Bone mineral density predicts osteoporotic fractures in elderly men: the MINOS study

Osteoporosis in men is becoming a public health problem in developed countries. Fracture incidence increases with age, and the number of fractures increases because of the ageing of the population. We assessed the predictive value of bone mineral density (BMD) for osteoporotic fractures evaluated prospectively in a large cohort of elderly men and assessed the sensitivity of the T-score =–2 to detect men who will sustain a fracture. Fracture incidence was evaluated for 90 months in 759 men from the MINOS cohort aged 50 and over at baseline. In 74 men, 77 incident vertebral and peripheral fractures occurred. BMD was measured at baseline at the lumbar spine, hip, whole body and distal forearm. The incidence of osteoporotic fractures increased with age and with decreasing body weight. In men with low BMD (T-score <–2), fracture incidence varied from 2.26 to 3.07 fractures per 100 person-years and was 2.1 to 3.6 times higher than in men with normal BMD. After adjustment for age, body weight and height, baseline BMD was 3.7 to 7.9% ( P <0.05–0.0001) lower at all the sites of measurement in men who sustained a fracture. After adjustment for age, weight and prevalent fractures, BMD was predictive of osteoporotic fractures at all the sites. Odds ratios varied from 1.28 to 1.89 per 1 SD decrease in BMD ( P <0.05–0.0001). The predictive accuracy of BMD for fractures (area under the curve of the receiving operator characteristics adjusted for age, weight and prevalent fractures) varied from 0.643 to 0.712 according to the skeletal site and was higher for the whole body than for other sites. Thus, BMD itself has a limited value for determining men at an increased risk for fracture. The percentage of incident fractures occurring in men with low BMD (T-score <–2) ranged from 13.7% at the trochanter to 44.6% at the ultradistal radius. Conversely, 27 to 45% of incident fractures occurred in men with mildly decreased BMD (T-score between –1 and –2). In conclusion, BMD predicts osteoporotic fractures in men independently of age, body weight and prevalent fractures. However, the sensitivity of BMD to detect men at high risk of fracture is low. More studies on the predictors of fractures in men, such as bone architecture, morphology, biochemical markers of bone turnover and hormonal levels, are necessary.     

TBS在监测及诊断骨质疏松方面的应用价值

利用DXA（dual energy X-ray absorptiometry,双能X线吸收法）测得的单位面积骨密度值（areal bone mineral density,BMD）是诊断骨质疏松的金标准。骨质疏松患者骨量减少的同时通常存在骨微结构的退化,表现为骨小梁数量减少、间距增加以及骨小梁间连接性下降,而BMD仅能显示骨量的变化,不能提供关于骨结构的信息。因此,仅靠BMD来诊断或排除骨质疏松是不全面的。骨小梁分数（trabecular bone score,TBS）是一种可由DXA图像获得的反映图像上灰阶变化的结构参数,能有效评估骨的微结构、描述骨的质量。本文将从TBS的检测方法、与其他检测骨折风险指标之间的关系以及TBS的有效性和不足等方面来介绍TBS在监测及诊断骨质疏松方面的应用价值。     

绝经后女性股骨近端骨密度与骨质疏松性骨折相关性研究

目的：研究绝经后女性股骨近端骨密度的变化规律与骨质疏松症、骨质疏松性骨折间的关系。方法采用法国Medlink公司Osteocore 3型双能X线骨密度仪,对本地区417例绝经后女性股骨颈、大转子、粗隆间、全髋进行骨密度测定。结果骨折组各年龄段、各部位的BMD均比非骨折组低（ P＜0．05）。随着年龄的增长,股骨近端骨量逐渐丢失,除了45～50组,其余各年龄段骨折组的患病率明显高于非骨折组（ P＜0．05）,骨密度值越低,骨折危险性越大。结论绝经后女性股骨近端骨密度与发生骨质疏松性骨折的风险呈明显负相关性,应该注意预防。     

骨密度对骨质疏松性骨折的判断价值

目的研究骨密度对骨质疏松性骨折的判断价值。方法共3组研究对象,398例骨质疏松不伴有骨折的研究对象(A组),胸腰椎骨折患者(B组),骨密度正常的正常组进行研究。研究骨密度的一般情况、不同T值在各组的分配情况,骨质疏松性骨折与骨密度(BMD)的相关性。结果腰椎L2-L4、L2-L4和股颈的BMD值之间,T值人数分配之间,正常组、A组以及B组的差别具有统计学意义(P<0.05)。腰椎L1-L4、L2-L4和股颈的BMD以及总BMD的测定值均与骨质疏松性骨折相关。结论我们认为:本地区所收治的骨质疏松性骨折患者,全部应诊断判定为骨质疏松症。     

The relationship between bone mineral density and ultrasound in postmenopausal and osteoporotic women

The aim of this cross-sectional study was to use a novel method of data analysis to demonstrate that patients with osteoporosis have significantly lower ultrasound results in the heel after correcting for the effect of bone mineral density (BMD) measured in the spine or hip. Three groups of patients were studied: healthy early postmenopausal women, within 3 years of the menopause (n=104, 50%), healthy late postmenopausal women, more than 10 years from the menopause (n=75, 36%), and a group of women with osteoporosis as defined by WHO criteria (n=30, 14%). Broadband ultrasound attenuation (BUA), speed of sound (SOS) and Stiffness were measured using a Lunar Achilles heel machine, and BMD of the lumbar spine and left hip was measured using dual-energy X-ray absorptiometry (DXA). SOS, BUA and Stiffness were regressed against lumbar spine BMD and femoral BMD for all three groups combined. The correlation coefficients were in the range 0.52–0.58, in agreement with previously published work. Using a calculated ratio R, analysis of variance demonstrated that the ratio was significantly higher in the osteoporotic group compared with the other two groups. This implied that heel ultrasound values are proportionately lower in the osteoporotic group compared with the other two groups for an equivalent value of lumbar spine and femoral neck BMD. We conclude that postmenopausal bone loss is not associated with different ultasound values once lumbar spine or femoral neck BMD is taken into account. Ultrasound does not give additional information about patterns of bone loss in postmenopausal patients but is important in those patients with osteoporosis and fractures.     

绝经后女性骨质疏松性椎体骨折与腰椎体骨密度的相关性

随着我国步入老龄化社会,骨质疏松症的患病率明显升高。骨质疏松症最严重的危害来自骨质疏松性骨折,绝经后女性尤其多见。由于脊柱独特的解剖学和生物力学特点,骨质疏松患者更易发生椎体骨折。骨密度测量是诊断骨质疏松的金标准。本文通过回顾近年来相关文献,探讨腰椎体骨密度检测对绝经后女性骨质疏松性椎体骨折的意义,发现:绝经后骨质疏松性椎体骨折患者的BMD水平比绝经后骨质疏松症但无脊椎骨折者明显减少;绝经后骨质疏松症患者的BMD水平越低,其发生椎体骨折的风险越高;有椎体骨折史的绝经后骨质疏松症患者的BMD水平与发生再次椎体骨折的风险呈负相关。药物干预通常可明显提高绝经后骨质疏松症患者的BMD水平,同时还可减少椎体骨折的发生。尚存在一些不足:腰椎骨密度可能出现假性增高;需进一步探讨预测骨质疏松性椎体骨折的骨密度阈值;药物干预的研究中BMD水平与椎体骨折发生的相关性并没有得到深入研究;缺少大规模的绝经后骨质疏松性椎体骨折的流行病学,现有研究也大都存在病例收集方法不规范、样本量小、年龄分布存在差异等不足。对绝经后骨质疏松性椎体骨折的深入研究需要多学科共同协作。     

骨质疏松性骨折与骨密度关系的研究进展

骨质疏松症是老年人的常见病和多发病,其最大的危害是导致骨折的发生。随着老年人口的增加,骨质疏松性骨折的发病率也显著增高,这已经引起了医学研究者的普遍关注。近年来对运用骨密度检测来预测骨质疏松性骨折的研究很多,但是还没有形成一个定论,故对运用骨密度检测来预测骨质疏松性骨折的研究现状作一简单综述。     

绝经后女性骨质疏松合并骨折血清25羟维生素D水平研究

目的 探讨绝经后女性骨质疏松合并骨折血清25羟维生素D的水平.方法 选择2010年1月-2013年5月在解放军第309医院骨内科住院的86例患者,包括绝经后骨质疏松合并骨折患者42例,年龄(70.38±6.11)岁,不伴骨折绝经后骨质疏松患者44例,年龄(67.32±8.93)岁.采用美国Norland双光能X线骨密度检测仪对所有患者进行腰椎L2-L4和左侧股骨近端(包括Neck、Troch、Ward''s三角区)骨密度测量,并测定身高、体重、血谷丙转氨酶(ALT)、谷草转氨酶(AST)、肌酐(CRE)、尿素氮(BUN).采用酶联免疫吸附法测定两组患者血清25羟维生素D,比较两组25羟维生素D水平.结果 绝经后骨质疏松合并骨折组患者血清25羟维生素D(12.40±3.7) ng/ml,较绝经后非骨折骨质疏松患者(16.23 ±4.6)ng/ml低,差异具有统计学意义(P＜0.05);绝经后骨质疏松合并骨折组患者ALT(18.22±8.17) IU/L、AST(20.70±12.67) IU/L、CRE(56.76±11.81)umol/L、BUN(5.20±1.40) mmol/L与骨质疏松组ALT(21.32±12.16)IU/L、AST(22.16±8.36) IU/L、CRE(57.29±13.42) umol/L、BUN(5.2±1.8) mmol/L相比,差异无统计学意义(P＞0.05);绝经后骨质疏松合并骨折患者L2-4、Neck、Troch、Ward''s三角区的骨密度分别为(0.75 ±0.19) g/cm2、(0.61 ±0.18)g/cm2、(0.50±0.12) g/cm2、(0.40±0.14)g/cm2与对照组(0.81 ±0.33) g/cm2、(0.67 ±0.11)g/cm2、(0.52±0.10) g/cm2、(0.45±0.1)g/cm2相比较,差异没有统计学意义(P＞0.05).结论 绝经后骨质疏松合并骨折患者较未合并骨折骨质疏松维生素D缺乏更严重.     

漯河地区中老年骨质疏松性骨折与股骨近端骨密度相关性研究

目的 调查漯河地区中老年骨密度(BMD)的变化规律和骨折之间的关系。方法 采用法国Medlink公司的的双能X线骨密度仪对漯河地区649名中老年人进行健侧髋部股骨颈、大转子、粗隆间和全髋的骨密度值测量。结果 骨折组各年龄段、各部位的BMD均比非骨折组低（P<0.05）。随着年龄的增长股骨近端骨量逐渐丢失,除了45~组,其余区域各年龄段骨折组的患病率明显高于非骨折组(P<0.05),骨密度值越低,骨折危险性越大。结论 中老年人骨近端骨密度值与发生骨质疏松性骨折之间存在密切关系,不容忽视。     

Usefulness of Trabecular Bone Score (TBS) to Identify Bone Fragility in Patients with Primary Hyperparathyroidism

Background: Patients with primary hyperparathyroidism usually show decreased bone strength that are often not well diagnosed by conventional Dual-energy X-ray absorptiometry (DXA). Trabecular Bone Score (TBS) is a new technique for assessing bone microarchitecture indirectly. This cross-sectional study evaluates the usefulness of TBS in patients with primary hyperparathyroidism in clinical practice. Methodology: Bone mineral density (BMD) by DXA and TBS values by TBS InSight® software were determined in 72 patients with primary hyperparathyroidism to analyze its relationship with fragility fractures. A receiver operating curve was performed to evaluate the usefulness of TBS as predictor of fragility fractures. FRAX index with and without adjustment by TBS was calculated. Additionally, longitudinal data of a subgroup of patients according to the therapeutic management were also evaluated. Results: A total of 51.4% of the patients showed degraded microarchitecture while only 37.5% of them were diagnosed of osteoporosis by DXA. No significant correlation was found between TBS values and BMD parameters. However, TBS values were lower in osteoporotic patients compared to those classified as normal by BMD (1.16 ± 0.12vs 1.26 ± 0.17; p?=?0.043) and in patients with fragility fractures compared to nonfractured patients (1.19 ± 0.03vs 1.24 ± 0.02, p < 0.001). The area under the curve for TBS performed better than the combination of femoral, hip and spine-BMD for prevalent fractures (0.714vs 0.679). TBS-adjusted FRAX was higher than nonadjusted model for both major osteoporotic and hip fracture (4.5% vs 3%; 0.9% vs 0.7%; p < 0.001). At follow-up, an improvement in TBS values was observed in treated patients (medical or surgical) vs nontreated close to significance (1.27 ± 0.10vs 1.24 ± 0.11, p?=?0.074). Conclusions: TBS could be a useful tool to identify increased fracture risk in patients with primary hyperparathyroidism underdiagnosed by BMD. Moreover, FRAX adjusted by TBS could be a more robust tool for predicting the risk of osteoporotic fracture to help in therapeutic decisions in this population.     

TBS as a Tool to Differentiate the Impact of Antiresorptives onCortical and Trabecular Bone in Children With OsteogenesisImperfecta

Introduction/Background: Osteogenesis imperfecta is a hereditary connective tissue disorder, resulting in low bone mass and high bone fragility. Dual-energy X-ray absorptiometry (DXA) and in adulthood also the trabecular bone score (TBS) are well established to assess bone health and fracture risk. The purpose of this investigation was to assess the usefulness of TBS in respect to different treatment regimes in children with osteogenesis imperfecta. Changes of areal bone mineral density (aBMD) and TBS using DXA scans of children treated with antiresorptive therapies were evaluated. Methodology: DXA scans (aBMD, TBS) of 8 children with OI were evaluated. The scans were taken during a 1 yr period of treatment with bisphosphonates and during 1 yr pilot trial using denosumab. Changes of aBMD and TBS during both treatment regimens were compared. Results: During bisphosphonate treatment aBMD increased about 6.2%, while TBS increased about 2.1%. The difference between aBMD and TBS before and after bisphosphonate treatment was not significant (p?=?0.25). During denosumab treatment aBMD increased around 25.1%, while TBS increased 6.7%. The change of aBMD was significant (p?=?0.007), as was the difference between aBMD and TBS (p < 0.001). Conclusions: Denosumab had a significant effect on both aBMD and TBS but was significantly more pronounced in aBMD. These results suggest a stronger effect of denosumab on cortical bone and the growth plate in comparison to bisphosphonates. Beside the lack of paediatric reference data and the small sample size, the results suggest TBS to be a useful tool for monitoring skeletal changes during development, growth, and antiresorptive therapy in children with OI.     

绝经后妇女骨质疏松性椎体骨折与腰椎骨密度的关系

目的探讨绝经后妇女骨质疏松性椎体骨折与腰椎骨密度的关系。方法选择骨质疏松性椎体骨折的绝经后妇女23例为骨折组,无椎体骨折的25例绝经后骨质疏松妇女为对照组。两组的年龄、绝经年限、身高、体重、体重指数差异无显著性,均行胸腰椎正侧位X线摄片。用双能X线吸收仪（DXA）测量的腰椎（L2-4）前后位骨密度（BMD）、骨矿含量（BMC）和T值。结果骨折组BMD、BMC和T值均低于对照组（P〈0.01）。结论腰椎BMD降低与绝经后妇女的骨质疏松性椎体骨折相关。绝经后骨质疏松妇女应重视BMD变化,预防椎体骨折的发生。     

Comparison of the radiographic vertebral trabecular pattern with the vertebral fracture prevalence and spinal bone density

Spinal bone densitometry allows accurate and precise measurement of the severity of bone loss. Where densitometry is not yet available medical practitioners have to continue to rely on clinical radiography. Since the grey levels of the radiographic image are highly inaccurate we studied the radiographic vertebral trabecular pattern for its suitability as a semiquantitative assessment of vertebral bone loss. We defined four vertebral trabecular pattern indices (VTPI 4=normal, VTPI 1=severe bone loss) and tested these for correlations with the prevalence of vertebral fractures, and with spinal and hip bone mineral density measured by dual-energy X-ray absorptiometry (DXA). We found negative correlations between VTPI and the percentage of patients with vertebral fractures (p=0.0001), between VTPI and the number of vertebral fractures per patient (r=0.606,p=0.001) and between VTPI and the severity of vertebral fractures, and a positive correlation between VTPI and spinal (r ²=0.556,p=0.0001) and hip DXA values (r ²=0.315,p=0.0001). We conclude that the vertebral trabecular pattern index can be used to assess the severity of spinal bone loss when a bone densitometer is not available.     

Factors associated with trabecular bone score in postmenopausal women with type 2 diabetes and normal bone mineral density

BACKGROUNDOsteoporosis and type 2 diabetes (T2D) have been recognized as a widespread comorbidity leading to excess mortality and an enormous healthcare burden. In T2D, bone mineral density (BMD) may underestimate the risk of low-energy fractures as bone quality is reduced. It was hypothesized that a decrease in the trabecular bone score (TBS), a parameter assessing bone microarchitecture, may be an early marker of impaired bone health in women with T2D.AIMTo identify clinical and body composition parameters that affect TBS in postmenopausal women with T2D and normal BMD.METHODSA non-interventional cross-sectional comparative study was conducted. Potentially eligible subjects were screened at tertiary referral center. Postmenopausal women with T2D, aged 50-75 years, with no established risk factors for secondary osteoporosis, were included. BMD, TBS and body composition parameters were assessed by dual-energy X-ray absorptiometry. In women with normal BMD, a wide range of anthropometric, general and diabetes-related clinical and laboratory parameters were evaluated as risk factors for TBS decrease using univariate and multivariate regression analysis and analysis of receiver operating characteristic (ROC) curves.RESULTSThree hundred twelve women were initially screened, 176 of them met the inclusion criteria and underwent dual X-ray absorptiometry. Those with reduced BMD were subsequently excluded; 96 women with normal BMD were included in final analysis. Among them, 43 women (44.8%) showed decreased TBS values (≤ 1.31). Women with TBS ≤ 1.31 were taller and had a lower body mass index (BMI) when compared to those with normal TBS (Р = 0.008 and P = 0.007 respectively). No significant differences in HbA1c, renal function, calcium, phosphorus, alkaline phosphatase, PTH and 25(ОН)D levels were found. In a model of multivariate linear regression analysis, TBS was positively associated with gynoid fat mass, whereas the height and androgen fat mass were associated negatively (all P < 0.001). In a multiple logistic regression, TBS ≤ 1.31 was associated with lower gynoid fat mass (adjusted odd ratio [OR], 0.9, 95% confidence interval [CI], 0.85-0.94, P < 0.001), higher android fat mass (adjusted OR, 1.13, 95%CI, 1.03-1.24, P = 0.008) and height (adjusted OR, 1.13, 95%CI, 1.05-1.20, P < 0.001). In ROC-curve analysis, height ≥ 162.5 cm (P = 0.04), body mass index ≤ 33.85 kg/m² (P = 0.002), gynoid fat mass ≤ 5.41 kg (P = 0.03) and android/gynoid fat mass ratio ≥ 1.145 (P < 0.001) were identified as the risk factors for TBS reduction.CONCLUSIONIn postmenopausal women with T2D and normal BMD, greater height and central adiposity are associated with impaired bone microarchitecture.     

骨转换标志物与骨密度预测老年女性骨质疏松性骨折的对比研究

目的探讨骨密度与骨转换标志物(bone turnover markers,BTMs)在老年女性骨质疏松患者中的检测意义,对比两者对骨质疏松性骨折(osteoporotic fracture,OF)的预测能力。方法收集2017年10月至2019年2月于成都医学院第一附属医院骨科住院的OF患者96例和骨质疏松患者107例,分为骨折组和非骨折组。通过双能X线吸收仪(DXA)测定骨密度,电化学发光检测BTMs:I型前胶原N端前肽(PINP)、I型胶原β-异构化C末端肽(β-CTX)、骨钙素N端分子片段(N-MID),同时测定骨代谢相关指标:碱性磷酸酶(alkaline phosphatase,ALP)、钙(Ca)、磷(P),t检验对比两组间的计量资料,采用二分类Logistic回归分析骨密度和BTMs与OF的相关性。结果骨折组的骨密度低于非骨折组,差异有统计学意义(P 0. 05);PINP、β-CTX高于非骨折组,70～90岁患者N-MID低于非骨折组,差异均有统计学意义(P0. 05);而ALP、P、Ca在两组之间相比,差异无统计学意义(P0. 05)。二分类Logistic回归分析提示腰椎及髋部骨密度、β-CTX与OF具有显著相关性,OR分别为-4. 182、-6. 929和7. 572,差异均有统计学意义(P0. 05)。PINP、N-MID与OF呈正相关,OR分别为4. 213和2. 510,差异均无统计学意义(P0. 05)。结论低骨密度、高β-CTX的骨质疏松老年女性更容易发生OF,β-CTX比骨密度预测OF的能力更强,可适时对高危人群进行相关干预管理。     

Physical training preserves bone mineral density in postmenopausal women with forearm fractures and low bone mineral density

Summary One hundred and twelve postmenopausal women with low bone mineral density (BMD) and forearm fractures were randomized to physical training or control group. After one year the total hip BMD was significantly higher in the women in the physical training group. The results indicate a positive effect of physical training on BMD in postmenopausal women with low BMD. Introduction The fivefold increase in hip fracture incidence since 1950 in Sweden may partially be due to an increasingly sedentary lifestyle. Our hypothesis was that physical training can prevent bone loss in postmenopausal women. Methods One hundred and twelve postmenopausal women 45 to 65 years with forearm fractures and T-scores from −1.0 to −3.0 were randomized to either a physical training or control group. Training included three fast 30-minute walks and two sessions of one-hour training per week. Bone mineral density (BMD) was measured in the hip and the lumbar spine at baseline and after one year. Results A per protocol analysis was performed, including 48 subjects in the training group and 44 subjects in the control group. The total hip BMD increased in the training group +0.005 g/cm2 (±0.018), +0.58%, while it decreased −0.003 g/cm2 (±0.019), −0.36%, (p = 0.041) in the control group. No significant effects of physical training were seen in the lumbar spine. A sensitivity intention to treat analysis, including all randomized subjects, showed no significant effect of physical training on BMD at any site. Conclusions The results indicate a small but positive effect of physical exercise on hip BMD in postmenopausal women with low BMD.     

腰椎间盘突出对绝经后妇女骨密度的影响分析

目的探讨腰椎间盘突出对绝经后妇女骨密度的影响。方法随机选择绝经后妇女进行问卷调查,内容包括身高、体重、是否有腰椎间盘突出、生活习惯、健康状况等;用双能X线骨密度仪测定腰椎、髋部骨密度,并利用SPSS 20.0统计软件对数据进行分析。结果共筛选入组582例,腰椎间盘突出组133例、腰椎间盘无突出组449例。对各因素与骨质疏松的相关性分析,腰椎间盘突出与腰椎椎体骨密度具有负相关(r=-0.094,P=0.023);两组一般资料比较,日光照射、腰椎骨密度差异比较有统计学意义(P0.05);协方差分析,腰椎间盘无突出组腰椎骨密度(0.734±0.123)g/cm~2明显高于腰椎间盘突出组腰椎骨密度(0.707±0.123)g/cm~2,差异有统计学意义(F=3.968,P=0.047),髋部骨密度差异无统计学意义(P0.05);两组骨质疏松患病率比较,腰椎间盘突出组为55.6%,腰椎间盘无突出组为43.7%,两组比较差异有统计学意义(P=0.015)。结论腰椎间盘突出能够引起腰椎骨量流失,是引起骨质疏松发生的影响因素。     

颈动脉内膜中层厚度和绝经后妇女骨密度相关性研究

目的探讨绝经后骨质疏松症患者颈动脉内膜中层厚度(CIMT)的差异及CIMT和斑块增大的风险。方法进行横断面研究,包括60位绝经后骨质疏松症妇女和60位非骨质疏松症绝经后妇女。CIMT采用B型超声测量。结果绝经后骨质疏松症妇女与无骨质疏松症妇女的平均CIMT差异无统计学意义(P 0.05)。骨质疏松症组CIMT升高的风险与非骨质疏松症组相似。骨质疏松症妇女斑块出现的风险是正常人的三倍。然而,调整了易使妇女患有心血管疾病的年龄和基础疾病后,两组之间斑块的存在并无显着差异(校正比值比=0.85;95%可信区间0.10～6.464)。结论绝经后妇女与无骨质疏松症患者的平均CIMT无差异。绝经后骨质疏松症女性的CIMT升高风险与无骨质疏松症的绝经后妇女相当。两组之间斑块的存在没有显着差异。     

骨转换指标和骨密度监测治疗骨质疏松及其与骨折的关系

骨转换指标和骨密度(BMD)对监测治疗骨质疏松及预测骨折的风险具有重要的临床意义。本文扼要综述了骨转换指标和BMD在治疗骨质疏松中的监测频率和最小显著变化(LSC),以及两者与骨折风险的关系,它对于指导临床监测治疗骨质疏松具有重要价值。