title: Fixation of total knee arthroplasty improved by mobile-bearing design.
abstract: We examined the in vivo displacement of mobile-bearing polyethylene and its effect on prosthesis-bone fixation. Thirty-five patients with the Interax ISA mobile platform total knee arthroplasties were examined by roentgen stereophotogrammetric analysis. Our protocol included weightbearing to measure the range of motion of the mobile platform in relation to the tibial component. We also studied the micromotions of the tibial component in relation to the tibia during a 2-year followup. The analysis of micromotion (maximum total motion mean, 0.5 mm; subsidence mean, 0.15 mm) showed this mobile platform design is stable and improves fixation at the prosthesis-bone interface. Longitudinal rotations of the mobile platform occurred in all patients and followed a homogeneous pattern of motion, depending on the examination. However, anteroposterior translations did not show any patterns with specific examination. This suggests the meniscal movement adapts itself to different weightbearing conditions. We measured the in vivo mobile-bearing displacement under static loading conditions. We also observed improved fixation at the bone-prosthesis interface.
authors.affiliation: Biomechanics Lab, Istituti Ortopedici Rizzoli, Bologna, Italy. a.russo@biomecior.it
authors.forename: Alessandro
authors.initials: A
authors.lastname: Russo
authors.forename: Luisa
authors.initials: L
authors.lastname: Montagna
authors.forename: Laura
authors.initials: L
authors.lastname: Bragonzoni
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Zampagni
authors.forename: Maurilio
authors.initials: M
authors.lastname: Marcacci
mesh_terms: D000328:Adult; D000368:Aged; D001175:Arthrography; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D005260:Female; D005500:Follow-Up Studies; D005548:Foreign-Body Migration / Q000517:prevention & control; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D009984:Orthopedic Fixation Devices; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D010780:Photogrammetry; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000601:surgery; D011446:Prospective Studies; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D012086:Reoperation; D012399:Rotation; D013314:Stress, Mechanical; D013997:Time Factors; D016896:Treatment Outcome; D016474:Weight-Bearing / Q000502:physiology