Electrosurgery Induced Damage to Ti-6Al-4V and CoCrMo Alloy Surfaces in Orthopedic Implants In Vivo and In Vitro.

BACKGROUND: Recent observations of specific metal damage patterns on retrieved total joint implants implied a cellular origin and was termed inflammatory cell-induced (ICI) corrosion. Although ICI corrosion continues to present a potential damage source for metallic biomaterials surfaces, an alternate source of some damage patterns may arise from electrosurgery instruments in total joint arthroplasty.

METHODS: To characterize electrosurgically-induced damage patterns on metal implants, a model system of highly polished CoCrMo and Ti-6Al-4V disks and commercial electrosurgical generator was evaluated in various modes and power settings using monopolar and bipolar configurations. Surfaces were tested dry, wet with phosphate-buffered saline, or covered with known thicknesses of hydrated 5% agarose hydrogel.

RESULTS: In all cases, surface damage was generated on both alloy surfaces, directly resulting from plasma discharge interacting with the metal. Direct surface contact caused pitting and oxide buildup at the contact area. Damage was produced through 3 mm thickness of hydrogel on the surface and across metal-metal junctions representing modular tapers. Damage patterns on wetted surfaces were highly consistent with damage patterns observed on retrieved total joint implants; circular, ruffled areas with centralized pits, occasionally presenting trail- and weld-like features.

CONCLUSION: Surgeons using electrosurgical systems in proximity to metallic implants should exercise caution. Discharge of electrical energy through implants can induce localized surface damage and may result in other adverse outcomes. Although these results show some damage reported to be ICI corrosion is indeed the result of electrosurgery, there remains damage observed in retrievals not explained by this process.