Electronic Letters to:

Knee: H. P. Delport, S. A. Banks, J. De Schepper, and J. Bellemans A kinematic comparison of fixed- and mobile-bearing knee replacements J Bone Joint Surg Br 2006; 88-B: 1016-1021 [Abstract] [Full text] [PDF]

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A kinematic comparison of fixed- and mobile-bearing knee replacements

Joby John, Mauffery CM   (16 August 2006)

A kinematic comparison of fixed- and mobile-bearing knee replacements 16 August 2006
Joby John, Registrar Robert Jones Agnes Hunt Hospital, Oswestry, Mauffery CM Send letter to journal: Re: A kinematic comparison of fixed- and mobile-bearing knee replacements jobyjohnm{at}yahoo.com Joby John, et al.	Sir, I read with great interest the article by Delport et al. It is clear from their work that decoupling of rotation does improve the in vivo kinematics. We would like to know the following: 1) Do the improved kinematics lead to an improvement in flexion? (weight bearing and non weight bearing) 2) Do the authors agree that decoupling the rotation does indeed reduce wear? It would seem that the alignment of the UHMWPE on the underside of the tibial insert would still be perpendicular to the line of stress and hence maligned to the direction of rotation. It would also seem that the LCS prosthesis would have more conforming surfaces simply because it was not designed to roll back. Therefore, any conclusions based on the work on LCS knees would probably be misplaced. 3) The symmetrical slide on cam post mechanism would produce more symmetrical wear on the post, hence probably a reduction in the volume of wear debris and the possibility of disengagement at a latter date, but would this benefit not be offset by the wear debris from the undersurface of the tibial insert? It seems that the mobile bearing posterior stabilised knee would definitely produce more normal kinematics, but whether this translates into increased survivorship is debatable. J. John, Registrar, C.M. Mauffery, Robert Jones Agnes Hunt Hospital, Oswestry, UK.