title: In vivo weight-bearing kinematics with medial rotation knee arthroplasty.
abstract: Knee arthroplasties are designed to accommodate flexion, axial rotation and anteroposterior (AP) translation. Axial rotation during extension varies, with some rotating platform devices allowing unrestricted rotation while some conforming fixed-bearing designs almost none. The purpose of this study was to examine in vivo kinematics of a fixed-bearing medial rotation-type arthroplasty (MRK) during weight-bearing activities. Fifteen knees with a medial pivot TKA design were studied during step and pivot activities using lateral fluoroscopy and model-image registration. Average knee kinematics during the step activity showed little AP translation or rotation from 0 degrees -100 degrees flexion. During the pivot activity, the mean tibial internal rotation in individual knees was 7 degrees (3 degrees -19 degrees ). Mean condylar translations for individual knees were 3mm medially and 5mm laterally. The medial pivot prosthesis design provides anteroposterior stability during demanding activities, and exhibits a medial pivot motion pattern when subjected to twisting.
authors.affiliation: South West London Elective Orthopaedic Centre, Dorking Road, Epsom, Surrey, UK. drmoonot@yahoo.co.uk
authors.forename: Pradeep
authors.initials: P
authors.lastname: Moonot
authors.forename: Mu
authors.initials: M
authors.lastname: Shang
authors.forename: Gilbert T
authors.initials: GT
authors.lastname: Railton
authors.forename: Richard E
authors.initials: RE
authors.lastname: Field
authors.forename: Scott A
authors.initials: SA
authors.lastname: Banks
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000534:rehabilitation*; D001696:Biomechanical Phenomena / Q000502:physiology; D005260:Female; D006801:Humans; D007700:Kinetics; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D012399:Rotation; D016474:Weight-Bearing / Q000502:physiology