title: In vivo knee kinematics during high flexion after a posterior-substituting total knee arthroplasty.
abstract: The objective of this study was to investigate biomechanics of TKA patients during high flexion. Six patients (seven knees) with a posterior-substituting TKA and weight-bearing flexion >130 degrees were included in the study. The six degree-of-freedom kinematics, tibiofemoral contact, and cam-post contact were measured during a deep knee bend using dual-plane fluoroscopy. The patients achieved average weight-bearing flexion of 139.5 +/- 4.5 degrees. Posterior femoral translation and internal tibial rotation increased steadily beyond 90 degrees flexion, and a sharp increase in varus rotation was noted at maximum flexion. Initial cam-post engagement was observed at 100.3 +/- 6.7 degrees flexion. Five knees had cam-post disengagement before maximum flexion. Lateral femoral condylar lift-off was found in five out of seven knees at maximum flexion, and medial condylar lift-off was found in one knee. Future studies should investigate if the kinematic characteristics of posterior-substituting TKA knees noted in this study are causative factors of high knee flexion.
authors.affiliation: Department of Orthopaedic Surgery, Bioengineering Laboratory, Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street, GRJ 1215, Boston, MA 02114, USA.
authors.forename: Angela L
authors.initials: AL
authors.lastname: Moynihan
authors.forename: Kartik M
authors.initials: KM
authors.lastname: Varadarajan
authors.forename: George R
authors.initials: GR
authors.lastname: Hanson
authors.forename: Sang-Eun
authors.initials: SE
authors.lastname: Park
authors.forename: Kyung Wook
authors.initials: KW
authors.lastname: Nha
authors.forename: Jeremy F
authors.initials: JF
authors.lastname: Suggs
authors.forename: Todd
authors.initials: T
authors.lastname: Johnson
authors.forename: Guoan
authors.initials: G
authors.lastname: Li
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008875:Middle Aged; D016059:Range of Motion, Articular; D013314:Stress, Mechanical; D016474:Weight-Bearing