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Biomedical subjects

S Pal

Publications and source records attributed to S Pal.

At least 199 records · Page 11Linked to original sources
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

Improved preservation medium for Campylobacter jejuni.

An egg-based medium was found to be superior to the conventional Wang transport medium and the recently developed biphasic medium for the preservation of Campylobacter jejuni in the laboratory. Strains of C. jejuni preserved in egg-based medium maintained at 4 degrees C were viable for over 3 months. The survival of C. jejuni in egg-based medium held at room temperature (27 +/- 2 degrees C) was also relatively longer than in Wang transport medium and biphasic medium.

Animals↗
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↗
PubMed1983

The assessment of in vivo bone condition in humans by impact response measurement.

Transverse impact tests were conducted on the lower legs of 30 human volunteers and on 18 embalmed human tibiae. The impact was produced by an instrumented hammer and the response was monitored by an accelerometer. The apparent flexural wave velocity, measured from the force and acceleration records, showed significant negative correlations with the ages of both the male and female volunteer groups. The decrease in the velocity with increasing age was more pronounced in the female group. Two patients with bone diseases also manifested a much lower wave velocity compared to that from a normal person of similar age. Results of in vitro impact tests on human tibiae also showed that the wave velocity had: (1) a significant positive correlation with the mass/unit length of bone and (2) a significant negative correlation with the degree of osteoporosis in the bones.

Adolescent↗
PubMed1983

Cholesterol solubility in mixed micellar solutions of ionic and non-ionic surfactants.

The solubility of cholesterol in mixed aqueous ionic and non-ionic micellar systems in the presence and absence of salts and ionic dyes has been studied. The mixed micellar system of cetyl trimethyl ammonium bromide and Triton X-100 solubilized more cholesterol than a system consisting of sodium dodecyl sulfate and Triton X-100. The influence of salts and dyes on these systems was moderate but different for each system. Sodium chloride, calcium chloride, and sodium citrate had mild effects on both the systems, whereas the effects of potassium hydrogen phthalate, sodium salicylate, and sodium acetyl salicylate were dramatic. The free energy, enthalpy, and entropy of solution were determined. On the basis of the energetics, the nature of the mixed systems is discussed. Solubility of cholesterol was found to bear a direct correlation with the total lipid content.

Cetrimonium↗
PubMed1982

Stress relaxation and creep behaviour of normal and carbon fibre reinforced acrylic bone cement.

Room temperature compression creep and stress relaxation behaviour of normal as well as carbon fibre reinforced bone cement was studied and their properties compared. It was observed that increased deformation due to creep in 24 h was about 70% of the initial strain (due to applied constant stress fo 10.5 MN/m2) for normal PMMA and this could be reduced to 45% of the initial strain by carbon fibre reinforcement. Surgical grade PMMA, when subjected to 1% constant strain, showed an average stress-relaxation by 24% in eight hours. Percentage of stress-relaxation was somewhat more for carbon fibre reinforced bone cement even though the level of stress was much higher compared to normal PMMA.

Bone Cements↗
PubMed1982

Surgical drilling: design and performance of an improved drill.

The majority of twist drills used in orthopaedics are very similar to chisel pointed metal drilling bits. Modifications usually observed are reduction of the point angle to 90 deg and sometimes grinding of the entire cutting lip at 0 deg rake angle, which appeared to have been made arbitrarily without any advantage. We have attempted to design a surgical drill bit with the objective of minimization of the drilling thrust and temperature and effective removal of bone chips. Our results showed that the presence of the chisel edge was mainly responsible for increasing the thrust force and the temperature developed. The effects of a constant feed rate and thrust on the peak temperature were also examined. The combined effect of the helix and the point angles on the rake angle which in turn determines the cutting efficiency was analyzed for various types of surgical bits. Based on our results and previously published data from the literature an optimized drill bit was designed with a split point, a point angle of 118 deg, a parabolic flute, and a helix angle of 36 deg and its performance was compared with other existing surgical drill bits. For drilling in compact bone, the new design decreased the thrust load by 45 percent an the peak temperature rise by 41 percent. Similar improvements were also recorded for drilling bone cement. The time of drilling a bone cortex was also significantly reduced and "walking" on the curved bone surface was eliminated and dimensional tolerance on hole sizes was improved. The new design is likely to reduce the time of surgery and also minimize the tissue damage.

Biomechanical Phenomena↗