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Published on: May 8, 2014
Bi-unicondylar knee prosthesis functional assessment utilizing force-control wear testing
M Spinelli1, S Affatato, M K Harman
1Laboratorio di Tecnologia Medica, Istituti Ortopedici Rizzoli, Bologna, Italy.
Summary
This study simulated knee replacement wear and found that over time, the knee joint simulator showed significant changes in how the prosthesis moved, impacting its long-term function.
Area of Science:
- Orthopedic Surgery
- Biomedical Engineering
- Materials Science
Background:
- Knee prosthesis function varies with geometry, kinematics, and soft-tissue constraints.
- Unicondylar knee replacements (UKR) are particularly sensitive to these variations.
- Rigorous experimental simulations of UKR function under physiological, force-controlled conditions are lacking.
Purpose of the Study:
- To evaluate the long-term functional performance of a fixed-bearing bi-unicondylar knee replacement (Bi-UKR).
- To analyze wear behavior, femoral-tibial kinematics, and damage scars using a force-controlled knee simulator.
- To provide experimental insight into the effects of prosthesis design on wear and kinematics.
Main Methods:
- Utilized a force-controlled knee simulator under ISO 14243 simulated walking conditions.
- Mounted a widely used fixed-bearing unicompartmental knee replacement in a bi-unicondylar configuration.
- Analyzed wear rates, femoral-tibial contact point kinematics, and damage scars up to 2 million cycles.
Main Results:
- Wear rates were 10.27 mg/million cycles (medial) and 4.49 mg/million cycles (lateral).
- Femoral-tibial kinematics decreased significantly (65-74%) with cycling time.
- Focal damage scars extended 16-21 mm anterior/posterior; no significant medial/lateral damage differences were observed.
Conclusions:
- Accumulated changes in Bi-UKR articular conformity altered kinematics over time.
- Force-controlled wear simulation revealed significant kinematic deviations in anterior/posterior travel and medial/lateral travel.
- The study provides valuable experimental data on Bi-UKR functional performance and design implications.
