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BackgroundFinite element analysis (FEA) of the proximal femur has been previously validated with large mesh size, but these were insufficient to simulate the model with small implants in recent studies. This study aimed to validate the proximal femoral computed tomography (CT)-based specimen-specific FEA model with smaller mesh size using fresh frozen cadavers.MethodsTwenty proximal femora from 10 cadavers (mean age, 87.1 years) were examined. CT was performed on all specimens with a calibration phantom. Nonlinear FEA prediction with stance configuration was performed using Mechanical Finder (mesh,1.5 mm tetrahedral elements; shell thickness, 0.2 mm; Poisson’s coefficient, 0.3), in comparison with mechanical testing. Force was applied at a fixed vertical displacement rate, and the magnitude of the applied load and displacement were continuously recorded. The fracture load and stiffness were calculated from force–displacement curve, and the correlation between mechanical testing and FEA prediction was examined.ResultsA pilot study with one femur revealed that the equations proposed by Keller for vertebra were the most reproducible for calculating Young’s modulus and the yield stress of elements of the proximal femur. There was a good linear correlation between fracture loads of mechanical testing and FEA prediction (R2 = 0.6187) and between the stiffness of mechanical testing and FEA prediction (R2 = 0.5499). There was a good linear correlation between fracture load and stiffness (R2 = 0.6345) in mechanical testing and an excellent correlation between these (R2 = 0.9240) in FEA prediction.ConclusionsCT-based specimen-specific FEA model of the proximal femur with small element size was validated using fresh frozen cadavers. The equations proposed by Keller for vertebra were found to be the most reproducible for the proximal femur in elderly people.

The incidence of glucocorticoid-associated osteonecrosis in SLE patients decreased in association with a decrease in glucocorticoid administration after introduction of immunosuppressant agents.

BackgroundThe purpose of this study was to validate a diaphyseal femoral fracture model using a finite element analysis (FEA) with mechanical testing in fresh-frozen cadavers.MethodsWe used 18 intact femora (9 right and 9 left) from 9 fresh-frozen cadavers. Specimens were obtained from 5 males and 4 females with a mean age of 85.6 years. We compared a computed tomography (CT)-based FEA model to diaphyseal femoral fracture loads and stiffness obtained by three-point bending. Four material characteristic conversion equations (the Keyak, Carter, and Keller equations plus Keller’s equation for the vertebra) with different shell thicknesses (0.3, 0.4, and 0.5 mm) were compared with the mechanical testing.ResultsThe average fracture load was 4582.8 N and the mean stiffness was 942.0 N/mm from actual mechanical testing. FEA prediction using Keller’s equation for the vertebra with a 0.4-mm shell thickness showed the best correlations with the fracture load (R2 = 0.76) and stiffness (R2 = 0.54). Shell thicknesses of 0.3 and 0.5 mm in Keller’s equation for the vertebra also showed a strong correlation with fracture load (R2 = 0.66 for both) and stiffness (R2 = 0.50 and 0.52, respectively). There were no significant correlations with the other equations.ConclusionWe validated femoral diaphyseal fracture loads and stiffness using an FEA in a cadaveric study.