Tibial post wear in posterior-stabilized knee replacements is design-dependent

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Materials Science

Background:

• Polyethylene tibial post wear is a critical issue in posterior-stabilized knee replacements.
• The Insall-Burstein II (IB PS II) design is associated with severe anterior post wear in retrieved implants.

Purpose of the Study:

• To investigate the hypothesis that the anterior placement of the tibial post in the IB PS II design leads to greater anterior face wear compared to the Insall-Burstein I (IB PS I).

Main Methods:

• Analysis of 234 retrieved polyethylene tibial inserts from IB PS I and IB PS II knee replacement systems.
• Subjective grading scales were used to assess post damage and wear patterns.

Main Results:

• 38% of IB PS II inserts showed severe wear, versus 25% of IB PS I inserts.
• The primary wear location for IB PS II was the anterior face, while IB PS I experienced wear mainly on the medial face.
• Observed contact in hyperextension or paradoxical anterior tibial translation is common and design-dependent.

Conclusions:

• Tibial post placement significantly influences wear patterns in posterior-stabilized knee designs.
• Future designs should consider anterior post contact and placement to minimize wear and damage.
• Optimizing post placement and design requires consideration of tibial bearing surface interaction.