title: Does high-flexion total knee arthroplasty promote early loosening of the femoral component?
abstract: High-flexion knee replacements have been developed to accommodate a large range of motion (RoM > 120°). Knee implants that allow for higher flexion may be more sensitive to femoral loosening as the knee load is relatively high during deep knee flexion, which could result in an increased failure potential at the implant-cement interface of the femoral component. A 3D finite element knee model was developed including a posterior-stabilized high-flexion knee replacement to analyze the stress state at the femoral implant-cement interface during a full squatting movement (RoM ≤ 155°). During deep flexion (RoM > 120°), tensile and shear stress concentrations were found at the implant-cement interface beneath the proximal part of the anterior flange. Particularly, the shear stresses at this interface location increased during high flexion, from a peak stress of 4.03 MPa at 90° to 6.89 MPa at 140° of flexion. Tensile stresses were substantially lower, having a peak stress of 0.72 MPa at 100° of flexion. Using data from earlier interface strength experiments, none of the interface beneath the anterior flange was predicted to fail in the normal flexion range (RoM ≤ 120°), whereas the prediction increased to 2.2% of the interface during deeper knee flexion. Thigh-calf contact reduced the knee forces, interface load, and failure risk beyond 140-145° of flexion. Based on the more critical stresses at the femoral fixation site between 120° and 145° of flexion, we conclude that the femoral component has a higher risk of loosening at high-flexion angles.
authors.affiliation: Orthopaedic Research Laboratory, Radboud University Nijmegen Medical Centre, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands. j.zelle@orthop.umcn.nl
authors.forename: Jorrit
authors.initials: J
authors.lastname: Zelle
authors.forename: Dennis
authors.initials: D
authors.lastname: Janssen
authors.forename: Jolanda
authors.initials: J
authors.lastname: Van Eijden
authors.forename: Maarten
authors.initials: M
authors.lastname: De Waal Malefijt
authors.forename: Nico
authors.initials: N
authors.lastname: Verdonschot
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D001843:Bone Cements / Q000627:therapeutic use; D019544:Equipment Failure Analysis; D005269:Femur / Q000502:physiology*; D005360:Fibula / Q000502:physiology; D020342:Finite Element Analysis; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D008954:Models, Biological; D010329:Patella / Q000502:physiology; D011475:Prosthesis Failure; D016059:Range of Motion, Articular / Q000502:physiology; D013718:Tensile Strength / Q000502:physiology; D013977:Tibia / Q000502:physiology
chemical_list: D001843:Bone Cements