Amputation takes away more than muscle power. The loss of nerve fibers in amputated tissue means that all sensations from the missing flesh vanish as well, and that haywire signals from neuromas and the severed nerve ends can cause phantom sensations and intense pain. However, two sets of researchers have reported on work with a new polymer that might not only significantly reduce neurological complications from amputations, but may also bring far more sensation to prosthesis wearers.
Two sets of researchers presenting at the American Society of Plastic Surgeons Plastic Surgery 2009 conference, held October 23-27 in Seattle, Washington, gave lectures on the discovery and use of 3, 4-ethylenedioxythiophene (PEDOT), a biocompatible polymer that both conducts electricity and promotes stimulation and growth of nerve fibers.
In one study, surgeons at the University of Michigan (U-M), Ann Arbor, placed what they termed an “artificial neuromuscular junction”-a scaffold of the polymer that contained muscles cells-over the severed leg nerve of a rat. Inside the tube, new nerve fibers grew and developed stable connections with muscle fibers. The rodents’ feet, which had been innervated by the cut nerve, began responding to tickling sensations.
“The polymer has the ability to pick up signals coming out of the nerve, and the nerve does not grow an abnormal mass of nerve fibers,” said Paul S. Cederna, MD, a plastic and reconstructive surgeon at University of Michigan Health System and associate professor of surgery at the university’s medical school.
In a second study, plastic surgeons wrapped PEDOT around the severed leg nerve of a rat and then fit a cup containing muscle tissue around the nerve and polymer. According to ScienceDAILY, the PEDOT provided electrical charge to the nerves and muscles. After 114 days, new nerve fibers, muscle tissue, and blood vessels had grown and were compensating for the severed nerve, providing sensation to the injured limb.
Cederna told ScienceDAILY that he believes this research could lead to far finer control of prosthetic limbs than is currently possible and that the polymer could allow wearers to experience heat, cold, and other sensations through a prosthesis.
According to U-M, the U.S. Department of Defense and the Army have already provided $4.5 million in grants to support this research. Meanwhile, the research team has submitted a proposal to the Defense Advance Research Project Agency (DARPA) to begin testing the bioengineered interface in humans by 2013.
