Treatment Depth Effects of Combined Magnetic Field Technology using a Commercial Bone Growth Stimulator

Lumbar spinal fusion is one of the more common spinal surgeries, and its use is on the rise. If the bone fails to fuse properly, then a pseudarthrosis or “false joint” develops and results in pain, instability, and disability. Since1974, three types of electrical stimulation technologies have been approved for clinical use to enhance spinal fusions. One such technology is inductive coupling, which includes combined magnetic fields (CMFs). The purpose of this study was to evaluate the effects of a CMF device known as the Donjoy (SpinaLogic®) on MG-63 (ATCC® CRL1427TM) human osteosarcoma cells at treatment depths ranging from 0.5” to 6.0”. The cells were grown to confluence on 4-well chamber slides that were kept in a nickel-alloy chamber within an incubator to shield the cells from unwanted environmental electromagnetic fields. During treatment, a specially designed apparatus held both the treatment device and the chamber slide. Briefly, the chamber slide was placed inside an acrylic tube at a specific distance from the transducer housing, and the device was turned on for 30 minutes. The chamber slides were then returned to the incubator to be evaluated at 7, 14, and 21 days post treatment for cell viability and bone nodule formation. Our results showed that compared to control cells, the cells located at 3” from the source had the greatest increase in bone nodule formation 7 days post treatment which is the depth at this consistent with manufacturer recommendations.