Discordance in lumbar bone mineral density measurements by quantitative computed tomography and dual-energy X-ray absorptiometry in postmenopausal women: a prospective comparative study

Background ContextLevel-specific lumbar bone mineral density (BMD) evaluation of a single vertebral body can provide useful surgical planning and osteoporosis management information. Previous comparative studies have primarily focused on detecting spinal osteoporosis but not at specific levels.PurposeTo compare the detection rate of lumbar osteoporosis between quantitative computed tomography (QCT) and dual-energy X-ray absorptiometry (DXA); to explore and analyze the distribution models of QCT-derived BMD and DXA T-score at the specific levels; and to evaluate the diagnostic accuracy of level-specific BMD thresholds for the prediction of osteoporotic vertebral compression fracture (OVCF) in postmenopausal women.Study Design/SettingA comparative analysis of prospectively collected data comparing QCT-derived BMD with DXA T-score.Patient SampleA total of 296 postmenopausal women who were referred to the spine service of a single academic institution were enrolled.Outcome MeasuresQCT-derived BMD and DXA T-score at specific levels, with or without osteoporotic vertebral compression fracture.MethodsPostmenopausal women who underwent QCT and DXA within a week of admission from May 2019 to June 2022 were enrolled. The diagnostic criteria for osteoporosis recommended by the World Health Organization and the American College of Radiology were used for lumbar osteoporotic diagnosis. To evaluate differences in lumbar BMD measurements at specific levels, a threshold of T score=-2.5 and QCT-derived BMD = 80 mg/cm³ were used to categorize level-specific lumbar BMD into low and high BMD. Disagreements in BMD categorization between DXA and QCT were classified as a minor or major discordance based on the definition by Woodson. Data between QCT and DXA were visualized in a stacked bar plot and analyzed. Correlations between DXA and QCT at the specific levels were evaluated using Pearson's linear correlation and scatter plots. Curve fitting of BMD distribution, receiver operating characteristic (ROC) and area under the curve (AUC) for each single vertebral level was performed.ResultsOf the 296 patients, QCT diagnosed 61.1% as osteoporosis, 30.4% as osteopenia and 8.4% as normal. For those screened with DXA, 54.1% of the patients had osteoporosis, 29.4% had osteopenia and 16.6% had normal BMD. Diagnoses were concordant for 194 (65.5%) patients. Of the other 102 discordant patients, 5 (1.7%) were major and 97 (32.8%) were minor. Significant correlations in level-specific BMD between DXA and QCT were observed (p<.001), with Pearson's correlation coefficients ranging from 0.662 to 0.728. The correlation strength was in the order of L1 > L2 > L3 > L4. The low BMD detection rate for QCT was significantly higher than that for DXA at the L3 and L4 levels (65% vs. 47.9% and 68.1% vs 43.7, respectively, p<.001). Patients with OVCF showed significantly lower QCT-derived BMD (47.2 mg/cm³ vs. 83.2 mg/cm³, p<.001) and T-score (-3.39 vs. -1.98, p<.001) than those without OVCF. Among these patients, 82.8% (101/122) were diagnosed with osteoporosis by QCT measurement, while only 74.6% (91/122) were diagnosed by DXA. For discrimination between patients with and without OVCF, QCT-derived BMD showed better diagnosed performance (AUC range from 0.769 to 0.801) than DXA T-score (AUC range from 0.696 to 0.753).ConclusionQCT provided a more accurate evaluation of lumbar osteoporosis than DXA. The QCT-derived BMD measurements at a specific lumbar level have a high diagnostic performance for OVCF.     

Association of 3D Geometric Measures Derived From Quantitative Computed Tomography With Hip Fracture Risk in Older Men

We investigated the associations of 3D geometric measures and volumetric bone mineral density (vBMD) of the proximal femur assessed by quantitative computed tomography (QCT) with hip fracture risk among elderly men. This study was a prospective case‐cohort design nested within the Osteoporotic Fractures in Men Study (MrOS) cohort. QCT scans of 230 men (65 with confirmed hip fractures) were evaluated with Mindways' QCTPRO‐BIT software. Measures that are indicative of bone strength for the femoral neck (FN) and for the trochanteric region (TR) were defined. Bending strength measures were estimated by minimum section modulus, buckling strength by buckling ratio, and a local thinning index (LTI). Integral and trabecular vBMD measures were also derived. Areal BMD (aBMD) of the total proximal femur from dual‐energy X‐ray absorptiometry (DXA) is presented for comparison. Associations of skeletal measures with incident hip fracture were estimated with hazard ratios (HR) per standard deviation and their 95% confidence intervals (CI) from Cox proportional hazard regression models with adjustment for age, body mass index (BMI), site, and aBMD. Men with hip fractures were older than men without fracture (77.1 ± 6.0 years versus 73.3 ± 5.7 years, p < 0.01). Age, BMI, and site‐adjusted HRs were significant for all measures except TR_LTI. Total femural BMD by DXA (HR = 4.9, 95% CI 2.5–9.9) and QCT (HR = 5.5, 95% CI 2.5–11.7) showed the strongest association followed by QCT FN integral vBMD (HR = 3.6, 95% CI 1.8–6.9). In models that additionally included aBMD, FN buckling ratio (HR = 1.9, 95% CI 1.1–3.2) and trabecular vBMD of the TR (HR = 2.0, 95% CI 1.2–3.4) remained associated with hip fracture risk, independent of aBMD. QCT‐derived 3D geometric indices of instability of the proximal femur were significantly associated with incident hip fractures, independent of DXA aBMD. Buckling of the FN is a relevant failure mode not entirely captured by DXA. Further research to study these relationships in women is warranted. © 2016 American Society for Bone and Mineral Research.     

Measurement of subregional vertebral bone mineral density in vitro using lateral projection dual-energy X-ray absorptiometry: validation with peripheral quantitative computed tomography

Although a strong relationship exists between areal bone mineral density (aBMD) derived from dual-energy X-ray absorptiometry (DXA) and bone strength, the predictive validity of aBMD for osteoporotic vertebral fractures remains suboptimal. The diagnostic sensitivity of DXA may be improved by assessing aBMD within vertebral subregions, rather than relying on an estimate derived from the total area of the vertebra. The objective of this study was to validate a method of measuring subregional vertebral aBMD in vitro using lateral-projection DXA against subregional volumetric BMD (vBMD) measured with peripheral quantitative computed tomography (pQCT). A mixed set of 49 lumbar and thoracic vertebrae from 25 donors were scanned using lateral-projection DXA and pQCT. aBMD and apparent vBMD were measured in 7 vertebral regions (1 total area and 6 subregions) from the lateral DXA scan. vBMD was calculated in anatomically equivalent regions from pQCT scan data, using a customised software program designed to increase efficiency of the analysis process. Significant differences in densitometric parameters between subregions were observed by DXA and pQCT (P < 0.01). Subregional vBMD derived from pQCT was explained by a significant proportion of the variance in DXA-derived aBMD (R ² = 0.51–0.67, P < 0.05) and apparent vBMD (R ² = 0.64–0.75, P < 0.05). These results confirm the validity of measuring aBMD in vertebral subregions using lateral-projection DXA. The clinical significance should now be explored.     

Distribution of bone density in the proximal femur and its association with hip fracture risk in older men: The osteoporotic fractures in men (MrOS) study

This prospective case‐cohort study aimed to map the distribution of bone density in the proximal femur and examine its association with hip fracture. We analyzed baseline quantitative computed tomography (QCT) scans in 250 men aged 65 years or older, which comprised a randomly‐selected subcohort of 210 men and 40 cases of first hip fracture during a mean follow‐up period of 5.5 years. We quantified cortical, trabecular, and integral volumetric bone mineral density (vBMD), and cortical thickness (CtTh) in four quadrants of cross‐sections along the length of the femoral neck (FN), intertrochanter (IT), and trochanter (TR). In most quadrants, vBMDs and CtTh were significantly (p < 0.05) lower in cases compared to the subcohort and these deficits were present across the entire proximal femur. To examine the association of QCT measurements with hip fracture, we merged the two quadrants in the medial and lateral aspects of the FN, IT, and TR. At most sites, QCT measurements were associated significantly (p < 0.001) with hip fracture, the hazard ratio (HR) adjusted for age, body mass index (BMI), and clinical site for a 1‐SD decrease ranged between 2.28 (95% confidence interval [CI], 1.44–3.63) to 6.91 (95% CI, 3.11–15.53). After additional adjustment for total hip (TH) areal BMD (aBMD), trabecular vBMDs at the FN, TR, and TH were still associated with hip fracture significantly (p < 0.001), the HRs ranged from 3.21 (95% CI, 1.65–6.24) for the superolateral FN to 6.20 (95% CI, 2.71–14.18) for medial TR. QCT measurements alone or in combination did not predict fracture significantly (p > 0.05) better than TH aBMD. With an area under the receiver operating characteristic curve (AUC) of 0.901 (95% CI, 0.852–0.950), the regression model combining TH aBMD, age, and trabecular vBMD predicted hip fracture significantly (p < 0.05) better than TH aBMD alone or TH aBMD plus age. These findings confirm that both cortical and trabecular bone contribute to hip fracture risk and highlight trabecular vBMD at the FN and TR as an independent risk factor. © 2012 American Society for Bone and Mineral Research.     

Opportunistic Quantitative CT Bone Mineral Density Measurement at the Proximal Femur Using Routine Contrast‐Enhanced Scans: Direct Comparison With DXA in 355 Adults

For patients undergoing routine contrast‐enhanced CT examinations, an opportunity exists for concurrent osteoporosis screening without additional radiation exposure or patient time using proximal femur CT X‐ray absorptiometry (CTXA). We investigated the effect of i.v. contrast enhancement on femoral neck CTXA T‐score measurement compared with DXA. This cohort included 355 adults (277 female; mean age, 59.7 ± 13.3 years; range, 21 to 90 years) who underwent standard contrast‐enhanced CT assessment at 120 kV_p over an 8‐year interval, as well as DXA BMD assessment within 100 days of the CT study (mean 46 ± 30 days). Linear regression and a Bland‐Altman plot were performed to compare DXA and CTXA results. CTXA diagnostic sensitivity and specificity was evaluated with DXA as the reference standard. There was good correlation between DXA and CTXA (r² = 0.824 for both areal BMD and T‐scores) and the SD of the distribution of residuals was 0.063 g/cm² or 0.45 T‐score units. There was no trend in differences between the two measurements and a small bias was noted with DXA T‐score +0.18 units higher than CTXA. CTXA had a sensitivity for discriminating normal from low bone mineral density of 94.9% (95% CI, 90.6% to 97.4%). For opportunistic osteoporosis screening at routine post‐contrast abdominopelvic CT scans, CTXA produces T‐scores similar to DXA. Because femoral neck CTXA BMD measurement is now included in the WHO Fracture Risk Assessment Tool (FRAX) tool, this opportunistic method could help to increase osteoporosis screening because it can be applied regardless of the clinical indication for CT scanning. © 2016 American Society for Bone and Mineral Research.     

Bone Loss After Bariatric Surgery: Discordant Results Between DXA and QCT Bone Density

Several studies, using dual‐energy X‐ray absorptiometry (DXA), have reported substantial bone loss after bariatric surgery. However, profound weight loss may cause artifactual changes in DXA areal bone mineral density (aBMD) results. Assessment of volumetric bone mineral density (vBMD) by quantitative computed tomography (QCT) may be less susceptible to such artifacts. We assessed changes in BMD of the lumbar spine and proximal femur prospectively for 1 year using DXA and QCT in 30 morbidly obese adults undergoing Roux‐en‐Y gastric bypass surgery and 20 obese nonsurgical controls. At 1 year, subjects who underwent gastric bypass surgery lost 37 ± 2 kg compared with 3 ± 2 kg lost in the nonsurgical controls (p < 0.0001). Spine BMD declined more in the surgical group than in the nonsurgical group whether assessed by DXA (?3.3 versus ?1.1%, p = 0.034) or by QCT (?3.4 versus 0.2%, p = 0.010). Total hip and femoral neck aBMD declined significantly in the surgical group when assessed by DXA (?8.9 versus ?1.1%, p < 0.0001 for the total hip and ?6.1 versus ?2.0%, p = 0.002 for the femoral neck), but no changes in hip vBMD were noted using QCT. Within the surgical group, serum P1NP and CTX levels increased by 82% ± 10% and by 220% ± 22%, respectively, by 6 months and remained elevated over 12 months (p < 0.0001 for all). Serum calcium, vitamin D, and PTH levels remained stable in both groups. We conclude that moderate vertebral bone loss occurs in the first year after gastric bypass surgery. However, striking declines in DXA aBMD at the proximal femur were not confirmed with QCT vBMD measurements. These discordant results suggest that artifacts induced by large changes in body weight after bariatric surgery affect DXA and/or QCT measurements of bone, particularly at the hip. © 2014 American Society for Bone and Mineral Research.     

A Comparative Study of Computed Digital Absorptiometry and Conventional Dual-Energy X-ray Absorptiometry in Postmenopausal Women

The aim of the study was to evaluate whether computed digital absorptiometry (CDA) of the hand might be a useful screening technique for identifying patients with postmenopausal osteoporosis and to compare the results of CDA with those of dual-energy X-ray absorptiometry (DXA) of the lumbar spine and femoral neck. We studied 230 postmenopausal women (mean age 58.4 ± 7.9 years). For CDA, bone mineral density (BMD) was measured with an AccuDEXA Schick densitometer in the third middle phalanx of the nondominant hand. For DXA, BMD of the lumbar spine and upper femur was assessed using a DXA Hologic QDR-1000 densitometer. We did a comparative analysis (ANOVA) and linear correlation tests. Sensitivity and specificity of CDA and receiver operating characteristic (ROC) curves for the diagnosis of osteoporosis were calculated. The mean BMD with CDA was 0.445 ± 0.084 (T-score: −1.27 ± 1.29). The mean BMD (g/cm²) with DXA at the lumbar spine was 0.877 ± 0.166 (T-score: −1.52 ± 1.59) and 0.708 ± 0.127 at the femoral neck (T-score: −1.12 ± 1.25). BMD at the lumbar spine and femoral neck correlated positively with CDA of the hand (r= 0.66 and r= 0.65 respectively, p<0.001). When using as cut-off a T-score of −2.5, according to WHO criteria, 76 women (33%) had osteoporosis of the lumbar spine and/or femoral neck with DXA and 42 (18%) with CDA (p<0.001). The kappa score for osteoporosis was 0.33 for CDA versus spinal DXA and 0.35 for CDA versus femoral DXA. With the cut-off level used, sensitivity and specificity of CDA in detecting osteoporosis at the lumbar spine were 0.39 and 0.90, respectively; sensitivity and specificity of CDA in identifying osteoporosis at the femoral neck were 0.58 and 0.87, respectively. The positive predictive value of CDA for osteoporosis was 69% and the negative predictive value was 75%. The area under the ROC curve for osteoporosis was 0.822 ± 0.028. We conclude that: (a) CDA assessment has a moderate correlation with BMD measured by DXA at the lumbar spine and femoral neck; (b) CDA has a low sensitivity for the diagnosis of osteoporosis compared with spinal and femoral DXA; and (c) predictive values for osteoporosis at both the lumbar spine and femoral neck are acceptable. Received: September 2000 / Accepted: January 2001     

Ultrasound and X-ray-Based Bone Densitometry in Patients with Anorexia Nervosa

In 20 patients (mean age 23 ± 5 years) with anorexia nervosa (AN), bone mass was evaluated by broadband ultrasound attenuation (BUA) of the calcaneus, peripheral quantitative computed tomography (pQCT) of the distal radius, and dual X-ray absorptiometry (DXA) of the lumbar spine and the hip. Compared with 20 age- and sex- matched healthy controls, patients with AN showed marked osteopenia at all measuring sites. Values of BUA (33.0 ± 9dB/MHz vs. 51.0 ± 5.7 dB/MHz; P < 0.0001) and of BMD of all regions of the hip (e.g., femoral neck: 0.71 ± 0.13 g/cm² versus 0.89 ± 0.07 g/cm²; P < 0.001), lumbar spine (0.82 ± 0.15 g/cm² versus 1.24 ± 0.06 g/cm²; P < 0.003) and total BMD of the peripheral radius (303.2 ± 75 g/cm³ versus 369.4 ± 53.2 g/cm³, P < 0.001) were significantly reduced. Calculating a Z-score we found the most prominent differences between AN and controls by BUA of the calcaneus (−3.2 ± 1.6), followed by DXA at the lumbar spine (−2.9 ± 2.2) and the hip (femoral neck −2.1 ± 1.7) and by pQCT at the distal radius (total BMD −1.2 ± 2.0). There were highly significant correlations between BUA of the calcaneus and BMD of the femoral neck (r = 0.78, P < 0.0001) and lumbar spine (r = 0.75, P < 0.0001) as well as between BMD values of the femoral neck and lumbar spine (r = 0.95; P < 0.0001). In addition, there were significant correlations (P < 0.001) between body mass index (BMI) and the three different measuring sites and between the duration of the disease and BUA (r = 0.5, P < 0.05). Our data suggest that BUA of the calcaneus is a valuable tool in the management of osteoporosis. Being a fast, radiation-free investigation method of good acceptance, it may be well suited for an assessment of the skeletal status in patients with AN. Received: 14 October 1998 / Accepted: 10 December 1999     

Daily Physical Education in the School Curriculum in Prepubertal Girls during 1 Year is Followed by an Increase in Bone Mineral Accrual and Bone Width—Data from the Prospective Controlled Malmö Pediatric Osteoporosis Prevention Study

The aim of this study was to evaluate a general school-based 1-year exercise intervention program in a population-based cohort of girls at Tanner stage I. Fifty-three girls aged 7–9 years were included. The school curriculum-based exercise intervention program included 40 minutes/school day. Fifty healthy age-matched girls assigned to the general school curriculum of 60 minutes physical activity/week served as controls. Bone mineral content (BMC, g) and areal bone mineral density (aBMD, g/cm²) were measured with dual X-ray absorptiometry (DXA) of the total body (TB), lumbar spine (L2–L4 vertebrae), third lumbar vertebra (L3), femoral neck (FN), and leg. Volumetric bone mineral density (g/cm³) and bone width were calculated at L3 and FN. Total lean body mass and total fat mass were estimated from the TB scan. No differences at baseline were found in age, anthropometrics, or bone parameters when the groups were compared. The annual gain in BMC was 4.7 percentage points higher in the lumbar spine and 9.5 percentage points higher in L3 in cases than in controls (both P < 0.001). The annual gain in aBMD was 2.8 percentage points higher in the lumbar spine and 3.1 percentage points higher in L3 in cases than in controls (both P < 0.001). The annual gain in bone width was 2.9 percentage points higher in L3 in cases than in controls (P < 0.001). A general school-based exercise program in girls aged 7–9 years enhances the accrual of BMC and aBMD and increases bone width.     

Effect of antioxidants combined to resistance training on BMD in elderly women: a pilot study

Summary  We determined the effect of antioxidants and resistance training on bone mineral density of postmenopausal women. After 6 months, we observed a significant decrease in the lumbar spine BMD of the placebo group while other groups remained stable. Antioxidants may offer protection against bone loss such as resistance training. Introduction  The purpose of this pilot study was to determine the effects of antioxidant supplements combined to resistance training on bone mineral density (BMD) in healthy elderly women. Methods  Thirty-four postmenopausal women (66.1 ± 3.3 years) were randomized in four groups (placebo, n = 7; antioxidants, n = 8; exercise and placebo, n = 11; and exercise and antioxidants, n = 8). The 6-month intervention consisted in antioxidant supplements (600 mg vitamin E and 1,000 mg vitamin C daily) or resistance exercise (3×/week). Femoral neck and lumbar spine BMD (DXA) and dietary intakes (3-day food record) were measured before and after the intervention. A repeated measure ANOVA and non-parametric Mann–Whitney U tests were used. Results  We observed a significant decrease in the placebo group for lumbar spine BMD (pre, 1.01 ± 0.17 g/cm²; post, 1.00 ± 0.16 g/cm²; P < 0.05 respectively) while it remained stable in all other groups. No changes were observed for femoral neck BMD. Conclusions  Antioxidant vitamins may offer some protection against bone loss in the same extent as resistance exercise although combining both does not seem to produce additional effects. Our results suggest to further investigate the impact of antioxidant supplements on the prevention of osteoporosis.     

Muscle mass deficits are associated with bone mineral density in men with idiopathic vertebral fracture

Introduction and hypothesis The causes of idiopathic vertebral fractures (IVF) in men are poorly understood. We hypothesised that in IVF, areal bone mineral density (aBMD) deficits would be associated with reduced muscle mass. Methods In this case-control study, 48 men (61.5 ± 12.1 years old) presenting with symptomatic IVF were compared with 48 healthy controls matched for age (±5 years) and stature (±5 cm). The aBMD and soft-tissue body composition were determined by dual energy X-ray absorptiometry (DXA). Muscle mass was defined as the ratio of appendicular lean mass to the square of height (ALMI). Sex hormones, IGF-I and its binding protein IGFBP-3 were measured by immunoassay. Results ALMI was significantly lower in IVF patients (8.27 ± 0.90 vs 8.65 ± 0.88 kg/m², t = 2.193, df = 47, P = 0.033 by paired sample t-test). Hierarchical regression analysis revealed that for IVF patients, ALMI explained the greatest proportion of variance in BMD at the lumbar spine, femoral neck and total hip (R ² _change = 16.4–22.7%, P = 0.012–0.002) and only IGFBP-3 explained variance in ALMI (R ² _change = 19.9%, P = 0.006). Conclusions In men with IVF, ALMI was reduced and associated with IGFBP-3. ALMI was identified as a novel factor that explained a greater proportion of variance in BMD than either fat mass or serum biochemistry. Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Quantitative Computed Tomography in the Evaluation of Spinal Osteoporosis Following Spinal Cord Injury

Disuse osteoporosis occurs in the lower extremities of patients with spinal cord injury (SCI). However, spinal osteoporosis is not usually observed in these patients. We investigated lumbar spine bone mineral density (BMD) in SCI patients using single energy quantitative computed tomography (QCT) and dual-energy X-ray absorptiometry (DXA). Our study population consisted of 64 patients with long-standing SCI. Spine BMD (g/cm³) was assessed by QCT at four vertebrae ranging from T11 to L4 with single midvertebral CT slices 1 cm thick parallel to the vertebral end-plates. Confounding variables affecting normal trabecular bone pattern, such as compression fractures, surgical hardware or fat replacement, were excluded. For a subset of 29 patients, DXA values of the spine and femoral neck were also measured, and QCT and DXA Z-scores were compared On the average, the 64 SCI patients had Z-scores 2.0 ± 1.2 below those of age-matched controls. In the subset of 29 patients with both QCT and DXA measurements, the QCT and DXA Z-scores were 2.4 ± 1.1 below and 1.3 ± 2.3 above the mean, respectively (p<0.0001). Our results indicate that QCT reveals osteoporosis of the spine after SCI, in contrast to DXA. We postulate that QCT is more valuable for evaluating spinal osteoporosis following SCI than DXA and thus recommend QCT for spinal BMD studies in SCI. Received: 20 December 1999 / Accepted: 17 April 2000     

Relationship between the pelvic osteolytic volume on computed tomography and clinical outcome in patients with cementless acetabular components

The purpose of this study was to evaluate the relationship between the pelvic osteolytic volume on computed tomography (CT) and clinical outcome in patients with cementless acetabular components. We reviewed 87 patients (104 hips) who met the following inclusion criteria: (1) there was evidence of pelvic osteolysis on CT at a minium of five years postoperatively, (2) all cups and stems were radiographically stable at the time of CT, (3) the follow-up period after CT was a minimum of two years clinically. The mean pelvic osteolytic volume was 2.3 ± 6.9 cm³. The mean Harris hip score (HHS) at CT was 92.3 ± 7.9 points. Inversely moderate correlation (r = −0.569, P < 0.05) was found between the HHS at CT and pelvic osteolytic volume. In ten cases of hips with acetabular revisions, the mean pelvic osteolytic volume was 16.3 ± 26.9 cm³. The mean HHS at CT and HHS at reoperation was 87.6 ± 9.2 points and 73.4 ± 8.8 points, respectively, with significant difference (P < 0.05). The area under curve (ROC) analysis showed that the optimal cutoff value of the osteolytic volume was 4.8 cm³ with 100% each for sensitivity and specificity. We conclude that the amount of pelvic osteolytic volume on CT may be used to guide treatment decision-making in patients with well-fixed cementless acetabular components who show evidence of pelvic osteolysis.     

Peritoneal membrane recruitment in rats: a micro-computerized tomography (μCT) study

The peritoneal contact surface area (PCSA), which represents the area parameter in the mass transfer area coefficient (MTAC), is a crucial marker in the evaluation of peritoneal dialysis effectiveness. However, the capacity to recruit a larger PCSA has only been rarely demonstrated in vivo and, in most cases, changes in MTAC are interpreted as permeability changes and not as surface area variations. Here, we report the use of micro-computerized tomography (μCT) for the measurement of PCSA changes to various fill volumes. Using this three-dimensional imaging method, PCSA was measured in vivo in 26 healthy Wistar rats receiving intraperitoneally increasing fill volumes of peritoneal dialysis solutions: 5 mL (group 1, n = 8), 10 mL (group 2, n = 8) and 15 mL (group 3, n = 10) per 100 g of body weight. A non-ionic iodinated contrast agent was added to the dialysis solution in order to distinguish the intraperitoneal dialysis solutions from soft tissues. The normalized PCSA/weight ratio (cm²/g) increased with fill volume: 1.12 ± 0.10 cm²/g (range 0.98–1.25) in group 1; 1.74 ± 0.08 cm²/g (range 1.64–1.87) in group 2; 2.13 ± 0.09 cm²/g(range 1.90–2.30) in group 3. With this μCT method, PCSA recruited in vivo with a 10 mL/100 g fill volume was in the range 94–107%) of ex vivo total peritoneal surface area (evPSA), as calculated with the Kuzlan’s formula. With a 15 mL/100 g fill volume, the in vivo-measured PCSA, the exchange surface area, surpassed the evPSA (range 113–139%).     

Better late than never? Experience with intravenous pamidronate treatment in patients with low bone mass or fractures following cardiac or liver transplantation

 Organ transplantation is associated with a high turnover of bone metabolism, and an increased loss of bone mass and incidence of osteoporotic fractures. Established therapies for osteoporosis after organ transplantation are still lacking, however. We report on an intravenous bisphosphonate therapy initiated in transplant patients because of a high rate of bone loss or incident osteoporotic fractures. Twenty-one patients after liver transplantation and 13 patients after heart transplantation received 30 mg pamidronate intravenously every 3 months, combined with 1000 mg calcium and 1000 IU vitamin D per day. The median time interval between transplantation and start of pamidronate treatment was 1.9 years in cardiac patients and 2.3 years in liver patients. Lumbar spine bone mineral density (LS BMD) and femoral neck BMD (FN BMD) were measured before and every 6 months after pamidronate therapy was initiated. Spinal radiographs were performed annually. Biochemical markers of bone metabolism were determined every 3 months, immediately before pamidronate administration. From a previous observational study, 58 patients treated only with calcium and vitamin D were matched for age, sex, pretransplantation LS BMD and time interval between transplantation and the first pamidronate treatment. In the pamidronate-treated patients, the mean increase in LS BMD adjusted for baseline values amounted to 0.080 ± 0.038 g/cm² (8.6 ± 4.0 %) after 1 year and 0.091 ± 0.058 g/cm² (10.4 ± 6.1%) after 2 years compared with 0.001 ± 0.037 g/cm² (0.26 ± 4.0%) after 1 year and 0.015 ± 0.057 g/cm² (1.8 ± 6.0%) after 2 years in the historical control group (absolute LS BMD changes pamidronate group vs historical group p < 0.0001 after 1 and 2 years). The changes of FN BMD were 0.024 ± 0.043 g/cm² (3.2 ± 6.1%) after 1 year and 0.046 ± 0.052 g/cm² (7.0 ± 6.1%) after 2 years in the pamidronate group compared with −0.012 ± 0.043 g/cm² (−1.6 ± 6.1%) after 1 year and −0.013 ± 0.052 g/cm² (−1.1 ± 6.1%) after 2 years in the historical control group (absolute FN BMD changes pamidronate group vs historical group p=0.003 after 1 year and p=0.001 after 2 years). From a total of 287 application cycles of pamidronate treatment, no severe side effects were observed and non-severe side effects were seen in only 39 cycles (13.6%). We conclude that cyclic intravenous pamidronate treatment is beneficial to patients with low bone mass or osteoporotic fractures following transplant, even when not immediately initiated. Received: 5 March 2002 / Accepted: 27 August 2002     

Relationships between T-scores at the hip and bone mineral density at the distal femur and proximal tibia in persons with spinal cord injury

Objective: To identify T-score values at the total hip (TH) and femoral neck (FN) that correspond to the cutoff value of <0.60?g/cm² for heightened risk of fracture at the distal femur (DF) and proximal tibia (PT).

Design: Retrospective analysis of data in a research center’s database.

Setting: Community-based individuals with spinal cord injury (SCI).

Participants: 105 unique individuals with SCI.

Outcome Measurements: DXA derived areal BMD (aBMD) and T-score of the DF, PT, TH, and FN.

Results: The aBMD at the DF and PT regions were predictors of T-scores at the TH (R ²?=?0.63, P?<?0.001 and R ²?=?0.65, P?<?0.001) and FN (R ²?=?0.55, P?<?0.001 and R ²?=?0.58, P?<?0.001). Using the DF and PT aBMD of 0.60?g/cm² as a value below which fractures were more likely to occur, the predicted T-score was ?3.1 and ?3.5 at the TH and ?2.6 and ?2.9 at the FN, respectively. However, when the predicted and observed T-score values disagree outside the 95% limit of agreement, the predicted T-score values are lower than the measured T-score values, overestimating the measured values between ?2.0 and ?4.0 SD.

Conclusion: The DF and PT cutoff value for aBMD of 0.60?g/cm² was a moderate predictor of T-score values at the TH and FN, with considerable inaccuracies outside the clinically acceptable limits of agreement. As such, the direct measurement of knee aBMD in persons with SCI should be performed, whenever possible, prior to prescribing weight bearing upright activities, such as robotic exoskeletal-assisted walking.     

Longitudinal study of bone mineral density in children with idiopathic hypercalciuria

Children with idiopathic hypercalciuria (IH) may have a reduced bone mineral density (BMD), which could impact on bone health in adulthood. There is currently no strong evidence for a preferred treatment of such children. The aim of our study was to evaluate the BMD z-score before and after treating children and adolescents with IH with potassium citrate and thiazides. The study consisted of a historical cohort of 80 pediatric patients who were evaluated between October 1989 and November 2010. Bone scanning and densitometry measurements were made with dual-emission X-ray absorptiometry. Lumbar-spine BMD (g/cm²) and BMD z-score were evaluated before and after treatment. The t test and Mann–Whitney U test were used for statistical analysis. Forty-three boys and 37 girls were followed for a median time of 6.0 years. Median calcium excretion before and after treatment was 5.0 and 2.6 mg/kg/24 h, respectively. The BMD z-score changed significantly from −0.763 ± 0.954 (mean ± SD) to −0.537 ± 0.898 (p < 0.0001) before and after treatment, respectively. The BMD z-score of the patients improved with treatment, suggesting a beneficial effect and potential need for treatment. However, the lack of a control group points to the need for future studies to corroborate this outcome.     

Assessment of the Relationship Between Post-meal Satiety, Gastric Volume and Gastric Emptying After Swedish Adjustable Gastric Banding. A Pilot Study Using Magnetic Resonance Imaging to Assess Postsurgery Gastric Function

Background  Swedish adjustable gastric banding (SAGB) is a common weight loss procedure performed worldwide. The exact mechanism by which it achieves appetite suppression, and hence weight loss, is not clear. One possible mechanism is altered meal handling by the post-SAGB stomach. Methods  Five post SAGB patients and five age/sex-matched controls were recruited. Pre- and post-meal magnetic resonance imaging (MRI) was performed with two liquid test meals of differing viscosity—locust bean gum (3.0%) and water. Appetite was assessed using ten-point visual analogue scales. Results  There were significant relationships between hunger scores and esophageal, pouch and residual stomach fluid volume changes for the locust bean gum meal (p = 0.033, 0.043 and 0.011, respectively). The rate constants for gastric emptying were similar in the two groups for both the gum (0.038 ± 0.016 min⁻¹ for SAGB, 0.041 ± 0.032 min⁻¹ for controls, p = 0.44) and water meals (0.068 ± 0.044 min⁻¹ for SAGB, 0.044 ± 0.009 min⁻¹ for controls, p = 0.35). An unexpected finding was asymptomatic esophageal meal retention with the locust bean gum meal in the post-SAGB arm (mean 16.9 ml at 15 min). Conclusions  There is no evidence of differences in volume-dependent gastric emptying between the normal and post-SAGB stomach. Further investigation of the phenomenon of esophageal retention, and its role in post-SAGB satiety, is warranted.     

Intensive Insulin Therapy and Bone Mineral Density in Type 1 Diabetes Mellitus: A Prospective Study

To determine the effect of metabolic control on bone mineral density (BMD) in type 1 diabetes mellitus (type 1 DM), we studied BMD (by dual-energy X-ray energy absorptiometry) and bone remodeling parameters in 62 patients with type 1 DM both before and 7 years after commencement of intensive insulin therapy. Overall outcomes after the 7-year treatment included the stabilization of BMD at all sites, as well as a significant decrease in tartrate-resistant acid phosphatase (TRAP) (4.302 ± 2.62 vs 2.65 ± 0.97 IU/l; p = 0.0001) and increase in intact parathyroid hormone (PTHi) (28.05 ± 15.7 vs 39.78 ± 22.41 ng/l; p = 0.005). Presence of diabetic retinopathy (RTP) versus its absence (non-RTP) was associated with lower BMD in femoral neck (FN) (0.831 ± 0.142 vs 0.756 ± 0.153 mg/cm²; p = 0.03) and Ward’s triangle (WT) (0.736 ± 0.165 vs 0.632 ± 0.172 mg/cm²; p = 0.03), and with a lower T-score in FN (–0.93 ± 1.34 vs –1.70 ± 1.46; p = 0.04) and WT (–0.72 ± 1.42 vs –1.540 ± 1.55; p = 0.04) and Z-score in FN (–0.591 ± 1.23 vs –1.132 ± 1.46; p = 0.01). The percentage of patients with osteopenia or osteoporosis in the RTP group was significantly higher than in the non-RTP group (72% vs 53%, p = 0.05; RR= 3.2) and the glycosylated hemoglobin (HbA1c) levels of the RTP group were also higher (8.53 ± 1.6% vs 7.1 ± 1.1%; p = 0.05). The improvement in metabolic control, increase in body mass index and decrease in resorption parameters could contribute to the stabilization of bone mass in type 1 DM but the presence of retinopathy is a critical factor in the progression of diabetic osteopenia. Received: 4 June 1999 / Accepted: 16 November 1999     

Application of High‐Resolution Skeletal Imaging to Measurements of Volumetric BMD and Skeletal Microarchitecture in Chinese‐American and White Women: Explanation of a Paradox

Asian women have lower rates of hip and forearm fractures despite lower areal BMD (aBMD) by DXA compared with white women and other racial groups. We hypothesized that the lower fracture rates may be explained by more favorable measurements of volumetric BMD (vBMD) and microarchitectural properties, despite lower areal BMD. To address this hypothesis, we used high‐resolution pQCT (HRpQCT), a new method that can provide this information noninvasively. We studied 63 premenopausal Chinese‐American (n = 31) and white (n = 32) women with DXA and HRpQCT. aBMD by DXA did not differ between groups for the lumbar spine (1.017 ± 0.108 versus 1.028 ± 0.152 g/cm²; p = 0.7), total hip (0.910 ± 0.093 versus 0.932 ± 0.134 g/cm²; p = 0.5), femoral neck (0.788 ± 0.083 versus 0.809 ± 0.129 g/cm²; p = 0.4), or one‐third radius (0.691 ± 0.052 versus 0.708 ± 0.047 g/cm²; p = 0.2). HRpQCT at the radius indicated greater trabecular (168 ± 41 versus 137 ± 33 mg HA/cm³; p = <0.01) and cortical (963 ± 46 versus 915 ± 42 mg HA/cm³; p < 0.0001) density; trabecular bone to tissue volume (0.140 ± 0.034 versus 0.114 ± 0.028; p = <0.01); trabecular (0.075 ± 0.013 versus 0.062 ± 0.009 mm; p < 0.0001) and cortical thickness (0.98 ± 0.16 versus 0.80 ± 0.14 mm; p < 0.0001); and lower total bone area (197 ± 34 versus 232 ± 33 mm²; p = <0.001) in the Chinese versus white women and no difference in trabecular number, spacing, or inhomogeneity before adjustment for covariates. Similar results were observed at the weight‐bearing tibia. At the radius, adjustment for covariates did not change the direction or significance of differences except for bone, which became similar between the groups. However, at the tibia, adjustment for covariates attenuated differences in cortical BMD and bone area and accentuated differences in trabecular microarchitecture such that Chinese women additionally had higher trabecular number and lower trabecular spacing, as well as inhomogeneity after adjustment. Using the high‐resolution technology, the results provide a mechanistic explanation for why Chinese women have fewer hip and forearm fractures than white women.