title: Changes in microgaps, micromotion, and trabecular strain from interlocked cement-trabecular bone interfaces in total knee replacements with in vivo service.
abstract: The initial fixation of cemented Total Knee Replacements (TKRs) relies on mechanical interlock between cement and bone, but loss of interlock occurs with in vivo service. In this study, cement-trabeculae gap morphology and micromechanics were measured for lab prepared (representing post-operative state) and postmortem retrieval (with in vivo remodeling) TKRs to determine how changes in fixation affect local micromechanics. Small specimens taken from beneath the tibial tray were loaded with 1 MPa axial compression and the local micromechanics of the trabeculae-cement interface was quantified using digital image correlation. Lab prepared trabeculae that initially interlock with cement had small gaps (ave:14 μm) and limited micromotion (ave:1 μm) which were larger near the cement border. Trabecular resorption was prevalent following in vivo service; interface gaps became larger (ave:40 μm) and micromotion increased (ave:6 μm), particularly near the cement border. Interlocked trabeculae from lab prepared specimens exhibited strains that were 20% of the supporting bone strain, indicating the trabeculae were initially strain shielded. The spatial and temporal progression of gaps, micromotion, and bone strain was complex and much more variable for post-mortem retrievals compared to the lab prepared specimens. From a clinical perspective, attaining more initial interlock results in cement-bone interfaces that are better fixed with less micromotion. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1019-1025, 2016.
authors.affiliation: Department of Orthopedic Surgery, State University of New York, Upstate Medical University, 3216 IHP, 750 East Adams Street, Syracuse, New York, 13210.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Miller
authors.affiliation: Department of Orthopedic Surgery, State University of New York, Upstate Medical University, 3216 IHP, 750 East Adams Street, Syracuse, New York, 13210.
authors.forename: Jacklyn R
authors.initials: JR
authors.lastname: Goodheart
authors.affiliation: Department of Orthopedic Surgery, State University of New York, Upstate Medical University, 3216 IHP, 750 East Adams Street, Syracuse, New York, 13210.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Khechen
authors.affiliation: Nijmegen Medical Centre, Radboud University, Nijmegen, The Netherlands.
authors.forename: Dennis
authors.initials: D
authors.lastname: Janssen
authors.affiliation: Department of Orthopedic Surgery, State University of New York, Upstate Medical University, 3216 IHP, 750 East Adams Street, Syracuse, New York, 13210.
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Mann
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D001843:Bone Cements; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007720:Knee Prosthesis / Q000706:statistics & numerical data*; D008297:Male; D011475:Prosthesis Failure
chemical_list: D001843:Bone Cements
keywords: bone strain; knee replacement; loosening; micromotion; trabecular resorption