Computerized analysis of gray-value profiles in spongy and cortical bone. Clinical experience.

RATIONALE AND OBJECTIVES: Osteoporosis is characterized by a loss of bone mineral density and deterioration of structure. The authors present a structural parameter for the quantitative assessment of osteoporotic changes in vertebral bone. METHODS: In 40 patients without or with known osteoporotic fractures, spongiosa and cortical bone mineral density was measured in lumbar vertebrae 1 to 3 by quantitative CT. Additional axial high-resolution CT slices were obtained for the structural analysis. In the spongiosa, the gray-value profile along a horizontal line in the CT slice was used, whereas in the cortical shell a profile was obtained from the cortical ridge. Both profiles were intersected with a horizontal line of variable position, and the maximum number of intersections was determined. RESULTS: The maximum number of intersections is significantly higher in cases with fractures (spongiosa 48.6, cortical shell 77.3) than in cases without fractures (spongiosa 42.1, cortical shell 62.4). It also correlates with bone mineral density and age. CONCLUSIONS: The presented method shows significantly different numeric results for patients with and without osteoporotic fractures. The analysis is easy to perform and provides additional information on the bone structure that may be used in combination with bone mineral density measurements.     

Assessment of vertebral bone mineral density using volumetric quantitative CT

PURPOSE: The purpose of this work was to determine the precision and diagnostic efficacy of bone mineral density (BMD) measures based on volumetric quantitative CT (QCT) of the spine. METHOD: Volumetric CT scans of L1 and L2 (GE-9800Q; 80 kVp, 140 mAs, 3 mm slices) were acquired in a cohort of 62 osteoporotic women (mean age 70.4 years, T(DXA hip or spine) < -2.5), of whom 20 had vertebral fractures and 42 were nonfractured control subjects. An image analysis technique delineated trabecular, cortical, and integral regions in reference to a vertebra-fixed coordinate system. We computed precision values and fracture control differences for these new regions and for single-slice QCT and dual X-ray absorptiometry (DXA) measures synthesized from the volumetric data. RESULTS: Volumetric trabecular BMD showed higher precision (1.3%) than the synthesized single-slice measures (2.1-2.8%). Volumetric and single-slice trabecular BMD showed equivalent decrements between fractured and nonfractured subjects (17-19%), with integral BMD showing smaller and less significant differences (7-8%). CONCLUSION: Volumetric and single-slice QCT techniques are equivalent for vertebral fracture risk estimation, but volumetric techniques should be superior for monitoring therapy efficacy.     

Bone density and geometry in assessing hip fracture risk in post-menopausal women

We used femoral neck structural parameters (FNSPs), calculated from bone mineral density (BMD) measurements of the femoral neck by dual X-ray absorptiometry, to discriminate osteoporotic fractures of the proximal femur in post-menopausal women. We compared 1646 women without fracture and 429 women with hip fractures, including 273 with femoral neck (FN) and 156 with trochanter (TR) fractures. The association between the studied parameters and the fractures was modelled using multiple logistic regression, and included age, height and weight. Fracture-predicted probability (FPP) was also calculated for each predictor tested. Receiver operating characteristic (ROC) curve areas with their standard errors (SEs) were calculated for the fracture status, having the calculated FPP as a test variable. The areas were compared by the Hanley-McNeil test. Hip fracture had lower BMD, cross-sectional area (CSA), section modulus (SM) and cortical thickness (CT), and higher buckling ratio (BR), than controls. To the same extent as FN BMD, BR best predicted the risk for each fracture, showing ROC curve areas of 0.809 (SE 0.011) for hip fracture, 0.789 (SE 0.014) for FN fracture, and 0.848 (SE 0.016) for TR fracture. The association of BR with fracture risk did not differ from that of FN BMD, which has a ROC curve area of 0.801 (SE 0.011) for hip fracture, 0.778 (SE 0.014) for FN fracture, and 0.852 (SE 0.016) for TR fracture. Both FN BMD and BR predicted TR fracture significantly better than they did FN fracture. FNSPs, although interesting in understanding the biomechanics of bone fragility, do not appear to add diagnostic value to the simple measurement of BMD.     

Evaluation of the detectability of early mandible fracture healing findings in terms of vitality aspect by using micro-CT technology in postmortem interval

The purpose of the present study was to investigate the vitality aspect of mandibular fractures using micro-CT in the analysis of bone mineral density and other bone microstructure trabecular parameters in the postmortem interval. This study included 72 female Wistar rats. In the study groups, the rats’ mandibles were first fractured and after three days of living, the rats were sacrificed. In the control groups, the rats were sacrificed first and then the mandibles were fractured. All rats were left for a natural putrefaction period according to their group’s time as week-0, week-1, week-2, week-4, week-8, and week-12. All fractured hemi-mandibles were scanned by micro-CT and analyzed in terms of BMD and other bone trabecular microstructures. BMD and the other bone trabecular microstructures, such as bone volume, percent bone volume, trabecular separation, and trabecular pattern factor, showed statistically significant differences in both the study and control groups (p ≤ 0.05). There were statistically significant differences between the study and control groups in comparisons of BMD in groups 1, 2, 3, 4 and 5, bone volume and percent bone volume in groups 1 and 3, bone surface and bone surface density in group 6, trabecular separation in group 1, and trabecular number, trabecular pattern factor, and structural model index in group 6. Micro-CT scanning and analysis of BMD and other bone trabecular microstructure parameters for evaluation of vitality aspects of mandible fractures in the PMI has various valuable results that should provide guidance for possible studies in the future.     

Issues of threshold selection when determining the fractal dimension in HRCT slices of lumbar vertebrae

The box counting dimension is a frequently applied tool for the classification of trabecular bone structure. The algorithm requires a binarization of the gray value data, for example that acquired by high resolution CT (HRCT). We recently proposed a method to eliminate bone mineral density (BMD) by applying a linear normalization scheme. Further consideration has shown that full BMD independence has not been achieved, and the structural parameter proposed was therefore difficult to interpret. In this study we present an alternative approach to obtain a structural parameter that is independent of BMD. HRCT volume data was acquired on 21 lumbar vertebrae from five cadavers. In the segmented spongiosa, thresholding was based on different quantiles of the gray value histogram, yielding invariance over linear and non-linear transformations. Thresholding at high gray value levels (80% quantile) shows the highest level of significance when discriminating between osteoporotic and non-osteoporotic cases. As an addition to the measurement of BMD alone, the determination of structural properties allows an improvement of the assessment of the individual fracture risk.     

Trabecular bone structure obtained from multislice spiral computed tomography of the calcaneus predicts osteoporotic vertebral deformities

PURPOSE: To compare multislice computed tomography (MSCT)-derived parameters of the trabecular bone structure of the calcaneus with bone mineral density (BMD) in their ability to differentiate between donors with and without osteoporotic fractures of the spine and to optimize CT scan protocols. METHODS: Forty-two postmortem calcanei (81.2 +/- 10 years) were imaged with a 16-detector row MSCT system using 4 different scan protocols varying spatial resolution (12-24 lp/cm) and radiation dose. Structural parameters of trabecular bone were derived from these images, and BMDs of the calcanei were determined using dual x-ray absorptiometry. Vertebral deformities of the spine were radiographically classified using the Spinal Fracture Index. Diagnostic performance in differentiation between donors with and without vertebral fractures was assessed using receiver operating characteristic (ROC) analysis. RESULTS: There were significant case-control differences for many of the structural parameters measured (P < 0.05). The highest ROC values were found for apparent trabecular thickness using the high-resolution and high-dose protocols. Statistically significant correlations were found between most structure parameters and BMD (up to r = 0.85, P < 0.01). CONCLUSION: Structural parameters of trabecular bone as obtained from high-resolution MSCT images of the calcaneus can be used to differentiate between donors with and without osteoporotic vertebral fractures, using a high-resolution and high-dose CT protocol.     

Fracture Risk (FRISK) Score: Geelong Osteoporosis Study

PURPOSE: To develop and evaluate a fracture risk (FRISK) score based on multiple-site bone mineral density (BMD) measurements and other risk factors, to enable prediction of future fracture occurrence. MATERIALS AND METHODS: All participants gave written informed consent, and the study was approved by the Barwon Health Research and Ethics Advisory Committee. BMD was measured at the femoral neck and spine in two concurrently recruited groups: women 60 years of age or older who had sustained a low-trauma fracture of the hip, spine, humerus or distal forearm during a 2-year ascertainment period (n = 231; mean age, 74 years +/- 7 [standard deviation]) and a population-based random sample of women who had not sustained a fracture during the recruitment period (n = 448; mean age, 72 years +/- 8). Falls in the previous year and the number of self-reported fractures in adult life were recorded. Coefficients of a multiple logistic regression model were used as weightings for a combined model. A longitudinal population-based sample was used to assess the fracture risk equation (n = 600; median age, 74 years; interquartile range, 67-82 years). RESULTS: The FRISK score was obtained from the following equation: 9.304 - 4.735BMD(SP) - 4.530BMD(FN) + 1.127FS + 0.344NPF + 0.037W, where BMD(SP) is spinal BMD (in grams per square centimeter), BMD(FN) is femoral neck BMD, FS is falls score, NPF is number of previous fractures, and W is weight (in kilograms). The FRISK score successfully predicted 75% of fractures 2 years after baseline measurements in subjects in the longitudinal study with 68% specificity. CONCLUSION: This study resulted in the derivation of a fracture risk score that successfully predicted 75% of fractures 2 years after baseline.     

Quantitative computed tomographic evaluation of femoral bone mineral content in renal osteodystrophy compared with radial photon absorptiometry

The computed tomography (CT) numbers of cortical bone at the level of 20 cm (CT20) and of spongiosa in the lateral condyle at the level of 2 cm (CT02) from the distal end of the femur were obtained by a quantitative CT method and compared with the bone mineral density of mostly cortical bone within the radius (BMD) by photon absorptiometry. The study included 47 patients with chronic renal failure not dialyzed or induced to regular hemodialysis within 4 weeks of the study (group 1), 28 patients on regular hemodialysis for more than one month (group 2), and ten healthy volunteers (group 3). The measures of bone mineral content (BMC), namely CT20, CT02, and BMD, were compared in terms of their abilities to distinguish members in the various groups. For group 1 and group 3, the greatest variation in BMC was in the difference in CT02, which was primarily a measurement of the BMC of spongiosa. For groups 1 and 2, the greatest variation was in the difference in BMD, which was primarily a measurement of the BMC of cortex. The reproducibility of CT02 was estimated as almost equal to the difference in CT02 values at intervals of 10 months' duration of hemodialysis. The results indicated that CT02 was a useful measurement for evaluating the progress in the early stage of the renal osteodystrophy, and it is recommended that the bone mineral measurement with this QCT method should be performed once or twice a year.     

CT evaluation of trabecular and cortical bone mineral density of the lumbar spine in patients on hemodialysis

It is difficult to evaluate the severity of bone involvement in patients on maintenance hemodialysis (HD) by the measurement of vertebral bone mineral density (BMD), since many endocrine factors influence bone metabolism, making the value of BMD variable from high to low. It is also difficult to interpret the BMD measured in one ROI (region of interest) since bone density distribution is sometimes very heterogenous. On the other hand QCT method is useful to evaluate the value of trabecular and cortical bone mineral density separately. Vertebral BMD was measured in 138 patients on maintenance HD, by using DEQCT (dual energy QCT). 161 patients without bone metabolic disorders were studied for control group. In patients on HD, various BMD values ranging from high to low were observed, and there was no correlation between BMD value and duration of HD. The number of patients with low mineral content was greater than that with high mineral content in both cortical and trabecular bone. The trabecular BMD decreased with age, and the speed of BMD decline was the same in both sexes. The rapid decrease of trabecular BMD after menopause seen in control female group was not observed in female patients on hemodialysis. The deviation of BMD from the age-matched average BMD value was smaller in older male patients than that in young male and female patients. In order to evaluate the difference of change between the trabecular and cortical bone at the same vertebra, cases in which discrepancy of Z-score was more than 0.2 were divided into three groups; group A: increased trabecular BMD (Z-score greater than 1), group B: decreased trabecular BMD (-1 greater than Z-score), group C: normal trabecular BMD (-1 less than Z-score less than 1), and in each group T/C ratio (Z-score of trabecular BMD/Z-score of cortical BMD ratio) was evaluated. In group A, almost all cases showed trabecular BMD to be higher than cortical, and in group B, 60% cases showed trabecular BMD to be lower than cortical, suggesting that the change of BMD in trabecular bone is greater than that in cortical bone.     

Exercise in youth: High bone mass,large bone size,and low fracture risk in old age

Physical activity is favorable for peak bone mass but if the skeletal benefits remain and influence fracture risk in old age is debated. In a cross‐sectional controlled mixed model design, we compared dual X‐ray absorptiometry‐derived bone mineral density (BMD) and bone size in 193 active and retired male elite soccer players and 280 controls, with duplicate measurements of the same individual done a mean 5 years apart. To evaluate lifetime fractures, we used a retrospective controlled study design in 397 retired male elite soccer players and 1368 controls. Differences in bone traits were evaluated by Student's t‐test and fracture risk assessments by Poisson regression and Cox regression. More than 30 years after retirement from sports, the soccer players had a Z‐score for total body BMD of 0.4 (0.1 to 0.6), leg BMD of 0.5 (0.2 to 0.8), and femoral neck area of 0.3 (0.0 to 0.5). The rate ratio for fracture after career end was 0.6 (0.4 to 0.9) and for any fragility fracture 0.4 (0.2 to 0.9). Exercise‐associated bone trait benefits are found long term after retirement from sports together with a lower fracture risk. This indicates that physical activity in youth could reduce the burden of fragility fractures.     

绝经后妇女腰椎骨密度容积性定量CT测量研究

目的 应用容积性定量CT(vQCT)技术和双能X线吸收测量(DXA)仪测量绝经后妇女腰椎容积性骨密度(BMD),评价2种检查方法区分骨质疏松伴椎体骨折与骨质疏松不伴骨折的差异.方法 选取绝经后妇女118名[平均年龄(62.1±7.0)岁],按照所行胸腰椎X线平片检查结果及腰椎DXA测量的参数[前后位BMD(AP-SPINE)]值分组,>均值-1个标准差(x-1s)为正常组、x-1s～x-2s为骨量减少组、0.05).在骨质疏松组和骨质疏松伴骨折组AP-SPINE仅与3D-CORT间有相关性(R2=0.189,P<0.01);App60 BV/TV%、App80 BV/TV%、App100 BV/TV%、App120 BV/TV%与3D-TRAB或2D-TRAB之有相关性(3D法:R2值分别为0.955、0.951、0.941、0.912;2D法:R2值分别为0.912、0.910、0.878、0.821;P值均<0.01).容积性BMD的测量精确度为0.70%～2.25%.结论 vQCT技术可区分骨质疏松及伴骨质疏松性骨折绝经后妇女骨量,能力高于DXA,其中整体骨BMD诊断严重骨质疏松的效果最好;App BV/TV%可反映骨质疏松者骨小梁丢失程度,预测骨折风险.     

绝经后妇女腰椎骨密度测量的研究

作者对患有或未患腰椎骨折的绝经后妇女的骨密度测量进行了研究分析，旨在比较L－DXA和mL－DXA对骨折诊断的敏感性。材料和方法：共240例绝经后妇女。根据各胸腰椎（胸4至腰4）倒位X线平片所见，并采用目视半定量法判断椎体的骨折或其程度，腰椎骨密度值分别选用L－DXA和mL－DXA所测数据。结果：骨折组的年龄高于非骨折组，而其BMD值则低于非骨折组。分析比较L－DXA和mL—DXA的结果表明其下降百分数和Z分数相似，ROC曲线下面积也无显著性差异，logistic回归分析中，两者年龄调整后的优势比无显著性差异。进一步将正常与轻度骨折组比较，两者的ROC面积仍无显著性差异。结论：在区分正常与骨折以及正常与轻度骨折时，mL－DXA并不优于L－DXA。因轻度骨折的L－DXA和mL－DXA所测骨密度值均低于非骨折组，故应视其为骨折。     

Vertebral morphometry: evaluation of osteoporosis-caused fractures

PURPOSE: To compare visual reading of spine radiographs and quantitative morphometric approach for assessing the prevalence of vertebral fractures in postmenopausal osteoporosis. MATERIAL AND METHODS: In 473 postmenopausal women afferent to our Centre of Osteoporosis under-went lateral thoracic and lumbar spine radiograph to identify vertebral fractures and dual energy X-ray absorptiometry (DXA) to measure bone mineral density (BMD) of the lumbar spine (L1-L4). Osteoporosis was defined according to the World Health Organization (WHO) guidelines. To identify vertebral fractures the radiographs were visually analyzed by two radiologists; a woman was judged as fractured only if both readers independently found at least one vertebral fracture on her films. Then the spine radiographs were digitized by means of a scanner to perform quantitative vertebral morphometry (QVM) using specific software. An expert operator manually located the calipers on the vertebral bodies from T4 to L5 and the computer automatically calculated the anterior, middle and posterior vertebral heights and their ratios. A vertebral fracture was defined by morphometry as a reduction by at least 20%, with an absolute decrease of at least 4 mm, in one of three height ratios of any vertebral body compared to the corresponding reference ratio for fertile women. RESULTS: Visual reading by radiologists detected 9.5% (45/473) women with vertebral fractures and QVM detected 13.7% (65/473) with statistical significance (p < 0.001). In the 75-80 years age group the prevalence of vertebral fractures reaches the maximum value, 26.3% by visual reading and 36.8% by QVM. Among fractured women, 34 were osteoporotic by DXA; 11 women found fractured by visual reading and 21 by QVM were osteopenic women, with bone mineral densities between -1 and -2.5 SD of the T-score. CONCLUSION: This study showed that quantitative assessment of spine radiographs by vertebral morphometry is an objective method that allows to identify a larger number of vertebral fractures compared to visual inspection. This is very important not only for epidemiological studies, but also for clinical use because a previous vertebral fracture increases the risk of subsequent fractures significantly. Therefore, to improve the risk assessment of vertebral fractures for osteoporotic patients it is necessary to combine the use of QVM and BMD.     

Influence of anthropometric parameters and bone size on bone mineral density using volumetric quantitative computed tomography and dual X-ray absorptiometry at the hip

PURPOSE: To evaluate the influence of anthropometric parameters (age, height, and weight) and bone size on bone mineral density (BMD) using volumetric quantitative computed tomography (QCT) and dual X-ray absorptiometry (DXA) in a group of elderly women. MATERIAL AND METHODS: BMD values were obtained with DXA and QCT at the spine and hip in a cohort of 84 elderly women (mean age 73 +/- 6 years). QCT measures included trabecular, integral, and cortical BMD assessed at the hip and spine as well as cross-sectional areas of the mid-vertebrae and proximal femora. Spinal integral and femoral neck BMD measures were well matched to the regions of bone quantified on anteroposterior (AP) spine DXA and the femoral neck region of hip DXA. RESULTS: When QCT parameters were linearly regressed against body height and weight, only the relationships with weight were found to be statistically significant. Except for cortical BMD at the femoral neck, all BMD and geometric parameters measured from both DXA and QCT showed statistically significant associations with body weight (r2 = 0.4, 0.0001 < P < 0.02). The strongest associations with weight were found for DXA Neck (DXA_NECK) and DXA lumbar spine (DXA_LSP) (r2 = 0.4, P < 0.0001). CONCLUSION: The relationship of DXA BMD is stronger than QCT BMD with body weight and it encompasses the response of both bone size and density to increasing body mass.     

Effect of spinal degenerative changes on volumetric bone mineral density of the central skeleton as measured by quantitative computed tomography

Purpose: To evaluate the impact of degenerative changes due to osteoarthritis (OA) at the spine on volumetric bone mineral density (BMD) as measured by volumetric quantitative computed tomography (vQCT).

Material and Methods: Eighty-four elderly women (mean age 73±6 years), comprising 33 with vertebral fractures assessed by radiographs and 51 without vertebral fractures, were studied. Trabecular, cortical, and integral BMD were examined at the spine and hip using a helical CT scanner and were compared to dual X-ray absorptiometry (DXA) measurements at the same sites. OA changes visible on the radiographs were categorized into two grades according to severity. Differences in BMD measures obtained in the two groups of patients defined by OA grade using the described radiologic methods were compared using analysis of variance. Standardized difference (effect sizes) was also compared between radiologic methods.

Results: Spinal trabecular BMD did not differ significantly between OA grade 0 and OA grade 1. Spinal cortical and integral BMD measures showed statistically significant differences, as did the lumbar spine DXA BMD measurement (13%, P = 0.02). The QCT measurements at the hip were also higher in OA 1 subjects. Femoral trabecular BMD was 13-15% higher in OA grade 1 subjects than in OA grade 0 subjects. The cortical BMD measures in the CT_TOT_FEM and CT_TROCH ROI's were also higher in the OA 1 subjects. The integral QCT BMD measures in the hip showed difference between grades OA 1 and 0. The DXA measurements in the neck and trochanter ROI's showed smaller differences (9 and 11%, respectively). There were no statistically significant differences in bone size.

Conclusion: There is no evidence supporting that trabecular BMD measurements by QCT are influenced by OA. Instead, degenerative changes have an effect on both cortical and integral QCT, and on DXA at the lumbar spine and the hip. For subjects with established OA, assessment of BMD by volumetric QCT may be suggested.     

Radiographic bone texture analysis is correlated with 3D microarchitecture in the femoral head,and improves the estimation of the femoral neck fracture risk when combined with bone mineral density

Purpose

Femoral neck fracture is a major public health problem in elderly persons, representing the main source of osteoporosis-related mortality and morbidity. In this study, we aimed at comparing radiographic texture analysis with three-dimensional (3D) microarchitecture in human femurs, and at evaluating whether bone texture analysis improved the assessment of the femoral neck fracture risk other than that obtainable by bone mineral density (BMD).

Materials and methods

Thirteen osteoporotic femoral heads from patients who fractured their femoral neck and twelve non-fractured femoral heads from osteoarthritic patients were studied using respectively (1) a new high-resolution digital X-ray device (BMA™, D3A Medical Systems) allowing for bone texture analysis with fractal parameter Hmean, and (2) a micro-computed tomograph (CT) for 3D microarchitecture. BMD was measured postoperatively by DXA in all patients in the contralateral femur.

Results

In these femoral heads, we found that fractal parameter Hmean was correlated with 3D microarchitecture parameters: bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular separation (Tb.Sp) and fractal dimension (FD) respectively (p < 0.05). Then, fractal parameter Hmean was significantly lower in the femoral heads from the fractured group than from the non-fractured group (p < 0.01). Finally, multiple regression analysis showed that combining bone texture analysis and total hip BMD significantly improved the estimation of the femoral neck fracture risk from adjusted r² = 0.46 to adjusted r² = 0.67 (p < 0.05).

Conclusion

Radiographic bone texture analysis was correlated with 3D microarchitecture parameters in the femoral head, provided accurate discrimination between the femoral heads from the fractured and non-fractured groups, and significantly improved the estimation of the femoral neck fracture risk when combined with BMD.     

In vitro and in vivo spiral CT to determine bone mineral density: initial experience in patients at risk for osteoporosis

PURPOSE: To evaluate, both experimentally and in vivo, if nondedicated standard spiral computed tomography (CT) may be used to obtain reliable bone mineral density (BMD) data. MATERIALS AND METHODS: Twenty lumbar spine specimens from human cadavers were examined with standard quantitative CT and spiral CT. In addition, 50 patients with a history of lymphoma and chemotherapy were examined. These patients underwent long-term follow-up CT to rule out tumor recurrence. Quantitative CT was performed before contrast medium administration to assess potential posttherapeutic osteoporosis. In addition, fracture status of the spine was determined. Mean BMD values and SDs were calculated, and relationships between measurements obtained with quantitative CT and spiral CT were assessed with linear regression analysis and two-tailed tests of significance (t test). A linear fit was used to calculate quantitative CT data from spiral CT values. RESULTS: For the specimens, a coefficient of determination (r(2) = 0.99, P <.001) was found between BMD measurements obtained with quantitative CT and those obtained with spiral CT. Mean BMD in specimens was 63.6 mg/mL +/- 36.6 with quantitative CT and 74.4 mg/mL +/- 38.2 with spiral CT. Mean BMD in patients was 105.0 mg/mL +/- 34.6 with quantitative CT and 139.5 mg/mL +/- 42.7 with contrast medium-enhanced spiral CT. A coefficient of determination (r(2) = 0.91, P <.001) was obtained between these measurements. Mean BMD from L1 through L3 vertebrae was calculated, and spiral CT data were multiplied by 0.77 to yield quantitative CT data. Differences in BMD were significant (P <.05) for patients with (n = 9) and those without fractures (n = 41), as determined with spiral CT and quantitative CT. CONCLUSION: Correlations between BMD data obtained with spiral CT and standard quantitative CT were highly significant. By using a conversion factor, BMD measurements can be determined with routine abdominal spiral CT scans.     

Osteonecrosis diagnosed on MR images of the knee. Relationship to reduced bone mineral density determined by high resolution peripheral quantitative CT

Purpose: 
To evaluate if osteonecrosis diagnosed on MR images of the knee relates to reduced bone mineral density (BMD) and may be caused by an insufficiency fracture. Material and Methods: 
Thirty-two consecutive patients (8 men, 24 women; age range 27-82 years, mean 62 years) with MR findings of osteonecrosis of the femoral or tibial condyle were prospectively included. Trabecular and cortical BMD were measured with high resolution peripheral quantitative CT in the non-dominant distal radius and the tibia of the involved extremity. One tibia was not measured due to posttraumatic deformity. Results: 
The mean trabecular BMD of the radius was 81% of the young-adult average peak BMD (range 19-160%). The mean cortical BMD in the radius was 86% (range 63-108%). The mean trabecular BMD in the tibia was 92% (range 28-160%). The mean cortical BMD in the tibia was 86% (range 49-132%). The values of the trabecular bone of the distal radius (tibia) were normal in 11 (15) patients, osteopenic in 12 (4), and osteoporotic in 9 (12), respectively. The cortical bone values of the distal radius (tibia) were normal in 12 (13) patients, osteopenic in 12 (12), and osteoporotic in 8 (6), respectively. Conclusion: 
Osteoporosis and osteopenia are commonly found in patients with osteonecrosis of the knee as diagnosed on MR images. This indicates that for some patients an insufficiency mechanism may be responsible for the MR findings. However, in the patients with normal bone density other reasons for osteonecrosis may be present.     

Usefulness of assessing bone mineral content of cortical bone in patients with lingering imbalance of bone metabolism

The CT numbers of cortex at the level of 20 cm (CT20) and of spongiosa in the lateral condyle at 2 cm (CT02) proximally from the distal end of the femur, and the bone mineral density of spongiosa in L3 body (BMD), were obtained by QCT. The study included 48 patients with rheumatoid arthritis or chronic renal failure as well as 10 healthy volunteers. The relationships of CT20 vs BMD in the regions above and below a critical value of BMD were quite different from each other. Similar relationships were observed in the plot of CT20 vs CT02. The results indicated that the demineralization of cortex was much less than that of spongiosa while the mineral content of spongiosa kept higher than a critical value, but the demineralization of cortex surpassed that of spongiosa once the mineral content of spongiosa had become lower than the critical value. It is necessary to assess bone mineral content of cortex especially in patients with lingering imbalance of bone metabolism.     

女性髋部骨质疏松性骨折患者股骨近端几何结构对患者骨折危险的影响

目的研究女性髋部骨质疏松性骨折患者股骨近端几何结构对患者骨折危险的影响,以及股骨近端几何结构是否是独立于骨密度之外与髋骨骨折密切相关的危险因素。方法 2013年5月—2016年7月延安市人民医院骨科收治171例65周岁以上髋部骨质疏松性骨折女性患者(试验组,其中股骨颈骨折97例,股骨粗隆间骨折74例),另在同时期门诊收治65周岁以上骨质疏松症女性患者386例(对照组),采用双能X线吸收分析技术(DXA)分析比较这两组患者的骨密度(BMD)差异,并分析股骨近端几何结构与两种髋骨骨折之间的相关性。结果两组的体重、股骨颈横截面积(CSA)、股骨颈长(NL)、股骨颈宽与股骨近端骨密度差异有统计学意义(P0.05)。其中对照组股骨近端骨密度比试验组高(P0.05)。此外,在股骨颈骨折组中,股骨颈横截面积与股骨颈长骨折的比值比(OR)分别降低了1.98和1.72倍,而股骨颈宽骨折的OR增加了1.52倍;在粗隆间骨折组中,股骨颈宽骨折的OR则增加了1.44倍(P0.05),并且这些OR与股骨近端骨密度没有相关性。结论股骨颈宽是除骨密度以外独立的与女性髋骨骨折密切相关的危险因素。