Causes of instability after total knee arthroplasty

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering

Background:

• Total knee arthroplasty (TKA) is a common procedure for end-stage knee osteoarthritis.
• Instability is a significant cause of TKA revision surgery, impacting patient outcomes.
• Understanding the etiologies of TKA instability is critical for improving revision strategies.

Purpose of the Study:

• To characterize the diverse underlying causes of instability following total knee arthroplasty (TKA).
• To categorize the specific reasons leading to revision TKA due to instability.
• To inform tailored surgical approaches for revision TKA based on identified instability causes.

Main Methods:

• Retrospective review of 83 revision TKAs performed in 79 patients for instability.
• Detailed analysis of patient history, physical examination findings, operative reports, and radiographic imaging.
• Classification of instability causes into six distinct categories: flexion/extension gap mismatch, component malposition, ligament insufficiency, extensor mechanism insufficiency, component loosening, and global instability.

Main Results:

• Six primary categories of TKA instability were identified.
• Flexion/extension gap mismatch was the most frequent cause (24 knees).
• Twenty-five knees presented with multi-factorial instability, highlighting complex etiologies.

Conclusions:

• TKA instability arises from a spectrum of distinct causes that require precise identification.
• Revision TKA procedures should be specifically tailored to address the fundamental etiology of instability.
• Accurate diagnosis of instability causes is paramount for successful revision total knee arthroplasty outcomes.