title: Predicting mouse vertebra strength with micro-computed tomography-derived finite element analysis.
abstract: As in clinical studies, finite element analysis (FEA) developed from computed tomography (CT) images of bones are useful in pre-clinical rodent studies assessing treatment effects on vertebral body (VB) strength. Since strength predictions from microCT-derived FEAs (μFEA) have not been validated against experimental measurements of mouse VB strength, a parametric analysis exploring material and failure definitions was performed to determine whether elastic μFEAs with linear failure criteria could reasonably assess VB strength in two studies, treatment and genetic, with differences in bone volume fraction between the control and the experimental groups. VBs were scanned with a 12-μm voxel size, and voxels were directly converted to 8-node, hexahedral elements. The coefficient of determination or R (2) between predicted VB strength and experimental VB strength, as determined from compression tests, was 62.3% for the treatment study and 85.3% for the genetic study when using a homogenous tissue modulus (E t) of 18 GPa for all elements, a failure volume of 2%, and an equivalent failure strain of 0.007. The difference between prediction and measurement (that is, error) increased when lowering the failure volume to 0.1% or increasing it to 4%. Using inhomogeneous tissue density-specific moduli improved the R (2) between predicted and experimental strength when compared with uniform E t=18 GPa. Also, the optimum failure volume is higher for the inhomogeneous than for the homogeneous material definition. Regardless of model assumptions, μFEA can assess differences in murine VB strength between experimental groups when the expected difference in strength is at least 20%.
authors.affiliation: Department of Veterans Affairs, Tennessee Valley Healthcare System , Nashville, TN, USA ; Department of Orthopaedic Surgery and Rehabilitation, Vanderbilt University, Medical Center East , Nashville, TN, USA ; Department of Biomedical Engineering, Vanderbilt University Medical Center , Nashville, TN, USA ; Center for Bone Biology, Vanderbilt University Medical Center , Nashville, TN, USA.
authors.forename: Jeffry S
authors.initials: JS
authors.lastname: Nyman
authors.affiliation: Department of Orthopaedic Surgery and Rehabilitation, Vanderbilt University, Medical Center East , Nashville, TN, USA.
authors.forename: Sasidhar
authors.initials: S
authors.lastname: Uppuganti
authors.affiliation: Department of Veterans Affairs, Tennessee Valley Healthcare System , Nashville, TN, USA ; Department of Biomedical Engineering, Vanderbilt University Medical Center , Nashville, TN, USA ; Center for Bone Biology, Vanderbilt University Medical Center , Nashville, TN, USA.
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Makowski
authors.affiliation: Department of Veterans Affairs, Tennessee Valley Healthcare System , Nashville, TN, USA ; Center for Bone Biology, Vanderbilt University Medical Center , Nashville, TN, USA.
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Rowland
authors.affiliation: Center for Bone Biology, Vanderbilt University Medical Center , Nashville, TN, USA ; Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University Medical Center , Nashville, TN, USA.
authors.forename: Alyssa R
authors.initials: AR
authors.lastname: Merkel
authors.affiliation: Department of Veterans Affairs, Tennessee Valley Healthcare System , Nashville, TN, USA ; Center for Bone Biology, Vanderbilt University Medical Center , Nashville, TN, USA ; Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University Medical Center , Nashville, TN, USA ; Department of Cancer Biology, Vanderbilt University Medical Center , Nashville, TN, USA.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Sterling
authors.affiliation: Musculoskeletal Biomechanics Section, Southwest Research Institute , San Antonio, TX, USA.
authors.forename: Todd L
authors.initials: TL
authors.lastname: Bredbenner
authors.affiliation: Department of Veterans Affairs, Tennessee Valley Healthcare System , Nashville, TN, USA ; Department of Orthopaedic Surgery and Rehabilitation, Vanderbilt University, Medical Center East , Nashville, TN, USA ; Center for Bone Biology, Vanderbilt University Medical Center , Nashville, TN, USA ; Vanderbilt University Institute of Imaging Sciences, Vanderbilt University Medical Center , Nashville, TN, USA.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Perrien