RESUMO
Purpose To evaluate the performance of three imaging methods (radiography, dual-energy x-ray absorptiometry [DXA], and quantitative computed tomography [CT]) and that of a numerical analysis with finite element modeling (FEM) in the prediction of failure load of the proximal femur and to identify the best densitometric or geometric predictors of hip failure load. Materials and Methods Institutional review board approval was obtained. A total of 40 pairs of excised cadaver femurs (mean patient age at time of death, 82 years ± 12 [standard deviation]) were examined with (a) radiography to measure geometric parameters (lengths, angles, and cortical thicknesses), (b) DXA (reference standard) to determine areal bone mineral densities (BMDs), and (c) quantitative CT with dedicated three-dimensional analysis software to determine volumetric BMDs and geometric parameters (neck axis length, cortical thicknesses, volumes, and moments of inertia), and (d) quantitative CT-based FEM to calculate a numerical value of failure load. The 80 femurs were fractured via mechanical testing, with random assignment of one femur from each pair to the single-limb stance configuration (hereafter, stance configuration) and assignment of the paired femur to the sideways fall configuration (hereafter, side configuration). Descriptive statistics, univariate correlations, and stepwise regression models were obtained for each imaging method and for FEM to enable us to predict failure load in both configurations. Results Statistics reported are for stance and side configurations, respectively. For radiography, the strongest correlation with mechanical failure load was obtained by using a geometric parameter combined with a cortical thickness (r(2) = 0.66, P < .001; r(2) = 0.65, P < .001). For DXA, the strongest correlation with mechanical failure load was obtained by using total BMD (r(2) = 0.73, P < .001) and trochanteric BMD (r(2) = 0.80, P < .001). For quantitative CT, in both configurations, the best model combined volumetric BMD and a moment of inertia (r(2) = 0.78, P < .001; r(2) = 0.85, P < .001). FEM explained 87% (P < .001) and 83% (P < .001) of bone strength, respectively. By combining (a) radiography and DXA and (b) quantitative CT and DXA, correlations with mechanical failure load increased to 0.82 (P < .001) and 0.84 (P < .001), respectively, for radiography and DXA and to 0.80 (P < .001) and 0.86 (P < .001) , respectively, for quantitative CT and DXA. Conclusion Quantitative CT-based FEM was the best method with which to predict the experimental failure load; however, combining quantitative CT and DXA yielded a performance as good as that attained with FEM. The quantitative CT DXA combination may be easier to use in fracture prediction, provided standardized software is developed. These findings also highlight the major influence on femoral failure load, particularly in the trochanteric region, of a densitometric parameter combined with a geometric parameter. (©) RSNA, 2016 Online supplemental material is available for this article.
Assuntos
Fraturas do Fêmur/diagnóstico por imagem , Fraturas do Quadril/diagnóstico por imagem , Absorciometria de Fóton , Idoso , Idoso de 80 Anos ou mais , Densidade Óssea , Cadáver , Feminino , Análise de Elementos Finitos , Humanos , Imageamento Tridimensional , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Interpretação de Imagem Radiográfica Assistida por Computador , Estresse Mecânico , Tomografia Computadorizada por Raios X/métodosRESUMO
BACKGROUND: No study has compared the bone histopathologic findings in renal transplant patients receiving cyclosporine A (CsA) monotherapy with those in patients receiving a non-CsA regimen. The aim of this study was to compare bone densitometry and histomorphometry findings in patients receiving CsA monotherapy versus those receiving azathioprine + prednisolone dual therapy. METHODS: A bone biopsy and densitometry were performed in 13 patients receiving CsA monotherapy and 12 patients receiving azathioprine + prednisolone, who had been on these regimens since the time of transplantation. Fourteen men and 11 women, age 51+/-12 years, with 140+/-75 months since transplantation, were included. RESULTS: A low bone mineral density (BMD) was observed in patients on both immunosuppressive schemes-most notably at the distal radius and less significantly at the lumbar spine. No significant differences in BMD were observed between immunosuppressive groups. Histopathologic analysis of the group as a whole revealed mixed uremic bone disease in 42%, adynamic bone in 29%, hyperparathyroid disease in 17%, and normal bone in 12%. Patients showed a slight increase in osteoclast number and function, decreased osteoblast number and function, and retardation of dynamic parameters. No differences in histopathologic diagnosis or histomorphometric findings were observed between the immunosuppressive therapy groups. In addition to the immunosuppressive drugs, male gender and old age negatively affected bone mass. CONCLUSIONS: Both prednisolone and CsA were associated with slight osteoclast stimulation and osteoblast suppression and marked retardation of mineral apposition and bone formation rates. Both drugs were also associated with reduced BMD at the axial and appendicular skeleton, even though a nonsignificant trend to a better-preserved lumbar spine BMD was observed in the CsA group.