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Biomedical subjects

S Hirokawa

Publications and source records attributed to S Hirokawa.

At least 37 records · Page 2Linked to original sources
PubMed1993

Biomechanics of the knee joint: a critical review.

The literature concerning kinematic and kinetic studies on the knee joint is comprehensively reviewed in this article. Also reviewed are studies of etiology and operative treatment of injury, as well as chronic disease such as dislocation, arthritis, and ligamentous rupture. This paper formulates experimental study and mathematical model analysis of the tibio-femoral and patello-femoral joints, respectively. The sections on experimental study cover the following: the tibio-femoral joint including load bearing capacity, knee laxity, ligamentous strain, articular geometry, and multiaxial movement; the patello-femoral joint including forces and stresses and patellar tracking patterns. Further, three items, considered as future problems, are discussed briefly: individual variations in material properties of the soft tissue and biphasic cartilage-bone structures, quantitative description of bone geometry, and quantitative determination of extreme tensions and distortions in connective tissues surrounding the knee.

Anterior Cruciate Ligament↗
PubMed1992

Synergistic stimulating effect between cyclic AMP and phorbol ester on plasminogen activator inhibitor type 2 production in human promyelocytic leukemia cell line PL-21.

We investigated the effect of agents which raise intracellular cyclic AMP (cAMP) and protein kinase C activators on the production of plasminogen activator inhibitor type-2 (PAI-2) by cultured human promyelocytic leukemia cell line, PL-21. As previously reported, PMA, a protein kinase C activator, showed a strong stimulating effect on the PAI-2 production. 1-oleoyl-2-acetyl-sn-glycerol (OAG), another synthetic protein kinase C activator, also showed a stimulating effect, which was, however, much less than that of PMA. The agents which raise intracellular cAMP, dibutyryl cAMP, 8-bromo cAMP, prostaglandin E1, and 3-isobutyl-1-methyl-xanthine, little increased the PAI-2 production when tested alone, but showed significant synergistic effects with PMA or OAG. The synergistic effect between PMA and dibutyryl cAMP was further verified by SDS-PAGE followed by immunoblotting using a monoclonal antibody against the PAI-2. It is interesting that the up-regulation of PAI-2 by cAMP and the synergistic effect with PKC activators forms a contrast to the previous reported bi-directional regulation of endothelial PAI-1 secretion by PKC activator and cAMP.

Bucladesine↗
PubMed1992

Effects of variation on extensor elements and operative procedures in patellofemoral disorders.

The influence of both insertion and strength/elasticity of each extensor in patellofemoral disorders was fully investigated through a two-dimensional mathematical model analysis in a horizontal plane, in combination with experimental design theory for analyzing mutually correlated influences. In the model, patellofemoral joint profiles projected on a horizontal plane have been expressed as spline functions. Each muscle of the quadriceps has been represented as a string pulled by the respective force; fascias and tendons have been represented by springs. Nonlinear equations have been constructed to represent the forces involved, and then solved by numerical iteration. An analysis of variance was performed on the data derived from a series of simulations, obtaining the following results. The strength of most extensors has been shown to have an influence on the increase in lateral contact force but not patellar translation. The tibial tubercle position has significant influence on both patellar translation and lateral contact force. The quadriceps' insertion on the femur has no influence on patellar translation. The insertion of each extensor on the patella has been shown to have a strong effect on patellar translation but not on contact force.

Aged↗
PubMed1992

[Activities of antithrombin III and heparin cofactor II in patients with pathologic blood coagulation conditions].

To investigate the physio-pathological functions of HC-II, assays for HC-II and AT-III were performed simultaneously on the samples from patients with DIC, liver dysfunction or renal disease from the three view points of consumption, production and loss of AT-III and HC-II. For the AT-III activity, two kinds of assays were applied: the automatic chromogenic substrate method and a newly developed clotting method which receives no effects from HC-II activity. The activity of HC-II was significantly lower than that of AT-III in patients with either DIC or liver dysfunction. However, no significant difference between HC-II and AT-III activities in patients with either thrombosis or renal disease. There were high correlations between HC-II and AT-III activities were found in the patients with liver dysfunction, suggesting that low activity was due to decreased production of HC-II and AT-III in the liver. It will be necessary that elucidation of the significant functions of HC-II not only in coagulation and hemostasis but also in regulation of local inflammation and invasion of neoplasm is necessary.

Adult↗
PubMed1991

The clinical pharmacokinetics of two different preparations of intrarectal ketoprofen following spinal or local anesthesia for anal surgery.

Two different preparations of commercially available suppositories containing Ketoprofen (KP) were administered to 49 patients immediately following anal surgery. The KP was prepared as either fatty suppositories (FS) or gelatin capsulated suppositories (GCS) and surgery was performed under either spinal (n = 37) or local anesthesia (n = 12). Similar results were observed in the kinetics of KP after both FS and GCS administration. The extent of bioavailability of the two dosage forms in the patient groups and control subjects (n = 10) were essentially equal. When the pharmacokinetic parameters of KP were compared between patient groups under spinal and local anesthesia, significant differences were found in the values of the peak level (C max), peak time (T max), and terminal phase half-life (t 1/2). The C max decreased by one-half, while the T max and t 1/2 increased twice and four times, respectively, in patient operated on under spinal anesthesia compared to those operated on under local anesthesia. The absorption rate constant (Ka) following spinal anesthesia was significantly less than that following local anesthesia or that of the healthy subjects (p less than 0.01). A "flip-flop" phenomena could be seen in the time profiles of plasma KP concentration following spinal anesthesia.

Administration, Rectal↗
PubMed1991

Three-dimensional mathematical model analysis of the patellofemoral joint.

This paper is concerned with a mathematical model analysis of the patellofemoral joint in the human knee, taking into account the articular surface geometry and mechanical properties of the ligament. It was made by the application of a computer-aided design theory (previously studied) and it was possible to express the articular surface geometries in a mathematical formulation and hence elucidate the joint movement mechanics. This method was then applied to a three-dimensional geometrical model of the patellofemoral joint. For the modelling of tendofemoral contact at large angles of knee flexion, the geodestic line theory was adopted. Applying the Newton-Raphson method and the Runge-Kutta Gil method to the model, variables such as patellar attitudes, patellofemoral contact force and tensile force of the patellar ligament for various knee flexion angles were computed. Applying the Hertzian elastic theory, contact stress was also computed. These results showed good agreement with the previously reported experimental results. As an application for the model, some parameter analyses were performed in terms of the contact stress variations and compared with those of the normal knee. The simulation results indicated that both the Q-angle increase and decrease increased contact stress, the patella alta showed undulating variations of stress while the patella infera showed little change of stress, and the tibial tuberositas elevation showed 20-30% reduction of stress.

Aged↗
PubMed1990

Energy consumption in paraplegic ambulation using the reciprocating gait orthosis and electric stimulation of the thigh muscles.

The energy consumption of six thoracic paraplegic persons ambulating in the reciprocating gait orthosis (RGO) with and without functional electric stimulation (FES) of their thigh muscles was determined as a function of walking speed. Plots of Kcal/kg-min and Kcal/kg-m vs walking speed in the RGO and RGO & FES were experimentally determined in this study and compared with the energy cost of walking in the long leg brace (LLB), the hip guidance orthosis (HGO), and an FES walking aid from data available in the literature. The RGO powered with electric stimulation of the thigh muscles required the lowest energy expenditure in Kcal/kg-m across the full range of walking speeds. The RGO, HGO, LLB, and FES walking orthoses ranked second, third, fourth, and fifth respectively. The lowest energy costs in Kcal/kg-min were associated with the RGO & FES, followed by the RGO, HGO, LLB, and FES for walking speeds below .28m/sec. At walking speeds higher than .28m/sec the HGO demonstrates lower energy cost followed by the RGO & FES, RGO, FES, and LLB. At the end of a 30-m walk, patients using the RGO & FES had a mean heart rate (HR) which was 12 beats/min less than the mean HR when using the RGO without FES, 31 beats/min less than the HR when using the LLB, and 42 beats/min less than the HR when using FES only. It was concluded that the FES-powered RGO combines the advantages of a passive mechanical orthosis with those of FES to provide substantial improvements in energy cost which may provide paraplegic persons with a mode of independent ambulation superior to the wheelchair.

Adult↗
PubMed1989

Biofeedback gait training system for temporal and distance factors.

A biofeedback gait-training system has been developed which can deal with the gait problems of all subjects in any phase of rehabilitation: measurement, analysis, training and/or evaluation. The system is composed of a measuring walkway and a training walker. The walkway can measure all the temporal and distance factors of gait. The walker, with two parallel grasping bars and a CRT monitor, moves automatically with the aid of servo-motors. The system provides visual feedback for distance factors of gait and audio feedback for temporal factors. During the single-support phase the desired foot position for the next step and the supporting foot position are displayed on the CRT. The actual position of the foot placement is then overlaid for the double support duration that follows. A trainee learns to place the foot in such a way as to overlap the desired with the actual foot stamps on the CRT. The desired temporal factors are provided by buzzer tones. A trainee tries to shorten or elongate the duration of the respective phase of the gait cycle in accordance with the tone. Some experiments on normal subjects and on some with degenerative knee joints verified that the biofeedback signals were utilised effectively and that the walker was of value for improving pathological gait.

Adult↗
PubMed1989

Normal gait characteristics under temporal and distance constraints.

Walking patterns of 53 males and 39 females, all in good health, were studied at slow, free, and fast speeds using a walkway system developed by the author. Three males and three females, also in good health, were then studied under constrained walking conditions such as rhythm constraint, speed coupled with constraint, walking up or down a slope, line stepping constraint, stepping onto a marked square, and starting/stopping of walking. In the first set of experiments, the following results were obtained. When increasing speed, the male had a tendency to increase step length and the female had a tendency to increase cadence. The relationships between the speed and the statistics of gait parameters, i.e. the coefficient of variation and the symmetry were examined. The data in this experiment were also applied to Grieve's gait equations which formulated the relationships between step frequency and speed, or between swing time and cycle time. In the second set of experiments the following results were obtained. Although rhythm constraint (induced by a metronome) resulted in no difference of gait between males and females, a difference did appear in the case of speed coupled with constraint. When walking up and down a slope, the ascent case showed a longer step length and a lower cadence compared with the descent. The idea of functional asymmetry, a supporting function of the left leg and a moving function of the right leg, is well accepted. However, in this study of the effect of line stepping constraints predominant right-left functional differences were found.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

The RGO Generation II: muscle stimulation powered orthosis as a practical walking system for thoracic paraplegics.

The RGO Generation II reciprocating gait orthosis was jointly developed by Louisiana State University Medical Center and Durr-Fillauer Medical, Inc, to overcome four problems encountered with the existing model: 1) The high energy cost of locomotion; 2) the great arm strength required for patients to stand up from the seated position without assistance; 3) difficulty (especially for patients with hamstring contracture) in remaining standing owing to failure of the knee latch to lock except in full extension; and 4) problems in balancing when ambulating on an incline. The RGO Generation II employs concurrent electrostimulation of the rectus femoris and hamstrings to assist in rising and balancing and a ratchet-type latching device to improve safety and stability in standing. Alternating stimulation of the rectus femoris and contralateral hamstrings are used for locomotion. Testing in six patients with thoracic paraplegia demonstrated an average 30+% reduction in energy expenditure at a walking speed of .05 m/s and a 15+% reduction at .37 m/s; improved mobility and better balance on inclines; and unassisted rising in all patients. Walking range was increased from an average of 100 m to an average of 800 m. More research is needed to provide stair-climbing ability and to further reduce energy expenditure.

Adult↗