title: Proximal Cadaveric Femur Preparation for Fracture Strength Testing and Quantitative CT-based Finite Element Analysis.
abstract: Cadaveric fracture testing is routinely used to understand factors that affect proximal femur strength. Because ex vivo biological tissues are prone to lose their mechanical properties over time, specimen preparation for experimental testing must be performed carefully to obtain reliable results that represent in vivo conditions. For that reason, we designed a protocol and a set of fixtures to prepare the femoral specimens such that their mechanical properties experienced minimal changes. The femora were kept in a frozen state except during preparation steps and mechanical testing. The relevant clinical measures of total hip and femoral neck bone mineral density (BMD) were obtained with a clinical dual X-ray absorptiometry (DXA) bone densitometer, and the 3D geometry and distribution of bone mineral were obtained using CT with a calibration phantom for quantitative estimations based on the greyscale values. Any possible bone disease, fracture, or the presence of implants or artifacts affecting the bone structure, was ruled out with X-ray scans. For preparation, all bones were carefully cleaned of excess soft tissue, and were cut and potted at the internal rotation angle of interest. A cutting fixture allowed the distal end of the bone to be cut off leaving the proximal femur at a desired length. To allow positioning of the femoral neck at prescribed angles during later CT scanning and mechanical testing, the proximal femoral shafts were potted in polymethylmethacrylate (PMMA) using a fixture designed specifically for desired orientations. The data collected from our experiments were then used for validation of quantitative computed tomography (QCT)-based finite element analysis (FEA), as described in a different protocol. In this manuscript, we present the protocol for the precise bone preparation for mechanical testing and subsequent QCT/FEA modeling. The current protocol was successfully applied to prepare about 200 cadaveric femora over a 6-year time period.
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic; Division of Engineering, Mayo Clinic; dragomirdaescu.dan@mayo.edu.
authors.forename: Dan
authors.initials: D
authors.lastname: Dragomir-Daescu
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic; Division of Engineering, Mayo Clinic.
authors.forename: Asghar
authors.initials: A
authors.lastname: Rezaei
authors.affiliation: Division of Engineering, Mayo Clinic.
authors.forename: Susheil
authors.initials: S
authors.lastname: Uthamaraj
authors.affiliation: Division of Engineering, Mayo Clinic.
authors.forename: Timothy
authors.initials: T
authors.lastname: Rossman
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic.
authors.forename: James T
authors.initials: JT
authors.lastname: Bronk
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic.
authors.forename: Mark
authors.initials: M
authors.lastname: Bolander
authors.affiliation: Division of Engineering, Mayo Clinic.
authors.forename: Vincent
authors.initials: V
authors.lastname: Lambert
authors.affiliation: Division of Engineering, Mayo Clinic.
authors.forename: Sean
authors.initials: S
authors.lastname: McEligot
authors.affiliation: Division of Engineering, Mayo Clinic.
authors.forename: Rachel
authors.initials: R
authors.lastname: Entwistle
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic.
authors.forename: Hugo
authors.initials: H
authors.lastname: Giambini
authors.affiliation: Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign.
authors.forename: Iwona
authors.initials: I
authors.lastname: Jasiuk
authors.affiliation: Department of Orthopedic Surgery, Mayo Clinic.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Yaszemski
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic; Department of Orthopedic Surgery, Mayo Clinic.
authors.forename: Lichun
authors.initials: L
authors.lastname: Lu
mesh_terms: D015502:Absorptiometry, Photon / Q000295:instrumentation / Q000379:methods*; D015519:Bone Density; D002102:Cadaver; D005269:Femur / Q000000981:diagnostic imaging; D005272:Femur Neck; D020342:Finite Element Analysis; D050723:Fractures, Bone / Q000000981:diagnostic imaging*; D006801:Humans; D014057:Tomography, X-Ray Computed / Q000379:methods*