Mechanical Failure of Modular Rotating Hinge Femoral Component

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Implant failure analysis

Background:

• Hinged constructs are utilized in revision total knee arthroplasty for severe instability, ligament deficiency, or bone defects.
• These implants aim to restore stable knee motion for ambulation, but success varies with surgical complexity and bone quality.
• Common re-revision causes include patellofemoral issues, aseptic loosening, and infection, with mechanical hinge failure being a significant concern.

Observation:

• This report details the first documented case of catastrophic femoral component failure in a modular rotating hinge.
• The failure occurred due to a low-energy mechanism, suggesting a potential vulnerability in the construct design.
• Mechanical failure in hinged constructs most frequently involves the hinge component itself.

Findings:

• Catastrophic failure of the femoral component in a modular rotating hinge was observed.
• The failure mechanism was attributed to a low-energy event, contrasting with typical high-impact failures.
• This represents a novel failure mode for this type of constrained implant.

Implications:

• This case underscores the need for careful consideration of implant material and design in modular rotating hinges.
• Further investigation into the biomechanics and failure modes of these constructs under various conditions is warranted.
• Understanding rare failure mechanisms is crucial for improving the longevity and safety of revision total knee arthroplasty implants.