Accuracy of cortical and trabecular bone measurements with peripheral quantitative computed tomography (pQCT)

Differences in vertebral bone density between African apes

OBJECTIVES

Low-energy vertebral fractures are a common health concern, especially in elderly people. Interestingly, African apes do not seem to experience as many vertebral fractures and the low-energy ones are even rarer. One potential explanation for this difference is the lower bone density in humans. Yet, only limited research has been done on the vertebral bone density of the great apes and these have mainly included only single vertebrae. Hence the study aim is to expand our understanding of the vertebral microstructure of African apes in multiple spinal segments.

MATERIALS

Bone density in the vertebral body of C7, T12, and L3 was measured from 32 Pan troglodytes and 26 Gorilla gorilla using peripheral quantitative computed tomography (pQCT).

RESULTS

There was a clear difference between the three individual vertebrae and consequently the spinal segments in terms of trabecular density and cortical density and thickness. The variation of these bone parameters between the vertebrae differed between the apes but was also different from those reported for humans. The chimpanzees were observed to have overall higher trabecular density, but gorillas had higher cortical density and thickness. Cortical thickness had a relatively strong association with the vertebral size.

DISCUSSION

Despite the similarity in locomotion and posture, the results show slight differences in the bone parameters and their variation between spinal segments in African apes. This variation also differs from humans and appears to indicate a complex influence of locomotion, posture, and body size on the different spinal segments.

Trabecular bone morphology in big cats reflects the complex diversity of limb use but not home range size or daily travel distance

A relationship exists between mechanical loading and bone morphology. Although studies show a relationship between trabecular bone morphology and locomotor strategy in mammals, none of them have studied trabecular bone morphology in felid species occupying disparate and overlapping habitats. We investigate trabecular bone volume fraction (BVF) in the femoral and humeral heads, and distal tibia of four felid species (mountain lions, jaguars, cheetahs, and leopards) to identify whether there is a relationship between BVF and locomotor behavior. This study's goals are to identify whether felid species with high daily travel distance or large home range size have greater BVF compared with those with small daily travel distance or home range size, and whether BVF is correlated among the three elements of the fore and hindlimb studied. We quantified BVF in micro- and peripheral computed tomography images and found no significant differences across species in the femoral and humeral head (p > 0.05). However, in the distal tibia, results showed that leopards, mountain lions, and cheetahs have significantly greater (p < 0.05) BVF than jaguars. Despite differences in home range size and daily travel distance, the proximal elements did not reflect differences in BVF; however, the distal-most element did, suggesting decreased loading among jaguars. These findings suggest that the observed pattern of trabecular bone morphology is potentially due to the diversity in locomotor strategy of the forelimb. Additionally, these results imply that neither home range size nor daily travel distance are clear indicators of activity levels. A cautious approach is warranted in studying how loading influences trabecular morphology.

The relationship between circulating hormone levels, bone turnover markers and skeletal development in healthy boys differs according to maturation stage

INTRODUCTION

This study investigates peri-pubertal changes in bone turnover markers, Wnt-signalling markers, insulin-like growth factor-1 (IGF-1) and sex steroid levels, and how they reflect skeletal development in peri-pubertal boys.

MATERIALS AND METHODS

Population-based study in 118 peri-pubertal boys from the NINIOS cohort (age range at baseline 5.1-17.3 years) with repeated measurements at baseline and after two years. Serum levels of the classical bone turnover markers (BTM) procollagen type 1 N-terminal propeptide and carboxy-terminal collagen crosslinks, as well as sex-hormone binding globulin, IGF-1, osteoprotegerin, sclerostin and dickkopf-1 were measured using immunoassays. Sex steroids (estradiol, testosterone, and androstenedione) were measured using mass spectrometry and free fractions calculated. Dual energy x-ray absorptiometry was used for bone measurements at the lumbar spine and whole body. Volumetric bone parameters and bone geometry at the proximal and distal radius were assessed by peripheral QCT. Pubertal development was categorized based on Tanner staging.

RESULTS

During puberty, sex steroid and IGF-1-levels along with most parameters of bone mass and bone size increased every next Tanner stage. In contrast, classical bone turnover markers and sclerostin peaked around mid-puberty, with subsequent declines towards adult values in late puberty. Especially classical BTM and sex steroid levels showed consistent associations with areal and volumetric bone parameters and bone geometry. However, observed associations differed markedly according to pubertal stage and skeletal site.

CONCLUSION

Serum levels of sex steroids, IGF-1 and bone metabolism markers reflect skeletal development in peri-pubertal boys. However, skeletal development during puberty is nonlinear, and the relations between skeletal indices and hormonal parameters are nonlinear as well, and dependent on the respective maturation stage and skeletal site.

Can neck fractures in proximal humeri be predicted by CT-based FEA?

BACKGROUND

Proximal humeri fractures at anatomical and surgical neck (∼5% and ∼50% incidence respectively) are frequent in elderly population. Yet, neither in-vitro experiments nor CT-based finite element analyses (CTFEA) have investigated these in depth. Herein we enhance (Dahan et al., 2019) (addressing anatomical neck fractures) by more experiments and specimens, accounting for surgical neck fractures and explore CTFEA's prediction of humeri mechanical response and yield force.

METHODS

Four fresh frozen human humeri were tested in a new experimental configuration inducing surgical neck fractures. Digital image correlation (DIC) provided strains and displacements on humeri surfaces and used to validate CTFEA predictions. CTFEA were enhanced herein to improve the accuracy at the proximal neck: A cortical bone mapping (CBM) algorithm was implemented to overcome insufficient scanning resolution, and a new trabecular material mapping was investigated.

RESULTS

The new experimental setting induced impacted surgical neck fractures in all humeri. Excellent DIC to CTFEA correlation in strains was obtained at the shaft (slope 0.984, R²=0.99) and a fair agreement (slope 0.807, R²=0.73) at the neck. CBM algorithm had worsened the correlation, whereas the new material mapping had a negligible influence. Yield loads predictions improved considerably when trabecular yielding (maximum principal strain criterion) was considered instead of surface cortical yielding.

DISCUSSION

CTFEA well predicts strains on the shaft and reasonably well on the neck. This enhances former conclusions by past studies conducted using SGs, now also evident by DIC. Yield load prediction for surgical neck fractures (involving crushing of trabecular bone) is predicted better by trabecular failure laws rather than cortex ones. Further FEA studies using trabecular orthotropic constitutive models and failure laws are warrant.

Effects of reduced mobility on trabecular bone density in captive big cats

Bone responds to elevated mechanical loading by increasing in mass and density. Therefore, wild animals should exhibit greater skeletal mass and density than captive conspecifics. This expectation is pertinent to testing bone functional adaptation theories and to comparative studies, which commonly use skeletal remains that combine zoo and wild-caught specimens. Conservationists are also interested in the effects of captivity on bone morphology as it may influence rewilding success. We compared trabecular bone volume fraction (BVF) between wild and captive mountain lions, cheetahs, leopards and jaguars. We found significantly greater BVF in wild than in captive felids. Effects of captivity were more marked in the humerus than in the femur. A ratio of humeral/femoral BVF was also lower in captive animals and showed a positive relationship to home range size in wild animals. Results are consistent with greater forelimb than hindlimb loading during terrestrial travel, and possibly reduced loading of the forelimb associated with lack of predatory behaviour in captive animals. Thus, captivity among felids has general effects on BVF in the postcranial skeleton and location-specific effects related to limb use. Caution should be exercised when identifying skeletal specimens for use in comparative studies and when rearing animals for conservation purposes.

Associations between parameters of peripheral quantitative computed tomography and bone material strength index

BACKGROUND

Bone material strength index (BMSi) is measured in vivo using impact microindentation (IMI). However, the associations between BMSi and other bone measures are not clear. This study investigated whether bone parameters derived by peripheral quantitative computed tomography (pQCT) are associated with BMSi.

METHODS

Participants were men (n = 373, ages 34-96 yr) from the Geelong Osteoporosis Study. BMSi was measured using an OsteoProbe (Active Life Scientific, USA). Bone measures were obtained at both the radius (n = 348) and tibia (n = 342) using pQCT (XCT 2000 Stratec Medizintechnik, Germany). Images were obtained at 4% and 66% of radial and tibial length. Associations between pQCT parameters and BMSi were tested using Spearman's correlation and multivariable regression used to determine independent associations after adjustment for potential confounders. Models were checked for interaction terms.

RESULTS

Weak associations were observed between total bone density (radius 4%; r = +0.108, p = 0.046, tibia 4%; r = +0.115, p = 0.035), cortical density (tibia 4%; r = +0.123, p = 0.023) and BMSi. The associations were independent of weight, height, and glucocorticoid use (total bone density: radius 4%; β = 0.020, p = 0.006, tibia 4%; β = 0.020, p = 0.027 and cortical density: radius 4%; β = 4.160, p = 0.006, tibia 4%; β = 0.038, p = 0.010). Associations with bone mass were also observed at the 66% radial and tibial site, independent of age, weight, and glucocorticoid use (β = 4.160, p = 0.053, β = 1.458, p = 0.027 respectively). Total area at the 66% tibial site was also associated with BMSi (β = 0.010, p = 0.012), independent of weight and glucocorticoid use. No interaction terms were identified.

CONCLUSION

There were weak associations detected between some pQCT-derived bone parameters and BMSi.

A systematic review and meta-analysis of pediatric normative peripheral quantitative computed tomography data

BACKGROUND

Peripheral-quantitative computed tomography (pQCT) provides an intriguing diagnostic alternative to dual-energy X-ray absorptiometry (DXA) since it can measure 3D bone geometry and differentiate between the cortical and trabecular bone compartments.

OBJECTIVE

To investigate and summarize the methods of pQCT image acquisition of in children, adolescents and/or young adults (up to age 20) and to aggregate the published normative pQCT data.

EVIDENCE ACQUISITION

A literature search was conducted in MEDLINE and EMBASE from 1947 to December 2020. Quality of the included articles was assessed using Standards for Reporting of Diagnostic Accuracy (STARD) scoring system and United States Preventative Services Task Force (USPSTF) Study Design Categorization. Seven articles, encompassing a total of 2134 participants, were aggregated in the meta-analysis. Due to dissimilar age groups and scan sites, only seven pQCT parameters of the 4% radius, 4% tibia and 38% tibia were analyzed in this meta-analysis.

EVIDENCE SYNTHESIS

The overall fixed-effect estimates of trabecular vBMD of the 4% radius were: 207.16 (201.46, 212.86), mg/cm3 in 8 to 9 year-old girls, 210.42 (201.91, 218.93)in 10 to 12 year-old girls, 226.99 (222.45, 231.54) in 12 to 13 year-old girls, 259.97 (254.85, 265.10) in 12 to 13 year-old boys and 171.55 (163.41,179.69) in 16 to 18 year-old girls. 21 of 54 (38.9%) primary papers received a 'good' STARD quality of reporting score (<90 and 70 ≥ %) (mean STARD score of all articles = 69.4%). The primary articles of this review had a 'good' level USPSTF study design categorization. However, most of the normative data in these articles were non-comparable and non-aggregable due to a lack of standardization of reference lines, acquisition parameters and/or age at acquisition.

CONCLUSION

There is not sufficient evidence to suggest that pQCT is appropriately suited for use in the pediatric clinical setting. Normative pediatric data must be systematically derived for pQCT should it ever be a modality that is used outside of research.

CLINICAL IMPACT

We demonstrate the need for normative pQCT reference data and for clinical guidelines that standardize pediatric acquisition parameters and delineate its use in pediatric settings.

Effect of rheumatoid arthritis and age on metacarpal bone shaft geometry and density: A longitudinal pQCT study in postmenopausal women

OBJECTIVE

This study aimed to elucidate the effects of changes in the geometry and density of the metacarpal bone of patients with rheumatoid arthritis (RA).

METHODS

This prospective study included consecutive postmenopausal RA patients who met the American College of Rheumatology Criteria and healthy controls (HC). Peripheral quantitative computed tomography scans at 50% of the total metacarpal shaft (third metacarpal bone) were obtained at baseline and follow-ups. Use of bisphosphonates (BP), glucocorticoids (GC), biologics, and disease-modifying anti-rheumatic drugs (DMARD) was monitored (baseline to follow-up). Total cross-sectional area (CSA), cortical-transitional zone and compact zone CSA, cortical volumetric bone mineral density, and compact cortex porosity were measured. A linear mixed-effects model was used to determine significant differences in the rate of change in the RA and control groups and in RA patient subgroups.

RESULTS

Thirty-nine RA patients and 42 consecutive postmenopausal HC were followed for 63 months. RA and HC depicted a time-dependent increase of medullary CSA (+0.41 mm²/year, P < 0.0001), while total CSA remained stable (P = 0.2). RA status was associated with a loss of cortical bone mineral density (interaction: -3.08 mg/mm³; P = 0.014). In RA subgroup analysis, GC use ≥5 mg/day was positively correlated with a fourfold increase of medullary CSA (0.67 mm²/year P = 0.009), which resulted in a three- to fourfold loss of cortical density (-6.6 mg/mm³/year; P = 0.002) and cortical CSA (-0.57 mm²/year, P = 0.004). Patients with high disease activity and high GC dose at baseline demonstrated an increase in the total CSA (0.29 mm²/y; P = 0.049) and a loss of cortical BMD (-5.73 mg/mm³/y; P = 0.05) despite good clinical response.

CONCLUSION

Increase in medullary metacarpal CSA and thinning of the cortical CSA are physiological and time dependent. RA status is associated with loss in cortical density. Even upon biological therapy, low glucocorticoid dose affects metacarpal bone shaft geometry and density over time.

A new noninvasive mechanical bending test accurately predicts ulna bending strength in cadaveric human arms

BACKGROUND

High error rates in the prediction of fragility fractures by bone mineral density have motivated searches for better clinical indicators of bone strength, and the high incidence of non-hip, non-spine fractures has raised interest in cortical bone. The aim of this study was to assess the accuracy of Cortical Bone Mechanics Technology™. CBMT is a new non-invasive 3-point bending technique for measuring the mechanical properties of cortical bone in the ulnas of living humans.

METHODS

35 cadaveric human arms were obtained from small women and large men ranging widely in age (17 < Age < 99 years) and body size (14 < BMI < 40 kg/m²). Noninvasive CBMT measurements of the flexural rigidity of the ulna bones within these arms (EI_CBMT) were compared to measurements of EI by Quasistatic Mechanical Testing in the ulnas excised from those arms (EI_QMT). Ulna bending strength was also measured by QMT as the peak moment before fracture (M_peak). The open source BoneJ plugin to ImageJ image processing software was used to calculate cortical porosity (CP) in micro-computed tomography images of a 2 mm length of the mid-shaft of each fractured ulna, and the interosseous diameter (IOD) of each ulna was also measured in those images.

RESULTS

EI_CBMT measurements (13 < EI_CBMT < 97 Nm²) explained 99% of the variance in QMT measurements of ulna bending strength (11 < M_peak < 90 Nm), but EI_CBMT was biased high by 30% (p < 0.0001) relative to EI_QMT (11 < EI_QMT < 69 Nm²). After correcting this bias, EI_CBMT and EI_QMT measurements lay along the identity line (y = 1.00x, R² = 0.99, SEE = 3.1 Nm²). Predictions of M_peak by EI_CBMT were less accurate than predictions by EI_QMT (both R² = 0.99; SEE_CBMT = 5.9 Nm vs SEE_QMT = 4.5 Nm, F = 2.92, p = 0.001), but EI_CBMT predictions were substantially more accurate than those by IOD (R² = 0.79; SEE_IOD = 10.6 Nm, F = 3.30, p < 0.001) and CP (R² = 0.35; SEE_CP = 18.9 Nm, F = 10.45, p < 10^-9). Predictions by EI_CBMT were also more accurate than predictions by arm donor height (R² = 0.63; SEE = 14.3 Nm, F = 5.87, p < 10^-6), body weight (R² = 0.77; SEE = 11.1 Nm, F = 3.54, p < 0.001) and BMI (R² = 0.64; SEE = 14.1 Nm, F = 2.39, p < 0.01). In forward stepwise multiple regression beginning with EI_CBMT, only age explained any additional variance in ulna bending strength (ΔR² = 0.3%, F = 8.03, p = 0.008).

CONCLUSION

Noninvasive CBMT measurements of ulna EI explain 99% of individual differences in QMT measurements of ulna bending strength in cadaveric human arms.

Automated skeletal tissue quantification in the lower leg using peripheral quantitative computed tomography

OBJECTIVE

In this paper we introduce a methodology for hard and soft tissue quantification at proximal, intermediate and distal tibia sites using peripheral quantitative computed tomography scans. Quantification of bone properties is crucial for estimating bone structure resistance to mechanical stress and adaptations to loading. Soft tissue variables can be computed to investigate muscle volume and density, muscle-bone relationship, and fat infiltration.

APPROACH

We employed implicit active contour models and clustering techniques for automated segmentation and identification of bone, muscle and fat at [Formula: see text], [Formula: see text], and [Formula: see text] tibia length. Next, we calculated densitometric, area and shape characteristics for each tissue type. We implemented our approach as a multi-platform tool denoted by TIDAQ (tissue identification and quantification) to be used by clinical researchers.

MAIN RESULTS

We validated the proposed method against reference quantification measurements and tissue delineations obtained by semi-automated workflows. The average Deming regression slope between the tested and reference method was 1.126 for cross-sectional areas and 1.078 for mineral densities, indicating very good agreement. Our method produced high average coefficient of variation (R ²) estimates: 0.935 for cross-sectional areas and 0.888 for mineral densities over all tibia sites. In addition, our tissue segmentation approach achieved an average Dice coefficient of 0.91 over soft and hard tissues, indicating very good delineation accuracy.

SIGNIFICANCE

Our methodology should allow for high throughput, accurate and reproducible automatic quantification of muscle and bone characteristics of the lower leg. This information is critical to evaluate risk of future adverse outcomes and assess the effect of medications, hormones, and behavioral interventions aimed at improving bone and muscle strength.

A partially supervised physical activity program for adult and adolescent survivors of childhood cancer (SURfit): study design of a randomized controlled trial [NCT02730767]

BACKGROUND

Beyond survival of nowadays >80%, modern childhood cancer treatment strives to preserve long-term health and quality of life. However, the majority of today's survivors suffer from short- and long-term adverse effects such as cardiovascular and pulmonary diseases, obesity, osteoporosis, fatigue, depression, and reduced physical fitness and quality of life. Regular exercise can play a major role to mitigate or prevent such late-effects. Despite this, there are no data on the effects of regular exercise in childhood cancer survivors from randomized controlled trials (RCTs). Primary outcome of the current RCT is therefore the effect of a 12-months exercise program on a composite cardiovascular disease risk score in childhood cancer survivors. Secondary outcomes are single cardiovascular disease risk factors, glycaemic control, bone health, body composition, physical fitness, physical activity, quality of life, mental health, fatigue and adverse events (safety).

METHODS

A total of 150 childhood cancer survivors aged ≥16 years and diagnosed ≥5 years prior to the study are recruited from Swiss paediatric oncology clinics. Following the baseline assessments patients are randomized 1:1 into an intervention and control group. Thereafter, they are seen at month 3, 6 and 12 for follow-up assessments. The intervention group is asked to add ≥2.5 h of intense physical activity/week, including 30 min of strength building and 2 h of aerobic exercises. In addition, they are told to reduce screen time by 25%. Regular consulting by physiotherapists, individual web-based activity diaries, and pedometer devices are used as motivational tools for the intervention group. The control group is asked to keep their physical activity levels constant.

DISCUSSION

The results of this study will show whether a partially supervised exercise intervention can improve cardiovascular disease risk factors, bone health, body composition, physical activity and fitness, fatigue, mental health and quality of life in childhood cancer survivors. If the program will be effective, all relevant information of the SURfit physical activity intervention will be made available to interested clinics that treat and follow-up childhood cancer patients to promote exercise in their patients.

TRIAL REGISTRATION

Prospectively registered in clinicaltrials.gov [ NCT02730767 ], registration date: 10.12.2015.

Low trabecular bone density in recent sedentary modern humans

OBJECTIVES

Research on a limited number of samples suggests that trabecular bone density (i.e., bone volume fraction, BVF) within specific articulations is lower among more sedentary Holocene agricultural populations compared with Holocene foragers, implying that activity levels have a significant effect on trabecular BVF. However, it is unclear to what extent BVF differs among groups with varying activity levels and how general this phenomenon is across multiple limb articulations. Here, we test two hypotheses that: (i) sedentary populations have lower BVF compared with active populations across limb articulations; and (ii) these declines are more uniform in the lower limb (because of its more direct relationship to mobility), and more variable in the upper limb.

MATERIALS AND METHODS

We estimated BVF in seven lower and upper limb articulations of five Holocene population samples with subsistence strategies spanning from foraging through horticultural to industrial using pQCT (peripheral Quantitative Computed Tomography).

RESULTS

Both hypotheses are largely supported. First, the most active groups have significantly greater BVF in most limb elements compared with more sedentary groups. Second, all sedentary groups have relatively similar (and lower) BVF in the lower limb but show more variation in upper limb articulations.

CONCLUSIONS

These results suggest that a decline in activity levels associated with the adoption of agriculture and industrialization significantly contributed to the reduction in BVF in recent modern humans, but specific behavioral changes, particularly in the upper limb, also affected these patterns.

Bone Traits Seem to Develop Also During the Third Decade in Life-Normative Cross-Sectional Data on 1083 Men Aged 18-28 Years

By identifying individuals with low peak bone mass (PBM) at young age, early targeted interventions to reduce future fracture risk could be possible. Peripheral quantitative computed tomography (pQCT) is in many ways superior to the gold standard dual-energy X-ray absorptiometry (DXA), as cortical and trabecular compartments as well as the volumetric density and bone structure can be examined separately. Because each of these traits contributes independently to bone strength, it is probable that pQCT provides an even better fracture risk estimation than DXA. Currently, the clinical applications of pQCT are limited partly because comprehensive normative pQCT data, especially in young men, are not readily available. We therefore set up a study in young men with the following objectives: (1) to identify peak ages in pQCT bone traits with special reference to PBM and peak bone strength; and (2) to provide normative pQCT data. We measured volumetric bone mineral density and structural parameters at ultradistal (trabecular bone) and diaphyseal radius and tibia (cortical bone) by pQCT scans (Stratec XCT2000®; Stratec Medizintechnik GmbH, Pforzheim, Germany) in a population-based age-stratified sample of 1083 men aged 18-28 yr residing in greater Malmö, Sweden. Group differences in 1-yr classes were evaluated by analysis of variance. We found similar bone traits in age groups at ultradistal sites whereas most bone traits at diaphyseal sites were higher with higher ages, however with different increment patterns depending on the specific trait. In Swedish young adult men, we found that different bone traits continued to change after age 18, but at different rates, indicating that peak areal bone mineral density (as measured by DXA) and peak bone strength may be reached at different ages.

Scattered image artifacts from cone beam computed tomography and its clinical potential in bone mineral density estimation

Background

Image artifacts affect the quality of medical images and may obscure anatomic structure and pathology. Numerous methods for suppression and correction of scattered image artifacts have been suggested in the past three decades. In this paper, we assessed the feasibility of use of information on scattered artifacts for estimation of bone mineral density (BMD) without dual-energy X-ray absorptiometry (DXA) or quantitative computed tomographic imaging (QCT).

Methods

To investigate the relationship between scattered image artifacts and BMD, we first used a forearm phantom and cone-beam computed tomography. In the phantom, we considered two regions of interest—bone-equivalent solid material containing 50 mg HA per cm⁻³ and water—to represent low- and high-density trabecular bone, respectively. We compared the scattered image artifacts in the high-density material with those in the low-density material. The technique was then applied to osteoporosis patients and healthy subjects to assess its feasibility for BMD estimation.

Results

The high-density material produced a greater number of scattered image artifacts than the low-density material. Moreover, the radius and ulna of healthy subjects produced a greater number of scattered image artifacts than those from osteoporosis patients.

Conclusions

Although other parameters, such as bone thickness and X-ray incidence, should be considered, our technique facilitated BMD estimation directly without DXA or QCT. We believe that BMD estimation based on assessment of scattered image artifacts may benefit the prevention, early treatment and management of osteoporosis.

Decreased bone cortical density at the forearm in subjects with subclinical peripheral arterial disease

The association between peripheral arterial disease (PAD) and low bone mass is controversial. In our study, peripheral quantitative computed tomography shows a reduction of cortical but not trabecular, bone mineral density (BMD) at the forearm, in patients with subclinical PAD.

INTRODUCTION

Some controversy exists regarding the association between peripheral arterial disease (PAD) and low bone mass. Previous studies have evaluated bone mineral density (BMD) in patients with subclinical PAD, with mixed results. Inconsistency of data may depend on the fact that most studies measured areal bone mineral density (aBMD) by Dual-energy-x ray absorptiometry (DXA). Because DXA cannot distinguish between cortical and trabecular compartments, we reasoned that a study aimed to establish whether these compartments were differentially affected by PAD status could give more information on the nature of this association.

METHODS

In this cross-sectional study, we used peripheral quantitative computed tomography (pQCT) to examine volumetric cortical and trabecular mineral density at the radius (vBMD) in a cohort of subjects with subclinical PAD as defined by ABI ≤0.90 and compared them with healthy subjects with no evidence of PAD.

RESULTS

Patients with subclinical PAD had significantly reduced cortical density (1101.0 ± 45.4 vs 1156.2 ± 51.3 mg/cm(3), p < 0.001) and cortical area (75.0 ± 20.9 vs 99.9 ± 18.2 mm(2), p < 0.001) than healthy subjects. Trabecular density (178.1 ± 47.9 vs 165.8 ± 29.6 mg/cm(3)) was not significantly different in the two groups.

CONCLUSION

Subclinical PAD induces a selective bone loss at the radius compartment, not identified by standard DXA, which seems to occur primarily at the cortical level.

Measurement of muscle and fat in postmenopausal women: precision of previously reported pQCT imaging methods

Peripheral quantitative computed tomography (pQCT) imaging has been used to quantify muscle area and density as well as intermuscular adipose tissue (IMAT) and subcutaneous adipose tissue (SAT) area in the lower and upper limb. Numerous protocols have been reported to derive these soft-tissue outcomes, but their precision has not been assessed in community-dwelling postmenopausal women. The objective of this study was to compare the precision of previously reported analysis protocols for quantifying muscle area and density, as well as IMAT and SAT area in postmenopausal women. Six image analysis protocols using two available software suites (Stratec XCT, BoneJ) were identified from the pQCT literature. Analysis protocols were applied to a sample of 35 older female adults (mean age 73.7; SD 7.2 years), randomly selected from a population based-cohort and scanned twice within an average of 9.7 (SD 3.6) days. Relative precision was calculated as absolute values and as a percentage of the sample mean (root mean square coefficient of variation; CV%RMS). Soft-tissue outcomes across protocols were compared on their log-transformed coefficients of variation using multilevel linear models and Tukey contrasts. For most protocols, CV%RMS for muscle area, density, and SAT area ranged between 2.1 and 3.7%, 0.7 and 1.9%, and 2.4 and 6.4%, respectively. Precision for IMAT area varied considerably, from 3 to 42%. Consideration of these study results will aid in the selection of appropriate image analysis protocols for pQCT-derived soft-tissue outcomes in postmenopausal women.

Decreases in bone mineral density at cortical and trabecular sites in the tibia and femur during the first year of spinal cord injury

BACKGROUND

Disuse osteoporosis occurs in response to long-term immobilization. Spinal cord injury (SCI) leads to a form of disuse osteoporosis that only affects the paralyzed limbs. High rates of bone resorption after injury are evident from decreases in bone mineral content (BMC), which in the past have been attributed in the main to loss of trabecular bone in the epiphyses and cortical thinning in the shaft through endocortical resorption.

METHODS

Patients with motor-complete SCI recruited from the Queen Elizabeth National Spinal Injuries Unit (Glasgow, UK) were scanned within 5weeks of injury (baseline) using peripheral Quantitative Computed Tomography (pQCT). Unilateral scans of the tibia, femur and radius provided separate estimates of trabecular and cortical bone parameters in the epiphyses and diaphyses, respectively. Using repeat pQCT scans at 4, 8 and 12months post-injury, changes in BMC, bone mineral density (BMD) and cross-sectional area (CSA) of the bone were quantified.

RESULTS

Twenty-six subjects (5 female, 21 male) with SCI (12 paraplegic, 14 tetraplegic), ranging from 16 to 76years old, were enrolled onto the study. Repeated-measures analyses showed a significant effect of time since injury on key bone parameters at the epiphyses of the tibia and femur (BMC, total BMD, trabecular BMD) and their diaphyses (BMC, cortical BMD, cortical CSA). There was no significant effect of gender or age on key outcome measures, but there was a tendency for the female subjects to experience greater decreases in cortical BMD. The decreases in cortical BMD in the tibia and femur were found to be statistically significant in both men and women.

CONCLUSIONS

By carrying out repeat pQCT scans at four-monthly intervals, this study provides a uniquely detailed description of the cortical bone changes that occur alongside trabecular bone changes in the first year of complete SCI. Significant decreases in BMD were recorded in both the cortical and trabecular bone compartments of the tibia and femur throughout the first year of injury. This study provides evidence for the need for targeted early intervention to preserve bone mass within this patient group.

Recent origin of low trabecular bone density in modern humans

Humans are unique, compared with our closest living relatives (chimpanzees) and early fossil hominins, in having an enlarged body size and lower limb joint surfaces in combination with a relatively gracile skeleton (i.e., lower bone mass for our body size). Some analyses have observed that in at least a few anatomical regions modern humans today appear to have relatively low trabecular density, but little is known about how that density varies throughout the human skeleton and across species or how and when the present trabecular patterns emerged over the course of human evolution. Here, we test the hypotheses that (i) recent modern humans have low trabecular density throughout the upper and lower limbs compared with other primate taxa and (ii) the reduction in trabecular density first occurred in early Homo erectus, consistent with the shift toward a modern human locomotor anatomy, or more recently in concert with diaphyseal gracilization in Holocene humans. We used peripheral quantitative CT and microtomography to measure trabecular bone of limb epiphyses (long bone articular ends) in modern humans and chimpanzees and in fossil hominins attributed to Australopithecus africanus, Paranthropus robustus/early Homo from Swartkrans, Homo neanderthalensis, and early Homo sapiens. Results show that only recent modern humans have low trabecular density throughout the limb joints. Extinct hominins, including pre-Holocene Homo sapiens, retain the high levels seen in nonhuman primates. Thus, the low trabecular density of the recent modern human skeleton evolved late in our evolutionary history, potentially resulting from increased sedentism and reliance on technological and cultural innovations.

Body composition during childhood and adolescence: relations to bone strength and microstructure

CONTEXT

Numerous studies have examined the association of body composition with bone development in children and adolescents, but none have used micro-finite element (μFE) analysis of high-resolution peripheral quantitative computed tomography images to assess bone strength.

OBJECTIVE

This study sought to examine the relations of appendicular lean mass (ALM) and total body fat mass (TBFM) to bone strength (failure load) at the distal radius and tibia.

DESIGN, PARTICIPANTS, AND SETTING

This was a cross-sectional study of 198 healthy 8- to <15-year-old boys (n = 109) and girls (n = 89) performed in a Clinical Research Unit.

RESULTS

After adjusting for bone age, height, fracture history, ALM, and TBFM, multiple linear regression analyses in boys and girls, separately, showed robust positive associations between ALM and failure loads at both the distal radius (boys: β = 0.92, P < .001; girls: β = 0.66, P = .001) and tibia (boys: β = 0.96, P < .001; girls: β = 0.66, P < .001). By contrast, in both boys and girls the relationship between TBFM and failure load at the distal radius was virtually nonexistent (boys: β = -0.07; P = .284; girls: β = -0.03; P = .729). At the distal tibia, positive, albeit weak, associations were observed between TBFM and failure load in both boys (β = 0.09, P = .075) and girls (β = 0.17, P = .033).

CONCLUSIONS

Our data highlight the importance of lean mass for optimizing bone strength during growth, and suggest that fat mass may have differential relations to bone strength at weight-bearing vs non-weight-bearing sites in children and adolescents. These observations suggest that the strength of the distal radius does not commensurately increase with excess gains in adiposity during growth, which may result in a mismatch between bone strength and the load experienced by the distal forearm during a fall. These findings may explain, in part, why obese children are over-represented among distal forearm fracture cases.

A comparative study of trabecular bone mass distribution in cursorial and non-cursorial limb joints

Skeletal design among cursorial animals is a compromise between a stable body that can withstand locomotor stress and a light design that is energetically inexpensive to grow, maintain, and move. Cursors have been hypothesized to reduce distal musculoskeletal mass to maintain a balance between safety and energetic cost due to an exponential increase in energetic demand observed during the oscillation of the distal limb. Additionally, experimental research shows that the cortical bone in distal limbs experiences higher strains and remodeling rates, apparently maintaining lower mass at the expense of a smaller safety factor. This study tests the hypothesis that the trabecular bone mass in the distal limb epiphyses of cursors is relatively lower than that in the proximal limb epiphyses to minimize the energetic cost of moving the limb. This study utilized peripheral quantitative computed tomography scanning to measure the trabecular mass in the lower and upper limb epiphyses of hominids, cercopithecines, and felids that are considered cursorial and non-cursorial. One-way ANOVA with Tukey post hoc corrections was used to test for significant differences in trabecular mass across limb epiphyses. The results indicate that overall, both cursors and non-cursors exhibit varied trabecular mass in limb epiphyses and, in certain instances, conform to a proximal-distal decrease in mass irrespective of cursoriality. Specifically, hominid and cercopithecine hind limb epiphyses exhibit a proximal-distal decrease in mass irrespective of cursorial adaptations. These results suggest that cursorial mammals employ other energy saving mechanisms to minimize energy costs during running.

Age-related changes in osteometry, bone mineral density and osteophytosis of the lumbar vertebrae in Japanese macaques

The age-related changes in lumbar vertebrae were studied in 77 young/full adult Japanese macaques (Macaca fuscata) (40 females, 37 males), in terms of their morphometry, density and osteophytosis, and the interrelationship between these three aspects. The most common age-related pattern of morphometric changes was an initial increase during young adulthood until reaching the peak and then a subsequent decrease with age. Most of the peaks were in the age group 15-20 and 10-15 years in females and males, respectively. In both sexes, the age-related decrease in the vertebral body depth (ventro-dorsal) was greater than in the height and width. The ventral height of the vertebral body relative to the dorsal height continuously decreased with age. The trabecular bone mineral density (BMD) continuously decreased after young adulthood. However, the magnitude of the decreased trabecular BMD with age was greater in females than in males, especially in the older age groups. Osteophytosis clearly increased with age in both sexes, but males showed an earlier appearance of osteophytes and females tended to have more severe osteophytes from 15 years old upwards. A correlation between the osteometry, density, and osteophytosis severity appeared in all vertebrae, but not all of these reached statistical significance after controlling for the influence of age. Although Japanese macaques showed the higher prevalence and rapid increase of osteophytosis, a similar age change profile was observed in the lumbar vertebrae of Japanese macaques and humans.

Bone strength and structural deficits in children and adolescents with a distal forearm fracture resulting from mild trauma

Although distal forearm fractures (DFFs) are common during childhood and adolescence, it is unclear whether they reflect underlying skeletal deficits or are simply a consequence of the usual physical activities, and associated trauma, during growth. Therefore, we examined whether a recent DFF, resulting from mild or moderate trauma, is related to deficits in bone strength and cortical and trabecular bone macro- and microstructure compared with nonfracture controls. High-resolution peripheral quantitative computed tomography was used to assess micro-finite element-derived bone strength (ie, failure load) and to measure cortical and trabecular bone parameters at the distal radius and tibia in 115 boys and girls with a recent (<1 year) DFF and 108 nonfracture controls aged 8 to 15 years. Trauma levels (mild versus moderate) were assigned based on a validated classification scheme. Compared with sex-matched controls, boys and girls with a mild-trauma DFF (eg, fall from standing height) showed significant deficits at the distal radius in failure load (-13% and -11%, respectively; p < 0.05) and had higher ("worse") fall load-to-strength ratios (both +10%; p < 0.05 for boys and p = 0.06 for girls). In addition, boys and girls with a mild-trauma DFF had significant reductions in cortical area (-26% and -23%, respectively; p < 0.01) and cortical thickness (-14% and -13%, respectively; p < 0.01) compared with controls. The skeletal deficits in the mild-trauma DFF patients were generalized, as similar changes were present at the distal tibia. By contrast, both boys and girls with a moderate-trauma DFF (eg, fall from a bicycle) had virtually identical values for all of the measured bone parameters compared with controls. In conclusion, DFFs during growth have two distinct etiologies: those owing to underlying skeletal deficits leading to fractures with mild trauma versus those owing to more significant trauma in the setting of normal bone strength.

Standardizing evaluation of pQCT image quality in the presence of subject movement: qualitative versus quantitative assessment

Peripheral quantitative computed tomography (pQCT) is an essential tool for assessing bone parameters of the limbs, but subject movement and its impact on image quality remains a challenge to manage. The current approach to determine image viability is by visual inspection, but pQCT lacks a quantitative evaluation. Therefore, the aims of this study were to (1) examine the reliability of a qualitative visual inspection scale and (2) establish a quantitative motion assessment methodology. Scans were performed on 506 healthy girls (9-13 years) at diaphyseal regions of the femur and tibia. Scans were rated for movement independently by three technicians using a linear, nominal scale. Quantitatively, a ratio of movement to limb size (%Move) provided a measure of movement artifact. A repeat-scan subsample (n = 46) was examined to determine %Move's impact on bone parameters. Agreement between measurers was strong (intraclass correlation coefficient = 0.732 for tibia, 0.812 for femur), but greater variability was observed in scans rated 3 or 4, the delineation between repeat and no repeat. The quantitative approach found ≥95% of subjects had %Move <25 %. Comparison of initial and repeat scans by groups above and below 25% initial movement showed significant differences in the >25 % grouping. A pQCT visual inspection scale can be a reliable metric of image quality, but technicians may periodically mischaracterize subject motion. The presented quantitative methodology yields more consistent movement assessment and could unify procedure across laboratories. Data suggest a delineation of 25% movement for determining whether a diaphyseal scan is viable or requires repeat.

Long-term outcome of morphology and function after soft tissue injury of the forearm with vascular involvement

BACKGROUND

We sought to assess long-term changes in bone, muscle area, and muscle strength at different levels of the forearm and hand mobility according to arterial patency and nerve damage after surgically treated trauma related to involuntary local cutting/piercing injuries.

METHODS

Forty subjects were evaluated 11 years after surgery for traumatic lesions involving the major vascular axis of the distal forearm. Peripheral quantitative computed tomography was used to measure cortical bone mineral density (BMD) and muscle area at the proximal radius, trabecular BMD at the distal radius, and cortical BMD at the third finger. Hand grip strength was assessed using dynamometry. Muscle area and hand grip strength were corrected for the limb dominance effect.

RESULTS

All subjects had reduced trabecular BMD at the distal radius on the affected side (Δ, -5.8%; P < 0.001) and reduced cortical BMD in the third finger (Δ, -2.8%; P < 0.05). Hand grip strength was significantly lower on the affected side. According to vascular patency, only subjects with nonpreserved blood flow had significantly reduced distal radius BMD (Δ, -6.7%; P = 0.004), and those with nerve damage had a significant reduction in BMD at the third finger (Δ, -3.5%; P = 0.05). Moreover, nerve injury was associated with the presence of clinical symptoms and hand functional impairment.

CONCLUSIONS

The absence of blood flow and nerve damage after forearm trauma caused by involuntary cutting/piercing injuries causes remarkable permanent impairment in musculoskeletal structures, hand grip strength, and hand functionality.

Changes in body composition in triathletes during an Ironman race

PURPOSE

Triathletes lose body mass during an Ironman triathlon. However, the associated body composition changes remain enigmatic. Thus, the purpose of this study was to investigate Ironman-induced changes in segmental body composition, using for the first time dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT).

METHODS

Before and after an Ironman triathlon, segmental body composition and lower leg tissue mass, areas and densities were assessed using DXA and pQCT, respectively, in eight non-professional male triathletes. In addition, blood and urine samples were collected for the determination of hydration status.

RESULTS

Body mass decreased by 1.9 ± 0.8 kg. This loss was due to 0.4 ± 0.3 and 1.4 ± 0.8 kg decrease in fat and lean mass, respectively (P < 0.01). Calf muscle density was reduced by 1.93 ± 1.04 % (P < 0.01). Hemoglobin, hematocrit, and plasma [K(+)] remained unchanged, while plasma [Na(+)] (P < 0.05), urine specific gravity and plasma and urine osmolality increased (P < 0.01).

CONCLUSIONS

The loss in lean mass was explained by a decrease in muscle density, as an indicator of glycogen loss, and increases in several indicators for dehydration. The measurement of body composition with DXA and pQCT before and after an Ironman triathlon provided exact values for the loss in fat and lean mass. Consequently, these results yielded more detailed insights into tissue catabolism during ultra-endurance exercise.

Association between serum 25-hydroxyvitamin d levels, bone geometry, and bone mineral density in healthy older adults

PURPOSE

The association between serum 25-hydroxyvitamin D values and cortical/trabecular bone parameters in older adults has been incompletely explored. This study was designed to investigate the relationship between serum 25-hydroxyvitamin D levels and bone parameters for the tibia and radius using peripheral quantitative computed tomography in free-living healthy older adults.

METHODS

The study involved 134 older adults attending a twice-weekly low-intensity fitness program. In addition to clinical history and serum parameters, we assessed fat-free mass using dual-energy X-ray absorptiometry, total bone and cortical bone cross-sectional areas, and trabecular and cortical bone mineral density for the tibia and radius by peripheral quantitative computed tomography.

RESULTS

After applying multivariate linear regression models, adjusting for sex, age, body mass index, fat mass and fat-free mass, and creatinine, the association between 25-hydroxyvitamin D and bone parameters was significant for total bone and cortical bone cross-sectional areas in the radius (partial R (2) = 0.05 and 0.09, respectively) and for trabecular bone mineral density and cortical bone cross-sectional area in the tibia (partial R (2) = 0.11 and 0.02, respectively).

CONCLUSION

These findings support the idea that serum 25-hydroxyvitamin D levels and bone parameters are linked in older adults. Longitudinal studies are needed to establish whether vitamin D levels over time are associated with changes in these parameters.

Predicting patient-specific rates of bone loss at fracture-prone sites after spinal cord injury

PURPOSE

People with spinal cord injury (SCI) experience bone loss and have an elevated rate of fracture in the paralysed limbs. The literature suggests an exponential time course of bone loss after SCI, but true rates may vary between patients. We propose systematic evaluation of bone status in the early stages of SCI to identify fast bone losers.

METHOD

A case series of six patients with complete SCI were scanned using peripheral quantitative computed tomography within 5 weeks and at 4, 8 and 12 months post-injury. Bone mineral density (BMD) and bone mineral content (BMC) were measured at fracture-prone sites in the tibia and femur. Patient-specific-predictions (PSP) of expected rates of bone loss were produced by individualising published model equations according to each patient's measured values at baseline. Wilcoxon Signed-Rank tests were used to identify changes between time-points; chi-squared tests for differences between measured and PSP values.

RESULTS

In the lower limbs, mean values decreased significantly between baseline and 8 months post-injury, by 19-31% for trabecular BMD, 21-32% for total BMD, and 9-29% for BMC. Most subjects showed no significant differences between PSP and measured values, but individuals with significantly faster rates of bone loss than predicted should be investigated further.

CONCLUSIONS

There was considerable intersubject variability in rates of bone loss after SCI. Patients showing the fastest bone loss could benefit from continued follow-up and possibly treatment.

Combination therapy with eldecalcitol and alendronate has therapeutic advantages over monotherapy by improving bone strength

Eldecalcitol (ED-71), a 2β-hydroxypropyloxy derivative of 1α,25(OH)(2)D(3), inhibits bone resorption more potently than does alfacalcidol while maintaining osteoblastic function in an estrogen-deficient, high-turnover osteoporosis rat model. Alendronate (ALN) has been reported to increase bone mass by suppressing bone resorption mainly by inducing apoptosis of osteoclasts. The aim of this study was to clarify the combination effect of ED-71 and ALN on bone loss in ovariectomized rats. Wistar-Imamichi rats (32weeks old) were ovariectomized and randomly assigned to 10 groups (n=9-11); 11 rats were sham-operated. Rats were orally administered either vehicle alone, ALN (0.05, 0.2mg/kg), ED-71 (0.015, 0.03μg/kg), or a combination of ALN and ED-71. The treatment started 2weeks after surgery and continued for 12weeks. ED-71 significantly increased calcium and phosphorus in serum and urine; however, the mean values were within the normal range. Bone mineral density (BMD) and maximum load in both the lumbar spine and femur significantly increased with ED-71 monotherapy, and showed a tendency to increase with ALN monotherapy. Compared with ALN monotherapy, the combination of ALN and ED-71 significantly increased BMD and maximum load in both the lumbar spine and femur, suggesting that the combination therapy is more beneficial than ALN monotherapy in this protocol. The combination treatment had an additive suppressive effect on eroded surface and osteoclast number, with the suppressive effect more potent than either ALN or ED-71 monotherapy. Moreover, the combination therapy partially counteracted the suppressive effects of ALN on bone formation and on the histomorphometric indices of osteoblast number and activity. Interestingly, ALN had no effect on the anabolic action of ED-71. In conclusion, the combination therapy of ALN and ED-71 has therapeutic advantages over ALN monotherapy in terms of improving bone mechanical strength without excessive suppression of bone turnover.

Skeletal muscle fat content is inversely associated with bone strength in young girls

Childhood obesity is an established risk factor for metabolic disease. The influence of obesity on bone development, however, remains controversial and may depend on the pattern of regional fat deposition. Therefore, we examined the associations of regional fat compartments of the calf and thigh with weight-bearing bone parameters in girls. Data from 444 girls aged 9 to 12 years from the Jump-In: Building Better Bones study were analyzed. Peripheral quantitative computed tomography (pQCT) was used to assess bone parameters at metaphyseal and diaphyseal sites of the femur and tibia along with subcutaneous adipose tissue (SAT, mm(2) ) and muscle density (mg/cm(3) ), an index of skeletal muscle fat content. As expected, SAT was positively correlated with total-body fat mass (r = 0.87-0.89, p < .001), and muscle density was inversely correlated with total-body fat mass (r = -0.24 to -0.28, p < .001). Multiple linear regression analyses with SAT, muscle density, muscle cross-sectional area, bone length, maturity, and ethnicity as independent variables showed significant associations between muscle density and indices of bone strength at metaphyseal (β = 0.13-0.19, p < .001) and diaphyseal (β = 0.06-0.09, p < .01) regions of the femur and tibia. Associations between SAT and indices of bone strength were nonsignificant at all skeletal sites (β = 0.03-0.05, p > .05), except the distal tibia (β = 0.09, p = .03). In conclusion, skeletal muscle fat content of the calf and thigh is inversely associated with weight-bearing bone strength in young girls.

Characterization of low bone mass in young patients with thalassemia by DXA, pQCT and markers of bone turnover

Previous reports using dual x-ray absorptiometry (DXA) suggest that up to 70% of adults with thalassemia major (Thal) have low bone mass. However, few studies have controlled for body size and pubertal delay, variables known to affect bone mass in this population. In this study, bone mineral content and areal density (BMC, aBMD) of the spine and whole body were assessed by DXA, and volumetric BMD and cortical geometries of the distal tibia by peripheral quantitative computed tomography (pQCT) in subjects with Thal (n = 25, 11 male, 10 to 30 years) and local controls (n=34, 15 male, 7 to 30 years). Z-scores for bone outcomes were calculated from reference data from a large sample of healthy children and young adults. Fasting blood and urine were collected, pubertal status determined by self-assessment and dietary intake and physical activity assessed by written questionnaires. Subjects with Thal were similar in age, but had lower height, weight and lean mass index Z-scores (all p < 0.001) compared to controls. DXA aBMD was significantly lower in Thal compared to controls at all sites. Adult Thal subjects (> 18 years, n = 11) had lower tibial trabecular vBMD (p = 0.03), cortical area, cortical BMC, cortical thickness, periosteal circumference and section modulus Z-scores (all p < 0.01) compared to controls. Cortical area, cortical BMC, cortical thickness, and periosteal circumference Z-scores (p = 0.02) were significantly lower in young Thal (≤ 18 years, n = 14) compared to controls. In separate multivariate models, tibial cortical area, BMC, and thickness and spine aBMD and whole body BMC Z-scores remained lower in Thal compared to controls after adjustment for gender, lean mass and/or growth deficits (all p < 0.01). Tanner stage was not predictive in these models. Osteocalcin, a marker of bone formation, was significantly reduced in Thal compared to controls after adjusting for age, puberty and whole body BMC (p=0.029). In summary, we have found evidence of skeletal deficits that cannot be dismissed as an artifact of small bone size or delayed maturity alone. Given that reduced bone density and strength are associated with increased risk of fracture, therapies focused on increasing bone formation and bone size in younger patients are worthy of further evaluation.

Lower trabecular volumetric BMD at metaphyseal regions of weight-bearing bones is associated with prior fracture in young girls

Understanding the etiology of skeletal fragility during growth is critical for the development of treatments and prevention strategies aimed at reducing the burden of childhood fractures. Thus we evaluated the relationship between prior fracture and bone parameters in young girls. Data from 465 girls aged 8 to 13 years from the Jump-In: Building Better Bones study were analyzed. Bone parameters were assessed at metaphyseal and diaphyseal sites of the nondominant femur and tibia using peripheral quantitative computed tomography (pQCT). Dual-energy X-ray absorptiometry (DXA) was used to assess femur, tibia, lumbar spine, and total body less head bone mineral content. Binary logistic regression was used to evaluate the relationship between prior fracture and bone parameters, controlling for maturity, body mass, leg length, ethnicity, and physical activity. Associations between prior fracture and all DXA and pQCT bone parameters at diaphyseal sites were nonsignificant. In contrast, lower trabecular volumetric BMD (vBMD) at distal metaphyseal sites of the femur and tibia was significantly associated with prior fracture. After adjustment for covariates, every SD decrease in trabecular vBMD at metaphyseal sites of the distal femur and tibia was associated with 1.4 (1.1-1.9) and 1.3 (1.0-1.7) times higher fracture prevalence, respectively. Prior fracture was not associated with metaphyseal bone size (ie, periosteal circumference). In conclusion, fractures in girls are associated with lower trabecular vBMD, but not bone size, at metaphyseal sites of the femur and tibia. Lower trabecular vBMD at metaphyseal sites of long bones may be an early marker of skeletal fragility in girls.

Correlations between strength and quantitative computed tomography measurement of callus mineralization in experimental tibial fractures

BACKGROUND

the evaluation of fracture healing in the clinic has not changed significantly during the past few decades, despite the development of modern tissue-imaging tools. Recent publications have reported significant and interesting associations between biomechanical properties and quantitative computed tomography data of fractures and grafts. We therefore studied the correlations between the strength and segmented quantitative computed tomography data of tibial diaphyseal fractures.

METHODS

forty male rats received a tibial-shaft osteotomy that was initially stabilized with either intramedullary nailing or external fixation. Evaluation at 30 and 60 days post-osteotomy included X-ray, quantitative computed tomography and bending testing. Quantitative computed tomography data were segmented by voxel density into soft callus (171-539 mg/cm(3)), hard callus (540-1199 mg/cm(3)) and cortical bone (≥ 1200mg/cm(3)), and volumetric bone mineral density was calculated.

FINDINGS

all fractures demonstrated pronounced formation of soft and hard callus tissues at 30 days post-osteotomy, and at 60 days the cortical bone volume was significantly increased with callus resorption. Bending strength correlated significantly and positively with fracture-site cortical bone volume and volumetric bone mineral density in the intramedullary nailed group in the early phase of healing.

INTERPRETATION

quantitative computed tomography was used to quantify characteristic secondary healing. The observed correlations indicate that biomechanically important mineralization can be measured by quantitative computed tomography in the early phase of healing in flexibly fixed fractures.

An automatic segmentation method for regional analysis of femoral neck images acquired by pQCT

We developed an automatic method for regional analysis of femoral neck images acquired by peripheral quantitative computed tomography (pQCT), based on automatic spatial re-alignment and segmentation; the segmentation method, based on a morphological approach, explicitly accounts for the presence of three different bone compartments: cortical region, trabecular region, and transition zone between cortical and trabecular compartments. The proposed method was applied on 13 femoral neck sections derived from female donors who were undergoing hip replacement surgery for primary degenerative arthritis or fracture, and a typical densitometric and structural analysis was performed both globally and regionally. The proposed segmentation method was quantitatively evaluated by comparing automatic contour and the corresponding manual contours delineated by three operators using metrics based on surface distance (average symmetric distance, ASD) and volumetric overlapping (dice similarity coefficient, DSC). The same approach was used to validate the automatic spatial orientation, considering as metric the difference between manual and automatic angle orientation. Results confirm a satisfactory agreement between automatic and manual performances (ASD < 0.41 mm, DSC > 0.91, orientation difference = 3.61°) and show that globally our algorithm performs very well. Concerning regional analysis application, from our results we can observe that significant differences are present among the four bone quadrants.

Bone mass and microarchitecture in CKD patients with fracture

Patients with predialysis chronic kidney disease (CKD) have increased risk for fracture, but the structural mechanisms underlying this increased skeletal fragility are unknown. We measured areal bone mineral density (aBMD) by dual-energy x-ray absorptiometry at the spine, hip, and radius, and we measured volumetric BMD (vBMD), geometry, and microarchitecture by high-resolution peripheral quantitative computed tomography (HR-pQCT) at the radius and tibia in patients with CKD: 32 with fracture and 59 without fracture. Patients with fracture had lower aBMD at the spine, total hip, femoral neck, and the ultradistal radius, the last having the strongest association with fracture. By HR-pQCT of the radius, patients with fracture had lower cortical area and thickness, total and trabecular vBMD, and trabecular number and greater trabecular separation and network heterogeneity. At the tibia, patients with fracture had significantly lower cortical area, thickness, and total and cortical density. Total vBMD at both radius and tibia most strongly associated with fracture. By receiver operator characteristic curve analysis, patients with longer duration of CKD had area under the curve of >0.75 for aBMD at both hip sites and the ultradistal radius, vBMD and geometry at the radius and tibia, and microarchitecture at the tibia. In summary, patients with predialysis CKD and fractures have lower aBMD by dual-energy x-ray absorptiometry and lower vBMD, thinner cortices, and trabecular loss by HR-pQCT. These density and structural differences may underlie the increased susceptibility to fracture among patients with CKD.

Reproducibility of peripheral quantitative computed tomography measurements at the radius and tibia in healthy pre- and postmenopausal women

PURPOSE

The objectives of this study were to utilise the XCT-2000 pQCT scanner to determine the mean values and the reproducibility of in vivo total, trabecular, and cortical volumetric bone measurements at distal and diaphyseal sites of the radius and the tibia, as well as calf muscle and subcutaneous fat areas, in healthy pre- and postmenopausal women.

METHODS

Twenty-nine women (14 premenopausal and 15 postmenopausal) were recruited to participate in this study. Distal and diaphyseal sites of the radius (at 4% and 20% of the length of the radius) and tibia (at 4%, 38%, and 66% of the length of the tibia) were examined.

RESULTS

The root mean square coefficient of variation for measurements at the distal tibia gave the most favorable reproducibility values for total (1.5%) and trabecular (1.6%) density, whereas the diaphyseal tibia showed the most favorable reproducibility value for cortical density (0.3%). The root mean square coefficients of variation for measurements of muscle and fat cross-sectional areas at the calf were 0.6% and 0.7%, respectively. At the distal tibia, the mean values for total (P < .05) and trabecular (P < .01) density were significantly lower in postmenopausal women than in premenopausal women.

CONCLUSIONS

The data presented here indicate that XCT-2000 pQCT scans at the tibia provide highly reproducible measurements of total, cortical, and trabecular bone as well as muscle and fat cross-sectional areas. Furthermore, significant differences in volumetric bone measurements between healthy pre- and postmenopausal women were evident only at the distal tibia, suggesting that this site warrants further study.

Reduced trabecular bone mineral density and cortical thickness accompanied by increased outer bone circumference in metacarpal bone of rheumatoid arthritis patients: a cross-sectional study

Introduction

The objective of this study was to assess three-dimensional bone geometry and density at the epiphysis and shaft of the third meta-carpal bone of rheumatoid arthritis (RA) patients in comparison to healthy controls with the novel method of peripheral quantitative computed tomography (pQCT).

Methods

PQCT scans were performed in 50 female RA patients and 100 healthy female controls at the distal epiphyses and shafts of the third metacarpal bone, the radius and the tibia. Reproducibility was determined by coefficient of varia-tion. Bone densitometric and geometric parameters were compared between the two groups and correlated to disease characteristics.

Results

Reproducibility of different pQCT parameters was between 0.7% and 2.5%. RA patients had 12% to 19% lower trabecular bone mineral density (BMD) (P ≤ 0.001) at the distal epiphyses of radius, tibia and metacarpal bone. At the shafts of these bones RA patients had 7% to 16% thinner cortices (P ≤ 0.03). Total cross-sectional area (CSA) at the metacarpal bone shaft of pa-tients was larger (between 5% and 7%, P < 0.02), and relative cortical area was reduced by 13%. Erosiveness by Ratingen score correlated negatively with tra-becular and total BMD at the epiphyses and shaft cortical thickness of all measured bones (P < 0.04).

Conclusions

Reduced trabecular BMD and thinner cortices at peripheral bones, and a greater bone shaft diameter at the metacarpal bone suggest RA spe-cific bone alterations. The proposed pQCT protocol is reliable and allows measuring juxta-articular trabecular BMD and shaft geometry at the metacarpal bone.

Childhood growth hormone deficiency, bone density, structures and fractures: scrutinizing the evidence

Childhood-onset growth hormone deficiency (GHD) is frequently perceived to cause low bone density, fractures and osteoporosis. This article critically reviews the evidence behind these perceptions. Inherent limitations of current bone imaging techniques have caused many artefacts and misconceptions about bone density and structure. Using appropriate size-corrections, bone density is normal in children and adults with isolated GHD. Cortical density, trabecular density and trabecular volume are normal when measured by peripheral quantitative computerized tomography and histomorphometry. The only verifiable deficit affects cortical thickness (periosteal expansion), both in human and animal studies. However, short limb bones cannot be expected to have an average-sized shaft, as bone elongation and widening could be proportionally impaired in GHD. In addition, GH and IGF-1 have indisputable anabolic actions not only on bone, but also on muscle tissue. In fact, compared with all other bone-related variables, muscle size is the lowest at diagnosis of GHD. During GH therapy, muscle enlargement precedes and exceeds any gain in bone mass. The mechanostat theory suggests that the GHD-induced deficit in muscle force secondarily causes low cortical thickness. There is no evidence that isolated childhood-onset GHD, or severe GH resistance, causes an increased fracture risk in children or adults. Only adults with organic hypopituitarism appear to have a slightly greater risk of fractures. Using current transition guidelines, short children and adults with GHD are at risk of being misdiagnosed with low bone mass and may consequently receive inappropriate treatment. As neither reports of increased fracture risk nor low bone density can stand up against scrutiny, these misconceptions should no longer influence clinical practice. In this respect, GHD should not be listed as a cause of osteoporosis in children and there is a need to review current transition guidelines.

History of amenorrhoea compromises some of the exercise-induced benefits in cortical and trabecular bone in the peripheral and axial skeleton: a study in retired elite gymnasts

BACKGROUND

Female gymnasts frequently present with overt signs of hypoestrogenism, such as late menarche or menstrual dysfunction. The objective was to investigate the impact of history of amenorrhoea on the exercise-induced skeletal benefits in bone geometry and volumetric density in retired elite gymnasts.

SUBJECTS AND METHODS

24 retired artistic gymnasts, aged 17-36 years, who had been training for at least 15 h/week at the peak of their career and had been retired for 3-18 years were recruited. They had not been engaged in more than 2 h/week of regular physical activity since retirement. Former gymnasts who reported history of amenorrhoea ('AME', n=12: either primary or secondary amenorrhoea) were compared with former gymnasts ('NO-AME', n=12) and controls ('C', n=26) who did not report history of amenorrhoea. Bone mineral content (BMC), total bone area (ToA) and total volumetric density (ToD) were measured by pQCT at the radius and tibia (4% and 66%). Trabecular volumetric density (TrD) and bone strength index (BSI) were measured at the 4% sites. Cortical area (CoA), cortical thickness (CoTh), medullary area (MedA), cortical volumetric density (CoD), stress-strain index (SSI) and muscle and fat area were measured at the 66% sites. Spinal BMC, areal BMD and bone mineral apparent density (BMAD) were measured by DXA.

RESULTS

Menarcheal age was delayed in AME when compared to NO-AME (16.4+/-0.5 years vs. 13.3+/-0.4 years, p<0.001). No differences were detected between AME and C for height-adjusted spinal BMC, aBMD and BMAD, TrD and BSI at the distal radius and tibia, CoA at the proximal radius, whereas these parameters were greater in NO-AME than C (p<0.05-0.005). AME had lower TrD and BSI at the distal radius, and lower spinal BMAD than NO-AME (p<0.05) but they had greater ToA at the distal radius (p<0.05).

CONCLUSION

Greater spinal BMC, aBMD and BMAD as well as trabecular volumetric density and bone strength in the peripheral skeleton were found in former gymnasts without a history of menstrual dysfunction but not in those who reported either primary or secondary amenorrhoea. History of amenorrhoea may have compromised some of the skeletal benefits associated with high-impact gymnastics training.

Quantitative computed tomography (QCT) of the forearm using general purpose spiral whole-body CT scanners: accuracy, precision and comparison with dual-energy X-ray absorptiometry (DXA)

BACKGROUND

Dual-energy X-ray absorptiometry (DXA) allows clinically relevant measurement of bone mineral density (BMD) at central and appendicular skeletal sites, but DXA has a limited ability to assess bone geometry and cannot distinguish between the cortical and trabecular bone compartments. Quantitative computed tomography (QCT) can supplement DXA by enabling geometric and compartmental bone assessments. Whole-body spiral CT scanners are widely available and require only seconds per scan, in contrast to peripheral QCT scanners, which have restricted availability, limited spatial resolution, and require several minutes of scanning time. This study evaluated the accuracy and precision of whole-body spiral CT scanners for quantitatively assessing the distal radius, a common site of non-vertebral osteoporosis-related fractures, and compared the CT-measured densitometric values with those obtained from dual-energy-X-ray absorptiometry.

SUBJECTS AND METHODS

A total of 161 postmenopausal women with baseline lumbar spine BMD T-scores between -1.0 and -2.5 underwent left forearm QCT using whole-body spiral CT scanners twice, 1 month apart. QCT volumes of interest were defined and analyzed at 3 specific radial regions: the ultradistal region by using slices at 8, 9, and 10 mm proximal to the ulnar styloid tip; the distal region by a slice 20 mm proximal; and the middle region by a slice 40 mm proximal. BMD, bone mineral content (BMC), volume, and average cortical thickness and circumference were measured. We evaluated QCT accuracy and precision and also report correlations between QCT and DXA for BMD and BMC.

RESULTS

Overall accuracy and precision errors for BMD, BMC and volume were consistent with known skeletal QCT technology precision and were generally less than 3%. BMD and BMC assessed by QCT and DXA were correlated (r=0.55 to 0.80).

DISCUSSION

Whole-body spiral CT scanners allow densitometric evaluations of the distal radius with good accuracy and very good precision. This original and convenient method provides a tool to further investigate cortical and trabecular bone variables in the peripheral skeleton in osteoporotic patients. These assessments, coupled with evaluation of the effects on cortical and trabecular bone measured in response to therapies for osteoporosis, may advance our understanding of the contributors to non-vertebral fracture occurrence.

The combination therapy with alfacalcidol and risedronate improves the mechanical property in lumbar spine by affecting the material properties in an ovariectomized rat model of osteoporosis

Background

We conducted the present study to investigate the therapeutic effects of a combination treatment of alfacalcidol (ALF) and risedronate (RIS) on the bone mechanical properties of bone and calcium (Ca) metabolism using an ovariectomized (OVX) rat model of osteoporosis.

Methods

Female Wistar rats were OVX- or sham-operated at 40 weeks of age. Twelve weeks post-surgery, rats were randomized into seven groups: 1) sham + vehicle, 2) OVX + vehicle, 3) OVX + ALF 0.025 μg/kg/day, 4) OVX + ALF 0.05 μg, 5) OVX + RIS 0.3 mg, 6) OVX + RIS 3.0 mg, 7) OVX + ALF 0.025 μg + RIS 0.3 mg. Each drug was administered orally five times a week for 12 weeks. After treatment, we evaluated the mechanical properties of the lumbar vertebra and femoral midshaft. In the lumbar vertebra, structural and material analyses were performed using micro-computed tomography (micro-CT) and microbeam X-ray diffraction (micro-XRD), respectively. Biochemical markers in serum and urine were also determined.

Results

(1) With respect to improvement in the mechanical strength of the lumbar spine and the femoral midshaft, the combination treatment of ALF and RIS at their sub-therapeutic doses was more effective than each administered as a monotherapy; (2) In the suppression of bone resorption and the amelioration of microstructural parameters, the effects of ALF and RIS were considered to be independent and additive; (3) The improvement of material properties, such as microstructural parameters and the biological apatite (Bap) c-axis orientation, contributed to the reinforcement of spinal strength; and (4) The combination treatment of ALF and RIS normalized urinary Ca excretion, suggesting that this treatment ameliorated the changes in Ca metabolism.

Conclusion

These results demonstrate that the combination treatment of ALF and RIS at their sub-therapeutic doses can improve the mechanical properties of the spine as well as the femur and ameliorate changes in Ca metabolism in an animal model of osteoporosis, suggesting that the combination treatment of ALF and RIS has a therapeutic advantage over each monotherapy for the treatment of osteoporosis.