Structural determinants of hip fracture in elderly women: re-analysis of the data from the EPIDOS study

In peripubertal girls, artistic gymnastics improves areal bone mineral density and femoral bone geometry without affecting serum OPG/RANKL levels

Peripubertal artistic gymnasts display elevated areal bone mineral density at various bone sites, despite delayed menarche and a high frequency of menstrual disorders, factors that may compromise bone health. The concomitant improvement in femoral bone geometry and strength suggested that this type of physical activity might have favourable clinical impact.

INTRODUCTION

The purpose of this study is to evaluate the effect of artistic gymnastics (GYM) on areal bone mineral density (aBMD), femoral bone geometry and bone markers and its relationship with the osteoprotegerin (OPG)/rank-ligand (RANKL) system in peripubertal girls.

METHODS

Forty-six girls (age 10-17.2 years) were recruited for this study: 23 elite athletes in the GYM group (training 12-30 h/week, age at start of training 5.3 years) and 23 age-matched (± 6 months; leisure physical activity ≤ 3 h/week) controls (CON). The aBMD at whole body, total proximal femur, lumbar spine, mid-radius and skull was determined using dual-X-ray absorptiometry. Hip structural analysis (HSA software) was applied at the femur to evaluate cross-sectional area (CSA, cm(2)), cross-sectional moment of inertia (CSMI, cm(4)), and the section modulus (Z, cm(3)) and buckling ratio at neck, intertrochanteric region and shaft. Markers of bone turnover and OPG/RANKL levels were also analysed.

RESULTS

GYM had higher (5.5-16.4%) non-adjusted aBMD and adjusted aBMD for age, fat-free soft tissue and fat mass at all bone sites, skull excepted and the difference increased with age. In the three femoral regions adjusted for body weight and height, CSA (12.5-18%), CSMI (14-18%), Z (15.5-18.6%) and mean cortical thickness (13.6-21%) were higher in GYM than CON, while the buckling ratio (21-27.1%) was lower. Bone markers decreased with age in both groups and GYM presented higher values than CON only in the postmenarchal period. A similar increase in RANKL with age without OPG variation was observed for both groups.

CONCLUSION

GYM is associated not only with an increase in aBMD but also an improvement in bone geometry associated with an increase in bone remodelling. These adaptations seem to be independent of the OPG/RANKL system.

Age trends for hip geometry in Chinese men and women and the association with femoral neck fracture

Hip dual-energy X-ray absorptiometry (DXA) images were used to calculate hip bone mineral density (BMD) and hip geometry parameters of 18,502 healthy Chinese people (14,435 women and 4,067 men), 254 subjects sustained a femoral neck fracture and 254 age- and sex-matched controls. Our study showed that thinning of the cortical shell and deterioration of the strength index (SI) in femoral neck with aging in both Chinese men and women. SI may be a risk factor for hip fracture in Chinese women.

INTRODUCTION

The purpose of this study was to evaluate age-related trends in the hip geometry of healthy Chinese men and women and to examine whether changes in hip geometric parameters is one of the risk factors of hip fracture.

METHODS

We recruited 14,435 women and 4,067 men as the study population. There were 254 subjects (216 women, 38 men) who had sustained a femoral neck fracture; 254 age- and sex-matched healthy persons served as controls. Hip DXA images were used to calculate hip BMD and hip geometry parameters, including the hip axis length (HAL), cross-sectional moment of inertia (CSMI), cross-sectional area (CSA), neck-shaft angle (NSA) and femoral SI.

RESULTS

Hip BMD, CSMI, CSA and SI showed significantly negative correlations with age. However, after adjustment for height and weight, HAL increased with age, and there was no strong correlation between CSMI and age in either sex. In both genders, hip BMD and CSA were significant lower in fracture cases compared with controls. After adjustment for hip BMD, in women only smaller SI (odds ratio [OR] 1.53; 95% confidence interval [CI], 1.04-2.26) was predictive of hip fracture but in men, none of the geometry parameters was associated with hip fracture risk.

CONCLUSIONS

This study demonstrated thinning of the cortical shell and deterioration of the resistance to bending and SI with aging in femoral neck in Chinese men and women. SI may be a risk factor for hip fracture that is independent of BMD measurement in Chinese women.

Surgical treatment options in patients with impaired bone quality

BACKGROUND

Bone quality should play an important role in decision-making for orthopaedic treatment options, implant selection, and affect ultimate surgical outcomes. The development of decision-making tools, currently typified by clinical guidelines, is highly dependent on the precise definition of the term(s) and the appropriate design of basic and clinical studies. This review was performed to determine the extent to which the issue of bone quality has been subjected to this type of process.

QUESTIONS/PURPOSES

We address the following issues: (1) current methods of clinically assessing bone quality; (2) emerging technologies; (3) how bone quality connects with surgical decision-making and the ultimate surgical outcome; and (4) gaps in knowledge that need to be closed to better characterize bone quality for more relevance to clinical decision-making.

METHODS

PubMed was used to identify selected papers relevant to our discussion. Additional sources were found using the references cited by identified papers.

RESULTS

Bone mineral density remains the most commonly validated clinical reference; however, it has had limited specificity for surgical decision-making. Other structural and geometric measures have not yet received enough study to provide definitive clinical applicability. A major gap remains between the basic research agenda for understanding bone quality and the transfer of these concepts to evidence-based practice.

CONCLUSIONS

Basic bone quality needs better definition through the systematic study of emerging technologies that offer a more precise clinical characterization of bone. Collaboration between basic scientists and clinicians needs to improve to facilitate the development of key questions for sound clinical studies.

Combination of radiograph-based trabecular and geometrical parameters can discriminate cervical hip fractures from controls in individuals with BMD in non-osteoporotic range

Majority of hip fractures occur in individuals with bone mineral density (BMD) in non-osteoporotic range. This suggests that factors other than BMD are associated with increased fracture risk in these individuals. The aim of this study was to investigate the combined ability of radiograph-based trabecular and geometrical parameters to discriminate cervical hip fractures from controls in individuals with non-osteoporotic BMD. A total of 39 postmenopausal females with non-pathologic cervical hip fracture were recruited to the study. Nineteen of the fracture patients (48.7%) had non-osteoporotic BMD and they constituted the fracture group. The control group consisted of 35 BMD-matched non-osteoporotic females. Several geometrical and trabecular parameters were extracted from plain pelvic radiographs, and their combined ability to discriminate fracture patients from controls was studied using a receiver operating characteristics (ROC) analysis. Significant differences in several radiograph-based geometrical and trabecular parameters were found between the fracture patients and controls, whereas no statistically significant difference in BMD was observed (p=0.92) between the groups. Area under the ROC curve was 0.993 (95% CI 0.977-1.008) for the combined multiple regression model, which included both trabecular and geometrical parameters as explanatory factors. Here, the sensitivity of 100% was achieved with the specificity of 94%. In a cross-validation of the model, 94.4% of the fracture patients, and 94.1% of the controls were classified correctly. The combination of radiograph-based trabecular and geometrical parameters was able to discriminate the cervical hip fracture cases from controls with similar BMD, showing that the method can provide additional information on bone structure and fracture risk beyond BMD.

Differences in femoral neck geometry associated with age and ethnicity

SUMMARY

We studied femoral geometry in relation to age and ethnicity in a cross-sectional study. Age-associated cortical thinning showed the most pronounced effect, and Koreans studied here had thicker cortices and lower buckling ratios than those reported for other races. Cortical thickness may thus be a major determinant of hip fracture risk.

INTRODUCTION

The rate of hip fracture varies by age and ethnicity. The geometric properties of the femur influence femoral strength and fragility, but differences in femoral geometry according to age and ethnicity are poorly understood. To explain the high prevalence of hip fractures in the elderly and the relatively low hip fracture rate in Asian populations, we studied age-related changes and ethnic differences in femoral geometry.

METHODS

We recruited 214 peri- or postmenopausal women aged 46 to 85 years (mean age, 60.6 years). Their proximal femoral bone mineral densities (BMD) were measured by quantitative computed tomography and further analyzed geometric properties.

RESULTS

We observed large declines in trabecular volumetric bone mineral density associated with aging (33.03% less than the reference value in the oldest group, respectively). Cortical thickness decreased remarkably with age as well, and only 53.94% of the baseline value remained in the oldest group. As a result, the cortical buckling ratio increased geometrically and reached 239.14% of the reference value in the oldest group. In comparisons with other ethnic groups, Korean subjects had thicker cortices than their American, European, and African counterparts.

CONCLUSIONS

In this cross-sectional study, cortical thickness showed a pronounced age-associated decrease, and the cortical buckling ratio showed a strong age-associated increase. This may in part explain the higher rates of hip fractures in the elderly. When compared with other races, Asians had thicker cortical bone and lower buckling ratios, which may partially explain the lower prevalence of hip fractures in Asians.

Smaller, weaker, and less stiff bones evolve from changes in subsistence strategy

We propose a computational model with which to examine the evolution of bone. Our results indicate that changes in subsistence strategy have influenced the evolution of bone growth and mechanoregulation, and predict that bone size, stiffness, and structural strength may decrease in future generations, bringing increased risk of fracture and prevalence of osteoporosis.

INTRODUCTION

Archeological data suggest that bone size and strength have decreased over evolution. We hypothesize that changing evolutionary pressures and levels of physical activity, both arising from changes in subsistence strategy, have affected the evolution of bone. We propose a computational model with which to examine the evolution of bone growth and mechanoregulation due to the transitions from hunter-gatherer to agricultural to modern lifestyles.

METHODS

The evolution of genes governing growth and mechanoregulation in a population of bones is simulated, where each individual is represented by a 2-D bone cross-section. Genetic variability is assumed to modulate growth through mechanoregulatory factors that direct periosteal expansion, endosteal expansion/infilling, and ash content accretion in response to strains incurred during walking.

RESULTS

The model predicts decreases in cortical area and section modulus (a measure of structural strength) and increases in maximum compressive strain over the course of the simulation, meaning evolution of smaller, less strong, and less stiff bones is predicted for the population average. The model predicts small but continued decreases in size, strength, and stiffness in modern populations, despite the absence of a strong evolutionary advantage to efficient bones during this phase.

CONCLUSION

In conclusion, our results show that changing loading regimes and evolutionary pressures may have influenced the evolution of bone growth and mechanoregulation, and predict that bone size and strength may continue to decrease in future generations, bringing increased risk of fracture and prevalence of osteoporosis.

Age-specific reference values of hip geometric indices from a representative sample of the Japanese female population: Japanese Population-based Osteoporosis (JPOS) Study

We analyzed 2,107 hip dual-energy X-ray absorptiometry (DXA) images from the Japanese Population-based Osteoporosis Study with the Hip Structure Analysis (HSA) program to obtain age-specific reference values of HSA indices for the Japanese female population. These references may help physicians accurately assess HSA results and aid researchers in making interracial comparisons of the indices.

INTRODUCTION

Hip geometry is expected to improve hip fracture risk assessment, which is usually assessed by bone mineral density (BMD) alone. We aimed to establish a reference database for Japanese women.

METHODS

We studied 2,107 Japanese women (15-79 years old) with no history of bone metabolism-related diseases from the Japanese Population-based Osteoporosis Study performed in 1996. Hip geometry was conducted on DXA images with the HSA program, which yielded data for cross-sectional area (CSA), subperiosteal diameter (PD), endocortical diameter (ED), mean cortical thickness (CT), section modulus (SM), and buckling ratio at the narrow neck (NN), intertrochanter (IT), and femoral shaft (FS) regions. Mean HSA indices were determined for each 5-year age group after adjustment for height and weight based on most recent Japanese population values.

RESULTS

Age-related changes in HSA indices were evident for the 50-54 year group in the NN and IT regions and for the 55-59 year group in the FS region; these changes increased with age thereafter. Age-related changes in CSA and CT were almost identical to that of BMD. Japanese subjects exhibited BMD and CT values similar to those reported for US non-Hispanic white women, but had 16-23% smaller SM values. CSA and CT were highly correlated with conventional BMD, whereas ED, SM, and PD showed lower correlations.

CONCLUSIONS

Age-specific reference values of HSA indices for the Japanese female population were obtained. This database will form the foundation for accurate HSA result evaluation.

Anatomical variance in acetabular anteversion does not predict hip fracture patterns in the elderly: a retrospective study in 135 patients

It has been suggested that variances in the anatomy of the acetabulum determine the type of hip fracture in elderly patients. Based on this concept, an overly anteverted acetabulum would lead to impingement of the femoral neck against the posterior rim of the acetabulum, causing a femoral neck fracture, whereas with a retroverted acetabulum, external rotation of the hip would be limited by the capsular tissues attached to the trochanteric region, causing a trochanteric fracture. To test the hypothesis that acetabular version predicts hip fracture type in elderly patients, we measured acetabular version using computed tomography scans for 135 patients with hip fracture. Logistic regression analysis was used to check for an association between version angle and fracture type. No significant relationship between acetabular version and fracture type was found. Therefore, we conclude that acetabular version angle does not predict hip fracture type in the elderly, and our data do not support the impingement concept as the mechanism of hip fractures.

Risedronate improves proximal femur bone density and geometry in patients with osteoporosis or osteopenia and clinical risk factors of fractures: a practice-based observational study

The purpose of this practice-based observational study was to clarify the acute effect of risedronate on proximal femur bone mineral density (BMD) and structural geometry in patients with an increased risk of fractures. One hundred sixty-four patients (7 men and 157 postmenopausal women; mean age, 69.2 years) with osteoporosis or osteopenia and clinical risk factors of fractures were analyzed. All these patients were treated with risedronate for 1 year. Urinary levels of cross-linked N-terminal telopeptide of type I collagen (NTX) were measured at baseline and 4 months after the start of treatment. BMD of the lumbar spine and proximal femur and structural geometric parameters of the proximal femur were evaluated by dual-energy X-ray absorptiometry with advanced hip assessment (AHA) software at baseline and every 4 months. Urinary NTX levels significantly decreased after 4 months of treatment. BMD of the femoral neck and total hip significantly increased after 4, 8, and 12 months of treatment. Cross-sectional moment of inertia (CSMI) and cross-sectional area significantly increased after 4, 8, and 12 months of treatment. An increase in CSMI was apparently greater than those of proximal femur BMD after 4 months of treatment. These results suggest the acute (4 months) and sustained (12 months) effect of risedronate on proximal femur structural geometry as well as BMD as a result of suppression of bone resorption in patients with an increased risk of fractures.

Structural asymmetry between the hips and its relation to experimental fracture type

Experimental analysis with paired femurs provides the opportunity to study within-person differences in fracture type and associated structural side differences. We hypothesized that different fracture types in the hips of a subject are associated with structural asymmetry. Bone mineral density (BMD) and structural measurements of paired cadaver femurs (32 females, 24 males) were performed before mechanical testing in a side-impact configuration. Fractures were classified (cervical or trochanteric) and differences in structural parameters, BMD, and failure load were evaluated between the left and right hips as well as between experimental fracture types. We observed larger dimensions (P < 0.05-0.01), thicker cortices (P < 0.05-0.001), and a smaller femoral shaft diameter (FSD) (P < 0.01) in the left hip than in the right. Seventeen pairs (30.4%) had trochanteric fractures on one side and cervical on the contralateral side. The asymmetric trochanteric fracture side had a higher head/neck diameter ratio (HD/ND) (P < 0.05) and a trend toward a lower neck-shaft angle (NSA) (P = 0.066) than its collateral cervical side in females and a lower HD and higher FSD (P < 0.05) in males. In females, asymmetric fracture cases displayed lower NSA (P < 0.001) and HD/ND (P < 0.01) than symmetric cervical ones. In males, asymmetric fracture cases showed larger dimensions than the other groups (P < 0.05-0.01). BMD increased from symmetric cervical to asymmetric and then to symmetric trochanteric cases (P < 0.05-0.01), with the experimental failure load showing a similar trend. In conclusion, intrasubject structural asymmetry is associated with asymmetric fracture types. Asymmetry should be considered when using the opposite side as control in clinical studies.

Hip fracture type: important role of parathyroid hormone (PTH) response to hypovitaminosis D

OBJECTIVE

To investigate whether clinical and laboratory characteristics, including serum 25-hydroxyvitamin D (25(OH) D), PTH and parameters of mineral and bone metabolism, differ by hip fracture (HF) type.

PATIENTS AND METHODS

We studied prospectively 761 consecutively admitted older patients (mean age 82.3+8.8(SD) years; 74.9% women) with low trauma non-pathological HF. A detailed clinical examination was performed, haematologic, renal, liver and thyroid function tests, serum 25(OH)D, PTH, calcium, phosphate, magnesium, C-reactive protein (CRP) and cardiac troponin I (cTnI) measured. In a subset of 294 patients' markers of bone formation (serum osteocalcin, OC; bone specific alkaline phosphatase, BAP) and bone resorption (urinary deoxypyridinoline, DPD/Cr; N-terminal cross-linked telopeptide of type 1 collagen, NTx/Cr; both corrected to urinary creatinine, Cr) were also measured.

RESULTS

In the trochanteric compared to the cervical group, females were older than males and the prevalence of Parkinson's disease, mean haemoglobin and albumin levels were lower. Incidence and degree of myocardial injury (cTnl rise) and inflammatory reaction (CRP elevation) as well as length of hospital stay, need of institutionalisation or in-hospital mortality were similar in both groups. Hypovitaminosis D (25(OH)D <50 mmol/L) was present in 77.8% of patients with cervical and in 82.1% with trochanteric HF, elevated PTH (>6.8 pmol/L) in 30.2% and 41.3%, respectively. The associations between 25(OH)D, PTH, and parameters of mineral metabolism and bone turnover were site-specific. In multivariate analyses, PTH (both as a continuous or categorical variable) response to hypovitaminosis D was a strong independent predictor of HF type. Coexistence of vitamin D deficiency (25(OH) D< 25 nmol/L) and elevated PTH predicts trochanteric HF while blunted PTH response predicts cervical HF (OR=3.5; 95% CI 1.5-80; p=0.005). PTH response and phosphate status (above or below median level) correctly discriminated HF type in 73.8% of patients with vitamin D deficiency.

CONCLUSIONS

HF type is significantly associated with PTH response to hypovitaminosis D and impaired phosphate homeostasis. We detected only minor differences between two main HF types with regard to a wide range of clinical and routine laboratory variables as well as short-term outcomes.

BMD T-score discriminates trochanteric fractures from unfractured controls, whereas geometry discriminates cervical fracture cases from unfractured controls of similar BMD

The ability of bone mineral density (BMD) to discriminate cervical and trochanteric hip fractures was studied. Since the majority of fractures occur among people who are not diagnosed as having osteoporosis, we also examined this population to elucidate whether geometrical risk factors can yield additional information on hip fracture risk beside BMD. The study showed that the T-score criterion was able to discriminate fracture patients from controls in the cases of trochanteric fractures, whereas geometrical measures may discriminate cervical fracture cases in patients with T-score >-2.5.

INTRODUCTION

Low bone mineral density (BMD) is a well-established risk factor for hip fracture. However, majority of fractures occur among people not diagnosed as having osteoporosis. We studied the ability of BMD to discriminate cervical and trochanteric hip fractures. Furthermore, we examined whether geometrical measures can yield additional information on the assessment of hip fracture risk in the fracture cases in subjects with T-score >-2.5.

METHODS

Study group consisted of postmenopausal females with non-pathologic cervical (n = 39) or trochanteric (n = 18) hip fracture (mean age 74.2 years) and 40 age-matched controls. BMD was measured at femoral neck, and femoral neck axis length, femoral neck and shaft cortex thicknesses (FNC and FSC), and femoral neck-shaft angle (NSA) were measured from radiographs.

RESULTS

BMD T-score threshold of -2.5 was able to discriminate trochanteric fractures from controls (p < 0.001). Seventeen out of 18 trochanteric fractures occurred in individuals with T-score <or=-2.5. However, the T-score criterion was not able to discriminate cervical fractures. Twenty of these fractures (51.3%) occurred in individuals with BMD in osteoporotic range and 19 (48.7%) in individuals with T-score >-2.5. Within these non-osteoporotic cervical fracture patients (N = 19) and non-osteoporotic controls (N = 35), 83.3% were classified correctly based on a model including NSA and FNC (p < 0.001), area under the receiver operating characteristics curve being 0.85 for the model, while it was only 0.56 for BMD alone.

CONCLUSIONS

The study suggests that the risk of trochanteric fractures could be discriminated based on a BMD T-score <-2.5 criterion, whereas cervical fracture cases would remain under-diagnosed if solely using this criterion. Instead, geometrical risk factors are able to discriminate cervical fracture cases even among individuals with T-score >-2.5. For cervical and trochanteric fractures combined, BMD and geometric measures independently contributed to hip fracture discrimination. Our data support changing from T-score <-2.5 to a more comprehensive assessment of hip fracture etiology, in which fracture type is also taken into account. The findings need to be confirmed with a larger sample, preferably in a prospective study.

Functional consequences of sarcopenia and dynapenia in the elderly

PURPOSE OF REVIEW

The economic burden due to the sequela of sarcopenia (muscle wasting in the elderly) are staggering and rank similarly to the costs associated with osteoporotic fractures. In this article, we discuss the societal burden and determinants of the loss of physical function with advancing age, the physiologic mechanisms underlying dynapenia (muscle weakness in the elderly), and provide perspectives on related critical issues to be addressed.

RECENT FINDINGS

Recent epidemiological findings from longitudinal aging studies suggest that dynapenia is highly associated with both mortality and physical disability even when adjusting for sarcopenia indicating that sarcopenia may be secondary to the effects of dynapenia. These findings are consistent with the physiologic underpinnings of muscle strength, as recent evidence demonstrates that alterations in muscle quantity, contractile quality and neural activation all collectively contribute to dynapenia.

SUMMARY

Although muscle mass is essential for regulation of whole body metabolic balance, overall neuromuscular function seems to be a critical factor for maintaining muscle strength and physical independence in the elderly. The relative contribution of physiologic factors contributing to muscle weakness are not fully understood and further research is needed to better elucidate these mechanisms between muscle groups and across populations.

O olhar e o sentir do idoso no pós-queda

A queda de idosos é um problema de relevância para a saúde pública no que diz respeito aos desfechos que esse incidente pode desencadear. Sendo assim, esta pesquisa se propôs a uma melhor compreensão, sob a ótica do idoso, do que se passa após esse incidente. Tratou-se de um estudo de natureza qualitativa realizado com idosos internados em um hospital de urgências de Goiânia (GO) devido às consequências da queda. A amostra constituiu-se de 12 entrevistas semiestruturadas, gravadas e transcritas. A análise das informações seguiu os seguintes passos metodológicos: entrevistas e gravações simultâneas, anotações em diários de campo, transcrição das entrevistas, leitura analítica, classificação em categorias e análise final. Os resultados estão apresentados em quatro categorias analíticas, sendo: "quedas recorrentes e suas repercussões no envelhecer", "limitações funcionais prévias às quedas", "expectativa de recuperação baseada na fé espiritual" e o "medo da dependência física". Percebe-se que, entre os idosos investigados, existe um processo de passividade em aceitar o envelhecer e que a queda poderá causar diminuição da capacidade funcional e da autoestima. Tornam-se necessários, portanto, programas de prevenção a quedas e incentivo ao envelhecimento ativo.

Cervical hip fracture in a Finnish population: incidence and mortality

BACKGROUND AND AIMS

Our aim was to describe the incidence of cervical hip fractures and to describe the relationships between selected background variables and mortality at 30 days, 6 months, and 3 years postoperatively.

MATERIAL AND METHODS

The basic material consisted of population-based data set of patients aged 65 years or older who had sustained a hip fracture and were treated operatively between 1999 and 2000. Out of these, we identified 266 consecutive patients with cervical hip fracture.

RESULTS

The age-adjusted incidence of cervical hip fractures in women was 1.3-fold compared to men. In age-adjusted analysis, occurrence of chronic lung disease, cardiovascular disease or 2-5 comorbidities, male gender, the need for 2-person mobility assistance, and poor ambulation postoperatively were associated with excess mortality at least at one evaluation point.

CONCLUSIONS

Only chronic lung disease and male gender were independent predictors of increased mortality at each follow-up assessment in multivariate analysis.

Quantifying the material and structural determinants of bone strength

The ability of a bone to resist fracture depends on the amount of bone present, the spatial distribution of the bone mass as cortical and trabecular bone and the intrinsic properties of the bone material. Whereas low areal bone mineral density (aBMD) predicts fractures, its sensitivity and specificity is low, as over 50% of fractures occur in persons without osteoporosis by BMD testing and most women with osteoporosis do not sustain a fracture. New non-invasive imaging techniques, including three-dimensional (3D) assessments of bone density and geometry, microarchitecture and integrated measurements of bone strength such as finite element analysis (FEA), provide estimates of bone strength that can be used to increase the sensitivity and specificity of fracture risk assessment. Initial observations have shown that these techniques provide information that will improve our understanding of the pathophysiology of skeletal fragility and suggest that these techniques are likely to have a role in the clinical management of individuals at risk for fracture.

Prediction of hip and other osteoporotic fractures from hip geometry in a large clinical cohort

SUMMARY

Incident hip fractures and non-hip osteoporotic fractures were studied in 30,953 women during mean 3.7 years of observation. Hip axis length (HAL) and strength index (SI) made a small but statistically significant contribution to hip fracture prediction that was independent of age and hip bone density.

INTRODUCTION

It is uncertain whether bone geometric measures improve fracture prediction independent of conventional areal bone mineral density (BMD).

METHODS

Women aged > or =50 years with hip dual-energy x-ray absorptiometry were identified from the regionally based database in the Province of Manitoba, Canada. Scans were reprocessed to derive parameters of hip bone geometry. Incident hip fractures (N = 270) and non-hip osteoporotic fractures (N = 1,347) were identified during mean 3.7 years of observation.

RESULTS

HAL was greater in both hip and non-hip fracture cases than in non-fracture cases, whereas cross-sectional moment of inertia, cross-sectional area, and femoral SI were all significantly less. After adjustment for total hip BMD, HAL [hazard ratio (HR) 1.22 per SD increase, 95% CI 1.07-1.38] and SI (HR 1.21 per SD decrease, 95% CI 1.07-1.37) were independent predictors of hip fractures but not of non-hip fractures. When both HAL and SI were added to a model containing age and total hip BMD, there was a small improvement in hip fracture prediction (ROC area under the curve 0.832 +/- 0.013 vs 0.823 +/- 0.013; P = 0.001).

CONCLUSIONS

HAL and SI made a small but statistically significant contribution to hip fracture prediction that was independent of age and BMD measurement.

Local topological analysis of densitometer-generated scan images of the proximal femur for differentiation between patients with hip fracture and age-matched controls

SUMMARY

We evaluate densitometer-generated scan images of the proximal femur with respect to topological properties of bone mineral distribution patterns in selected regions of interest. In a population of 100 post-menopausal women, the method has a highly discriminative potential with a performance superior to standard densitometry. Results vary with anatomical location within the proximal femur.

INTRODUCTION

The objectives of the study were to evaluate densitometer-generated scan images of the proximal femur with respect to topological properties of bone mineral distribution patterns in selected regions of interest, to test the ability for differentiation between post-menopausal women hip fracture and controls, and to compare results with standard bone densitometry.

MATERIALS AND METHODS

We used dual-energy X-ray absorptiometry (DXA) to measure the femoral bone mineral density (BMD) of 100 post-menopausal women (73.4 +/- 12.2), 50 of whom had a recent hip fracture. Local bone mineral distribution in the scanner-generated images was analyzed in the standard DXA-regions of interest (ROIs; femoral neck, the shaft, the trochanteric area; and the total hip) using an optimized, local topological parameter MF2D. Performance of topological analysis and BMD was tested by receiver-operator characteristic and discriminant analysis.

RESULTS

Area under the curve (AUC) for correct differentiation between patients with and without fractures by BMD in the different ROIs ranged from 0.64 to 0.71; AUC of regional density-pattern analysis varied between 0.79 and 0.84. Using multivariate statistical models, between 71% and 84% of patients were correctly identified as fracture/non-fracture cases by regional topological analysis, whereas BMD reached levels from 58% to 68%.

CONCLUSION

Our analysis indicates that identification of patients with hip fracture by regional evaluation of density patterns varies with anatomical location within the proximal femur. In our study population, performance of the novel parameter was superior to densitometry.

Low sit-to-stand performance is associated with low femoral neck bone mineral density in healthy women

Bone mass may be adjusted to control the strains produced by muscular activity. We assessed the relationship between maximum rising strength (MRS), a new measurement of sit-to-stand performance, and femoral neck (FN) bone mineral density (BMD), taking into account possible confounding variables. The study population consisted of 249 healthy women aged 18-76. We measured MRS with a dynamometer fixed on the ground and connected by an adjustable nonelastic cord to a padded belt. FN BMD was measured by dual X-ray absorptiometry. Women in the first quartile of FN BMD (<0.702 g/cm(2)) had significantly lower values of MRS, body weight, height, lean mass, past 5-year physical activity expenditures, blood 17 beta estradiol (E2), 25-hydroxyvitamin D (25(OH)D), dehydroepiandrosterone sulfate (DHEAS), and insulin like growth factor 1, and higher values of age and parathyroid hormone than other women. In the logistic regression model, FN BMD values in the lowest quartile were associated with age (adjusted odds ratio [OR(a)] per 10-year increase = 1.84, 95% confidence interval [95% CI] = 1.33-2.54, P < 0.001), body weight (OR(a) per 10-kg decrease = 3.67, 95% CI = 2.08-6.47, P < 0.001), MRS (OR(a) per 20-kg decrease = 1.17, 95% CI = 1.02-1.34, P = 0.03), serum DHEAS (OR(a) < 0.5 mg/ml vs > or =0.5 mg/ml = 2.83, 95% CI = 1.3-6.12, P = 0. 01), and serum E2 (OR(a) per 10-pmol/l decrease = 1.02, 95% CI = 1.01-1.03, P = 0.03). The present study suggests a significant association between low FN BMD and low sit-to-stand performance in healthy women, independent of possible confounding variables.

A new value of proximal femur geometry to evaluate hip fracture risk: true moment arm

This study was undertaken to determine the influence of proximal femur geometry on hip fracture risk independent of bone mineral density. We examined 34 hip fracture subjects (17 men, 17 women) and 36 control subjects (18 men, 18 women). The control subjects were matched with the hip fracture patients by femoral neck bone mineral density (+ or - 0.100 g/cm(2)). Hip axis length (HAL), femoral axis length (FAL), femoral neck-shaft angle (Theta angle), lateral and medial femoral cortical thickness were measured on standart pelvic radiographs. In the literature, there are conflicting views of the relationship between femur geometry and hip fracture risk which may be explained by different definitions of some parameters. We investigated the effect of a new parameter called true moment arm (TMA) on hip fracture risk. Longer TMA may be correlated to higher transmission of impact energy to the femoral neck. Thus it may be useful to define fracture prone individuals. The results of this study showed that HAL, FAL and TMA were significantly longer in the hip fracture subjects compared to the control group (p<0.001). Hip fracture patients had thinner lateral and medial femoral cortical thickness (p<0.001). Theta angle was wider in the hip fracture group than in the control group (p<0.001). In conclusion, our study showed that evaluation of TMA in addition to HAL, FAL, Theta angle, MCT and LCT can be used to determine of the fracture risk independently of BMD.

Use of DXA-based structural engineering models of the proximal femur to discriminate hip fracture

Several DXA-based structural engineering models (SEMs) of the proximal femur have been developed to estimate stress caused by sideway falls. Their usefulness in discriminating hip fracture has not yet been established and we therefore evaluated these models. The hip DXA scans of 51 postmenopausal women with hip fracture (30 femoral neck, 17 trochanteric, and 4 unspecified) and 153 age-, height-, and weight-matched controls were reanalyzed using a special version of Hologic's software that produced a pixel-by-pixel BMD map. For each map, a curved-beam, a curved composite-beam, and a finite element model were generated to calculate stress within the bone when falling sideways. An index of fracture risk (IFR) was defined over the femoral neck, trochanter, and total hip as the stress divided by the yield stress at each pixel and averaged over the regions of interest. Hip structure analysis (HSA) was also performed using Hologic APEX analysis software. Hip BMD and almost all parameters derived from HSA and SEM were discriminators of hip fracture on their own because their ORs were significantly >1. Because of the high correlation of total hip BMD to HSA and SEM-derived parameters, only the bone width discriminated hip fracture independently from total hip BMD. Judged by the area under the receiver operating characteristics curve, the trochanteric IFR derived from the finite element model was significant better than total hip BMD alone and similar to the total hip BMD plus bone width in discriminating all hip fracture and femoral neck fracture. No index was better than total hip BMD for discriminating trochanteric fractures. In conclusion, the finite element model has the potential to replace hip BMD in discriminating hip fractures.

Prediction of incident hip fracture risk by femur geometry variables measured by hip structural analysis in the study of osteoporotic fractures

The role of bone tissue's geometric distribution in hip fracture risk requires full evaluation in large population-based datasets. We tested whether section modulus, a geometric index of bending strength, predicted hip fracture better than BMD. Among 7474 women from the Study of Osteoporotic Fractures (SOF) with hip DXA scans at baseline, there were 635 incident hip fractures recorded over 13 yr. Hip structural analysis software was used to derive variables from the DXA scans at the narrow neck (NN), intertrochanter (IT), and shaft (S) regions. Associations of derived structural variables with hip fracture were assessed using Cox proportional hazard modeling. Hip fracture prediction was assessed using the C-index concordance statistic. Incident hip fracture cases had larger neck-shaft angles, larger subperiosteal and estimated endosteal diameters, greater distances from lateral cortical margin to center of mass (lateral distance), and higher estimated buckling ratios (p < 0.0001 for each). Areal BMD, cross-sectional area, cross-sectional moment of inertia, section modulus, estimated cortical thickness, and centroid position were all lower in hip fracture cases (p < 0.044). In hip fracture prediction using NN region parameters, estimated cortical thickness, areal BMD, and estimated buckling ratio were equivalent (C-index = 0.72; 95% CI, 0.70, 0.74), but section modulus performed less well (C-index = 0.61; 95% CI, 0.58, 0.63; p < 0.0001 for difference). In multivariable models combining hip structural analysis variables and age, effects of bone dimensions (i.e., lateral distance, subperiosteal diameter, and estimated endosteal width) were interchangeable, whereas age and neck-shaft angle were independent predictors. Several parsimonious multivariable models that were prognostically equivalent for the NN region were obtained combining a measure of width, a measure of mass, age, and neck-shaft angle (BMD is a ratio of mass to width in the NN region; C-index = 0.77; 95% CI, 0.75, 0.79). Trochanteric fractures were best predicted by analysis of the IT region. Because section modulus failed to predict hip fracture risk as well as areal BMD, the thinner cortices and wider bones among those who fractured may imply that simple failure in bending is not the usual event in fracture. Fracture might require initiation (e.g., by localized crushing or buckling of the lateral cortex).

The Impact of Proximal Femur Geometry on Fracture Type — A Comparison between Cervical and Trochanteric Fractures with Two Parameters

Introduction:

Only a few studies have tested the ability of proximal femur geometry parameters to discriminate between cervical hip fractures and those of the trochanter. The main objective of this study was to evaluate the geometrical differences between these two fracture types by measuring the neck shaft angle (NSA) and the femoral neck axis length (FNAL). We also compared the distributions of these parameters and the distributions of fracture type by gender.

Material and Methods:

A retrospective analysis was made in a population-based material of 428 hip fractures collected during a two-year period from 1999 to 2000 (323 women and 105 men aged 65 years or older). NSA and FNAL were manually measured from pelvic radiographs.

Results:

No significant differences in NSA or FNAL were found between cervical and trochanteric hip fractures in women or in men. Men had significantly higher NSA and FNAL than women. Age was not related to these geometrical parameters. The distributions by fracture type were similar in both genders.

Conclusions:

The different pathogenesis of cervical and trochanteric hip fractures cannot be explained by NSA or FNAL. A standardized measurement setup is needed when evaluating the role of hip geometry in fracture patients.

Effect of risedronate on hip structural geometry: a 1-year, double-blind trial in chemotherapy-induced postmenopausal women

INTRODUCTION

Chemotherapy-induced menopause is associated with bone loss. The effect on structural geometry is unknown. Our objective was to determine if oral bisphosphonate therapy could maintain or improve femoral geometry in breast cancer patients with chemotherapy-induced menopause.

METHODS

This preplanned 1 year interim, secondary analysis of the Risedronate's Effect on Bone loss in Breast CAncer Study (REBBeCA Study) examined hip structure analysis (HSA), i.e. changes in the bone cross-sectional area (bone CSA), section modulus (SM: measure of bending strength), cortical thickness (CT) and buckling ratio (BR: index of cortical bone stability), in a double-blind trial of 87 newly postmenopausal, nonmetastatic breast cancer patients, randomized to risedronate, 35 mg once weekly (RIS) versus placebo (PBO).

RESULTS

After 12 months, intertrochanteric parameters demonstrated percentage improvement (RIS vs. PBO) from baseline in bone CSA (mean+/-SD: 4.25+/-6.29 vs. 0.60+/-5.99%), SM (3.97+/-6.40 vs. 0.80+/-7.08%), and CT [5.20+/-6.98 vs. 1.13+/-6.87% (all p-values <0.05 except SM p=0,0643)]. Similar improvements were observed at the femoral shaft [bone CSA: 2.24+/-5.74 vs. -0.78+/-5.73%; SM: 1.62+/-6.23 vs. -1.39+/-7.06%; CT: 3.79+/-7.84 vs. -0.17+/-7.90% (all p-values <0.05, RIS vs. PBO, except SM p= p =0.0568)]. At both sites, the BR had significant decreases consistent with improved strength.

CONCLUSION

We conclude that RIS improves measures of hip structural geometry in women with breast cancer following chemotherapy.

Proximal femoral structure and the prediction of hip fracture in men: a large prospective study using QCT

The structure of the femoral neck contributes to hip strength, but the relationship of specific structural features of the hip to hip fracture risk is unclear. The objective of this study is to determine the contribution of structural features and volumetric density of both trabecular and cortical bone in the proximal femur to the prediction of hip fracture in older men. Baseline QCT scans of the hip were obtained in 3347 men >or=65 yr of age enrolled in the Osteoporotic Fractures in Men Study (MrOS). All men were followed prospectively for an average of 5.5 yr. Areal BMD (aBMD) by DXA was also assessed. We determined the associations between QCT-derived measures of femoral neck structure, volumetric bone density, and hip fracture risk. Forty-two men sustained incident hip fractures during follow-up: an overall rate of 2.3/1000 person-years. Multivariable analyses showed that, among the QCT-derived measures, lower percent cortical volume (hazard ratio [HR] per SD decrease: 3.2; 95% CI: 2.2-4.6), smaller minimal cross-sectional area (HR: 1.6; 95% CI: 1.2-2.1), and lower trabecular BMD (HR: 1.7; 95% CI: 1.2-2.4) were independently related to increased hip fracture risk. Femoral neck areal BMD was also strongly related to hip fracture risk (HR: 4.1; 95% CI: 2.7-6.4). In multivariable models, percent cortical volume and minimum cross-sectional area remained significant predictors of hip fracture risk after adjustment for areal BMD, but overall prediction was not improved by adding QCT parameters to DXA. Specific structural features of the proximal femur were related to an increased risk of hip fracture. Whereas overall hip fracture prediction was not improved relative to aBMD, by adding QCT parameters, these results yield useful information concerning the causation of hip fracture, the evaluation of hip fracture risk, and potential targets for therapeutic intervention.

A novel DXA-based hip failure index captures hip fragility independent of BMD

Capability of a novel dual-energy X-ray absorptiometry (DXA)-based hip failure index (HiFI) to discriminate between hip fracture cases and controls was evaluated. Given the constraints of planar DXA, the femoral neck was assumed a foam-filled ( approximately trabecular bone), thin-walled ( approximately cortical bone) sandwich structure, while HiFI estimated the critical force sufficient to buckle the wall of such a structure. Proximal femur DXA data from 1379 women aged 65yr and older, 268 with prior hip fracture were used. Comparison between standard areal bone mineral density (BMD), femur strength index (FSI), and HiFI was based on areas under receiver operatoring characteristic curves (AUC). The mean femoral neck BMD (SD) was 0.689 (0.109) g/cm(2) among the cases and 0.768 (0.119) g/cm(2) among the controls; the mean FSI 1.33 (0.36) and 1.54 (0.41), and the mean HiFI -0.28 (0.14) and -0.18 (0.15), respectively; all intergroup differences were highly significant (p<0.001). The intergroup difference for HiFI remained significant (p<0.002) after adjusting for age and BMD or FSI. The AUCs were 0.696 (95% confidence interval [CI]: 0.661-0.730) for BMD, 0.665 (0.630-0.700) for FSI, and 0.701 (0.666-0.736) for HiFI. In conclusion, HiFI may capture structural traits that account for femoral neck fragility independently of BMD or FSI. Obviously, the use of actual geometric and structural information from three-dimensional imaging of the femoral neck would help diminish the crude assumptions of the present DXA approach and reveal the true potential of the HiFI approach to gauge hip fragility and identify at-risk individuals for hip fractures.

Technology insight: noninvasive assessment of bone strength in osteoporosis

Fractures that result from osteoporosis are an enormous and growing concern for public health systems; as the population ages, the number of fractures worldwide will double or triple in the next 50 years. The ability of a bone to resist fracture depends not only on the amount of bone present, but also on the spatial distribution of the bone mass, the cortical and trabecular microarchitecture, and the intrinsic properties of the materials that comprise the bone. Although low bone mineral density is one of the strongest risk factors for fracture, a number of clinical studies have demonstrated the limitations of using measurements of areal bone mineral density by dual-energy X-ray absorptiometry to assess fracture risk and to monitor responses to therapy. As a result, new, noninvasive imaging techniques that are capable of assessing various components of bone strength are being developed. These techniques include three-dimensional assessments of bone density, geometry and microarchitecture, as well as integrated measurements of bone strength by engineering analyses. Although they show strong potential, further development and validation of these techniques is needed to define their role in the clinical management of individuals with osteoporosis.

Experimental hip fracture load can be predicted from plain radiography by combined analysis of trabecular bone structure and bone geometry

Computerized analysis of the trabecular structure was used to test whether femur failure load can be estimated from radiographs. The study showed that combined analysis of trabecular bone structure and geometry predicts in vitro failure load with similar accuracy as DXA.

INTRODUCTION

Since conventional radiography is widely available with low imaging cost, it is of considerable interest to discover how well bone mechanical competence can be determined using this technology. We tested the hypothesis that the mechanical strength of the femur can be estimated by the combined analysis of the bone trabecular structure and geometry.

METHODS

The sample consisted of 62 cadaver femurs (34 females, 28 males). After radiography and DXA, femora were mechanically tested in side impact configuration. Fracture patterns were classified as being cervical or trochanteric. Computerized image analysis was applied to obtain structure-related trabecular parameters (trabecular bone area, Euler number, homogeneity index, and trabecular main orientation), and set of geometrical variables (neck-shaft angle, medial calcar and femoral shaft cortex thicknesses, and femoral neck axis length). Multiple linear regression analysis was performed to identify the variables that best explain variation in BMD and failure load between subjects.

RESULTS

In cervical fracture cases, trabecular bone area and femoral neck axis length explained 64% of the variability in failure loads, while femoral neck BMD also explained 64%. In trochanteric fracture cases, Euler number and femoral cortex thickness explained 66% of the variability in failure load, while trochanteric BMD explained 72%.

CONCLUSIONS

Structural parameters of trabecular bone and bone geometry predict in vitro failure loads of the proximal femur with similar accuracy as DXA, when using appropriate image analysis technology.

Clinical risk factors for fracture in postmenopausal osteoporotic women: a review of the recent literature

OBJECTIVE

To review recent literature regarding relationships among age, weight or body mass index (BMI), bone mineral density (BMD), maternal history of fracture, or personal prior history of fracture and fragility fractures in women with postmenopausal osteoporosis (PMO).

DATA SOURCES

A MEDLINE database search (1995-June 30, 2007) was conducted to identify literature related to risk factors of interest for PMO-related fractures.

STUDY SELECTION AND DATA EXTRACTION

Cohort studies, case-control studies, and meta-analyses that reported fracture outcomes were included if they provided an estimate of relative risk for at least 1 of the 5 selected clinical risk factors (CRFs) and studied women with PMO or stratified risk estimates by age and sex. Of 313 identified studies that evaluated fractures as an endpoint, 245 did not report risk estimates for a CRF of interest and/or did not report data for a PMO population.

DATA SYNTHESIS

In the 68 included articles, the risks associated with the evaluated CRFs were high and significant. Prior fracture was a strong predictor of fracture and increased risk up to 18 times. Each standard deviation below the referent mean for BMD was associated with an increased fracture risk of up to 4.0 times; maternal fracture history increased risk 1.3-2.9 times. Age (per 5 year increment) increased risk by 1.2-5.0 times; low weight or BMI inconsistently showed a 0.5-3.0 times greater risk.

CONCLUSIONS

Low BMD is widely used as a diagnostic indicator for osteoporosis; however, other CRFs play an important role in determining fracture risk among women with PMO.

Survival and functional outcome according to hip fracture type: a one-year prospective cohort study in elderly women with an intertrochanteric or femoral neck fracture

We conducted a prospective study among elderly women with a first hip fracture to document survival and functional outcome and to determine whether outcomes differ by fracture type. The design was a one-year prospective cohort study in the context of standard day-to-day clinical practice. The main outcome measures were survival and functional outcome, both at hospital discharge and 1 year later. Functional outcome was assessed using the Rapid Disability Rating Scale version-2. Of the 170 women originally enrolled, 86 (51%) had an intertrochanteric and 84 (49%) a femoral neck fracture. There were no significant differences between the two groups with respect to median age (80 and 78 years, respectively), type and number of comorbidities and prefracture residence at the time of injury. At hospital discharge, intertrochanteric hip fracture patients had a higher mortality (p=0.006) and were functionally more impaired (p=0.005). One year later, mortality was still significantly higher after intertrochanteric fracture (relative risk 2.5; 95% confidence interval: 1.3 to 5.1; p=0.008), but functional outcome among surviving patients was similar in both groups. We conclude that intertrochanteric fractures are associated with increased mortality compared to femoral neck fractures. Functional outcome differs according to fracture type at hospital discharge, but these differences do not persist over time. These differences cannot be explained by differences in age or comorbidity. To address the mechanism(s) by which intertrochanteric fractures carry excess mortality compared to femoral neck fractures, future studies in hip fracture patients should include a comprehensive assessment of the degree of frailty, vitamin D status, and fall dynamics.

Noninvasive assessments of bone strength

PURPOSE OF REVIEW

Description of new noninvasive technologies or modifications of existing technologies with which individual components of bone strength and bone strength as a whole can be quantified.

RECENT FINDINGS

Although bone mineral density has served as an able surrogate for bone strength, it is clear that aspects of bone strength are either not captured or are not discernible within the measurement of bone density. New, noninvasive technologies have been developed to quantify aspects of bone strength such as biomechanical parameters based on geometry and scale and topological parameters of microarchitecture. Finite element modeling utilizes sophisticated mathematical approaches to predict the strength of the whole bone. At present, most of these technologies remain beyond the reach of clinicians, with the exception of hip structural or strength analysis.

SUMMARY

Hip strength or structural analysis is widely available because of its incorporation with dual energy X-ray absorptiometry and has been extensively used in clinical research. None of these new approaches has been shown to be superior to the measurement of bone density in the prediction of fracture risk. This fact does not diminish their potential to enhance the understanding of the pathophysiology of fracture and the mechanisms of therapeutic efficacy.

Hip structural geometry in old and old-old age: similarities and differences between men and women

INTRODUCTION

Changes in hip structure and geometry during aging contribute to decreased bone strength. Little is known, however, about these characteristics at advanced age, when fragility fractures are common. We examined hip structural geometry in men and women of old age (72-84 years) and old-old age (85-96 years) to determine (1) gender differences; (2) whether or not these differences are consistent with the increased occurrence of hip fracture in elderly women, compared to men; and (3) whether or not gender-specific changes are consistent with the increased occurrence of fragility fractures after age 80 in both men and women.

METHODS

We used Hip Structure Analysis (HSA) software to analyze bone densitometry scans from 916 community-dwelling men and women aged 72-96 years. We examined gender differences in hip geometry by age group (72-74, 75-79, 80-84, and >or=85 years) and between gender-specific age groups using multivariable linear regression.

RESULTS

At the femoral narrow neck, there was no gender difference at age 72-74 in bone mineral density (BMD), cortical thickness (CT), and buckling ratio (BR). In contrast, at age 85 or older women had 13% less BMD and CT than men and 8% higher BR. At the intertrochanteric region, women >or=85 years had 25-31% less BMD, cross-sectional bone area (CSA), and CT than men of comparable age, and 38% higher BR. These gender differences were approximately 10-20% greater than those between men and women in their 70s. In gender-specific comparisons, women showed increasing change in structural geometry with increasing age. At both narrow neck and trochanteric regions, women >or=85 years had nearly 35% higher BR, 15% less BMD and CT, and 10% less CSA than women aged 72-74 years. At the narrow neck, they also had 6% greater outer diameter than the youngest women and 8% lower section modulus (Z), an index of bending strength. In contrast, men showed significant age differences only at the narrow neck region, and only at 85 years or older, including 22% higher BR, 10% less BMD and CT, and 5% greater outer diameter, compared to men in their early 70s. Unlike women, men showed no age-associated decline in section modulus.

CONCLUSIONS

Gender differences in hip geometry consistent with increased fragility and fracture risk in elderly women, compared to men, continue into old-old age. Both men and women 85 or older show the most unfavorable features, suggesting a structural basis for the increased occurrence of hip fracture in both sexes at advanced age.

Bone density and geometry in assessing hip fracture risk in post-menopausal women

We used femoral neck structural parameters (FNSPs), calculated from bone mineral density (BMD) measurements of the femoral neck by dual X-ray absorptiometry, to discriminate osteoporotic fractures of the proximal femur in post-menopausal women. We compared 1646 women without fracture and 429 women with hip fractures, including 273 with femoral neck (FN) and 156 with trochanter (TR) fractures. The association between the studied parameters and the fractures was modelled using multiple logistic regression, and included age, height and weight. Fracture-predicted probability (FPP) was also calculated for each predictor tested. Receiver operating characteristic (ROC) curve areas with their standard errors (SEs) were calculated for the fracture status, having the calculated FPP as a test variable. The areas were compared by the Hanley-McNeil test. Hip fracture had lower BMD, cross-sectional area (CSA), section modulus (SM) and cortical thickness (CT), and higher buckling ratio (BR), than controls. To the same extent as FN BMD, BR best predicted the risk for each fracture, showing ROC curve areas of 0.809 (SE 0.011) for hip fracture, 0.789 (SE 0.014) for FN fracture, and 0.848 (SE 0.016) for TR fracture. The association of BR with fracture risk did not differ from that of FN BMD, which has a ROC curve area of 0.801 (SE 0.011) for hip fracture, 0.778 (SE 0.014) for FN fracture, and 0.852 (SE 0.016) for TR fracture. Both FN BMD and BR predicted TR fracture significantly better than they did FN fracture. FNSPs, although interesting in understanding the biomechanics of bone fragility, do not appear to add diagnostic value to the simple measurement of BMD.

Proximal hip geometry is linked to several chromosomal regions: genome-wide linkage results from the Framingham Osteoporosis Study

INTRODUCTION

Femoral geometry contributes to bone strength and predicts hip fracture risk. The purpose of this study was to evaluate heritability (h(2)) of geometric indices of the proximal hip and to perform whole-genome linkage analyses of these traits, adjusted for body size.

METHODS

DXA scans of the proximal femur from 1473 members of 323 pedigrees (age range 31-96 years) from the population-based Framingham Osteoporosis Study were obtained. Using the hip structural analysis program, we measured femoral neck length (FNL, cm) and neck-shaft angle (NSA); subperiosteal width (WID, cm), cross-sectional area (CSA, cm(2)); and section modulus (Z, cm(3)) at the narrowest section of the neck (NN), intertrochanteric (IT) and femoral shaft (S) regions. Linkage analyses were performed for the above indices with a set of 636 markers using variance components maximum likelihood method.

RESULTS

Substantial genetic influences were found for all geometric phenotypes, with h(2) values between 0.28 (NSA) and 0.70 (IT_WID). Adjustment for height and BMI did not alter h(2) of NSA and FNL but decreased h(2) of the cross-sectional indices. We obtained substantial linkage (multipoint LOD >3.0) for S_Z at 2p21 and 21q11 and S_WID at Xq25-q26. Inclusion of height and BMI as covariates resulted in much lower LOD scores for S_Z, whereas linkage signals for S_Z at 4q25, S_CSA at 4q32 and S_CSA and S_Z at 15q21 increased after the adjustment. Linkage of FNL at 1q and 13q, NSA at 2q and NN_WID at 16q did not change after the adjustment.

CONCLUSION

Suggestive linkages of bone geometric indices were found at 1q, 2p, 4q, 13q, 15q and Xq. The identification of significant linkage regions after adjustment for BMI and height may point to QTLs influencing femoral bone geometry independent of body size.

Biomechanical indices of the femoral neck estimated from the standard DXA output: age- and sex-related differences

We explored the feasibility of using routine dual-energy X-ray absorptiometry (DXA) to estimate several parameters of femoral neck geometry related to bone strength and to analyze their changes with age. Bone mineral density (BMD) was measured in 871 control men and women and in 19 women with hip fracture. Volumetric BMD (volBMD) and geometrical parameters were estimated from the DXA output with previously published formulas. In young subjects, areal BMD was higher in men than in women, but volBMD was similar in both sexes. However, it showed a more rapid decline with age in women. The femoral neck width and cortical thickness were also higher in young men than in women. Neck width increased and cortical thickness decreased with age in both sexes. The buckling ratio, an index of local cortical instability, increased more rapidly in women. The compressive strength decreased progressively with age in women, whereas it did not change in men after 50 yr of age. Compressive strength and the buckling ratio showed the largest difference between control and hip fracture women (Z=-1.3). This cross-sectional study suggests that data available in the standard DXA output can easily be used to estimate several geometrical parameters of the femoral neck that evolve in a sex- and age-specific manner. Further studies are needed to elucidate whether they add significant information to BMD in the prediction of fracture risk.

Sex hormone status may modulate rate of expansion of proximal femur diameter in older women alongside other skeletal regulators

CONTEXT

Little is known of associations between hip geometry and skeletal regulators. This is important because geometry is a determinant of both hip function and resistance to fracture.

OBJECTIVE

We aimed to determine the effects of sex hormone status and other candidate regulators on hip geometry and strength.

SUBJECTS AND METHODS

A random sample of 351 women aged 67-79 had two to four hip dual-energy x-ray absorptiometry scans performed over 8 yr of follow-up. Hip structural analysis software was used to measure subperiosteal diameter (PD) and the distance from the center of mass to the lateral cortical margin (d-lat) on three 5-mm-thick cross-sectional regions: narrow neck, intertrochanter, and shaft. Section modulus (Z), bone mineral density (grams per centimeter squared), and an index of bone mineral content (cross-sectional area) were calculated as estimators of bone strength. Serum analytes measured at baseline included SHBG, estradiol, PTH, creatinine, albumin, vitamin D metabolites, and glutamate- and gamma-carboxyglutamate-osteocalcin (OC). A linear mixed model was used to model associations with predictor variables, including testing whether the predictors significantly modified the effect of aging.

RESULTS

Aging was associated with increasing PD and d-lat, and higher baseline SHBG significantly modified this effect, in the case of PD, increasing the rates of change at the narrow neck region by 19% for SHBG level 2 sd higher than population mean (P = 0.026). Higher baseline creatinine was independently associated with faster increases in PD and d-lat with aging (P < 0.041). Z declined faster with aging if baseline PTH was higher, and higher albumin had a contrary effect. Z was positively associated with free estradiol and inversely associated with SHBG and glutamate-OC.

CONCLUSION

These results show large effects of SHBG on the regulation of proximal femur expansion and bending resistance, probably acting as a surrogate for low bioavailable estrogen. Potentially important effects for fracture resistance in old age were also revealed for PTH, markers related to renal function and the nutritional markers albumin and undercarboxylated OC.

Evolution of Brazilian elderly with hip fracture secondary to a fall

OBJECTIVE

To contribute to fall prevention by studying the epidemiological profile, mortality, and functional evolution of elderly persons with hip fracture, in Brazil, in the year following a fracture.

METHOD

Fifty-six elderly patients aged 60 years and over with hip fracture secondary to a fall and admitted in 2000 were included. In addition to the medical record data, patients or their guardians filled a form providing information regarding personal data, history of fall and fracture, physical evaluation, and ability to perform basic and instrumental activities of daily living prior to and 1 year after their fracture, using Katz's Index and Lawton's Index, respectively.

RESULTS

Fractures were more common among Caucasian widowed women, and most falls occurred at home. General mortality within 1 year after the occurrence of fracture was 30.35% and was associated with sex and age. There was an increase in the inability to walk and in the use of a supporting device. A significant reduction in the functional ability to perform basic and instrumental activities of daily living was found.

CONCLUSION

The evolution of hip fracture in the year following it is related to high mortality and to a decrease in functional ability, with age and male sex being the factors associated with a worse prognosis, emphasizing the need for special follow-up care of these groups during the immediate and late postoperative periods.

Evaluation of cortical bone by peripheral quantitative computed tomography in continuous ambulatory peritoneal dialysis patients

Several studies have suggested an increased prevalence of osteopenia in dialysis. Peripheral quantitative computed tomography (pQCT) is a new technique that allows the noninvasive evaluation of trabecular and cortical bone separately. The aim of the study was: (1) to evaluate cortical bone by pQCT in continuous ambulatory peritoneal dialysis (CAPD) patients and compare the data with that obtained in healthy controls; and (2) to correlate cortical bone parameters with bone mineral density (BMD) of the lumbar spine and femoral neck and total bone mineral content (TBMC). Cortical bone parameters were obtained in 22 CAPD patients and 27 healthy individuals at the distal radius using a Stratec XCT 960 pQCT machine. In the dialysis patients, we also determined BMD and TBMC by bone densitometry. Dialysis patients, compared with controls, showed a significant reduction in volumetric cortical BMD (VcBMD) (p = 0.04) and cortical thickness (cThk) (p < 0.0001) with a significant increase in radial total cross-sectional area (TA) (p = 0.006), endosteal circumference (p < 0.0001), and buckling ratio (p < 0.0001). In CAPD patients, total time on dialysis correlated negatively with radial total BMD (p < 0.01) and VcBMD (p < 0.01). Age correlated positively with TA (p < 0.01), endosteal (p < 0.01), and periosteal circumferences (p < 0.01). Serum intact parathyroid hormone (PTH) levels correlated positively with endosteal (p = 0.04) and periosteal perimeter (p = 0.01). Total alkaline phosphatase correlated negatively with VcBMD (p < 0.01), and positively with endosteal perimeter (p = 0.02). Total bone mineral content correlated significantly with radial cortical content (p < 0.001), cross-sectional cortical area (cA; p < 0.001), and cThk (p < 0.01) but not with total radial BMD, VcBMD, or buckling ratio. No correlations were found between radial cortical parameters and BMD measured at the lumbar spine or femoral neck. We conclude that dialysis patients show cortical osteopenia with marked cortical thinning partially mediated by PTH action on bone. Total bone mineral content correlated with various radial cortical parameters (content, area, and thickness) but not with others. No correlations were found between cortical bone parameters measured at the peripheral skeleton with areal bone density measured at the axial skeleton. These findings suggest that pQCT may be a new tool in the assessment of bone fragility in dialysis patients.

Prediction and discrimination of osteoporotic hip fracture in postmenopausal women

Osteoporotic hip fractures increase dramatically with age and are responsible for considerable morbidity and mortality. Several treatments to prevent the occurrence of hip fracture have been validated in large randomized trials and the current challenge is to improve the identification of individuals at high risk of fracture who would benefit from therapeutic or preventive intervention. We have performed an exhaustive literature review on hip fracture predictors, focusing primarily on clinical risk factors, dual X-ray absorptiometry (DXA), quantitative ultrasound, and bone markers. This review is based on original articles and meta-analyses. We have selected studies that aim both to predict the risk of hip fracture and to discriminate individuals with or without fracture. We have included only postmenopausal women in our review. For studies involving both men and women, only results concerning women have been considered. Regarding clinical factors, only prospective studies have been taken into account. Predictive factors have been used as stand-alone tools to predict hip fracture or sequentially through successive selection processes or by combination into risk scores. There is still much debate as to whether or not the combination of these various parameters, as risk scores or as sequential or concurrent combinations, could help to better predict hip fracture. There are conflicting results on whether or not such combinations provide improvement over each method alone. Sequential combination of bone mineral density and ultrasound parameters might be cost-effective compared with DXA alone, because of fewer bone mineral density measurements. However, use of multiple techniques may increase costs. One problem that precludes comparison of most published studies is that they use either relative risk, or absolute risk, or sensitivity and specificity. The absolute risk of individuals given their risk factors and bone assessment results would be a more appropriate model for decision-making than relative risk. Currently, a group appointed by the World Health Organization and lead by Professor John Kanis is working on such a model. It will therefore be possible to further assess the best choice of threshold to optimize the number of women needed to screen for each country and each treatment.

Bone geometry and skeletal fragility

Although low bone mineral density is among the strongest risk factors for fracture, a number of clinical studies have demonstrated the limitations of bone mineral density measurements in assessing fracture risk and monitoring the response to therapy. These observations have brought renewed attention to the broader array of factors that influence skeletal fragility, including bone size, shape, and microarchitecture. This article reviews the relationship between bone geometry and skeletal fragility, focusing on the impact of bone geometry on bone strength and fracture risk. It also reviews recent data on the effect of osteoporosis therapies on femoral geometry. It is clear that characteristics of a bone's size and shape strongly influence its biomechanical strength, but there is no consensus as to the geometric parameters that improve prediction of fracture risk. Recent data from hip structure analysis indicate that antiresorptive and anticatabolic treatments alter femoral geometry, but this observation depends on several assumptions that have not been tested in subjects treated with osteoporosis therapies. Current knowledge is limited, in part, by the predominant use of two-dimensional techniques to assess bone geometry. Additional studies that incorporate three-dimensional imaging are needed to better define the relationship between bone geometry and skeletal fragility, and to establish the clinical utility of bone geometry measurements.

Association of geometric factors and failure load level with the distribution of cervical vs. trochanteric hip fractures

We experimentally studied the distribution of hip fracture types at different structural mechanical strength. Femoral neck fractures were dominant at the lowest structural strength levels, whereas trochanteric fractures were more common at high failure loads. The best predictor of fracture type across all failure loads and in both sexes was the neck-shaft angle.

INTRODUCTION

Bone geometry has been shown to be a potential risk factor for osteoporotic fractures. Risk factors have been shown to differ between cervical and trochanteric hip fractures. However, the determinants of cervical and trochanteric fractures at different levels of structural mechanical strength are currently unknown. In addition, it is not known if the distribution of fracture types differs between sexes. The aim of this experimental study on excised femora was to investigate whether there exist differences in the distribution of cervical and trochanteric fractures between different structural mechanical strength levels and different sexes and to identify the geometric determinants that predict a fracture type.

MATERIALS AND METHODS

The sample was comprised of 140 cadavers (77 females: mean age, 81.7 years; 63 males: mean age, 79.1 years) from whom the left femora were excised for analysis. The bones were radiographed, and geometrical parameters were determined from the digitized X-rays. The femora were mechanically tested in a side impact configuration, simulating a sideways fall. After the mechanical test, the fracture patterns were classified into cervical and trochanteric.

RESULTS

The overall proportion of cervical fractures was higher in females (74%) than in males (49%) (p = 0.002). The fracture type distribution differed significantly across load quartiles in females (p = 0.025), but not in males (p = 0.205). At the lowest load quartiles, 94.7% of fractures in female and 62.5% in males were femoral neck fractures. At the highest quartiles, in contrast, only 52.6% of fractures in females and 33.3% in males were cervical fractures. Among geometric variables, the neck-shaft angle was the best predictor of fracture type, with higher values in subjects with cervical fractures. This finding was made in females (p < 0.001) and males (p = 0.02) and was consistent across all failure load quartiles.

CONCLUSIONS

Femoral neck fractures predominate at the lowest structural mechanical strength levels, whereas trochanteric fractures are more common at high failure loads. Females are more susceptible to femoral neck fractures than males. The best predictor of fracture type across all structural strength levels and both sexes was the neck-shaft angle.

Low width of tubular bones is associated with increased risk of fragility fracture in elderly men--the MINOS study

The risk of fragility fractures in elderly men is only partly explained by areal bone mineral density (aBMD) measured by dual X-ray absorptiometry (DXA). Several studies suggest the importance of bone morphology for the risk of fracture. The aim of this study was to assess the value of bone size and estimated structural parameters for the prediction of incident fractures in a large cohort of men. This study was made in 759 men aged 50-85 from the MINOS cohort. During a 90-month follow-up, 74 men sustained incident vertebral and peripheral fractures. Areal BMD was measured by DXA at femoral neck, distal radius and distal ulna. Estimates of structural bone parameters and volumetric BMD (vBMD) were derived from aBMD measured by DXA. Given the limited number of fractures, the predictive value of investigated parameters was assessed for peripheral and vertebral fractures jointly by using logistic regression. Men who sustained the fractures had, at baseline, lower aBMD (3.5-6.5%), lower bone mineral content (BMC 5.4-8.7%) and lower cortical thickness (3.5-6.9%) compared with the men without fracture. At all the three skeletal sites, aBMD, BMC, width, cortical area and thickness, cross-sectional moment of inertia (CSMI), and section modulus predicted incident fractures (O.R. = 1.28-1.92 per 1 SD decrease, P < 0.05-0.0001). Fracture risk was weakly associated with vBMD for ulna (O.R. = 1.25 per 1 SD decrease, P < 0.05) but not for femoral neck or radius. After adjustment for aBMD, bone width remained a significant predictor of fractures (O.R. = 1.37-1.48 per 1 SD decrease, P < 0.02-0.01). Men with osteopenia (BMD T score < -1) and low bone width (T score < -1) had the fracture incidence similar to that observed in men with BMD T score < -2. Bone width and aBMD of the femoral neck and radius were predictive of fractures in 49 men with the incident peripheral fractures, whereas their O.R. did not attain the level of statistical significance in 25 men with the incident vertebral fractures. Men, who had both low aBMD and low CSMI ( both T scores < -1), had the fracture risk 3.8 to 4.2 higher than the reference group (both T scores >or= -1). Men, who had both low aBMD and low section modulus (both T scores < -1), had the fracture risk 2.1 to 4.1 higher than the reference group (both T scores >or= -1). In conclusion, men who sustained a fragility fracture during a 90-month follow-up had, at baseline, lower BMC because they had narrower bones but not necessarily less dense. In elderly men, small bone width, low BMC and poor resistance to bending may increase bone fragility. Low bone width seems to be associated with an increased fracture risk in elderly men regardless of aBMD.