EARLY EFFECTS OF ELECTRICAL-STIMULATION ON OSTEOGENESIS

The mechanism by which electrical stimulation causes osteogenesis is u nknown. Bone marrow of the rabbit was stimulated by direct electrical current or electromagnetic fields to clarify the mechanism of osteogen esis by electrical stimulation, A total of 105 rabbits were separated into five groups: a direct current stimulation by Kirshner wire insert ion group; a pulsed electromagnetic fields stimulation (PEMF) group; a PEMF with Kirshner wire insertion group; a Kirshner wire insertion gr oup; and an intramedullary drilling control group, Measurement of intr amedullary new bone formation and determination of alkaline phosphatas e activity within the bone marrow were performed, Argylophilic nuclear organizer region (AgNOR) staining was done to evaluate the change in proliferative activity of the osteoblasts during electrical stimulatio n, In the direct current stimulation group and the PEMF accompanied by the insertion of the Kirshner wire group, alkaline phosphatase activi ty in the bone marrow and AgNOR staining increased at 7 days after sur gery, At 14 days after surgery, alkaline phosphatase activity and prol iferative activity of osteoblast were significantly higher in these tw o groups than in the other groups (PEMF group, Kirshner wire insertion alone group, intramedullary drilling group), Intramedullary new bone formation was most active in the direct current stimulation group, Ele ctromagnetic stimulation of the inserted Kirshner wire also promoted b one formation significantly, The Kirshner wire insertion alone group a nd the intramedullary drilling group showed bone formation, but it was significantly less, Electromagnetic stimulation without the insertion of the Kirshner wire showed little bone formation, These findings rev ealed that the degree of osteogenesis induced by electrical stimulatio n is influenced by the tissue environment, and that osteogenesis is pr omoted markedly when electrical stimulation is provided in the environ ment of inflammation and reactive cells.