Balance and constraint in revision TKR: A classification for instability management

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Reconstructive Surgery

Background:

• Instability is a frequent cause of Total Knee Arthroplasty (TKA) failure.
• Patients prioritize 'Functional Stability,' encompassing joint balance and mechanical support.
• Understanding TKA instability is crucial for successful revision procedures.

Purpose of the Study:

• To classify TKA instability types and their underlying causes.
• To develop a systematic approach for managing TKA instability.
• To provide recommendations for achieving functional stability in revision TKA.

Main Methods:

• Classification of TKA instability into three distinct types based on bone and ligamentous deficiency.
• Outlining the causes of instability for each TKA type.
• Developing an algorithm for joint line restoration and constraint management.

Main Results:

• Type 1: Bone deficiency requires joint line restoration for a balanced joint, with no increased constraint needed.
• Type 2: Ligament and soft tissue deficiency necessitates increased constraint to manage instability.
• Type 3: Composite (combined) deficiency involves both bone and soft tissue issues, requiring tailored management.

Conclusions:

• A clear classification system for TKA instability aids in targeted management.
• Restoring the joint line and applying appropriate constraint are key to achieving functional stability.
• Methodical recommendations based on instability type improve outcomes in revision TKA.