Electrocautery Alters the Near-Surface Microstructure, Phases, Composition, and Hardness of Ti-6Al-4V.

Abstract

Despite the high success rates of total joint arthroplasty procedures, including total knee and hip replacements, implant failures still occur. This study investigated a potential, yet underrecognized, cause of implant failure: unintentional damage from the contact of electrosurgical blades with metal implant alloys. To understand this phenomenon, electrocautery damage (ECD) was induced to Ti-6Al-4V discs to evaluate microstructural changes to the surface and subsurface using digital optical microscopy, scanning electron microscopy, energy-dispersive spectroscopy, and atomic force microscopy. We assessed local depth-dependent single-asperity hardness of the cross-sectioned samples through the ECD site. ECD caused permanent changes in the microstructure up to 300 μm beneath the surface, transforming the grain structure in a depth-dependent manner into a predominantly martensitic form and a concurrent modification of the β-phase morphology. Within the top 50 μm, surface melting and the formation of oxide and nitride phases was seen. Transferred silicon, carbon, and iron particles from the electrosurgical blade were detected in the melted and oxidized surface layer. Melt-resolidified particles and evidence of alloy mixing between the blade and substrate was documented. Surface cracking penetrating tens of microns into the surface was observed. Hardness measurements revealed a substantial increase in the ECD-affected zone, reaching up to 8.5 GPa at 130 μm depth, compared to a bulk hardness of 2.7 GPa (p = 0.001). These findings systematically characterize electrocautery-induced subsurface transformations in Ti-6Al-4V, highlighting a previously underrecognized mechanism of implant surface embrittlement that may have significant implications for long-term arthroplasty performance and surgical technique.