title: In vivo kinematics for fixed and mobile-bearing posterior stabilized knee prostheses.
abstract: This is the first in vivo kinematic study to compare mobile-bearing with fixed-bearing prostheses in patients who had total knee arthroplasties. Femorotibial contact positions for 40 patients implanted with either a fixed-bearing or mobile-bearing prosthesis were analyzed using videofluoroscopy. Femorotibial contact paths were determined using a computer automated model-fitting technique. Nineteen of 20 patients in each group experienced posterior femoral rollback of their lateral condyles, with a mean of 3.6 and 3.7 mm for fixed-bearing and mobile-bearing prostheses respectively. Eighteen patients who had mobile-bearing prostheses and 17 patients with fixed-bearing knee prostheses experienced a normal pattern of axial rotation of 7.3 degrees and 4.1 degrees respectively. Eleven of 20 (55%) patients who had mobile-bearing prostheses implanted and eight of 20 (40%) patients who had fixed-bearing prostheses implanted did not experience femoral condylar lift-off. The remaining knees had condylar lift-off less than 2.4 mm for fixed-bearing prostheses and 1.7 mm for mobile-bearing prostheses, respectively. Patients who had mobile-bearing prostheses implanted experienced greater axial rotation and less condylar lift-off than patients who had fixed-bearing prostheses implanted. Both cruciate ligaments are sacrificed for the mobile and fixed-bearing total knee replacements. The results from the current study showed that, in both groups, the majority of patients experienced kinematics similar to those of a normal knee. However, the extent of lateral femoral condyle posterior rollback and the extent of axial rotation were less.
authors.affiliation: Ranawat Orthopaedic Center, New York, New York, USA.
authors.forename: Chitranjan S
authors.initials: CS
authors.lastname: Ranawat
authors.forename: Richard D
authors.initials: RD
authors.lastname: Komistek
authors.forename: Jose A
authors.initials: JA
authors.lastname: Rodriguez
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Dennis
authors.forename: Matt
authors.initials: M
authors.lastname: Anderle
mesh_terms: D006801:Humans; D007720:Knee Prosthesis; D011474:Prosthesis Design; D016059:Range of Motion, Articular