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Biomedical subjects

M Arcan

Publications and source records attributed to M Arcan.

16 recordsLinked to original sources
PubMed2002

Analysis of muscular fatigue and foot stability during high-heeled gait.

Plantar pressure measurements and surface electromyography (EMG) were used to determine the effects of muscular fatigue induced by high-heeled gait. The medio-lateral (M/L) stability of the foot was characterized by measuring the M/L deviations of the center of pressure (COP) and correlating these data with fatigue of lower-limb muscles seen on EMG. EMG measurements from habitual high-heeled shoe wearers demonstrated an imbalance of gastrocnemius lateralis versus gastrocnemius medialis activity in fatigue conditions, which correlated with abnormal lateral shifts in the foot-ground or shoe-ground COP of these women.

Adult↗
PubMed2001

Integration of plantar soft tissue stiffness measurements in routine MRI of the diabetic foot.

OBJECTIVE: A method of measuring mechanical properties of plantar soft tissues in vivo by integrating a photoelastic technique into an MRI system is presented. BACKGROUND: Plantar tissue stiffening in the diabetic foot is associated with development of ulcers at the highest-pressure sites. MRI is used as an effective means of demonstrating tissue damage caused by diabetic ulceration. DESIGN: The new measurement method uses the indentation of a sphere into the plantar tissue, which is simultaneously scanned by MRI. The indentation force is obtained using the photoelastic technique while tissue deflection is measured on the MRI scans, to yield a characteristic load-displacement curve. METHODS: Applicability of the proposed method in characterizing the plantar tissue stiffness and indentation patterns of two young normal subjects and two older diabetic patients was tested. RESULTS: Significantly higher effective shear and elastic moduli were measured for the diabetic plantar tissue compared with that of normal. For the diabetic patients, local stiffness in proximity of the 1st metatarsal head was substantially larger than in other sites, and this could be associated with initial tissue ulceration at this location. RELEVANCE: The present method seems applicable as a practical means of identifying regions in the diabetic plantar tissue that are vulnerable to ulceration, and can be easily integrated into routine MRI scans for assessing tissue damage in these patients.

Case-Control Studies↗
PubMed2000

Modeling the body/chair interaction - an integrative experimental-numerical approach.

OBJECTIVE: To develop a systematic methodology towards a realistic model, of the body/chair interaction as a tool to analyze sitting posture and the cushioning system influence on the pelvis/lower back stress development. BACKGROUND: The model concept comprises an integrative structure including both the pelvis girdle and the lower spine, as well as the surrounding soft tissues with their specific characteristic behavior during sitting. METHODS: In vivo measurements were performed, in order to obtain a set of contact moduli defining the behavior of the soft tissues under tension during the sitting down process. Additionally in vivo indentation of a metal ball into the same soft tissues during sitting were performed in order to obtain the characteristic moduli. A finite element model was also developed for the specific analyses. RESULTS: Validation of the model was achieved by comparing its results with in vivo measurements of contact stresses developed between the body and a stiff target seat area. Loading the model using two alternative cushioning materials lead to different sets of stresses within the model; as the stiffness of the seat decreased, the peak contact stresses, as well as the internal body stresses substantially decreased. RELEVANCE: Body/chair interaction model methodology may be a practical means to analyze and design structures and materials in order to achieve more comfort during work or leisure, as well as for geriatric or impaired subjects.

Buttocks↗
PubMed2000

Biomechanical analysis of the three-dimensional foot structure during gait: a basic tool for clinical applications.

A novel three-dimensional numerical model of the foot, incorporating, for the first time in the literature, realistic geometric and material properties of both skeletal and soft tissue components of the foot, was developed for biomechanical analysis of its structural behavior during gait. A system of experimental methods, integrating the optical Contact Pressure Display (CPD) method for plantar pressure measurements and a Digital Radiographic Fluoroscopy (DRF) instrument for acquisition of skeletal motion during gait, was also developed in this study and subsequently used to build the foot model and validate its predictions. Using a Finite Element solver, the stress distribution within the foot structure was obtained and regions of elevated stresses for six subphases of the stance (initial-contact, heel-strike, midstance, forefoot-contact, push-off, and toe-off) were located. For each of these subphases, the model was adapted according to the corresponding fluoroscopic data, skeletal dynamics, and active muscle force loading. Validation of the stress state was achieved by comparing model predictions of contact stress distribution with respective CPD measurements. The presently developed measurement and numerical analysis tools open new approaches for clinical applications, from simulation of the development mechanisms of common foot disorders to pre- and post-interventional evaluation of their treatment.

Biomechanical Phenomena↗
PubMed1999

Performances of hill-type and neural network muscle models-toward a myosignal-based exoskeleton.

Muscle models are the essential components of any musculoskeletal simulation. In addition, muscle models which are incorporated in neural-based prosthetic and orthotic devices may significantly improve their performance. The aim of the study was to compare the performances of two types of muscle models in terms of predicting the moments developed at the human elbow joint complex based on joint kinematics and neuromuscular activity. The performance evaluation of the muscle models was required to implement them in a powered myosignal-driven exoskeleton (orthotic device). The experimental setup included a passive exoskeleton capable of measuring the joint kinematics and dynamics in addition to the muscle myosignal activity (EMG). Two types of models were developed and analyzed: (i) a Hill-based model and (ii) a neural network. The task, which was selected for evaluating the muscle models performance, was the flexion-extension movement of the forearm with a hand-held weight. For this task the muscle model inputs were the normalized neural activation levels of the four main flexor-extensor muscles of the elbow joint, and the elbow joint angle and angular velocity. Using this inputs, the muscle model predicted the moment applied on the elbow joint during the movement. Results indicated a good performance of the Hill model, although the neural network predictions appeared to be superior. Relative advantages and shortcomings of both approaches were presented and discussed.

Arm↗
PubMed1996

Shear modulus--measurement methodology with application to light-cured resin composites.

OBJECTIVES: This study was conducted to test a novel methodology for shear modulus determination of light-cured resin composites. METHODS: Using a butterfly-shaped specimen, a special loading device was able to apply pure uniform shear stress on a significant region of the specimen. Validation of the method was proven by photoelastic experiments. Shear modulus was directly obtained through shear stress-strain curve where the strains were measured by a shear strain gauge rosette. The composite materials analyzed were one microfill (Silux Plus, 3M Dental Products) and four hybrids (Brilliant, Coltene; Herculite XRV, Kerr; Z-100, 3M Dental Products; Graft LC, GC). An analysis of variance was used to evaluate the G modulus (p<0.01). RESULTS: Modulus values varied between 2.54-8.01 GPa. The microfilled material presented the lowest value, and Graft LC presented the highest value. A statistically significant difference was found between all materials (p<0.01). SIGNIFICANCE: The described methodology can also be applied to other restorative materials, as well as to adhesion strength measurements.

Analysis of Variance↗
PubMed1992

Foot-ground pressure pattern of flexible flatfoot in children, with and without correction of calcaneovalgus.

The footprint-measuring instrument was used to establish foot-ground pressure pattern of flexible flatfeet in male and female children, aged four to six years. Standing at ease, the children exerted most of their ground pressure by the posterior weight-bearing area (WBA). The rest was distributed between the middle and anterior WBAs, with the middle area usually exerting about 17%, and in extreme cases, as much as 30% of the total foot-ground pressure. Correcting valgus inclination of the calcaneus into neutral by inserting a leather wedge under the medial portion of the heel restored the longitudinal arch and the normal distribution of the foot-ground pressure of the standing child. The middle WBA exerted only 6% of the total pressure. This measuring system can differentiate between a normal foot, a flexible flatfoot, and a rigid flatfoot. It also can measure the exact amount of abnormal pressure being exerted by the middle WBA.

Biometry↗
PubMed1984

A method for in vivo quantitative occlusal strain and stress analysis.

A method to evaluate in vivo dental occlusal relationships by measuring strains and stresses, memorized in a thin wafer during occlusion, is presented. The method is based on the property of some polymers to memorize mechanical birefringence (the photoplastic phenomenon); it provides and records static and kinematic patterns related to the sequence of contacts during occlusion. This sequence determines the intensity levels of contacts according to impressions on the memorizing sheet. The method consists of observing and measuring, with an optical instrument, birefringence patterns appearing on a special memory sheet upon which a patient has occluded according to specific instructions. Two ways may be considered: the strain analysis and the stress analysis approach. The goal of the strain analysis approach is mostly clinical: to help attain harmonization of the static and kinematic occlusal patterns by detecting and eliminating prematurities and interferences through a step-by-step improvement of the strain uniformity. Other clinical uses include: Relating occlusal strain patterns to traumatic occlusion, bruxism or other functional disturbances. Diagnosing pain-dysfunction syndrome of supporting tissues in subjects with removable complete or partial dentures. Substantiating the comparative effect of supporting implants in combination with natural teeth in bridges, etc. The goal of the stress analysis approach is both clinical and theoretical, providing help in understanding the temporo-mandibular mechanical relationship.

Biomechanical Phenomena↗
PubMed1977

FGP assessment of postural disorders during the process of rehabilitation.

Application of the newly developed footground pressure pattern (F.G.P.) method to a number of cranio-cerebral injured patients (C.C.I.) as well as to hemiplegics and normal subjects is made. The postural disorders in standing are assessed through modifications of the F.G.P. and different stages of the rehabilitation process may be followed up. Special parameters of the standing posture, which characterize its disorders, are presented; a diagonal pressure pattern is described. The visual qualitative analysis of the pressure pattern may also be directly useful in the physiotherapy treatment.

Biomedical Engineering↗
PubMed1975

The effect of fluoride alone or fluoride followed by calcium and vitamin D on disuse osteoporosis of the rat tail vertebrae.

The therapeutic effect of fluoride alone or fluoride followed by calcium and vitamin D administration on the osteoporosis induced by immobilization of the rat tail vertebrae was investigated. Tail immobilization was carried out by musclectomy and tendectomy. After 60 days of immobilization, the vertebrae were examined for bone mass, breaking strength, ash percentage and Ca, P and F content. NaF or Ca and vitamin D as separate treatments improved the osteoporosis induced by immobilization. The effects of NaF treatment were more pronounced than those of Ca and vitamin D. NaF and NaF followed by Ca and vitamin D produced a similar degree of improvement in breaking strength. The fact that fluoride and calcium and vitamin D were administered separately and sequentially may explain the absence of a synergistic effect.

Animals↗
PubMed1975

A photoelastic force-indicating spreader for the correction of scoliosis.

The Harrington rod procedure for the surgical correction of scoliosis may be safely applied only if the spreader is instrumented with a force indicator. A method is described here of providing the surgeon with simple and direct means of controlling the force exerted with the spreader, using a photoelastic transducer with a special device for temperature compensation which is built into the spreader.

Elasticity↗