Abstract
Introduction Although most surgeons agree that the functional results obtained with modern total knee arthroplasty are acceptable, it is clear that even with the most recent designs it is still impossible to duplicate the behaviour and functional performance of a normal knee.
Methods I present a review of the literature and personal experience.
Results Recent kinematic studies have shown that modern TKA designs consistently provoke aberrant kinematics compared to the normal knee, mainly due to the absence of the ACL and the inability to maintain a functional PCL. With regard to roll-back, PS cam-post designs appear to perform better than PCL retaining knees, but only in deeper degrees of flexion, usually only beyond 90°. Whether it is striclty necessary to try to obtain normal kinematics with our TKA designs, is still an open debate.
Conclusions It is clear however that the aberrant kinematics we have noted with the current designs, are the direct cause of the flexion limit we see in many of our patients. Furthermore they probably also are the basis for many of the discomorts associated with modern TKA, such as difficulties in stair descent, chair rise, pivoting activities, thrust instabilities etc. With regard to these issues, I believe there are two potential directions to improve our current TKA designs; (1) by introducing the concept of guided-motion (intrinsic mechanism), or (2) by maintaining or restoring the (extrinsic) determinants of kinematics, i.e. the cruciate ligaments, the joint configuration and the extra-articular structures.
In relation to the conduct of this study, one or more of the authors has received, or is likely to receive direct material benefits.
The abstracts were prepared by Mr Jerzy Sikorski. Correspondence should be addressed to him at the Australian Orthopaedic Association, Ground Floor, William Bland Centre, 229 Macquarie Street, Sydney NSW 2000, Australia.
