[Ligament instability in total knee arthroplasty--causal analysis]

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Knee Biomechanics

Background:

• Ligament instability is a significant complication following total knee arthroplasty (TKA).
• Identifying the specific cause of instability is critical for successful revision procedures.
• Revision TKA aims to restore joint stability, function, and longevity.

Purpose of the Study:

• To analyze the various reasons for ligament instability in revision total knee arthroplasty (TKA).
• To correlate instability types with component positioning and other intraoperative findings.
• To provide insights for improving surgical techniques and patient outcomes in revision TKA.

Main Methods:

• Retrospective analysis of 135 revision TKA cases performed by a single surgeon.
• Preoperative clinical and radiographic assessment, including component positioning.
• Intraoperative evaluation of ligament stability (extension, 30°, 90° flexion), wear, patellar mechanics, and component alignment.

Main Results:

• Ligament instability was the primary reason for revision in 32.6% and a secondary reason in 21.6% of cases.
• Combined instability in extension and flexion was the most frequent type (31.8%), followed by isolated flexion instability (31.8%).
• A strong correlation was observed between instability and component malpositioning, particularly femoral rotation and tibial component placement.

Conclusions:

• Ligament instability is a common indication for revision TKA, presenting in various isolated and combined forms.
• Accurate anatomical component positioning and balanced soft tissues are essential for stable TKA revisions.
• Addressing ligamentous balance and precise component alignment is key to achieving favorable long-term clinical results and joint longevity.