Purdue News
Purdue News
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July 21, 1993 Electrical stimulation helps dogs with spinal injuriesWEST LAFAYETTE, IND. – A Purdue University study of dogs with spinal injuries shows that implanting an electrical device near the injury may promote nerve growth and help restore some bodily functions, including walking. Eighty-five percent of the dogs receiving an active device showed improvement compared to 45 percent of a control group of dogs that received a sham, the researchers say. "The most improved dogs got an active implant within two weeks of the injury," says Professor Richard B. Borgens. "From cell biology studies, we know that nerves are directed and guided by electrical fields. We also know that nerve degeneration is partially inhibited by appropriately placed fields. "These initial results are exciting and may help people with spinal injuries." Borgens is director of the Center for Paralysis Research and professor of developmental anatomy in Purdue's School of Veterinary Medicine, and since 1974 he has been studying how electrical fields stimulate limb regeneration and nerve growth in animals. He led the team that will report its results in the Aug. 24 issue of the journal Restorative Neurology and Neuroscience. The electrical device is called an oscillating field stimulator. DePuy (de-PYOU), an international manufacturer of orthopedic implants and equipment based in Warsaw. Ind., licensed the patent on the technology and is building a prototype for human use. A version of this new device will be tested first in dogs with naturally occurring spinal injuries before human use is considered. The new dog trials began this month at Purdue. "We are very excited about the prospects of this technology," says Dr. Stephen Peoples, vice president of clinical and regulatory affairs at DePuy, who also is a veterinarian and adjunct professor in Purdue's School of Veterinary Medicine. "While the results of the initial dog study are very promising, many variables are present in spinal injuries. Human clinical trials will be considered only after the safety and effectiveness of the technology are clearly established in further study in dogs." Peoples notes that the period of time from injury to surgery varied from dog to dog. "Because the length of time from injury to surgical decompression of the damaged spinal cord is known to be a very important determinant in the outcome of these injuries," People says, "the next dog study will be designed to consider this factor." The initial Purdue study involved 24 dogs with severe disc herniations, leading to spinal-cord compression and paralysis. After receiving surgery to reduce swelling and pressure from the injury, each dog was implanted with either an active or a sham version of the stimulator, which is about the size of a tube of lipstick. The battery-operated device passed a weak electrical current across the damaged nerves to stimulate their growth. The direction of the current flow was reversed periodically to cause growth from each side of the injury. The applied voltage produced by the device is about 1/250,000 of a volt, much less than the voltage that can cause muscle contractions. Thirteen of the dogs received an active unit, and 11 received a sham. Neither the Purdue researchers nor the dogs' owners knew which type of unit was put in any particular dog because the treatment assignments were coded. The dogs, whose owners voluntarily entered their animals in the study, were checked at the end of six weeks and again at six months, and then the code was revealed. At six months, 85 percent of the dogs with active units showed improvement in one or more of four neurological tests, compared to 45 percent of the dogs with sham stimulators. Almost one-third of the dogs with active units improved in all four categories, but none with the sham units did. The dogs were tested to determine if they felt superficial and deeper pain when their paws were squeezed and if they were able to place paralyzed paws unassisted in a natural weight-bearing stance. Their ability to walk and responses to electrical diagnostic tests also were measured. Within six months after the implantation, three of the dogs with inactive units recovered some walking ability although it was very uncoordinated and unbalanced, Borgens says, while seven of the active-implant dogs walked. Of the seven, two dogs walked almost as well as a normal dog and two more scored higher on walking ability than did the best of the sham-implanted dogs that walked. The researchers say they are especially encouraged that the effects seem to be permanent. "Dogs that got one or more functions back–including walking–have kept it," Borgens says. More recent work on dogs with older injuries–more than a month old–was not as successful, however. "There were only modest changes in the chronically injured dogs, even with an active unit," Borgens says. "And many reports were anecdotal, provided by the owners. It's fair to say electrical stimulation doesn't appear to be as effective on chronic injuries and will require more research." Borgens and Andrew Blight directed the first trials of the oscillating field stimulator in dogs. Blight, a former professor of anatomy at Purdue, is now a professor at the University of North Carolina, Chapel Hill; Dr. James P. Toombs, professor of small animal surgery in Purdue's School of Veterinary Medicine, is clinical director of the Center for Paralysis Research and oversaw clinical management aspects of the research, together with Drs. Michael Bauer, James Cook, Michael McGinnis and William Widmer. Bauer is associate professor of small animal surgery at Colorado State University; Cook is a neurology and internal medicine specialist with the Animal Emergency and Referral Center, Fort Pierce, Fla.; McGinnis is assistant professor of biology at Spelman College, Atlanta; and Widmer is associate professor of diagnostic imaging in Purdue's School of Veterinary Medicine. The Center for Paralysis Research is supported by funds from the Canadian Spinal Research Organization, the U.S. Department of Defense, the Center for Injury Control of the Public Health Service, and DePuy Inc. DePuy is part of Boehringer Mannheim, an international pharmaceutical, diagnostic-equipment and medical-device company. NOTE: B roll and graphics available, including a variety in color and black-and-white. Contact Purdue News Service (765) 494-2096 or purduenews@purdue.edu
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