Bone mineral density in the lumbar spine as determined by dual-energy X-ray absorptiometry. Comparison of whole-body scans and dedicated regional scans

A 20-week exercise program improved total body and legs bone mineral density in children with overweight or obesity: The ActiveBrains randomized controlled trial

OBJECTIVES

The aim of this study was to investigate the effect of a 20-week exercise program on bone mineral parameters in children with overweight or obesity.

DESIGN

Randomized controlled trial.

METHODS

This study took part from November 21, 2014, to June 30, 2016, in Granada, Spain. A secondary analysis of this parallel-group randomized controlled trial was performed with 77 children with overweight or obesity (9.9 ± 1.2, 65 % boys) who were randomly allocated to exercise or control group. All participants received lifestyle recommendations. The control group continued their usual routines, whereas the exercise group attended a minimum of 3 supervised 90-minute sessions/week of aerobic plus resistance training for 20 weeks. A whole-body scan by dual-energy X-ray absorptiometry was carried out to obtain body composition at total body less head, arms, lumbar spine, pelvis, and legs.

RESULTS

Participants in the exercise group acquired significantly higher total body aBMD (mean z-score [95 % confidence intervals, CI], 0.607 [0.522-0.692]) compared with the participants in the control group (mean z-score, 0.472 [0.388-0.556]); difference between groups, 0.135 standard deviations [95 % CI 0.015-0.255], and legs aBMD (mean z-score, 0.629 [0.550-0.708]); control group (mean z-score, 0.518 [0.440-0.596]); difference between groups, 0.111 [0.001-0.222]; all p < 0.05. There were no significant differences between exercise group and control group at the remaining evaluated regions (p > 0.05).

CONCLUSIONS

A 20-week non-specifically bone-targeted exercise program induced a small, yet significant, improvement on total body and legs aBMD in children with overweight or obesity. Future studies should investigate the interaction of weight status in the bone response to exercise programs.

TRIAL REGISTRATION

Prospectively registered in ClinicalTrials.gov Identifier: NCT02295072.

Liver Fat, Bone Marrow Adipose Tissue, and Bone Mineral Density in Children With Overweight

CONTEXT

Hepatic steatosis is associated with decreased bone mineral density (BMD). Bone marrow fat fraction (BMFF) could play a role in this relationship in children with obesity.

OBJECTIVE

The objectives of this work were (i) to examine the relationship between the lumbar spine (LS) BMFF and BMD, and (ii) to explore the mediating role of LS-BMFF on the relationship between percentage hepatic fat with LS-BMD in preadolescent children with overweight/obesity.

METHODS

Hepatic fat and LS-BMFF (magnetic resonance imaging) and areal LS-BMD (LS-aBMD, dual-energy x-ray absorptiometry) were measured in 106 children (aged 10.6 ± 1.1 years, 53.8% girls) with overweight/obesity.

RESULTS

LS-BMFF was inversely associated with LS-aBMD (r = -0.313; P = .001) and directly related with percentage hepatic fat (r = 0.276; P = .005). LS-BMFF was significantly greater in children with than without hepatic steatosis (P = .003; Cohen's d: 0.61; 95% CI, -0.21 to 1.0), while no significant difference was seen between children with overweight and those with obesity (P = .604; Cohen's d: 0.16; 95% CI, -0.21-0.55). Mediating analysis indicated that LS-BMFF is an important mediator (50%) in the association of hepatic fat with lower LS-aBMD (indirect effect: β = -.076; 95% CI, -0.143 to -0.015).

CONCLUSION

These findings suggest that hepatic steatosis, rather than overall excess adiposity, is associated with greater bone marrow adipose tissue in preadolescent children with overweight/obesity, which in turn, is related to lower BMD. Hepatic steatosis could be a potential biomarker of osteoporosis risk, and a therapeutic target for interventions that aim to reduce not only hepatic steatosis, but for those designed to improve bone health in such children.

BMDs Derived From Total Body DXA are Strongly Correlated With Dedicated Hip and Spine BMD and are Associated With Prior Fractures in NHANES

Dedicated dual energy X-ray absorptiometry (DXA) bone mineral density (BMD) of the hip and spine are strongly associated with fractures, but it is not clear whether total body (TB) DXA measures correlate with dedicated DXA or relate to fractures. Using National Health and Nutrition Examination Survey (NHANES) data from years 2013-2014 and 2017-2018, we assessed Pearson correlations between dedicated and TB DXA measures. Associations with fractures were examined using self-reported prior fractures or fractures found on vertebral fracture assessment (VFA) using logistic regression models while controlling for age, gender, race/ethnicity, and body mass index. Among 1418 subjects from NHANES 2013-2014, we found signification correlations between all dedicated DXA BMD and TB DXA BMD measures. For dedicated spine BMD, the TB site with the strongest correlation was TB lumbar spine (r = 0.87, p < 0.001), while for dedicated total hip and femoral neck BMD, total body, pelvis, leg, and trunk BMD had the strongest correlations (r = 0.67-0.75, p < 0.001 for all). There were relatively few differences by sex or race/ethnicity. Findings were similar in 481 subjects from NHANES 2017-2018. In NHANES 2013-2014, there were 438 prior fractures in 370 subjects (26.3%). When controlling for age, gender, race/ethnicity, and body mass index, the adjusted odds ratio for fracture per T-score decrease of BMD were similar for TB BMD measures as for dedicated BMD measures (OR 1.10-1.28). In conclusion, total body DXA measures are correlated with hip and spine DXA and are strongly associated with prior fracture. Our results suggest that total body DXA measures are valid alternative sites to study BMD and fracture risk.

Leptin levels were negatively associated with lumbar spine bone mineral content in children with overweight or obesity

AIM

Adipokines seem to play a role in bone morphogenesis, although this also depends on the mechanical forces applied to the skeleton. The aim was to assess the relationships of resting leptin and adiponectin with bone parameters and whether high muscular fitness levels affect these relationships in children with overweight or obesity.

METHODS

This cross-sectional study took part from 2014 to 2016 in Granada, Spain. Participants were recruited from University Hospitals, and we also used advertisements in local media and school contacts in the city. Adipokines were analysed in plasma. Muscular fitness was assessed by 1 repetition maximum in bench and leg press tests. Dual-energy X-ray absorptiometry was used to measure bone parameters.

RESULTS

We included 84 children (10.0±1.2y; 63% boys) in this analysis. Leptin was negatively associated with lumbar spine bone mineral content (β=-0.162, p=0.053). No significant interaction was found for muscular fitness. Simple slope estimates suggested that children performing more than 133.3kg in leg press test ameliorated the negative association between leptin and lumbar spine bone mineral content.

CONCLUSION

Leptin levels were negatively associated with lumbar spine bone mineral content in children with overweight or obesity. A high muscular fitness at the lower body could counteract this association.

Thoracic Quantitative Computed Tomography (QCT) Can Sensitively Monitor Bone Mineral Metabolism: Comparison of Thoracic QCT vs Lumbar QCT and Dual-energy X-ray Absorptiometry in Detection of Age-relative Change in Bone Mineral Density

RATIONALE AND OBJECTIVE

Sensitive detection of bone mineral density (BMD) change is a key issue to monitor and evaluate the individual bone health status, as well as bone metabolism and bone mineral status. The ability to use thoracic quantitative computed tomography (QCT) to detect the annual change of BMD remains unclear. We aimed to investigate the sensitivity in detecting age-related bone mineral loss using the thoracic QCT from the electrocardiographically gated heart scans in comparison to whole-body dual-energy X-ray absorptiometry (DXA) and standard lumbar QCT.

MATERIALS AND METHODS

A total of 121 asymptomatic patients' imaging data, including DXA whole body scan, cardiac CT scan, and abdomen scans were analyzed. The BMD of the thoracolumbar spine, upper, and lower extremities were measured using QCT and DXA, respectively. The age-related annual rate of bone density loss was computed and compared to the thoracic and lumbar QCT, as well DXA measures.

RESULTS

The age-related annual rate of bone loss with QCT was -0.70 mg/mL³ (-0.75%/y) in women, -0.83 mg/mL³ (-0.86%/y) in men in the thoracic and the lumbar trabecular QCT, respectively. Compared to the QCT, DXA demonstrates a lower annual rate of bone loss in the area of BMD measurement (P < .05 in all, excluding legs of women) in -0.45, -0.42, -0.67, and -0.46 in women, in -0.32, -0.02, -0.12, and -0.08 in men for thoracic, lumbar, leg, and arm, respectively.

CONCLUSION

We conclude that the thoracic and the lumbar QCT provide a similar and more sensitive method for detecting bone mineral loss when compared to DXA.

Low bone mineral status in adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis (AIS) is a pathological entity of unknown etiology. The causes of osteoporosis or osteopenia in AIS remain undetermined. Whether poor bone quality is an etiologic factor remains controversial. To determine the correlation between low bone mineral status and AIS, a review of literature was performed. After a literature search from 1966 to June 2007 (using Medline, EMBASE, Cochrane DSR, ACP Journal Club, DARE, CCTR, CINAHL and hand searches of references) for studies regarding low bone mineral status and AIS, 20 studies meeting the inclusion criteria were reviewed in terms of the appropriateness of valuation technique, the validity of descriptive system, the number and type of respondents, and overall quality of the studies. Nearly all investigations demonstrated that low bone mineral density (BMD) was a generalized phenomenon and a systematic disorder in AIS. The prevalence of AIS with osteoporosis is approximately 20-38%. The follow-up studies indicated that osteopenia in patients with AIS may be a persistent phenomenon. BMD could be affected by the mechanical loading and lower bone mineral mass is always associated with lower bone strength. The spinal architecture associated with the osteopenia may aggravate the spinal deformity. However, with regard to the concave and convex femoral neck BMD values, and the correlation of BMD to scoliosis parameters, the results remain inconsistent. Bracing may not result in permanent loss of bone mineral mass. The effect of the eccentric tension-compression environments on BMD, the correlation of BMD with scoliosis parameters and the effect of bracing on BMD should be investigated further in prospective, randomized and longitudinal follow-up studies.

Osteoporosis assessment by whole body region vs. site-specific DXA

The ability of regional data from whole body scans to provide an accurate assessment of site-specific BMD, osteoporosis prevalence and fracture risk has not been fully explored. To address these issues, we measured total body (TBBD) and site-specific BMD in an age-stratified population sample of 351 women (21-93 years) and 348 men (22-90 years). We found an excellent correlation between AP lumbar spine and total body lumbar spine subregion BMD (r2=0.92), but weaker ones for total hip compared to pelvis region (r2=0.72) or between total wrist and left arm subregion from the whole body scan (r2=0.83). The error in estimating site-specific BMD from total body regions ranged from 4.3% (lumbar spine) to 11.2% (femoral neck) in women and from 4.9 to 11.1%, respectively, in men. Site-specific versus regional measurements at the lumbar spine and total hip/pelvis provided comparable overall estimates of osteoporosis prevalence, but disagreed on the status of individuals; measurements at whole body regions underestimated osteoporosis as assessed at the femoral neck or total wrist. All measurements were associated with a history of various fractures [age adjusted odds ratios (OR), 1.3 to 2.1 in women and 1.2 to 1.5 in men] and were generally interchangeable, but femoral neck BMD provided the best estimate of osteoporotic fracture risk in women (OR, 2.9; 95% CI, 1.7-5.0). Although there are strong correlations between BMD from dedicated scans of the hip, spine and distal forearm and corresponding regions on the whole body scan, the measurements provide somewhat different estimates of osteoporosis prevalence and fracture risk.

Assessment of bone mass following renal transplantation in children

Throughout childhood and adolescence, skeletal growth results in site-specific increases in trabecular and cortical dimensions and density. Childhood osteoporosis can be defined as a skeletal disorder characterized by compromised bone strength predisposing to an increased risk of fracture. Pediatric renal transplant recipients have multiple risk factors for impaired bone density and bone strength, including pre-existing renal osteodystrophy, delayed growth and development, malnutrition, decreased weight-bearing activity, inflammation, and immunosuppressive therapies. Dual energy X-ray absorptiometry (DXA) is the most-common method for the assessment of skeletal status in children and adults. However, DXA has many important limitations that are unique to the assessment of bone health in children. Furthermore, DXA is limited in its ability to distinguish between the distinct, and sometimes opposing, effects of renal disease on cortical and trabecular bone. This review summarizes these limitations and the difficulties in assessing and interpreting bone measures in pediatric transplantation are highlighted in a review of select studies. Alternative strategies are presented for clinical and research applications.

Interpretation of whole body dual energy X-ray absorptiometry measures in children: comparison with peripheral quantitative computed tomography

The assessment of bone health in children requires strategies to minimize the confounding effects of bone size on dual energy X-ray absorptiometry (DXA) areal bone mineral density (BMD) results. Cortical bone composes 80% of the total skeletal bone mass. The objective of this study was to develop analytic strategies for the assessment of whole body DXA that describe the biomechanical characteristics of cortical bone across a wide range of body sizes using peripheral quantitative computed tomography (pQCT) measures of cortical geometry, density (mg/mm(3)), and strength as the gold standard. Whole body DXA (Hologic QDR 4500) and pQCT (Stratec XCT-2000) of the tibia diaphysis were completed in 150 healthy children 6-21 years of age. To assess DXA and pQCT measures relative to age, body size, and bone size, gender-specific regression models were used to establish z scores for DXA bone mineral content (BMC) for age, areal BMD for age, bone area for height, bone area for lean mass, BMC for height, BMC for lean mass, and BMC for bone area; and for pQCT, bone cross-sectional area (CSA) for tibia length and bone strength (stress-strain index, SSI) for tibia length. DXA bone area for height and BMC for height were both strongly and positively associated with pQCT CSA for length and with SSI for length (all P < 0.0001), suggesting that decreases in DXA bone area for height or DXA BMC for height represent narrower bones with less resistance to bending. DXA BMC for age (P < 0.01) and areal BMD (P < 0.05) for age were moderately correlated with strength. Neither DXA bone area for lean mass nor BMC for lean mass correlated with pQCT CSA for length or SSI for length. DXA BMC for bone area was weakly associated with pQCT SSI for length, in females only. Therefore, normalizing whole body DXA bone area for height and BMC for height provided the best measures of bone dimensions and strength. DXA BMC normalized for bone area and lean mass were poor indicators of bone strength.

Bone mass after treatment of malignant lymphoma in childhood

BACKGROUND

Sex hormone deficiency, growth hormone deficiency, skeletal irradiation, and treatment with corticosteroids or methotrexate may all cause reduction in bone mass after treatment for childhood malignant lymphoma. Previous studies of the bone mass of childhood cancer survivors often lacked adequate local reference data, and survivors of malignant lymphoma were never analyzed separately.

PROCEDURE

The bone mass of survivors of childhood Hodgkin disease (n = 23) or non-Hodgkin lymphoma (n = 21) was measured by dual-energy X-ray absorptiometry a median of 11 years after diagnosis (range 2-25). Results were compared with local data on 463 healthy controls.

RESULTS

Adjusted for gender and age, the mean whole-body bone mineral content and bone mineral areal density were slightly, but significantly, reduced (0.5 and 0.4 SD lower than predicted). The reduced bone mineral content was associated with a significantly reduced height, whereas the size-adjusted bone mass (bone mineral content for bone area) did not differ significantly from that of controls. Lower height was related to male gender and to cranial, thoracic, and lumbar spine irradiation. Whole-body bone mineral content and bone mineral density were lower in persons treated with lumbar spine irradiation and whole-body bone mineral content was higher in nine women receiving sex hormone replacement therapy or oral contraceptives. Whole-body bone mass was not related to the cumulated doses of corticosteroids or methotrexate.

CONCLUSIONS

Eleven years after diagnosis of childhood Hodgkin disease or non-Hodgkin lymphoma, the whole-body bone mass of survivors was only slightly reduced and the size-adjusted bone mass was normal.

Comparison of absorptiometric evaluations from total-body and local-regional skeletal scans

The most common measurement sites for dual-energy absorptiometry (DXA) in clinical practice are posteroanterior (PA) spine and femur. However, other skeletal regions may provide different bone density information. The purpose of this study was to establish the least number of DXA measurements needed to obtain complete information about bone. A total of 262 normal female subjects, 8-50, were measured on a Lunar DPX-L scanner under total body, PA spine, lateral spine, and femur protocol. Forearm measurements were performed with a Lunar SP2 single-photon absorptiometry scanner. The various measurements were compared based on a linear regression model. The correlation coefficients for bone mineral density (BMD) between adjacent vertebrae were 0.92-0.95, and the associated standard errors of the estimate (SEE) were 4.5-5.5%. Total-body BMD can best predict BMD of the trunk, arms, and legs (SEE<4.3%), but least that of the lateral view of the spine (SEE>13.9%). BMD values of the leg from total-body scans predict those from the femoral neck with an error of 9.0%, and those of the trochanteric region with 11.1%. The error between adjacent vertebrae (6%) is considered acceptable, then a total-body measurement combined with a lateral view of the spine and a femur scan are adequate.

Bone mass after allogeneic BMT for childhood leukaemia or lymphoma

The bone mass was measured by dual energy X-ray absorptiometry in 25 survivors of childhood leukaemia or lymphoma (21 with ALL) who had received TBI and allogeneic BMT a median of 8 years ago (range 4-13). Results were compared with local data on 463 healthy controls and 95 survivors of childhood ALL treated without BMT. Adjusted for sex and age, the mean whole-body bone mineral content (BMC) and bone mineral areal density were significantly less than in healthy controls (0.8 and 0.5 s.d. less than predicted). The reduced BMC was caused by a significantly reduced height for age, whereas bone area for height and BMC for bone area were similar to controls. Less bone mass tended to be related to additional cranial irradiation and age above 20 years at follow-up. Controlled for this, the whole-body bone mass seemed to be unrelated to previous chemotherapy and endocrine status at follow-up and tended to be only marginally less in BMT patients than in ALL survivors treated without BMT. In conclusion, 8 years after allogeneic BMT for childhood leukaemia or lymphoma, the whole-body bone mass was only slightly reduced and the size-adjusted bone mass (BMC for bone area) was normal. Bone Marrow Transplantation (2000) 25, 191-196.