Dual-energy CT hybridation and kernel processing effects on the estimation of bone mineral mass and density: a calcination study on ex vivo human femur.

INTRODUCTION: Recent technological advances with dual-energy quantitative computed tomography (DEQCT) allow to combine two images of different level of energy to obtain simulated mono-energetic images at 60 keV (SIM60KeV-QCT) with improved image contrast in clinical practice. This study includes three topics: (1) compare bone mineral content (BMC), areal and volumetric bone mineral density (aBMD, vBMD) obtained with SIM60KeV-QCT, single-energy QCT (SEQCT), and dual X-ray absorptiometry (DXA); (2) compare ash density and weight with respective vBMD and BMC assessed on SIM60KeV-QCT, SEQCT, and DXA; and (3) compare the influence of reconstruction kernels on the accuracy of vBMD and BMC using ash density and ash weight as the reference values. METHODS: DXA, SEQCT, and DEQCT acquisitions were performed ex vivo on 42 human femurs. Standard kernel (SK) and bone kernel (BK) were applied to each stack of images. Ten diaphyses and 10 femoral necks were cut, scanned, and reconstructed using the techniques described above. Finally, the bone specimens were calcined to obtain the ash weight. RESULTS: QCT analysis (SEQCT, SIM60KeV-QCT) underestimated BMC value compared to DXA. For femoral necks, all QCT analyses provided an unbiased estimate of ash weight but underestimated ash density regardless of the kernel used. For femoral diaphysis, SEQCT BK, SIM60KeV-QCT BK, and SK underestimated ash weight but not ash density. CONCLUSION: BMC and vBMD quantifications with the SIM60KeV-QCT gave similar results as the SEQCT. Further studies are needed to optimize the use of SIM60KeV-QCT in clinical situations. SK should be used given the effect of kernels on QCT assessment.

Risk Factors for the Incident Decline of Physical Performance in Older Men: The Prospective Strambo Study.

Risk factors of physical performance decline in older men remain uncertain. We assessed risk factors of incident physical performance deterioration in older men followed up prospectively. In a cohort of 821 men aged 60-87, physical performance was assessed by four tests (five chair stands, standing with closed eyes, forward and backward tandem walk) at baseline, 4 and 8 years. Various predictive biological measurements were performed at baseline. Serum creatinine/ cystatin C (Cr/CysC) ratio was used as an index of muscle mass. In multivariate models, higher age, higher fat mass index (FMI = fat mass/height2), low physical activity, prior stroke and fracture were associated with poor physical performance at baseline. Higher age, low physical activity, low calcium intake, prior non-vertebral fractures, low apparent free testosterone concentration and poor health status were associated with higher risk of loss to follow-up. Low grip strength, Parkinson's disease and stroke were associated with higher risk of incident inability to do five chair stands. Low Cr/CysC ratio and high FMI were associated with high risk of incident inability to perform forward and backward tandem walk. Sarcopenic obesity (co-occurrence of lower tertile of Cr/CysC and upper tertile of FMI) was associated with higher risk of incident inability to perform forward (OR = 3.31, 95% CI 1.88-5.84, p < 0.001) and backward tandem walk and of incident inability to perform more than one test (OR = 5.82, 95% CI 1.29-26.27, p < 0.001). In conclusion, sarcopenic obesity and poor health are associated with higher risk of incident severe decline of physical performance.

Bone Microarchitecture Decline and Risk of Fall and Fracture in Men With Poor Physical Performance-The STRAMBO Study.

CONTEXT: High fracture risk in individuals with low muscle strength is attributed to high risk of falls. OBJECTIVE: This work aims to study the association of muscle mass and physical performance with bone microarchitecture decline and risk of fall and nonvertebral fracture in men. METHODS: A prospective, 8-year follow-up of a cohort was conducted among the general population. A total of 821 volunteer men aged 60 and older participated. Hip areal bone mineral density (aBMD) and appendicular lean mass (ALM) were assessed at baseline by dual x-ray absorptiometry. Lower-limb relative ALM (RALM-LL) is ALM-LL/(leg length)2. The physical performance score reflects the ability to perform chair stands and static and dynamic balance. Bone microarchitecture was assessed by high-resolution peripheral quantitative computed tomography (HR-pQCT) at baseline and after 4 and 8 years. Statistical analyses were adjusted for shared risk factors. Outcome measurements included the rate of change in the HR-pQCT indices, incident falls, and fractures. RESULTS: Cortical bone loss and estimated bone strength decline were faster in men with low vs normal RALM-LL (failure load: -0.74 ±â€…0.09 vs -0.43 ±â€…0.10%/year; P < .005). Differences were similar between men with poor and those with normal physical performance (failure load: -1.12 ±â€…0.09 vs -0.40 ±â€…0.05%/year; P < .001). Differences were similar between men having poor performance and low RALM-LL and men having normal RALM-LL and performance (failure load: -1.40 ±â€…0.17 vs -0.47 ±â€…0.03%/year; P < .001). Men with poor physical performance had a higher risk of fall (hazard ratio [HR] = 3.52; 95% CI, 1.57-7.90, P < .05) and fracture (HR = 2.68; 95% CI, 1.08-6.66, P < .05). CONCLUSION: Rapid decline of bone microarchitecture and estimated strength in men with poor physical performance and low RALM-LL may contribute to higher fracture risk.