title: Computational modelling of mobile bearing TKA anterior-posterior dislocation.
abstract: Anterior-posterior stability in an unconstrained mobile-bearing total knee arthroplasty (TKA) and one with rotational constraints is compared in a computational model based on an ASTM test. Both TKA designs dislocate at loads greater than reported maximum in vivo forces. The posterior drawer forces (mean: 3027 N vs. 1817 N) needed to induce subluxation increase with a greater anterior jump distance (12 mm vs. 7 mm; refers to the vertical height of the anterior or posterior border of the tibial insert's articulating surface). The posterior jump distance for both tested TKA differed by 1.5 mm and had minimal effect on the magnitude of the anterior drawer forces at dislocation in mid-flexion (unconstrained vs. constrained: 445 N vs. 412 N). The unconstrained insert dislocated by means of spin-out whereas in the constrained TKA the femur dislocated from the bearing during posterior drawer and the bearing from the baseplate during anterior drawer. MCL function is an important consideration during ligament balancing since a ± 10% variation in MCL tension affects dislocation forces by ± 20%. The simulation platform provided the means to investigate TKA designs in terms of anterior-posterior stability as a function of knee flexion, collateral ligament function and mechanical morphology.
authors.affiliation: a Department of Mechanical and Mechatronic Engineering , Stellenbosch University , Stellenbosch , South Africa.
authors.forename: J H
authors.initials: JH
authors.lastname: Müller
authors.affiliation: b R&D Large Joints Department , Tornier Inc. , Montbonnot , France.
authors.forename: T
authors.initials: T
authors.lastname: Zakaria
authors.affiliation: c Sports Science Orthopaedic Clinic, Sports Science Institute of South Africa , Cape Town , South Africa.
authors.forename: W
authors.initials: W
authors.lastname: van der Merwe
authors.affiliation: d Department of Biotechnology and Life Sciences , Institute of Orthopedics and Traumatology, University of Insubria , Varese , Italy.
authors.forename: F
authors.initials: F
authors.lastname: D'Angelo
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D003198:Computer Simulation; D004867:Equipment Design; D005260:Female; D005269:Femur / Q000601:surgery; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology; D031221:Knee Dislocation / Q000503:physiopathology*; D007719:Knee Joint / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D008962:Models, Theoretical; D016059:Range of Motion, Articular; D012680:Sensitivity and Specificity
keywords: anterior–posterior stability; computational model; mobile bearing; total knee arthroplasty