Screw Track Osteolysis in the Cementless Total Knee Replacement Design.

Background: There is a paucity of reports on osteolysis associated with tibial screw fixation in cementless total knee arthroplasty (TKA), and the pathophysiology is not clear. This study aimed to describe the pathology related to screw track osteolysis around the tibia in cementless TKA.

Methods: The study cohort comprised 100 revised cementless TKAs with tibial screw fixation. Screw track osteolysis and various screw angles were analyzed radiologically. Tissue samples from the joint capsule and the osteolytic cavity were investigated for metal/polyethylene wear. The type of tissue response was determined using immunohistochemistry. Retrieved tibial polyethylene inserts were analyzed for screw hole impression and mode of wear. Tissue metal content was measured by inductively coupled plasma optical emission spectrometry. Electrochemical reactions between the tibial tray and the cancellous screws were investigated.

Results: Radiological analysis showed screw track osteolysis predominantly at the medial aspect of the tibial component, and the severity of osteolysis positively correlated with smaller medial proximal tibial screw angles. Osteolysis was associated with high titanium concentrations but not with polyethylene particles. An open circuit potential between the screw and the tibial base plate was measured. Necrosis, osteolytic cyst formation and macrophages, T and B cells, and dendritic cells were present.

Conclusion: The present study highlights the risk for screw track osteolysis in cementless TKA with screw fixation. Our data collectively suggest that titanium wear may contribute to screw track osteolysis in the cementless TKA design. The contribution of screw angles is difficult to prove.