title: Specimen-specific modeling of hip fracture pattern and repair.
abstract: Hip fracture remains a major health problem for the elderly. Clinical studies have assessed fracture risk based on bone quality in the aging population and cadaveric testing has quantified bone strength and fracture loads. Prior modeling has primarily focused on quantifying the strain distribution in bone as an indicator of fracture risk. Recent advances in the extended finite element method (XFEM) enable prediction of the initiation and propagation of cracks without requiring a priori knowledge of the crack path. Accordingly, the objectives of this study were to predict femoral fracture in specimen-specific models using the XFEM approach, to perform one-to-one comparisons of predicted and in vitro fracture patterns, and to develop a framework to assess the mechanics and load transfer in the fractured femur when it is repaired with an osteosynthesis implant. Five specimen-specific femur models were developed from in vitro experiments under a simulated stance loading condition. Predicted fracture patterns closely matched the in vitro patterns; however, predictions of fracture load differed by approximately 50% due to sensitivity to local material properties. Specimen-specific intertrochanteric fractures were induced by subjecting the femur models to a sideways fall and repaired with a contemporary implant. Under a post-surgical stance loading, model-predicted load sharing between the implant and bone across the fracture surface varied from 59%:41% to 89%:11%, underscoring the importance of considering anatomic and fracture variability in the evaluation of implants. XFEM modeling shows potential as a macro-level analysis enabling fracture investigations of clinical cohorts, including at-risk groups, and the design of robust implants.
authors.affiliation: Center for Orthopaedic Biomechanics, University of Denver, Denver, CO 80208, USA.
authors.forename: Azhar A
authors.initials: AA
authors.lastname: Ali
authors.affiliation: Department of Industrial Engineering, School of Engineering and Architecture, University of Bologna, Bologna, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Cristofolini
authors.affiliation: Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Bologna, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Schileo
authors.affiliation: Center for Orthopaedic Biomechanics, University of Denver, Denver, CO 80208, USA.
authors.forename: Haixiang
authors.initials: H
authors.lastname: Hu
authors.affiliation: Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Bologna, Italy.
authors.forename: Fulvia
authors.initials: F
authors.lastname: Taddei
authors.affiliation: Center for Orthopaedic Biomechanics, University of Denver, Denver, CO 80208, USA; Colorado Joint Replacement, Porter Adventist Hospital, Denver, CO, USA.
authors.forename: Raymond H
authors.initials: RH
authors.lastname: Kim
authors.affiliation: Center for Orthopaedic Biomechanics, University of Denver, Denver, CO 80208, USA.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Rullkoetter
authors.affiliation: Center for Orthopaedic Biomechanics, University of Denver, Denver, CO 80208, USA. Electronic address: plaz@du.edu.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Laz
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D005260:Female; D005264:Femoral Fractures / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy*; D005269:Femur / Q000000981:diagnostic imaging / Q000503:physiopathology; D020342:Finite Element Analysis; D005592:Fracture Fixation; D006620:Hip Fractures / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D008297:Male; D008953:Models, Anatomic; D014057:Tomography, X-Ray Computed
keywords: Bone fracture; Extended finite element method (XFEM); Femur; Finite element; Hip fracture; Osteosynthesis