Mobile Bearing Knee
Arthroplasty
J. Roderick Davey, M.D.,
F.R.C.S.(C) Head, Division of
Orthopaedic Surgery Toronto Western Hospital Toronto, Ontario Clinical
experience has highlighted the need to minimize wear of the polyethylene in total
knee arthroplasty (TKA). It has long been recognized that the wear rate of
the articulating surfaces is proportional to the contact pressures imposed
upon them during movement. However, it is difficult to increase the
congruency of the surfaces without detrimentally affecting the kinematics of
the knee joint. In
the natural knee joint, incongruency of the opposing surfaces of the femoral
condyles and tibial plateau is accommodated by the menisci, which serve to
spread the applied load and thus reduce contact pressure. In the case of TKA,
it is possible to achieve the same effect by allowing one of the bearing
surfaces, typically the tibial articulating surface, to move relative to the
other. Semi-constrained or unconstrained movement of the tibial articulating
surface in the AP direction and rotation is needed to accurately mimic the
kinematics of the natural knee joint. The
Mobile Bearing Knee (MBK) is designed to maximize congruency between the
femoral and tibial articulating surfaces over the entire range of motion,
while providing movement of the tibial surface to maintain optimum
kinematics. It is anticipated that the increased congruency will reduce
contact pressures at the articulating surfaces, and thereby lead to reduced
wear. The MBK is a modular, anatomical, tricompartmental total knee
replacement, designed to accommodate posterior cruciate recession or
resection. Twenty-five MBK total knee arthroplasties have been performed at the Toronto Western Hospital since February 2, 1998. The early results of these cases will be presented including clinical scores and range of motion. Although early results may be of interest, long term follow-up is required to determine longevity of these TKA’s compared to the results of conventional TKA.  Previous Lecture |
