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Mass gain behaviour of tibial polyethylene inserts during soak testing
J M Brandt1, K D j Charron, S J MacDonald
1Concordia Joint Replacement Group, Concordia Hip & Knee Institute, Suite 310-1155 Concordia Ave, Winnipeg, Canada. jbrandt@cjrg.ca
Summary
Investigating fluid adsorption in total knee replacement tibial inserts revealed that handling and protein-rich fluids increase mass gain. Proper conditioning of polyethylene (PE) inserts is crucial for accurate wear rate determination.
Area of Science:
- Biomaterials Science
- Orthopedic Engineering
- Polymer Science
Background:
- Polyethylene (PE) tibial inserts are critical components in total knee replacements.
- Understanding fluid adsorption and mass gain in PE is essential for predicting implant longevity and wear.
- Previous studies have not fully elucidated the factors influencing PE mass gain during simulated implantation conditions.
Purpose of the Study:
- To investigate the fluid adsorption and mass gain behavior of polyethylene (PE) tibial inserts used in total knee replacements.
- To identify key factors affecting mass gain, such as handling, sterilization method, temperature, and fluid composition.
- To provide recommendations for optimizing conditioning protocols for PE inserts prior to wear testing.
Main Methods:
- Polyethylene (PE) inserts manufactured from extruded GUR 1050 resin were used.
- Inserts were soaked in various fluids (protein-rich and distilled water) at different temperatures (room temperature and 37°C).
- Gravimetric assessment was performed, involving repeated removal, cleaning, desiccation, and weighing of the inserts.
Main Results:
- Repeated handling during gravimetric assessment significantly increased PE mass gain.
- Higher mass gain was observed in inserts soaked at 37°C compared to room temperature.
- Gas-plasma sterilized inserts showed less mass gain than gamma-in-air sterilized inserts.
- Protein-rich fluids resulted in greater mass gain than low-ion distilled water.
- No significant difference in mass gain was found between 10mm and 14mm thick PE inserts.
Conclusions:
- Conditioning protocols significantly influence the mass gain of polyethylene tibial inserts.
- Accurate and precise determination of PE wear rate requires consistent conditioning under identical conditions (fluid type, temperature, handling frequency).
- Standardized pre-conditioning is recommended for tibial inserts before knee simulator wear testing to enhance data reliability.
