体重体成分与骨密度的关系

为了研究体成分与骨密度（ＢＭＤ）之间的关系，因体重与ＢＭＤ显著相关，体成分各个组成相加等于体重，而体成分与ＢＭＤ的关系仍不清楚。方法随机选取２０６名１６～５２岁健康的男女性汉族人，用双能Ｘ射线吸收法（ＤＸＡ）测量ＢＭＤ与体成分，进行ＢＭＤ与体重，体成分的多元线性回归分析。结果体重，瘦组织（ＬＴＭ）与男女性的ＢＭＤ显著正相关，脂肪组织（ＦＴＭ）仅对女性全身，腰椎ＢＭＤ起显著性作用。结论影响男女性ＢＭＤ的体成分中，ＬＴＭ是主要因素，ＦＴＭ仅对女性ＢＭＤ有影响。本文较全面地研究了体成分与ＢＭＤ的关系。     

乌鲁木齐地区2711例骨密度调查研究

目的了解新疆乌鲁木齐地区正常汉族人群骨密度(BMD)的变化规律和骨质疏松症(OP) 的患病率。方法应用法国DMS公司生产的CHALLENGER型双能X线骨密度仪对乌鲁木齐地区汉族人群共2711名20～80岁居民进行腰椎2～4及股骨近端的骨密度测定。结果乌鲁木齐地区汉族人群男性、女性的腰椎及股骨近端的BMD峰值均出现在20～29岁年龄组,峰值后随着年龄的增长,而骨密度BMD降低,女性在50～59岁明显加速下降,男性没有加速下降现象。乌鲁木齐地区40岁以后OP患病率男性28．3％,女性OP患病率45．2％。男女性50～59岁以上,组间患病率有显著差异(P<0．05)。结论通过对乌鲁木齐地区汉族人群的骨密度变化规律及患病率研究, 为乌鲁木齐地区汉族人群的骨质疏松症诊断及治疗提供客观有效的依据。     

腰椎旋转角度对骨密度测量值影响的定量研究

目的定量分析腰椎旋转角度对双能X线法(Dual-energy X-ray absorptiometry,DXA)测量腰椎骨密度值(Bone mineral density,BMD)的影响,并提出校正方法。方法模拟腰椎BMD标准测量方法,将5具成年男性腰椎标本放于特制的可旋转模具上。以5°为增加量,将标本从0°(标准前后位)逐渐旋转至45°,测量不同旋转角度状态下的腰椎BMD。同时,对标本进行X线摄片,根据Nash-Moe法评估椎体的旋转程度,并与DXA获得的图像进行比较。结果随着腰椎旋转角度增加,腰椎的投射面积逐渐增加,骨矿含量无显著性变化,骨密度值逐渐降低。相关性分析表明,腰椎旋转角度与投射面积呈正性相关,与BMD呈负性相关。当旋转度数至15°时,测量BMD值与0°值之间有显著性差异(P=0.001)。当旋转至45°时,BMD降低达21%。根据Nash-Moe法判断腰椎旋转程度,DXA法与X线法的符合率为90%。结论椎体旋转角度对腰椎骨密度值具有显著性影响,可以导致测量值较真实值偏低。对于存在腰椎旋转畸形患者,应当根据旋转角度校正骨密度,以避免过高估计患者骨质疏松严重程度。     

Vertebral bone mineral density measured laterally by dual-energy X-ray absorptiometry

The bone mineral density (BMD) of lumbar vertebrae in the anteroposterior (AP) view may be overestimated in osteoarthritis or with aortic calcification, which are common in elderly. Furthermore, the risk of spinal crush fracture should be more closely related inversely to the BMD of the vertebral body than to that of the posterior arch. Therefore, we measured BMD of lumbar vertebrae in lateral (LAT) view (L2–L3), using a standard dual-energy X-ray absorptiometer (DEXA), thus eliminating most of the posterior spinal elements. The precision of BMD LAT measurement was determined both in vitro and in healthy volunteers. Then, we compared the capability of BMD LAT and BMD AP scans for monitoring bone loss related to age and for discriminating the BMD of postmenopausal women with nontraumatic vertebral fractures from that of young subjects. In vitro, when a spine phantom was placed in lateral position in the middle of 26 cm of water in order to simulate both soft-tissue thickness and X-ray source remoteness, the coefficient of variation (CV) of six repeated determinations of BMD was 1.0%. In vivo, the CV of paired BMD LAT measurements obtained in 20 healthy volunteers after repositioning was 2.8%. The age-related difference between a peak bone mass group estimated in a group of 27 healthy women aged 20 to 35 years and a group of 50 women aged 60 to 75 years, in whom neither vertebral fracture nor osteoporosis risk factors could be detected, were 21.7% and 37.6% in AP and LAT view, respectively. An arbitrary BMD fracture threshold was defined in AP and LAT views as the 90th percentile of the BMD value of a group of 22 osteoporotic women with vertebral fractures. The distribution of BMD AP and LAT above and below this threshold in 169 consecutively screened women without vertebral fracture was then analysed. In both AP and LAT views, 39.1% and 31.3% had BMD values above and below this threshold, respectively. Of the remaining, 16.0% had a BMD below this threshold only in AP and 13.6% only in LAT view. Thus, if BMD LAT was a better reflection of vertebral body bone mass than BMD AP, and thereby a better predictor of the resistance to crush fracture, our results would suggest that only the use of the standard AP view could under- or overestimate spinal fracture risk in about 30% of women screened for osteoporosis. In conclusion, our results indicate that BMD measurement in lateral view is feasible with a standard DEXA instrument. This mode of scanning, besides overcoming artefacts due to osteoarthritis of the posterior arch and aortic calcifications, appears to provide a greater sensitivity for assessing bone mass loss of the vertebral body than the standard anteroposterior scan.     

Characteristics of bone mineral density and soft tissue composition of obese Japanese women: Application of dual-energy X-ray absorptiometry

We studied the characteristics of bone mineral density (BMD) and soft tissue composition in obese Japanese women using dual-energy X-ray absorptiometry. Eighty-nine women, aged 45–85 years, were divided into three groups according to their body mass index (BMI): a thin group (n = 38; BMI < 21), a standard weight group (n = 31; BMI, 21–25), and an obese group (n = 20; BMI ≥ 25). The mean BMD of the second to fourth lumbar vertebrae and BMD of the lumbar spine, thoracic spine, pelvis, legs, and ribs of the thin group were significantly lower than those of the standard weight group or the obese group (P < 0.05), whereas no significant difference in total body BMD was observed among the three groups. There was a significant difference in total and regional fat mass among the three groups (P < 0.05). Lean mass of legs and total lean mass showed a significant difference between the thin group and the obese group (P < 0.05). The results showed that obesity was associated with higher BMD of weight bearing-bones and ribs, high total and regional fat mass, and high lean mass of bilateral legs and total lean mass. We suggest that obesity may contribute to the prevention of bone loss of weight-bearing bones and ribs and muscular atrophy of the legs. Received: Sept. 30, 1998 / Accepted: Dec. 10, 1998     

人体双髋骨密度分布规律研究

目的 探索人体双髋骨密度(bone mineral density,BMD)的分布规律,为选择髋部感兴趣区提供依据.方法 用GE Lunar Prodigy型双能X线骨密度仪(dual-energy X-ray absorptiometry,DXA)测量受检者双髋BMD,感兴趣区选择股骨颈和全髋部.结果 共检测301例,其中男性135例,左右侧股骨颈BMD差值为(0.004±0.048)g/cm~2,左右侧全髋部BMD差值为(0.006±0.042)g/cm~2,差异均无统计学意义;高低侧股骨颈BMD差值为(0.038±0.029)g/cm~2[95%CI(0.034,0.043)],高低侧全髋部BMD差值为(0.035±0.025)g/cm~2[95%CI(0.030,0.039)].女性166例,左右侧股骨颈BMD差值为(0.006±0.040)g/cm~2,左右侧全髋部BMD差值为(0.003±0.036)g/cm~2,差异均无统计学意义;高低侧股骨颈BMD差值为(0.032±0.025)g/cm~2[95%CI(0.028,0.036)],高低侧全髋部BMD差值为(0.030±0.021)g/cm~2[95%CI(0.027,0.033)].无论男性还是女性,髋部股骨颈BMD与全髋部BMD呈正相关.结论 人体左右侧髋部感兴趣区BMD总体分布基本一致,但个体髋部存在优势侧与非优势侧,建议测量双侧髋部BMD,并报告较低的一侧.     

股骨近端骨密度的测量

双能X线骨密度仪检测骨密度是诊断骨质疏松症和疗效随访的金标准,特别是髋部骨密度的测量对于骨折的预测尤其测定部位本身骨折的预测作用较大.由于脊柱部位的骨密度测量值易受到脊柱退行性疾病的病理改变如退行性侧凸、骨赘增生、腰椎间盘突出等影响,测量的准确性下降.因而近年来欧美国家临床试验也好或者骨质疏松诊疗也好,大都以股骨近端的BMD测定为标准.本文就股骨近端解剖特点、骨密度测量的意义、方法以及测量的注意点作一个综述,以期帮助临床医生或技术员全面评估股骨近端骨密度测定的意义.     

老年男性2型糖尿病患者骨密度变化的分析

目的:探讨老年男性2型糖尿病患者骨密度的变化情况.方法:应用双能X线骨密度测定法测定52例老年男性2型糖尿病患者腰椎和股骨颈的骨密度,同时检测身高,体重,血钙、磷、碱性磷酸酶,24 h尿钙,计算体质指数,并与46例同龄正常健康老年男性进行比较.结果:老年男性2型糖尿病患者骨质疏松症的患病率为11.5%,正常对照组骨质疏松的患病率为3.8%.两组间体质指数,血钙、磷及碱性磷酸酶无明显差异,但糖尿病组24 h尿钙高于正常对照组,差异具有显著性(P＜0.01).结论:老年男性2型糖尿病患者的骨质疏松患病率较正常男性明显增高,是2型糖尿病的常见并发症.     

体成分对男性2型糖尿病患者骨密度的影响

目的 应用双能X线骨密度仪（DXA）探讨体成分对男性2型糖尿病患者骨密度的影响。方法 选择年龄50～60岁在我科住院的男性2型糖尿病患者107例,分为正常体重组、超重组和肥胖组,分别测定其身高、体重,计算体重指数（BMI）,利用全自动生化分析仪测定血糖、血脂,高压液相色谱法测定糖化血红蛋白（HbA1c）,采用双能Ｘ线骨密度仪测定腰椎、左股骨大转子骨密度（BMD）及体成分,并进行统计学分析。结果 3组男性2型糖尿病患者腰椎BMD分别为1.12±0.05,1.21±0.07,1.36±0.09,左股骨大转子BMD分别1.12±0.06,1.22±0.08,1.41±0.08,与骨密度呈正相关;全身各部位肌肉含量与骨密度成正相关,且大腿＞上肢＞躯干;不同部位脂肪含量对骨密度的影响是不同的,其中上肢脂肪和大腿脂肪与骨密度成正相关,而躯干脂肪与骨密度成负相关;年龄、糖化血红蛋白、血脂对男性2型糖尿病患者骨密度无明显影响,而体重指数、肌肉含量及脂肪含量影响明显。结论 体重指数、肌肉含量和脂肪含量对男性2型糖尿病患者骨密度有直接影响。男性2型糖尿病患者加强锻炼,减少腹部脂肪含量,增加四肢肌肉含量,可以预防骨质疏松症的发生。     

Failure load of thoracic vertebrae correlates with lumbar bone mineral density measured by DXA

Fractures of the thoracic spine account for a large portion of vertebral fractures in the elderly, yet noninvasive measurements of bone mineral properties are limited to the L2–L4 vertebral bodies. The purpose of this investigation was to determine whether bone mineral properties of the umbar spine correlate with the failure properties of thoracic ertebrae. Cadaveric lumbar segments were scanned using dual-energy x-ray absorptiometry (DXA) from both the latcrol and anteroposterior projections. Three-body segments L1–L3 and T10–T12 were then compressed to create crush tractures in the L2 and T11 vertebral bodies, and linear corelation analyses were performed to compare each DXA measure with the failure properties of L2 and T11. Lumbar BMD from the lateral view correlated significantly with T11 altimate load (r=0.94, P<0.001), as did lumbar BMD from the anteroposterior projection (r=0.83, P=0.001). Significant correlations were also found between both lumbar BMD and BMC and the stiffness and energy to failure of I'll. Furthermore, BMD and BMC measured at L2 correlated significantly with L2 ultimate load, stiffness, and energy to failure. We conclude that bone mineral properties measured at the lumbar spine provide a valid assessment of the compressive strength of both thoracic and lumbar vertebrae. Lumbar BMD may therefore be used to derive an index for the prediction of thoracolumbar fractures to aid in the early intervention of vertebral fractures.Portions of this work were presented at the 40th Annual Meeting of the Orthopaedic Research Society and appeared in abstract form in the conference proceedings.     

Bone mineral density measured by dual-energy X-ray absorptiometry in healthy finnish women

Summary A cross-sectional study of 351 healthy Finnish women aged 20–76 years was done to establish reference values of bone mineral density (BMD) using dual-energy X-ray absorptiometry (DEXA). The effects of age and of several physical and lifestyle factors on BMD of the lumbar spine and proximal femur (femoral neck, trochanter, and Ward's triangle area) were investigated. Altogether 58 women were excluded from the final analysis due to significant spinal osteoarthritis or other diseases or drugs known to influence calcium or bone metabolism. The precision of the method was 0.9, 1.2, 2.7, and 2.4% in the lumbar, femoral neck, Ward's triangle and trochanter area, respectively. Lumbar BMD was increased by 30% (P<0.001) in 15 patients with osteoarthritis (21% of women 50 years or older), but it was apparently unaffected in 5 cases with aortic calcification. Except for the trochanter area, BMD diminished along with age, and this was significant after the menopause. The peak of mean BMD was observed at the age of 31–35 years in the spine and at the age of 20–25 years in the femoral neck and Ward's triangle. BMD was in a positive relationship to weight both in premenopausal and postmenopausal women and to the use of oral contraceptives in premenopausal women and to that of estrogen replacement therapy in postmenopausal women. Labors and pregnancies had a weak positive effect on BMD in premenopausal women. As compared with nonusers premenopausal women who had used alcohol showed a slightly decreased BMD of Ward's triangle. In postmenopausal women there was a positive correlation between alcohol intake and BMD.     

长期强的松治疗对绝经前SLE患者骨密度的影响

目的探讨长期强的松治疗对绝经前系统性红斑狼疮(SLE)患者骨密度的影响。方法142例SLE患者均为绝经前女性,年龄12~40岁(平均29·5岁)。正常对照78例女性,年龄15~39岁(平均28·9岁),排除影响骨代谢的各种急慢性疾病。应用HOLOGIC QDR4500双能量X线骨密度仪检测腰椎和股骨近端的骨密度值,测定血清雌二醇、雌三醇。结果①绝经前SLE患者骨量减少、骨质疏松发生率分别为42·96%、14·79%,均显著高于正常对照组(P值均<0·01);②骨质疏松和骨量减少患者服用强的松的时间、总剂量均显著高于骨量正常患者(P值均<0·01);③绝经前患者雌二醇与正常对照无显著差异,而雌三醇明显升高(P<0·01)。结论①长期服用强的松的绝经前SLE患者骨量减少和骨质疏松发生率均显著增高;②SLE患者骨量减少和骨质疏松的发生与使用强的松的时间和总剂量有关;③绝经前SLE患者雌三醇产生增多,可能对骨密度具有保护作用。     

Influence of patient's weight on dual-photon absorptiometry and dual-energy X-ray absorptiometry measurements of bone mineral density

Lumbar spine bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA) (Hologic QDR 1000) and by¹⁵³Gd dual-photon absorptiometry (DPA) (Novo Lab 22a) in 120 postmenopausal women. Though a high correlation existed between the two techniques, the ratio between DXA and DPA values was not constant. Using DXA we observed a higher dependence of BMD on weight than in the DPA measurements. To investigate the different behaviour of DXA and DPA machines with weight, we analysed the effects of increasing thickness of soft tissue equivalents on the BMD of the Hologic spine phantom and on the BMD equivalent of an aluminium standard tube. Increasing tissue-equivalent thickness caused the phantom BMD measured by DPA to decrease significantly but had not effect on the DXA measurements. The different behaviour of DPA and DXA equipment with regard to the phantoms could account for the differences observed in the relations between BMD and weight in the patients. Using multiple regression we studied the influence of weight and body mass index on the relation between BMD measured by the two techniques. The introduction of either of these variables into the regression resulted in an improvement of the prediction of the DXA values from the DPA values. However, the residual standard error of the estimate was still higher than the combined precision errors of the two methods, so that no simple relation allows a conversion of BMD_DPA into BMD_DXA. Our results confirm that BMD is positively correlated with weight in postmenopausal women; the influence of weight on BMD is blunted when the Novo Lab 22a DPA machine is used for measuring bone mineral.     

Comparison of areal and estimated volumetric bone mineral density values between older men and women

We compared areal bone mineral density (BMD) of the total body (TBMD), antero-posterior lumbar spine at L3 (APS), lateral spine at L3 (LS) and femoral neck (FN). In order to understand better the effect of gender-related size differences on BMD, we also compared the estimated volumetric BMD at L3 (VLS) and the femoral neck (VFN). Subjects were asymptomatic women (n=22) and men (n=44) with an age range of 58–79 years. BMD at each site was measured by dual-energy X-ray absorptiometry using a Hologic 2000 in array mode. Results of the statistical analyses (ANOVA) showed the men to have significantly greater BMD at all areal sites [APS, LS (p<0.05); FN (p<0.01); TBMD (p<0.001)]. The two estimated volumetric comparisons, however, showed no gender differences. Results demonstrate how measures from areal BMD measures can be misleading when comparing groups of different size. In older men and women planar measures may overestimate gender differences in BMD.     

MRI-measured bone marrow adipose tissue is inversely related to DXA-measured bone mineral in Caucasian women

Introduction Recent studies suggest that bone marrow adipose tissue (BMAT) might play a role in the pathogenesis of osteoporosis. Previous research using regional magnetic resonance spectroscopy methods to measure BMAT has reported inconsistent findings on the relationship between BMAT and dual-energy absorptiometry (DXA)-measured bone mineral density (BMD). Methods In the present study, total body and pelvic BMAT were evaluated in 56 healthy women (age 18–88 yrs, mean ± SD, 47.4 ± 17.6 yrs; BMI, 24.3 ± 4.2 kg/m²) with T1-weighted whole-body magnetic resonance imaging (MRI). BMD was measured using the whole-body DXA mode (GE Lunar DPX, software version 4.7). Results A strong negative correlation was observed between pelvic BMAT and BMD (total-body BMD, R = −0.743, P < 0.001; pelvic BMD, R = −0.646, P < 0.001), and between total-body BMAT and BMD (total-body BMD, R = −0.443, P < 0.001; pelvic BMD, R = −0.308, P < 0.001). The inverse association between pelvic BMAT and BMD remained strong after adjusting for age, weight, total body fat, and menopausal status (partial correlation: total-body BMD, R = −0.553, P < 0.001; pelvic BMD, R = −0.513, P < 0.001). BMAT was also highly correlated with age (pelvic BMAT, R = 0.715, P < 0.001; total-body BMAT, R = 0.519, P < 0.001). Conclusion MRI-measured BMAT is thus strongly inversely correlated with DXA-measured BMD independent of other predictor variables. These observations, in the context of DXA technical concerns, support the growing evidence linking BMAT with low bone density.     

甲亢131I治疗前后骨密度测定的临床分析

目的 探讨甲亢患者131I治疗前及治疗后临床缓解持续时间的长短及其骨密度的变化情况。方法 70例甲亢患者于131I治疗前和其中37例于131I治疗后临床缓解小于6个月、9-12个月和大于18个月,分别用双能X线骨密度仪(DEXA)进行骨密度(BMD)测定,并分别与年龄匹配正常健康者95例进行对照分析。结果 (1)甲亢131I治疗前和治疗后临床缓解小于6个月、9-12个月的L2-4BMD均明确低于正常对照组,差异有非常显著性,股骨上段各区(股骨颈、Ward's区、大转子区)虽低于正常对照组,但差异无明显性;(2)131I治疗后临床缓解大于18个月的L2-4及股骨上段各区的BMD改善至接近正常人的水平,差异无显著性;(3)131I治疗后临床甲低组L2-4及股骨上段各区(尤其Ward's区)的BMD均明显低于正常对照组,差异有非常显著性。结论 甲亢经131I治疗后临床缓解6-12个月骨矿含量改善不明显,至18个月逐渐增加接近正常对照组水平;131I治疗后临床甲低持续时间大于6个月者,同样会导致骨矿含量的降低。     

Study of bone mineral density in lumbar spine and femoral neck in a Spanish population

The aim of this study was to generate standard curves for bone mineral density (BMD) in a Spanish population using dual-energy X-ray absorptiometry (DXA), at both lumbar spine and femoral neck sites. The total sample size was 2442 subjects of both sexes aged 20–80 years, stratified according to survival rates, demographic distribution by local regions and sex ratio in the Spanish population. Subjects with suspected conditions affecting bone metabolism or receiving any treatment affecting bone mineralization were excluded. The study was carried out in 14 hospitals and bone density measurements were performed, using a QDR/1000 Hologic device. In the female population, the highest value for lumbar spine BMD was found within the 30–39 years age group, being significantly lower after the age of 49 years. In the male population, the highest values for lumbar spine BMD are found one decade earlier than in the female population and become significantly lower after the age of 69 years. The highest values for femoral neck BMD in men and women was found in the 20–29 year age group. Values for femoral neck BMD in the female population become statistically lower after the age of 49 years, while in the male population this effect was seen after the age of 69 years. Values for femoral neck BMD were higher in men than women at all ages.Others investigators of the Multicentre Research Project on Osteoporosis: Drs Torrijos, Aguado, Espinosa (H. La Paz, Madrid); Drs Lozano, Gonzalez (H. Clínico San Carlos, Madrid); Drs Yagüe, López Gavilanes (F. Jimenez Díaz, Madrid); Drs Portugal, Del Pino, Martín (H. Clínico Univ., Salamanda); Drs Roig, Nolla (Ciudad Sanitaria Bellvitge, Barcelona); Drs Farrerons, Lopez Navidad, Yoldi (H. Sta. Creu i San Pau, Barcelona); Drs Diez Pérez, Kanterewicz, Martínez Izquierdo, H. de la Esperanza, Barcelona); Drs. Romeu, Edo, Monzó (H. La Fe, Valencia); Drs Moruno, Vazquez (H. Clínico Univesitario, Sevilla); Drs Escobar, Muñoz Torres, Raya, Salvatierra (H. Clínico Universitario, Granada); Drs Cannata, Gómez Alonso, Virgós (H. Central de Asturias); Drs Ferrer, Peguero (H. Miguel Servet, Zaragoza); Drs Ganoza, Barrios (Clinica Universitaria, Pamplona); Drs Betancor, Sosa Henríquez, Hernandez Hernandez (H. Insular Las Palmas).     

Bone mineral density after total joint arthroplasty of lower extremities in rheumatoid arthritis patients

We studied the effects on the axial bone mass of total joint arthroplasty (TJA) for lower extremities in 48 female rheumatoid arthritis (RA) patients by using dual-energy X-ray absorptiometry (DXA). Twenty-nine postmenopausal RA patients treated only with nonsteroidal anti-inflammatory drugs (NSAIDs) served as controls. They were studied for an average duration of 63 months. The reduction in the bone mineral density (BMD) of the lumbar spine (L2–4) was significant in both groups (p < 0.01∼0.05), but it was not statistically different between the two groups. The BMD of the femoral neck decreased significantly in both groups (p < 0.01–0.05) after 2 years, but it was not statistically different between the two groups. Our data suggest that TJA slowed the rapid axial bone loss usually associated with advanced RA. Received: 7 February 2000     

脊柱退行性疾病对腰椎前后位骨密度的影响分析

双能X线骨密度仪检测骨密度是诊断骨质疏松症的"金标准",学者推荐50岁以上人群采用腰椎前后位进行测量。然而骨质疏松症发病率较高的老年人群,常常合并罹患多种脊柱退行性疾病,例如腰椎间盘突出、退行性侧凸、骨赘增生等,这些病理改变可导致腰椎前后位骨密度值准确性降低。因此,提高腰椎骨密度测量准确性,对于骨质疏松症的诊断和治疗具有重要意义。本文就常见的脊柱退行性疾病对腰椎前后位骨密度的影响作一综述,以期帮助临床医生全面评估和诊断骨质疏松症。     

The prevalence of significant left-right differences in hip bone mineral density

Introduction We determined the prevalence of left-right differences in hip bone mineral density (BMD) by dual-energy x-ray absorptiometry (DXA) and the resultant consequence, namely: the frequency at which patients would be classified differently if lumbar spine and only one hip (rather than both hips) were measured.Methods This was a retrospective DXA scan reanalysis of 3012 white women ≥50 yrs who had scans of both hips using Hologic DXA systems. The difference between left and right hips was considered significant if it exceeded the least significant change (LSC) for any of three hip subregions (total hip, femoral neck, trochanter). The number of women with osteoporosis in both hips, the left hip only, or the right hip only was determined by lowest T-score from total hip, femoral neck, or trochanter.Results Despite high left-right correlations of subregion BMD, significant left-right differences in BMD were common: the difference exceeded the LSC for 47% of women at total hip, 31% at femoral neck, and 56% at trochanter. Left-right differences in BMD that exceeded the LSC affected the percent agreement of left-right hip classification: for all women irrespective of spine status, there was 77% classification (diagnostic) agreement in hip pairs in which the left-right hip BMD difference exceeded the LSC versus 87% agreement in which LSC was not exceeded (significant difference in proportions, P<0.0001). The greatest risk of different classification would occur in women with normal spines as the diagnosis might be determined by hip T-scores. Using L1-4 lumbar spine T-scores, 1229 women were normal at the spine. Twenty-four (2%) were osteoporotic at both hips. However, 12 women (1%) were osteoporotic only in the left hip (significantly different from zero, P<0.001) and 11 (1%) only in the right hip (P<0.001); of these 23 women, the difference in BMD between the osteoporotic hip and the contralateral hip exceeded the LSC in 16 (70% of those with osteoporosis in only one hip). Using L1-4 lumbar spine T-scores, 1159 women were osteopenic at the spine. Of these, 126 (11%) were osteoporotic at both hips, 54 (5%) only in the left hip (P<0.001), and 42 (4%) only in the right hip (P<0.001); of these 96 women, the difference in BMD between the osteoporotic hip and the contralateral hip exceeded the LSC in 56 (58% of those with osteoporosis in only one hip).Conclusions A statistically significant number of women with osteoporosis are potentially classified differently when scanning only one hip as a result of the high prevalence of left-right differences in BMD. Although the percentages are low, the total number of women affected may be large. From a public health perspective, the practice of scanning both hips could potentially identify more women with osteoporosis and may help prevent future hip fractures.