Nontraumatic Tibial Polyethylene Insert Cone Fracture in Rotating-Platform Total Knee Arthroplasty

Area of Science:

• Orthopedic Surgery
• Biomaterials Science
• Implant Failure Analysis

Background:

• Total knee arthroplasty (TKA) with rotating-platform (RP) designs is a common procedure.
• Polyethylene (PE) inserts are crucial components in TKA, designed for durability.
• Understanding failure modes is essential for improving long-term implant survival.

Observation:

• A 65-year-old female experienced knee pain and instability 10 years post-primary RP TKA.
• Revision surgery revealed a fractured polyethylene insert cone, 10 mm from the liner's inferior surface.
• This represents the first documented instance of cone fracture in this specific RP TKA implant model.

Findings:

• The observed fracture was attributed to fatigue failure of the polyethylene insert cone.
• This fatigue failure led to secondary loosening of the tibial tray component.
• The fracture mechanism suggests a potential vulnerability in the implant design or material under specific loads.

Implications:

• This case highlights a novel failure mode for rotating-platform total knee arthroplasty.
• Clinicians should consider PE insert cone fracture in patients presenting with pain and instability after RP TKA.
• Further investigation into fatigue resistance of polyethylene components in TKA is warranted.