title: Predicting the effect of tray malalignment on risk for bone damage and implant subsidence after total knee arthroplasty.
abstract: Tibial tray malalignment has been associated with increased subsidence and failure. We constructed a finite element model of knee arthroplasty to determine the biomechanical factors involved in increasing the risk of subsidence with malalignment. Four fresh-frozen human knees were implanted with a tibial tray and subjected to forces representative of walking for up to 100,000 cycles. Cyclic displacement was measured between the tray and proximal tibia. The vertical load was shifted medially to generate a load distribution ratio of 55:45 (medial/lateral) to represent neutral alignment or 75:25 to represent varus alignment. Subjected specific geometry and material properties were obtained from qCT scans of tibia to construct a finite element model. The tray was subjected to a single load cycle representing experimental conditions. Tray displacement computed by the model matched that measured experimentally. Forces representing varus tray alignment generated greater strains in the proximal tibia and a greater volume of bone was subjected to strains higher than the fatigue threshold. Local compressive strains directly correlated with experimental subsidence and failure. Our results indicate that failure after tray malalignment is likely due to fatigue damage to the proximal tibia rather than shear across the implant-bone interface or failure of the cement mantle.
authors.affiliation: Shiley Center for Orthopaedic Research and Education at Scripps Clinic, 11025 North Torrey Pines Road, Suite 140, La Jolla, California 92037, USA.
authors.forename: Jowene
authors.initials: J
authors.lastname: Wong
authors.forename: Nikolai
authors.initials: N
authors.lastname: Steklov
authors.forename: Shantanu
authors.initials: S
authors.lastname: Patil
authors.forename: Cesar
authors.initials: C
authors.lastname: Flores-Hernandez
authors.forename: Mark
authors.initials: M
authors.lastname: Kester
authors.forename: Clifford W
authors.initials: CW
authors.lastname: Colwell
authors.forename: Darryl D
authors.initials: DD
authors.lastname: D'Lima
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000706:statistics & numerical data; D001696:Biomechanical Phenomena; D001843:Bone Cements; D017760:Bone Malalignment / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D002102:Cadaver; D004548:Elasticity; D020342:Finite Element Analysis; D056305:Genu Varum / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D006801:Humans; D007720:Knee Prosthesis / Q000009:adverse effects* / Q000706:statistics & numerical data; D011183:Postoperative Complications / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D011237:Predictive Value of Tests; D012307:Risk Factors; D013314:Stress, Mechanical; D013977:Tibia / Q000503:physiopathology / Q000601:surgery
chemical_list: D001843:Bone Cements