In vivo determination of condylar lift-off and screw-home in a mobile-bearing total knee arthroplasty.
Twenty subjects implanted with the low-contact stress (LCS) cruciate-sacrificing, mobile-bearing total knee arthroplasty underwent dynamic videofluoroscopy during in vivo weight-bearing conditions using a 3-dimensional computer-aided design (CAD) interactive modeling method. Ninety percent of the subjects demonstrated significant lift-off during stance phase of gait. Condylar lift-off was present at both the medial and the lateral condyles. The maximal medial lift-off was 2.12 mm, whereas the greatest lateral lift-off was 3.53 mm. The maximal positive screw-home was 9.6 degrees, whereas the maximal negative or reverse screw-home was 6.2 degrees. The average screw-home rotation was positive 0.5 degrees. In 50% of patients, medial condylar translation was unexpectedly greater than lateral condylar motion. Condylar lift-off and screw-home motion are significant kinematic functions in this rotationally unconstrained total condylar knee arthroplasty.
Stiehl
J B
JB
Midwest Orthopaedic Biomechanical Laboratory, St. Luke's Hospital, Milwaukee, Wisconsin, USA.
Dennis
D A
DA
Komistek
R D
RD
Crane
H S
HS
D019645:Arthroplasty, Replacement, Knee; D001696:Biomechanical Phenomena; D001863:Bone Screws; D005471:Fluoroscopy; D005684:Gait / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology; D007720:Knee Prosthesis; D014741:Video Recording; D016474:Weight-Bearing / Q000502:physiology