Subregional statistical shape modelling identifies lesser trochanter size as a possible risk factor for radiographic hip osteoarthritis, a cross-sectional analysis from the Osteoporotic Fractures in Men Study

BGF was a National Institute of Health Research academic clinical fellow whilst undertaking part of this research and is now a Medical Research Council clinical research fellow supported by grant MR/S021280/1. FRS was supported by a Medical Research Council UK grant MR/L010399/1 at the time of this study. This study used the SSM cohort funded by Versus Arthritis UK project grant ref 20244. The Osteoporotic Fractures in Men (MrOS) Study is supported by National Institutes of Health funding. The following institutes provide support: the National Institute on Aging (NIA), the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), the National Center for Advancing Translational Sciences (NCATS), and NIH Roadmap for Medical Research under the following grant numbers: R01 AR052000, K24 AR048841, U01 AG027810, U01 AG042124, U01 AG042139, U01 AG042140, U01 AG042143, U01 AG042145, U01 AG042168, U01 AR066160, and UL1 TR000128. Partial support for this work was provided by the Southwest Research Institute internal research project R9541 and NIAMS research grant AR052013. All authors have made significant contributions to the conception and design of this study, the acquisition of data, its analysis and interpretation. All authors helped draft the article before approving the final version of this manuscript. Dr B Faber ([email protected]) takes responsibility for the integrity of the work in its entirety.Peer reviewedPublisher PD

Linear viscoelasticity - bone volume fraction relationships of bovine trabecular bone

Trabecular bone has been previously recognized as time-dependent (viscoelastic) material, but the relationships of its viscoelastic behaviour with bone volume fraction (BV/TV) have not been investigated so far. Therefore, the aim of the present study was to quantify the time-dependent viscoelastic behaviour of trabecular bone and relate it to BV/TV. Uniaxial compressive creep experiments were performed on cylindrical bovine trabecular bone samples ([Formula: see text] ) at loads corresponding to physiological strain level of 2000 [Formula: see text] . We assumed that the bone behaves in a linear viscoelastic manner at this low strain level and the corresponding linear viscoelastic parameters were estimated by fitting a generalized Kelvin–Voigt rheological model to the experimental creep strain response. Strong and significant power law relationships ([Formula: see text] ) were found between time-dependent creep compliance function and BV/TV of the bone. These BV/TV-based material properties can be used in finite element models involving trabecular bone to predict time-dependent response. For users’ convenience, the creep compliance functions were also converted to relaxation functions by using numerical interconversion methods and similar power law relationships were reported between time-dependent relaxation modulus function and BV/TV

Nonlinear viscoelastic characterization of bovine trabecular bone

The time-independent elastic properties of trabecular bone have been extensively investigated, and several stiffness–density relations have been proposed. Although it is recognized that trabecular bone exhibits time-dependent mechanical behaviour, a property of viscoelastic materials, the characterization of this behaviour has received limited attention. The objective of the present study was to investigate the time-dependent behaviour of bovine trabecular bone through a series of compressive creep–recovery experiments and to identify its nonlinear constitutive viscoelastic material parameters. Uniaxial compressive creep and recovery experiments at multiple loads were performed on cylindrical bovine trabecular bone samples ([Formula: see text] ). Creep response was found to be significant and always comprised of recoverable and irrecoverable strains, even at low stress/strain levels. This response was also found to vary nonlinearly with applied stress. A systematic methodology was developed to separate recoverable (nonlinear viscoelastic) and irrecoverable (permanent) strains from the total experimental strain response. We found that Schapery’s nonlinear viscoelastic constitutive model describes the viscoelastic response of the trabecular bone, and parameters associated with this model were estimated from the multiple load creep–recovery (MLCR) experiments. Nonlinear viscoelastic recovery compliance was found to have a decreasing and then increasing trend with increasing stress level, indicating possible stiffening and softening behaviour of trabecular bone due to creep. The obtained parameters from MLCR tests, expressed as second-order polynomial functions of stress, showed a similar trend for all the samples, and also demonstrate stiffening–softening behaviour with increasing stress

Strength of titanium intramedullary implant versus miniplate fixation of mandibular condyle fractures

Objective. To test the strength of internal fixation of mandibular condyle fractures repaired with titanium miniplates versus titanium intramedullary implants. Study Design. Prospective laboratory experimentation in urethane mandible models and human cadaveric mandibles. Setting. Materials testing laboratory at an academic medical center. Methods. Osteotomies of the mandibular condyle were created in 40 urethane hemimandible models and 24 human cadaveric specimens. Half of the samples in each group were repaired with traditional miniplates, and the other half were repaired with intramedullary titanium implants. Anteroposterior and mediolateral loads were applied to the samples, and the displacement was measured with reference to the applied force. Results. Titanium intramedullary implants demonstrated statistically significant improved strength and stiffness versus miniplates in the urethane model experimental groups. Despite frequent plastic deformation and mechanical failures of the miniplates, a 1.6-mm-diameter titanium intramedullary pin did not mechanically fail in any of the cases. Intramedullary implantation failures were due to secondary fracture of the adjacent cortical bone or experimental design limitations including rotation of the smooth pin implant. Conclusion. Mechanical implant failures that were encountered with miniplate fixation were not seen with titanium intramedullary implants. These intramedullary implants provide stronger and more rigid fixation of mandibular condyle fractures than miniplates in this in vitro model. © 2012 American Academy of Otolaryngology - Head and Neck Surgery Foundation