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Biomedical subjects

S Saha

Publications and source records attributed to S Saha.

At least 235 records · Page 13Linked to original sources
PubMed1987

Wave propagation characteristics in long bones to diagnose osteoporosis.

A mathematical model of stress wave propagation in bone is developed assuming a long bone to be a thick-walled, long cylindrical shell filled with a fluid. The calculated phase and group velocities in adult human femurs were found to be a function of the wave number and they were different for population groups of above and below 55 yr of age. The velocities were also sex dependent, being different for males and females of the same age group. Diagnostic methods based on the measurement of wave propagation characteristics may potentially be used to measure the structural changes in long bones due to osteoporosis.

Adult↗
PubMed1987

Bioethics and applied biomaterials.

Rapid growth in the field of applied biomaterials poses new ethical problems in the design, manufacture, evaluation, and regulation of medical devices and implants. This article addresses some of these ethical concerns and points out the ethical responsibilities of the scientists and engineers working in the field of biomaterials. The need for the development of a code of ethics by the Society for Biomaterials is also discussed.

Animal Welfare↗
PubMed1985

Wave propagation across a bony discontinuity simulating a healing fracture.

Stress wave propagation in a long bone with a progressively increasing defect in the bony cortex, simulating a healing fracture, was studied by recording the outputs of bonded semiconductor strain gages, proximal and distal to the defect. Statistically significant relations were found between the relative size of the discontinuity and the transmission coefficient, dispersion and transit time across the fracture. We also showed that the stress wave in a bone could be monitored from the vibration response of a traction pin, placed in a magnetic field. The results may be helpful for the development of new methods to measure the rate of fracture healing, as well as aiding our understanding of the dynamic loading of bone.

Femoral Fractures↗
PubMed1985

Osteoporosis.

Osteoporosis is the most common bone disorder in the United States. Bone mass is decreased, and porosity and fragility are increased. Dual-beam photon absorptiometry is currently considered the best detection technique. Prevention involves increased calcium intake and avoidance of diets high in protein and phosphates, excessive alcohol consumption and smoking. Estrogen therapy is recommended for most oophorectomized or postmenopausal women, at least for a few years. The addition of progestins to the regimen reduces the risk of endometrial cancer.

Aged↗
PubMed1985

Exomphalos.

Explore the source record for details and available documents.

Abnormalities, Multiple↗
PubMed1984

Mechanical properties of bone cement: a review.

Many authors have examined the mechanical properties of bone cement and the various factors that affect its mechanical behavior. This article presents a comprehensive survey on the reported mechanical properties of bone cement. Variables that influence the mechanical properties, such as handling characteristics, strain rate, loading modes, additives, porosity, blood inclusion, in vivo environment, temperature, etc. have also been reviewed. The importance of specifying these variables in reporting test results on the mechanical properties of bone cement is pointed out. Previous attempts to improve the mechanical properties of bone cement are also summarized. Future research areas important for fully characterizing the physical properties of PMMA are also suggested.

Anti-Bacterial Agents↗
PubMed1984

Improvement of mechanical properties of acrylic bone cement by fiber reinforcement.

Acrylic bone cement is significantly weaker and less stiff than compact bone. Bone cement is also weaker in tension than in compression. This limits its use in orthopaedics to areas where tensile stresses are minimum. We have attempted to improve the mechanical properties of PMMA by reinforcing it with metal wires, and graphite and aramid fibers. Normal, carbon fiber reinforced and aramid fiber reinforced bone cement specimens were tested in compression. Addition of a small percentage (1-2% by weight for carbon and up to 6% for aramid) of these fibers improved the mechanical properties significantly. Due to the improved mechanical properties of fiber reinforced bone cement, its clinical use may reduce the incidence of cement fracture and thus loosening of the prosthesis.

Biomechanical Phenomena↗
PubMed1984

Electro-mechanical behavior of wet bone--Part I: Theory.

The remodeling properties of bones due to various stimuli have been of substantial interest to the scientists. Examination of electro-mechanical properties of bone and their relation to remodeling and osteogenesis have been investigated mainly by experimental means. In this study, by using continuum physics, it is shown that the remodeling of bones can be formulated theoretically in terms of electrical and mechanical effects. The interactions among the constituents of bone (bone matrix, bone salts, electrolytes and hydrogen ions) and effects of various stimuli (mechanical, electrical and chemical) on the remodeling mechanism of bone tissue are interpreted with this model. Moreover, the stimulation of osteogenesis by electrical means is predicted.

Biomedical Engineering↗
PubMed1984

Electro-mechanical behavior of wet bone--Part II: Wave propagation.

In this study, a general mixture model, which was developed for wet bone, has been used to analyze the flexural wave propagation in long bones. The electrical conduction is taken into account as well as the piezo-electric properties of bone tissue. The general formulation is simplified and certain assumptions made to yield a particular set of equations. The solution of the magnetic induction vector outside the bone due to the mechanical wave propagation is obtained. The results are compared with a similar problem using dry bone. The results indicate that the electro-mechanical properties of bone tissue could be used for monitoring the rate of fracture healing in long bones.

Biomedical Engineering↗
PubMed1984

Electrical properties of bone. A review.

A review of the available data on the electrical properties (resistance, capacitance, dielectric constant, dielectric loss factor, and dissipation factor, etc.) of whole as well as standardized bone specimens suggest that impedance was lowest in the longitudinal direction and highest in the radial direction. This is further evidence of the anisotropic nature of bone. The electrical properties of fully hydrated bone were significantly different from those of dry and partially wet bone and these properties were highly frequency-dependent. Other variables that influence the electrical properties, such as moisture content, principles and methods of measurement, temperature, and pH and conductivity of the immersing fluid, etc., have also been reviewed. Delineation of these variables is important in reporting test results on the electrical properties of bone; only then can the data on different electrical properties of bone reported by various authors be compared. Future research is needed to characterize the effect of age, microstructure, mineral content, and various disease processes on the electrical properties of bone. Such information may lead to new insight on the role of electrical properties on bone remodeling. An understanding of the electrical behavior of bone is also important for the design of electrical stimulation devices and their proper use for maximum osteogenic effect.

Aging↗
PubMed1983

Strain-rate dependence of the compressive properties of normal and carbon-fiber-reinforced bone cement.

Normal and carbon-fiber-reinforced (1 wt. %) bone cement samples were tested in compression at various strain rates. Both the compressive strength and proportional limit increased in general with increasing strain rate. Similar strain-rate sensitivity was also shown by the carbon-fiber-reinforced bone cement. The mechanical properties, namely the modulus of elasticity, the proportional limit, and the compressive strength of the carbon-fiber-reinforced bone cement showed highly significant positive correlations with the strain rate.

Bone Cements↗