Tibial insert undersurface as a contributing source of polyethylene wear debris

Area of Science:

• Biomaterials Science
• Orthopedic Surgery
• Wear Analysis

Background:

• Ultrahigh molecular weight polyethylene (UHMWPE) tibial inserts are crucial components in cementless total knee arthroplasty (TKA).
• Osteolysis, or bone loss, is a significant cause of TKA failure, often attributed to polyethylene wear debris.
• The primary articulation surface has been considered the main source of this debris.

Purpose of the Study:

• To investigate the role of both articular and nonarticular surface wear of UHMWPE tibial inserts in TKA.
• To determine the correlation between insert wear patterns and the occurrence of tibial metaphyseal osteolysis.
• To identify potential strategies for reducing wear debris and subsequent osteolysis.

Main Methods:

• Retrieval analysis of 67 UHMWPE tibial inserts from cementless TKAs implanted for a mean of 62.8 months.
• Assessment of articular and nonarticular (undersurface) wear severity using a grading system (Grade 0-4).
• Radiographic evaluation for tibial metaphyseal osteolysis and osteolysis around fixation screws, analyzed using nonparametric conditional inference methods.

Main Results:

• Severe Grade 4 wear on the insert undersurface was significantly associated with tibial metaphyseal osteolysis and osteolysis around fixation screws.
• Implantation time correlated with severe undersurface wear and tibial metaphyseal osteolysis.
• Articular wear severity, insert thickness, and implant type were not statistically related to tibial osteolysis.

Conclusions:

• The undersurface of the UHMWPE tibial insert represents an additional source of polyethylene debris contributing to tibial osteolysis in TKA.
• Improving the fixation mechanism of the tibial insert to the metal backing is essential to minimize micromotion and debris generation.
• Optimizing the wear characteristics of the inner tray surface is necessary to reduce wear debris from this secondary articulation.