Systemic Cobalt Toxicity Secondary to Tibial Component Malpositioning in Bilateral Primary Total Knee Arthroplasties

Metallosis and systemic metal toxicity are uncommon complications in modern total joint arthroplasty, typically linked to metal-on-metal hip articulations. We present a case of systemic cobalt toxicity following bilateral total knee arthroplasties (TKAs), where excessive posterior tibial slope caused flexion gap instability and polyethylene wear with subsequent metallic debris release. This patient developed cognitive impairment, neuropathy, and cardiac symptoms nearly a decade after surgery, with the highest serum cobalt and chromium levels reported in literature for primary TKAs. At revision, polyethylene and baseplate wear with metallic debris and bone loss were present. Surgeons should remain vigilant for metallosis and systemic toxicity in painful or unstable TKAs with polyethylene wear from component malalignment or instability. Further studies are needed to define surveillance strategies and management guidelines.