The effect of postoperative electromagnetic pulsing on canine posterior spinal fusions

An experimental canine study was devised to evaluate the efficacy of a noninvasive adjunct to improve the rate and quality of the posterior fusion mass over the standard surgical technique. Ten large adult mongrel dogs underwent a three-level lumbar spinal fusion. Bone excised from the spinous processes was packed in removed facet joints and over the decorticated laminae. To insure rigid internal fixation, custom-made distraction instrumentation was placed bilaterally under the laminae of the vertebrae above and below the three fused vertebrae. Five dogs underwent electromagnetic pulsing, and five dogs acted as controls. Two dogs were sacrificed at 4, 6, 9, 12, and 15 weeks to assess the radiographic and histologic status of the fusion mass. Preoperative and preautopsy hematologic studies as well as gross and histologic autopsy specimens revealed no abnormalities attributable to the electromagnetic pulsing. High-resolution radiography and histologic studies showed earlier incorporation of the graft, improved new bone formation, and better organization of the fusion mass in the 4-, 6-, and 9-week stimulated specimens. However, by 12 and 15 weeks there did not appear to be any histologic or radiographic differences between the stimulated and control dogs. Although electromagnetic pulsing appears to produce an early accelerated osteogenic response, it does not appear to improve the overall results of primary canine spinal fusions.