Occupational Activity and Bone Mineral Density in Postmenopausal Women in England

Few studies have assessed the relationship between occupational activity and bone mineral density (BMD), although two case–control studies have reported a protective effect of occupational activity on hip fracture. In the present study 580 postmenopausal women aged 45–61 years completed a risk factor questionnaire including a detailed occupational history. For each job, hours spent sitting, standing, walking, lifting and carrying were recorded; these measures, evaluated at ages 20, 30, 40 years, in the current job and over the working lifetime, were used in the analysis. BMD was measured with dual-energy X-ray absorptiometry, and measurements at five sites were used in a multiple regression analysis adjusting for potential confounding variables. There was a significant negative association between sitting at age 20 years and BMD at the radius (p= 0.037), with negative relationships of borderline significance at the anteroposterior spine (p = 0.091) and whole body (p= 0.078). There were significant positive associations between standing at age 30 years and BMD at all five sites (p<0.05), but no significant linear associations for standing at ages 20 and 40 years. No significant associations were found for lifetime or current occupational measures of sitting, standing, walking and lifting or carrying. The lack of consistency of these significant findings suggests that they may have occurred by chance, and that occupational activity has little if any effect on BMD in postmenopausal women. Received: 12 March 1999 / Accepted: 17 September 1999     

Annual change in bone mineral density in predialysis patients with chronic renal failure: significance of a decrease in serum 1,25-dihydroxy-vitamin D

Bone disease occurs in the predialysis phase of chronic renal failure (CRF). The aim of this study was to examine how a decrease in renal function affects annual bone mineral density (BMD) changes in predialysis CRF patients and to examine the factors that affect BMD. The BMD of the distal radius in 53 predialysis CRF patients (age, 61.3 ± 10.8 years; serum creatinine 2.7 ± 1.2 mg/dl) was measured by peripheral quantitative computed tomography (pQCT) twice with a 1-year interval. The total BMD of the radius significantly decreased over a year (P < 0.001), and both trabecular and cortical BMD showed a significant decrease. Significant positive correlations with BMD changes were found for estimated creatinine clearance (r = 0.375, P < 0.01) and baseline serum 1,25(OH)₂D (r = 0.434, P < 0.005), indicating that BMD decreased to a greater extent with larger reductions in creatinine clearance and serum 1,25(OH)₂D. Of several bone metabolic markers examined, baseline serum osteocalcin was significantly positively correlated with annual BMD changes (r = −0.276, P < 0.05). Multiple regression analysis showed that baseline serum 1,25(OH)₂D (β = 0.434) was a significant predictor of decreases in total and trabecular BMD (R ² = 0.188, P < 0.01; and R ² = 0.207, P < 0.01), independent of other confounding factors. These results indicate that BMD decreases as renal function deteriorates in predialysis CRF patients, and that osteocalcin is a clinically useful marker associated with the decrease in BMD. The serum 1,25(OH)₂D level is the principal factor affecting BMD of the radius, suggesting that supplementation with an active form of vitamin D is of importance for predialysis CRF patients.     

Alterations of bone mineral density of the femurs in hemiplegia

We evaluated the bone mineral density (BMD) of the bilateral femurs in 112 patients with hemiplegia using dual-energy X-ray absorptiometry in order to elucidate the effect of disuse and immobilization. BMD of the paretic side was significantly reduced compared with that of the nonparetic side in hemiplegic patients (femoral neck 0.582±0.014 g/cm² versus 0.623±0.014 g/cm² and total femur 0.645±0.02 g/cm² versus 0.702±0.017 g/cm²; mean±SEM, P<0.01, respectively). Femoral BMD in both the paretic and nonparetic limb had significantly (P<0.01) lower values than in age- and sex-matched controls, but the paretic side had a more significant reduction of BMD; femoral neck-20% versus -14% and total femur -24% versus -18%. In addition, patients with impaired activities of daily living (ADL), evaluated by a mobility score, had significantly decreased BMD ratios of paretic/nonparetic side than patients with improved ADL (femoral neck 91% versus 97%, P<0.01 and total femur 89% versus 94%, P<0.05). Our results indicated that BMD of both femurs of patients with hemiplegia was reduced, although the paretic side showed a greater BMD decrease. This decrease might be prevented or reduced by improvement of ADL.     

Bone mineral status in paraplegic patients who do or do not perform standing

Bone mineral density (BMD) was assessed by dual-photon X-ray absorptiometry at the lumbar spine (L3, L4), the proximal femur and the femoral shaft, and by single-photon absorptiometry at the forearm in 53 patients with complete traumatic paraplegia of at least 1 year's duration and in age- and sex-matched healthy controls. The patients did (n=38) or did not (n=15) regularly perform passive weightbearing standing with the aid of a standing device. Compared with the controls, the BMD of paraplegic patients was preserved in the lumbar spine and was markedly decreased in the proximal femur (33%) and the femoral shaft (25%). When considering all patients performing standing, they had a better-preserved BMD at the femoral shaft (p=0.009), but not at the proximal femur, than patients not performing standing. BMD at the lumbar spine (L3,L4) was marginally higher in the standing group (significant only for L3;p=0.040). A subgroup of patients performing standing with use of long leg braces had a significantly higher BMD at the proximal femur than patients using a standing frame or a standing wheelchair (p=0.030). The present results suggest that passive mechanical loading can have a beneficial effect on the preservation of bone mass in osteoporosis found in paraplegics.     

Trabecular Bone Structure Analysis in the Osteoporotic Spine Using a Clinical In Vivo Setup for 64‐Slice MDCT Imaging: Comparison to μCT Imaging and μFE Modeling

Assessment of trabecular microarchitecture may improve estimation of biomechanical strength, but visualization of trabecular bone structure in vivo is challenging. We tested the feasibility of assessing trabecular microarchitecture in the spine using multidetector CT (MDCT) on intact human cadavers in an experimental in vivo–like setup. BMD, bone structure (e.g., bone volume/total volume = BV/TV; trabecular thickness = Tb.Th; structure model index = SMI) and bone texture parameters were evaluated in 45 lumbar vertebral bodies using MDCT (mean in‐plane pixel size, 274 μm²; slice thickness, 500 μm). These measures were correlated with structure measures assessed with μCT at an isotropic spatial resolution of 16 μm and to microfinite element models (μFE) of apparent modulus and stiffness. MDCT‐derived BMD and structure measures showed significant correlations to the density and structure obtained by μCT (BMD, R² = 0.86, p < 0.0001; BV/TV, R² = 0.64, p < 0.0001; Tb.Th, R² = 0.36, p < 0.01). When comparing μCT‐derived measures with μFE models, the following correlations (p < 0.001) were found for apparent modulus and stiffness, respectively: BMD (R² = 0.58 and 0.66), BV/TV (R² = 0.44 and 0.58), and SMI (R² = 0.44 and 0.49). However, the overall highest correlation (p < 0.001) with μFE app. modulus (R² = 0.75) and stiffness (R² = 0.76) was achieved by the combination of QCT‐derived BMD with the bone texture measure Minkowski Dimension. In summary, although still limited by its spatial resolution, trabecular bone structure assessment using MDCT is overall feasible. However, when comparing with μFE‐derived bone properties, BMD is superior compared with single parameters for microarchitecture, and correlations further improve when combining with texture measures.     

Effect of cavity preparation and bone mineral density on bone‐interface densification and bone‐implant contact during press‐fit implantation of hip stems

Implant loosening and periprosthetic fracture are two major revision causes for uncemented hip stems. The chosen method of cavity preparation could play a key role for both failure mechanisms. The aim of this study was to determine the dependence of the broach type as well as patient bone mineral density (BMD) on densification and contact conditions at the bone‐implant interface. Hip stems were implanted into cadaveric femora using compaction, blunt extraction or sharp extraction broaches with computed tomography scans performed prior to broaching, after broaching and after stem implantation. Proximal periprosthetic bone densification as well as press‐fit, contact area and stem seating relative to the last broach were determined. Median bone densification was higher with the compaction and blunt extraction broaches compared to sharp extraction broaches (181% and 177%, respectively, p = 0.002). The bone densification of femora prepared with compaction broaching increased with higher BMD (R² = 0.183, p = 0.037), while stem seating decreased with higher BMD for all broach types (R² = 0.259, p = 0.001). Incomplete seated prostheses were associated with smaller press‐fit and bone‐implant contact area (R² = 0.249, p = 0.001; R² = 0.287, p < 0.001). Clinical Significance: The results suggest that compaction broaching maximizes bone densification in patients with higher bone density. However, there appears to be an increased risk of insufficient stem seating in high‐density bone that could limit the benefits for primary stability. For lower quality bone, the broach type appears to play a lesser role, but care must be taken to limit extensive stem seating which might increase periprosthetic fracture risk. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1580–1589, 2019.     

Sex Differences in Bone Size and Bone Mineral Density Exist before Puberty. The Copenhagen School Child Intervention Study (CoSCIS)

Background The aim of this study was to provide normative data of bone mineral density (BMD; g/cm²) of the forearm and the calcaneus, evaluated by peripheral dual X ray absorbtiometry (DXA), in children aged 6 to 7 years of age and to evaluate the association with anthropometrics and sex. Material and methods 368 boys and 326 girls with a mean age of 6.7 ± 0.4 years participated. BMD was measured by DXA in the forearms and the os calcanei, with average values presented in this report. Measurements of weight, height, skinfolds, the width of distal radius and ulna, and the femur condyles were collected and body composition estimated from skinfolds measurements. Results There was no difference in calcaneus BMD when comparing boys and girls, whereas the boys had 4.5% (0.013 g/cm²) higher forearm BMD than the girls (P < 0.001). Calcaneal BMD (mean 0.318 g/cm²) was 11% higher than forearm BMD (mean 0.283 g/cm²). Linear relationship was found between calcaneus BMD and weight (partial r = 0.50), Fat free mass (FFM) (partial r = 0.50), Fat mass (FM) (partial r = 0.45), % body fat (partial r = 0.29) and knee width (partial r = 0.46), all P < 0.000 respectively. Adjusted for weight the relationship between calcaneus BMD and FFM, FM, %body fat and knee width disappeared. There were significant relationships between the forearm BMD and weight (partial r = 0.37), FFM (partial r = 0.39), FM (partial r = 0.28), %body fat (partial r = 0.14) and wrist width (partial r = 0.24), all P < 0.000 respectively. Adjusted for body weight, the relationship remained between forearm BMD and FFM (r = 0.10), FM (R = −0.10) and % body fat (r = −0.12), all P < 0.000 respectively. Children measured in the spring had 3.5% (P < 0.01) higher calcaneus BMD than children measured in the winter. Conclusion Seven year old boys have higher BMD in the forearm but not in the calcaneus in comparison with girls of a similar age. Body weight is the best predictor of calcaneus BMD, accounting for 25% of the variance whereas body weight and FFM are the best predictors of forearm BMD, each accounting for 17% of the variance, respectively.     

Does Vitamin D Strengthen the Increase in Femoral Neck BMD in Osteoporotic Women Treated with Estrogen?

The long-term effects on bone of estrogen therapy (HRT) combined with vitamin D₃ supplementation were evaluated and compared with the effects of HRT without vitamin D₃ supplementation in a 4-year prospective, partly randomized study among 60 osteoporotic women (mean age 55.4 years; range 49.7–59.4 years). The women studied were a subgroup of the population-based Kuopio Osteoporosis Risk Factor and Prevention Study (OSTPRE) (n = 13100). The bone mineral densities (BMD) of the lumbar spine and femoral neck were determined by dual-energy X-ray absorptiometry (DXA) in 3236 perimenopausal women. Those 106 women with baseline BMD more than 2 SDs less than the mean value in this population, either at the lumbar spine (BMD < 0.826 g/cm²) and/or femoral neck (BMD < 0.684 g/cm²), were offered treatment for osteoporosis. After exclusions, 60 women were included in the analyses. Group allocation was: HRT (estradiol valerate (2 mg) plus cyproterone acetate, 1 mg, sequentially: Climen^R) (n = 21); HRT + Vit D: Climen + vitamin D₃ (cholecalciferol, 300 IU/day, no intake during June–August) (n = 23); controls: 16 women who refused all treatment served as a non-randomized control group. In the HRT group, the highly significant increase in lumbar BMD was 5.4%, 5.3%, 4.7% and 4.0% after 1, 2, 3 and 4 years of treatment, respectively, all compared with the baseline values and with the control group. The increase in femoral neck BMD was statistically insignificant (1.4%, 2.2%, 1.9% and 2.1%, respectively; p > 0.05). In the HRT + Vit D group, the lumbar BMD increased by 3.7%, 4.9%, 4.9% and 4.9% (p < 0.001), whereas the 5.8% increase in femoral neck BMD reached significance at 4 years (p < 0.01) when compared with the control group as well as with the baseline values. However, there were no statistically significant differences in lumbar or femoral BMD changes between the two HRT groups. In conclusion, estrogen can substantially increase lumbar bone mass in patients with postmenopausal osteoporosis. In addition, the combination of HRT and vitamin D₃ may increase femoral neck BMD in osteoporotic women more than estrogen alone.     

Relationship between leg bone mineral values and muscle strength in women with different physical activity

This study examines whether knee extensor muscle isometric, isokinetic, and isoinertial strength values in women with different physical activity and body composition patterns are related to leg bone mineral density (BMD) and bone mineral content (BMC) values. A total of 129 women aged 17–40 participated in this study. They were divided into four groups: strength-trained (n = 33), endurance-trained (n = 32), normal weight sedentary (n = 41), and overweight sedentary (n = 23) women. In addition, the subjects were grouped as physically active (n = 65) or sedentary (n = 64) women. BMD and BMC for both legs (LBMD and LBMC, respectively) and for the dominant leg alone (DLBMC), body fat percentage and lean body mass (LBM), maximal knee extension isometric (ISOM) and isokinetic (ISOK) strength at the angular velocity of 60 deg·s⁻¹, and isoinertial leg explosive strengths (countermovement jump CMJ) were measured. In endurance-trained women, LBMD was dependent on body mass index (BMI) (33.7% of the variance, R² × 100), and in the physically active group and the total group with LBM (14.6% and 15.6%, respectively). In the overweight group, LBMD was dependent on ISOK strength (21.7% of the variance, R² × 100). In the sedentary and total groups, ISOM strength was more important (10.3% and 5.0%, respectively); in the strength-trained group, body weight influenced LBMC, accounting for 71.6% of the variance (R² × 100). In the endurance-trained women, height influenced LMBC (37.9%, R² × 100). In sedentary and overweight women, LBM accounted for 52.1% and 61.4% of the total variance in LBMC. In these groups, ISOM strength accounted for 15.3% and 25.9% of the variance in LBMC. In overweight women, ISOM and ISOK strength together influenced LBMC highly (64.8% of the variance, R² × 100). In the sedentary group, the influence of LBM on LBMC was higher than in the active group (82.1% and 50.5% of the variance, respectively). In the total group, LBM influenced LBMC, accounting for 54.5% of the variance (R² × 100). ISOM strength (22.7%) alone or in combination with ISOK strength (35.8%) and CMJ (41.7%) (R² × 100) in LBMC in the sedentary group explained the variance. In the total group, ISOM strength alone (13.2%) or in combination with CMJ (17.1%) influenced LBMC (R² × 100). Our results suggest that (1) muscle strength and anthropometrical parameters were associated with LBMD; (2) LBM and ISOM strength had a significant relationship with DLBMC and LBMC only in nonathletic women; and (3) strength measured with different regimens highly influenced LBMC compared with LBMD, especially in the sedentary groups.     

Effects of Two Years of Daily Teriparatide Treatment on BMD in Postmenopausal Women With Severe Osteoporosis With and Without Prior Antiresorptive Treatment

Previous antiresorptive (AR) treatment may influence the response to teriparatide. We examined BMD response and safety in a subgroup of 503 postmenopausal women with osteoporosis who received teriparatide for 24 mo. Patients were divided into three groups based on their prior AR treatment: treatment‐naïve (n = 84); pretreated with no evidence of inadequate treatment response (n = 134); and pretreated showing an inadequate response to AR treatment (n = 285), which was predefined based on the occurrence of fractures, persistent low BMD, and/or significant BMD loss while on therapy. Changes in BMD from baseline were analyzed using mixed model repeated measures. Lumbar spine BMD increased significantly from baseline at 6, 12, 18, and 24 mo in all three groups. The mean gain in spine BMD over 24 mo was greater in the treatment‐naïve group (0.095 g/cm²; 13.1%) than in the AR pretreated (0.074 g/cm²; 10.2%; p < 0.005) and inadequate AR responder (0.071 g/cm²; 9.8%; p < 0.001) groups. The corresponding increases in total hip BMD were 3.8%, 2.3%, and 2.3%, respectively. Early decreases in hip BMD in the inadequate AR responder group were reversed by 18 mo of treatment. Increases in BMD between 18 and 24 mo were highly significant. Nausea (13.3%) and arthralgia (11.7%) were the most commonly reported adverse events. Asymptomatic hypercalcemia was reported in 5.0% of patients. Teriparatide treatment for 24 mo is associated with a significant increase in BMD in patients with and without previous AR use. Prior AR treatment modestly blunted the BMD response to teriparatide. Safety was consistent with current prescribing label information.     

Vertebral Strength and Estimated Fracture Risk Across the BMI Spectrum in Women

Somewhat paradoxically, fracture risk, which depends on applied loads and bone strength, is elevated in both anorexia nervosa and obesity at certain skeletal sites. Factor‐of‐risk (Φ), the ratio of applied load to bone strength, is a biomechanically based method to estimate fracture risk; theoretically, higher Φ reflects increased fracture risk. We estimated vertebral strength (linear combination of integral volumetric bone mineral density [Int.vBMD] and cross‐sectional area from quantitative computed tomography [QCT]), vertebral compressive loads, and Φ at L₄ in 176 women (65 anorexia nervosa, 45 lean controls, and 66 obese). Using biomechanical models, applied loads were estimated for: 1) standing; 2) arms flexed 90°, holding 5 kg in each hand (holding); 3) 45° trunk flexion, 5 kg in each hand (lifting); 4) 20° trunk right lateral bend, 10 kg in right hand (bending). We also investigated associations of Int.vBMD and vertebral strength with lean mass (from dual‐energy X‐ray absorptiometry [DXA]) and visceral adipose tissue (VAT, from QCT). Women with anorexia nervosa had lower, whereas obese women had similar, Int.vBMD and estimated vertebral strength compared with controls. Vertebral loads were highest in obesity and lowest in anorexia nervosa for standing, holding, and lifting (p < 0.0001) but were highest in anorexia nervosa for bending (p < 0.02). Obese women had highest Φ for standing and lifting, whereas women with anorexia nervosa had highest Φ for bending (p < 0.0001). Obese and anorexia nervosa subjects had higher Φ for holding than controls (p < 0.03). Int.vBMD and estimated vertebral strength were associated positively with lean mass (R = 0.28 to 0.45, p ≤ 0.0001) in all groups combined and negatively with VAT (R = –[0.36 to 0.38], p < 0.003) within the obese group. Therefore, women with anorexia nervosa had higher estimated vertebral fracture risk (Φ) for holding and bending because of inferior vertebral strength. Despite similar vertebral strength as controls, obese women had higher vertebral fracture risk for standing, holding, and lifting because of higher applied loads from higher body weight. Examining the load‐to‐strength ratio helps explain increased fracture risk in both low‐weight and obese women. © 2015 American Society for Bone and Mineral Research.     

Inverse association of serum long-acting natriuretic peptide and bone mineral density in renal transplant recipients

Hsu B‐G, Ho G‐J, Lee C‐J, Yang Y‐C, Chen Y‐C, Shih M‐H, Lee M‐C. Inverse association of serum long‐acting natriuretic peptide and bone mineral density in renal transplant recipients.
Clin Transplant 2011 DOI: 10.1111/j.1399‐0012.2011.01575.x.
© 2011 John Wiley & Sons A/S. Abstract: Objective: Our aim was to evaluate the relationship between bone mineral density (BMD) and fasting serum long‐acting natriuretic peptide (LANP) concentration in renal transplant recipients. Patients and methods: Fasting blood samples were obtained from 65 renal transplant recipients. BMD was measured using dual energy X‐ray absorptiometry in lumbar vertebrae (L2–L4). Serum LANP levels were measured using a commercial enzyme immunoassay kit. Results: Six patients (9.2%) had osteoporosis and 28 patients (43.1%) had osteopenia in renal transplant recipients. Increased serum LANP (p < 0.001) was significantly correlated with low lumbar T‐score cut‐off points between groups (normal, osteopenia, and osteoporosis) in renal transplant recipients. Female patients had lower lumbar BMD than male renal transplant recipients (p = 0.027). Univariate linear regression analysis indicated that lumbar BMD were positively correlated with height (p = 0.038), body weight (p = 0.003), and body mass index (BMI; p = 0.019), whereas negatively correlated with LANP (p = 0.004) among the renal transplant recipients. Multivariate forward stepwise linear regression analysis of the significant variables revealed that body weight (R² change = 0.132; p = 0.006) and LANP (R² change = 0.093; p = 0.008) were the independent predictors of lumbar BMD values in the renal transplant recipients. Conclusion: Serum LANP concentration correlates negatively with lumbar BMD values in renal transplant recipients.     

Association between height loss and bone loss, cumulative incidence of vertebral fractures and future quality of life: the Miyama study

Introduction The study aimed to clarify associations between height loss, bone loss and the quality of life (QOL) score among general inhabitants of Miyama, a rural Japanese community. This population-based epidemiological study was conducted in Miyama, a village located in a mountain area in Wakayama Prefecture, Japan. Methods A list of all inhabitants comprising 1,543 inhabitants (716 men, 827 women) born in this village between 1910–1949 was compiled. From the above whole cohort, a subcohort to measure bone mineral density (BMD) was recruited, consisting of 400 participants, divided into four groups of 50 men and 50 women each, and stratified into age decades by decade of birth-year (1910–1919, 1920–1929, 1930–1939 or 1940–1949). BMD measurement, physical measurements of height (cm) and body weight (kg) were taken, and body mass index (BMI; kg/m²) were calculated. BMD and anthropometric measurements were repeated on the same participants at 3, 7 and 10 years after baseline measurement (1993, 1997 and 2000). Results and discussion Among 299 of 400 participants, changes in height over 10 years for men in their 40s, 50s, 60s and 70s were −0.7 cm, −0.5 cm, −1.2 cm and −1.5 cm, respectively, compared with −0.7 cm, −1.4 cm, −2.1 cm and −3.7 cm in women, respectively. No significant relationships between change in height and rate of change in BMD at the lumbar spine and femoral neck after adjustment for age in men (lumbar spine, β = 0.058, standard error of the mean (SE) = 0.031, P = 0.501, R² = 0.038; femoral neck, β = 0.100, SE = 0.038, P = 0.228, R² = 0.121) were identified. By contrast, among women, a significant positive association was identified between height change and change rate of BMD at the lumbar spine after adjusting for age (β = 0.221, SE = 0.039, P = 0.012, R² = 0.069), while no significant relationship was found between height change and change rate at the femoral neck (β = 0.107, SE = 0.039, P = 0.229, R² = 0.048). No significant relationship was noted between vertebral fractures (VFx) and height at baseline in men and women (men: odds ratio (OR) 0.93, 95% confidence interval (CI) 0.81–1.05, P = 0.24; women: OR 0.97, 95% CI 0.87–1.08, P = 0.58) or between VFx and height loss (men: OR 1.31, 95% CI 1.00–1.71, P = 0.051; women: OR 1.20, 95% CI 0.94–1.53, P = 0.14). In both men and women, no significant relationship was identified between utility of the EuroQol EQ5D questionnaire and height at baseline (men: β = −0.148, SE = 0.003, P = 0.202, R² = 0.076; women: β = 0.127, SE = 0.004, P = 0.235, R² = 0.048), and height change (men: β = −0.078, SE = 0.008, P = 0.452, R² = 0.065; women: β = 0.053, SE = 0.010, P = 0.608, R² = 0.038).     

Factors Underlying Changes in Bone Mineral During Postpartum Amenorrhea and Lactation

To determine the physiologic and habitual factors that may modulate changes in bone mineral density (BMD) postpartum, dual-energy X-ray absorptiometry was performed at the lumbar spine, right femoral neck and dominant distal radius immediately after delivery, after resumption of menses, and 1 year thereafter in a cohort of 41 healthy postpartum Finnish women aged 31.5 (SD 4.6) years. Mean durations of lactation and postpartum amenorrhea (PPA) were 7.7 (3.7) and 5.9 (2.9) months, respectively. After PPA, significant bone losses of 2%–4% were observed at the lumbar spine and femoral neck. Duration of PPA and different lactational variables explained (adjusted R ²) from 21% to 27% of the variability in changes in BMD during PPA. A recovery to postpregnancy BMD levels was observed at the lumbar spine; in contrast BMD at the femoral neck showed only a partial recovery. The duration of unsupplemented lactation was weakly (adjusted R ²= 0.13) associated with recovery at the lumbar spine, while a long duration of total lactation also showed a weak association (adjusted R ²= 0.02) with delayed recovery at the femoral neck. In conclusion, a systematic bone loss occurs during PPA, and after resumption of menstruation BMD recovers despite continued lactation. However, the time of bony recovery back to postpregnancy level seems to be modulated slightly by lactation habits. It is obvious that the control of postpartum BMD changes is a multifactorial process that may be specific to the skeletal site of interest. Received: 7 June 1999 / Accepted: 5 January 2000     

Naturally Occurring Stable Calcium Isotope Ratios in Body Compartments Provide a Novel Biomarker of Bone Mineral Balance in Children and Young Adults

Serum calcium (Ca), bone biomarkers, and radiological imaging do not allow accurate evaluation of bone mineral balance (BMB), a key determinant of bone mineral density (BMD) and fracture risk. We studied naturally occurring stable (non-radioactive) Ca isotopes in different body pools as a potential biomarker of BMB. ⁴²Ca and ⁴⁴Ca are absorbed from our diet and sequestered into different body compartments following kinetic principles of isotope fractionation; isotopically light ⁴²Ca is preferentially incorporated into bone, whereas heavier ⁴⁴Ca preferentially remains in blood and is excreted in urine and feces. Their ratio (δ^44/42Ca) in serum and urine increases during bone formation and decreases with bone resorption. In 117 healthy participants, we measured Ca isotopes, biomarkers, and BMD by dual-energy X-ray absorptiometry (DXA) and tibial peripheral quantitative CT (pQCT). ⁴⁴Ca and ⁴²Ca were measured by multi-collector ionization-coupled plasma mass-spectrometry in serum, urine, and feces. The relationship between bone Ca gain and loss was calculated using a compartment model. δ^44/42Ca_serum and δ^44/42Ca_urine were higher in children (n = 66, median age 13 years) compared with adults (n = 51, median age 28 years; p < 0.0001 and p = 0.008, respectively). δ^44/42Ca_serum increased with height in boys (p < 0.001, R² = 0.65) and was greatest at Tanner stage 4. δ^44/42Ca_serum correlated positively with biomarkers of bone formation (25-hydroxyvitaminD [p < 0.0001, R² = 0.37] and alkaline phosphatase [p = 0.009, R² = 0.18]) and negatively with bone resorption marker parathyroid hormone (PTH; p = 0.03, R² = 0.13). δ^44/42Ca_serum strongly positively correlated with tibial cortical BMD Z-score (n = 62; p < 0.001, R² = 0.39) but not DXA. Independent predictors of tibial cortical BMD Z-score were δ^44/42Ca_serum (p = 0.004, β = 0.37), 25-hydroxyvitaminD (p = 0.04, β = 0.19) and PTH (p = 0.03, β = −0.13), together predicting 76% of variability. In conclusion, naturally occurring Ca isotope ratios in different body compartments may provide a novel, non-invasive method of assessing bone mineralization. Defining an accurate biomarker of BMB could form the basis of future studies investigating Ca dynamics in disease states and the impact of treatments that affect bone homeostasis. © 2020 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).     

Adduction moment increases with age in healthy obese individuals

There is a need to understand how obesity and aging interact to cause an increased risk of medial knee osteoarthritis (OA). This study tested whether the knee adduction and flexion moments increase with age in healthy normal‐weight and obese adults, as well as the mechanism of this increase. We analyzed whether ground reaction force magnitude, knee alignment, step width, toe‐out angle, body volume distribution, and limb position (knee position relative to the pelvis center) are associated with the adduction moment and whether these variables also change with age. Ninety‐six healthy volunteers (60 normal‐weight and 36 obese) were tested using marker‐based gait analysis; knee alignment was based on marker positions during quiet standing. Adduction moment increased with age in obese (R² = 0.19), but not in normal‐weight individuals (R² = 0.01); knee flexion moment did not change with age in either group. In the obese, only knee alignment and limb position were related to the adduction moment (R² = 0.19 and 0.51), but only limb position changed with age (R² = 0.26). The resulting increase in adduction moment suggests greater medial compartment loads, which may combine with elevated levels of inflammation to contribute to the increased risk of medial OA in this population. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1414–1422, 2013     

Temporal Trends in Obesity,Osteoporosis Treatment,Bone Mineral Density,and Fracture Rates: A Population‐Based Historical Cohort Study

Diverging international trends in fracture rates have been observed, with most reports showing that fracture rates have stabilized or decreased in North American and many European populations. We studied two complementary population‐based historical cohorts from the Province of Manitoba, Canada (1996–2006) to determine whether declining osteoporotic fracture rates in Canada are attributable to trends in obesity, osteoporosis treatment, or bone mineral density (BMD). The Population Fracture Registry included women aged 50 years and older with major osteoporotic fractures, and was used to assess impact of changes in osteoporosis treatment. The BMD Registry included all women aged 50 years and older undergoing BMD tests, and was used to assess impact of changes in obesity and BMD. Model‐based estimates of temporal changes in fracture rates (Fracture Registry) were calculated. Temporal changes in obesity and BMD and their association with fracture rates (BMD Registry) were estimated. In the Fracture Registry (n = 27,341), fracture rates declined 1.6% per year (95% confidence interval [CI], 1.3% to 2.0%). Although osteoporosis treatment increased from 5.6% to 17.4%, the decline in fractures was independent of osteoporosis treatment. In the BMD Registry (n = 36,587), obesity increased from 12.7% to 27.4%. Femoral neck BMD increased 0.52% per year and lumbar spine BMD increased 0.32% per year after covariate adjustment (p < 0.001). Major osteoporotic fracture rates decreased in models that did not include femoral neck BMD (fully adjusted annual change –1.8%; 95% CI, –2.9 to –0.5), but adjusting for femoral neck BMD accounted for the observed reduction (annual change –0.5%; 95% CI, –1.8 to +1.0). In summary, major osteoporotic fracture rates declined substantially and linearly from 1996 to 2006, and this was explained by improvements in BMD rather than greater rates of obesity or osteoporosis treatment. © 2014 American Society for Bone and Mineral Research.     

Subpixel Enhancement of Nonuniform Tissue (SPENT): A Novel MRI Technique for Quantifying BMD

BMD is commonly obtained with DXA, but this is confounded by the length and composition of tissues that the X‐ray must traverse. Subpixel enhancement of nonuniform tissue (SPENT) is a novel MRI technique that can provide (direction specific) information based on the subvoxel structural uniformity of a sample. We hypothesized that the SPENT signal would be related to BMD. This hypothesis was tested using (1) 2D computer simulation of a simplified bone structure and (2) in vitro experiments. Simulation results suggested that a resolution of 610–800 μm was required for SPENT to be correlated well with the simulated bone volume fraction (BVF) and, at this resolution, a modest signal‐to‐noise ratio (SNR > 5) was required for reasonable data quality. For the experiments, 15‐mm³ human trabecular bone samples were used (1) to quantify BMD (through both physical measurement and DXA) and (2) to perform MRI on a 7T system. Standard and SPENT images were obtained. Normalized SPENT (NSPENT) images were calculated by pixel‐by‐pixel division of the SPENT images by the standard proton density images to remove any dependence on proton density and coil uniformity from the SPENT images. The average NSPENT values were determined over the sample volume and compared with the reference BMD measurements. Each of the individual NSPENT directions was highly correlated with BMD (x‐NSPENT, R² = 0.73, p < 0.001; y‐NSPENT, R² = 0.76, p < 0.001; z‐NSPENT, R² = 0.89, p < 0.001). With all three individual NSPENT directions combined, the correlation with BMD was found to be the highest (xyz‐NSPENT, R² = 0.95, p < 0.001). The results suggest that the SPENT technique can provide a noninvasive measure of BMD at resolution and SNR levels achievable in vivo.     

Correlations Among Bone Mineral Density,Broadband Ultrasound Attenuation,Mechanical Indentation Testing,and Bone Orientation in Bovine Femoral Neck Samples

Broadband ultrasound attenuation (BUA) of the calcaneus has been found to correlate with bone mineral density (BMD) of the femoral neck. The purpose of this study was to determine if a correlation exists among femoral neck BUA, femoral neck BMD, and incremental indent depth, a qualitative indicator of local mechanical bone strength, in bovine samples, and if this correlation is dependent upon orientation. For 12 of the bovine samples obtained, BUA was measured at the femoral neck and was followed by a BMD determination of the same area. A 19 mm diameter bicortical core containing the center of the area of interest was removed, transversely cut into 7 mm, thick disks, and tested for hardness by indent depth. For these tests, BMD was well correlated with BUA (R²= 0.85, P < 0.001). An inversely proportional relationship with a modest correlation was found between indent depth and BMD (R²= 0.59, P= 0.026), and indent depth and BUA (R²= 0.57, P= 0.031). In a second set of tests involving 15 different bovine samples, a bicortical core was removed from the femoral neck. A trabecular bone cube measuring 1.5 cm on a side was removed from the center of the core. BUA and BMD measurements were made along the anterior–posterior (AP), medial–lateral (ML), and cephalic–caudal (CC) aspects of the cube. The cubes were randomly separated into three groups, cut in half perpendicular to the axis of interest, and tested for hardness by indent depth. In these tests, no significant difference was found in BMD among the three orientations of the cubes scanned (P= 0.77). In contrast, the BUA along the ML orientation of the cube was significantly greater than that along the AP orientation (P < 0.05). No significant difference was found in the incremental indent depth measurements among cube orientations (P= 0.41). In the test involving only trabecular bone, a much higher correlation between BMD and incremental indent depth was found regardless of cube orientation (R²= 0.64, P < 0.001). The data indicate that BUA, but not BMD, is affected by trabecular orientation, and that BMD is negatively correlated with incremental indent depth. Received: 18 July 1995 / Accepted: 19 July 1996     

Effects of gastric bypass procedures on bone mineral density,calcium, parathyroid hormone,and vitamin d

Weight loss after gastric bypass procedures has been well studied, but the long-term metabolic sequelae are not known. Data on bone mineral density (BMD), calcium, parathyroid hormone, and vitamin D were collected preoperatively and at yearly intervals after gastric bypass procedures. A total of 230 patients underwent preoperative BMD scans. Fifteen patients were osteopenic preoperatively, and three patients subsequently developed osteopenia postoperatively within the first year. No patient had or developed osteoporosis. At 1 year, total forearm BMD decreased by 0.55% (n = 91; P = .03) and radius BMD had increased overall by 1.85% (n = 23; P = .008); both total hip and lumbar spine BMD decreased by 9.27% (n = 22; P < .001) and 4.53% (n = 31; P < .001), respectively. By the second postoperative year, BMD in the total forearm had decreased an additional 3.62% (n = 14; P<.001), whereas radius BMD remained unchanged. Although total hip and lumbar spine BMD significantly decreased at 1 year, by year 2 both total hip and lumbar spine BMD only slightly decreased and were not significantly different from before the operation. Serum calcium decreased from 9.8 mg/dL to 9.2 during the first year (not significant [NS]) and then to 8.8 (NS) by the second year. Parathyroid hormone increased from 59.7 pg/mL (nl 10-65 pg/mL) preoperatively to 63.1 during year 1 (NS) and continued to increase to 64.7 by year 2 (NS). No difference was noted among levels of 25-hydroxy vitamin D preoperatively (25.2 ng/mL; nl 10-65 ng/mL), at 1 year (34.4), and at 2 years (35.4). Our data indicate that bone loss is highest in the first year after gastric bypass with stabilization, and that, in some cases, there is an increase in bone density after the first year. Presented at the Forty-Sixth Annual Meeting of The Society for Surgery of the Alimentary Tract, Chicago, Illinois, May 14–18, 2005 (oral presentation).