Epidemiology of forearm fractures in women and men in Norway 2008-2019

The purpose of this paper is to describe rates of forearm fractures in adults in Norway 2008-2019. Incidence rate of distal forearm fractures declined over time in both sexes. Forearm fracture constitute a significant health burden and prevention strategies are needed.

PURPOSE

To assess age- and sex-specific incidence rates, and time trends for forearm fractures in Norway, and compare these with incidence rates in other Nordic countries.

METHODS

Data on all patients aged 20-107 years with forearm fractures treated in Norwegian hospitals from 2008 to 2019 was retrieved from the Norwegian Patient Registry. Fractures were identified based on International Classification of Disease 10th revision code S52. Age- and sex-specific incidence rates and changes in incidence rates were calculated.

RESULTS

We identified 181,784 forearm fractures in 45,628,418 person-years. Mean annual forearm fracture incidence rates per 100,000 person-years were 398 (95% CI 390-407) for all, 565 (95% CI 550-580) for women, and 231 (95% CI 228-234) for men above 20 years. Mean annual number of forearm fractures was 15,148 (95% CI 14,575-15,722). From 2008 to 2019, age-adjusted total incidence rates of forearm fractures S52 diagnoses declined by 3.5% (incidence rate ratio (IRR) of 0.997 (95% CI 0.994-0.999)) in men. The corresponding decline in women was not significant (IRR: 0.999 (95% CI 0.997-1.002)). In the same period, the age-adjusted incidence rates of distal forearm fractures declined by 7.0% in men (IRR = 0.930; 95% CI 0.886-0.965) and 4.7% in women (IRR = 0.953; 95% CI 0.919-0.976). The incidence rates of distal forearm fractures were similar to rates in Sweden and Finland.

CONCLUSION

Age-adjusted incidence rates of distal forearm fractures in both sexes declined over time.

A perspective on muscle phenotyping in musculoskeletal research

Musculoskeletal research should synergistically investigate bone and muscle to inform approaches for maintaining mobility and to avoid bone fractures. The relationship between sarcopenia and osteoporosis, integrated in the term 'osteosarcopenia', is underscored by the close association shown between these two conditions in many studies, whereby one entity emerges as a predictor of the other. In a recent workshop of Working Group (WG) 2 of the EU Cooperation in Science and Technology (COST) Action 'Genomics of MusculoSkeletal traits Translational Network' (GEMSTONE) consortium (CA18139), muscle characterization was highlighted as being important, but currently under-recognized in the musculoskeletal field. Here, we summarize the opinions of the Consortium and research questions around translational and clinical musculoskeletal research, discussing muscle phenotyping in human experimental research and in two animal models: zebrafish and mouse.

Forearm fractures - are we counting them all? An attempt to identify and include the missing fractures treated in primary care

OBJECTIVE

Norway has a high incidence of forearm fractures, however, the incidence rates based on secondary care registers can be underestimated, as some fractures are treated exclusively in primary care. We estimated the proportion of forearm fracture diagnoses registered exclusively in primary care and assessed the agreement between diagnosis for forearm fractures in primary and secondary care.

DESIGN

Quality assurance study combining nationwide data from 2008 to 2019 on forearm fractures registered in primary care (Norwegian Control and Payment of Health Reimbursement) and secondary care (the Norwegian Patient Registry).

SETTING AND PATIENTS

Forearm fracture diagnoses in patients aged ≥20 treated in primary care (n = 83,357) were combined with injury diagnoses for in- and outpatients in secondary care (n = 3,294,336).

MAIN OUTCOME MEASURES

Proportion of forearm fractures registered exclusively in primary care, and corresponding injury diagnoses for those registered in both primary and secondary care.

RESULTS

Of 189,105 forearm fracture registrations in primary and secondary care, 13,948 (7.4%) were registered exclusively in primary care. The proportion ranged from 4.9% to 13.5% on average between counties, but was higher in some municipalities (>30%). Of 66,747 primary care forearm fractures registered with a diagnosis in secondary care, 62% were incident forearm fractures, 28% follow-up controls, and 10% other fractures or non-fracture injuries.

CONCLUSION

An overall small proportion of forearm fractures were registered only in primary care, but it was larger in some areas of Norway. Failing to include fractures exclusively treated in primary care could underestimate the incidence rates in these areas.

Validation of forearm fracture diagnoses in administrative patient registers

The validity of forearm fracture diagnoses recorded in five Norwegian hospitals was investigated using image reports and medical records as gold standard. A relatively high completeness and correctness of the diagnoses was found. Algorithms used to define forearm fractures in administrative data should depend on study purpose.

PURPOSE

In Norway, forearm fractures are routinely recorded in the Norwegian Patient Registry (NPR). However, these data have not been validated. Data from patient administrative systems (PAS) at hospitals are sent unabridged to NPR. By using data from PAS, we aimed to examine (1) the validity of the forearm fracture diagnoses and (2) the usefulness of washout periods, follow-up codes, and procedure codes to define incident forearm fracture cases.

METHODS

This hospital-based validation study included women and men aged ≥ 19 years referred to five hospitals for treatment of a forearm fracture during selected periods in 2015. Administrative data for the ICD-10 forearm fracture code S52 (with all subgroups) in PAS and the medical records were reviewed. X-ray and computed tomography (CT) reports from examinations of forearms were reviewed independently and linked to the data from PAS. Sensitivity and positive predictive values (PPVs) were calculated using image reports and/or review of medical records as gold standard.

RESULTS

Among the 8482 reviewed image reports and medical records, 624 patients were identified with an incident forearm fracture during the study period. The sensitivity of PAS registrations was 90.4% (95% CI: 87.8-92.6). The PPV increased from 73.9% (95% CI: 70.6-77.0) in crude data to 90.5% (95% CI: 88.0-92.7) when using a washout period of 6 months. Using procedure codes and follow-up codes in addition to 6-months washout increased the PPV to 94.0%, but the sensitivity fell to 69.0%.

CONCLUSION

A relatively high sensitivity of forearm fracture diagnoses was found in PAS. PPV varied depending on the algorithms used to define cases. Choice of algorithm should therefore depend on study purposes. The results give useful measures of forearm fracture diagnoses from administrative patient registers. Depending on local coding practices and treatment pathways, we infer that the findings are relevant to other fracture diagnoses and registers.

Is There a Causal Relationship between Physical Activity and Bone Microarchitecture? A Study of Adult Female Twin Pairs

The reasons for the association between physical activity (PA) and bone microarchitecture traits are unclear. We examined whether these associations were consistent with causation and/or with shared familial factors using a cross-sectional study of 47 dizygotic and 93 monozygotic female twin pairs aged 31-77 years. Images of the nondominant distal tibia were obtained using high-resolutionperipheral quantitative computed tomography. The bone microarchitecture was assessed using StrAx1.0 software. Based on a self-completed questionnaire, a PA index was calculated as a weighted sum of weekly hours of light (walking, light gardening), moderate (social tennis, golf, hiking), and vigorous activity (competitive active sports) = light + 2 * moderate + 3 * vigorous. We applied Inference about Causation through Examination of FAmiliaL CONfounding (ICE FALCON) to test whether cross-pair cross-trait associations changed after adjustment for within-individual associations. Within-individual distal tibia cortical cross-sectional area (CSA) and cortical thickness were positively associated with PA (regression coefficients [β] = 0.20 and 0.22), while the porosity of the inner transitional zone was negatively associated with PA (β = -0.17), all p < 0.05. Trabecular volumetric bone mineral density (vBMD) and trabecular thickness were positively associated with PA (β = 0.13 and 0.14), and medullary CSA was negatively associated with PA (β = -0.22), all p ≤ 0.01. Cross-pair cross-trait associations of cortical thickness, cortical CSA, and medullary CSA with PA attenuated after adjustment for the within-individual association (p = 0.048, p = 0.062, and p = 0.028 for changes). In conclusion, increasing PA was associated with thicker cortices, larger cortical area, lower porosity of the inner transitional zone, thicker trabeculae, and smaller medullary cavities. The attenuation of cross-pair cross-trait associations after accounting for the within-individual associations was consistent with PA having a causal effect on the improved cortical and trabecular microarchitecture of adult females, in addition to shared familial factors. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Target Values and Daytime Variation of Bone Turnover Markers in Monitoring Osteoporosis Treatment after Fractures

The serum bone turnover markers (BTM) procollagen type 1 N‐terminal propeptide (P1NP) and C‐terminal cross‐linking telopeptide of type 1 collagen (CTX) are recommended for monitoring adherence and response of antiresorptive drugs (ARD). BTM are elevated about 1 year after fracture and therefore BTM target values are most convenient in ARD treatment follow‐up of fracture patients. In this prospective cohort study, we explored the cut‐off values of P1NP and CTX showing the best discriminating ability with respect to adherence and treatment effects, reflected in bone mineral density (BMD) changes. Furthermore, we explored the ability of BTM to predict subsequent fractures and BTM variation during daytime in patients using ARD or not. After a fragility fracture, 228 consenting patients (82.2% women) were evaluated for ARD indication and followed for a mean of 4.6 years (SD 0.5 years). BMD was measured at baseline and after 2 years. Serum BTM were measured after 1 or 2 years. The largest area under the curve (AUC) for discrimination of patients taking ARD or not was shown for P1NP <30 μg/L and CTX <0.25 μg/L. AUC for discrimination of patients with >2% gain in BMD (lumbar spine and total hip) was largest at cut‐off values for P1NP <30 μg/L and CTX <0.25 μg/L. Higher P1NP was associated with increased fracture risk in patients using ARD (hazard ratio [HR]_logP1NP = 15.0; 95% confidence interval [CI] 2.7–83.3), p = 0.002. P1NP and CTX were stable during daytime, except in those patients not taking ARD, where CTX decreased by 21% per hour during daytime. In conclusion, P1NP <30 μg/L and CTX <0.25 μg/L yield the best discrimination between patients taking and not taking ARD and the best prediction of BMD gains after 2 years. Furthermore, higher P1NP is associated with increased fracture risk in patients on ARD. BTM can be measured at any time during the day in patients on ARD. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Cortical bone structure of the proximal femur and incident fractures

PURPOSE

Fracture risk is most frequently assessed using Dual X-ray absorptiometry to measure areal bone mineral density (aBMD) and using the Fracture Risk Assessment Tool (FRAX). However, these approaches have limitations and additional bone measurements may enhance the predictive ability of these existing tools. Increased cortical porosity has been associated with incident fracture in some studies, but not in others. In this prospective study, we examined whether cortical bone structure of the proximal femur predicts incident fractures independent of aBMD and FRAX score.

METHODS

We pooled 211 postmenopausal women with fractures aged 54-94 years at baseline and 232 fracture-free age-matched controls based on a prior nested case-control study from the Tromsø Study in Norway. We assessed baseline femoral neck (FN) aBMD, calculated FRAX 10-year probability of major osteoporotic fracture (MOF), and quantified femoral subtrochanteric cortical parameters: porosity, area, thickness, and volumetric BMD (vBMD) from CT images using the StrAx1.0 software. Associations between bone parameters and any incident fracture, MOF and hip fracture were determined using Cox's proportional hazard models to calculate hazard ratio (HR) with 95% confidence interval.

RESULTS

During a median follow-up of 7.2 years, 114 (25.7%) of 443 women suffered one or more incident fracture. Cortical bone structure did not predict any incident fracture or MOF after adjustment for age, BMI, and previous fracture. Each SD higher total cortical porosity, thinner cortices, and lower cortical vBMD predicted hip fracture with increased risk of 46-62% (HRs ranging from 1.46 (1.01-2.11) to 1.62 (1.02-2.57)). After adjustment for FN aBMD or FRAX score no association remained significant. Both lower FN aBMD and higher FRAX score predicted any incident fracture, MOF and hip fractures with HRs ranging from 1.45-2.56.

CONCLUSIONS

This study showed that cortical bone measurements using clinical CT did not add substantial insight into fracture risk beyond FN aBMD and FRAX. We infer from these results that fracture risk related to the deteriorated bone structure seems to be largely captured by a measurement of FN aBMD and the FRAX tool.

Bone Phenotyping Approaches in Human, Mice and Zebrafish - Expert Overview of the EU Cost Action GEMSTONE ("GEnomics of MusculoSkeletal traits TranslatiOnal NEtwork")

A synoptic overview of scientific methods applied in bone and associated research fields across species has yet to be published. Experts from the EU Cost Action GEMSTONE ("GEnomics of MusculoSkeletal Traits translational Network") Working Group 2 present an overview of the routine techniques as well as clinical and research approaches employed to characterize bone phenotypes in humans and selected animal models (mice and zebrafish) of health and disease. The goal is consolidation of knowledge and a map for future research. This expert paper provides a comprehensive overview of state-of-the-art technologies to investigate bone properties in humans and animals - including their strengths and weaknesses. New research methodologies are outlined and future strategies are discussed to combine phenotypic with rapidly developing -omics data in order to advance musculoskeletal research and move towards "personalised medicine".

Estimated Glomerular Filtration Rate (eGFR) based on cystatin C was associated with increased risk of hip and proximal humerus fractures in women and decreased risk of hip fracture in men, whereas eGFR based on creatinine was not associated with fracture risk in both sexes: The Tromsø Study

PURPOSE

Patients with end-stage kidney disease have an increased fracture risk. Whether mild to moderate reductions in kidney function is associated with increased fracture risk is uncertain. Results from previous studies may be confounded by muscle mass because of the use of creatinine-based estimates of the glomerular filtration rate (eGFRcre). We tested the hypothesis that lower eGFR within the normal range of kidney function based on serum cystatin C (eGFRcys) or both cystatin C and creatinine (eGFRcrecys) predict fractures better than eGFR based on creatinine (eGFRcre).

METHODS

In the Tromsø Study 1994-95, a cohort of 3016 women and 2836 men aged 50-84 years had eGFRcre, eGFRcys and eGFRcrecys estimated using the Chronic Kidney Disease Epidemiology Collaboration equations. Hazard ratios (HRs) (95% confidence intervals) for fracture were calculated in Cox's proportional hazards models and adjusted for age, height, body mass index, bone mineral density, diastolic blood pressure, smoking, physical activity, previous fracture, diabetes and cardiovascular disease.

RESULTS

During a median of 14.6 years follow-up, 232, 135 and 394 women and 118, 35 and 65 men suffered incident hip, proximal humerus and wrist fractures. In women, lower eGFRcre did not predict fracture, but the risk for hip and proximal humerus fracture increased per standard deviation (SD) lower eGFRcys (HRs 1.36 (1.16-1.60) and 1.33 (1.08-1.63)) and per SD lower eGFRcrecys (HRs 1.25 (1.08-1.45) and 1.30 (1.07-1.57)). In men, none of the eGFR estimates were related to increased fracture risk. In contrast, eGFRcys and eGFRcrecys were inversely associated with hip fracture risk (HRs 0.85 (0.73-0.99) and 0.82 (0.68-0.98)).

CONCLUSIONS

In women, each SD lower eGFRcys and eGFRcrecys increased the risk of hip and proximal humerus fracture by 25-36%, whereas eGFRcre did not. In men, none of the estimates of eGFR were related to increased fracture risk, and each SD lower eGFRcys and eGFRcrecys decreased the risk of hip fracture by 15-18%. The findings particularly apply to a cohort of generally healthy individuals with a normal kidney function. In future studies, the association of measured GFR using the gold standard method of iohexol clearance with fractures risk should be examined for causal inference. More clinical research is needed before robust clinical inferences can be made.

Are the Relationships of Lean Mass and Fat Mass With Bone Microarchitecture Causal or Due to Familial Confounders? A Novel Study of Adult Female Twin Pairs

It is not known whether the relationships of lean mass (LM) and fat mass (FM) with bone microarchitecture and geometry are causal and/or are because of confounders, including familial confounders arising from genetic and environment effects shared by relatives. We tested the hypotheses that: (i) LM is associated with cortical bone traits, (ii) FM is associated with trabecular bone traits, and (iii) these relationships of LM and FM with bone microarchitecture and geometry have a causal component. Total body composition was quantified for 98 monozygotic (MZ) and 54 dizygotic (DZ) white female twin pairs aged 31 to 77 years. Microarchitecture at the distal tibia and distal radius was quantified using HRpQCT and StrAx software. We applied the Inference about Causation through Examination of FAmiliaL CONfounding (ICE FALCON) method. Within‐individuals, distal tibia total bone area, cortical area, cortical thickness, and trabecular number were positively associated with LM (standardized regression coefficient (β) = 0.13 to 0.43; all p < 0.05); porosity of the inner transitional zone (ITZ) was negatively associated with LM (β = −0.22; p < 0.01). Trabecular number was positively associated with FM (β = 0.40; p < 0.001), and trabecular thickness was negatively associated with FM (β = −0.27; p < 0.001). For porosity of ITZ and trabecular number, the cross‐pair cross‐trait association with LM was significant before and after adjustment for the within‐individual association with LM (all ps < 0.05). For trabecular number, the cross‐pair cross‐trait association with FM was significant before and after adjustment for the within‐individual association with FM (p < 0.01). There were no significant changes in these cross‐pair cross‐trait associations after adjustment for the within‐individual association (p = 0.06 to 0.99). Similar results were found for distal radius measures. We conclude that there was no evidence that the relationships of LM and FM with bone microarchitecture and geometry are causal; they must in part due to by familial confounders affecting both bone architecture and body composition. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Determinants of trabecular bone score and prevalent vertebral fractures in women with fragility fractures: a cross-sectional sub-study of NoFRACT

Determinants of trabecular bone score (TBS) and vertebral fractures assessed semiquantitatively (SQ1-SQ3) were studied in 496 women with fragility fractures. TBS was associated with age, parental hip fracture, alcohol intake and BMD, not SQ1-SQ3 fractures. SQ1-SQ3 fractures were associated with age, prior fractures, and lumbar spine BMD, but not TBS.

INTRODUCTION

Trabecular bone score (TBS) and vertebral fractures assessed by semiquantitative method (SQ1-SQ3) seem to reflect different aspects of bone strength. We therefore sought to explore the determinants of and the associations between TBS and SQ1-SQ3 fractures.

METHODS

This cross-sectional sub-study of the Norwegian Capture the Fracture Initiative included 496 women aged ≥ 50 years with fragility fractures. All responded to a questionnaire about risk factors for fracture, had bone mineral density (BMD) of femoral neck and/or lumbar spine assessed, TBS calculated, and 423 had SQ1-SQ3 fracture assessed.

RESULTS

Mean (SD) age was 65.6 years (8.6), mean TBS 1.27 (0.10), and 33.3% exhibited SQ1-SQ3 fractures. In multiple variable analysis, higher age (β_{per SD} = - 0.26, 95% CI: - 0.36,- 0.15), parental hip fracture (β = - 0.29, 95% CI: - 0.54,- 0.05), and daily alcohol intake (β = - 0.43, 95% CI - 0.79, - 0.08) were associated with lower TBS. Higher BMD of femoral neck (β_{per SD} = 0.34, 95% CI 0.25-0.43) and lumbar spine (β_{per SD} = 0.40, 95% CI 0.31-0.48) were associated with higher TBS. In multivariable logistic regression analyses, age (OR_{per SD} = 1.94, 95% CI 1.51-2.46) and prior fragility fractures (OR = 1.71, 95% CI 1.09-2.71) were positively associated with SQ1-SQ3 fractures, while lumbar spine BMD (OR_{per SD} = 0.75 95% CI 0.60-0.95) was negatively associated with SQ1-SQ3 fractures. No association between TBS and SQ1-SQ3 fractures was found.

CONCLUSION

Since TBS and SQ1-SQ3 fractures were not associated, they may act as independent risk factors, justifying the use of both in post-fracture risk assessment.

Grip strength in men and women aged 50-79 years is associated with non-vertebral osteoporotic fracture during 15 years follow-up: The Tromsø Study 1994-1995

In 50-79-year-olds who participated in the Tromsø Study (1994-1995), the risk of non-vertebral osteoporotic fractures during 15 years follow-up increased by 22% in men and 9% in women per 1 SD lower grip strength. The strongest association was observed in men aged 50-64 years.

INTRODUCTION

We aimed to explore whether low grip strength was associated with increased risk of non-vertebral osteoporotic fracture in the population-based Tromsø Study 1994-1995.

METHODS

Grip strength (bar) was measured by a Martin Vigorimeter and fractures were retrieved from the X-ray archives at the University Hospital of North Norway between 1994 and 2010. At baseline, weight and height were measured, whereas information on the other covariates were obtained through self-reported questionnaires. Cox regression was used to estimate the hazard ratio (HR) of fracture in age- and gender-specific quintiles of grip-strength, and per 1 SD lower grip strength. Similar analyses were done solely for hip fractures. Adjustments were made for age, height, body mass index (BMI), marital status, education, smoking, physical activity, use of alcohol, self-perceived health, and self-reported diseases.

RESULTS

In 2891 men and 4002 women aged 50-79 years, 1099 non-vertebral osteoporotic fractures-including 393 hip fractures-were sustained during the median 15 years follow-up. Risk of non-vertebral osteoporotic fracture increased with declining grip strength: hazard ratios per SD decline was 1.22 (95% CI 1.05-1.43) in men and 1.09 (95% CI 1.01-1.18) in women. HR for fracture in lower vs. upper quintile was 1.58 (95% CI 1.02-2.45) in men and 1.28 (95% CI 1.03-1.59) in women. The association was most pronounced in men aged 50-64 years with HR = 3.39 (95% CI 1.76-6.53) in the lower compared to the upper quintile.

CONCLUSIONS

The risk of non-vertebral osteoporotic fracture increased with declining grip-strength in both genders, particularly in men aged 50-64 years.

Prevalence of gestational diabetes and pregnancy outcomes in Nordland and Troms counties 2004–15

BACKGROUND

The aim was to investigate the prevalence of gestational diabetes and pregnancy outcomes in women with gestational diabetes in Nordland and Troms counties.

MATERIAL AND METHOD

We included all 1 067 women with type 1 diabetes, type 2 diabetes and gestational diabetes among 34 915 births at four hospitals in Nordland and Troms counties from 2004 to 2015. Prevalence of diabetes was calculated based on ICD-10 codes in patient records for women with diabetes in Nordland and Troms counties, and compared with national prevalence figures from the Medical Birth Registry of Norway. Prevalence of pre-eclampsia, macrosomia (birth weight > 4 500 grams) and caesarian section was calculated for all women with diabetes and all those giving birth in the same region.

RESULTS

Prevalence of type 1 diabetes and type 2 diabetes remained stable. Prevalence of gestational diabetes increased from 1.0 % to 4.0 % in Nordland and Troms counties and from 1.0 % to 3.8 % nationally. Prevalence of pre-eclampsia among all women with diabetes fell from 18.8 % in 2004-06 to 12.4 % in 2013-15. In women with diabetes, the prevalence of pre-eclampsia was 4.6 times higher, that of macrosomia was 3.5 times higher, and the proportion of caesarian sections was 2.3 times higher than in the background population.

INTERPRETATION

Prevalence of gestational diabetes increased in Nordland and Troms counties, as it did nationally. Prevalence of pre-eclampsia among pregnant women with diabetes fell, but prevalence of pre-eclampsia, macrosomia and caesarean section was higher than in the background population.

Post-fracture Risk Assessment: Target the Centrally Sited Fractures First! A Substudy of NoFRACT

The location of osteoporotic fragility fractures adds crucial information to post-fracture risk estimation. Triaging patients according to fracture site for secondary fracture prevention can therefore be of interest to prioritize patients considering the high imminent fracture risk. The objectives of this cross-sectional study were therefore to explore potential differences between central (vertebral, hip, proximal humerus, pelvis) and peripheral (forearm, ankle, other) fractures. This substudy of the Norwegian Capture the Fracture Initiative (NoFRACT) included 495 women and 119 men ≥50 years with fragility fractures. They had bone mineral density (BMD) of the femoral neck, total hip, and lumbar spine assessed using dual-energy X-ray absorptiometry (DXA), trabecular bone score (TBS) calculated, concomitantly vertebral fracture assessment (VFA) with semiquantitative grading of vertebral fractures (SQ1-SQ3), and a questionnaire concerning risk factors for fractures was answered. Patients with central fractures exhibited lower BMD of the femoral neck (765 versus 827 mg/cm² ), total hip (800 versus 876 mg/cm² ), and lumbar spine (1024 versus 1062 mg/cm² ); lower mean TBS (1.24 versus 1.28); and a higher proportion of SQ1-SQ3 fractures (52.0% versus 27.7%), SQ2-SQ3 fractures (36.8% versus 13.4%), and SQ3 fractures (21.5% versus 2.2%) than patients with peripheral fractures (all p < 0.05). All analyses were adjusted for sex, age, and body mass index (BMI); and the analyses of TBS and SQ1-SQ3 fracture prevalence was additionally adjusted for BMD). In conclusion, patients with central fragility fractures revealed lower femoral neck BMD, lower TBS, and higher prevalence of vertebral fractures on VFA than the patients with peripheral fractures. This suggests that patients with central fragility fractures exhibit more severe deterioration of bone structure, translating into a higher risk of subsequent fragility fractures and therefore they should get the highest priority in secondary fracture prevention, although attention to peripheral fractures should still not be diminished. © 2019 American Society for Bone and Mineral Research. © 2019 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research.

The effect of maternal and paternal height and weight on antenatal, perinatal and postnatal morphology in sex-stratified analyses

INTRODUCTION

Low birthweight is associated with diseases later in life. The mechanisms for these associations are not well known. If the hypothesis concerning "maternal constraint" is correct for humans, as shown in animal experiments, we expect the maternal, not paternal, body proportions to influence antenatal growth and those of both parents to influence postnatal growth. We aimed to study the effect of maternal and paternal height and weight on fetal femur length antenatally (gestational weeks 20 and 30) and body length and weight at birth and postnatally (12 and 24 months old) in both sexes.

MATERIAL AND METHODS

In this prospective cohort study, 399 healthy pregnant women aged 20-42 years were recruited at The Mercy Hospital for Woman, Melbourne, Australia from 2008 to 2009. Fetal femur length was measured using antenatal ultrasound (gestational weeks 20 and 30). Body length and weight were measured for parents and offspring at birth and postnatally (12 and 24 months).

RESULTS

Each standard deviation (SD) rise in maternal weight (15.5 kg) was associated with 0.24 SD (0.5 mm) and 0.18 SD (0.4 mm) longer femur length in female and male fetuses at week 20 and 0.17 SD (0.5 mm) and 0.38 SD (1.1 mm) longer femur length in female and male fetuses at week 30, respectively. In girls, each SD rise in paternal height (7.2 cm) was associated with 0.29 SD (0.6 cm) longer birth length. In boys, each SD rise in maternal height (6.7 cm) was associated with 0.23 SD (0.5 cm) longer birth length. In both sexes, parental height and weight were associated with offspring length and weight at 12 and 24 months (SD ranging from 0.20 to 0.38, length from 0.7 to 1.5 cm and weight from 0.3 to 0.6 kg). The multivariable linear regression analyses were adjusted for parental age, height and weight, maternal smoking, alcohol intake, parity, and ethnicity, all P < 0.05.

CONCLUSIONS

Maternal, not paternal, body proportions determined fetal growth in both sexes. Paternal height predicted birth length in girls. In contrast, maternal height predicted birth length in boys. Both parents predicted postnatal body proportions at 12 and 24 months in both sexes.

Adding Marrow Adiposity and Cortical Porosity to Femoral Neck Areal Bone Mineral Density Improves the Discrimination of Women With Nonvertebral Fractures From Controls

Advancing age is accompanied by a reduction in bone formation and remodeling imbalance, which produces microstructural deterioration. This may be partly caused by a diversion of mesenchymal cells towards adipocytes rather than osteoblast lineage cells. We hypothesized that microstructural deterioration would be associated with an increased marrow adiposity, and each of these traits would be independently associated with nonvertebral fractures and improve discrimination of women with fractures from controls over that achieved by femoral neck (FN) areal bone mineral density (aBMD) alone. The marrow adiposity and bone microstructure were quantified from HR-pQCT images of the distal tibia and distal radius in 77 women aged 40 to 70 years with a recent nonvertebral fracture and 226 controls in Melbourne, Australia. Marrow fat measurement from HR-pQCT images was validated using direct histologic measurement as the gold standard, at the distal radius of 15 sheep, with an agreement (R² = 0.86, p < 0.0001). Each SD higher distal tibia marrow adiposity was associated with 0.33 SD higher cortical porosity, and 0.60 SD fewer, 0.24 SD thinner, and 0.72 SD more-separated trabeculae (all p < 0.05). Adjusted for age and FN aBMD, odds ratios (ORs) (95% CI) for fracture per SD higher marrow adiposity and cortical porosity were OR, 3.39 (95% CI, 2.14 to 5.38) and OR, 1.79 (95% CI, 1.14 to 2.80), respectively. Discrimination of women with fracture from controls improved when cortical porosity was added to FN aBMD and age (area under the receiver-operating characteristic curve [AUC] 0.778 versus 0.751, p = 0.006) or marrow adiposity was added to FN aBMD and age (AUC 0.825 versus 0.751, p = 0.002). The model including FN aBMD, age, cortical porosity, trabecular thickness, and marrow adiposity had an AUC = 0.888. Results were similar for the distal radius. Whether marrow adiposity and cortical porosity indices improve the identification of women at risk for fractures requires validation in prospective studies. © 2019 American Society for Bone and Mineral Research.

High prevalence of vertebral fractures and low trabecular bone score in patients with fragility fractures: A cross-sectional sub-study of NoFRACT

PURPOSE

Norway has among the highest incidence rates of fractures in the world. Vertebral fracture assessment (VFA) and trabecular bone score (TBS) provide information about fracture risk, but their importance have not been studied in Norwegian patients with fragility fractures. The objectives of this study were to examine the clinical characteristics of a cohort of women and men with fragility fractures, their prevalence of vertebral fractures using VFA and prevalence of low TBS, and explore the differences between the sexes and patients with and without vertebral fractures.

METHODS

This cross-sectional sub-study of the Norwegian Capture the Fracture Initiative (NoFRACT) included 839 patients with fragility fractures. Of these, 804 patients had bone mineral density (BMD) of the total hip, femoral neck and/or spine assessed using dual energy x-ray absorptiometry, 679 underwent concomitant VFA, 771 had TBS calculated and 696 responded to a questionnaire.

RESULTS

Mean age was 65.8 (SD 8.8) years and 80.5% were women. VFA revealed vertebral fractures in 34.8% of the patients and 34.0% had low TBS (≤ 1.23), with no differences between the sexes. In all patients with valid measures of both VFA and TBS, 53.8% had either vertebral fractures, low TBS, or both. In the patients with osteopenia at the femoral neck, 53.6% had either vertebral fractures, low TBS, or both. Femoral neck BMD T-score ≤ -2.5 was found in 13.8% of all patients, whereas the corresponding figure was 27.4% using the skeletal site with lowest T-score. Women exhibited lower BMD at all sites and lower TBS than men (1.27 vs. 1.29), (all p < 0.05). Patients with prevalent vertebral fractures were older (69.4 vs. 64.0 years), exhibited lower BMD at all sites and lower TBS (1.25 vs.1.29) than those without vertebral fractures (all p < 0.05). Before assessment, 8.2% were taking anti-osteoporotic drugs (AOD), and after assessment, the prescription rate increased to 56.2%.

CONCLUSIONS

More than half of the patients with fragility fractures had vertebral fractures, low TBS or both. The prescription of AOD increased seven fold from before assessment to after assessment, emphasizing the importance of risk assessment after a fragility fracture.

Effect of a Fracture Liaison Service on the Rate of Subsequent Fracture Among Patients With a Fragility Fracture in the Norwegian Capture the Fracture Initiative (NoFRACT): A Trial Protocol

IMPORTANCE

Fragility fracture is a major health issue because of the accompanying morbidity, mortality, and financial cost. Despite the high cost to society and personal cost to affected individuals, secondary fracture prevention is suboptimal in Norway, mainly because most patients with osteoporotic fractures do not receive treatment with antiosteoporotic drugs after fracture repair.

OBJECTIVES

To improve secondary fracture prevention by introducing a standardized intervention program and to investigate the effect of the program on the rate of subsequent fractures.

DESIGN, SETTING, AND PARTICIPANTS

Trial protocol of the Norwegian Capture the Fracture Initiative (NoFRACT), an ongoing, stepped wedge cluster randomized clinical trial in 7 hospitals in Norway. The participating hospitals were cluster randomized to an intervention starting date: May 1, 2015; September 1, 2015; and January 1, 2016. Follow-up is through December 31, 2019. The outcome data were merged from national registries of women and men 50 years and older with a recent fragility fracture treated at 1 of the 7 hospitals.

DISCUSSION

The NoFRACT trial is intended to enroll 82 000 patients (intervention period, 26 000 patients; control period, 56 000 patients), of whom 23 578 are currently enrolled by January 2018. Interventions include a standardized program for identification, assessment, and treatment of osteoporosis in patients with a fragility fracture that is led by a trained coordinating nurse. The primary outcome is rate of subsequent fracture (per 10 000 person-years) based on national registry data. Outcomes before (2008-2015; control period) and after (2015-2019; intervention period) the intervention will be compared, and each hospital will act as its own control. Use of outcomes from national registry data means that all patients are included in the analysis regardless of whether they are exposed to the intervention (intention to treat). A sensitivity analysis with a transition window will be performed to mitigate possible within-cluster contamination.

RESULTS

Results are planned to be disseminated through publications in peer-reviewed journals and presented at local, national, and international conferences.

CONCLUSIONS

By introducing a standardized intervention program for assessment and treatment of osteoporosis in patients with fragility fractures, we expect to document reduced rates of subsequent fractures and fracture-related mortality.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02536898.

Women with fracture, unidentified by FRAX, but identified by cortical porosity, have a set of characteristics that contribute to their increased fracture risk beyond high FRAX score and high cortical porosity

The Fracture Risk Assessment Tool (FRAX) is widely used to identify individuals at increased risk for fracture. However, cortical porosity is associated with risk for fracture independent of FRAX and is reported to improve the net reclassification of fracture cases. We wanted to test the hypothesis that women with fracture who are unidentified by high FRAX score, but identified by high cortical porosity, have a set of characteristics that contribute to their fracture risk beyond high FRAX score and high cortical porosity. We quantified FRAX score with femoral neck areal bone mineral density (FN aBMD), and femoral subtrochanteric architecture, in 211 postmenopausal women aged 54-94 years with non-vertebral fractures, and 232 fracture-free controls in Tromsø, Norway, using StrAx software. Of 211 fracture cases, FRAX score > 20% identified 53 women (sensitivity 25.1% and specificity 93.5%), while cortical porosity cut-off > 80th percentile identified 61 women (sensitivity 28.9% and specificity 87.9%). The 43 (20.4%) additional fracture cases identified by high cortical porosity alone, had lower FRAX score (12.3 vs. 26.2%) than those identified by FRAX alone, they were younger, had higher FN aBMD (806 vs. 738 mg/cm²), and fewer had a prior fracture (23.3 vs. 62.9%), all p < 0.05. They had higher cortical porosity (48.7 vs. 42.1%), thinner cortices (3.75 vs. 4.12 mm), lower cortical and total volumetric BMD (942 vs. 1053 and 586 vs. 699 mg HA/cm³), larger medullary and total cross-sectional areas (245 vs. 190 and 669 vs. 593 mm²), and higher cross-sectional moment of inertia (2619 vs. 2388 cm⁴) all p < 0.001. When the fracture cases and controls with high cortical porosity were compared, cases had higher cortical porosity, lower cortical vBMD, lower total vBMD, smaller cortical CSA/Total CSA, larger medullary CSA and larger total CSA than controls (all p ≤ 0.05). Thus, fracture cases, unidentified by FRAX, but identified by cortical porosity, had an architecture where the positive impact of larger bone size did not offset the negative effect of thinner cortices with increased porosity. A measurement of cortical porosity may be a marker of other characteristics that capture additional fracture risk components, not captured by FRAX.

Bone trait ranking in the population is not established during antenatal growth but is robustly established in the first postnatal year

Efforts to understand the pathophysiology of bone fragility must focus on bone traits during growth. We hypothesized that variance in individual trait ranking in the population distribution is established by genetic factors and is reflected in foetal trait ranking in early pregnancy, but intrauterine factors modify trait ranking in late pregnancy, followed by the reinstating of this ranking during the first postnatal year. Thus, relations with paternal factors are present in early pregnancy but are then lost and subsequently reinstated postnatal. We recruited 399 healthy pregnant women aged 20–42 years from The Mercy Hospital for Woman in Melbourne, Australia. Foetal femur length (FL) and knee-heel length (KHL) were measured by ultrasound during gestation, and FL, KHL, body length and weight were measured in neonates, infants, and parents. The z-scores were calculated using Royston models. Pearson correlation was used to assess tracking and linear mixed models to test the associations. Correlations between FL and KHL z-scores of the same trait at 20 and 30 weeks gestation, at birth, and at 12 and 24 months of age (r = 0.1–0.3) and of body length and weight at birth, and 6, 12 and 24 months (r = 0.3–0.5) became more robust after 6–12 months (r = 0.4–0.8). FL and KHL z-scores at 20 weeks gestation accounted for 4–5% of total variance, while FL, KHL, body length and weight z-scores at birth accounted for 13–26% of total variance in the same traits at 24 months. Maternal FL and KHL were associated with foetal FL and KHL at 20 and 30 weeks, but there were no such associations for paternal FL and KHL with foetal traits during gestation. Both maternal and paternal traits were associated with infant traits. Tracking in traits is not established antenatal but is robustly established at 6–12 months of age.

Menopause-Related Appendicular Bone Loss is Mainly Cortical and Results in Increased Cortical Porosity

After menopause, remodeling becomes unbalanced and rapid. Each of the many remodeling transactions deposits less bone than it resorbed, producing microstructural deterioration. Trabecular bone is said to be lost more rapidly than cortical bone. However, because 80% of the skeleton is cortical, we hypothesized that most menopause-related bone loss and changes in bone microstructure are cortical, not trabecular in origin, and are the result of intracortical remodeling. Distal tibial and distal radial microstructure were quantified during 3.1 years (range, 1.5 to 4.5 years) of follow-up using high-resolution peripheral quantitative computed tomography and StrAx software in 199 monozygotic and 125 dizygotic twin pairs aged 25 to 75 years in Melbourne, Australia. The annual increases in tibial cortical porosity accelerated, being 0.44%, 0.80%, and 1.40% in women remaining premenopausal, transitioning to perimenopause, and from perimenopausal to postmenopause, respectively. Porosity increased in the compact-appearing, outer, and inner transitional zones of the cortex (all p < 0.001). The annual decrease in trabecular bone volume/tissue volume (BV/TV) also accelerated, being 0.17%, 0.26%, and 0.31%, respectively. Little bone loss was observed before menopause. The reduction in BV/TV was due to a decrease in trabecular number (p < 0.001). The greatest bone loss, 7.7 mg hydroxyapatite (HA) annually, occurred in women transitioning from perimenopausal to postmenopause and of this, 6.1 mg HA (80%) was cortical. Results were similar for the distal radius. Despite microarchitectural changes, no significant bone loss was observed before menopause. Over 90% of appendicular bone loss occurs during and after menopause, over 80% is cortical, and this may explain why 80% of fractures are appendicular. © 2017 American Society for Bone and Mineral Research.

Serum parathyroid hormone is associated with increased cortical porosity of the inner transitional zone at the proximal femur in postmenopausal women: the Tromsø Study

Serum parathyroid hormone (PTH) was associated with increased bone turnover markers and cortical porosity of the inner transitional zone at the proximal femur. These results suggest that PTH through increased intracortical bone turnover leads to trabecularisation of inner cortical bone in postmenopausal women.

INTRODUCTION

Vitamin D deficiency leads to secondary hyperparathyroidism and increased risk for fractures, whereas its association with cortical porosity is less clear. We tested (i) whether serum 25-hydroxyvitamin D (25(OH)D) and PTH were associated with cortical porosity and (ii) whether the associations of 25(OH)D) and PTH with fracture risk are dependent on cortical porosity.

METHODS

This case-control study included 211 postmenopausal women, 54-94 years old, with prevalent fractures and 232 controls from the Tromsø Study. Serum 25(OH)D, PTH, and bone turnover markers (procollagen type I N-terminal propeptide [PINP] and C-terminal cross-linking telopeptide of type I collagen [CTX]) were measured. Femoral subtrochanteric cortical and trabecular parameters were quantified using computed tomography, and femoral neck areal bone mineral density (FN aBMD) was quantified using dual-energy X-ray absorptiometry.

RESULTS

Compared with controls, fracture cases exhibited reduced serum 25(OH)D and increased PTH, PINP, and CTX, increased femoral subtrochanteric cortical porosity, and reduced cortical thickness and FN aBMD (all, p < 0.05). Serum 25(OH)D was not associated with cortical parameters (all, p > 0.10). PTH was associated with increased PINP, CTX, and cortical porosity of the inner transitional zone and reduced trabecular bone volume/tissue volume and FN aBMD (p ranging from 0.003 to 0.054). Decreasing 25(OH)D and increasing PTH were associated with increased odds for fractures, independent of age, height, weight, calcium supplementation, serum calcium, cortical porosity, and thickness.

CONCLUSIONS

These data suggest that serum PTH, not 25(OH)D, is associated with increased intracortical bone turnover resulting in trabecularisation of the inner cortical bone; nevertheless, decreasing 25(OH)D) and increasing PTH are associated with fracture risk, independent of cortical porosity and thickness.

Women with type 2 diabetes mellitus have lower cortical porosity of the proximal femoral shaft using low-resolution CT than nondiabetic women, and increasing glucose is associated with reduced cortical porosity

Increased cortical porosity has been suggested as a possible factor increasing fracture propensity in patients with type 2 diabetes mellitus (T2DM). This is a paradox because cortical porosity is generally associated with high bone turnover, while bone turnover is reduced in patients with T2DM. We therefore wanted to test the hypothesis that women with T2DM have lower bone turnover markers (BTM) and lower cortical porosity than those without diabetes, and that higher serum glucose and body mass index (BMI) are associated with lower BTM, and with lower cortical porosity. This cross-sectional study is based on a prior nested case-control study including 443 postmenopausal women aged 54-94years from the Tromsø Study, 211 with non-vertebral fracture and 232 fracture-free controls. Of those 443 participants, 22 women exhibited T2DM and 421 women did not have diabetes. All had fasting blood samples assayed for procollagen type I N-terminal propeptide (PINP), C-terminal cross-linking telopeptide of type I collagen (CTX) and glucose, and femoral subtrochanteric architecture was quantified using low-resolution clinical CT and StrAx1.0 software. Women with T2DM had higher serum glucose (7.2 vs. 5.3mmol/L), BMI (29.0 vs. 26.4kg/m²), and higher femoral subtrochanteric total volumetric bone mineral density (vBMD) (783 vs. 715mgHA/cm³), but lower cortical porosity (40.9 vs. 42.8%) than nondiabetic women (all p<0.05). Each standard deviation (SD) increment in glucose was associated with 0.10-0.12 SD lower PINP and CTX, and 0.13 SD lower cortical porosity (all p<0.05). Each SD increment in BMI was associated with 0.10-0.18 SD lower serum PINP and CTX, and 0.19 SD thicker cortices (all p<0.05). Increasing glucose and BMI were associated with lower bone turnover suggesting that reduced intracortical and endocortical remodeling leads to reduced porosity and thicker cortices. Using low-resolution clinical CT, cortical porosity was lower in women with T2DM compared to women without diabetes. This indicates that other changes in bone qualities, not increased cortical porosity, are likely to explain the increased fracture propensity in patients with T2DM.

Irreversible Deterioration of Cortical and Trabecular Microstructure Associated With Breastfeeding

Estrogen deficiency associated with menopause is accompanied by an increase in the rate of bone remodeling and the appearance of a remodeling imbalance; each of the greater number of remodeling transactions deposits less bone than was resorbed, resulting in microstructural deterioration. The newly deposited bone is also less completely mineralized than the older bone resorbed. We examined whether breastfeeding, an estrogen-deficient state, compromises bone microstructure and matrix mineral density. Distal tibial and distal radial microarchitecture were quantified using high-resolution peripheral quantitative computed tomography in 58 women before, during, and after breastfeeding and in 48 controls during follow-up of 1 to 5 years. Five months of exclusive breastfeeding increased cortical porosity by 0.6% (95% confidence interval [CI] 0.3-0.9), reduced matrix mineralization density by 0.26% (95% CI 0.12-0.41) (both p < 0.01), reduced trabecular number by 0.22 per mm (95% CI 0.15-0.28), and increased trabecular separation by 0.07 mm (95% CI 0.05-0.08) (all p < 0.001). Relative to prebreastfeeding, at a median of 2.6 years (range 1 to 4.8) after cessation of breastfeeding, cortical porosity remained 0.58 SD (95% CI 0.48-0.68) higher, matrix mineralization density remained 1.28 SD (95% CI 1.07-1.49) lower, and trabeculae were 1.33 SD (95% CI 1.15-1.50) fewer and 1.06 SD (95% CI 0.91-1.22) more greatly separated (all p < 0.001). All deficits were greater than in controls. The results were similar at distal radius. Bone microstructure may be irreversibly deteriorated after cessation of breastfeeding at appendicular sites. Studies are needed to establish whether this deterioration compromises bone strength and increases fracture risk later in life. © 2016 American Society for Bone and Mineral Research.

The clinical contribution of cortical porosity to fragility fractures

Cortical bone is not compact; rather it is penetrated by many Haversian and Volkmann canals for blood supply. The lining of these canals are the intracortical bone surfaces available for bone remodeling. Increasing intracortical bone remodeling increases cortical porosity. However, cortical bone loss occurs more slowly than trabecular loss due to the fact that less surface per unit of bone matrix volume is available for bone remodeling. Nevertheless, most of the bone loss over time is cortical because cortical bone constitutes 80% of the skeleton, and the relative proportion of trabecular bone diminishes with advancing age. Higher serum levels of bone turnover markers are associated with higher cortical porosity of the distal tibia and the proximal femur. Greater porosity of the distal radius is associated with higher odds for forearm fracture, and greater porosity of the proximal femur is associated with higher odds for non-vertebral fracture in postmenopausal women. Measurement of cortical porosity contributes to fracture risk independent of areal bone mineral density and Fracture Risk Assessment Tool. On the other hand, antiresorptive treatment reduces porosity at the distal radius and at the proximal femoral shaft. Thus, porosity is a substantial determinant of the bone fragility that underlies the risk of fractures and may be a target for fracture prevention.

Determinants of Transitional Zone Area and Porosity of the Proximal Femur Quantified In Vivo in Postmenopausal Women

Bone architecture as well as size and shape is important for bone strength and risk of fracture. Most bone loss is cortical and occurs by trabecularization of the inner part of the cortex. We therefore wanted to identify determinants of the bone architecture, especially the area and porosity of the transitional zone, an inner cortical region with a large surface/matrix volume available for intracortical remodeling. In 211 postmenopausal women aged 54 to 94 years with nonvertebral fractures and 232 controls from the Tromsø Study, Norway, we quantified femoral subtrochanteric architecture in CT images using StrAx1.0 software, and serum levels of bone turnover markers (BTM, procollagen type I N-terminal propeptide and C-terminal cross-linking telopeptide of type I collagen). Multivariable linear and logistic regression analyses were used to quantify associations of age, weight, height, and bone size with bone architecture and BTM, and odds ratio (OR) for fracture. Increasing age, height, and larger total cross-sectional area (TCSA) were associated with larger transitional zone CSA and transitional zone CSA/TCSA (standardized coefficients [STB] = 0.11 to 0.80, p ≤ 0.05). Increasing weight was associated with larger TCSA, but smaller transitional zone CSA/TCSA and thicker cortices (STB = 0.15 to 0.22, p < 0.01). Increasing height and TCSA were associated with higher porosity of the transitional zone (STB = 0.12 to 0.46, p < 0.05). Increasing BTM were associated with larger TCSA, larger transitional zone CSA/TCSA, and higher porosity of each of the cortical compartments (p < 0.01). Fracture cases exhibited larger transitional zone CSA and higher porosity than controls (p < 0.001). Per SD increasing CSA and porosity of the transitional zone, OR for fracture was 1.71 (95% CI, 1.37 to 2.14) and 1.51 (95% CI, 1.23 to 1.85), respectively. Cortical bone architecture is determined mainly by bone size as built during growth and is modified by lifestyle factors throughout life through bone turnover. Fracture cases exhibited larger transitional zone area and porosity, highlighting the importance of cortical bone architecture for fracture propensity.

Bone turnover markers are associated with higher cortical porosity, thinner cortices, and larger size of the proximal femur and non-vertebral fractures

Bone turnover markers (BTM) predict bone loss and fragility fracture. Although cortical porosity and cortical thinning are important determinants of bone strength, the relationship between BTM and cortical porosity has, however, remained elusive. We therefore wanted to examine the relationship of BTM with cortical porosity and risk of non-vertebral fracture. In 211 postmenopausal women aged 54-94 years with non-vertebral fractures and 232 age-matched fracture-free controls from the Tromsø Study, Norway, we quantified femoral neck areal bone mineral density (FN aBMD), femoral subtrochanteric bone architecture, and assessed serum levels of procollagen type I N-terminal propeptide (PINP) and C-terminal cross-linking telopeptide of type I collagen (CTX). Fracture cases exhibited higher PINP and CTX levels, lower FN aBMD, larger total and medullary cross-sectional area (CSA), thinner cortices, and higher cortical porosity of the femoral subtrochanter than controls (p≤0.01). Each SD increment in PINP and CTX was associated with 0.21-0.26 SD lower total volumetric BMD, 0.10-0.14 SD larger total CSA, 0.14-0.18 SD larger medullary CSA, 0.13-0.18 SD thinner cortices, and 0.27-0.33 SD higher porosity of the total cortex, compact cortex, and transitional zone (all p≤0.01). Moreover, each SD of higher PINP and CTX was associated with increased odds for fracture after adjustment for age, height, and weight (ORs 1.49; 95% CI, 1.20-1.85 and OR 1.22; 95% CI, 1.00-1.49, both p<0.05). PINP, but not CTX, remained associated with fracture after accounting for FN aBMD, cortical porosity or cortical thickness (OR ranging from 1.31 to 1.39, p ranging from 0.005 to 0.028). In summary, increased BTM levels are associated with higher cortical porosity, thinner cortices, larger bone size and higher odds for fracture. We infer that this is produced by increased periosteal apposition, intracortical and endocortical remodeling; and that these changes in bone architecture are predisposing to fracture.

Measurement of cortical porosity of the proximal femur improves identification of women with nonvertebral fragility fractures

We tested whether cortical porosity of the proximal femur measured using StrAx1.0 software provides additional information to areal bone mineral density (aBMD) or Fracture Risk Assessment Tool (FRAX) in differentiating women with and without fracture. Porosity was associated with fracture independent of aBMD and FRAX and identified additional women with fractures than by osteoporosis or FRAX thresholds.

INTRODUCTION

Neither aBMD nor the FRAX captures cortical porosity, a major determinant of bone strength. We therefore tested whether combining porosity with aBMD or FRAX improves identification of women with fractures.

METHODS

We quantified femoral neck (FN) aBMD using dual-energy X-ray absorptiometry, FRAX score, and femoral subtrochanteric cortical porosity using StrAx1.0 software in 211 postmenopausal women aged 54-94 years with nonvertebral fractures and 232 controls in Tromsø, Norway. Odds ratios (ORs) were calculated using logistic regression analysis.

RESULTS

Women with fractures had lower FN aBMD, higher FRAX score, and higher cortical porosity than controls (all p < 0.001). Each standard deviation higher porosity was associated with fracture independent of FN aBMD (OR 1.39; 95% confidence interval 1.11-1.74) and FRAX score (OR 1.58; 1.27-1.97) in all women combined. Porosity was also associated with fracture independent of FRAX score in subgroups with normal FN aBMD (OR 1.88; 1.21-2.94), osteopenia (OR 1.40; 1.06-1.85), but not significantly in those with osteoporosis (OR 1.48; 0.68-3.23). Of the 211 fracture cases, only 18 women (9%) were identified using FN aBMD T-score < -2.5, 45 women (21%) using FRAX threshold >20%, whereas porosity >80th percentile identified 61 women (29%). Porosity identified 26% additional women with fractures than identified by the osteoporosis threshold and 21% additional women with fractures than by this FRAX threshold.

CONCLUSIONS

Cortical porosity is a risk factor for fracture independent of aBMD and FRAX and improves identification of women with fracture.

Genetic and environmental variances of bone microarchitecture and bone remodeling markers: a twin study

All genetic and environmental factors contributing to differences in bone structure between individuals mediate their effects through the final common cellular pathway of bone modeling and remodeling. We hypothesized that genetic factors account for most of the population variance of cortical and trabecular microstructure, in particular intracortical porosity and medullary size - void volumes (porosity), which establish the internal bone surface areas or interfaces upon which modeling and remodeling deposit or remove bone to configure bone microarchitecture. Microarchitecture of the distal tibia and distal radius and remodeling markers were measured for 95 monozygotic (MZ) and 66 dizygotic (DZ) white female twin pairs aged 40 to 61 years. Images obtained using high-resolution peripheral quantitative computed tomography were analyzed using StrAx1.0, a nonthreshold-based software that quantifies cortical matrix and porosity. Genetic and environmental components of variance were estimated under the assumptions of the classic twin model. The data were consistent with the proportion of variance accounted for by genetic factors being: 72% to 81% (standard errors ∼18%) for the distal tibial total, cortical, and medullary cross-sectional area (CSA); 67% and 61% for total cortical porosity, before and after adjusting for total CSA, respectively; 51% for trabecular volumetric bone mineral density (vBMD; all p < 0.001). For the corresponding distal radius traits, genetic factors accounted for 47% to 68% of the variance (all p ≤ 0.001). Cross-twin cross-trait correlations between tibial cortical porosity and medullary CSA were higher for MZ (rMZ  = 0.49) than DZ (rDZ  = 0.27) pairs before (p = 0.024), but not after (p = 0.258), adjusting for total CSA. For the remodeling markers, the data were consistent with genetic factors accounting for 55% to 62% of the variance. We infer that middle-aged women differ in their bone microarchitecture and remodeling markers more because of differences in their genetic factors than differences in their environment.

High-sensitivity C-reactive protein is an independent risk factor for non-vertebral fractures in women and men: The Tromsø Study

Low-grade inflammation is associated with fractures, while the relationship between inflammation and bone mineral density (BMD) is less clear. Moreover, any gender differences in the sensitivity to inflammation are still poorly elucidated. We therefore tested the hypothesis that high-sensitivity C-reactive protein (CRP) is an independent risk factor for low BMD and non-vertebral fractures, in both genders, and whether there are gender differences in these associations. CRP levels and BMD at the total hip and femoral neck were measured in 1902 women and 1648 men between 55 and 74 years of age, at baseline in the Tromsø Study, Norway, in 2001-2002. Non-vertebral fractures were registered from hospital X-ray archives during an average of 7.2 years follow-up. Linear regression analyses were used for CRP association with BMD and Cox proportional hazards model for fracture prediction by CRP. During 25 595 person-years follow-up, 366 (19%) women and 126 (8%) men suffered a non-vertebral fracture. There was no association between CRP and BMD in women, but an inverse association in men (p=0.001) after adjustment for age and body mass index. Each standard deviation (SD) increase in log-CRP was associated with an increased risk for non-vertebral fracture by 13% in women and 22% in men (hazard ratios (HRs) 1.13, 95% confidence interval (CI) 1.02-1.26, p=0.026 and 1.22, 95% CI=1.00-1.48, p=0.046, respectively). After adjustment for BMD and other risk factors, women with CRP in the upper tertile exhibited 39% higher risk for fracture than those in the lowest tertile of CRP (HR = 1.39, 95% CI = 1.06-1.83, p = 0.017), while men in the upper tertile exhibited 80% higher risk (HR=1.80, 95% CI=1.10-2.94, p=0.019). In summary, CRP was not associated with BMD in women but inversely associated in men, and predicted fractures in both genders. We infer that inflammation influence fracture risk in both women and men, although the biological mechanisms may differ between the genders.

External validation of the Garvan nomograms for predicting absolute fracture risk: the Tromsø study

Background

Absolute risk estimation is a preferred approach for assessing fracture risk and treatment decision making. This study aimed to evaluate and validate the predictive performance of the Garvan Fracture Risk Calculator in a Norwegian cohort.

Methods

The analysis included 1637 women and 1355 aged 60+ years from the Tromsø study. All incident fragility fractures between 2001 and 2009 were registered. The predicted probabilities of non-vertebral osteoporotic and hip fractures were determined using models with and without BMD. The discrimination and calibration of the models were assessed. Reclassification analysis was used to compare the models performance.

Results

The incidence of osteoporotic and hip fracture was 31.5 and 8.6 per 1000 population in women, respectively; in men the corresponding incidence was 12.2 and 5.1. The predicted 5-year and 10-year probability of fractures was consistently higher in the fracture group than the non-fracture group for all models. The 10-year predicted probabilities of hip fracture in those with fracture was 2.8 (women) to 3.1 times (men) higher than those without fracture. There was a close agreement between predicted and observed risk in both sexes and up to the fifth quintile. Among those in the highest quintile of risk, the models over-estimated the risk of fracture. Models with BMD performed better than models with body weight in correct classification of risk in individuals with and without fracture. The overall net decrease in reclassification of the model with weight compared to the model with BMD was 10.6% (p = 0.008) in women and 17.2% (p = 0.001) in men for osteoporotic fractures, and 13.3% (p = 0.07) in women and 17.5% (p = 0.09) in men for hip fracture.

Conclusions

The Garvan Fracture Risk Calculator is valid and clinically useful in identifying individuals at high risk of fracture. The models with BMD performed better than those with body weight in fracture risk prediction.

Cortical porosity identifies women with osteopenia at increased risk for forearm fractures

Most fragility fractures arise among the many women with osteopenia, not the smaller number with osteoporosis at high risk for fracture. Thus, most women at risk for fracture assessed only by measuring areal bone mineral density (aBMD) will remain untreated. We measured cortical porosity and trabecular bone volume/total volume (BV/TV) of the ultradistal radius (UDR) using high-resolution peripheral quantitative computed tomography, aBMD using densitometry, and 10-year fracture probability using the country-specific fracture risk assessment tool (FRAX) in 68 postmenopausal women with forearm fractures and 70 age-matched community controls in Olmsted County, MN, USA. Women with forearm fractures had 0.4 standard deviations (SD) higher cortical porosity and 0.6 SD lower trabecular BV/TV. Compact-appearing cortical porosity predicted fracture independent of aBMD; odds ratio (OR) = 1.92 (95% confidence interval [CI] 1.10–3.33). In women with osteoporosis at the UDR, cortical porosity did not distinguish those with fractures from those without because high porosity was present in 92% and 86% of each group, respectively. By contrast, in women with osteopenia at the UDR, high porosity of the compact-appearing cortex conferred an OR for fracture of 4.00 (95% CI 1.15–13.90). In women with osteoporosis, porosity is captured by aBMD, so measuring UDR cortical porosity does not improve diagnostic sensitivity. However, in women with osteopenia, cortical porosity was associated with forearm fractures.

Fracture risk and height: an association partly accounted for by cortical porosity of relatively thinner cortices

Taller women are at increased risk for fracture despite having wider bones that better tolerate bending. Because wider bones require less material to achieve a given bending strength, we hypothesized that taller women assemble bones with relatively thinner and more porous cortices because excavation of a larger medullary canal may be accompanied by excavation of more intracortical canals. Three-dimensional images of distal tibia, fibula, and radius were obtained in vivo using high-resolution peripheral quantitative computed tomography (HRpQCT) in a twin study of 345 females aged 40 to 61 years, 93 with at least one fracture. Cortical porosity <100 µm as well as >100 µm, and microarchitecture, were quantified using Strax1.0, a new algorithm. Multivariable linear and logistic regression using generalized estimating equation (GEE) methods quantified associations between height and microarchitecture and estimated the associations with fracture risk. Each standard deviation (SD) greater height was associated with a 0.69 SD larger tibia total cross-sectional area (CSA), 0.66 SD larger medullary CSA, 0.50 SD higher medullary CSA/total CSA (i.e., thinner cortices relative to the total CSA due to a proportionally larger medullary area), and 0.42 SD higher porosity (all p < 0.001). Cortical area was 0.45 SD larger in absolute terms but 0.50 SD smaller in relative terms. These observations were confirmed by examining trait correlations in twin pairs. Fracture risk was associated with height, total CSA, medullary CSA/total CSA, and porosity in univariate analyses. In multivariable analyses, distal tibia, medullary CSA/total CSA, and porosity predicted fracture independently; height was no longer significant. Each 1 SD greater porosity was associated with fracture; odds ratios (ORs) and 95% confidence intervals (CIs) are as follows: distal tibia, OR = 1.55 (95% CI, 1.11-2.15); distal fibula, OR = 1.47 (95% CI, 1.14-1.88); and distal radius, OR = 1.22 (95% CI, 0.96-1.55). Taller women assemble wider bones with relatively thinner and more porous cortices predisposing to fracture.

Osteoprotegerin is associated with hip fracture incidence: the Tromso Study

BACKGROUND

Osteoprotegerin (OPG) is a cytokine essential for the regulation of bone resorption, but large longitudinal studies on its relationship to fracture risk in humans are lacking. In this population-based study of 2740 men and 2857 post-menopausal women, it was examined whether serum OPG was associated with hip fracture incidence. The participants were followed for 15 years.

METHODS

Baseline measurements included height, weight and serum OPG, and information about lifestyle, prevalent diseases and use of medication.

RESULTS

Men with OPG in the highest quartile were 2.79-fold [95% confidence interval (CI) 1.34-5.82] more likely to have a hip fracture during follow-up, compared with those with OPG in the lowest quartile (P-trend over OPG quartiles ≤ 0.001, after adjustments for age and other confounders). In women not using post-menopausal hormone therapy (HT), the risk of hip fracture was 1.64-fold higher (95% CI 0.94-2.86) in the highest quartile compared with the lowest OPG quartile (P-trend over OPG quartiles = 0.05). No relationship was found in post-menopausal women using HT (P-trend over OPG quartiles = 0.23).

CONCLUSIONS

In men, OPG was positively associated with the incidence of hip fracture. In post-menopausal women not using HT a similar, but weaker, relationship was found.

Remodeling markers are associated with larger intracortical surface area but smaller trabecular surface area: a twin study

All postmenopausal women become estrogen deficient but not all remodel their skeleton rapidly or lose bone rapidly. As remodeling requires a surface to be initiated upon, we hypothesized that a volume of mineralized bone assembled with a larger internal surface area is more accessible to being remodeled, and so decayed, after menopause. We measured intracortical, endocortical and trabecular bone surface area and microarchitecture of the distal tibia and distal radius in 185 healthy female twin pairs aged 40 to 61 years using high-resolution peripheral quantitative computed tomography (HR-pQCT). We used generalized estimation equations to analyze (i) the trait differences across menopause, (ii) the relationship between remodeling markers and bone surface areas, and (iii) robust regression to estimate associations between within-pair differences. Relative to premenopausal women, postmenopausal women had higher remodeling markers, larger intracortical and endocortical bone surface area, higher intracortical porosity, smaller trabecular bone surface area and fewer trabeculae at both sites (all p<0.01). Postmenopausal women had greater deficits in cortical than trabecular bone mass at the distal tibia (-0.98 vs. -0.12 SD, p<0.001), but similar deficits at the distal radius (-0.45 vs. -0.39 SD, p=0.79). A 1 SD higher tibia intracortical bone surface area was associated with 0.22-0.29 SD higher remodeling markers, about half the 0.53-0.67 SD increment in remodeling markers across menopause (all p<0.001). A 1 SD higher porosity was associated with 0.20-0.30 SD higher remodeling markers. A 1 SD lower trabecular bone surface area was associated with 0.15-0.18 SD higher remodeling markers (all p<0.01). Within-pair differences in intracortical and endocortical bone surface areas at both sites and porosity at the distal tibia were associated with within-pair differences in some remodeling markers (p=0.05 to 0.09). We infer intracortical remodeling may be self perpetuating by creating intracortical porosity and so more bone surface for remodeling to occur upon, while remodeling upon the trabecular bone surface is self limiting because it removes trabeculae with their surface.