Morris H. Shamos

Electric Enhancement of Bone Healing

A human congenital pseudarthrosis of the tibia, unresponsive to conventional treatment, was stimulated to healing by direct electric current. The method was modeled after prior experimental work in vivo in rabbits. X-ray photographs, histological techniques, and electron microscopy confirmed the presence of newly formed bone in the defect region.

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.

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.

Piezoelectric Effect in Dentin

It was reported recently (J. M. MUMFORD and A. V. NEWTON, J Dent Res 48:226-229, 1969) that there is considerable transduction of mechanical force to electric potential in whole teeth. In the same paper, a tentative model for this phenomenon was presented, which involved the streaming potential in capillaries (the periprocessal space in dentinal tubules). An alternate explanation for this effect, namely, the piezoelectric response of dentin is possible. Piezoelectricity, long regarded as a classical phenomenon in physics (W. G. CADY, Piezoelectricity, 1964) has, in the last few years, been found in a variety of biologic materials (V. A. BAZHENOV, Piezoelectric Properties of Wood, 1961; M. H. SHAMOS, and L. S. LAVINE, Clin Orthop 35:177-188, 1964; E. FUKADA, Biorheology (Oxford) 5:199-208, 1968) and it must be recognized as a fundamental property of biologic tissues (M. H. SHAMOS and L. S. LAVINE, Nature 213:267-269, 1967.). This and other groups have previously reported (SHAMOS, LAVINE, 1964; M. BRADEN ET AL, Nature 212: 1565-1566, 1966; G. V. B. COCHRAN, R. J. PAWLUK, and C. A. L. BASSETT, Arch Oral Biol 12: 917-920, 1967) a decided piezoelectric effect in human dentin. However, these were qualitative results and were difficult to interpret because of the specimen size available from humans. A recent determination has been made on horse dentin cubes cut so the dentinal tubules were all approximately parallel. The expression governing the electric polarization, Ps (coulombs/m2), resulting from the application of stress, Sj (newtons/M2), is Pi= doSe, where the 18 elements (dil) are referred to as the piezoelectric moduli. The index j takes on the values 1 -e 6, corresponding to the six possible stresses on a cube, and the index i takes on the values 1, 2, 3, corresponding to the three Cartesian directions. Depending on the crystal system, most of the dij are zero. It is generally agreed that the greatest piezoresponse in collagenous systems

Light induced effects in bone.

SOME recent reports on photoelectric effects in human bone by Becker and co-workers have been interpreted as evidence that bone exhibits semiconducting properties, including photoconductivity1,2. The present investigation leads to the conclusion that the effect of light on bone is simply heating, which is often difficult to distinguish from photoconductivity. The reported photoelectric effects1,2 can probably be attributed to such an “artefact”.

USE OF OPTICAL FIBRES FOR DETERMINATION OF IRRADIANCE AT THE RETINAL PLANE

When attempting to draw correlations between the amount of thermal energy incident upon the retina and the degree of retinal damage, one of the problems that faces the investigator is the determination of the irradiance at the retinal plane. A commonly used technique for arriving at this factor is to utilize an neye simulator<< consisting of a quartz lens. This technique (1) of necessity assumes a fixed and constant focal length, emmetropia and spectral absorption characteristics for all experimental animal eyes. This method is not accurate to the degree required for definitive work. Because of the problems of these assumptions, we have devised a technique which allows us to measure the irradiance at the retinal plane of each eye used for the study. The basis of the measurement technique involves placing the receiving end of a fiber optic light guide at the retinal plane of an enucleated eye and allowing the energy delivered a t the far end of the guide to fall upon the face of a. silicon solar cell.