Severe metallosis-related osteolysis as a cause of failure after total knee replacement

Metallosis is a syndrome of metal-induced synovitis caused by friction between two metal surfaces. In contrast to the hip joint after resurfacing arthroplasty or metal-on-metal (MoM) total hip replacement, metallosis of the knee is extremely rare.

We describe 4 patients who underwent revision total knee replacement because of disabling pain and implant loosening after a mean time of 21 (range: 13-30) years of knee replacement surgery. They were all females with a mean age of 79 (range: 75-82) years. Septic loosening was excluded through microbiological examination and synovial fluid analysis.

Direct metal-on-metal contact at the tibiofemoral interface was confirmed intraoperatively in all cases. All knees showed severe metallosis with advanced osteolysis and pseudotumor formation. In one knee there was a complete fracture of the tibial tray. All patients had a one-stage revision surgery with implant removal, profound synovectomy and implantation of a constrained modular revision knee system. Long modular stems with offset adapters, wedges and/or blocks were used in all cases.

Metallosis-associated osteolysis should be suspected in cases with radiologically evident polyethylene wear after knee replacement. Recognizing that revision arthroplasty is very technically demanding in such cases, surgeons should have a back-up with modular revision components and a ready access to reconstructive options at this revision setting.