Electrode Encapsulation

The tight-cell layer is compromised when particulate matter is present on lead, effect of cleaning


In the early 1990’s Narendra Bhadra carried out experiments involving several types of intramuscular electrodes. One set involved electrodes that were commercially packaged and labeled as, ready for human use. Histological examination of the implantation sites, of this electrode, reveled a larger than expected inflammatory response, shown here in a H&E section. This response was not unlike those seen with leads having particulate matter on the surface of the implanted lead. SEM examination of a lead, of an electrode that was withdrawn from the hypodermic needle for examination, revealed particles adhering the to the surface of the Teflon insulation. Several of the commercially packaged electrode were unpackaged, disassembled and inspected. It was determined that the bore of the hypodermic needles, used for electrode implantation, was the likely source of contaminate. The implant needles were thoroughly cleaned, the electrode was subjected to the cleaning procedure previously mentioned, repackaged under clean air conditions, and the implantation experiments repeated. An SEM of the cleaned lead showed no evidence of particulate matter on the lead surface and the muscle implant site was microscopically examined to reveal a much milder inflammatory response, like that observed for other intramuscular electrodes studied in that set of experiments. These results underscore the importance of implanting sterilized devices that are free of particulate matter. Sources of contaminates must be considered at the time of implantation. Such source can be talc on surgical gloves and fiber from drapes used to cover the sterile field.