Sex differences in trabecular bone microarchitecture are not detected in pre and early pubertal children using magnetic resonance imaging

Hormonal Control of Bone Architecture Throughout the Lifespan: Implications for Fracture Prediction and Prevention

BACKGROUND

Skeletal modeling in childhood and adolescence and continuous remodeling throughout the lifespan are designed to adapt to a changing environment and resist external forces and fractures. The flux of sex steroids in men and women, beginning from fetal development and evolving through infancy, childhood, puberty, young adulthood, peri/menopause transition, and postmenopause, is critical for bone size, peak bone mass, and fracture resistance.

OBJECTIVE

This review will highlight how changes in sex steroids throughout the lifespan affect bone cells and the consequence of these changes on bone architecture and strength.

METHODS

Literature review and discussion.

RESULTS

The contributions of estrogen and testosterone on skeletal development have been difficult to study due to the reciprocal and intertwining contributions of one on the other. Although orchiectomy in men renders circulating testosterone absent, circulating estrogen also declines due to testosterone being the substrate for estradiol. The discovery of men with absent estradiol or resistance to estrogen and the study of mouse models led to the understanding that estrogen has a larger direct role in skeletal development and maintenance in men and women. The mechanistic reason for larger bone size in men is incompletely understood but related to indirect effects of testosterone on the skeleton, such as higher muscle mass leading to larger mechanical loading. Declines in sex steroids during menopause in women and androgen deprivation therapies in men have profound and negative effects on the skeleton. Therapies to prevent such bone loss are available, but how such therapies can be tailored based on bone size and architecture remains an area of investigation.

CONCLUSION

In this review, the elegant interplay and contribution of sex steroids on bone architecture in men and women throughout the lifespan is described.

3T-MRI-based age, sex and site-specific markers of musculoskeletal health in healthy children and young adults

Objective

The aim of this study is to investigate the role of 3T-MRI in assessing musculoskeletal health in children and young people.

Design

Bone, muscle and bone marrow imaging was performed in 161 healthy participants with a median age of 15.0 years (range, 8.0, 30.0).

Methods

Detailed assessment of bone microarchitecture (constructive interference in the steady state (CISS) sequence, voxel size 0.2 × 0.2 × 0.4 mm3), bone geometry (T1-weighted turbo spin echo (TSE) sequence, voxel size 0.4 × 0.4 × 2 mm3) and bone marrow (1H-MRS, point resolved spectroscopy sequence (PRESS) (single voxel size 20 × 20 × 20 mm3) size and muscle adiposity (Dixon, voxel size 1.1 × 1.1 × 2 mm3).

Results

There was an inverse association of apparent bone volume/total volume (appBV/TV) with age (r = -0.5, P < 0.0005). Cortical area, endosteal and periosteal circumferences and muscle cross-sectional area showed a positive association to age (r > 0.49, P < 0.0001). In those over 17 years of age, these parameters were also higher in males than females (P < 0.05). This sex difference was also evident for appBV/TV and bone marrow adiposity (BMA) in the older participants (P < 0.05). AppBV/TV showed a negative correlation with BMA (r = -0.22, P = 0.01) which also showed an association with muscle adiposity (r = 0.24, P = 0.04). Cortical geometric parameters were highly correlated with muscle area (r > 0.57, P < 0.01).

Conclusions

In addition to providing deep insight into the normal relationships between bone, fat and muscle in young people, these novel data emphasize the role of MRI as a non-invasive method for performing a comprehensive and integrated assessment of musculoskeletal health in the growing skeleton.

Accurate Age Determination for Adolescents Using Magnetic Resonance Imaging of the Hand and Wrist with an Artificial Neural Network-Based Approach

This study proposes an accurate method in assessing chronological age of the adolescents using a machine learning approach using MRI images. We also examined the value of MRI with Tanner-Whitehouse 3 (TW3) method in assessing skeletal maturity. Seventy-nine 12-17-year-old healthy Hong Kong Chinese adolescents were recruited. The left hand and wrist region were scanned by a dedicated skeletal MRI scanner. T1-weighted three-dimensional coronal view images for the left hand and wrist region were acquired. Independent maturity indicators such as subject body height, body weight, bone marrow composition intensity quantified by MRI, and TW3 skeletal age were included for artificial neural network (ANN) analysis. Our results indicated that the skeletal age was generally underestimated using TW3 method, and significant difference (p < 0.05) was noted for skeletal age with chronological age for female category and at later stage of adolescence (15 to 17 years old) in both genders. In our proposed machine learning approach, ages determined by ANN method agreed well with chronological age (p > 0.05).The machine learning approach using ANN method was about 10-fold more accurate than the TW3 method using MRI alone. It offers a more objective and accurate solution for prospective chronological maturity assessment for adolescents.

Update on bone density measurements and their interpretation in children and adolescents

Following the increased awareness about the central role of the pediatric age in building bone for life, clinicians face more than ever the necessity of assessing bone health in pediatric subjects at risk for early bone mass derangements or in healthy children, in order to optimize their bone mass accrual and prevent osteoporosis. Although the diagnosis of osteoporosis is not made solely upon bone mineral density measurements during growth, such determination can be very useful in the follow-up of pediatric patients with primary and secondary osteoporosis. The ideal instrument would give information on the mineral content and density of the bone, and on its architecture. It should be able to perform the measurements on the skeletal sites where fractures are more frequent, and it should be minimally invasive, accurate, precise and rapid. Unfortunately, none of the techniques currently utilized fulfills all requirements. In the present review, we focus on the pediatric use of dual-energy X-ray absorptiometry (DXA), quantitative computed tomography (QCT), peripheral QCT (pQCT), and magnetic resonance imaging (MRI), highlighting advantages and limits for their use and providing indications for bone densitometry interpretation and of vertebral fractures diagnosis in pediatric subjects.

The persistence of epiphyseal scars in the distal radius in adult individuals

The use of radiographic imaging in the estimation of chronological age facilitates the analysis of structures not visible on gross morphological inspection. Following the completion of epiphyseal fusion, a thin radio-opaque band, the epiphyseal scar, may be observed at the locus of the former growth plate. The obliteration of this feature has previously been interpreted as the final stage of skeletal maturation and consequently has been included as a criterion in several methods of age estimation, particularly from the distal radius. Due to the recommendations relating to age estimation in living individuals, accurate assessment of age from the distal radius is of great importance in human identification; however, the validity of the interpretation of the obliteration of the epiphyseal scar as an age-related process has not been tested. A study was undertaken to assess the persistence of epiphyseal scars in adults between 20 and 50 years of age through the assessment of 616 radiographs of left and right distal radii from a cross-sectional population. This study found that 86% of females and 78% of males retained some remnant of the epiphyseal scar in the distal radius. The relationships between chronological age, biological sex and the persistence of the epiphyseal scar were not statistically significant. The findings of this study indicate that the epiphyseal scars may persist in adult individuals until at least 50 years of age. No maximum age should therefore be applied to the persistence of an epiphyseal scar in the distal radius.

Underdevelopment of trabecular bone microarchitecture in the distal femur of nonambulatory children with cerebral palsy becomes more pronounced with distance from the growth plate

SUMMARY

We found that the underdeveloped trabecular bone microarchitecture in the distal femur of children with cerebral palsy (CP) who are unable to ambulate independently becomes more pronounced with increased distance from the growth plate. This suggests that the degree of underdevelopment in trabecular bone in children with CP is greater than previously understood.

INTRODUCTION

Children with CP who are unable to ambulate independently have severely underdeveloped trabecular bone microarchitecture in the distal femur. The aim of the study was to determine if the level of underdevelopment in trabecular bone microarchitecture is consistent across the distal femur in children with CP.

METHODS

Children with quadriplegic CP and typically developing children were studied (n=12/group, 5-14 years). Apparent bone volume to total volume (appBV/TV), trabecular number (appTb.N), trabecular thickness (appTb.Th), and trabecular separation (appTb.Sp) were estimated in each of 20 magnetic resonance images collected above the growth plate in the distal femur.

RESULTS

For the total region, appBV/TV, appTb.N, and appTb.Th were lower (30, 21, and 12%, respectively) and appTb.Sp was higher (52%) (all p≤0.001) in children with CP than in controls. Distance from the growth plate was inversely related to appBV/TV and appTb.N and was positively related to appTb.Sp at the same distance in children with CP and controls (all p<0.01). However, the relationships were stronger (r2=0.87 to 0.92 versus 0.36 to 0.65) and the slopes were steeper in children with CP (all p<0.01). Furthermore, the steepness of the slopes in children with CP was positively related to appBV/TV, appTb.N, appTb.Th, and appTb.Sp for the total region (r2=0.37 to 0.75, p<0.05).

CONCLUSIONS

The underdeveloped trabecular bone microarchitecture in the metaphysis of the distal femur in children with CP becomes more pronounced with greater distance from the growth plate. This pattern is most profound in children with the least developed trabecular bone microarchitecture.

The pattern of trabecular bone microarchitecture in the distal femur of typically developing children and its effect on processing of magnetic resonance images

INTRODUCTION

Magnetic resonance imaging (MRI) is used to assess trabecular bone microarchitecture in humans; however, image processing can be labor intensive and time consuming. One aim of this study was to determine the pattern of trabecular bone microarchitecture in the distal femur of typically developing children. A second aim was to determine the proportion and location of magnetic resonance images that need to be processed to yield representative estimates of trabecular bone microarchitecture.

MATERIALS AND METHODS

Twenty-six high resolution magnetic resonance images were collected immediately above the growth plate in the distal femur of 6-12year-old typically developing children (n=40). Measures of trabecular bone microarchitecture [i.e., apparent trabecular bone volume to total volume (appBV/TV), trabecular number (appTb.N), trabecular thickness (appTb.Th) and trabecular separation (appTb.Sp)] in the lateral aspect of the distal femur were determined using the twenty most central images (20IM). The average values for appBV/TV, appTb.N, appTb.Th and appTb.Sp from 20IM were compared to the average values from 10 images (10IM), 5 images (5IM) and 3 images (3IM) equally dispersed throughout the total image set and one image (1IM) from the center of the total image set using linear regression analysis. The resulting mathematical models were cross-validated using the leave-one-out technique.

RESULTS

Distance from the growth plate was strongly and inversely related to appBV/TV (r(2)=0.68, p<0.001) and appTb.N (r(2)=0.92, p<0.001) and was strongly and positively related to appTb.Sp (r(2)=0.86, p<0.001). The relationship between distance from the growth plate and appTb.Th was not linear (r(2)=0.06, p=0.28), but instead it was quadratic and statistically significant (r(2)=0.54, p<0.001). Trabecular bone microarchitecture estimates from 10IM, 5IM, 3IM and 1IM were not different from estimates from 20IM (p>0.05). However, there was a progressive decrease in the strength of the relationships as a smaller proportion of images were used to predict estimates from 20IM (r(2)=0.98 to 0.99 using 10IM, 0.94 to 0.96 using 5IM, 0.87 to 0.90 using 3IM and 0.66 to 0.72 using 1IM; all p<0.001). Using the resulting mathematical models and the leave-one-out cross-validation analysis, measures of trabecular bone microarchitecture estimated from the 10IM and 5IM partial image sets agreed extremely well with estimates from 20IM.

CONCLUSIONS

The findings indicate that partial magnetic resonance image sets can be used to provide reasonable estimates of trabecular bone microarchitecture status in the distal femur of typically developing children. However, because the relative amount of trabecular bone in the distal femur decreases with distance from the growth plate due to a decrease in trabecular number, careful positioning of the region of interest and sampling from throughout the region of interest is necessary.