under the sole of each foot provide information on placement and temporal contact. Signals from the multiple sensors are amplified, encoded by pulse-width modulation, and transmitted at an FM radio frequency of 107 MHz. Received data are decoded and then sampled by a minicomputer for analysis. Results from a comparative study of kinematic gait in five normal subjects and five children with cerebral palsy demonstrate system effectiveness in providing quantitative data and various intrasubject and intersubject gait differences. Factors reviewed in the analysis include swing and stance times; cadence; hip-joint motion in sagittal, coronal, and transverse planes; and sequence of foot placement.

Analog-Digital Conversion↗