Correlation between condylar lift-off and femoral component alignment

Area of Science:

• Orthopedic Surgery
• Biomechanical Engineering
• Medical Imaging

Background:

• Total knee arthroplasty (TKA) is a common procedure to alleviate pain and restore function.
• Condylar lift-off, a phenomenon where the femoral component separates from the tibial plateau, can lead to implant wear and failure.
• Accurate femoral component alignment is crucial for TKA success.

Purpose of the Study:

• To determine the incidence of condylar lift-off in posterior stabilized TKA.
• To correlate condylar lift-off with femoral component alignment relative to the transepicondylar axis.
• To investigate methods for reducing condylar lift-off and associated polyethylene wear.

Main Methods:

• Twenty-five TKA subjects underwent weightbearing deep knee bends under fluoroscopic surveillance.
• 2D fluoroscopic images were converted to 3D models using automated computer fitting.
• Femoral component alignment was measured using digitization and correlated with condylar lift-off incidence, with CT used for high-lift-off cases.

Main Results:

• Forty percent (10 of 25) of subjects experienced condylar lift-off, with a maximum of 2.3 mm and an average of 1.4 mm.
• A significant correlation was found between femoral component malalignment and condylar lift-off (69.2% of subjects).
• Incidence of condylar lift-off was lower than reported in previous fluoroscopic studies.

Conclusions:

• Femoral component alignment parallel to the transepicondylar axis appears to reduce condylar lift-off.
• Minimizing condylar lift-off may decrease polyethylene wear by reducing eccentric edge loading.
• Optimizing femoral component placement is vital for long-term TKA implant survival and function.