Dual X-ray Absorptiometry Scans Research Articles

Relationship between Body Mass Index and Bone Mineral Density in Saudi Women Above 40 Years with Vitamin D Deficiency

Low body mass index (BMI) causing low bone mineral density (BMD) has been reported in several articles. There are also contradictory data available which shows that obesity is associated with low bone mass. Vitamin D deficiency is a very common problem in Saudi women due to their lifestyle and culture. The present study was conducted to find out the relationship between body mass index and bone mineral density in Saudi women who have vitamin D deficiency. After the Vitamin D level assessment, the patients underwent Dual Energy X-ray Absorptiometry (DEXA) scan. Patients who had hormonal disorders, renal diseases and who were on immunosuppressive drugs were excluded from the study. Among the patients who had Vitamin D deficiency, 42.7 % had normal BMD while 57.3 % had low BMD. The BMD was low in 80% with normal BMI, 74.1% in overweight and 50% in obese patients. There was no statistically significant association between BMI and BMD (P>0.05) although there was a significant association between exercise and BMD (P<0.05) and age and BMD (P<0.05). The results indicate that bone loss and osteoporosis can occur in obese patients above 40 years of age, if they are not having sufficient exercise.

A Novel Ultrasound Methodology for Estimating Spine Mineral Density

We investigated the possible clinical feasibility and accuracy of an innovative ultrasound (US) method for diagnosis of osteoporosis of the spine. A total of 342 female patients (aged 51–60 y) underwent spinal dual X-ray absorptiometry and abdominal echographic scanning of the lumbar spine. Recruited patients were subdivided into a reference database used for US spectral model construction and a study population for repeatability and accuracy evaluation. US images and radiofrequency signals were analyzed via a new fully automatic algorithm that performed a series of spectral and statistical analyses, providing a novel diagnostic parameter called the osteoporosis score (O.S.). If dual X-ray absorptiometry is assumed to be the gold standard reference, the accuracy of O.S.-based diagnoses was 91.1%, with k = 0.859 (p < 0.0001). Significant correlations were also found between O.S.-estimated bone mineral densities and corresponding dual X-ray absorptiometry values, with r2 values up to 0.73 and a root mean square error of 6.3%–9.3%. The results obtained suggest that the proposed method has the potential for future routine application in US-based diagnosis of osteoporosis.

The negative impact of being underweight and weight loss on survival of children with acute lymphoblastic leukemia.

Body mass index and change in body mass index during treatment may influence treatment outcome of pediatric patients with acute lymphoblastic leukemia. However, previous studies in pediatric acute lymphoblastic leukemia reported contradictory results. We prospectively collected data on body composition from a cohort of newly diagnosed Dutch pediatric patients with acute lymphoblastic leukemia (n=762, age 2-17 years). Patients were treated from 1997-2004 and the median follow-up was 9 years (range, 0-10). Body mass index at diagnosis was expressed as age- and gender-matched standard deviation scores and on the basis of these scores the patients were categorized as being underweight, of normal weight or overweight. Multivariate analyses showed that patients who were underweight (8%) had a higher risk of relapse [hazard ratio: 1.88, 95% confidence interval (1.13-3.13)], but similar overall survival and event-free survival as patients who had a normal weight or who were overweight. Patients with loss of body mass index during the first 32 weeks of treatment had a similar risk of relapse and event-free survival, but decreased overall survival [hazard ratio: 2.10, 95% confidence interval (1.14-3.87)] compared to patients without a loss of body mass index. In addition, dual X-ray absorptiometry scans were performed in a nested, single-center cohort. Data from these scans revealed that a loss of body mass consisted mainly of a loss of lean body mass, while there was a gain in the percentage of fat. In conclusion, being underweight at diagnosis is a risk factor for relapse, and a decrease in body mass index early during treatment is associated with decreased survival. In addition, loss of body mass during treatment seems to consist mainly of a loss of lean body mass. This study was approved by the Medical Ethical Committee in 1996 (trial number NTR460/SNWLK-ALL-9).

Validity of Hounsfield Units from computed tomographic images of mandibular bone in detection of osteoporosis

The figure for the clinical application of computed tomography have been increased significantly in oral and maxillofacial field that supply the dentists with sufficient data enables them to play a main role in screening osteoporosis, therefore Hounsfield units of mandibular computed tomography view used as a main indicator to predict general skeleton osteoporosis and fracture risk factor. Material and Methods: Thirty subjects (7 males &23 females) with a mean age of (60.1) years underwent computed tomographic scanning for different diagnostic assessment in head and neck region. The mandibular bone quality of them were determined through Hounsfield units of CT scan images and were correlated with the bone mineral density values obtained from t-scores of lumbar spine using dual x-ray absorptiometry scans (DEXA). Results: There was a highly significant positive correlation (p-value 0.000 (HS)) of bone mineral density that measured by t-score of dual x-ray absorptiometrical scan and Hounsfield units with very strong relation in measuring the bone density (r test) = 0.969, this close relation lead to predict osteoporosity and the chance of fracture occurrence using a statistical equation that classified the patients as osteoporotic. Conclusion: Hounsfield units obtained from computed tomography scans that are made for any purposes can provide an alternative clinical parameter to predict osteoporosis at no additional cost to the patient and no additional radiation.

Prevalence of insulin resistance and risk of diabetes mellitus in HIV-infected patients receiving current antiretroviral drugs.

HIV-infected patients had a higher prevalence of insulin resistance (IR) and risk of diabetes mellitus (DM) than that observed in healthy controls, but there are no data about the current prevalence considering the changes in HIV presentation and the use of newer antiretroviral drugs. Longitudinal study which involved 265 HIV patients without DM, receiving first (n=71) and advanced lines of antiretroviral therapy (n=194). Prevalence of IR according to clinical and anthropometric variables, including dual X-ray absorptiometry (DXA) scan evaluation. IR was defined as homeostasis model assessment of IR≥3.8. Incident DM was assessed during the follow-up. First-line patients had a short time of HIV infection, less hepatitis C virus coinfection, and received mainly an efavirenz-based regimen. Overall, the prevalence of IR was 21% (55 patients, 6% in first-line, 27% in pretreated). In a logistic regression analysis, significant associations were found between the waist/hip circumference ratio (RR 10; 95% CI 1.66-16; P<0.01, per unit), and central fat in percentage (RR 1.08; 95% CI 1.01-1.17; P=0.04, per unit) as evaluated by DXA, and IR. During 770.8 patient-years, DM was diagnosed in 8% (22 patients), mostly in pretreated patients (10 vs 4%; P=0.1). Thus, the overall rate of incident DM was 2.85 per 100 person-years, mostly in previous IR (10.39 vs 0.82/100 person-years; P=0.01). A lower prevalence of IR is observed in the current HIV-infected patients with fewer risk factors and receiving newer antiretroviral drugs. IR continues to identify patients at high risk for developing DM in the short term.

Influence of physical activity and skeleton geometry on bone mass at the proximal femur in 10- to 12-year-old children--a longitudinal study.

Physical activity (PA) have long been identified as a determining factor of the mineralization of the skeleton, particularly in children. Our research supports the hypothesis that the geometry of the pelvis and proximal femur (PF) might moderate the effect of PA in the relative mineralization of the PF subregions. Using a longitudinal observational study with two evaluations and a 1-year follow-up interval, we investigated the influence of PA and skeletal geometry in bone mineral density (BMD) and bone mass distribution at the PF in 96 girls and 81 boys (10-12 years). It is plausible that the geometry of the pelvis-PF structure moderates mechanical forces exerted at the hip and therefore creates different degrees of mineralization among PF subregions. Whole body and left hip dual X-ray absorptiometry scans were used to derive geometric measures of the pelvis-inter-acetabular distance (IAD) and PFabductor lever arm (ALA). BMD was measured at the integral, superolateral (SL), and inferomedial (IM) femoral neck (FN), and at the trochanter (TR). These subregions were used to represent bone mass distribution via three BMD ratios: FN/PF, IM/SL, and TR/PF. PA was measured using accelerometry and a bone-specific PA questionnaire (BPAQ). A longitudinal data approach revealed BPAQ as a positive predictor for all BMD variables (p < 0.05) except TR BMD in girls and FN BMD in boys. Comparing the most active with the less-active participants, the greatest benefits of PA were observed at the FN of the girls with the lowest IAD (p < 0.001), at the FN of the boys with the highest IAD (p < 0.001) and at the TR of the boys with the lowest ALA (p < 0.01). Geometric measures of IAD and ALA seem to moderate the effect of PA role in the relative mineralization of the PF regions. On the other hand, absolute BMD levels appear to be determined by mechanical loading.

Dynamic Interactions of Gas Exchange, Body Mass, and Progressive Exercise in Children

Cardiopulmonary exercise testing (CPET) is increasingly used as a biomarker of fitness in children. Maximal or peak values remain the most common variables obtained in CPET, but these physiologically challenging high-intensity work rates (WR) are often not achieved. We hypothesized that interactions of gas exchange, heart rate (HR), and WR CPET variables (slopes) could yield useful mechanistic and clinical insights that might enhance the clinical utility of CPET in children. We further hypothesized that the dependence of the slope on body mass could be predicted by the first-principle analysis of body size and physiological response. One hundred and sixty-nine healthy participants (8-18 yr old, body mass index <95th percentile, 82 females) underwent dual x-ray absorptiometry scan to estimate lean body mass (LBM) and performed a ramp-type progressive cycle ergometry exercise protocol with a breath-by-breath measurement of gas exchange. Linear regression was used to calculate the slopes among VO2, VCO2, VE, HR, and WR. ΔWR/ΔHR (r = 0.87) and ΔVO2/ΔHR (r = 0.96) were strongly correlated with VO2peak, whereas ΔVO2/ΔWR (r = 0.42) and ΔVE/ΔVCO2 (r = -0.51) were mildly correlated with peak values. LBM was more highly correlated with those slopes predicted to be body size dependent (P < 0.0001) compared with total body mass. The data largely supported our original hypotheses. Unlike peak or maximal values, which are derived from no more than a few data points at the end of a progressive exercise test, the CPET slopes were calculated from a much larger data set obtained throughout the test. An analysis of these slopes might ultimately prove useful clinically and in research studies when peak values are not achieved.

Fracture Liaison Service: Impact on Subsequent Nonvertebral Fracture Incidence and Mortality

A fracture liaison service model of care is widely recommended and applied, but data on its effectiveness are scarce. Therefore, the risk of subsequent nonvertebral fractures and mortality within two years after a nonvertebral fracture was analyzed in patients who presented to a hospital with a fracture liaison service and a hospital without a fracture liaison service. In 2005 to 2006, all consecutive patients with an age of fifty years or older presenting with a nonvertebral fracture were included. In the group that presented to a hospital without a fracture liaison service (the no-FLS group), only standard fracture care procedures were followed to address proper fracture-healing. In the group that presented to a hospital with a fracture liaison service (the FLS group), dual x-ray absorptiometry scans and laboratory testing were performed, and if applicable, patients were treated according to the Dutch guideline for osteoporosis. The risk for subsequent nonvertebral fracture and mortality were analyzed using multivariable Cox regression models with adjustments for age, sex, and baseline fracture location. In total, 1412 patients presented to the fracture liaison service (73.2% were women, and the mean age was 71.1 years), and 1910 underwent standard fracture care (69.8% were women, and the mean age was 69.5 years). After adjustment for age, sex, and baseline fracture location, patients who attended the fracture liaison service had a significantly lower mortality risk (hazard ratio: 0.65; 95% confidence interval [CI]: 0.53 to 0.79) over two years of follow-up. The subsequent nonvertebral fracture risk was also significantly lower in the patients in the FLS group, but this effect was time-dependent, with a hazard ratio of 0.84 (95% CI: 0.64 to 1.10) at twelve months and 0.44 (95% CI: 0.25 to 0.79) at twenty-four months. Patients seen at the fracture liaison service had a significantly lower mortality and subsequently a lower risk of nonvertebral fracture than those not seen at the fracture liaison service, with a reduction of 35% and 56%, respectively, over two years of follow-up. A fracture liaison service appears to be a successful approach to reduce the number of subsequent fractures and premature mortality in this cohort of patients.

Bilateral Iliac Fracture: An Unusual Sequela of Osteoporosis and Spinal Fusion: A Case Report.

Transverse or Chance fractures of the pelvis are extremely rare and do not fit within existing pelvic fracture classifications. Only three have been reported in the literature; all resulted from high-energy motor vehicle accidents1. We describe an unusual fracture pattern in a patient with a prolonged history of bisphosphonate use who experienced a low-energy mechanical fall. The patient was informed that data concerning the case would be submitted for publication, and she provided consent. A fifty-nine-year-old woman with a complicated orthopaedic history, which originated with a spinal fusion for scoliosis at age seventeen, subsequently required multiple lumbar spine operations, including several revision fusions. Prior to the injury that resulted from a low-energy fall, she had been treated with alendronate for nearly fifteen years. Before the injury, the most recent dual x-ray absorptiometry scan was consistent with osteoporosis, with a T score of –3.3 for the proximal aspect of the right femur. The T score had improved from earlier scans, but she still was considerably osteoporotic. After the low-energy fall, the patient was taken to a local hospital where a concussion and the pelvic fractures were noted. There were insufficiency fractures of both iliac wings; the transverse lucencies began at the lower portion of the sacroiliac joints and extended laterally to the region of the iliac tubercles (Figs. 1-A, 1-B, and 1-C). The injuries necessitated a prolonged hospital inpatient admission. She was allowed to bear weight as tolerated after the injury but was admitted to a rehabilitation hospital because of difficulty mobilizing and substantial pain. Initial injury films. The fractures (arrows) are difficult to visualize on the anteroposterior radiograph (Fig. 1-A), but computed tomography (Fig. 1-B and Fig. 1-C) clearly shows the fracture (arrows). Fig. 1-A Fig. 1-B Fig. 1-C The patient was …

Bone density and fractures in autosomal dominant hyper IgE syndrome.

Autosomal Dominant Hyper IgE Recurrent Infection Syndrome (AD-HIES) is caused by mutations in STAT3 and characterized by eczema, recurrent bacterial infections, and skeletal and connective tissue abnormalities. To further understand the minimal trauma fractures of AD-HIES, we examined bone mineral density (BMD) and laboratory markers of bone turnover. Patients with AD-HIES enrolled in a prospective natural history study were examined with dual x-ray absorptiometry (DEXA) scans and laboratory studies of bone metabolism. The number of fractures was recorded as well as clinical features of AD-HIES including scoliosis and retained primary teeth. Patients on medications with skeletal effects, including bisphosphonates, were examined separately. Twenty-three AD-HIES children (6-18 years) and 33 AD-HIES adults (21-50 years) not receiving bone-active drugs were studied. Fourteen of the 23 children (61%) had histories of minimal trauma fractures, as did 26 of the 33 adults (79%). Osteopenia or osteoporosis was found in 79% of children and adults. Only radial BMD correlated with the qualitative occurrence of fractures but it did not correlate with the numbers of fractures. Markers of bone metabolism did not correlate with minimal trauma fractures or BMD. Patients on bone-active medications had improved BMD, but still sustained fractures. Minimal trauma fractures and decreased BMD are common in AD-HIES. Low radial BMD is associated with fractures, but hip and spine BMD are not. Treatment with bisphosphonates increased BMD but its role in fracture prevention remains undefined.

Antiepileptic medications increase osteoporosis risk in male fabry patients: bone mineral density in an Australian cohort.

Fabry disease (FD) is an inherited X-linked lysosomal storage disease with widespread clinical manifestations. Small prospective studies have shown increased osteopenia and osteoporosis in male FD patients. Limited information however exists about bone metabolism and osteoporosis risk factors within this group. We reviewed osteoporosis risk factors within our cohort. A retrospective analysis of bone mineral density (BMD) results and fracture incidence in 44 patients (22 males and 22 females) was undertaken. Dual X-ray absorptiometry scans were performed at the lumbar spine, hip and femoral neck. The impact of risk factors including renal function, antiepileptic drug (AED), analgesia and vitamin D levels were assessed. Male FD patients had low T scores at all sites (spine -1.2 ± 1.06, hip -1.6 ± 0.9, femoral neck -2.23 ± 1.01). Female T scores showed more typical distribution (spine -0.07 ± 1.47, hip 0.02 ± 1.14, femoral neck -0.49 ± 1.31). A higher incidence of osteopenia and/or osteoporosis occurred in males versus females (spine 46.9% versus 31.8%, hip 75.5% versus 18.2% and femoral neck 86.4% versus 45.5%). Multiple regression analysis showed a 50.8% (p < 0.001) reduction in femoral neck BMD with AED usage, after adjustment for age, gender and renal function. Non-traumatic fractures occurred in 27.3% males over 205 patient-years versus 4.6% in females over 149 patient-years, p = 0.095. Low bone density was highly prevalent in male patients with increased incidence of non-traumatic fractures. AED usage significantly reduces BMD. Treatment to prevent BMD deterioration will depend on determining the bone turnover status.

Effects of recreational soccer in men with prostate cancer undergoing androgen deprivation therapy: study protocol for the 'FC Prostate' randomized controlled trial.

BackgroundAndrogen deprivation therapy (ADT) is a cornerstone in the treatment of advanced prostate cancer. Adverse musculoskeletal and cardiovascular effects of ADT are widely reported and investigations into the potential of exercise to ameliorate the effects of treatment are warranted. The ‘Football Club (FC) Prostate’ study is a randomized trial comparing the effects of soccer training with standard treatment approaches on body composition, cardiovascular function, physical function parameters, glucose tolerance, bone health, and patient-reported outcomes in men undergoing ADT for prostate cancer.Methods/DesignUsing a single-center randomized controlled design, 80 men with histologically confirmed locally advanced or disseminated prostate cancer undergoing ADT for 6 months or more at The Copenhagen University Hospital will be enrolled on this trial. After baseline assessments eligible participants will be randomly assigned to a soccer training group or a control group receiving usual care. The soccer intervention will consist of 12 weeks of training 2–3 times/week for 45–60 min after which the assessment protocol will be repeated. Soccer training will then continue bi-weekly for an additional 20 weeks at the end of which all measures will be repeated to allow for additional analyses of long-term effects. The primary endpoint is changes in lean body mass from baseline to 12 weeks assessed by dual X-ray absorptiometry scan. Secondary endpoints include changes of cardiovascular, metabolic, and physical function parameters, as well as markers of bone metabolism and patient-reported outcomes.DiscussionThe FC Prostate trial will assess the safety and efficacy of a novel soccer-training approach to cancer rehabilitation on a number of clinically important health outcomes in men with advanced prostate cancer during ADT. The results may pave the way for innovative, community-based interventions in the approach to treating prostate cancer.Trial registrationClinicalTrials.gov: NCT01711892

Which factors prognosticate rotational instability following lumbar laminectomy?

Reduced strength and stiffness of lumbar spinal motion segments following laminectomy may lead to instability. Factors that predict shear biomechanical properties of the lumbar spine were previously published. The purpose of the present study was to predict spinal torsion biomechanical properties with and without laminectomy from a total of 21 imaging parameters. Radiographs and MRI of ten human cadaveric lumbar spines (mean age 75.5, range 59-88 years) were obtained to quantify geometry and degeneration of the motion segments. Additionally, dual X-ray absorptiometry (DXA) scans were performed to measure bone mineral content and density. Facet-sparing lumbar laminectomy was performed either on L2 or L4. Spinal motion segments were dissected (L2-L3 and L4-L5) and tested in torsion, under 1,600 N axial compression. Torsion moment to failure (TMF), early torsion stiffness (ETS, at 20-40 % TMF) and late torsion stiffness (LTS, at 60-80 % TMF) were determined and bivariate correlations with all parameters were established. For dichotomized parameters, independent-sample t tests were used. Univariate analyses showed that a range of geometric characteristics and disc and bone quality parameters were associated with torsion biomechanical properties of lumbar segments. Multivariate models showed that ETS, LTS and TMF could be predicted for segments without laminectomy (r (2) values 0.693, 0.610 and 0.452, respectively) and with laminectomy (r (2) values 0.952, 0.871 and 0.932, respectively), with DXA-derived measures of bone quality and quantity as the main predictors. Vertebral bone content and geometry, i.e. intervertebral disc width, frontal area and facet joint tropism, were found to be strong predictors of ETS, LTS and TMF following laminectomy, suggesting that these variables could predict the possible development of post-operative rotational instability following lumbar laminectomy. Proposed diagnostic parameters might aid surgical decision-making when deciding upon the use of instrumentation techniques.

A Biomechanical Comparison of One-Third Tubular Plates Versus Periarticular Plates for Fixation of Osteoporotic Distal Fibula Fractures

The purpose of this study was to test the biomechanical properties of locking and nonlocking plates using one-third tubular and periarticular plate designs in an osteoporotic distal fibula fracture model. Twenty-four cadaveric specimens, whose bone mineral densities were obtained using dual x-ray absorptiometry scans, were tested. The fracture model simulated an OTA 44-B2.1 fracture. The constructs included (1) nonlocking one-third tubular plate, (2) locking one-third tubular plate, (3) nonlocking periarticular plate, and (4) locking periarticular plate. The specimens underwent axial loading followed by torsional loading to failure. Statistical analysis was performed using Kruskal-Wallis testing and further analysis with Mann-Whitney testing. The periarticular plates had greater rotational stiffness compared with the one-third tubular plates (P = 0.04). The nonlocking plates had greater torque to failure than the locking plates (P = 0.01). The nonlocking one-third tubular plate had greater torque to failure than the locking one-third tubular plate (P = 0.03). No significant differences were found in any of the comparisons regarding axial stiffness. In biomechanical testing using an osteoporotic model of OTA 44-B2.1 fractures, periarticular plates were superior to one-third tubular plates in rotational stiffness only. Locking plates did not outperform their nonlocking counterparts. Periarticular plates should be considered when treating osteoporotic distal fibula fractures, but one-third tubular plates and nonlocking plates provide adequate fixation for these injuries.

Vitamin D Deficiency and Low Bone Mineral Density in Pediatric and Young Adult Intestinal Failure

The aim of the present study was to determine the prevalence and predisposing factors for vitamin D deficiency and low bone mineral density (BMD) in patients with intestinal failure (IF). A retrospective review of patients with IF managed at the Cincinnati Children's Hospital Medical Center. IF was defined as history of parenteral nutrition (PN) >30 days. Vitamin D deficiency was defined as serum 25-hydroxyvitamin D (25 (OH) D) <20 ng/dL. Reduced BMD was defined using dual x-ray absorptiometry z score ≤-2. A binary logistic regression model was used to test for association of significant risk factors and the outcome variables after univariate analyses. One hundred and twenty-three patients with median age of 4 years (range 3-22 years) were evaluated. Forty-nine (39.8%) patients had at least a documented serum 25 (OH) D deficiency during the study interval, whereas 10 of 80 patients (12.5%) with dual x-ray absorptiometry scans completed had a low BMD z score. Age at study entry was associated with both 25 (OH) D deficiency (P = 0.01) and low BMD z score (P = 0.03). Exclusive PN at study entry was associated with reduced bone mass (P = 0.03). There was no significant association between vitamin D deficiency and low BMD z score (P = 0.31). The risk of 25 (OH) D deficiency and low BMD z score increases with age among patients with IF. Strategies for monitoring and preventing abnormal bone health in older children receiving exclusive PN need to be developed and evaluated.

Childhood socioeconomic status and adult femoral neck bone strength: Findings from the Midlife in the United States Study

PurposeBone acquisition in childhood impacts adult bone mass, and can be influenced by childhood socioeconomic conditions. Socioeconomic status is also associated with body weight which affects the load that bone is exposed to in a fall. We hypothesized that socioeconomic advantage in childhood is associated with greater bone strength relative to load in adulthood. MethodsHip dual x-ray absorptiometry scans from 722 participants in the Midlife in the United States Study were used to measure femoral neck size and bone mineral density, and combined with body weight and height to create composite indices of femoral neck strength relative to load in different failure modes: compression, bending, and impact. A childhood socioeconomic advantage score was created for the same participants from parental education, self-rated financial status relative to others, and not being on welfare. Multiple linear regression was used to determine the association of childhood socioeconomic advantage with femoral neck composite strength indices, stratified by gender and race (white/non-white), and adjusted for study site, age, menopause status in women, education, and current financial advantage. ResultsChildhood socioeconomic advantage was independently associated with higher indices of all three composite strength indices in white men (adjusted standardized effect sizes, 0.19 to 0.27, all p values<0.01), but not in the other three race/gender groups. Additional adjustment for adult obesity, physical activity in different life stages, smoking, and heavy drinking over the life-course significantly attenuated the associations in white men. ConclusionsSocioeconomic disadvantage in childhood is associated with lower hip strength relative to load in white men, and these influences are dampened by healthy lifestyle choices.

Recovery of Decreased Bone Mineral Mass After Lower-Limb Fractures in Adolescents

Loss of bone mineral mass, muscle atrophy, and functional limitations are predictable consequences of immobilization and subsequent weight-bearing restriction due to leg or ankle fractures. The aim of this study was to prospectively determine whether decreased bone mineral mass following lower-limb fractures recovers at follow-up durations of six and eighteen months in adolescents. In the present study, we included fifty adolescents who underwent cast immobilization for a leg or ankle fracture. Dual x-ray absorptiometry scans of four different sites (total hip, femoral neck, entire lower limb, and calcaneus) were performed at the time of the fracture, at cast removal, and at follow-ups of six and eighteen months. Patients with fractures were paired with healthy controls according to sex, age, and ethnicity. Dual x-ray absorptiometry values were compared between groups and between injured and non-injured legs in adolescents with fractures. Among those with fractures, lower-limb bone mineral variables were significantly lower at the injured side compared with the non-injured side at cast removal, with differences ranging from 6.2% to 31.7% (p &lt; 0.0001). Similarly, injured adolescents had significantly lower bone mineral values at the level of the injured lower limb compared with healthy controls (p &lt; 0.0001). At the six-month follow-up, there were still significant residual differences between injured and non-injured legs in adolescents with fractures (p &lt; 0.0001). However, a significant residual difference between healthy controls and injured adolescents was present only for femoral neck bone mineral density (p = 0.011). At the eighteen-month follow-up, no significant difference was observed at any lower-limb site. Bone mineral loss following a fracture of the lower limb in adolescents is highly significant and affects the lower limb both proximal to and distal to the fracture site. In contrast to observations in adults, a rapid bone mass reversal occurs with full bone recovery by eighteen months. Prognostic Level I. See Instructions for Authors for a complete description of levels of evidence.

Numerical simulation of load-induced bone structural remodelling using stress-limit criterion

A simple and efficient numerical method for predicting the remodelling of adaptive materials and structures under applied loading was presented and implemented within a finite element framework. The model uses the trajectorial architecture theory of optimisation to predict the remodelling of material microstructure and structural organisation under mechanical loading. We used the proposed model to calculate the density distribution of proximal femur in the frontal plane. The loading considered was the hip joint contact forces and muscular forces at the attachment sites of the muscles to the bone. These forces were estimated from a separate finite element calculation using a heterogeneous three-dimensional model of the proximal femur. The density distributions obtained by this procedure has a qualitative similarity with in vivo observations. Solutions displayed the characteristic high-density channels that are evident in the Dual X-ray Absorptiometry scan. There is also evidence of the intramedullary canal, as well as low-density regions in the femoral neck. Several parametric studies were carried out to highlight the advantages of the proposed method, which includes fast convergence and low-computational cost. The potential applications of the proposed method in predicting bone structural remodelling in cancer are also briefly discussed.

Use of dual X-ray absorptiometry to measure body mass during short- to medium-term trials of nutrition and exercise interventions

Dual X-ray absorptiometry (DXA) has a range of clinical applications, from assessing associations between adipose or lean body mass and the risk of disease to measuring the effects of dietary interventions on adipose deposition and oxidation and/or muscle accumulation. Many lifestyle-related studies, however, are short- to medium-term interventions, and inter- or intradevice variation between DXA scanners can facilitate type I and type II errors during data analysis. Studies demonstrate that variation in body composition measurements exist not only between DXA instruments using fan-beam and pencil-beam technologies but also between DXA instruments produced by different manufacturers. Moreover, studies show inter- and intrainstrument variation between identical DXA instruments. Such inter- and intrascan variability between instruments can be compounded by the particular patient population being investigated. The objective of this review is to discuss inter- and intradevice variation of DXA instruments and to outline quality control procedures that should be implemented prior to initiating short-term single or multicenter clinical trials that use DXA to investigate the effects of an intervention on loss or accretion of lean or fat mass.

Porous Tantalum Tibial Component Prevents Periprosthetic Loss of Bone Mineral Density After Total Knee Arthroplasty for Five Years—A Matched Cohort Study

In 21 knees receiving porous tantalum tibial component and 21 knees receiving a cemented cobalt-chromium tibial component, dual x-ray absorptiometry scans were performed for five years post-operatively. The postoperative decrease in the bone mineral density in the lateral aspect of the tibia was significantly less in knees with porous tantalum tibial components (11.6%) than in knees with cemented cobalt-chromium tibial components (29.6%) at five years (p < 0.05). No prosthetic migration or periprosthetic fracture was detected in either group. The present study is one of the studies with the longest follow-up period on bone mineral density after total knee arthroplasty. Porous tantalum tibial component has a favorable effect on the bone mineral density of the proximal tibia after total knee arthroplasty up to five years.