title: In vitro kinematic patterns are similar for a fixed platform and a mobile bearing prosthesis.
abstract: In vitro dynamic simulation of knee flexion was performed to quantify knee kinematics for a mobile bearing prosthesis that allows the tibial insert to translate and rotate with respect to the baseplate. Six cadaver knees were tested in the intact state, after implanting a fixed platform prosthesis, and after implanting a mobile bearing prosthesis. The mobile bearing prosthesis significantly increased the tibial internal rotation and medial shift compared with the intact knee, near 90 degrees of flexion. Both prostheses increased the patellar medial shift near 90 degrees of flexion. The patellar flexion was significantly larger for the mobile bearing prosthesis than for the fixed platform prosthesis for most of flexion. Motion of the insert with respect to the baseplate may have contributed to the variations in tibiofemoral kinematics, whereas tibiofemoral kinematic changes influenced the patellofemoral kinematics. Although the kinematics were similar for the 2 types of prosthesis, the possibility of complications related to increased patellar flexion and backside wear of the tibial insert should be considered.
authors.affiliation: Orthopaedic Biomechanics Laboratory, The Johns Hopkins University, Baltimore, Maryland 21205, USA.
authors.forename: John J
authors.initials: JJ
authors.lastname: Elias
authors.forename: Masaru
authors.initials: M
authors.lastname: Kumagai
authors.forename: Isaac
authors.initials: I
authors.lastname: Mitchell
authors.forename: Yasayuki
authors.initials: Y
authors.lastname: Mizuno
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Mattessich
authors.forename: J D
authors.initials: JD
authors.lastname: Webb
authors.forename: Edmund Y
authors.initials: EY
authors.lastname: Chao
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D002102:Cadaver; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D007720:Knee Prosthesis; D011474:Prosthesis Design; D013977:Tibia; D016474:Weight-Bearing