Posteromedial tibial polyethylene failure in total knee replacements

Area of Science:

• Orthopedic Surgery
• Biomaterials Science
• Medical Device Engineering

Background:

• Total knee arthroplasty (TKA) is a common procedure for end-stage knee arthritis.
• Polyethylene wear is a known mode of failure in TKA, potentially leading to revision surgery.
• Specific wear patterns, like focal posteromedial tibial polyethylene wear, require detailed investigation.

Purpose of the Study:

• To analyze 16 cases of focal posteromedial tibial polyethylene wear and failure after TKA.
• To identify the association between this wear pattern and tibial component subluxation.
• To investigate potential contributing factors and commonalities among failed TKA components.

Main Methods:

• Retrospective case review of 16 patients experiencing focal posteromedial tibial polyethylene wear and failure.
• Analysis of failed components across different TKA designs (Miller Galante 1, Porous Coated Anatomic, Kinematic, Press-Fit Condylar).
• Examination of implant characteristics including metal type, fixation, polyethylene manufacturing, and thickness.

Main Results:

• Focal posteromedial tibial polyethylene wear was consistently associated with external rotatory subluxation of the tibial component.
• Failure occurred at a mean of 45 months post-implantation across various TKA designs.
• No clear relationship was found with metal type, fixation, polyethylene manufacturing, or thickness.
• A common feature among failed components was a relatively flat tibial articular surface design.

Conclusions:

• A flat tibial component design may predispose to excessive translation, leading to polyethylene deformity, wear, and subluxation.
• This specific failure mode appears linked to the geometry of the tibial articular surface.
• Preventative strategies targeting component design and stability are suggested to mitigate this TKA failure mode.