Radiofrequency-generated glow discharge treatment: potential benefits for polyester ligaments

This multicenter study has revealed that treating a woven polyethylene terephthalate (polyester) ligament with a radiofrequency (RF)-generated glow discharge (RFGD) produces marked benefits in terms of increased cell attachment and proliferation on the implant surface. In vitro tests of the same material revealed that the number of synovial fibroblasts attached to the treated samples after 14 days was four times that of the untreated material. Many of the cells were spread over the surface of a single filament, and some formed bridges between one filament and the next. The incorporation of [(3)H]-thymidine by synovial stromal cells (a measure of the amount of cell division) growing on the treated material was five times that on the untreated samples. The amount of DNA present on the treated material was also found to be almost an order of magnitude greater than that on untreated samples. This increase in cell attachment and proliferation is almost certainly related to a notable increase in wettability of the polyester surface induced by treatment. Mechanical tests revealed that, for ligaments with a nominal ultimate tensile strength of 2100 N, RF-generated glow treatment reduced the ligament's strength by 12% but increased its stiffness by 15%. After a medium-term fatigue test (10.8 million cycles), however, there appeared to be recovery of the mechanical properties, with the strength and stiffness of untreated and treated samples being essentially the same. After exhaustive fatigue tests (more than 62 million cycles) the residual strength of the treated ligaments was only 9% lower than that of the unfatigued and untreated ligaments.