Abstract
Tibiofemoral motions are fundamental to the function (strength, stability, ROM) and longevity of total knee replacements (TKR). Although a wide range of TKR kinematics have been reported, few studies have reported kinematics of a single TKR design utilising a variety of tibial articular surfaces. We hypothesised that increased articular constraint, from four different tibial inserts, would result in reduced tibio-femoral translations during dynamic activities.
We tested 22 knees with excellent early clinical outcomes after primary TKR. All knees received the same PCL retaining arthroplasty; with six curved tibial inserts, six flat inserts, six laterally pivoting inserts and four translating/rotating mobile bearing inserts. Fluoroscopic images of knees were acquired during gait, stair, and deep flexion activities. CAD model based shape matching was performed to determine 3D knee kinematics.
There were significant differences in medial condy-lar translations for all activities, none for the lateral condyle. The medial condyle in knees with flat and mobile bearing inserts translated more anterior with flexion than knees with curved or pivoting inserts. Medial condyle translations were greater in mobile bearing knees than knees with flat inserts.
Our results indicate that condylar motions in TKR’s during dynamic activities can be modulated in a reasonably predictable manner by varying the degree of tibio-femoral constraint. Furthermore, the results show that significant control of translation can be achieved through asymmetric tibial insert conformity. These findings suggest it is possible to achieve a particular pattern of tibio-femoral translations and rotations in vivo through careful selection or design of the articular geometry.
The abstracts were prepared by Nico Verdoschot. Correspondence should be addressed to him at Orthopaedic Research Laboratory, Universitair Medisch Centrum, Orthopaedie / CSS1, Huispost 800, Postbus 9101, 6500 HB Nijmegen, Th. Craanenlaan 7, 6525 GH Nijmegen, The Netherlands.
