Polyethylene thickness is a risk factor for wear necessitating insert exchange.

Area of Science:

• Orthopedic surgery
• Biomaterials science
• Wear analysis

Background:

• Polyethylene (PE) wear is a leading cause of revision in total knee arthroplasty (TKA).
• Understanding the relationship between PE thickness and implant survival is crucial for optimizing TKA outcomes.
• Identifying risk factors for PE insert wear can guide surgical decision-making and implant selection.

Purpose of the Study:

• To determine the optimal minimal polyethylene (PE) thickness for total knee arthroplasty (TKA) inserts.
• To identify risk factors associated with revision due to PE insert wear.
• To provide evidence-based recommendations for PE insert thickness in TKA.

Main Methods:

• Observational study of 84 TKAs over 11-16 years.
• All patients received the same prosthesis design with separate medial and lateral PE half-bearings.
• Cox-regression analysis was used to identify risk factors and adjust for confounding variables.

Main Results:

• Eight knees (9.5%) required revision due to PE insert thinning; one additional patient is scheduled for revision.
• Reduced PE thickness, osteoarthritis (OA) diagnosis, higher BMI, and increased weight were significant risk factors for insert exchange.
• A 1-mm decrease in PE thickness increased the risk of insert exchange by 3.0 times.
• OA patients had a 4.73 times higher likelihood of insert exchange compared to RA patients.
• Each unit increase in BMI and weight increased the risk of insert exchange by 1.40 and 1.14 times, respectively.

Conclusions:

• Thin PE inserts in modular TKA are associated with a significantly higher risk of revision due to wear.
• A minimum PE insert thickness of 8 mm is recommended for TKA to enhance implant durability and reduce revision rates.
• Optimizing PE thickness and considering patient-specific factors like BMI and diagnosis are essential for long-term TKA success.