Dielectric permittivity and conductivity of bone in different physiological conditions and collagen, a major component of bone are measured in the frequency range 400-1300 MHz using a Network analyzer. The dielectric dispersion observed in each cases are explained in terms of the relaxation of 'bound water' in this frequency range. The relaxation frequency as well as distribution parameter are computed in each case, under certain simplifying conditions, hydration as well as static dielectric permittivity of bound water attached with bone in different physiological conditions and collagen are also calculated. The effect of ultraviolet light irradiation on the dielectric properties of bone in this frequency range is also examined. The change in dielectric properties due to radiation is attributed to the breakage of hydrogen bonds in the ring structure. A consistent physical model in line with other data is presented.
The purpose of this study is to determine if the volume conduction of electrical current by blood can extend or possibly prevent clotting, and if so to determine where in the clotting sequence the effects occur. The important aspects of these based as follows: All cells and surfaces of the body carry an electrical charge. The magnitude of this surface charge is determined not only by the characteristics of the cells and particles themselves, but also by the liquid or solid in which they are immersed. The majority of the particles within the blood are negatively charged. Although the intima of the vascular system is negatively charged with respect to the adventitia of the vessel, trauma to the vessel will cause the negative charge to become zero or positive with a concomitant thrombosis at that point. An incision into a vessel will result in a positive voltage at the injury site. If the incision is kept negatively charged through application of an electrical current, coagulation at the site will be inhibited and the wound will ooze for many hours. If the current is reversed and made positive, clotting will accelerate. In the laboratory when two oppositely charged electrodes were cemmersed in a beaker of blood, a clot formed at the positive electrode only. If the procedure is carried out correctly, the blood surrounding the negative electrode will have highly effective anticoagulant properties. Furthermore, under similar conditions, leucocytes will migrate toward the negative electrode, thus indicating a change in cell polarity from negative to positive, possibly as a means to combat inflammation. A special bridge circuit and several original test cell designs were developed. Some of the results of this research are as follows: a means to electronically detect coagulation was devised; clotting was extended in excess of 400% by the application of electrical currents; currents below one milliamp per cm2 would not cause any noticeable trauma to the blood as determined by routine clinical laboratory methods. Analysis of the saline compartments resulted in the conclusion that there had not been any migration of the blood components into the saline. However, since the pore size would prohibit the migration of the blood components into the saline.(ABSTRACT TRUNCATED AT 400 WORDS)
The performance of particulate aluminum oxide (Al2O3) as a bone graft material was evaluated by comparison to two other graft materials, autogenous bone and particulate hydroxylapatite (HA). Holes were drilled through the medial cortex of both the distal femora and proximal tibiae in three dogs. The Al2O3, HA and autogenous bone were packed into the created defects and the rate and extent of defect healing examined. Particulate Al2O3 and HA were also placed on opposite sides of the median sacral crest in a spinal fusion procedure. One dog was sacrificed at 4, 8 and 12 weeks post-operative. The extent and rate of healing was superior with the autogenous bone, while the performance of the HA was superior to that of the Al2O3 at 4 and 8 weeks. However by 12 weeks, the performance of the two non-autogenous materials was equivalent. At 12 weeks the majority of the cancellous defect was infiltrated with viable bone with all three materials. In the spinal fusions, results were not as encouraging, with less bone present within the graft materials as compared to the cancellous defect implantations.
This study has revealed several factors which influence the accuracy and interpretation of electrochemical test results with surgical implant materials. These include variation between corrosion rate determination methods, IR drop, diffusional effects, and inherent statistical variations. The AC impedance method (ACI) is particularly useful for studying electrochemical mechanisms, measuring IR drop, and separating stress-enhanced ion release effects into components related to current density and surface area changes. This method can also measure true surface area even of irregular objects and can detect changes in area caused by cracking or surface plastic deformation. The corrosion rate method which is most accurate, in an absolute sense, must be determined by chemical analysis of the electrolyte.
C5a, released during activation of the complement cascade, was measured by radioimmunoassay in human plasma incubated with Dacron, preclotted Dacron, glutaraldehyde treated human umbilical vein (HUV), polytetrafluoroethylene (PTFE), and Dacron-collagen composite vascular grafts. Expressed as percent of C5a in control plasma incubated without graft, C5a generation by preclotted Dacron, and by the HUV was similar to that by Dacron (941 +/- 206% S.E.M.), while that due to PTFE was markedly less (p = 0.005). The Dacron-collagen composite vascular graft also generated significantly less C5a than Dacron and was similar to PTFE in this respect. These results expand on previous work suggesting that lower C5a generation by PTFE explained the negligible polymorphonuclear infiltrate seen on its surface in vivo, allowing it to endothelialise as rapidly as Dacron despite poorer attachment of seeded endothelial cells. The role of complement as a factor limiting endothelialisation of synthetic vascular prostheses needs further investigation.
A technique for making individualized silicone rubber intravaginal balloons is described. The method entails investing alginate vaginal impressions in silicone rubber and casting a resin model which is then dipped repeatedly in a Silastic Dispersion (Dow Corning, Q7-2213). The range of forces developed by circumvaginal muscles during maximum contractions was determined to be 0.5-4 lbs. Pressure-volume relationships of the balloons showed that the pressure of filling fluid was an accurate replica of the mean pressure in the vagina.
This study was designed to examine the effect of inflammatory reaction elicited by percutaneous tube on bone induction. Inflammation was provoked by different types of biomaterials. In order to evaluate incorporation of percutaneous tubes, bone matrix and subcutaneous tissue, demineralizing bone matrix was implanted in the subcutaneous tissue of rats and was exposed to interaction with inflammatory conditions. Inhibition to the induction of cartilage and bone by the inflammatory process could be clearly demonstrated. It is suggested that the low pH levels, typical to enzymes operative in inflammation are a direct cause for inhibition of chondro and osteogenesis. The process of calcification is characterized by the activation of enzymes in high pH levels.
In this study the electrical and dielectric properties of wet human cancellous bone from distal tibiae were examined as a function of frequency and direction. The resistance and capacitance of the cancellous bone specimens were measured at near 100% relative humidity. The measurements were made in all three orthogonal directions at discrete frequencies ranging from 120 Hz to 10 MHz using an LCR meter. At a frequency of 100 kHz, the mean resistivity and specific capacitance for the thirty cancellous bone specimens were 500 ohm-cm and 8.64 pF/cm in the longitudinal direction, 613 ohm-cm and 15.25 pF/cm in the anterior-posterior direction, and 609 ohm-cm and 14.64 pF/cm in the lateral-medial direction. All electrical and dielectric properties except the resistivity and the impedance were highly frequency dependent for the frequency range tested. All electrical and dielectric properties were transversely isotropic as the values for the longitudinal direction were different from values obtained for the two transverse directions and properties in the two transverse directions were approximately similar.
