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Polyethylene wear and variations in knee kinematics
D D D'Lima1, J C Hermida, P C Chen
1Scripps Clinic, La Jolla, CA 92037, USA.
Clinical Orthopaedics and Related Research
|November 22, 2001
Summary
High intensity and malalignment conditions significantly increase polyethylene wear in posterior cruciate-retaining total knee arthroplasty. This wear simulation helps explain variations observed in retrieved knee implants.
Area of Science:
- Biomaterials Engineering
- Orthopedic Biomechanics
- Tribology
Background:
- Total knee arthroplasty (TKA) aims to restore function and alleviate pain.
- Polyethylene insert wear is a critical factor influencing TKA longevity.
- Understanding wear mechanisms under various conditions is essential for improving implant design.
Purpose of the Study:
- To evaluate the wear rates of polyethylene inserts in a posterior cruciate-retaining TKA design.
- To investigate the impact of high intensity loading and malalignment on TKA wear.
- To correlate simulated wear with clinical observations in retrieved implants.
Main Methods:
- Utilized a six-station knee wear simulator to test posterior cruciate-retaining TKA designs.
- Tested six implants per group under low intensity, high intensity, and 3-degree varus malalignment conditions.
- Measured gravimetric wear of polyethylene inserts over 5,000,000 cycles using kinematic inputs from gait data.
Main Results:
- Wear rates differed significantly across tested groups.
- Low intensity group: 3.1 mg/million cycles.
- High intensity group: 7.4 mg/million cycles.
- Malalignment group: 9.2 mg/million cycles.
- Increased loading and varus malalignment led to higher wear rates.
Conclusions:
- Simulated wear is dependent on relative motions and loads at the articulating surface.
- High intensity loading and varus malalignment significantly accelerate polyethylene wear in TKA.
- Findings may explain variations in wear observed in retrieved clinical knee implants.