A study of the effect of pulsed electromagnetic waves on the blood flow of a normal limb.

THE mechanism of healing in a fractured long bone, despite its common occurrence, remains the subject of debate and investigation.' The factors which initiate, guide and control the various processes of bone repair are still illunderstood. The recent use of electrical stimulation of bone, particularly in nonunion and in pseudarthrosis of the tibia has gained popularity as a possible method of inducing osteogenesis. The first report of the use of electrical stimulation to enhance the healing of fractures was by Hartshone,2 but until fifteen years ago little was known of the effects of electricity on bone. Since then there has been an exponential rise in the number of publications3 and the literature on the subject is both bewildering and confused.4 It is still not clear what method of electrical stimulation is correct, what the current should be, where the anodes and cathodes should be placed, what pulsing of electro-magnetic fields is correct or indeed whether the technique has any significant effect on human bone at all. The association of piezoelectrical potentials and remodelling of bone according to Wolffs Law is altogether a different concept from its ability to induce osteogenesis in a non-union. The electrical potentials observed on stressing a bone do not depend on the viability of the tissue and the mechanism by which they reduce changes in bone is unclear. The effect on bone is generally held to be a piezoelectric effect,5 6'7 but others have postulated a pyro-electrical effect8 or an ion exchange mechanism.9 The mass of evidence, however uncontrolled and circumstantial, points to electricity as a possible signal which may redirect the response of a cell by changing its physical environment. The electrical signal may not be a direct stimulus but indirect, acting by some other physiological mechanism. The physiological mechanism may also be initiated by a number of other different signals. The effect of blood supply on fracture healing is accepted and it is possible that the physiological mechanism involves the blood supply. A fracture of the tibia in the dog produces a dramatic increase in total limb blood flow and specific receptors controlling flow changes are present in the soft tissues and periosteum surrounding the fractured bone.'0 Increased vascularity was confirmed in the human fractured