Failure due to metallosis after cruciate retaining total knee replacement

Background: Rupture of PCL on cruciate retaining TKA can cause abnormal accelerated wear of polyethylene component which may result in metal/metal articulation and development of massive infiltration of metal debris in the periprosthetic soft tissue (metallosis). Patient and methods: Eight cases (Five females, 3 males, mean age 64.6 years) with failed primary cruciate retaining knee arthroplasty were retrospectively studied. Revisions were performed after a mean of 59.8 months due to pain and instability. All the patients had variable degrees of clinically relevant posterior knee instability. Infection was excluded in all cases through microbiological examination and synovial fluid analysis. Results: Abnormal direct metal-on-metal articulation between the femoral component and the tibial base plate with advanced polyethylene wear were found intraoperatively in all cases in addition to extensive tissues black staining, advanced osteolysis and pseudotumor formation. All cases were managed by single stage revision surgery with implant removal, profound synovectomy and revision using a more constrained modular revision knee system. Conclusion: Metallosis after total knee arthroplasty is a rare situation that should be suspected in total knee arthroplasty cases with radiologically evident advanced polyethylene wear especially in cruciate retaining knee systems. It could lead to significant osteolysis making revision surgery technically challenging.