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The Coventry Award. Modular tibial insert micromotion. A concern with contemporary knee implants
N L Parks1, G A Engh, L D Topoleski
1Anderson Orthopaedic Research Institute, Alexandria, VA 22307, USA.
Clinical Orthopaedics and Related Research
|January 26, 1999
Summary
Micromotion at the interface of modular total knee implants causes polyethylene insert wear. Even under low loads, hundreds of microns of motion were observed, indicating a need for improved locking mechanisms in these medical devices.
Area of Science:
- Biomedical Engineering
- Orthopedic Surgery
- Materials Science
Background:
- Modular tibial components in total knee replacements can lead to wear on polyethylene inserts.
- Micromotion at the implant interface is a significant factor contributing to this wear mechanism.
Purpose of the Study:
- To quantify the micromotion between modular tibial components in contemporary total knee implant designs.
- To assess the extent of fretting and wear at the tibial insert-baseplate interface.
Main Methods:
- Mechanical testing of nine total knee implant designs using a servohydraulic testing machine.
- Measurement of anteroposterior and mediolateral motion at the tibial insert and baseplate interface with an extensometer.
- Application of a 100 N load to simulate interface stress.
Main Results:
- All analyzed implants exhibited sufficient motion at the modular interface to cause fretting.
- Hundreds of microns of motion were recorded even under a 100 N load.
- Significant variability in motion was observed between implants of the same design.
Conclusions:
- The study confirms that micromotion is a prevalent issue in current modular total knee implant designs.
- Existing locking mechanisms may be insufficient to prevent fretting and subsequent wear.
- Further research and development are needed to enhance the stability and longevity of modular tibial components.