Backside wear in modern total knee designs.

Area of Science:

• Orthopedic surgery
• Biomaterials science
• Wear mechanics

Background:

• Total knee arthroplasty (TKA) implants utilize modularity, but unintended contact between the tibial insert and metallic tray can cause micromotion.
• This micromotion generates polyethylene wear debris, potentially impacting implant performance and longevity.

Purpose of the Study:

• To investigate and compare the backside wear of tibial inserts from three distinct modern total knee designs.
• To evaluate the influence of different locking mechanisms on polyethylene wear patterns.

Main Methods:

• Analysis of 71 retrieved tibial inserts from Insall-Burstein II (IB II), Optetrak, and Advance total knee systems.
• Assessment of wear extent, depth, and damage modes (abrasion, burnishing, scratching, etc.) using a standardized scoring system (0-3).
• Correlation of wear findings with patient data including age, BMI, and implantation duration.

Main Results:

• Both Advance and IB II polyethylene inserts exhibited significantly higher backside wear scores compared to Optetrak inserts.
• All IB II and Advance implants displayed evidence of backside wear, whereas only 83% of Optetrak implants showed wear.
• No significant differences in wear depth were observed between the implant designs.

Conclusions:

• The locking mechanism of a total knee arthroplasty implant significantly influences the propensity for backside polyethylene wear.
• Implant design, specifically the locking mechanism, is a critical factor to consider in minimizing wear debris and optimizing implant survival.