Search PubMed⌕ Search

Biomedical subjects

S Saha

Publications and source records attributed to S Saha.

At least 253 records · Page 14Linked to original sources
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

Stress wave propagation in bone.

The traveling wave characteristics for a single compressive pulse were studied in fresh and embalmed human long bones. The stress wave was generated by the longitudinal impact of a steel ball on one end of a bone and was monitored by bonded strain gages. The dynamic properties, namely velocity, attenuation coefficient and dispersion were correlated with the mineral density, porosity, and cross-sectional area of the specimens. Statistically significant relationships were found between several of these parameters. These stress wave propagation characteristics are important for our understanding of the dynamic loading of bone and they may also provide a basis for the development of noninvasive techniques for studies of diseased or fractured bone.

Bone and Bones↗
PubMed1983

A variable pulse-burst electromagnetic generator for electrical stimulation of biological systems.

A variable frequency-burst type, electromagnetic pulse generator has been developed to optimize the effect of electrical stimulation on bone growth. Using a pair of coils, with 100 turns and 18-gauge wire, the instrument can generate a maximum magnetic field of 300 Gauss. Its pulse repetition frequency can be varied from 10 Hz to 2 KHz and the duty cycle, consisting of several short carrier frequency pulses, can be varied up to 95%. This design also permits the period of the carrier pulse to be changed.

Animals↗
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↗
PubMed1981

Imaging of irradiated liver with Tc-99m-sulfur colloid and Tc-99m-IDA.

In three cases, irradiated regions of liver failed to concentrate Tc-99m-sulfur colloid. In two of these three, imaging with Tc-99m-acetanilide iminodiacetic acid (IDA) agents within five days showed near normal hepatic uptake of this hepatobiliary imaging agent. The hepatic parenchymal cells may be imaged with Tc-99m-IDA in some irradiated regions of liver, despite loss of reticuloendothelial cell function.

Aged↗
PubMed1980

Long-term torsional creep in compact bone.

Bovine bone specimens loaded in torsion for periods of time exceeding one month exhibit pronounced time-dependent effects. The final strain exceeded the initial strain by a factor of more than four in some cases. Creep failure was observed in two cases. The effects are not attributable to prolonged immersion in Ringer's solution.

Animals↗
PubMed1980

The effect of axial tension on the load bearing capacity of traction pins.

Skeletal traction is often used in the conservative treatment of fractures. Although a small diameter traction pin causes less trauma, its use is limited by the strength of the pin and the holding power of the bone. Both theoretical analysis and in vitro experiments were conducted to investigate the bending resistance of traction pins subjected to an applied traction force. The results of this study indicate that thin K-wires could be prevented by applying tension. The possibility of a pin cutting through bone is minimal if the cortical bone structure of the patient is normal. However, further in vivo study is necessary to ascertain whether necrosis might occur due to excessive contact stress between the pin and the bone.

Bone and Bones↗
PubMed1979

Cement line motion in bone.

Compact bovine bone subjected to constant torsional load for long periods of time exhibits large anelastic effects. Displacements occur at the cement lines and are responsible for part or all of the long-term deformation. The absence of an asymptotic creep strain is consistent with an interpretation of the cement line as a viscous interface.

Animals↗
PubMed1979

Bending properties of wire-reinforced bone cement for applications in spinal fixation.

PMMA beam specimens were tested in four-point bending to determine if the bending strength of acrylic bone cement, as used in posterior spinal fusion, could be improved by metal-wire reinforcement. The result showed that the load-carrying capacities of 1- and 0.5-mm diam stainless-steel-wire-reinforced PMMA specimens in bending were significantly higher than similar unreinforced normal PMMA samples. On an average, steel reinforcement comprising approximately 1% of the cross-sectional area of the PMMA specimens caused a 15% increase in bending strength. Even after the cement fractured, the reinforcing wires still sustained an appreciable amount of bending moment, thus preventing catastrophic failure of cement alone.

Bone Cements↗