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Biomedical subjects

J F Lehmann

Publications and source records attributed to J F Lehmann.

At least 37 records · Page 2Linked to original sources
PubMed1987

Gait abnormalities in hemiplegia: their correction by ankle-foot orthoses.

Hemiparetic gait is characterized by slow speed and poorly coordinated movements. Because the values of gait parameters vary with changes in speed, the slow speed that is typical of hemiparetic gait necessitates applying controls for the influence of speed when comparing hemiparetic and able-bodied persons. Gait kinetics and kinematics were measured in seven hemiparetic and seven able-bodied adults to compare their gait patterns at similar speeds and to assess the effectiveness of ankle-foot orthoses which were double-stopped in 5 degrees of dorsiflexion or 5 degrees of plantarflexion. Hemiparetic persons ambulating without the orthoses had a shorter step length, longer duration stance, and shorter duration swing than normal. They displayed greater than normal flexion of the affected hip during midstance, which, by putting the center of mass farther in front of the knee, may explain the increased knee extension moment due to vertical force. Affected hip adduction during single support was less in hemiparetic persons than in able-bodied persons, indicating a decreased lateral shift to the paretic side. During the swing phase, the affected limbs of hemiparetic persons were in less knee flexion and less dorsiflexion than normal, necessitating circumduction to achieve toe clearance. Ankle-foot orthoses increased walking speed to normalize heelstrike duration through use of an optimally adjusted plantarflexion stop. An improperly adjusted orthosis may produce an exaggerated knee flexion moment resulting in knee instability.

Aged↗
PubMed1986

Gait abnormalities in peroneal nerve paralysis and their corrections by orthoses: a biomechanical study.

Stroke, brain injury, incomplete spinal cord injuries, and peripheral neuropathies frequently result in dysfunction of the foot dorsiflexors and evertors. A controlled examination of aspects of these disabilities was conducted with normal volunteers who underwent a temporary peroneal nerve block. The effects of peroneal nerve paralysis were analyzed to quantitatively describe the resulting gait abnormalities and to assess the effectiveness of orthoses in restoring a normal gait pattern. Kinematic and kinetic measurements were made during normal ambulation, ambulation with a right peroneal nerve paralysis, and ambulation with a paralysis and an ankle-foot orthosis (AFO) with three different adjustments: a posterior stop set in 5 degrees plantarflexion, a posterior stop set in 5 degrees dorsiflexion, and spring-assisted dorsiflexion. The peroneal paralysis produced abnormalities during both the stance and swing phases of gait. During early stance there was a decrease in the length of the heelstrike phase and a reduction in the peak plantarflexion moment (p less than 0.01). During midstance there was an increase in the range of inversion-eversion achieved suggesting medial-lateral instability (p less than 0.01). The second vertical force peak and the aft-shear force peak were reduced (p less than 0.05) as were the peak dorsiflexion moment and the opposite steplength (p less than 0.01). These reductions are believed to be due to medial-lateral instability during pushoff. Subjects demonstrated a steppage gait during swing phase and increased inversion just prior to heelstrike (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Ankle-foot orthoses: effect on gait abnormalities in tibial nerve paralysis.

To study the biomechanical effects of gastrocnemius-soleus dysfunction and its potential remediation, the gait patterns of six able-bodied young adults were analyzed before and after induced temporary tibial nerve paralysis. Ambulation with the tibial nerve block was performed with and without the assistance of an ankle-foot orthosis (AFO) with a rigid anterior stop adjusted to either 5 degrees plantarflexion or 5 degrees dorsiflexion. The gait abnormalities resulting from tibial nerve paralysis include delayed advancement of the center of pressure, delayed ipsilateral heeloff and early contralateral heelstrike, decreased steplength, decreased ankle dorsiflexion moment, and increased knee flexion moment. This study provides quantitative information on the degree to which these abnormalities were corrected by appropriately adjusted AFOs. When using an AFO with an anterior stop, subjects with tibial nerve paralysis had improved advancement of the center of pressure (p less than 0.01). The body's ground reactive force line moved forward more normally, pivoting over the metatarsal head area and raising the heel earlier than observed with uncorrected tibial nerve paralysis, thus approximating the normal ankle dorsiflexion moment, normal timing of gait events, normal advancement of the hip, and normal steplength. The AFO with the anterior stop set at 5 degrees plantarflexion was more effective in restoring the values to normal than the AFO with the anterior stop set at 5 degrees dorsiflexion, but still did not consistently achieve the normal values. Only by using the AFO with the anterior stop set at 5 degrees plantarflexion was the increased knee flexion moment observed during the block reduced to normal levels (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Gait abnormalities in tibial nerve paralysis: a biomechanical study.

Gastrocnemius-soleus dysfunction is a frequent result of cauda equina lesions and peripheral neurophathies and of stroke and brain injury. Temporary tibial nerve paralysis constitutes a comparable laboratory condition which allows the controlled examination of aspects of these disabilities. The biomechanical effects of temporary tibial nerve paralysis in six normal young adult volunteers were examined to quantitatively define the gait abnormalities resulting from gastrocnemius-soleus paralysis and to provide a basis for the assessment of the effectiveness of different orthotic designs in restoring a normal gait pattern. The motion of the right lower extremity, ground reactive forces acting on the right lower extremity, timing of gait events and step length were recorded, first during normal ambulation and then during ambulation after a right tibial nerve block. Step length was reduced bilaterally after the nerve block (p less than 0.005); the reduction was greater for the left (unblocked) step than for the right (blocked) step (p less than 0.005). Right heeloff was delayed until the time of left heelstrike in all subjects after the right tibial block. Right heeloff occurred later (p less than 0.005) while left heelstrike occurred earlier than normal (p less than 0.005). The shorter left step length and earlier left heelstrike resulted from a reduction in the forward progression of the right hip (p less than 0.001). When subjects were deprived of the plantarflexion activity necessary to counteract dorsiflexion moments at the ankle, they delayed the forward progression of the center of pressure (p less than 0.001) to avoid the unstable collapse of the foot into dorsiflexion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Local muscle blood flow and temperature responses to 915MHz diathermy as simultaneously measured and numerically predicted.

The therapeutic benefits of diathermy are tied to the relationship thought to exist between tissue temperature and augmented blood flow (BF). To further define this relationship, simultaneous measurements of thigh muscle blood flow (MBF) and temperature have been made in 15 human subjects during 915MHz, direct-contact microwave diathermy (MWD) with simultaneous skin cooling. Tissue temperatures were measured invasively by special thermistor probes designed to minimize MW-induced artifacts, and the local rates of MBF were measured by monitoring the radioactive washout of injected Xenon133 (Xe133). The experimental results have shown that the initial MBF response is characterized by a "critical temperature" behavior such that rapid increases in MBF occur for tissues above approximately 42C when diathermy power is sufficient. A proportionality between tissue temperature and MBF has not been found. To provide more useful descriptions of the temperature fields and diathermic BF responses, two-dimensional numerical thermal simulations of six of the subjects' treatments were constructed and recorded. An average peak simulated MBF of 48ml/min-100g was found for these subjects, a level in excess of previous estimates for maximum perfusion during diathermy.

Body Temperature↗
PubMed1984

Computerized data management as an aid to clinical decision making in rehabilitation medicine.

A computerized data-base management system has been developed as a basis for clinical decision making in rehabilitation. The system allows efficient entry, storage, manipulation, and retrieval of patient performance data. With every new entry all previous entries can be displayed. Thus, identification of trends or rapid changes is far easier than perusing data entered into the hospital chart in a conventional way. The system also allows rapid review of all data entries of the entire rehabilitation team by any individual member. Additionally, correlation of variables can be obtained easily. Use of this system facilitates discontinuation of ineffective programs and identification of complications, thereby reducing hospital stay and cost.

Computers↗
PubMed1983

Electrical discontinuity of tissue substitute models at 27.12 MHz.

Tissue-substitute models consisting of layers of synthetic, electrically equivalent subcutaneous fat, muscle, and bone shaped in conformation with the normal anatomy are used for rapid determination of distribution of temperature and specific absorption rate throughout the tissues when exposed to electromagnetic radiation. The surfaces of the bisected models are approximated during a short exposure period, then separated and scanned with a thermograph. A method was developed to eliminate the electrical discontinuity at the bisected surfaces while allowing separation and subsequent thermographic scanning. A thin layer of silk screen wetted with propylene glycol saturated with sodium chloride was used at the fat interface and a 0.9% sodium chloride solution was used to wet the screen at the muscle interface to eliminate electrical discontinuity during exposure to 27.12-MHz diathermy. Tests showed that in the presence of an electrical discontinuity the heating pattern was grossly distorted. With the method used, the electrical discontinuity is minimized and the subsequent thermographic scanning reveals that the heating pattern is equivalent to that of an intact model.

Adipose Tissue↗
PubMed1983

Plastic ankle-foot orthoses: evaluation of function.

Plastic ankle-foot orthoses (PAFOs) are worn by persons with hemiplegia to correct gait abnormalities such as foot drop during swing and insufficient pushoff during stance. A PAFO should resist plantarflexion sufficiently to provide toe clearance during the swing phase of gait without excessively increasing the knee bending moment during heelstrike. It should resist dorsiflexion during late stance to raise the heel to simulate gastrocnemiussoleus muscle group function. Five PAFOs were evaluated as to the amount of plantarflexion-dorsiflexion resistance that was provided when worn by hemiplegic and able-bodied subjects. A self-aligning goniometer measured ankle angle as the subject walked, and a gait event marker system recorded occurrences of gait events. The Seattle design polypropylene orthosis which enclosed the malleoli was the least flexible; it provided the greatest plantarflexion resistance to ensure against toe drag during swing for patients with severe plantarflexion spasticity. It offered the greatest dorsiflexion resistance to provide a good substitute for the gastrocnemiussoleus during the latter part of stance as required by patients with flaccid plantarflexors and full ankle range of motion. Progressive trimming of the Seattle design polypropylene orthosis made it more flexible and comparable in function to the commercially available Engen and Teufel orthoses. The latter 2 orthoses did not provide a pushoff substitute as well as the Seattle design orthosis which enclosed the malleoli, but they did provide an adequate amount of toe clearance during swing. The more flexible orthoses would be appropriate for subjects with mild to moderate plantarflexor spasticity.

Aged↗
PubMed1983

Heating patterns produced by shortwave diathermy applicators in tissue substitute models.

To be a deep-heating modality, shortwave diathermy applicators have to heat the musculature more than the subcutaneous fat. In this study, commercially available and prototype shortwave diathermy applicators were tested using tissue substitute models which allow rapid thermographic scanning of the initial linear transient temperature rise in the subcutaneous fat and muscle. The specific absorption rates (SAR) of the electromagnetic radiation were calculated throughout the tissues. Great differences were found in the deep-heating capability of these applicators. Some of the applicators heated the subcutaneous fat more than the muscle, while others were more efficient in heating the musculature.

Adipose Tissue↗
PubMed1983

Microwave diathermy: effects on experimental muscle hematoma resolution.

The resolution of a muscular hematoma is an important step in the recovery from a muscle injury. Because heat application has been advocated to accelerate this resolution, the effectiveness of microwave diathermy as a means of selectively heating the musculature was studied. For this purpose muscular hematomas were formed in 6 pigs by bilateral injections of blood labeled with the radioisotope chromium-51 (Cr51) into the biceps femoris muscle. One hematoma site was heated with microwave diathermy and the opposite side served as a control. The tissue temperature at the hematoma site was shown to be in the therapeutic range of 42 to 45C, which would cause a maximal local blood flow response. A decay curve was formed by counting the radioactivity of the hematoma site with a scintillation counter. Best fit lines fitted to the decay curves to determine effective half-life values showed that the treated side had a significantly shorter washout time than the control side. This result supports the use of heat as an adjunct to other therapy aimed at resolution of muscular hematomas.

Animals↗
PubMed1982

Determination of perfusion field during local hyperthermia with the aid of finite element thermal models.

Two-dimensional transient thermal models of human thighs undergoing microwave diathermy are developed with the aid of experimental data to shed light on the blood flow response occurring during local hyperthermia in muscle. The experimental data were taken from tests on six human subjects treated with a 915-Mz, direct-contact microwave diathermy device which incorporated a system for simultaneously cooling the skin surface with a cold air stream. The numerically calculated perfusion fields were determined by systematically varying a model's blood flow response to the temperature stimulus until good agreement between the experimental and model temperature fields were achieved. The model blood flow values were then checked against those measured in the human experiments via xenon 133 washout and good agreement here was also found. The future use of models of this type in clinical diagnosis and hyperthermic treatment is proposed.

Diathermy↗
PubMed1982

Knee moments: origin in normal ambulation and their modification by double-stopped ankle-foot orthoses.

While the primary function of an ankle-foot orthosis is to stabilize the ankle complex, these devices often cause an unstable knee joint. The effect of a double upright ankle-foot orthosis on knee stability was evaluated during the stance phase of the walking cycle. The external moments applied to the knee in the anteroposterior plane were determined by measuring the ground reaction forces and the position of the knee with respect to these forces. Total knee moment and individual moment contributions of the fore/aft shear and vertical ground reaction forces were analyzed. Moments generated during normal ambulation were compared with those generated by an ankle-foot orthosis with an adjustable double stop. Knee moment components due to fore/aft shear and vertical ground reaction forces tended to counterbalance each other, minimizing the magnitudes of total knee moment. Fore/aft shear moment was most affected by the magnitude of the fore/aft shear force and had the major effect on total knee moment when the fore/aft shear force was peaking during the heel-strike and push-off phases. The vertical force moment was most affected by the length of the moment arm (position of knee center with respect to force) rather than magnitude of force, and had the major effect on total knee moment during midstance phase.

Adult↗
PubMed1980

Double-stopped ankle-foot orthosis in flaccid peroneal and tibial paralysis: evaluation of function.

This study was undertaken to evaluate how effectively an ankle-foot orthosis can substitute for paralyzed musculature, and to determine the forces it sustains in so doing. Timing of the events of gait, the ground reaction forces, their magnitude and location, and the brace moments were studied. Midstance phase was found lengthened at the expense of push-off phase. During push-off, vertical loading and posterior shear were markedly reduced by tibial block. Also, the dorsiflexion moment in the orthosis was correspondingly increased. The orthosis was found to substitute for muscle function in that it approximates the foot-ankle motion of heel-strike and allows a push-off substitute.

Adult↗
PubMed1978

Temperatures in human thighs after hot pack treatment followed by ultrasound.

Temperature distributions were measured in the anterior thigh of human volunteers after preheating with a hot pack followed by ultrasound, a frequently used therapeutic procedure. The skin surface temperature is elevated by this procedure but the highest temperature is still produced at the bone-muscle interface at the end of the treatment session.

Adult↗