Meng Ai Png

An emerging pattern of subtrochanteric stress fractures: A long-term complication of alendronate therapy?*

BACKGROUND Subtrochanteric insufficiency fractures in post-menopausal patients have not been commonly reported in the literature. A recent increase in the incidence of such fractures occurring in patients while on alendronate therapy led us to conduct a retrospective review of these patients in our institution. METHODS Seventeen patients, with a mean age of 66 years, sustained low energy subtrochanteric fractures within a 20-month period. These patients were incidentally found to be on alendronate therapy for an average of 4.8 years. Clinical data and history were reviewed and roentgenograms were evaluated by a single investigator. All additional imaging and bone mineral density measurements available were analysed. RESULTS A characteristic fracture configuration suggestive of an insufficiency stress fracture was identified on plain radiographs. This consisted of (a) cortical thickening in the lateral side of the subtrochanteric region, (b) a transverse fracture, and (c) a medial cortical spike. In addition, 9 (53%) patients had bilateral findings of stress reactions or fractures, and 13 (76%) had symptoms of prodromal pain. CONCLUSIONS These insufficiency fractures could possibly have developed from the over suppression of bone turnover from prolonged alendronate therapy, in keeping with recently published evidence. This study further highlights the need for heightened awareness of alendronates potential adverse effects.

Femoral cortical stress lesions in long-term bisphosphonate therapy: a herald of impending fracture?

Objective: Lateral cortical stress reactions have been documented to precede femoral insufficiency fractures after long-term bisphosphonate therapy. We studied the natural history of femoral stress lesions associated with long-term bisphosphonate therapy. Design and Setting: A retrospective clinical and radiologic review of all patients with radiologically documented femoral stress lesions associated with bisphosphonate therapy was carried out in a tertiary center involved with geriatric trauma care. Patients: Of 1463 geriatric hip fractures occurring from May 1, 2004, to July 31, 2008, 33 were of a distinct metaphyseal-diaphyseal configuration. Thirty-two were on prior bisphosphonate therapy. Sixteen femurs showed a lateral cortical thickening either on prefracture radiographs (four femurs) or on radiographs of the contralateral femur (12 femurs). Main Outcome Measures: Features that predispose to complete stress fractures were determined. The intact femurs were followed up for symptomatic and radiologic progression and occurrence of new lesions. Results: All four cases that fractured had a “dreaded black line” in the lesion, whereas only 1 of 12 patients had this fracture in femurs which remained intact (100% versus 8.3%, P = 0.003). All patients who fractured reported thigh discomfort over 1 month (range, 0.1-9.0 months; standard deviation, 4.0 months), whereas three of 12 patients who did not fracture reported thigh discomfort (100% versus 25%, P = 0.019). In the remaining patients, eight patients were asymptomatic, two patients had reduced symptoms, and one patient had persistent thigh pain at 23.0 months (range, 5-35 months; standard deviation, 10.2 months). One patient was too demented for symptomatic assessment. No patient developed a new lesion. Radiologic stabilization of the lateral cortical thickening was evident on follow-up radiographs. Conclusion: Cortical stress reactions associated with prolonged antiresorptive therapy, in the presence of pain and the “dreaded black line,” have an increased risk for complete stress fractures.

Computing Neck-Shaft Angle of Femur for X-Ray Fracture Detection

Worldwide, 30% – 40% of women and 13% of men suffer from osteoporotic fractures of the bone, particularly the older people. Doctors in the hospitals need to manually inspect a large number of x-ray images to identify the fracture cases. Automated detection of fractures in x-ray images can help to lower the workload of doctors by screening out the easy cases, leaving a small number of difficult cases and the second confirmation to the doctors to examine more closely. To our best knowledge, such a system does not exist as yet. This paper describes a method of measuring the neck-shaft angle of the femur, which is one of the main diagnostic rules that doctors use to determine whether a fracture is present at the femur. Experimental tests performed on test images confirm that the method is accurate in measuring neck-shaft angle and detecting certain types of femur fractures.

Combining classifiers for bone fracture detection in X-ray images

In medical applications, sensitivity in detecting medical problems and accuracy of detection are often in conflict. A single classifier usually cannot achieve both high sensitivity and accuracy at the same time. Methods of combining classifiers have been proposed in the literature. This paper presents a study of probabilistic combination methods applied to the detection of bone fractures in X-ray images. Test results show that the effectiveness of a method in improving both accuracy and sensitivity depends on the nature of the method as well as the proportion of positive samples.

Detecting femur fractures by texture analysis of trabeculae

30% of women and 13% of men worldwide suffer from osteoporotic bone fractures worldwide. In large hospitals, doctors need to visually inspect a large number of X-ray images to identify the fracture cases, which typically constitute about 12% of all the X-ray images examined. Automated fracture detection can help to screen for obvious cases and flag suspicious cases for closer examinations. This paper describes a method of detecting femur fractures by analyzing trabecular texture patterns. Test results show that it is more accurate than an existing method based on neck-shaft angle. Moreover, combining the methods further improve the overall performance of fracture detection.

Bisphosphonate-related femoral periosteal stress reactions: scoring system based on radiographic and MRI findings.

OBJECTIVE The purpose of this study was to review the radiographic and MRI findings of bisphosphonate-related femoral periosteal stress reactions to propose a scoring system for predicting symptoms and fracture risk. MATERIALS AND METHODS A retrospective study included patients undergoing long-term bisphosphonate therapy who had radiographic evidence of focal femoral periosteal thickening on radiographs and MR images. There were 43 femoral periosteal stress reactions in 33 patients; eight patients underwent MRI. Radiographs and MR images were evaluated for focal cortical thickening (periosteal and endosteal), bone edema, focal cortical abnormalities (radiolucency, striations, cavities), and dreaded black line. The radiographic score (derived with statistical methods) and simple scores (simple radiographic, MRI, and combined scores) were compared with symptoms and fracture outcome. RESULTS Logistic regression analysis showed an association between radiographic dreaded black line and symptoms (odds ratio, 68.0). Kaplan-Meier and Cox regression analyses showed radiographic dreaded black line (p < 0.0005; hazard ratio, 27.3) and focal cortical radiolucency (p = 0.011; hazard ratio, 6.8) were independent predictors of fracture. The survival score derived from Cox regression coefficients showed good separation of high- and low-risk groups. Mann-Whitney tests showed an association between MRI and combined scores and symptoms (p = 0.036, p = 0.036). The area under the receiver operating characteristic curve suggested better association with symptoms for MRI and combined scores than for simple radiographic scores (1.00, 1.00, 0.93). CONCLUSION In bisphosphonate-related femoral periosteal stress reactions, radiographic dreaded black line and MRI and combined scores were associated with symptoms, and radiographic survival score was predictive of fracture risk. The relation between MRI and combined scores and fracture was not statistically significant.

Atypical Fractures Are Mainly Subtrochanteric in Singapore and Diaphyseal in Sweden: A Cross-Sectional Study

We have previously noted a dichotomy in the location of atypical fractures along the femoral shaft in Swedish patients, and a mainly subtrochanteric location of atypical fractures in descriptions of patients from Singapore. These unexpected differences were now investigated by testing the following hypotheses in a cross‐sectional study: first, that there is a dichotomy also in Singapore; second, that the relation between subtrochanteric and diaphyseal location is different between the two countries; third, that the location is related to femoral bow. The previously published Swedish sample (n = 151) was re‐measured, and a new Singaporean sample (n = 75) was established. Both samples were based on radiographic classification of all femoral fractures in women above 55 years of age. The distance between the fracture line and the lesser trochanter was measured. Femoral bow was classified as present or absent on frontal radiographs. Frequency distribution of the measured distances was analyzed using the Bayesian information criterion to choose the best description of the observed variable distribution in terms of a compilation of normally distributed subgroups. The analysis showed a clear dichotomy of the fracture location: either subtrochanteric or diaphyseal. Subtrochanteric fractures comprised 48% of all fractures in Singapore, and 17% in Sweden (p = 0.0001). In Singapore, femoral bow was associated with more fractures in the diaphyseal subgroup (p = 0.0001). This was not seen in Sweden. A dichotomous location of atypical fractures was confirmed, because it was found also in Singapore. The fractures showed a different localization pattern in the two countries. This difference may be linked to anatomical variations, but might also be related to cultural differences between the two populations that influence physical activity.

Bone cross-sectional geometry is not associated with atypical femoral fractures in Asian female chronic bisphosphonate users

INTRODUCTION Atypical femoral fractures (AFF) tend to occur in Asian women with prolonged bisphosphonate exposure. Hip geometry is thought to contribute to the risk of AFF formation. We examined the hip structural geometry parameters in Asian female chronic bisphosphonate users who sustained an AFF and compared them to chronic bisphosphonate users who did not sustain any femoral fracture (NFF) and bisphosphonate-naïve patients who sustained an osteoporotic femoral fracture (OFF). MATERIALS & METHODS Thirty-one patients with AFFs were gender and age-matched to 31 patients with NFFs and 49 patients with OFFs. The Hip Structural Analysis parameters analyzed were bone mineral density (BMD), cross-sectional area (CSA; a metric of resistance to axial compression), section modulus (SM; a metric of resistance to tensile loads), average cortical thickness (ACT; mean thickness of the femoral cortices), buckling ratio (BR; an index of likelihood of local buckling), and neck shaft angle (NSA; the angle between the neck and shaft axes). The regions analyzed were three cross-sections measured at the narrowest femoral neck diameter, the intertrochanteric area, and the proximal femoral shaft. One-way ANOVA with Bonferroni adjustment for multiple comparisons was used to compare parameters between the three patient groups, with statistical significance defined as p<0.05. RESULTS There were no statistical differences in parameters between patients with AFFs and patients with NFFs at all measured regions. Patients with AFFs and NFFs had statistically higher BMD, CSA, ACT, SM values and lower BR values at the NN and IT regions than patients with OFFs. Additionally, patients with NFFs had statistically higher SM values at the IT region than patients with OFFs, while patients with AFFs had statistically higher BMD, CSA, and ACT values at the FS region. All other measured parameters were not statistically different between the groups. CONCLUSIONS Chronic bisphosphonate users with and without AFFs had similar femoral structural geometries. Unlike in other populations, varus neck shaft angles were not found to be associated with AFFs in Asian female chronic bisphosphonate users. Thus, bone cross-sectional geometry is not likely to be associated with AFFs in Asian female chronic bisphosphonate users. Hip Structural Analysis does not show an increased predilection for tensile failure in AFFs.

Atypical femoral fractures: transverse morphology at lateral cortex is a critical feature.

In 2010, the American Society for Bone and Mineral Research (ASBMR) task force defined major and minor features to assist in the case finding and reporting of atypical femoral fractures (AFFs). One major feature that was proposed was a “transverse or short oblique configuration.” Our primary aim was to compare the conventional overall fracture morphology (OFM) with its associated angle (OFMA) and our proposed lateral cortical fracture angle (LCFA) in the assessment of fracture configuration in suspected AFFs and non‐AFFs. The radiographs of 79 patients with AFFs and 39 patients with non‐AFFs were each analyzed by two blinded reviewers to obtain the OFM, OFMA, and LCFA. Using the overall fracture morphology to assess the suspected AFFs resulted in discordance between reviewers in 18 cases (22.8%), of which 5 (6.3%) were discordant between short oblique (>30° to 60°) and long oblique (>60° to 90°) configurations, therefore affecting their classifications as AFFs. By assessing only the critical component within the lateral cortex, all the suspected AFFs fell well within the classification as transverse fractures with a mean LCFA of 4.8° (range 0.3 to 18.0, SD = 4.23). The inter‐reader variability was also lower for LCFA versus OFMA (4.1° versus 6.9°, p = 0.001) when used to assess AFFs. Fracture angles were significantly different in AFFs versus non‐AFFs regardless of whether the OFMA or LCFA methodology was employed, but the greater difference associated with LCFA suggests its greater discriminating power. When LCFA was used in conjunction with 0° to 30° as the criteria for transverse morphology, all the AFFs and non‐AFFs were correctly classified. By using a standardized and precise method in measuring the fracture angle, specifically using only the component of the lateral cortex and limiting to truly transverse fractures, ie, between 0° and 30°, the LCFA is a robust and accurate method to assess the fracture morphology in suspected AFFs.

Review: Epidemiology and Pathophysiology of Atypical Femur Fractures

The recent recognition of the clinical phenomenon of atypical femoral fractures has garnered significant scientific interest. In this review, we will discuss and summarize the salient developments in the current understanding of the epidemiology, pathophysiology, and radiology of atypical femoral fractures.