Metal-backed and all-polyethylene tibial components in total knee replacement

Area of Science:

• Orthopedic Surgery
• Biomaterials Science
• Medical Device Engineering

Background:

• Press Fit Condylar (PFC) total knee replacement (TKR) is a common procedure.
• Metal backing and modularity were introduced to enhance fixation durability in TKR components.
• Long-term outcomes comparing different tibial component designs are crucial for clinical decision-making.

Purpose of the Study:

• To evaluate the clinical and radiographic outcomes of PFC TKR with modular metal-backed versus all-polyethylene tibial components.
• To assess the incidence of osteolysis, synovitis, and revision rates between the two tibial component designs.
• To determine the survival rates and wear characteristics of the tibial components.

Main Methods:

• Retrospective evaluation of 175 patients (243 knees) undergoing primary PFC TKR.
• Comparison of outcomes between 113 knees with modular metal-backed tibial components and 130 knees with all-polyethylene tibial components.
• Assessment of patient-reported scores, radiographic findings (osteolysis, synovitis), revision rates, and component survival at a mean of 5.5 years.

Main Results:

• No significant difference in mean knee and functional scores between the groups.
• Higher incidence of osteolysis (5%) and synovitis in the modular metal-backed tibia group compared to none in the all-polyethylene group.
• Five revisions (all in metal-backed group) for osteolytic defects or synovitis; backside wear noted on retrieved polyethylene inserts.

Conclusions:

• The all-polyethylene tibial components demonstrated a superior safety profile, with no osteolysis or synovitis observed.
• The incidence of revision surgery was significantly higher in the modular metal-backed tibia group.
• The long-term benefits of metal backing and modularity in the PFC TKR design are questionable given the observed adverse events and lower survival rates.