Trunnion Failure in Revision Total Knee Arthroplasty

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Implant design

Background:

• Revision total knee arthroplasty (rTKA) necessitates preserving joint kinematics despite compromised bone and ligament integrity.
• Modular prosthetic designs offer intraoperative customization for bone defects using various stem extensions and constraints.
• Increased constraint enhances knee stability but elevates stress at the implant-host interface and modular junction.

Observation:

• Two cases of prosthetic stem-condyle junction failure were observed.
• Failures occurred in revision total knee arthroplasty utilizing varus-valgus constrained implants.
• The failures highlight a vulnerability in the prosthetic stem-condyle junction under specific constrained conditions.

Findings:

• The prosthetic stem-condyle junction is susceptible to fatigue failure when subjected to increased stress from constrained revision knee implants.
• Varus-valgus constrained implants, while stabilizing the knee, may inadvertently concentrate stress, leading to mechanical failure.
• This indicates a potential design limitation in current modular revision knee systems.

Implications:

• Consideration of junctional stress is critical in the design of constrained revision total knee arthroplasty components.
• Further research into optimizing implant geometry and material properties to mitigate fatigue failure at the stem-condyle junction is warranted.
• Clinical strategies may need to adapt to account for the risk of junctional failure in highly constrained revision TKA cases.