Comparison of short-term in vivo precision of bone density and microarchitecture at the distal radius and tibia between postmenopausal women and young adults

Precision of 3D Registration Analysis for Longitudinal Study of Second-Generation HR-pQCT

OBJECTIVE

The objective of this research was to develop 3D registration analysis method in longitudinal studies of high-resolution peripheral quantitative computed tomography (HR-pQCT), to analyze ranges of bone microstructure parameters in addition to standard parameters, and to test the precision of these measurements.

METHODS

Scans of HR-pQCT and analysis of bone microstructure were performed at 3 times in 15 subjects. The 3 images were matched 3-dimensionally, and bone microstructures were analyzed in the common region. In addition to standard measurement parameters of geometry, bone mineral density (BMD), trabecular bone, and cortical bone, parameters showing plate to rod-like structure, connectivity, cavity formation of trabecular bone, and bending stability of cortical bone were also measured. Precision was evaluated with the root mean square percent coefficient variance (RMS%CV).

RESULTS

RMS%CV was 0.1%-1.3% for geometry, 0.6%-1.9% for BMD, 0.8%-3.3% for trabecular bone, 2.1%-9.8% for additionally measured trabecular bone, 1.0%-3.4% for cortical bone excluding Ct.Po, 6.0%-6.1% for Ct.Po, and 0.8%-1.5% for additionally measured cortical bone. Precision was higher for 3D registration than for 2D registration in geometry, BV/TV, and Ct.Po.

CONCLUSIONS

3D registration analysis of a range of bone microstructural parameters in longitudinal analysis of HR-pQCT showed good precision, offering potential for contributing to future research on osteoporosis and bone metabolic diseases.

Bone health assessment via digital wrist tomosynthesis in the mammography setting

Bone fractures attributable to osteoporosis are a significant problem. Though preventative treatment options are available for individuals who are at risk of a fracture, a substantial number of these individuals are not identified due to lack of adherence to bone screening recommendations. The issue is further complicated as standard diagnosis of osteoporosis is based on bone mineral density (BMD) derived from dual energy x-ray absorptiometry (DXA), which, while helpful in identifying many at risk, is limited in fully predicting risk of fracture. It is reasonable to expect that bone screening would become more prevalent and efficacious if offered in coordination with digital breast tomosynthesis (DBT) exams, provided that osteoporosis can be assessed using a DBT modality. Therefore, the objective of the current study was to explore the feasibility of using digital tomosynthesis imaging in a mammography setting. To this end, we measured density, cortical thickness and microstructural properties of the wrist bone, correlated these to reference measurements from microcomputed tomography and DXA, demonstrated the application in vivo in a small group of participants, and determined the repeatability of the measurements. We found that measurements from digital wrist tomosynthesis (DWT) imaging with a DBT scanner were highly repeatable ex vivo (error = 0.05%-9.62%) and in vivo (error = 0.06%-10.2%). In ex vivo trials, DWT derived BMDs were strongly correlated with reference measurements (R = 0.841-0.980), as were cortical thickness measured at lateral and medial cortices (R = 0.991 and R = 0.959, respectively) and the majority of microstructural measures (R = 0.736-0.991). The measurements were quick and tolerated by human patients with no discomfort, and appeared to be different between young and old participants in a preliminary comparison. In conclusion, DWT is feasible in a mammography setting, and informative on bone mass, cortical thickness, and microstructural qualities that are known to deteriorate in osteoporosis. To our knowledge, this study represents the first application of DBT for imaging bone. Future clinical studies are needed to further establish the efficacy for diagnosing osteoporosis and predicting risk of fragility fracture using DWT.

In vivo repeatability of homogenized finite element analysis based on multiple HR-pQCT sections for assessment of distal radius and tibia strength

INTRODUCTION

Micro finite element analysis (μFE) is a widely applied tool in biomedical research for assessing in vivo mechanical properties of bone at measurement sites, including the ultra-distal radius and tibia. A finite element approach (hFE) based on homogenized constitutive models for trabecular bone offers an attractive alternative for clinical use, as it is computationally less expensive than traditional μFE. The respective patient-specific models for in vivo bone strength estimation are usually based on standard clinical high-resolution peripheral quantitative CT (HR-pQCT) measurements. They include a scan region of roughly 10 mm in height and are referred to as single-sections. It has been shown, that these small peripheral bone sections don't reliably cover the fracture line in Colles' fractures and therefore the weakest region at the radius. Recently introduced multiple section (multiple adjacent single-sections) measurements might improve the evaluation of bone strength, but little is known about the repeatability of hFE estimations in general, and especially for multiple section measurement protocols. Accordingly, the aim of the present work is to quantify repeatability of clinical in vivo bone strength measurement by hFE on multiple section HR-pQCT reconstructions at the distal radius and tibia.

METHODS

Nineteen healthy Swiss women (43.6y ± 17.8y) and twenty men (48.2y ± 19.4y) were examined with HR-pQCT at 61 μm isotropic voxel resolution. Each subject was first scanned three times using a double-section (336 slices) at the distal radius and then three times using a triple-section (504 slices) at the distal tibia. The multiple section HR-pQCT reconstructions were graded for motion artefacts and non-linear hFE models (radius and tibia) and linear μFE models (only radius) were generated for estimation of stiffness and ultimate load. Then in vivo repeatability errors were computed in terms of root mean square coefficients of variation (CV).

RESULTS

In vivo repeatability errors of non-linear hFE stiffness (S) and ultimate load (F) were significantly higher at the radius (S: 2.71% and F: 2.97%) compared to the tibia (S: 1.21%, F: 1.45%). Multiple section linear μFE at the radius resulted in substantially higher repeatability errors (S: 5.38% and F: 10.80%) compared to hFE.

DISCUSSION/CONCLUSION

Repeatability errors of hFE outcomes based on multiple section measurements at the distal radius and tibia were generally lower compared to respective reported single-section μFE repeatability errors. Therefore, hFE is an attractive alternative to today's gold standard of μFE models and should especially be encouraged when analyzing multiple section measurements.

HR-pQCT Measures of Bone Microarchitecture Predict Fracture: Systematic Review and Meta-Analysis

High-resolution peripheral quantitative computed tomography (HR-pQCT) is a noninvasive imaging modality for assessing volumetric bone mineral density (vBMD) and microarchitecture of cancellous and cortical bone. The objective was to (1) assess fracture-associated differences in HR-pQCT bone parameters; and (2) to determine if HR-pQCT is sufficiently precise to reliably detect these differences in individuals. We systematically identified 40 studies that used HR-pQCT (39/40 used XtremeCT scanners) to assess 1291 to 3253 and 3389 to 10,687 individuals with and without fractures, respectively, ranging in age from 10.9 to 84.7 years with no comorbid conditions. Parameters describing radial and tibial bone density, microarchitecture, and strength were extracted and percentage differences between fracture and control subjects were estimated using a random effects meta-analysis. An additional meta-analysis of short-term in vivo reproducibility of bone parameters assessed by XtremeCT was conducted to determine whether fracture-associated differences exceeded the least significant change (LSC) required to discern measured differences from precision error. Radial and tibial HR-pQCT parameters, including failure load, were significantly altered in fracture subjects, with differences ranging from -2.6% (95% confidence interval [CI] -3.4 to -1.9) in radial cortical vBMD to -12.6% (95% CI -15.0 to -10.3) in radial trabecular vBMD. Fracture-associated differences reported by prospective studies were consistent with those from retrospective studies, indicating that HR-pQCT can predict incident fracture. Assessment of study quality, heterogeneity, and publication biases verified the validity of these findings. Finally, we demonstrated that fracture-associated deficits in total and trabecular vBMD and certain tibial cortical parameters can be reliably discerned from HR-pQCT-related precision error and can be used to detect fracture-associated differences in individual patients. Although differences in other HR-pQCT measures, including failure load, were significantly associated with fracture, improved reproducibility is needed to ensure reliable individual cross-sectional screening and longitudinal monitoring. In conclusion, our study supports the use of HR-pQCT in clinical fracture prediction. © 2019 American Society for Bone and Mineral Research.

Reliability of Annual Changes and Monitoring Time Intervals for Bone Strength, Size, Density, and Microarchitectural Development at the Distal Radius and Tibia in Children: A 1-Year HR-pQCT Follow-Up

High-resolution peripheral quantitative computed tomography (HR-pQCT) imaging, together with computational finite element analysis (FEA), offers an attractive, noninvasive tool to quantify bone strength development in pediatric studies. Evidence of annual changes and errors in repeated HR-pQCT measures is limited, and time intervals required to reliably capture changes in children's bone strength or microarchitecture have not yet been defined. Our objectives were: (1) to quantify annual changes in bone strength and microarchitectural properties; (2) to define precision errors for pediatric bone strength outcomes; (3) to characterize annual changes in contrast to pediatric precision errors; and (4) to estimate monitoring time intervals (MTIs) required to reliably characterize bone development at the distal radius and tibia. We obtained distal radius (7% of ulnar length) and tibia (8%) bone properties using HR-pQCT and FEA from 38 follow-up study participants (21 girls) at baseline (mean age 10.6 years, SD 1.7 years) and after 1 year; and from 32 precision study participants (16 girls) at baseline (mean age 11.3 years, SD 1.6 years) and after 1 week. We characterized mean annual changes (paired t tests) contrasted to pediatric precision errors (CV%_RMS ) and estimated MTIs. Annual increases in bone strength, total area, cortical thickness, and density ranged between 3.0% and 25.3% and 2.4% and 15.6% at the distal radius and tibia, respectively. Precision errors for all bone strength outcomes were ≤6.8% and ≤5.1% at the distal radius and tibia, respectively, and appeared lower than annual gains in bone strength at both sites. Cortical porosity decreased 19.6% at the distal radius and 6.6% at the distal tibia; these changes exceeded respective precision errors, indicating cortical bone consolidation. MTIs ranged between 0.5 years and infinity at the distal radius and 0.5 and 5.9 years at the distal tibia. Estimated MTIs suggest that pediatric bone strength, cortical bone density, and porosity development can be reliably monitored with annual measurements. © 2019 American Society for Bone and Mineral Research.

Precision of Second-Generation High-Resolution Peripheral Quantitative Computed Tomography: Intra- and Intertester Reproducibilities and Factors Involved in the Reproducibility of Cortical Porosity

High-resolution peripheral quantitative computed tomography (HR-pQCT) was upgraded to a second generation in 2014 with higher spatial resolution, faster scan time, and a different measurement algorithm. The purpose of this study was to investigate the precision of the second-generation HR-pQCT. The distal radius and tibia of 15 healthy men and women (age range of 20-74 yr, 8 men and 7 women) were scanned by second-generation HR-pQCT, and their geometry, bone mineral density (BMD), and the microstructure of trabecular and cortical bones were evaluated. Scans and measurements were performed by tester 1 at baseline and at 1 and 4 wk to evaluate intratester reproducibility, and by testers 2 and 3 one time each to evaluate intertester reproducibility. Reproducibility was evaluated by root mean square percent coefficient of variance (RMS%CV). Factors involved in the reproducibility of cortical porosity (Ct.Po) were also investigated. The ranges of RMS%CV were 0.2%-2.5% for geometry, 0.6%-1.7% for BMD, 0.7%-2.4% for trabecular bone, and 1.1%-1.3% for cortical thickness, showing excellent reproducibility. The range of RMS%CV for Ct.Po was 11.0%-13.3%, relatively higher than those for the other parameters. There was no apparent difference between intra- and intertester reproducibilities. There was no clear correlation between the percent coefficient of variance of Ct.Po and the subjects' background characteristics, motion artifact, and cortical bone structure. The reproducibility of the second-generation HR-pQCT was excellent in geometry, BMD, trabecular bone, and cortical thickness, with no apparent difference between intra- and intertester reproducibilities. Compared with the first-generation HR-pQCT, the reproducibility of trabecular bone was improved. The reproducibility of Ct.Po was insufficient and needed to be improved, and factors that influence its reproducibility were not clear.

Precision of bone density and micro-architectural properties at the distal radius and tibia in children: an HR-pQCT study

Precision errors need to be known when monitoring bone micro-architecture in children with HR-pQCT. Precision errors for trabecular bone micro-architecture ranged from 1 to 8% when using the standard evaluation at the radius and tibia. Precision errors for cortical bone micro-architecture ranged from 1 to 11% when using the advanced cortical evaluation.

INTRODUCTION

Our objective was to define HR-pQCT precision errors (CV%_RMS) and least significant changes (LSCs) at the distal radius and tibia in children using the standard evaluation and the advanced cortical evaluation.

METHODS

We scanned the distal radius (7% of ulnar length) and tibia (8% of tibia length) of 32 children (age range 8-13; mean age 11.3; SD 1.6 years) twice (1 week apart) using HR-pQCT (XtremeCT1). We calculated root-mean-squared coefficients of variation (CV%_RMS) to define precision errors and LSC to identify differences required to detect change.

RESULTS

Precision errors ranged between 1-8 and 1-5% for trabecular bone outcomes (obtained with standard evaluation) and between 1.5-11 and 0.5-6% for cortical bone outcomes (obtained with advanced cortical evaluation) at the distal radius and tibia, respectively. Related LSCs ranged between 3-21 and 3-14% for trabecular bone outcomes and between 4-30 and 2-16% for cortical bone outcomes at the distal radius and tibia, respectively.

CONCLUSIONS

HR-pQCT precision errors were between 1 and 8% (LSC 3-21%) for trabecular bone outcomes and 1 and 11% (LSC 2-30%) for cortical bone outcomes at the radius and tibia in children. Cortical bone outcomes obtained using the advanced cortical evaluation appeared to have lower precision errors than cortical outcomes derived using the standard evaluation. These findings, combined with better-defined cortical bone contours with advanced cortical evaluation, indicate that metrics from advanced cortical evaluation should be utilized when monitoring cortical bone properties in children.

Cross-sectional Versus Longitudinal Change in a Prospective HR-pQCT Study

Longitudinal studies assessing age-related changes using high-resolution peripheral quantitative computed tomography (HR-pQCT) provide novel insight compared with cross-sectional analyses. The purpose of this cohort study was 1) to determine individuals' change in HR-pQCT parameters over 5 years relative to least significant change (LSC), and 2) to evaluate if predicted rate of change from cross-sectional data is comparable to actual change from longitudinal investigation. A cohort of 466 (162 male, 304 female) participants completed two HR-pQCT scans with 5 years between assessments. After image registration, standard and cortical morphological analyses were conducted. Rate of bone microarchitectural change was compared between cross-sectional models and actual change calculated from longitudinal analyses. At the young end of the life span, we observed gains in total bone density of +0.2% to +2.9% per year, whereas the older participants (aged >50 years) lost total bone density at a rate of -0.3% to -1.3% per year. Declines in total bone density begin at age 40 years in females and 60 years in males, and significant adaptation was found at both ends of the age spectrum with respect to the LSC. Models predicting rate of change from cross-sectional data were similar to the actual change reported in this longitudinal study for total density and cortical thickness at the radius and cortical density at the tibia, but we found that changes in comparison to our 5-year longitudinal results were often overestimated from cross-sectional data. Studies aimed at observing age-related changes in a normative cohort, especially in a follow-up period of less than 5 years, are better to focus on the tibia rather than the radius because of the increased sensitivity to change at the tibia. © 2017 American Society for Bone and Mineral Research.

In vivo precision of three HR-pQCT-derived finite element models of the distal radius and tibia in postmenopausal women

Background

The distal radius is the most common osteoporotic fracture site occurring in postmenopausal women. Finite element (FE) modeling is a non-invasive mathematical technique that can estimate bone strength using inputted geometry/micro-architecture and tissue material properties from computed tomographic images. Our first objective was to define and compare in vivo precision errors for three high-resolution peripheral quantitative computed tomography (HR-pQCT, XtremeCT; Scanco) based FE models of the distal radius and tibia in postmenopausal women. Our second objective was to assess the role of scan interval, scan quality, and common region on precision errors of outcomes for each FE model.

Methods

Models included: single-tissue model (STM), cortical-trabecular dual-tissue model (DTM), and one scaled model using imaged bone mineral density (E-BMD). Using HR-pQCT, we scanned the distal radius and tibia of 34 postmenopausal women (74 ± 7 years), at two time points. Primary outcomes included: tissue stiffness, apparent modulus, average von Mises stress, and failure load. Precision errors (root-mean-squared coefficient of variation, CV%_RMS) were calculated. Multivariate ANOVA was used to compare the mean of individual CV% among the 3 HR-pQCT-based FE models. Spearman correlations were used to characterize the associations between precision errors of all FE model outcomes and scan/time interval, scan quality, and common region. Significance was accepted at P < 0.05.

Results

At the distal radius, CV%_RMS precision errors were <9 % (Range STM: 2.8–5.3 %; DTM: 2.9–5.4 %; E-BMD: 4.4–8.7 %). At the distal tibia, CV%_RMS precision errors were <6 % (Range STM: 2.7–4.8 %; DTM: 2.9–3.8 %; E-BMD: 1.8–2.5 %). At the radius, Spearman correlations indicated associations between the common region and associated precision errors of the E-BMD-derived apparent modulus (ρ = −0.392; P < 0.001) and von Mises stress (ρ = −0.297; P = 0.007).

Conclusion

Results suggest that the STM and DTM are more precise for modeling apparent modulus, average von Mises stress, and failure load at the distal radius. Precision errors were comparable for all three models at the distal tibia. Results indicate that the noted differences in precision error at the distal radius were associated with the common scan region, illustrating the importance of participant repositioning within the cast and reference line placement in the scout view during the scanning process.

Role of endocortical contouring methods on precision of HR-pQCT-derived cortical micro-architecture in postmenopausal women and young adults

Precision errors of cortical bone micro-architecture from high-resolution peripheral quantitative computed tomography (pQCT) ranged from 1 to 16 % and did not differ between automatic or manually modified endocortical contour methods in postmenopausal women or young adults. In postmenopausal women, manually modified contours led to generally higher cortical bone properties when compared to the automated method.

INTRODUCTION

First, the objective of the study was to define in vivo precision errors (coefficient of variation root mean square (CV%RMS)) and least significant change (LSC) for cortical bone micro-architecture using two endocortical contouring methods: automatic (AUTO) and manually modified (MOD) in two groups (postmenopausal women and young adults) from high-resolution pQCT (HR-pQCT) scans. Second, it was to compare precision errors and bone outcomes obtained with both methods within and between groups.

METHODS

Using HR-pQCT, we scanned twice the distal radius and tibia of 34 postmenopausal women (mean age ± SD 74 ± 7 years) and 30 young adults (27 ± 9 years). Cortical micro-architecture was determined using AUTO and MOD contour methods. CV%RMS and LSC were calculated. Repeated measures and multivariate ANOVA were used to compare mean CV% and bone outcomes between the methods within and between the groups. Significance was accepted at P < 0.05.

RESULTS

CV%RMS ranged from 0.9 to 16.3 %. Within-group precision did not differ between evaluation methods. Compared to young adults, postmenopausal women had better precision for radial cortical porosity (precision difference 9.3 %) and pore volume (7.5 %) with MOD. Young adults had better precision for cortical thickness (0.8 %, MOD) and tibial cortical density (0.2 %, AUTO). In postmenopausal women, MOD resulted in 0.2-54 % higher values for most cortical outcomes, as well as 6-8 % lower radial and tibial cortical BMD and 2 % lower tibial cortical thickness.

CONCLUSIONS

Results suggest that AUTO and MOD endocortical contour methods provide comparable repeatability. In postmenopausal women, manual modification of endocortical contours led to generally higher cortical bone properties when compared to the automated method, while no between-method differences were observed in young adults.