NUMERICAL ANALYSIS OF WEAR PROPAGATION IN CASE OF UNCONSTRAINED, SEMI-CONSTRAINED AND HIGH-CONSTRAINED TOTAL KNEE ARTHROPLASTIES

Total knee arthroplasties (TKAs) can be classified as unconstrained (or minimally constrained), semi-constrained and high-constrained. This study aims to investigate how different constraint levels affect volumetric wear by examining cruciate retained (CR) type TKAs with different sizes. The comparison was carried out by means of multibody simulations with identical kinetic and kinematic boundary conditions similar to load controlled knee simulators (ISO 14243–1). Three kinematic variations were examined: the unconstrained condition, the semi-constrained condition and the high-constrained condition. With these conditions, the volumetric wear rate was determined for each TKA configuration. It was concluded that semi-constrained condition, for instance, not permitting the relative rotation between the femoral component and the tibial insert, causes virtually no difference in wear propagation. Moderately elevated wear was observed if TKA motion was high-constrained to the point of only being able to carry out flexion-extension motion, similar to a constrained condylar knee (CCK) design. This study demonstrated that CR type TKAs show negligible wear when the constraint of the TKA is increased, or in other words, the degree of freedom of the TKA is decreased.