Differences in proximal femur geometry distinguish vertebral from femoral neck fractures in osteoporotic women

Distinctive Geometrical Traits of Proximal Femur Fractures-Original Article and Review of Literature

Background and Objectives: The incidence of proximal femoral fractures is escalating rapidly, generating a significant challenge for healthcare systems globally and, carrying serious social and economic implications. The primarily object of this study was to discover potential distinguishing factors between fractures occurring in the femoral neck and trochanteric region. Materials and Methods: We performed a prospective cohort study of the radiographic images of 70 people over 65 years of age who were admitted to the orthopedic department with hip fracture and who fulfilled our eligibility criteria. Neck Length (NL), Offset Lenth (OL), Hip Axis Length (HAL), Neck Shaft Angle (NSA), Wiberg Angle (WA), Acetabular Angle (AA), Femoral Neck Diameter (FND), Femoral Head Diameter (FHD), Femoral Shaft Diameter (FSD), Femoral Canal Diameter (FCD) and Tonnis classification were recorded. For the comparison of the categorical variables, Pearson's χ2 criterion was used, while Student's t-test was applied for the comparison of means of quantitative variables across fracture types. Results: There were no statistically significant variances observed while comparing the selected geometric parameters of the proximal femur with the type of fracture. This finding was reaffirmed in relation to age, gender, and Tonnis classification. However, a moderate correlation was noted, revealing comparatively reduced values of HAL, FHD, and FND in women as opposed to men. Conclusions: The inability of our research to establish the differentiative geometric factors between femoral neck and trochanteric fractures underscores the need for further investigations, which would take into consideration the intrinsic characteristics of the proximal femur.

Relationship between site-specific bone mineral density in the proximal femur and instability of proximal femoral fractures: A retrospective study

BACKGROUND

Proximal femoral fractures can occur in patients with osteoporosis. However, the relationship between bone mineral density (BMD) of the proximal femur and fracture type and instability remains unclear. This study aimed to determine whether there is a relationship between the site-specific BMD of the proximal femur and the instability of proximal femoral fracture.

HYPOTHESIS

The instability of proximal femoral fractures is related to the site-specific BMD of the proximal femur.

PATIENTS AND METHODS

Using dual-energy X-ray absorptiometry (DEXA), the BMD on the non-fractured side was retrospectively examined in 252 women who underwent surgery for proximal femoral fracture at our hospital. The BMD was measured at three sites: the femoral neck (neck), trochanter (trochanter), and intertrochanteric region (inter). The BMD at several sites was compared between the femoral neck and trochanteric fractures. Femoral neck fractures were classified into the displaced and non-displaced types, and trochanteric fractures were classified into stable and unstable types. A comparative analysis was conducted for each proximal femur site and fracture type.

RESULTS

Both total and site-specific BMDs were lower in trochanteric fractures than in femoral neck fractures. No difference was observed between BMD and displaced or non-displaced femoral neck fractures. However, the BMD of the intertrochanteric region was lower in unstable trochanteric fractures (0.57±0.12g/cm2) than in stable trochanteric fractures (0.61±0.11g/cm2) [p<0.05].

DISCUSSION

Several factors, including the patient's age and the bone component of each region, may influence the lower BMD in trochanteric fractures. In trochanteric fractures, the site-specific BMD of the proximal femur may predict the type of fracture and the degree of instability, especially in those with low BMD at the intertrochanteric site. The study findings suggest that a decrease in the BMD of the intertrochanteric region of femoral trochanteric fractures, which is thought to be involved in instability, is associated with fracture type instability.

LEVEL OF EVIDENCE

III, retrospective study.

Site-Specific Differences in Bone Mineral Density of Proximal Femur Correlate with the Type of Hip Fracture

The aim of this study was to investigate whether site-specific differences in bone mineral density (BMD) of proximal femur correlate with the type of hip fracture using quantitative computed tomography. Femoral neck (FN) fractures were classified as nondisplaced or displaced subtypes. Intertrochanteric (IT) fractures were classified as A1, A2, or A3. The severe hip fractures were identified as displaced FN fractures or unstable IT fractures (A2 and A3). In total, 404 FN fractures (89 nondisplaced and 317 displaced) and 189 IT fractures (76 A1, 90 A2, and 23 A3) were enrolled. Areal BMD (aBMD) and volumetric BMD (vBMD) were measured in the regions of total hip (TH), trochanter (TR), FN, and IT of the contralateral unfractured femur. IT fractures exhibited lower BMD than FN fractures (all p ≤ 0.01). However, unstable IT fractures had higher BMD compared with stable ones (p < 0.01). After adjusting for covariates, higher BMD in TH and IT were associated with IT A2 (A1 vs. A2: odds ratios (ORs) from 1.47 to 1.69, all p < 0.01). Low bone measurements were risk factors for stable IT fractures (IT A1 vs. FN fracture subtypes: ORs from 0.40 to 0.65, all p < 0.01). There are substantial site-specific differences in BMD between IT fractures A1 and displaced FN fractures. Higher bone density was associated with unstable IT fracture when compared with stable ones. The understanding of biomechanics of various fracture types could help to improve the clinical management of these patients.

Clinical prediction model for postoperative ambulatory ability outcomes in patients with trochanteric fractures

INTRODUCTION

Regaining independent ambulatory ability is one of the primary goals of treatment in patients with trochanteric fractures. This study aimed to develop and evaluate the discriminative accuracy of a clinical prediction model for ambulatory ability outcomes 3 months after surgery for trochanteric fractures.

METHODS

This retrospective cohort study included 346 patients treated with intramedullary nailing for trochanteric fractures who had independent ambulatory ability before their injury. Multiple regression models with preoperative and postoperative factors were used to predict ambulatory ability outcomes at 3 months. A clinical prediction model (CPM) was created based on a decision tree developed using a chi-square automatic interaction detector technique.

RESULTS

Three months after surgery, 263 (76.0%) and 83 (24.0%) patients regained and lost independent ambulatory ability, respectively. Univariate analysis showed that the Barthel index (BI) total score at 2 weeks predicted the ambulatory ability outcome at 3 months with good discriminative accuracy (area under the receiver operating characteristic curve [AUROC]: 0.819; 95% confidence interval [CI]: [0.769, 0.868], cut-off value: 22.5; sensitivity: 69.5%; specificity: 82.3%). Multiple logistic regression analysis showed that preoperative factors (residence before injury, diagnosis of dementia, and serum albumin at admission) and postoperative factors (BI total score at 2 weeks) predicted ambulatory ability outcomes at 3 months (AUROC: 0.710; 95%CI: [0.636, 0.783]; sensitivity: 91.3%; specificity: 41.8%). The CPM with the BI total score at 2 weeks (≤10; 10<, ≤50; >50 points) and dementia status (present; absent) had a moderate discriminative accuracy (AUROC: 0.676; 95%CI: [0.600, 0.752]; sensitivity: 94.7%; specificity: 40.5%).

CONCLUSIONS

We developed a CPM with moderate accuracy to predict ambulatory ability outcomes in patients 3 months after surgery for trochanteric fractures. Our results demonstrate the importance of the BI score measured soon after surgery and dementia status for the prediction of postoperative ambulation.

Differences in Bone Mineral Density and Hip Geometry in Trochanteric and Cervical Hip Fractures in Elderly Chinese Patients

OBJECTIVE

To assess the differences in bone mineral density (BMD) and hip geometry in trochanteric and cervical hip fractures in elderly Chinese patients.

METHODS

A consecutive series of 196 hip fracture patients aged over 50 years was recruited from November 2013 to October 2015, including 109 cases of cervical fractures (36 males and 73 females) and 87 cases of trochanteric fractures (34 males and 53 females). All patients were evaluated through dual-energy X-ray absorptiometry, and baseline characteristics, BMD and structural parameters were collected and reviewed.

RESULTS

There were statistically significant differences in age, height, and body mass index between patients with each type of fracture, and patients with trochanteric fractures were older than those with cervical fractures, especially in women. The BMD in trochanteric fractures was markedly lower than in cervical fractures in all five sites of the hip by an approximate reduction of 10%, in both men and women. The cross-sectional area, cross-sectional moment of inertia, and the cortical thickness in the cervical fracture group were significantly higher than in the trochanteric fracture group. However, the buckling ratio of both the femoral neck and trochanteric region were significantly lower in the cervical fracture group. Age (/10 years), cross-sectional moment of inertia in femoral neck and buckling ratio in trochanteric region were significant risk factors for trochanteric fractures compared with cervical fractures.

CONCLUSIONS

Compared with cervical hip fractures, patients with trochanteric fractures were older, had a lower BMD, and had less bone mechanical strength, especially in female patients. Age, femoral neck cross-sectional moment of inertia (FNCSMI), and trochanteric region buckling ratio (ITBR) were stronger risk factors for trochanteric hip fractures than for cervical fractures.

Definition of a Novel Proximal Femur Classification in the Sagittal Plane According to the Femur Morphometric Analysis

BACKGROUND

Studies on prosthesis positioning and implant design in total hip arthroplasty (THA) have generally focused on the anatomy of the proximal femur in the coronal plane. The aim of this study was to investigate the proximal femur morphology in the sagittal plane to provide better positioning of the femoral component in THA and contribute to the determination of proximal femur morphology through possible outcomes that can be shown also by considering the sagittal plane in the selection and design of the femoral component.

METHODS

Computerized tomography scans were obtained from 270 femoral bones belonging to adult skeletons, followed by 3D reconstruction using Leonardo Dr/Dsa Va30a software (Siemens, Erlangen, Germany) and measurements. Canal widths were measured in the coronal and sagittal planes at the lesser trochanter (LT) level, at 20 millimeters proximal to the LT(LT+20) and at various levels distal to the lesser trochanter in 25 mm jumps up to 200 mm from the lesser trochanter.

RESULTS

The average width was wider at the level of the lesser trochanter and all points distal to it in the sagittal plane compared to the coronal plane except LT-200 mm. At each levels from LT-25 to LT-175, the differences were statistically significant (P < .05). The ratio of the femoral width at the lesser trochanter level to the width 50 mm distal to the LT was stated as the most prevalent one, and a novel classification in the sagittal plane was developed in accordance with these findings.

CONCLUSION

A novel and simple classification in the sagittal plane was developed based on the findings of this study, and this classification may improve the accuracy, validity, and reliability of femoral stem fixation in total hip arthroplasty.

The influence of acetabular morphology on prediction of proximal femur fractures types in an elderly population

INTRODUCTION

The role of proximal femur morphology to the development of certain proximal femur fracture types both femoral neck and trochanteric fractures has been observed. However, the relavance of acetabular morphology to the development of proximal femur fractures is not extensively questioned. Therefore the aim of the study was to determine whether there is a correlation between acetabular morphology and pathogenesis of 2 different hip fracture types after low energy trauma.

METHODS

This retrospective study includes 60 cases (41 women, 19 men) with a proximal femoral fracture after a low energy trauma between July 2012 and December 2014. Acetabular depth and acetabular index were measured on pelvic radiographs. Neck shaft angle, hip axis length and cortical index were measured on pelvic computed tomography scans. All measurements were performed on the contralateral hip.

RESULTS

Mean age was 77.56 ± 8.99 years (range 61-92 years). No statistically significant difference was found with regard to neck shaft angle, acetabular depth or cortical index measurements between patients with femoral neck fracture and patients with trochanteric femoral fractures (p>0.05). Acetabular index measurement was higher (p = 0.001) and hip axis length measurement was lower (p = 0.001) in trochanteric fracture group as compared to femoral neck fracture.

CONCLUSIONS

The rate of trochanteric femur fractures is higher in patients with high acetabular index, whereas the rate of femoral neck fractures is higher in patients with increased hip axis length.

Cortical thickness in the intertrochanteric region may be relevant to hip fracture type

Background

This study assessed the differences in femoral geometry and bone mineral density between femoral neck fragility fractures and trochanteric fractures.

Methods

One hundred and seventeen patients were divided into femoral neck and trochanteric fracture groups. There were 69 patients with femoral neck fractures, 20 men and 49 women with an average age of 75.1 ± 9.6 years and an average body mass index (BMI) value of 21.6 ± 4.1 kg/m². The trochanteric group consisted of 48 patients, 16 men and 32 women with an average age of 78.1 ± 9.1 years and an average BMI value of 21.5 ± 4.3 kg/m². All patients underwent dual-energy X-ray absorptiometry (DXA) of the contralateral hip; hip structural analysis (HSA) software was used to analyze the femoral geometry parameters, including hip axis length (HAL), neck-shaft angle (NSA), cross-sectional area (CSA), the cross-sectional moment of inertia (CSMI), the buckling ratio (BR), and cortical thickness.

Results

The cortical thickness in the intertrochanteric region was reduced in the trochanteric fractures group compared to the femoral neck fracture group (P < 0.05). There were no statistically significant differences (P > 0.05) in gender, age, height, weight, or BMI between the two groups. In addition, no statistically significant differences (P > 0.05) were found in the CSA, CSMI, or BR of the femoral neck or the intertrochanteric region between the two groups. There were no statistically significant differences (P > 0.05) in femoral neck cortical thickness between the two groups.

Conclusions

Cortical thickness thinning in the intertrochanteric region may be one of the relevant factors causing different types of hip fractures, especially in elderly patients.

Does serum calcium relate to different types of hip fracture? A retrospective study

PURPOSE

To investigate the potential correlation between two different types of hip fractures and serum calcium levels.

METHODS

We consecutively studied 101 cases of femoral neck fracture and 95 cases of femoral inter- trochanteric fracture between January 2011 and December 2013. Fasting blood samples were taken and serum calcium measurements were performed respectively in three periods: the time of admission, postoperation, and discharge. Creatinine, alkaline phosphatase and albumin were also analyzed.

RESULTS

Considering the levels of serum calcium between two groups at the time of admission, post- operation and discharge, there was significant difference at admission and discharge (p <0.05), while there was no significant difference at the time of postoperation (p > 0.05). The magnitude of serum calcium fluctuation was larger in femoral neck group than femoral intertrochanteric group. Concerning alkaline phosphatase and albumin levels at admission, there was no significant difference between two groups (p > 0.05).

CONCLUSION

The capability of reservation and restoration of serum calcium in patients with femoral neck fracture is better than that in patients with femoral intertrochanteric fracture. A low serum calcium level may be susceptible to femoral intertrochanteric fracture.

Osteoporosis Imaging in the Geriatric Patient

Given the expected rapid growth of the geriatric world population (=individuals aged >65 years) to 1.3 billion by 2050, age-related diseases such as osteoporosis and its sequelae, osteoporotic fractures, are on the rise. Areal bone mineral density (aBMD) by dual-energy X-ray absorptiometry (DXA) is the current gold standard to diagnose osteoporosis, to assess osteoporotic fracture risk, and to monitor treatment-induced BMD changes. However, most fragility fractures occur in patients with normal or osteopenic aBMD, indicating that factors beyond BMD impact bone strength. Recent developments in DXA technology such as TBS, VFA, and hip geometry analysis are now available to assess some of these non-BMD parameters from the DXA image. This review will discuss the use of DXA and DXA-assisted technologies and their respective advantages and disadvantages. Special attention is given to if and how each method is indicated in the geriatric population, and the latest ISCD 2015 guidelines have been incorporated.

Influence of bone mineral density and hip geometry on the different types of hip fracture

The aim of this study was to assess the influence of bone mineral density and hip geometry on the fragility fracture of femoral neck and trochanteric region. There were 95 menopausal females of age ≥ 50 years with fragility fracture of hip, including 55 cases of femoral neck fracture and 40 cases of trochanteric fracture. Another 63 non-fractured females with normal bone mineral density (BMD) were chosen as control. BMD, hip axis length, neck-shaft angle and structural parameters including cross surface area, cortical thickness and buckling ratio were detected and compared. Compared with control group, the patients with femoral neck fracture or trochanteric fractures had significantly lower BMD of femoral neck, as well as lower cross surface area and cortical thickness and higher buckling ratio in femoral neck and trochanteric region. There were no significant differences of BMD and structural parameters in the femoral neck fracture group and intertrochanteric fracture group. Hip axis length and neck-shaft angle were not significantly different among three groups. The significant changes of BMD and proximal femur geometry were present in the fragility fracture of femoral neck and trochanteric region. The different types of hip fractures cannot be explained by these changes.

Fracture Risk Prediction by Non-BMD DXA Measures: the 2015 ISCD Official Positions Part 1: Hip Geometry

Bone mineral density (BMD) measured by dual-energy X-ray absorptiometry is the current imaging procedure of choice to assess fracture risk. However, BMD is only one of the factors that explain bone strength or resistance to fracture. Other factors include bone microarchitecture and macroarchitecture. We now have the ability to assess some of these non-BMD parameters from a dual-energy X-ray absorptiometry image. Available measurements include various measurements of hip geometry including hip structural analysis, hip axis length, and neck-shaft angle. At the 2015 Position Development Conference, the International Society of Clinical Densitometry established official positions for the clinical utility of measurements of hip geometry. We present the official positions approved by an expert panel after careful review of the recommendations and evidence prepared by an independent task force. Each question addressed by the task force is presented followed by the official position with the associated medical evidence and rationale.

The impact of adding weight-bearing exercise versus nonweight bearing programs to the medical treatment of elderly patients with osteoporosis

BACKGROUND

Osteoporosis is a major public health problem affecting the elderly population, particularly women. The objective of the study was to evaluate the effects of adding weight-bearing exercise as opposed to nonweight-bearing programs to the medical treatment of bone mineral density (BMD) and health-related quality of life (HRQoL) of elderly patients with osteoporosis.

MATERIALS AND METHODS

Participating in the study were 40 elderly osteoporotic patients (27 females and 13 males), with ages ranging from 60 to 67 years, who were receiving medical treatment for osteoporosis. They were assigned randomly into two groups: Group-I: Twenty patients practiced weight-bearing exercises. Group-II: Twenty patients did nonweight-bearing exercises. All patients trained for 45-60 min/session, two sessions/week for 6 months. BMD of the lumbar spine, right neck of femur, and right distal radial head of all patients were measured by dual-energy X-ray absorptiometry before and after both treatment programs. In addition, the QoL was measured by means of the HRQoL "ECOS-16" questionnaire.

RESULTS

T-tests proved that mean values of BMD of the lumbar spine, right neck of femur and right distal radial head were significantly increased in both groups with greater improvement in the weight-bearing group. The QoL was significantly improved in both groups, but the difference between them was not significant.

CONCLUSION

Addition of weight-bearing exercise program to medical treatment increases BMD more than nonweight-bearing exercise in elderly subjects with osteoporosis. Furthermore, both weight-bearing and nonweight-bearing exercise programs significantly improved the QoL of patients with osteoporosis.

Morphometric evaluation of proximal femur in patients with unilateral total hip prosthesis

It is important to know the morphometric characteristics of the proximal femur. This is necessary to reduce the risk of complications related to surgical procedures performed in the area due to vascular, metabolic, or traumatic causes. It is of importance for achieving the alignment of the prosthesis to be implanted as well. The aim of this study was to evaluate the morphometric characteristics of the proximal femur and to establish a database for making and performing total hip prosthesis. Anteroposterior (AP) pelvic radiographs of 162 cases, with a mean age of 65.6 years, who had undergone unilateral total hip arthroplasty were used in this study. Femoral head diameter (FHD), femoral neck width (FNW), femoral neck length (FNL), femoral neck axis length (FNAL), intertrochanteric line length (ILL), and neck-shaft angle (NSA) were measured on radiographs obtained digitally using setrapacs media. FHD was found to be 48.1 ± 3.7 mm, FNW 35.4 ± 4.2 mm, FNL 30.8 ± 6.1 mm, FNAL 98.6 ± 9.4 mm, ILL 81.1 ± 7.9 mm, and NSA 130.4 ± 5.1° on average. The comparison of the mean values for females and males revealed a statistically significant difference between the FHD, FNW, FNL, FNAL, and ILL (P = 0.000). There was no statistically significant difference in NSA between males and females (P = 0.356). A weak correlation was found between age and parameter values using correlation analysis (r < 0.24, P > 0.05). In morphometric assessment of the proximal femur, taking into consideration regional and sexual differences is of importance for prosthesis design and surgical success.

Femoral neck shaft angle width is associated with hip-fracture risk in males but not independently of femoral neck bone density

OBJECTIVE

To investigate the specificity of the neck shaft angle (NSA) to predict hip fracture in males.

METHODS

We consecutively studied 228 males without fracture and 38 with hip fracture. A further 49 males with spine fracture were studied to evaluate the specificity of NSA for hip-fracture prediction. Femoral neck (FN) bone mineral density (FN-BMD), NSA, hip axis length and FN diameter (FND) were measured in each subject by dual X-ray absorptiometry. Between-mean differences in the studied variables were tested by the unpaired t-test. The ability of NSA to predict hip fracture was tested by logistic regression.

RESULTS

Compared with controls, FN-BMD (p < 0.01) was significantly lower in both groups of males with fractures, whereas FND (p < 0.01) and NSA (p = 0.05) were higher only in the hip-fracture group. A significant inverse correlation (p < 0.01) was found between NSA and FN-BMD. By age-, height- and weight-corrected logistic regression, none of the tested geometric parameters, separately considered from FN-BMD, entered the best model to predict spine fracture, whereas NSA (p < 0.03) predicted hip fracture together with age (p < 0.001). When forced into the regression, FN-BMD (p < 0.001) became the only fracture predictor to enter the best model to predict both fracture types.

CONCLUSION

NSA is associated with hip-fracture risk in males but is not independent of FN-BMD.

ADVANCES IN KNOWLEDGE

The lack of ability of NSA to predict hip fracture in males independent of FN-BMD should depend on its inverse correlation with FN-BMD by capturing, as the strongest fracture predictor, some of the effects of NSA on the hip fracture. Conversely, NSA in females does not correlate with FN-BMD but independently predicts hip fractures.

A comparison of bone density and bone morphology between patients presenting with hip fractures, spinal fractures or a combination of the two

Background

Currently it is uncertain how to define osteoporosis and who to treat after a hip fracture. There is little to support the universal treatment of all such patients but how to select those most in need of treatment is not clear. In this study we have compared cortical and trabecular bone status between patients with spinal fractures and those with hip fracture with or without spinal fracture with the aim to begin to identify, by a simple clinical method (spine x-ray), a group of hip fracture patients likely to be more responsive to treatment with current antiresorptive agents.

Methods

Comparison of convenience samples of three groups of 50 patients, one with spinal fractures, one with a hip fracture, and one with both. Measurements consist of bone mineral density at the lumbar spine, at the four standard hip sites, number, distribution and severity of spinal fractures by the method of Genant, cortical bone thickness at the infero-medial femoral neck site, femoral neck and axis length and femoral neck width.

Results

Patients with spinal fractures alone have the most deficient bones at both trabecular and cortical sites: those with hip fracture and no spinal fractures the best at trabecular bone and most cortical bone sites: and those with both hip and spinal fractures intermediate in most measurements. Hip axis length and neck width did not differ between groups.

Conclusion

The presence of the spinal fracture indicates poor trabecular bone status in hip fracture patients. Hip fracture patients without spinal fractures have a bone mass similar to the reference range for their age and gender. Poor trabecular bone in hip fracture patients may point to a category of patient more likely to benefit from therapy and may be indicated by the presence of spinal fractures.

Comparison of femoral morphology and bone mineral density between femoral neck fractures and trochanteric fractures

BACKGROUND

Many studies that analyzed bone mineral density (BMD) and skeletal factors of hip fractures were based on uncalibrated radiographs or dual-energy xray absorptiometry (DXA).

QUESTIONS/PURPOSES

Spatial accuracy in measuring BMD and morphologic features of the femur with DXA is limited. This study investigated differences in BMD and morphologic features of the femur between two types of hip fractures using quantitative computed tomography (QCT).

PATIENTS AND METHODS

Forty patients with hip fractures with normal contralateral hips were selected for this study between 2003 and 2007 (trochanteric fracture, n=18; femoral neck fracture, n=22). Each patient underwent QCT of the bilateral femora using a calibration phantom. Using images of the intact contralateral femur, BMD measurements were made at the point of minimum femoral-neck cross-sectional area, middle of the intertrochanteric region, and center of the femoral head. QCT images also were used to measure morphologic features of the hip, including hip axis length, femoral neck axis length, neck-shaft angle, neck width, head offset, anteversion of the femoral neck, and cortical index at the femoral isthmus.

RESULTS

No significant differences were found in trabecular BMD between groups in those three regions. Patients with trochanteric fractures showed a smaller neck shaft angle and smaller cortical index at the femoral canal isthmus compared with patients with femoral neck fractures.

CONCLUSIONS

We conclude that severe osteoporosis with thinner cortical bone of the femoral diaphysis is seen more often in patients with trochanteric fracture than in patients with femoral neck fracture.

LEVELS OF EVIDENCE

Level IV, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

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.

Analysis of hip geometry by clinical CT for the assessment of hip fracture risk in elderly Japanese women

Two case-control studies were designed to investigate the contribution of the geometry and bone mineral density (BMD) of the proximal femur to bone strength in Japanese elderly women. We also investigated whether clinical CT is useful to assess the risk of hip fracture. Subjects in the neck fracture study included 20 Japanese women with neck fracture (age: mean+/-SD; 80.1+/-4.5 years old) and 20 age-matched control women (79.2+/-2.6 years old). Subjects in the trochanteric fracture study included 16 Japanese women with trochanteric fracture (82.6+/-5.0 years old) and 16 age-matched control women (80.8+/-3.8 years old). CT examination of the proximal femur was performed between the date of admission and the date of surgery. The CT scanners used were an Aquillion 16 (Toshiba) and Somatom 64 (Siemens); the scanning conditions including spatial resolution and scanning energy were adjusted, and the same type of reference phantom containing hydroxyapatite was used. QCT PRO software (Mindways) was used to analyze data for BMD, geometry, and biomechanical parameters. Both the neck and trochanteric fracture cases had significantly lower total and cortical BMD, a significantly smaller cortical cross-sectional area (CSA), and a larger trabecular CSA. Both had significantly thinner cortex and smaller distance to center of bone mass, and women with trochanteric fracture had a significantly smaller cortical perimeter in the cross-sectional femoral neck. Women with neck fracture had a longer hip axis length (HAL) and women with trochanteric fracture had a significantly larger neck-shaft angle (NSA). Both groups had significantly lower cross-sectional moment of inertia (CSMI), and only women with neck fracture had a significantly higher buckling ratio (BR) compared to their respective controls. According to the multiple logistic regression analysis, women with neck fracture had a significantly longer HAL, lower CSMI, and higher BR, and women with trochanteric fracture had a significantly smaller cortical CSA of the femoral neck. We conclude that clinical CT may be useful for the assessment of the risk of neck and trochanteric fracture.

Advances in osteoporosis imaging

In the assessment of osteoporosis, the measurement of bone mineral density (BMD(a)) obtained from dual energy X-ray absorptiometry (DXA; g/cm(2)) is the most widely used parameter. However, bone strength and fracture risk are also influenced by parameters of bone quality such as micro-architecture and tissue properties. This article reviews the radiological techniques currently available for imaging and quantifying bone structure, as well as advanced techniques to image bone quality. With the recent developments in magnetic resonance (MR) techniques, including the availability of clinical 3T scanners, and advances in computed tomography (CT) technology (e.g. clinical Micro-CT), in-vivo imaging of the trabecular bone architecture is becoming more feasible. Several in-vitro studies have demonstrated that bone architecture, measured by MR or CT, was a BMD-independent determinant of bone strength. In-vivo studies showed that patients with, and without, osteoporotic fractures could better be separated with parameters of bone architecture than with BMD. Parameters of trabecular architecture were more sensitive to treatment effects than BMD. Besides the 3D tomographic techniques, projection radiography has been used in the peripheral skeleton as an additional tool to better predict fracture risk than BMD alone. The quantification of the trabecular architecture included parameters of scale, shape, anisotropy and connectivity. Finite element analyses required highest resolution, but best predicted the biomechanical properties of the bone. MR diffusion and perfusion imaging and MR spectroscopy may provide measures of bone quality beyond trabecular micro-architecture.

Risk factors for severity and type of the hip fracture

More severe hip fractures such as displaced femoral neck (FN) fractures and unstable intertrochanteric (IT) fractures lead to poorer outcomes, but risk factors for severe fractures have not been studied. To identify risk factors for severe types of hip fracture, we performed a prospective cohort study and obtained preoperative hip radiographs from women who sustained an incident hip fracture (excluding traumatic fractures). A single radiologist scored the severity of FN fractures by the Garden System: grades I and II, undisplaced; grades III and IV, displaced. The severity of IT hip fractures was rated by the Kyle System: grades I and II, stable; grades III and IV, unstable. A total of 249 women had FN fractures: 75 (30%) were undisplaced. A total of 213 women had IT fractures: 59 (28%) were stable. Both types of hip fracture increased with age, but older age was even more strongly associated with more severe hip fractures. Low BMD was more strongly related to undisplaced FN fractures (p interaction BMD x FN type, p = 0.0008) and stable IT fractures (p interaction BMD x IT type, p = 0.04). Similar findings were observed for estimated volumetric BMD and hip geometric parameters. Corticosteroid use was only associated with displaced FN fractures, and Parkinson's disease was only associated with stable IT fractures. Little difference was reported in the self-reported circumstances surrounding each type of fracture. In conclusion, the lower the BMD, the greater the likelihood of experiencing a hip fracture that is less displaced and more stable.

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.

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.

Bone mass and architecture determination: state of the art

Bone fracture occurs when the bone strength (i.e. the ability of the bone to resist a force) is less than the force applied to the bone. In the elderly, falls represent the more severe forces applied to bone. Bone density is a good marker of bone strength, and has been used widely in this respect. Nevertheless, many aspects of bone strength cannot be explained by bone density alone. For this reason there has been increasing interest in studying architectural parameters of bone, beyond bone density, which may affect bone strength. Macro-architectural parameters include e.g. bone size and geometry assessed with techniques such as radiography, dual-energy x-ray absorptiometry (DXA), peripheral quantitative computed tomography (QCT), computed tomography (CT) and magnetic resonance imaging (MRI). Micro-architectural parameters include fine cortical and trabecular structural detail which can be evaluated using high-resolution imaging techniques such as multidetector CT, MRI, and high-resolution peripheral QCT. These techniques are providing a great deal of new information on the physiological architectural responses of bone to aging, weightlessness, and treatment. This will ultimately lead to the prediction of fracture risk being improved through a combined assessment of bone density and architectural parameters.

Fracture risk and bone mineral density in Turner syndrome

Bone health is a major lifelong concern in caring for women and girls with Turner syndrome (TS). There is an approximately 25% increase in fracture risk most of which is related to medium or high impact trauma. The long bones, especially of the forearm are predominantly affected. This fact may be due to a selective cortical bone deficiency in TS which is unrelated to hypogonadism. In addition, lack of adequate estrogen replacement can lead to trabecular bone deficiency and increase in vertebral compression fractures after age 45. Evaluation of bone density by dual X-ray absorptiometry (DEXA) is important, however, it should be used judiciously in TS in view of its inherent tendency to underestimate the bone density of people with short stature. Bone size-independent methods, such as QCT or volumetric transformation of DEXA data should be used in individuals shorter than 150 cm. Achieving optimal bone density is of critical importance for fracture prevention in TS, and should be pursued by timely introduction of hormone replacement therapy, adequate dose of estrogens during the young adult life, optimal calcium and vitamin D intake and regular physical exercise. In addition, other measures to prevent fall and trauma should be considered, including optimizing hearing and vision, avoiding contact sports and exercise to improve coordination.

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.

Bivariate linkage study of proximal hip geometry and body size indices: the Framingham study

Femoral geometry and body size are both characterized by substantial heritability. The purpose of this study was to discern whether hip geometry and body size (height and body mass index, BMI) share quantitative trait loci (QTL). Dual-energy X-ray absorptiometric scans of the proximal femur from 1,473 members in 323 pedigrees (ages 31-96 years) from the Framingham Osteoporosis Study were studied. We measured femoral neck length, neck-shaft angle, subperiosteal width (outer diameter), cross-sectional bone area, and section modulus, at the narrowest section of the femoral neck (NN), intertrochanteric (IT), and femoral shaft (S) regions. In variance component analyses, genetic correlations (rho ( G )) between hip geometry traits and height ranged 0.30-0.59 and between hip geometry and BMI ranged 0.11-0.47. In a genomewide linkage scan with 636 markers, we obtained nominally suggestive linkages (bivariate LOD scores > or =1.9) for geometric traits and either height or BMI at several chromosomes (4, 6, 9, 15, and 21). Two loci, on chr. 2 (80 cM, BMI/shaft section modulus) and chr. X (height/shaft outer diameter), yielded bivariate LOD scores > or =3.0; although these loci were linked in univariate analyses with a geometric trait, neither was linked with either height or BMI. In conclusion, substantial genetic correlations were found between the femoral geometric traits, height and BMI. Linkage signals from bivariate linkage analyses of bone geometric indices and body size were similar to those obtained in univariate linkage analyses of femoral geometric traits, suggesting that most of the detected QTL primarily influence geometry of the hip.

Structural and functional assessment of trabecular and cortical bone by micro magnetic resonance imaging

Osteoporosis is a multifactorial disorder of bone mineral homeostasis affecting the elderly. It is a major public health issue with significant socioeconomic consequences. Recent findings suggest that bone loss-the key manifestation of the disease-is accompanied by architectural deterioration, both affecting the bone's mechanical competence and susceptibility to fracture. This article reviews the potential of quantitative micro MRI (mu-MRI), including a discussion of the technical requirements for image acquisition, processing, and analysis for assessing the architectural implications of osteoporosis and as a means to monitor the response to treatment. With current technology, the resolution achievable in clinically acceptable scan times and necessary signal-to-noise ratio (SNR) is comparable to trabecular thickness. This limited spatial resolution regime demands processing and analysis algorithms designed to operate under such limiting conditions. It is shown that three different classes of structural parameters can be distinguished, characterizing scale, topology, and orientation. There is considerable evidence that osteoporotic bone loss affects all three classes but that topological changes, resulting from conversion of trabecular plates to rods, with the latter's eventual disconnection, are particularly prominent. Clinical applications discussed can be divided into those dealing with assessment of osteoporotic fracture risk as opposed to the study of the effect of disease progression and regression in response to treatment. Current data suggest that noninvasive assessment of cortical and trabecular bone (TB) architecture by mu-MRI may provide new surrogate endpoints to assess the efficacy of intervention in osteoporosis treatment and prevention.

Association and linkage analysis of COL1A1 and AHSG gene polymorphisms with femoral neck bone geometric parameters in both Caucasian and Chinese nuclear families

AIM

To simultaneously investigate the contribution of the alpha 1 chain of collagen type 1 (COL1A1) and alpha2-HS-glycoprotein (AHSG) genes to the variation of bone geometric parameters in both Caucasians and Chinese.

METHODS

Six hundred and five Caucasian individuals from 157 nuclear families and 1228 Chinese subjects from 400 nuclear families were genotyped at the AHSG-SacI, COL1A1- PCOL2 and Sp1 polymorphisms using polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP). 5 FN bone geometric parameters were calculated based on bone mineral density and bone area of femoral neck (FN) measured by dual energy X-ray absorptiometry. Population stratification, total family association, within-family association, and linkage tests were performed by the quantitative transmission disequilibrium test program.

RESULTS

The t-test showed the significant differences of all bone geometric phenotypes (except ED) between Caucasians and Chinese in the offspring using both unadjusted and adjusted (by age, height, weight, and gender) data. In Caucasians, we found significant within-family association results between the COL1A1-Sp1 polymorphism (rs1800012) and cross sectional area (CSA), cortical thickness (CT), endocortical diameter (ED), buckling ratio (BR) (P=0.018, 0.002, 0.023, and 0.001, respectively); the COL1A1-Sp1 polymorphism also detected significant linkage with BR (P=0.039). In the population of China, the within-family associations between the COL1A1-PCOL2 polymorphism (rs1107946) and CT, BR were significant (P=0.012 and 0.008, respectively). Furthermore, evidence of linkage were observed between the AHSG-SacI polymorphism (rs4918) and CT, BR (P=0.042 and 0.014, respectively) in Caucasians, but not in Chinese.

CONCLUSION

Our results suggest that the COL1A1 gene may have significantly association with bone geometry in both Caucasians and Chinese, and the AHSG gene may be linked to bone geometry in Caucasians, but not in Chinese. This study represents our first efforts on investigating the importance of the COL1A1 and AHSG genes on bone geometry in both Caucasians and Chinese.

Age-related trends in hip geometry in Sri Lankan women: a cross-sectional study

Indices of hip geometry are known to be predictive of hip fractures while sex and ethnic differences in hip geometry have been previously demonstrated. Age-related trends in hip geometry among Asians, however, have not been studied sufficiently. A total of 280 healthy, perimenopausal women, aged between 32 and 97 years, were selected from the Community Study Area of the Faculty of Medicine, Galle, Sri Lanka. Hip DXA images were analyzed further to calculate the hip axis length, neck-shaft angle, and femoral neck width at the narrowest point of the femoral neck. Standard formulae were used to calculate cross-sectional area, cross-sectional moment of inertia, and section modulus in the femoral neck region. Mean (SD) age, weight, height, femoral neck bone mineral density (BMD), hip axis length, neck-shaft angle, neck width, cross-sectional area, and cross-sectional moment of inertia of the study sample were 56.8 (13.0) years, 47.8 (10.1) kg, 1.48 (0.06) m, 0.704 (0.147) g/cm(2), 90.6 (5.6) mm, 123.2 (5.7) degrees, 2.99 (0.24) cm, 2.00 (0.42) cm(2), and 1.62 (0.47) cm(4), respectively. Height and weight of subjects had positive correlations with most of the indices of hip geometry. Femoral neck BMD, cross-sectional area and section modulus showed a rapid reduction during the postmenopausal period. With advancing age, there was a marginal but statistically nonsignificant expansion of the neck width, increase in the hip axis length, and narrowing of the neck-shaft angle. In conclusion, this study demonstrated a gradual loss of BMD in postmenopausal age, accompanied by thinning of the cortical shell and deterioration of the resistance to bending in the femoral neck of this group of healthy women. The clinical relevance of the marginal changes seen in other indices such as neck-shaft angle, hip axis length, and neck width is not known.

Neue Techniken in der Osteoporosediagnostik

In this review article current developments and applications in quantitative osteoporosis imaging are presented. Developments in the field of DXA include geometrical parameters of the proximal femur such as the "hip axis length" and new ROIs to determine BMD. Advances in QCT are new volumetric techniques to quantify BMD at the lumbar spine and the proximal femur. In addition techniques to determine BMD in standard contrast-enhanced abdominal computed tomography studies are described. Currently with the new bone quality concept in full bloom techniques to quantify trabecular bone architecture as new surrogates of bone strength are of increasing significance. Spatial high-resolution techniques such as magnetic resonance imaging and new computed tomography techniques have shown their potential in assessing trabecular bone structure. In addition ultrasound is considered a low-cost technique to explore bone quality.

Bone density testing in clinical practice

The diagnosis of osteoporosis and monitoring of treatment is a challenge for physicians due to the large number of available tests and complexities of interpretation. Bone mineral density (BMD) testing is a non-invasive measurement to assess skeletal health. The "gold-standard" technology for diagnosis and monitoring is dual-energy X-ray absorptiometry (DXA) of the spine, hip, or forearm. Fracture risk can be predicted using DXA and other technologies at many skeletal sites. Despite guidelines for selecting patients for BMD testing and identifying those most likely to benefit from treatment, many patients are not being tested or receiving therapy. Even patients with very high risk of fracture, such as those on long-term glucocorticoid therapy or with prevalent fragility fractures, are often not managed appropriately. The optimal testing strategy varies according to local availability and affordability of BMD testing. The role of BMD testing to monitor therapy is still being defined, and interpretation of serial studies requires special attention to instrument calibration, acquisition technique, analysis, and precision assessment. BMD is usually reported as a T-score, the standard deviation variance of the patient's BMD compared to a normal young-adult reference population. BMD in postmenopausal women is classified as normal, osteopenia, or osteoporosis according to criteria established by the World Health Organization. Standardized methodologies are being developed to establish cost-effective intervention thresholds for pharmacological therapy based on T-score combined with clinical risk factors for fracture.

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.

Femur strength index predicts hip fracture independent of bone density and hip axis length

INTRODUCTION

Proximal femoral bone strength is not only a function of femoral bone mineral density (BMD), but also a function of the spatial distribution of bone mass intrinsic in structural geometric properties such as diameter, area, length, and angle of the femoral neck. Recent advancements in bone density measurement include software that can automatically calculate a variety of femoral structural variables that may be related to hip fracture risk. The purpose of this study was to compare femoral bone density, structure, and strength assessments obtained from dual-energy X-ray absorbtiometry (DXA) measurements in a group of women with and without hip fracture.

METHODS

DXA measurements of the proximal femur were obtained from 2,506 women 50 years of age or older, 365 with prior hip fracture and 2,141 controls. In addition to the conventional densitometry measurements, structural variables were determined using the Hip Strength Analysis program, including hip axis length (HAL), cross-sectional moment of inertia (CSMI), and the femur strength index (FSI) calculated as the ratio of estimated compressive yield strength of the femoral neck to the expected compressive stress of a fall on the greater trochanter.

RESULTS

Femoral neck BMD was significantly lower and HAL significantly higher in the fracture group compared with controls. Mean CSMI was not significantly different between fracture patients and controls after adjustment for BMD and HAL. FSI, after adjustment for T score and HAL, was significantly lower in the fracture group, consistent with a reduced capacity to withstand a fall without fracturing a hip.

CONCLUSION

We conclude that BMD, HAL, and FSI are significant independent predictors of hip fracture.

Update on bone density testing

Bone mineral density (BMD) testing is a noninvasive measurement to diagnose osteoporosis or low bone density, predict fracture risk, and monitor changes in bone density over time. The "gold-standard" technology for diagnosis and monitoring is dual-energy x-ray absorptiometry of the spine, hip, or forearm. Fracture risk can be predicted using a variety of technologies at many skeletal sites. BMD is usually reported as T-score, the standard deviation variance of the patient's BMD compared with a normal young-adult reference population. In untreated postmenopausal women, there is a strong correlation between T-score and fracture risk, with fracture risk increasing approximately two-fold for every standard deviation decrease in bone density. BMD in postmenopausal women is classified as normal, osteopenia, or osteoporosis according to criteria established by the World Health Organization. Standardized methodologies are being developed to establish intervention thresholds for pharmacologic therapy based on T-score combined with clinical risk factors for fracture.

Schmid type of metaphyseal chondrodysplasia and COL10A1 mutations--findings in 10 patients

The Schmid type of metaphyseal chondrodyplasia (MCDS) is characterized by short stature, widened growth plates, and bowing of the long bones. It results from autosomal dominant mutations of COL10A1, the gene which encodes alpha1(X) chains of type X collagen. We report the clinical and radiographic findings in 10 patients with MCDS and COL10A1 mutations. Six patients had lower limb deformities, which necessitated orthopedic surgeries in all of them. One patient demonstrated no deformities and normal stature at age 11 years (height -1.2 SDS) while the others manifested severe short stature (<-3.5 SDS). Radiographs showed metaphyseal changes which were most pronounced at the hips and knees. Five of the identified 10 mutations in COL10A1 were novel. Six mutations resulted in truncation of the NC1 domain while four mutations were single amino-acid substitutions. Our findings suggest that COL10A1 mutations result in a uniform pattern of growth plate abnormalities. However, the clinical variability in severity among affected individuals is greater than previously thought.

Medial and lateral osteoarthritis of the knee is related to variations of hip and pelvic anatomy

OBJECTIVE

We evaluated if increased risk of combined hip and lateral knee osteoarthritis (OA) could be attributed to anatomical reasons in the hip region resulting in increased abductor moment over the knee.

METHODS

We measured pelvic width, femoral offset, femoral neck length and angle in 29 women with lateral knee OA (13 unilateral, 16 bilateral) and 27 women with bilateral medial OA. Twenty-one of these patients with normal hips (lateral/medial OA of the knee=12/9) and 35 with associated hip OA (lateral/medial OA of the knee=17/18) were evaluated separately. Radiographic examinations in 14 women planned for hip prosthesis because of failures after hip fracture acted as controls.

RESULTS

Patients with lateral OA of the knee had wider pelvis than controls (13.7 mm increased distance between the medial borders of the acetabulum, P=0.001). Patients with medial OA had 11.4mm longer distance from the centre of the femoral head to the centre of the proximal part of the femoral shaft (P=0.005), corresponding to a higher offset. The pelvic and hip anatomy also differed between patients with medial and lateral OA of the knee. In the groups without hip OA, presence of lateral knee OA was associated with a wider pelvis (P=0.009), shorter femoral neck (P=0.02) and Head-Shaft distance (P=0.04). In the groups with OA of the hip associated lateral OA of the knee also implied increased Neck Shaft angle (coxa valga, P=0.008), but there was no difference in pelvic width (P=0.15). We found a shorter lever arm over the hip in lateral knee OA compared to medial knee OA (P=0.02), but not when compared to controls.

CONCLUSION

Our findings suggest that occurrence of medial or lateral OA has a biomechanical background originating from pelvis and hip anatomy.

Management of osteoporosis

Osteoporosis or osteopenia occurs in about 44 million Americans, resulting in 1.5 million fragility fractures per year. The consequences of these fractures include pain, disability, depression, loss of independence, and increased mortality. The burden to the healthcare system, in terms of cost and resources, is tremendous, with an estimated direct annual USA healthcare expenditure of about $17 billion. With longer life expectancy and the aging of the baby-boomer generation, the number of men and women with osteoporosis or low bone density is expected to rise to over 61 million by 2020. Osteoporosis is a silent disease that causes no symptoms until a fracture occurs. Any fragility fracture greatly increases the risk of future fractures. Most patients with osteoporosis are not being diagnosed or treated. Even those with previous fractures, who are at extremely high risk of future fractures, are often not being treated. It is preferable to diagnose osteoporosis by bone density testing of high risk individuals before the first fracture occurs. If osteoporosis or low bone density is identified, evaluation for contributing factors should be considered. Patients on long-term glucocorticoid therapy are at especially high risk for developing osteoporosis, and may sustain fractures at a lower bone density than those not taking glucocorticoids. All patients should be counseled on the importance of regular weight-bearing exercise and adequate daily intake of calcium and vitamin D. Exposure to medications that cause drowsiness or hypotension should be minimized. Non-pharmacologic therapy to reduce the non-skeletal risk factors for fracture should be considered. These include fall prevention through balance training and muscle strengthening, removal of fall hazards at home, and wearing hip protectors if the risk of falling remains high. Pharmacologic therapy can stabilize or increase bone density in most patients, and reduce fracture risk by about 50%. By selecting high risk patients for bone density testing it is possible to diagnose this disease before the first fracture occurs, and initiate appropriate treatment to reduce the risk of future fractures.