Abstract
Introduction: Total knee arthroplasty (TKA) has become a successful clinical treatment for patients in regard to relief of pain, correction of deformity and restoration of function with promising long term behaviour [Pradhan et al. 2006].
In TKA the generation of polyethylene wear debris is mainly affected by the factors design of the articulating bearing, contact stresses, kinematics, implant material and surface finish [McEwen et al. 2005].
The objective of our study was to evaluate the in vitro wear behaviour of fixed bearing knee designs in comprehension to the contact mechanics and resultant kinematics for different degrees of congruency.
Material and Methods: Wear simulator testing on 12 TKA devices has been performed according to ISO 14243-1 under load control. The knee replacements were tested in the fixed bearing configurations LC, CR and DD with different degrees of tibio-femoral congruency.
For gravimetric wear assessment the protocol described in ISO 14243-2 has been used, followed by a kinematic analysis of the single test stations.
The articulating contact and subsurface stresses have been investigated in a finite element analysis.
Results: The contact areas are increasing from Search® Evolution LC (144 mm2) to Columbus® CR (235 mm2) and Columbus® DD (279 mm2), whereas the peak surface contact stresses are decreasing from Search® Evolution LC (34.4 MPa) to Columbus® CR (20.9 MPa) and Columbus® DD (18.1 MPa). The estimated amount of wear has decreased from Search® Evolution LC (21.4 mg/million cycles) to Columbus® CR (8.9 mg/million cycles) and Columbus® DD (2.2 mg/million cycles).
The wear rates between the knee design configurations differ substantially and statistically analysis demonstrates a significant difference (p< 0.01) between the test groups in correlation with congruency.
Conclusion: The present study demonstrates the influence of different bearing types on contact stresses, abrasive wear and kinematics for three different degrees of tibio-femoral congruency under elimination of production, material and sterilization parameters.
Corresponding author: Dr.-Ing. Thomas M. Grupp
Research and Development: e-mail: thomas.grupp@aesculap.de
Correspondence should be addressed to EORS Secretariat Mag. Gerlinde M. Jahn, c/o Vienna Medical Academy, Alserstrasse 4, 1090 Vienna, Austria. Fax: +43-1-4078274. Email: eors@medacad.org
