Treatment of congenital pseudarthrosis of the tibia with direct current.

Bone possesses a bioelectric property that is important in maintaining its structural and architectural integrity. In vivo experiments demonstrate that bone formation can be accelerated by the application of direct current. We hypothesize that bone formation occurs through an electrochemical rather than an electromechanical effect. Two cases of congenital pseudarthrosis of the tibia treated by direct current stimulation are presented. A bone graft may be added to enhance bony union in conjunction with direct current. The implications of this work are that there is need for further fundamental studies including ultrastructural observations.

On electrical condution in living bone.

Despite the effectiveness of electrical currents in enhancing bone repair, there is little information in the literature on electrical parameters per se. Very little is known about the nature of the conduction mechanism or the current path between the electrodes. Without a better understanding it is difficult to establish meaningful hypotheses at the cellular level and to design relevant experimental protocols. In the present work, a first attempt is made at an in vivo delineation of the current-voltage relationship in the medullary area between two platinum electrodes embedded in the femur, by one of the techniques generally known to stimulate bone growth. At potential differences of less than 1 volt, a rather good ohmic dependence is observed, with an approximate specific resistance of 2 to 5 times 10-5 ohms/cm. At potentials higher than 1 volt, electrolytic processes appear to predominate and there is increasing non-linearity. Experimental techniques involving the adjustment of current through bone tissue assuming an ohmic dependence with little or no associated polarization effects are valid and certainly warrant further investigation.

An investigation of the bound water in tendon by dielectric measurement.

The dielectric constant of natural tendon in the frequency range of 200 Hz to 100 kHz has been determined as a function of temperature (300-450 degrees K) for water concentrations ranging from about 6 to 16% by weight. The results compare well with the approach taken by Haggis and his coworkers. Based on the assumption that at low concentration of water the probability of water-water bonding is small and hence may be disregarded, a structure for water in the collagen matrix is proposed in which the water is either bonded in one of four possible states to the polar groups of the polypeptide chains, or is unbound. In determining the distribution of the water among these states an approach similar to that of Haggis and his co-workers, in conjunction with the order-disorder theory of Bragg and Williams, is used. The number of water molecules per unit volume is then determined experimentally by relating it to weight loss as a function of temperature, as determined by thermogravimetric analysis. The dispersion which is normally found in dipolar substances has not been found for tendon. A maximum in the value of the dielectric constant is observed to occur between 25 and 80 degrees C, the temperature depending upon the heating rate.