Wear, Material Transfer, and Electrocautery Damage Are Ubiquitous on CoCrMo Femoral Knee Retrievals

Abstract

Despite high total knee arthroplasty (TKA) survivorship after 10 years (92%–99%), a gap persists where patient satisfaction lags clinical success. Additionally, while cobalt chrome molybdenum (CoCrMo) use decreases in primary total hip arthroplasty, the alloy continues to be widely used in TKA femoral components. In vivo, CoCrMo degradation may be associated with adverse local tissue reactions (ALTR) and compared with the hip, the damage mechanisms that may release metal in the knee and the potential biological effects remain poorly understood. In this study, we characterized the damage on 50 retrieved CoCrMo femoral knee implants paired with 19 titanium alloy and 31 CoCrMo tibial baseplates. We asked (1) what damage modes can release CoCrMo debris in vivo from femoral components and (2) how frequently does the damage occur? First, we developed a semiquantitative scoring system for abrasive wear. Then, we characterized damage modes on CoCrMo femoral implants using digital optical microscopy (DOM), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). We found that wear, electrocautery damage, and Ti-6Al-4V material transfer were ubiquitous. Of the 50 CoCrMo femoral implants we investigated, we documented wear on 100% (n = 50/50), electrocautery damage on 98% (n = 49/50), and Ti-6Al-4V material transfer to the posterior condyles on 95% (n = 18/19). Our results suggest that these damage modes may be more prevalent than previously thought and may act as metal release mechanisms in vivo.