Kinematics of mobile bearing total knee arthroplasty

Abstract

Review of the kinematic patterns of fixed-vs. mobile-bearing TKA has not demonstrated major differences, with the following exceptions. Less (minimal) anteroposterior translation of both the medial and lateral femoral condyles was observed during gait in patients who received mobile-bearing designs than in those implanted with fixed-bearing TKA. This is likely secondary to the increased sagittal femorotibial conformity present in most mobile-bearing designs. This reduces polyethylene shear stresses and should result in lower polyethylene wear rates in mobile-bearing TKA. In rotating-platform mobile-bearing designs, axial rotation occurs primarily on the inferior surface of the polyethylene bearing, as compared with primarily on the superior surface in fixed-bearing TKA. This should reduce shear forces on the superior aspect of the polyethylene bearing, thereby lessening wear. Additionally, while average axial rotational values following TKA were limited (<10°), a significant number of subjects exhibited higher magnitudes (>20°) of rotation which exceed the rotational limits of most fixed bearing TKA designs. This may be an advantage of rotating-platform mobile-bearing TKA designs which can accommodate a wider range of axial rotation without creation of excessive polyethylene stresses. © 2005 Springer Medizin Verlag Heidelberg.