In Vivo Assessment of Age- and Loading Configuration-Related Changes in Multiscale Mechanical Behavior of the Human Proximal Femur Using MRI-Based Finite Element Analysis.

BACKGROUND: MRI-based finite element analysis (MRI-FEA) is the only method able to assess microstructural and whole-bone mechanical properties of the hip in vivo. PURPOSE: To examine whether MRI-FEA is capable of discriminating age-related changes in whole-bone mechanical performance and micromechanical behavior of the proximal femur, particularly considering the most common hip fracture-related sideways fall loading. STUDY TYPE: Retrospective. SUBJECTS: A total of nine younger (27 ± 3.2 years) and nine elderly (61 ± 3.9 years) healthy volunteers. FIELD STRENGTH/SEQUENCE: 3T; 3D fast field echo sequence. ASSESSMENT: The left proximal femurs were scanned and FE models created. FEA was performed to simulate sideways fall and stance loading for each femoral model. Apparent stiffness and high-risk (90th percentile) tensile and compressive strains of the proximal femur as well as the average strains within cubic regions of the femoral neck and greater trochanter were assessed. STATISTICAL TESTS: Paired and unpaired t-tests. RESULTS: Compared to the young group, the femoral stiffness of the elderly decreased by 39% and 40% (both P < 0.05) under the sideways fall and stance conditions, respectively. Accordingly, the high-risk tensile and compressive stains were elevated with aging (40% and 23% for sideways fall, 23% and 11% for stance conditions; all P < 0.05). However, the loading configuration-induced difference was only observed in the elderly group for the high-risk strains (22% for tension and 12% for compression; both P < 0.05). Additionally, compared to the stance condition, the sideways fall increased the average tensile (young: 108%, elderly: 123%; both P < 0.05) and compressive strains (young: 631%, elderly: 617%, both P < 0.05) within the greater trochanter rather than the femoral neck region. DATA CONCLUSION: In vivo MRI-FEA is capable of capturing age-related changes in both apparent-level stiffness and tissue-level micromechanical behavior of the proximal femur. However, the effect of sideways fall loading might be better reflected by tissue-level micromechanics rather than apparent stiffness. LEVEL OF EVIDENCE: 3 TECHNICAL EFFICACY STAGE: 1.

Age- and sex-related differences in muscle strength and physical performance in older Chinese.

BACKGROUND: Little is known about muscle strength and physical performance in Chinese. AIM: This study aimed to assess the age- and sex-related differences in muscle strength and physical performance in older Chinese. METHODS: Three hundred and eight healthy participants (110 males and 198 females) age 68.3 ± 6.1 (mean ± SD) years were enrolled in this cross-sectional study. The handgrip muscle strength (HGS) of the dominant hand was measured using a Jamar dynamometer. Physical performance was assessed by the Timed Up and Go test (TUG). The EuroQol five-dimension questionnaire (EQ-5D) was used to evaluate participants' health status. RESULTS: Men showed higher levels of HGS with a smaller percentage having low muscle strength compared with women. No differences were observed in TUG between sexes. No significant association of TUG and age was observed in males. However, older females had increased TUG and hence poorer performance. Good health status was associated with better physical performance but was not related to muscle strength in either sex. DISCUSSION: In men, there was no correlation between age and TUG, although a negative association with handgrip muscle strength was observed. For women, both muscle strength and physical performance declined with age. The sex-related differences in aging effects on physical performance in our study could partly explain why women have a higher incidence of hip fracture than men. CONCLUSION: Chinese women may be more vulnerable to severe sarcopenia in old age than men.

Measurement of visceral fat and abdominal obesity by single-frequency bioelectrical impedance and CT: a cross-sectional study.

OBJECTIVES: The measurement of visceral fat (VF) is clinically important for the identification of individuals at high risk of visceral obesity-related health conditions. Bioelectrical impedance analysis (BIA) is a widely available and frequently used body composition assessment method, but there have been few validation studies for the measurement of VF. This validation study investigated agreement between BIA and CT for the assessment of VF in adults. DESIGN: Cross-sectional study. SETTING: Between 2015 and 2016 in China. PARTICIPANTS: A total of 414 adults (119 men and 295 women) aged 40-82 years. PRIMARY AND SECONDARY OUTCOME MEASURES: CT-visceral fat area (VFA) was derived at the L2-3 and umbilicus level and VFA cut-offs for visceral obesity applied. BIA measurements of visceral fat level were compared with CT VFA findings using scatter plots and receiver operator characteristic (ROC) curves. RESULTS: Scatter plots showed poor agreement between BIA and CT-derived visceral fat measurements in both sexes (R=0.387-0.636). ROC curves gave optimum figures for sensitivity and specificity of 65% and 69% in women and 76% and 70% in men, respectively, for BIA to discriminate between adults with normal levels of VF and those with visceral obesity determined by CT. CONCLUSION: BIA has limited accuracy for the assessment of VF in adults in practice when compared with the criterion method.

QCT of the femur: Comparison between QCTPro CTXA and MIAF Femur.

QCT is commonly employed in research studies and clinical trials to measure BMD at the proximal femur. In this study we compared two analysis software options, QCTPro CTXA and MIAF-Femur, using CT scans of the semi-anthropometric European Proximal Femur Phantom (EPFP) and in vivo data from 130 Chinese elderly men and women aged 60-80 years. Integral (Int), cortical (Cort) and trabecular (Trab) vBMD, volume, and BMC of the neck (FN), trochanter (TR), inter-trochanter (IT), and total hip (TH) VOIs were compared. Accuracy was determined in the 5 mm wide central portion of the femoral neck of the EPFP. Nominal values were: cross-sectional area (CSA) 4.9 cm2, cortical thickness (C.Th) 2 mm, CortBMD 723 mg/cm3 and TrabBMD 100 mg/cm3. In MIAF the so-called peeled trabecular VOI was analyzed, which excludes subcortical bone to avoid partial volume artefacts at the endocortical border that artificially increase TrabBMD. For CTXA uncorrected, so called raw cortical values were used for the analysis. QCTPro and MIAF phantom results were: CSA 5.9 cm2 versus 5.1 cm2; C.Th 1.68 mm versus 1.92 mm; CortBMD 578 mg/cm3 versus 569 mg/cm3; and TrabBMD 154 mg/cm3 versus 104 mg/cm3. In vivo correlations (R2) of integral and trabecular bone parameters ranged from 0.63 to 0.96. Bland-Altman analysis for TH and FN TrabBMD showed that lower mean values were associated with higher differences, which means that TrabBMD differences between MIAF and CTXA are larger for osteoporotic than for normal patients, which can be largely explained by the inclusion of subcortical BMD in the trabecular VOI analyzed by CTXA in combination with fixed thresholds used to separate cortical from trabecular bone compartments. Correlations between CTXA corrected CortBMD and MIAF were negative, whereas raw data correlated positively with MIAF measurements for all VOIs questioning the validity of the CTXA corrections. The EPFP results demonstrated higher MIAF accuracy of cortical thickness and TrabBMD. Integral and trabecular bone parameters were highly correlated between CTXA and MIAF. Partial volume artefacts at the endocortical border artificially increased trabecular BMD by CTXA, especially for osteoporosis patients. With respect to volumetric cortical measurements with CTXA, the use raw data is recommended, because corrected data cause a negative correlation with MIAF CortBMD.