The biomechanical basis of vertebral body fragility in men and women

Assessment of age-dependent sexual dimorphism in paediatric vertebral size and density using a statistical shape and statistical appearance modelling approach

This work focuses on the growth patterns of the human fourth lumbar vertebra (L4) in a paediatric population, with specific attention to sexual dimorphism. The study aims to understand morphological and density changes in the vertebrae through age-dependent statistical shape and statistical appearance models, which can describe full three-dimensional anatomy. Results show that the main growth patterns are associated with isotropic volumetric vertebral growth, a decrease in the relative size of the vertebral foramen, and an increase in the length of the transverse processes. Moreover, significant sexual dimorphism was demonstrated during puberty. We observe significant age and sex interaction in the anterior vertebral body height (P = 0.005), where females exhibited an earlier increase in rates of vertebral height evolution. Moreover, we also observe an increase in cross-sectional area (CSA) with age (P = 0.020), where the CSA is smaller in females than in males (significant sex effect P = 0.042). Finally, although no significant increase in trabecular bone density with age is observed (P = 0.363), a trend in the statistical appearance model suggests an increase in density with age.

Challenges in Orthopedic Surgical Decision-Making for Multilevel Vertebrae Fractures

Vertebral fractures commonly occur in postmenopausal women due to decreased bone density, a condition known as osteoporosis. They can occur after minimal trauma or even during routine activities. Vertebral fractures occur predominantly in individuals with a high fall risk. This case report explores the clinical complexities surrounding a 65-year-old female patient with a history of multilevel vertebrae fractures compounded by a history of chronic smoking, osteoporosis, multiple falls, and evident signs of osteopenia on X-ray. These risk factors complicate the decision to perform surgery and highlight the importance of constantly weighing the benefits and possible risks. This paper aims to emphasize the gender-specific challenges healthcare providers encounter when assessing surgical risks in the context of postmenopausal females with significant comorbidities. It underlines the need for tailored and comprehensive care strategies to manage orthopedic conditions in high-risk female individuals, further aligning with one of the World Health Organization's concerns on addressing gender-specific health considerations.

Breaking strength and bone microarchitecture in osteoporosis: a biomechanical approximation based on load tests in 104 human vertebrae from the cervical, thoracic, and lumbar spines of 13 body donors

Background

The purpose of the study was to investigate associations between biomechanical resilience (failure load, failure strength) and the microarchitecture of cancellous bone in the vertebrae of human cadavers with low bone density with or without vertebral fractures (VFx).

Methods

Spines were removed from 13 body donors (approval no. A 2017-0072) and analyzed in regard to bone mineral density (BMD), Hounsfield units (HU), and fracture count (Fx) with the aid of high-resolution CT images. This was followed by the puncture of cancellous bone in the vertebral bodies of C2 to L5 using a Jamshidi™ needle. The following parameters were determined on the micro-CT images: bone volume fraction (BVF), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), degree of anisotropy (DA), trabecular number (Tb.N), trabecular pattern factor (Tb.Pf), and connectivity density (Conn.D). The axial load behavior of 104 vertebral specimens (C5, C6, T7, T8, T9, T12, L1, L3) was investigated with a servohydraulic testing machine.

Results

Individuals with more than 2 fractures had a significantly lower trabecular pattern factor (Tb.Pf), which also proved to be an important factor for a reduced failure load in the regression analysis with differences between the parts of the spine. The failure load (FL) and endplate sizes of normal vertebrae increased with progression in the craniocaudal direction, while the HU was reduced. Failure strength (FS) was significantly greater in the cervical spine than in the thoracic or lumbar spine (p < 0.001), independent of sex. BVF, Tb.Th, Tb.N, and Conn.D were significantly higher in the cervical spine than in the other spinal segments. In contrast, Tb.Sp and Tb.Pf were lowest in the cervical spine. BVF was correlated with FL (r = 0.600, p = 0.030) and FS (r = 0.763, p = 0.002). Microarchitectural changes were also detectable in the cervical spine at lower densities.

Conclusions

Due to the unique microarchitecture of the cervical vertebrae, fractures occur much later in this region than they do in the thoracic or lumbar spine.

Trial registration

Approval no. A 2017-0072.

Physical Activity at Growth Induces Bone Mass Benefits Into Adulthood – A Fifteen‐Year Prospective Controlled Study

Daily school physical activity (PA) improves musculoskeletal traits. Whether or not benefits remain in adulthood is debated. We included in this study 131 children that took part in an intervention with 40 minutes of PA per school day (200 minutes per week) from age 6 to 9 years (grade one) to age 14 to 16 years (grade nine), whereas 78 children continued with national recommended school physical education of 60 minutes per week. Measurements were done with dual‐energy X‐ray absorptiometry (bone mineral content [BMC], bone mineral density [BMD], and bone area), and a computerized knee dynamometer (peak torque muscle strength) at study start, at the end of the intervention, and 7 years after the intervention. Group differences from study start and end of the intervention to 7 years thereafter were estimated by analyses of covariance (adjusted for sex and follow‐up time). Musculoskeletal gains from study start to 7 years after termination of the intervention were higher in the intervention group (total body less head BMC +182.5 g [95% confidence interval {CI}, 55.1–309.9] and BMD +0.03 g/cm² [95% CI, 0.003–0.05], femoral neck area + 0.2 cm² [95% CI, 0.1–0.4], and knee flexion peak torque muscle strength at 60 degrees per second +9.2 Nm [95% CI, 2.9–15.5]). There was no attenuation during the 7 years that followed termination of the intervention (all group comparisons p > 0.05). Benefits in musculoskeletal gains remain 7 years after termination of a daily school‐based PA program, without attenuation after termination of the program. Daily school PA may counteract low bone mass and inferior muscle strength in adulthood. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Associations between bone attenuation and prevalent vertebral fractures on chest CT scans differ with vertebral fracture locations

Vertebral fracture (VF) locations are bimodally distributed in the spine. The association between VF and bone attenuation (BA) measured on chest CT scans varied according to the location of VFs, indicating that other factors than only BA play a role in the bimodal distribution of VFs.

INTRODUCTION

Vertebral fractures (VFs) are associated with low bone mineral density but are not equally distributed throughout the spine and occur most commonly at T7-T8 and T11-T12 ("cVFs") and less commonly at T4-T6 and T9-T10 ("lcVF"). We aimed to determine whether associations between bone attenuation (BA) and VFs vary between subjects with cVFs only, with lcVFs only and with both cVFs and lcVFs.

METHODS

Chest CT images of T4-T12 in 1237 smokers with and without COPD were analysed for prevalent VFs according to the method described by Genant (11,133 vertebrae). BA (expressed in Hounsfield units) was measured in all non-fractured vertebrae (available for 10,489 vertebrae). Linear regression was used to compare mean BA, and logistic regression was used to estimate the association of BA with prevalent VFs (adjusted for age and sex).

RESULTS

On vertebral level, the proportion of cVFs was significantly higher than of lcVF (5.6% vs 2.0%). Compared to subjects without VFs, BA was 15% lower in subjects with cVFs (p < 0.0001), 25% lower in subjects with lcVFs (p < 0.0001) and lowest in subjects with cVFs and lcVFs (- 32%, p < 0.0001). The highest ORs for presence of VFs per - 1SD BA per vertebra were found in subjects with both cVFs and lcVFs (3.8 to 4.6).

CONCLUSIONS

The association between VFs and BA differed according to VF location. ORs increased from subjects with cVFs to subjects with lcVFs and were highest in subjects with cVFs and lcVFs, indicating that other factors than only BA play a role in the bimodal VF distribution.

TRIAL REGISTRATION

Clinicaltrials.gov identifier: NCT00292552.

Association Between Vertebral Dimensions and Lumbar Modic Changes

STUDY DESIGN

Population-based birth cohort study.

OBJECTIVE

The aim of this study was to evaluate the relationship between vertebral dimensions and lumbar MC.

SUMMARY OF BACKGROUND DATA

Low back pain (LBP) has become the leading cause of disability worldwide. Modic changes (MC) of the lumbar spine are one potential LBP-associated etiological factor. Mechanical stress is considered to play a key role in the development of MC through damage to endplates. There is speculation that vertebral dimensions play a role in some degenerative changes in the spine. Previous studies have also shown a positive association between moderate-to-vigorous physical activity (MVPA) and both vertebral dimensions and MC. In this study, we aimed to evaluate the relationship between vertebral dimensions and MC.

METHODS

The study population consisted of 1221 participants from the Northern Finland Birth Cohort 1966 who underwent lumbar magnetic resonance imaging (MRI) and physical activity measurements at the age of 46-48. The presence of Type 1 (MC1) and Type 2 (MC2) MC and the height, axial cross-sectional area (CSA), and volume of the L4 vertebra were determined from MRI scans. MVPA (≥3.5 metabolic equivalents) was measured by a wrist-worn accelerometer. We analyzed the association between lumbar MC and vertebral height, CSA, and volume using logistic regression models before and after adjustment for sex, height, weight, smoking, education level, and MVPA.

RESULTS

Vertebral height was positively associated with the presence of MC2 (odds ratio [OR] 3.51; 95% confidence interval [CI] 1.43-8.65), whereas vertebral CSA was not associated with the presence of lumbar MC. Vertebral volume was positively associated with the presence of any MC (OR 1.04; 95% CI 1.00-1.07), but the association did not persist when analyzing MC1 and MC2 separately.

CONCLUSION

Vertebral height was associated with the presence of MC2. Further studies are needed to clarify the role of vertebral dimensions as independent risk factors for MC.Level of Evidence: 3.

Obstructive Sleep Apnea and Risk for Incident Vertebral and Hip Fracture in Women

Recent studies suggest a positive association between obstructive sleep apnea (OSA), a disorder associated with intermittent hypoxia and sleep fragmentation, and derangements in bone metabolism. However, no prospective study to date has investigated the association between OSA and fracture risk in women. We conducted a prospective study examining the relation between OSA and risk of incident vertebral fracture (VF) and hip fracture (HF) in the Nurses' Health Study. History of physician-diagnosed OSA was assessed by self-reported questionnaires. A previous validation study demonstrated high concordance between self-reports and medical record identification of OSA. OSA severity was further categorized according to the presence or absence of self-reported sleepiness. Self-reports of VF were confirmed by medical record review. Self-reported HF was assessed by biennial questionnaires. Cox proportional-hazards models estimated the hazard ratio for fracture according to OSA status, adjusted for potential confounders, including BMI, physical activity, calcium intake, history of osteoporosis, and falls, and use of sleep medications. Among 55,264 women without prior history of fracture, physician-diagnosed OSA was self-reported in 1.3% in 2002 and increased to 3.3% by 2012. Between 2002 and 2014, 461 incident VF cases and 921 incident HF cases were documented. The multivariable-adjusted hazard ratio (HR) for confirmed VF for women with history of OSA was 2.00 (95% CI, 1.29-3.12) compared with no OSA history, with the strongest association observed for OSA with daytime sleepiness (HR 2.86; 95% CI, 1.31-6.21). No association was observed between OSA history and self-reported HF risk (HR 0.83; 95% CI, 0.49-1.43). History of OSA is independently associated with higher risk of confirmed VF but did not have a statistically significant association with self-reported HF in women. Further research is warranted in understanding the role of OSA and intermittent hypoxia in bone metabolism and health that may differ by fracture site. © 2020 American Society for Bone and Mineral Research (ASBMR).

Radiographic osteoporotic vertebral fractures in elderly men: a brief review focusing on differences between the sexes

Bone loss occurs in both sexes as a result of ageing but is exacerbated in women by the hormonal changes associated with menopause. Unlike in women, secondary osteoporosis occurs in almost half of men diagnosed with osteoporosis. Moreover, vertebral fractures (VFs) seen in elderly men may more likely be the result of high energy trauma. The osteoporotic vertebral fracture (OVF) radiograph diagnosis criteria for women may not be directly applicable for men. Particular attention should be paid to the mid-thoracic level where over-diagnosis commonly occurs. For wedge-shaped vertebral deformities (VDs) or VDs with anterior height reduction only, a diagnosis of OVF requires great caution, as they are poorly correlated to bone mineral density (BMD). For age-matched subjects, it is likely that elderly men's prevalent radiographic OVFs are approximately half of the elderly women's. This male-female ratio is very similar to other clinical fractures such as those occurring at the hip. Even so, the clinical relevance of OVF in elderly men may be less than that of elderly women. On the other hand, for elderly men with hip BMD-based osteoporosis, the OVF risk is as high as that of osteoporotic women. Elderly Chinese men have a lower OVF prevalence than age-matched Caucasian men.

Sex estimation of skeletons in middle and late adulthood: reliability of pelvic morphological traits and long bone metrics on an Italian skeletal collection

There are several metric and morphological methods available for sex estimation of skeletal remains, but their reliability and applicability depend on the sexual dimorphism of the remains as well as on the availability of preserved bones. Some studies showed that age-related changes on bones can cause misclassification of sex. The purpose of this study was to establish the reliability of pelvic morphological traits and metric methods of sex estimation on relatively old individuals from a modern Italian skeletal collection. The data for this study were obtained from 164 individuals of the Milano CAL skeletal collection and average age of the samples was 75 years. In the pelvic morphological method, the recalibrated regression formula of Klales and colleagues (2012), pre-auricular sulcus, and greater sciatic notch morphology were used for sex estimation. With regard to the metric method, 15 standard measurements from upper and lower limbs were analyzed for sexual dimorphism. The results showed that in pelvic morphological approach, the application of regression formula of the revised Klales and colleague formula (2017) resulted in 100% accuracy. Classification rates of metric methods vary from 75.19 to 90.73% with the maximum epiphyseal breadth of proximal tibia representing the most discriminant parameter. This study confirms that the effect of age on sex estimation methods is not substantial, and both metric and morphological methods of sex estimation can be reliably applied to individuals of Italian descent in middle and late adulthood.

Changes in vertebral dimensions in early adulthood - A 10-year follow-up MRI-study

Previous studies have shown that vertebral height increases until the early twenties, but very few studies have been conducted on other vertebral dimensions. Growth in vertebral size is believed to take place in elderly age but not in early adulthood. In this study, we wanted to clarify the potential changes in the dimensions of the lumbar vertebrae during early adulthood. We used the Northern Finland Birth Cohort 1986 as our study material, with a final sample size of 375 individuals. We performed lumbar magnetic resonance imaging (MRI) when the participants were 20 and 30 years of age (baseline and follow-up, respectively). We recorded the width, depth, height, and cross-sectional area (CSA) of the fourth lumbar vertebra (L4) using the MRI scans. We used generalized estimating equation (GEE) models to analyse the data. Men had 7.6%-26.5% larger vertebral dimensions than women at both baseline and follow-up. The GEE models demonstrated that all the studied dimensions increased during the follow-up period among both sexes (p < 0.001). Men had a higher growth rate in vertebral depth and CSA than women (p < 0.001). Among women, small vertebral width (p = 0.001), depth (p = 0.05) and height (p = 0.02) at baseline were associated with a higher vertebral growth rate during the follow-up than among those with large dimensions at baseline. Among men, small baseline width was associated with higher vertebral growth rate (p = 0.001). Our results clearly indicate that vertebral dimensions increase after 20 years of age among both sexes.

Proton Pump Inhibitor Use, H2-Receptor Antagonist Use, and Risk of Incident Clinical Vertebral Fracture in Women

The few prospective studies examining the relation between proton pump inhibitor (PPI) use and risk of vertebral fracture (VF) suggest a higher risk, but the magnitude of the association has been inconsistent. Moreover, no prospective studies have examined the association between substantially longer duration of PPI use and VF risk. Our objective was to determine the association between PPI use, H₂RA use, and incident clinical VF in women. We conducted a prospective study in 55,545 women participating in the Nurses' Health Study. PPI and H₂RA use was assessed by questionnaire every 4 years. Self-reports of VF were confirmed by medical record. Our analysis included 547 incident VF cases (2002-2014). The multivariate adjusted relative risk (MVRR) of VF for women taking PPIs was 1.29 (95% CI 1.04-1.59) compared with non-users. Longer duration of PPI use was associated with higher VF risk (MVRR 1.16 [0.90-1.49] for < 4 years; 1.27 [0.93-1.73] for 4-7.9 years; 1.64 [1.02-2.64] for ≥ 8 years; p_trend = 0.01). The MVRR of VF for women taking H₂RAs was 1.22 (0.90-1.67) compared with non-users. Longer duration of H₂RA use was not associated with VF risk (MVRR 1.16 [0.88-1.53] for < 4 years; 0.98 [0.60-1.59] for ≥ 4 years; p_trend = 0.72). PPI use is independently associated with a modestly higher risk of VF and the risk increases with longer duration of use. There was no statistically significant association between H₂RA use and VF risk. Our findings add to the growing evidence suggesting caution with PPI use, particularly with longer duration of use.

Increased Lumbar Lordosis and Smaller Vertebral Cross-Sectional Area Are Associated With Spondylolysis

STUDY DESIGN

A cross-sectional comparison of vertebral morphology and lumbar lordosis (LL) in adolescents with and without spondylolysis.

OBJECTIVE

To test the hypothesis that in addition to LL, vertebral cross-sectional area (CSA) is also associated with spondylolysis.

SUMMARY OF BACKGROUND DATA

Recent data indicate that the CSA of the vertebral body is a determinant of LL, which has been shown to be associated with spondylolysis.

METHODS

Using magnetic resonance imaging, we compared the degree of LL from L1 to L5 and the CSA of the lumbar vertebrae in 35 adolescents (16 females and 19 males) with spondylolysis and 86 healthy controls (36 females and 50 males) of similar sex, age, height, and weight.

RESULTS

There were no significant differences in age, height, weight, or vertebral height between subjects with and without spondylolysis, regardless of sex. In contrast, LL angle in spondylolysis patients was 57% and 51% greater in girls and boys with spondylolysis; 44.1 ± 10.4° versus 28.1 ± 9.8° and 34.8 ± 5.9° versus 23.0 ± 6.0° for girls and boys, respectively (both P's < 0.0001). Additionally, values for vertebral CSA were on average, 8% and 10% smaller in females and males with spondylolysis; 7.6 ± 0.8 cmversus 8.3 ± 1.1 cm and 8.4 ± 1.6 versus 9.3 ± 1.6 for girls and boys, respectively (both P's ≤ 0.039). Multiple linear and logistic regression analyses indicated that the CSA of the vertebral body was negatively associated with LL angle and an independent predictor of the presence of spondylolysis. This was true regardless of whether girls and boys were analyzed together or independently, and whether LL angle was measured from L1 to L5 or S1.

CONCLUSION

We provide evidence that patients with spondylolysis have increased LL and smaller vertebral CSA.

LEVEL OF EVIDENCE

4.

A meta-analysis of the association between body mass index and risk of vertebral fracture

We conducted a meta-analysis of prospective studies to assess the association between BMI and incident vertebral fracture. We found that as body mass index (BMI) increases, the risk of vertebral fracture decreases in men, but not in women, suggesting possible gender differences in the relationship of BMI with risk of vertebral fracture.

INTRODUCTION

Recent evidence suggests that the relationship between BMI and fracture risk may be site-specific. We conducted a systematic review and meta-analysis of prospective studies to investigate the association between BMI and risk of incident vertebral fracture.

METHODS

PubMed and Embase were searched for relevant articles published from inception through February 15, 2017. Extracted relative risks (RR) from the prospective studies were pooled using random-effects meta-analysis.

RESULTS

Six studies were included, with a total of 105,129 participants followed for 3 to 19 years. The pooled RR (95% confidence interval [CI]) for vertebral fracture per each standard deviation increase in BMI was 0.94 (95% CI = 0.80-1.10) with significant heterogeneity (I ² = 88.0%, p < 0.001). In subgroup analysis by gender, we found a significant inverse association between BMI and risk of vertebral fracture in men (RR = 0.85, 95% CI = 0.73-0.98, n = 25,617 participants) but not in women (RR = 0.98, 95% CI = 0.81-1.20, n = 79,512 participants). Across studies of women not adjusting for bone mineral density (BMD), there was no significant association between BMI and risk of vertebral fracture (RR = 0.91, 95% CI = 0.80-1.04, p = 0.18, n = 72,755 participants). However, BMI was associated with an increased risk of vertebral fracture in studies of women that adjusted for BMD (RR = 1.28, 95% CI = 1.17-1.40, p < 0.001, n = 6757 participants). Substantial heterogeneity was found among studies of women (I ² = 90.1%, p < 0.001), which was partly explained by the adjustment for BMD (adjusted R ² = 61%). We found no evidence of publication bias (p = 0.40).

CONCLUSIONS

In conclusion, our findings suggest that there might be gender differences in the relationship of BMI with risk of vertebral fracture. Further research is needed, including the assessment of other measures of adiposity, such as visceral adiposity, on the risk of vertebral fracture.

Vertebral cross-sectional growth: A predictor of vertebral wedging in the immature skeleton

The degree of vertebral wedging, a key structural characteristic of spinal curvatures, has recently been found to be negatively related to vertebral cross-sectional area (CSA). The purpose of this longitudinal study was to examine the relation between vertebral cross-sectional growth and vertebral wedging progression within the immature lumbar spine. Using magnetic resonance imaging (MRI), we analyzed the potential association between increases in lumbar vertebral CSA and changes in L5 vertebral wedging in 27 healthy adolescent girls (ages 9–13 years) twice within a two-year period. Vertebral CSA growth was negatively associated with changes in posteroanterior vertebral wedging (r = -0.61; p = 0.001). Multiple regression analysis showed that this relation was independent of gains in age, height, and weight. When compared to the 14 girls whose vertebral wedging progressed, the 13 subjects whose vertebral wedging decreased had significantly greater vertebral cross-sectional growth (0.39 ± 0.25 vs. 0.75 ± 0.23 cm²; p = 0.001); in contrast, there were no significant differences in increases in age, height, or weight between the two groups. Changes in posteroanterior vertebral wedging and the degree of lumbar lordosis (LL) positively correlated (r = 0.56, p = 0.002)—an association that persisted even after adjusting for gains in age, height, and weight. We concluded that in the immature skeleton, vertebral cross-sectional growth is an important determinant of the plasticity of the vertebral body; regression of L5 vertebral wedging is associated with greater lumbar vertebral cross-sectional growth, while progression is the consequence of lesser cross-sectional growth.

Association Between Vertebral Cross-sectional Area and Vertebral Wedging in Children and Adolescents: A Cross-sectional Analysis

A small vertebral cross-sectional area (CSA) imparts a mechanical disadvantage that escalates the risk for vertebral fractures in elderly populations. We examined whether a small vertebral CSA is also associated with a greater degree of vertebral wedging in children. Measurements of vertebral CSA, lumbar lordosis (LL) or thoracic scoliosis angle, and vertebral wedging were obtained in 100 healthy adolescents (50 boys and 50 girls) and 25 girls with adolescent idiopathic scoliosis (AIS) using magnetic resonance imaging. Vertebral CSA of the lumbar vertebrae negatively correlated to the degree of posteroanterior vertebral wedging at L₅ (r = -0.49; p < 0.0001); this was true whether all subjects were analyzed together or boys and girls independently. In contrast, we found a positive correlation between the degree of LL and vertebral wedging (r = 0.57; p < 0.0001). Multiple regression analysis showed that the association between vertebral CSA and wedging was independent of age and body mass index. In girls with AIS, vertebral CSA negatively correlated to the degree of lateral thoracic vertebral wedging (r = -0.66; p = 0.0004), an association that persisted even after accounting for age and body mass index. Additionally, Cobb angle positively correlated to lateral thoracic vertebral wedging (r = 0.46; p = 0.021). Our cross-sectional results support the hypothesis that smaller vertebral CSA is associated with greater vertebral deformity during growth, as in adulthood. © 2017 American Society for Bone and Mineral Research.

Clinical guidelines for the prevention and treatment of osteoporosis: summary statements and recommendations from the Italian Society for Orthopaedics and Traumatology

BACKGROUND

The Italian Society for Orthopaedics and Traumatology conceived this guidance-which is primarily addressed to Italian orthopedic surgeons, but should also prove useful to other bone specialists and to general practitioners-in order to improve the diagnosis, prevention, and treatment of osteoporosis and its consequences.

MATERIALS AND METHODS

Literature reviews by a multidisciplinary team.

RESULTS

The following topics are covered: the role of instrumental, metabolic, and genetic evaluations in the diagnosis of osteoporosis; appraisal of the risk of fracture and thresholds for intervention; general strategies for the prevention and treatment of osteoporosis (primary and secondary prevention); the pharmacologic treatment of osteoporosis; the setting and implementation of fracture liaison services for tertiary prevention. Grade A, B, and C recommendations are provided based on the main levels of evidence (1-3). Toolboxes for everyday clinical practice are provided.

CONCLUSIONS

The first up-to-date Italian guidelines for the primary, secondary, and tertiary prevention of osteoporosis and osteoporotic fractures are presented.

Diuretic Use and Risk of Vertebral Fracture in Women

BACKGROUND

Vertebral fracture is the most common type of osteoporotic fracture. While thiazide diuretics, which are commonly prescribed for the treatment of hypertension, decrease calciuria, they may also induce hyponatremia, which has been associated with increased vertebral fracture risk. Loop diuretics increase calciuria, which would reduce bone mineral density and increase vertebral fracture risk, but they rarely cause hyponatremia. Recent studies on diuretics and fractures did not include or specifically examine vertebral fracture. The few studies of diuretics and vertebral fracture have been limited by cases defined by self-report or administrative data, relatively small number of cases, study design that was not prospective, and lack of long-term follow-up with updated information on diuretic use.

METHODS

We conducted a prospective cohort study of thiazide diuretic use, loop diuretic use, and risk of incident clinical vertebral fracture in 55,780 women, 55-82 years of age, participating in the Nurses' Health Study, without a prior history of any fracture. Diuretic use was assessed by questionnaire every 4 years. Self-reported vertebral fracture was confirmed by medical record review. Cox proportional-hazards models were used to simultaneously adjust for potential confounders.

RESULTS

Our analysis included 420 incident vertebral fracture cases documented between 2002 and 2012. The multivariate-adjusted relative risk of clinical vertebral fracture for women taking thiazides compared with women not taking thiazides was 1.47 (95% confidence interval, 1.18-1.85). The multivariate adjusted relative risk of vertebral fracture for women taking loop diuretics compared with women not taking loop diuretics was 1.59 (95% confidence interval, 1.12-2.25).

CONCLUSION

Thiazide diuretics and loop diuretics are each independently associated with increased risk of vertebral fracture in women.

An Increase in Forearm Cortical Bone Size After Menopause May Influence the Estimated Bone Mineral Loss--A 28-Year Prospective Observational Study

Areal bone mineral density (aBMD) is the most common estimate of bone mass, incorporated in the World Health Organization definition of osteoporosis. However, aBMD depends on not only the amount of mineral but also the bone size. The estimated postmenopausal decline in aBMD could because of this be influenced by changes in bone size.We measured bone mineral content (BMC; mg), aBMD (mg/cm2), and bone width (mm) by single-photon absorptiometry at the cortical site of the forearm in a population-based sample of 105 Caucasian women. We conducted 12 measurements during a 28-yr period from mean 5 yr (range: 2-9) before menopause to mean 24 yr (range: 18-28) after menopause. We calculated individual slopes for changes in the periods before menopause, 0-<8, 8-<16, and 16-28 yr after menopause. Data are presented as means with 95% confidence intervals. The annual BMC changes in the 4 periods were -1.4% (-0.1, -2.6), -1.1% (-0.9, -1.4), -1.2% (-0.9, -1.6), and -1.1% (-0.8, -1.4) and the annual increase in bone width 0.4% (-1.2, 1.9), 0.7% (0.5, 0.9), 0.1% (-0.2, 0.4), and 0.1% (-0.2, 0.4). BMC loss was similar in all periods, whereas the increase in bone width was higher in the first postmenopausal period than in the second (p=0.003) and the third (p=0.01) postmenopausal periods. Menopause is followed by a transient increase in forearm bone size that will influence the by aBMD estimated cortical loss in bone minerals.

A biomechanical sorting of clinical risk factors affecting osteoporotic hip fracture

Osteoporotic fracture has been found associated with many clinical risk factors, and the associations have been explored dominantly by evidence-based and case-control approaches. The major challenges emerging from the studies are the large number of the risk factors, the difficulty in quantification, the incomplete list, and the interdependence of the risk factors. A biomechanical sorting of the risk factors may shed lights on resolving the above issues. Based on the definition of load-strength ratio (LSR), we first identified the four biomechanical variables determining fracture risk, i.e., the risk of fall, impact force, bone quality, and bone geometry. Then, we explored the links between the FRAX clinical risk factors and the biomechanical variables by looking for evidences in the literature. To accurately assess fracture risk, none of the four biomechanical variables can be ignored and their values must be subject-specific. A clinical risk factor contributes to osteoporotic fracture by affecting one or more of the biomechanical variables. A biomechanical variable represents the integral effect from all the clinical risk factors linked to the variable. The clinical risk factors in FRAX mostly stand for bone quality. The other three biomechanical variables are not adequately represented by the clinical risk factors. From the biomechanical viewpoint, most clinical risk factors are interdependent to each other as they affect the same biomechanical variable(s). As biomechanical variables must be expressed in numbers before their use in calculating LSR, the numerical value of a biomechanical variable can be used as a gauge of the linked clinical risk factors to measure their integral effect on fracture risk, which may be more efficient than to study each individual risk factor.

Male Osteoporosis in the Elderly

Osteoporosis is now recognized as an important public health problem in elderly men as fragility fractures are complicated by increased morbidity, mortality, and social costs. This review comprises an overview of recent findings in pathophysiology, diagnosis, and treatment of male osteoporosis, with particular regard to the old population.

Osteoporosis: the emperor has no clothes

Current prevention strategies for low-trauma fractures amongst older persons depend on the notions that fractures are mainly caused by osteoporosis (pathophysiology), that patients at high risk can be identified (screening) and that the risk is amenable to bone-targeted pharmacotherapy (treatment). However, all these three notions can be disputed.

PATHOPHYSIOLOGY

Most fracture patients have fallen, but actually do not have osteoporosis. A high likelihood of falling, in turn, is attributable to an ageing-related decline in physical functioning and general frailty.

SCREENING

Currently available fracture risk prediction strategies including bone densitometry and multifactorial prediction tools are unable to identify a large proportion of patients who will sustain a fracture, whereas many of those with a high fracture risk score will not sustain a fracture.

TREATMENT

The evidence for the viability of bone-targeted pharmacotherapy in preventing hip fracture and other clinical fragility fractures is mainly limited to women aged 65-80 years with osteoporosis, whereas the proof of hip fracture-preventing efficacy in women over 80 years of age and in men at all ages is meagre or absent. Further, the antihip fracture efficacy shown in clinical trials is absent in real-life studies. Many drugs for the treatment of osteoporosis have also been associated with increased risks of serious adverse events. There are also considerable uncertainties related to the efficacy of drug therapy in preventing clinical vertebral fractures, whereas the efficacy for preventing other fractures (relative risk reductions of 20-25%) remains moderate, particularly in terms of the low absolute risk reduction in fractures with this treatment.

Age-related trends in vertebral dimensions

Several studies have demonstrated age-related changes in vertebral dimensions. Vertebral size has been reported to increase among elderly adults, with periosteal apposition resulting in increased cross-sectional area (CSA) of the vertebral corpus combined with reduction in bone mineral density. These changes in CSA are observed to be sex-specific, as the pronounced increase of vertebral CSA is found only in elderly males. However, the reduction in bone mineral density in old age is apparent within both sexes. It is thus hypothesized that higher fracture risk in elderly women is a result of their incapacity to increase vertebral size and thus adapt to bone mineral reduction. In this study, our aim was to explore whether the onset of these changes could be ascribed to specific age intervals and whether the proposed differences between the sexes are as great as previously suggested. To conduct this study we utilized two large early 20th century skeletal collections known as Terry and Bass (n = 181). We also utilized data from two lumbar spine magnetic resonance imaging samples as a modern-day reference (n = 497). Age, sex and ethnicity of all individuals were known. Vertebral CSA was determined by measuring three width and length dimensions from the corpus of the fourth lumbar vertebra (L4). Our results indicate only a moderate association between age and vertebral CSA. This association was observed to be relatively similar in both sexes, and we thus conclude that there is no clear sex-specific compensatory mechanism for age-related bone loss in vertebral size.

Pubertal timing, bone acquisition, and risk of fracture throughout life

Pubertal maturation plays a fundamental role in bone acquisition. In retrospective epidemiological surveys in pre- and postmenopausal women, relatively later menarcheal age was associated with low bone mineral mass and increased risk of osteoporotic fracture. This association was usually ascribed to shorter time exposure to estrogen from the onset of pubertal maturation to peak bone mass attainment. Recent prospective studies in healthy children and adolescents do not corroborate the limited estrogen exposure hypothesis. In prepubertal girls who will experience later menarche, a reduced bone mineral density was observed before the onset of pubertal maturation, with no further accumulated deficit until peak bone mass attainment. In young adulthood, later menarche is associated with impaired microstructural bone components and reduced mechanical resistance. This intrinsic bone deficit can explain the fact that later menarche increases fracture risk during childhood and adolescence. In healthy individuals, both pubertal timing and bone development share several similar characteristics including wide physiological variability and strong effect of heritable factors but moderate influence of environmental determinants such as nutrition and physical activity. Several conditions modify pubertal timing and bone acquisition, a certain number of them acting in concert on both traits. Taken together, these facts should prompt the search for common genetic regulators of pubertal timing and bone acquisition. It should also open epigenetic investigation avenues to pinpoint which environmental exposure in fetal and infancy life, such as vitamin D, calcium, and/or protein supplies, influences both pubertal timing and bone acquisition.

Quantification of pediatric and adult cervical vertebra-anatomical characteristics by age and gender for automotive application

OBJECTIVE

The cervical anatomy has been shown to affect injury patterns in vehicle crashes. Characterizing the spine anatomy and changes associated with growth and gender is important when assessing occupant protection. In this study, selected cervical characteristics were quantified.

METHODS

Computed tomography (CT) scans of 750 patients were selected from the University of Michigan trauma database; 314 were children and 436 were adults. Four variables were obtained: the maximum spinal canal radius, vertebral body depth, facet angles, and retroversion angles.

RESULTS

The cervical spine measurements varied with age and gender. The body depth increased nonlinearly with age. The average vertebral body depth at C4 was 9.2 ± 0.38 mm in the 0-3 age group, 15.7 ± 0.29 mm in the 18-29 age group, and 17.2 ± 0.46 mm in the 60+ age group. Pediatric and adult males had larger vertebral body depth than females overall, irrespective of vertebral level (P <.001). Compared to females, the vertebral body depth was 8-9 percent greater in male children and 13-16 percent greater in adult males. The average radius varied with gender, with male children generally having a larger radius than females irrespective of vertebral level (P <.001). Overall, spinal canal radius was smallest in the 0-3 and 60+ age groups and largest in the 18-29 age group. The C4 radius was 5.91 ± 0.17, 6.28 ± 0.14, and 6.73 ± 0.17 mm respectively. The radius was larger in the 4-7 age group than in the 0-3 age group, irrespective of vertebral level (P <.0001). There were nonsignificant radius changes between the 4-7 and 8-11 age groups and the 8-11 and age 12-17 groups, suggesting that the size of the spinal cord reaches near maturation by the age of 7. Facet angles decreased with age in children and increased with age in adults. The average facet angles were largest in the 0-3 age group (P <.1, C2-C6). Adult facet angles were greater in the 60+ age group than in the 18-29 age group (P <.0001, C2-C6). Males had larger facet angles than females overall (P <.01 at C2, C5-C7). The retroversion angles were largest at C6 and C7. They increased with age in children and decreased in the adult population; they were larger (5-22%) in the 18-29 age group than in the 60+ age group (P <.0001, C2-C6).

CONCLUSIONS

The results obtained in this study help explain variations in cervical anatomical changes associated with age and gender. The information is useful when assessing differences in injury patterns between different segments of the population. Anatomical measurements of the cervical spine should be considered for the development of models used to assess injury mechanisms for various occupant age groups.

The predictive value of trabecular bone score (TBS) on whole lumbar vertebrae mechanics: an ex vivo study

We investigated the association of trabecular bone score (TBS) with microarchitecture and mechanical behavior of human lumbar vertebrae. We found that TBS reflects vertebral trabecular microarchitecture and is an independent predictor of vertebral mechanics. However, the addition of TBS to areal BMD (aBMD) did not significantly improve prediction of vertebral strength.

INTRODUCTION

The trabecular bone score (TBS) is a gray-level measure of texture using a modified experimental variogram which can be extracted from dual-energy X-ray absorptiometry (DXA) images. The current study aimed to confirm whether TBS is associated with trabecular microarchitecture and mechanics of human lumbar vertebrae, and if its combination with BMD improves prediction of fracture risk.

METHODS

Lumbar vertebrae (L3) were harvested fresh from 16 donors. The anteroposterior and lateral bone mineral content (BMC) and areal BMD (aBMD) of the vertebral body were measured using DXA; then, the TBS was extracted using TBS iNsight software (Medimaps SA, France). The trabecular bone volume (Tb.BV/tissue volume, TV), trabecular thickness (Tb.Th), degree of anisotropy, and structure model index (SMI) were measured using microcomputed tomography. Quasi-static uniaxial compressive testing was performed on L3 vertebral bodies to assess failure load and stiffness.

RESULTS

The TBS was significantly correlated to Tb.BV/TV and SMI (r = 0.58 and -0.62; p = 0.02, 0.01), but not related to BMC and BMD. TBS was significantly correlated with stiffness (r = 0.64; p = 0.007), independently of bone mass. Using stepwise multiple regression models, we failed to demonstrate that the combination of BMD and TBS was better at explaining mechanical behavior than either variable alone. However, the combination TBS, Tb.Th, and BMC did perform better than each parameter alone, explaining 79% of the variability in stiffness.

CONCLUSIONS

In our study, TBS was associated with microarchitecture parameters and with vertebral mechanical behavior, but TBS did not improve prediction of vertebral biomechanical properties in addition to aBMD.

A 5-year exercise program in pre- and peripubertal children improves bone mass and bone size without affecting fracture risk

We studied the effect in children of an exercise intervention program on fracture rates and skeletal traits. Fractures were registered for 5 years in a population-based prospective controlled exercise intervention study that included children aged 6-9 years at study start, 446 boys and 362 girls in the intervention group and 807 boys and 780 girls in the control group. Intervention subjects received 40 min/school day of physical education and controls, 60 min/week. In 73 boys and 48 girls in the intervention group and 52 boys and 48 girls in the control group, bone mineral density (BMD, g/cm(2)) and bone area (mm(2)) were followed annually by dual-energy X-ray absorptiometry, after which annual changes were calculated. At follow-up we also assessed trabecular and cortical volumetric BMD (g/cm(3)) and bone structure by peripheral computed tomography in the tibia and radius. There were 20.0 fractures/1,000 person-years in the intervention group and 18.5 fractures/1,000 person-years in the control group, resulting in a rate ratio of 1.08 (0.79-1.47) (mean and 95 % CI). The gain in spine BMD was higher in both girls (difference 0.01 g/cm(2), 0.005-0.019) and boys (difference 0.01 g/cm(2), 0.001-0.008) in the intervention group. Intervention girls also had higher gain in femoral neck area (difference 0.04 mm(2), 0.005-0.083) and at follow-up larger tibial bone mineral content (difference 0.18 g, 0.015-0.35), larger tibial cortical area (difference 17 mm(2), 2.4-31.3), and larger radial cross-sectional area (difference 11.0 mm(2), 0.63-21.40). As increased exercise improves bone mass and in girls bone size without affecting fracture risk, society ought to encourage exercise during growth.

Bone mass following physical activity in young years: a mean 39-year prospective controlled study in men

This is a study on exercise-associated bone mineral density (BMD) which in men is maintained three decades after cessation of sports. In this prospective controlled cohort study active athletes had a BMD Z-score of 1.0 and after 39 years 0.5 to 1.2 depending on the measured region), using the same single-photon absorptiometry device, dual X-ray absorptiometry (DXA), and peripheral computed tomography (pQCT).

INTRODUCTION

The aims of this study were to prospectively evaluate BMD changes in male athletes from activity into long-term retirement and to simultaneously evaluate other bone traits.

METHODS

Bone mineral density (grams per square centimeter) was measured in 46 male athletes with a mean age of 22 years (range, 15-40) by using the same single-photon absorptiometry device, both at active career and a mean of 39 years (range, 38-40) later when they had long-term retired. At follow-up, BMD was also evaluated by DXA and pQCT. Twenty-four non-athletic males of similar age served as controls. Between-group differences are presented as means with 95% confidence intervals.

RESULTS

The active athletes (baseline) had a BMD Z-score of 1.0 (0.7, 1.4) in the femoral condyles. The retired athletes (follow-up) had a BMD Z-score of 0.5 to 1.2 depending on the measuring technique and the measured region. The tibial cortical area Z-score at follow-up was 0.8 (0.5, 1.2) and the tibial strength index Z-score 0.7 (0.4, 1.0). There were no changes in BMD Z-scores from activity to retirement, neither when estimated by the same device in different regions [∆ Z-score -0.3 (-0.8, 0.2)] nor in the same region with different devices [∆ Z-score 0.0 (-0.4, 0.4)]. The benefits remained after adjustments for anthropometrics and lifestyle. No correlation was seen with years since retirement.

CONCLUSIONS

Exercise-associated high BMD in young years seems, in men, to be maintained three decades after cessation of high-level physical activity.

Overuse in volleyball training/practice: A review on shoulder and spine-related injuries

Overuse injuries are predominant in sports involving the repetition of similar movements patterns, such as in volleyball or beach volleyball, and they may represent as much a problem as do acute injuries. This review discusses the prevalence of two of the most common overuse-related injuries in volleyball: shoulder and back/spine injuries. Risk factors and the aetiology of these injuries are illustrated in order to make possible to initiate preventive programme or post-injuries solutions. Data collected from literature showed a moderately higher injury rate for overuse shoulder injuries compared to the back/spine (19.0 ± 11.2% and 16.8 ± 9.7%, respectively). These data could be underestimated, and future epidemiological studies should consider overuse injuries separately from the others, with new methodological approaches. In addition to age, biomechanical and anatomical features of a volleyball technique utilised in game and the amount of hours played are considered as the main risk factors for overuse upper limb injuries, both for professional and recreational athletes. Together with post-injuries solutions, great importance has to be placed on preventive programmes, such as preventive rehabilitation, stretching, adequate warm up, strength-power exercises, etc. Furthermore, it is particularly suggested that coaches and players work together in order to develop new game/training techniques that minimise stresses and range of motion of the principal anatomical structures involved, while maintaining athletes performance.

Computerised analysis of osteoporotic bone patterns using texture parameters characterising bone architecture

OBJECTIVE

To evaluate the geometric change of osteoporotic bone trabecular patterns using root mean square (RMS) values, first moment power spectrum (FMP) values and fractal dimension values. With the use of these methods, we attempted computerised analysis of osteoporotic bone patterns using texture parameters characterising bone architecture and computer-aided diagnosis of osteoporosis.

METHODS

32 patient cases from Korea University Guro Hospital were analysed. Patient ages ranged from 51 to 89 years, with a mean age of 65 years. Receiver operating characteristic curve analysis was performed with determination of the area under the curve (AUC).

RESULTS

The bone mineral density (BMD) measurement (AUC=0.78) was a better indicator of bone quantity than the RMS, FMP and fractal dimension values (AUC=0.72) for diagnosis; therefore the combination of RMS, FMP and fractal dimension values was a better indicator of bone quality.

CONCLUSION

Measurements that combined BMD measurement and RMS values and combined FMP and fractal dimension values (AUC=0.85) together produced better results than the use of the two parameter sets separately for a diagnosis of osteoporosis.

ADVANCES IN KNOWLEDGE

For more effective application, additional study on more cases and data will be required.

Variations in vertebral body dimensions in women measured by 3D-XA: a longitudinal in vivo study

Bone size and shape play an important role in bone strength, as shown by biomechanical testing and clinical studies. Vertebral body dimensions determine vertebral body strength even after adjustment for bone mineral density. We have recently proposed an in vivo method for 3D reconstruction of vertebral bodies using the whole spine imaging on a standard DXA device (3D-XA). The aim of our study was to measure in vivo vertebral body dimension changes by 3D-XA in women over a 6 year period. A total of 174 women were included in this study. They were divided into 3 groups: premenopausal (20-40 years; N=53), postmenopausal women (55-60 years; N=65) and elderly women (70-80 years; N=56). Thoracic and lumbar spine (T4-L4) were reconstructed using the 3D-XA method at baseline and 6 years later. Biochemical markers of bone remodeling were measured at baseline. In premenopausal women, there was an increase in minimal cross-sectional area (minCSA), vertebral body volume as well as end plate width of the lumbar vertebrae, without statistically significant change of these parameters at the thoracic spine; there was no change in anterior heights. In postmenopausal women, there was a decrease in vertebral body anterior height and depth, driven by results in the elderly group at both the thoracic and lumbar spine. Vertebral body width decreased at the thoracic spine but increased at the lumbar spine. MinCSA and volume decreased at the thoracic spine, in contrast with an increase of these 2 parameters at the lumbar spine in early postmenopausal women (55-60 years). In elderly women (70-80 years), the change in minCSA and volume of the lumbar spine was not statistically significant over 6 years. In postmenopausal women, there was no correlation between changes in vertebral dimensions and baseline biochemical markers of bone remodeling except for NTX/Cr and anterior height decrease. Our study confirms that an increase in geometric dimensions of lumbar vertebrae occurs through adult life. This could be related to a compensation for bone loss, aiming to maintain bone strength through increase in size. However, this phenomenon is not observed at all levels in the spine; since we do not confirm this increase at the thoracic spine. This might be one of the determinants of the higher risk of fractures in this part of the spine.

Microarchitectural changes in the aging skeleton

The age-related reduction in bone mass is disproportionally related to skeletal weakening, suggesting that microarchitectural changes are also important determinants of bone quality. The study of cortical and trabecular microstructure, which for many years was mainly based on two-dimensional histologic and scanning electron microscopy imaging, gained a tremendous momentum in the last decade and a half, due to the introduction of microcomputed tomography (μCT). This technology provides highly accurate qualitative and quantitative analyses based on three-dimensional images at micrometer resolution, which combined with finite elemental analysis predicts the biomechanical implications of microstructural changes. Global μCT analyses of trabecular bone have repeatedly suggested that the main age-related change in this compartment is a decrease in trabecular number with unaltered, or even increased, trabecular thickness. However, we show here that this may result from a bias whereby thick trabeculae near the cortex and the early clearance of thin struts mask authentic trabecular thinning. The main cortical age-related change is increased porosity due to negatively balanced osteonal remodeling and expansion of Haversian canals, which occasionally merge with endosteal and periosteal resorption bays, thus leading to rapid cortical thinning and cortical weakening. The recent emergence of CT systems with submicrometer resolution provides novel information on the age-related decrease in osteocyte lacunar density and related micropetrosis, the result of lacunar hypermineralization. Last but not least, the use of the submicrometer CT systems confirmed the occurrence of microcracks in the skeletal mineralized matrix and vastly advanced their morphologic characterization and mode of initiation and propagation.

Towards a diagnostic and therapeutic consensus in male osteoporosis

The consensus views on osteoporosis in men are reported.

INTRODUCTION

A workshop was convened within a meeting on osteoporosis in men to identify areas of consensus amongst the panel (the authors) and the participants of the meeting.

METHODS

A public debate with an expert panel on preselected topics was conducted.

RESULTS AND CONCLUSIONS

Consensus views were reached on diagnostic criteria and several aspects on the pathophysiology and treatment of osteoporosis in men.

Mechanical loading during growth is associated with plane-specific differences in vertebral geometry: A cross-sectional analysis comparing artistic gymnasts vs. non-gymnasts

Lumbar spine geometry, density and indices of bone strength were assessed relative to menarche status, using artistic gymnastics exposure during growth as a model of mechanical loading. Paired posteroanterior (pa) and supine lateral (lat) DXA scans of L3 for 114 females (60 ex/gymnasts and 54 non-gymnasts) yielded output for comparison of paired (palat) versus standard pa and lat outcomes. BMC, areal BMD, vertebral body dimensions, bone mineral apparent density (BMAD), axial compressive strength (IBS) and a fracture risk index were evaluated, modeling vertebral body geometry as an ellipsoid cylinder. Two-factor ANCOVA tested statistical effects of gymnastic exposure, menarche status and their interaction, adjusting for age and height as appropriate. Compared to non-gymnasts, ex/gymnasts exhibited greater paBMD, paBMC, paWidth, pa Cross-sectional area (CSA), paVolume, latBMD, latBMAD, palatCSA and palatIBS (p<0.05). Non-gymnasts exhibited greater latDepth/paWidth, latBMC/paBMC, latVHeight, latArea and Fracture Risk Index. Using ellipsoid vertebral geometric models, no significant differences were detected for pa or palat BMAD. In contrast, cuboid model results (Carter et al., 1992) suggested erroneous ex/gymnast paBMAD advantages, resulting from invalid assumptions of proportional variation in linear skeletal dimensions. Gymnastic exposure was associated with shorter, wider vertebral bodies, yielding greater axial compressive strength and lower fracture risk, despite no BMAD advantage. Our results suggest the importance of plane-specific vertebral geometric adaptation to mechanical loading during growth. Paired scan output provides a more accurate assessment of this adaptation than pa or lat plane scans alone.

Human evolution and osteoporosis-related spinal fractures

The field of evolutionary medicine examines the possibility that some diseases are the result of trade-offs made in human evolution. Spinal fractures are the most common osteoporosis-related fracture in humans, but are not observed in apes, even in cases of severe osteopenia. In humans, the development of osteoporosis is influenced by peak bone mass and strength in early adulthood as well as age-related bone loss. Here, we examine the structural differences in the vertebral bodies (the portion of the vertebra most commonly involved in osteoporosis-related fractures) between humans and apes before age-related bone loss occurs. Vertebrae from young adult humans and chimpanzees, gorillas, orangutans, and gibbons (T8 vertebrae, n = 8–14 per species, male and female, humans: 20–40 years of age) were examined to determine bone strength (using finite element models), bone morphology (external shape), and trabecular microarchitecture (micro-computed tomography). The vertebrae of young adult humans are not as strong as those from apes after accounting for body mass (p<0.01). Human vertebrae are larger in size (volume, cross-sectional area, height) than in apes with a similar body mass. Young adult human vertebrae have significantly lower trabecular bone volume fraction (0.26±0.04 in humans and 0.37±0.07 in apes, mean ± SD, p<0.01) and thinner vertebral shells than apes (after accounting for body mass, p<0.01). Since human vertebrae are more porous and weaker than those in apes in young adulthood (after accounting for bone mass), even modest amounts of age-related bone loss may lead to vertebral fracture in humans, while in apes, larger amounts of bone loss would be required before a vertebral fracture becomes likely. We present arguments that differences in vertebral bone size and shape associated with reduced bone strength in humans is linked to evolutionary adaptations associated with bipedalism.

Variability of trabecular microstructure is age-, gender-, race- and anatomic site-dependent and affects stiffness and stress distribution properties of human vertebral cancellous bone

Cancellous bone microstructure is an important determinant of the mechanical integrity of vertebrae. The numerous microstructural parameters that have been studied extensively are generally represented as a single value obtained as an average over a sample. The range of the intra-sample variability of cancellous microstructure and its effect on the mechanical properties of bone are less well-understood. The objectives of this study were to investigate the extent to which human cancellous bone microstructure within a vertebra i) is related to bone modulus and stress distribution properties and ii) changes along with age, gender and locations thoracic 12 (T12) vs lumbar 1 (L1). Vertebrae were collected from 15 male (66±15 years) and 25 female (54±16 years) cadavers. Three dimensional finite element models were constructed using microcomputed tomography images of cylindrical specimens. Linear finite element models were used to estimate apparent modulus and stress in the cylinders during uniaxial compression. The intra-specimen mean, standard deviation (SD) and coefficient of variation (CV) of microstructural variables were calculated. Mixed model statistical analysis of the results demonstrated that increases in the intra-specimen variability of the microstructure contribute to increases in the variability of trabecular stresses and decreases in bone stiffness. These effects were independent from the contribution from intra-specimen average of the microstructure. Further, the effects of microstructural variability on bone stiffness and stress variability were not accounted for by connectivity and anisotropy. Microstructural variability properties (SD, CV) generally increased with age, were greater in females than in males and in T12 than in L1. Significant interactions were found between age, gender, vertebra and race. These interactions suggest that microstructural variability properties varied with age differently between genders, races and vertebral levels. The current results collectively demonstrate that microstructural variability has a significant effect on mechanical properties and tissue stress of human vertebral cancellous bone. Considering microstructural variability could improve the understanding of bone fragility and improve assessment of vertebral fracture risk.

Functional interactions among morphologic and tissue quality traits define bone quality

BACKGROUND

Advances in diagnostic and treatment regimens that aim to reduce fracture incidence will benefit from a better understanding of how bone morphology and tissue quality define whole-bone mechanical properties.

QUESTIONS/PURPOSES

The goal of this article was to review what is known about the interactions among morphologic and tissue quality traits and how these interactions contribute to bone quality (ie, whole-bone mechanical function). Several questions were addressed. First, how do interactions among morphology and tissue quality traits relate to functional adaptation? Second, what are the emergent patterns of functionally adapted trait sets in long bones? Third, how effective is phenotypic integration at establishing function across a population? Fourth, what are the emergent patterns of functionally adapted trait sets in corticocancellous structures? Fifth, how do functional interactions change with aging?

METHODS

A literature review was conducted with papers identified primarily through citations listed in reference sections as well as general searches using Google Scholar and PubMed.

RESULTS

The interactions among adult traits or phenotypic integration are an emergent property of the compensatory mechanisms complex systems used to establish function or homeostasis. Traits are not regulated independently but vary simultaneously (ie, covary) in specific ways to establish function. This covariation results in individuals acquiring unique sets of traits to establish bone quality.

CONCLUSIONS AND CLINICAL RELEVANCE

Biologic constraints imposed on the skeletal system result in a population showing a pattern of trait sets that is predictable based on external bone size and that can be used to identify individuals with reduced bone quality relative to their bone size and body size.

Influence of a 3-year exercise intervention program on fracture risk, bone mass, and bone size in prepubertal children

Published prospective pediatric exercise intervention studies are short term and use skeletal traits as surrogate endpoints for fractures, whereas other reports infer exercise to be associated with more trauma and fractures. This prospective, controlled exercise intervention study therefore followed both skeletal traits and fracture risk for 36 months. Fractures were registered in children aged 7 to 9 years; there were 446 boys and 362 girls in the intervention group (2129 person-years) and 807 boys and 780 girls in the control group (4430 person-years). The intervention included school physical education of 40 minutes per day for 3 years. The control children achieved the Swedish standard of 60 minutes per week. In a subsample of 76 boys and 48 girls in the intervention group and 55 boys and 44 girls in the control group, bone mineral content (BMC, g) and bone width (cm) were followed in the lumbar spine and hip by dual-energy X-ray absorptiometry (DXA). The rate ratio (RR) for fractures was 1.08 (0.71, 1.62) [mean (95% confidence interval)]. In the DXA-measured children, there were no group differences at baseline in age, anthropometrics, or bone traits. The mean annual gain in the intervention group in lumbar spine BMC was 0.9 SD higher in girls and 0.8 SD higher in boys (both p < .001) and in third lumbar vertebra width 0.4 SD higher in girls and 0.3 SD higher in boys (both p < .05) than in control children. It is concluded that a moderately intense 3-year exercise program in 7- to 9-year-old children increases bone mass and possibly also bone size without increasing fracture risk.

Inter-sex differences in structural properties of aging femora: implications on differential bone fragility: a cadaver study

In this paper we examined age-related and sex-specific deterioration in bone strength of the proximal femur reflected in mechanical properties from dual energy X-ray absorptiometry (DXA)-based hip structural analysis (HSA) on a cadaveric sample from the Balkans. Cadaveric studies permit more precise measurement of HSA parameters and allow further analyses by micromorphometric methods. DXA and HSA analysis was performed on a total of 138 cadaveric proximal femora (63 female, 75 male, age range 20-101 years) from Belgrade. HSA parameters are reported for three standard regions of the proximal femur (narrow neck, intertrochanteric, and shaft). Major age-related findings include an increase in the radius of gyration (first reported in this study), a decline in the cross-sectional area (CSA), a shift in the centroid towards the medial cortex, higher buckling ratios and lower section moduli. Whereas age appears to affect mostly the neck region in men, weakening is also evident in the intertrochanteric region in women, particularly after the age of 80. Aging femoral neck declines in bending strength and increases in buckling susceptibility. The reduced bone mass tends to be distributed farther from the centroidal axis (increase in radius of gyration with decline in CSA). Bone mass is preferentially lost from the lateral part of the cross-section shifting the centroid towards the medial cortex which may increase fragility of the lateral part during fall impact. Results of this study contribute to the epidemiologic data on gender differences and age trends in aging male and female femora.

Vertebral fracture risk (VFR) score for fracture prediction in postmenopausal women

SUMMARY

Early prognosis of osteoporosis risk is not only important to individual patients but is also a key factor when screening for osteoporosis drug trial populations. We present an osteoporosis fracture risk score based on vertebral heights. The score separated individuals who sustained fractures (by follow-up after 6.3 years) from healthy controls at baseline.

INTRODUCTION

This case-control study was designed to assess the ability of three novel fracture risk scoring methods to predict first incident lumbar vertebral fractures in postmenopausal women matched for classical risk factors such as BMD, BMI, and age.

METHODS

This was a case-control study of 126 postmenopausal women, 25 of whom sustained at least one incident lumbar fracture and 101 controls that maintained skeletal integrity over a 6.3-year period. Three methods for fracture risk assessment were developed and tested. They are based on anterior, middle, and posterior vertebral heights measured from vertebrae T12-L5 in lumbar radiographs at baseline. Each score's fracture prediction potential was investigated in two variants using (1) measurements from the single most deformed vertebra or (2) average measurements across vertebrae T12-L5. Emphasis was given to the vertebral fracture risk (VFR) score.

RESULTS

All scoring methods demonstrated significant separation of cases from controls at baseline. Specifically, for the VFR score, cases and controls were significantly different (0.67 ± 0.04 vs. 0.35 ± 0.03, p < 10 (-6)) with an AUC of 0.82. Dividing the VFR scores into tertiles, the fracture odds ratio for the highest versus lowest tertile was 35 (p < 0.001). Sorting the combined case-control group according to VFR score resulted in 90% of cases in the top half.

CONCLUSION

At baseline, the three scores separated cases from controls and, especially, the VFR score appears to be predictive of fractures. Control experiments, however also, indicate that VFR-based fracture prediction is operator/annotator dependent and high-quality annotations are needed for good fracture prediction.

PTH receptor signaling in osteocytes governs periosteal bone formation and intracortical remodeling

The periosteal and endocortical surfaces of cortical bone dictate the geometry and overall mechanical properties of bone. Yet the cellular and molecular mechanisms that regulate activity on these surfaces are far from being understood. Parathyroid hormone (PTH) has profound effects in cortical bone, stimulating periosteal expansion and at the same time accelerating intracortical bone remodeling. We report herein that transgenic mice expressing a constitutive active PTH receptor in osteocytes (DMP1-caPTHR1 mice) exhibit increased cortical bone area and an elevated rate of periosteal and endocortical bone formation. In addition, DMP1-caPTHR1 mice display a marked increase in intracortical remodeling and cortical porosity. Crossing DMP1-caPTHR1 mice with mice lacking the Wnt coreceptor, LDL-related receptor 5 (LRP5), or with mice overexpressing the Wnt antagonist Sost in osteocytes (DMP1-Sost mice) reduced or abolished, respectively, the increased cortical bone area, periosteal bone formation rate, and expression of osteoblast markers and Wnt target genes exhibited by the DMP1-caPTHR1 mice. In addition, DMP1-caPTHR1 lacking LRP5 or double transgenic DMP1-caPTHR1;DMP1-Sost mice exhibit exacerbated intracortical remodeling and increased osteoclast numbers, and markedly decreased expression of the RANK decoy receptor osteoprotegerin. Thus, whereas Sost downregulation and the consequent Wnt activation is required for the stimulatory effect of PTH receptor signaling on periosteal bone formation, the Wnt-independent increase in osteoclastogenesis induced by PTH receptor activation in osteocytes overrides the effect on Sost. These findings demonstrate that PTH receptor signaling influences cortical bone through actions on osteocytes and defines the role of Wnt signaling in PTH receptor action.

Vulnerability of healthy vertebrae in patients with and without previous vertebral fracture

Vertebral deformities are associated with a marked increase in morbidity, mortality, and burden in terms of sanitary expenditures. Patients with vertebral fractures have a negative impact in their health, less quality of life, and loss of functional capacity and independence. The purpose of this study was to explore the vulnerability of healthy vertebrae in patients who have sustained already a compression fracture and in patients who do not have prevalent fractures in the thoracic spine; and to explore the association of the deformity in healthy vertebrae with different variables, such as bone mineral density (BMD), body mass index, age, loss of height, presence of clinical kyphosis, history of other osteoporotic fractures, and falls occurring during the last year. Clinical data and complementary studies from 175 postmenopausal outpatients were analyzed. These women (age: 69.7±11.1 years) had not received any treatment for osteoporosis. Anteroposterior and lateral radiographs of the thoracic spine and bone densitometry of the hip were obtained; morphometry was performed in 1575 thoracic vertebrae from T4 to T12. The angle of wedging of each vertebral body was calculated using a trigonometric formula. Then, the sum of wedge angles of vertebral bodies (SWA) was determined, and Cobb angle was measured. In patients with vertebral fractures, after excluding the angles of fractured vertebral bodies, the mean wedge angle of the remaining vertebrae (MWAhealthy) was calculated. The same procedure was followed in patients without vertebral fractures. MWAhealthy was considered as an indicator of the structural vulnerability of non-fractured vertebrae. Patients with prevalent fractures had lower BMD, wider Cobb angle, and higher sum of wedge angles than patients without vertebral fractures. The proportion of patients with accentuation of clinical kyphosis was higher in the group with prevalent vertebral fractures. A highly significant difference was found in the MWAhealthy, which was higher in patients with prevalent fractures (4.1±1.3° vs. 3.0±1.1°; p<0.001). Patients showing vertebral fractures had 7.1±4.2 cm height loss in average, significantly superior than that found among non-fractured women (3.6±3.2 cm; p<0.01). In multivariate analysis, the increase of MWAhealthy was associated with advancing age (p<0.02), lower femoral neck BMD (p<0.005), presence of clinical kyphosis (p<0.01) and vertebral fractures (p<0.02). This study presents evidence that a series of factors independently influence the increase in wedging deformity of vertebral bodies that are not fractured yet. These factors could contribute to an increased vulnerability of the vertebrae, making them more susceptible to fracture.

Determinants of the mechanical behavior of human lumbar vertebrae after simulated mild fracture

The ability of a vertebra to carry load after an initial deformation and the determinants of this postfracture load-bearing capacity are critical but poorly understood. This study aimed to determine the mechanical behavior of vertebrae after simulated mild fracture and to identify the determinants of this postfracture behavior. Twenty-one human L(3) vertebrae were analyzed for bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA) and for microarchitecture by micro-computed tomography (µCT). Mechanical testing was performed in two phases: initial compression of vertebra to 25% deformity, followed, after 30 minutes of relaxation, by a similar test to failure to determine postfracture behavior. We assessed (1) initial and postfracture mechanical parameters, (2) changes in mechanical parameters, (3) postfracture elastic behavior by recovery of vertebral height after relaxation, and (4) postfracture plastic behavior by residual strength and stiffness. Postfracture failure load and stiffness were 11% ± 19% and 53% ± 18% lower than initial values (p = .021 and p < .0001, respectively), with 29% to 69% of the variation in the postfracture mechanical behavior explained by the initial values. Both initial and postfracture mechanical behaviors were significantly correlated with bone mass and microarchitecture. Vertebral deformation recovery averaged 31% ± 7% and was associated with trabecular and cortical thickness (r = 0.47 and r = 0.64; p = .03 and p = .002, respectively). Residual strength and stiffness were independent of bone mass and initial mechanical behavior but were related to trabecular and cortical microarchitecture (|r| = 0.50 to 0.58; p = .02 to .006). In summary, we found marked variation in the postfracture load-bearing capacity following simulated mild vertebral fractures. Bone microarchitecture, but not bone mass, was associated with postfracture mechanical behavior of vertebrae.

Role of trabecular microarchitecture and its heterogeneity parameters in the mechanical behavior of ex vivo human L3 vertebrae

Low bone mineral density (BMD) is a strong risk factor for vertebral fracture risk in osteoporosis. However, many fractures occur in people with moderately decreased or normal BMD. Our aim was to assess the contributions of trabecular microarchitecture and its heterogeneity to the mechanical behavior of human lumbar vertebrae. Twenty-one human L(3) vertebrae were analyzed for BMD by dual-energy X-ray absorptiometry (DXA) and microarchitecture by high-resolution peripheral quantitative computed tomography (HR-pQCT) and then tested in axial compression. Microarchitecture heterogeneity was assessed using two vertically oriented virtual biopsies--one anterior (Ant) and one posterior (Post)--each divided into three zones (superior, middle, and inferior) and using the whole vertebral trabecular volume for the intraindividual distribution of trabecular separation (Tb.Sp*SD). Heterogeneity parameters were defined as (1) ratios of anterior to posterior microarchitectural parameters and (2) the coefficient of variation of microarchitectural parameters from the superior, middle, and inferior zones. BMD alone explained up to 44% of the variability in vertebral mechanical behavior, bone volume fraction (BV/TV) up to 53%, and trabecular architecture up to 66%. Importantly, bone mass (BMD or BV/TV) in combination with microarchitecture and its heterogeneity improved the prediction of vertebral mechanical behavior, together explaining up to 86% of the variability in vertebral failure load. In conclusion, our data indicate that regional variation of microarchitecture assessment expressed by heterogeneity parameters may enhance prediction of vertebral fracture risk.

Increase in vertebral body size in postmenopausal women with osteoporosis

Bone geometry plays a prominent role in bone strength. Cross-sectional studies have shown that advancing age is associated with increasing diameter of long bones, related to both periostal apposition and endosteal resorption. However, there are few data provided by prospective studies, especially concerning the changes in vertebral body dimensions. The objective of this prospective study was to measure the changes occurring in the vertebral body size of women with postmenopausal osteoporosis. Three-year data from placebo groups of the SOTI and TROPOS trials, performed in women with postmenopausal osteoporosis, were used for this study. In these trials, patients underwent lateral radiographs of the thoracic and lumbar spine at baseline and annually over 3 years, according to standardized procedures. Six-point digitization method was used: the four corner points of the vertebral body from T4 to L4 are marked, as well as an additional point in the middle of the upper and lower endplates. From these 6 points, the vertebral body perimeter, area and depth were measured at baseline and at 3 years. The analysis excluded all vertebrae with prevalent or incident fracture. A total of 2017 postmenopausal women (mean age 73.4+/-6.1 years) with a mean lumbar spine T score of -3.1+/-1.5, and a mean femoral neck T score of -3.0+/-0.7 are included in the analysis. Vertebral body dimensions increased over 3 years, by 2.1+/-5.5% (mean depth+/-SD), by 1.7+/-8.3% (mean area+/-SD) and by 1.5+/-4.9% (mean perimeter+/-SD) at the thoracic level (T4 to T12). At the lumbar level (L1 to L4), these dimensions increased as well: 1.4+/-3.6% (mean depth+/-SD), 1.4+/-5.7% (mean area+/-SD), 0.7+/-2.9% (mean perimeter+/-SD). A significant increase in vertebral body size was observed for each vertebral level from T5 to L4 for each of these parameters (p<0.01). These prospective results demonstrate that vertebral body dimensions increase over 3 years in women with postmenopausal osteoporosis.

Functional and association analysis of frizzled 1 (FZD1) promoter haplotypes with femoral neck geometry

Frizzleds are receptors for Wnt signaling and are involved in skeletal morphogenesis. Little is known about the transcriptional regulation of frizzleds in bone cells. In the current study, we determined if two common and potentially functional genetic variants (rs2232157, rs2232158) in the frizzled-1 (FZD1) promoter region and their haplotypes influence FZD1 promoter activity in human osteoblast-like cells. We also determined if these variants are associated with femoral neck bone mineral density (BMD) and geometry in 1319 African ancestry men aged > or =40 years. Real-time quantitative PCR and western blot analysis demonstrated FZD1 mRNA and protein expression in the human osteoblast-like cell lines, MG63 and SaOS-2. Promoter activity was next assessed by transient expression of haplotype specific FZD1 promoter reporter plasmids in these cells. In comparison to the common GG haplotype, promoter activity was 3-fold higher for the TC haplotype in both cell lines (p<0.05). We previously demonstrated that rs2232158 is associated with differential FZD1 promoter activity and Egr1 binding and thus focused further functional analyses on the rs2232157 G-to-T polymorphism. Electrophoretic mobility shift assay demonstrated that distinct nuclear protein complexes were associated with rs2232157 in an allele specific manner. Bioinformatics analysis predicted that the G to T transversion creates an E2F1 binding site, further supporting the functional significance of rs2232157 in FZD1 promoter regulation. Individual SNPs and haplotypes were not associated with femoral neck BMD. The TC haplotype was associated with larger subperiosteal width and greater CSMI (p<0.05). These results suggest that FZD1 expression is regulated in a haplotype-dependent manner in osteoblasts and that these same haplotypes may be associated with biomechanical indices of bone strength.