Pathogenesis, management and prevention of atypical femoral fractures

The role of the fracture liaison service in the prevention of atypical femoral fractures

Osteoporosis and fragility fractures (FFs) are considered critical health problems by the World Health Organization (WHO) because of high morbidity, mortality, and healthcare costs. The occurrence of a FF raises the risk of a subsequent fracture (refracture). The hip is the most common site of fragility refracture, and its onset is associated with a further increase in patient's morbidity, mortality, and socioeconomic burden. Therefore, the prevention of refracture is essential. In this context, fracture liaison service (FLS) demonstrated to be able to reduce FF risk and also improve patients' adherence to anti-osteoporotic treatments, particularly for bisphosphonates (BPs). However, long-term and high adherence to BPs may lead to atypical femoral fractures (AFFs). These latter are tensile side stress fractures of the femur, with high rates of complications, including delayed and non-healing. An effective FLS should be able to prevent both FF and AFF. A comprehensive and interdisciplinary approach, through the involvement and education of a dedicated team of healthcare professionals (i.e. orthopedic, geriatrician, primary care physician, rehabilitation team, and bone nurse) for evaluating both FF and AFF risks might be useful to improve the standard of care.

Atypical Femoral Fracture in Hypophosphatasia: A Systematic Review

Objective

To summarize the characteristics of all reported patients with hypophosphatasia (HPP) who sustained atypical femoral fracture (AFF) and identify all available evidence to quantify the rate of coexistence between HPP and AFF.

Methods

Potentially eligible articles were identified from the MEDLINE and EMBASE databases from its inception to September 2022, using a search strategy consisting of terms related to "Hypophosphatasia" and "Atypical femoral fracture." Eligible articles must report one of the following information: (1) individual data of patients diagnosed with HPP and AFF, (2) prevalence of HPP among patients with AFF, or (3) prevalence of AFF among patients of HPP. Characteristics of patients reported in each study were extracted.

Results

A total of 148 articles were identified. After the systematic review, 24 articles met the eligibility criteria. A total of 28 patients with AFF and HPP were identified. The mean ± SD age of the reported patients was 53.8 ± 12.5 years, and 22 patients (78.6%) were female. Nine patients (32.1%) received antiresorptive medication (bisphosphonate and/or denosumab), and two patients (7.1%) received teriparatide prior to the development of AFF. Seven (25.0%) and eighteen (64.3%) patients sustained unilateral and bilateral AFF, respectively (laterality not reported in three cases). Thirteen patients (46.4%) had a history of fractures at other sites. Four (14.3%) and seven (25.0%) patients received asfotase alfa and teriparatide after sustaining AFF. Two studies reported the prevalence of AFF among patients with HPP of approximately 10%. One study reported one HPP patient in a cohort of 72 patients with AFF.

Conclusions

Based on the limited evidence, AFF occurred in up to 10% of patients with HPP. Based on the 28 case reports, about two-thirds did not receive antiresorptive treatment, suggesting that the HPP itself could potentially be a risk factor for AFF.

Position Statement: Atypical Femoral Fracture from the Korean Society for Bone and Mineral Research in 2023

As the aging population increases, the number of patients with osteoporosis is gradually rising. Osteoporosis is a metabolic bone disease characterized by low bone mass and the microarchitectural deterioration of bone tissue, resulting in reduced bone strength and an increased risk of low-energy or fragility fractures. Thus, the use of anti-resorptive agents, such as bisphosphonates (BPs), to prevent osteoporotic fractures is growing annually. BPs are effective in reducing hip and other fractures. However, the longer a patient takes BPs, the higher the risk of an atypical femoral fracture (AFF). The exact mechanism by which long-term BP use affects the development of AFFs has not yet been clarified. However, several theories have been suggested to explain the pathogenesis of AFFs, such as suppressed bone remodeling, impaired bone healing, altered bone quality, and femoral morphology. The management of AFFs requires both medical and surgical approaches. BPs therapy should be discontinued immediately, and calcium and vitamin D levels should be evaluated and supplemented if insufficient. Teriparatide can be used for AFFs. Intramedullary nailing is the primary treatment for complete AFFs, and prophylactic femoral nailing is recommended if signs of an impending fracture are detected.

Medication-related osteonecrosis and osteoradionecrosis of the jaws: Update and current management

Medication related osteonecrosis of the jaws (MRONJ) and osteoradionecrosis of the jaws (ORNJ) are two different diseases of quite similar appearance. MRONJ is mainly due to antiresorptive or antiangiogenic drug therapy and ORNJ to radiotherapy. The present work aimed at presenting and comparing the current knowledge on MRONJ and ORNJ. They both present as an exposure of necrotic bone and differ in some clinical or radiological characteristics, clinical course and mostly in treatment. They share similar risk factors. A tooth extraction is more frequently found as a triggering factor in MRONJ. The frequency of a maxillary localisation seems higher for MRONJ. On computed tomographic images, a periosteal reaction seems characteristic of MRONJ. More frequent pathological fractures seem to occur in ORNJ. It is mandatory, for ORNJ diagnosis, to exclude a residual or recurrent tumour using histological examination. Both MRONJ and ORNJ are challenging to treat and cannot be managed similarly. For both, it would still be worth to optimise awareness within the medical community, patients' oral hygiene and dental cares to improve their prevention and make their incidences decrease. Conservative therapy is more frequently achieved for MRONJ than ORNJ and surgical resection is more often performed for ORNJ. For both diseases, the last treatment possible in refractory cases is a surgical extensive resection with free flap reconstruction. A MRONJ classification is widely used today, whereas no consensus exists to date for ORNJ classification. We propose a classification that could play this role.

Bone-Targeting AAV-Mediated Gene Silencing in Osteoclasts for Osteoporosis Therapy

Improper activity of bone-resorbing osteoclasts results in low bone density and deterioration of bone structure, which increase the risk of fractures. Anti-resorptive therapies targeting osteoclasts have proven effective in preserving bone mass, but these therapeutic agents lead to defective new bone formation and numerous potential side effects. In this study, we demonstrate that recombinant adeno-associated virus, serotype 9 (rAAV9) can deliver to osteoclasts an artificial microRNA (amiR) that silences expression of key osteoclast regulators, RANK (receptor activator for nuclear factor κB) and cathepsin K (rAAV9.amiR-rank, rAAV9.amiR-ctsk), to prevent bone loss in osteoporosis. As rAAV9 is highly effective for the transduction of osteoclasts, systemic administration of rAAV9 carrying amiR-rank or amiR-ctsk results in a significant increase of bone mass in mice. Furthermore, the bone-targeting peptide motif (Asp)14 or (AspSerSer)6 was grafted onto the AAV9-VP2 capsid protein, resulting in significant reduction of transgene expression in non-bone peripheral organs. Finally, systemic delivery of bone-targeting rAAV9.amiR-ctsk counteracts bone loss and improves bone mechanical properties in mouse models of postmenopausal and senile osteoporosis. Collectively, inhibition of osteoclast-mediated bone resorption via bone-targeting rAAV9-mediated silencing of ctsk is a promising gene therapy that can preserve bone formation and mitigate osteoporosis, while limiting adverse off-target effects.

Localization of Atypical Femoral Fracture on Straight and Bowed Femurs

Background

To elucidate the effect of anterolateral bowing on the fracture height of atypical femoral fractures (AFFs), we separated the AFFs into 2 groups according to the presence of anterolateral femoral bowing (straight group and bowing group) and analyzed the fracture height. The aims of this study were to evaluate the clinical and radiological features of AFFs in the straight group and bowing group, and to determine which factors were associated with the fracture height of AFFs in the total cohort and each subgroup.

Methods

Ninety-nine patients with AFFs were included in this study (43 patients in the bowing group and 56 patients in the straight group). Clinical and radiological characteristics were compared between the groups. Multivariable linear regression analysis was performed to determine the effect of factors on fracture height.

Results

Patients in the straight group were younger, heavier, and taller, and had a higher bone mineral density, smaller anterior and lateral bowing angles, and more proximal fracture height than those in the bowing group. Multivariable analysis showed that the presence of anterolateral bowing itself and height were associated with fracture height in the total cohort. In the subgroup analysis, the lateral bowing angle in the straight group and the estimated apex height in the bowing group were associated with fracture height. The lateral bowing angle was not significantly associated with fracture height in the total cohort and the bowing group.

Conclusions

The presence of anterolateral bowing and the level of the apex of the bowed femur were important factors for the fracture height of AFFs.

Bone mineralization and vascularization in bisphosphonate-related osteonecrosis of the jaw: an experimental study in the rat

OBJECTIVES

Pathogenesis of bisphosphonate-related osteonecrosis of the jaws (BRONJ) is not fully explained. An antiangiogenic effect of bisphosphonates (BPs) or an altered bone quality have been advocated. The aims of the present study were to analyze alveolar mandibular vascularization and bone quality in rats with BRONJ.

MATERIALS AND METHODS

Thirty-eight Sprague-Dawley rats were randomized into two groups: zoledronic acid (ZA), n = 27, and control (CTRL) n = 11. The ZA group received a weekly IV injection of ZA (100 μg/kg) during 10 weeks. The CTRL group received saline. After 6 weeks, extraction of the right mandibular molars was performed. Rats were sacrificed after 14 weeks. Microtomography characterized bone lesions and vascularization after injection of a radio-opaque material. Raman microspectroscopy evaluated bone mineralization.

RESULTS

Fifty-five percent of ZA rats presented bone exposure and signs of BRONJ. None sign was found at the left hemimandible in the ZA group and in the CTRL group. Vascular density appeared significantly increased in the right hemimandibles of the CTRL group compared to the left hemimandibles. Vascularization was reduced in the ZA group. A significantly increased of the mineral-to-amide ratio was found in the alveolar bone of ZA rats by Raman microspectroscopy.

CONCLUSIONS

In a rat model of BRONJ, microtomography evidenced osteonecrosis in BRONJ. Raman spectroscopy showed an increased mineralization. Vascularization after tooth extraction was impaired by ZA.

CLINICAL RELEVANCE

Prolonged BP administration caused an increase in the mineralization and a quantitative reduction of the vascularization in the alveolar bone; both factors might be involved concomitantly in the BRONJ pathophysiology.

Incidence Rate of Atypical Femoral Fracture after Bisphosphonates Treatment in Korea

BACKGROUND

Atypical femoral fracture (AFF) has been high-lightened, because it was associated with the long-term use of bisphosphonate. Comparing western countries, the incidence rate of AFF was unclear in East Asian patients. Our purposes were to estimate the incidence rate of radiologically defined AFF in Korea, and to determine the association between occurrence of AFF and long-term use of bisphosphonate.

METHODS

We conducted a hospital-based, retrospective cohort study in patients aged ≥ 45 years, who took bisphosphonate. The occurrence of AFF was estimated by using incidence rate, and the age-adjusted incidence rate to U.S. 2010 Census data. The association between occurrence of AFF and the duration of bisphosphonate use was examined. The cumulative probability of AFF was plotted per each duration of bisphosphonate use.

RESULTS

Among 10,338 individuals who took bisphosphonate, 13 patients with AFF following use of bisphosphonate were identified. The incidence rate was 85.9/100,000 person-years (95% confidence interval [CI], 50.2-146.9), and age-adjusted incidence rate was 72.7/100,000 person-years (95% CI, 29.1-175.8). In Poisson regression analysis, higher body mass index (BMI) was associated with an increased risk of AFF (relative risk, 1.2; 95% CI, 1.004-1.359). The cumulative probability of AFF increased abruptly when the duration of bisphosphonate use was 4 years or more.

CONCLUSION

Among Korean patients, the incidence rate of AFF was on a par with those of western countries, and this can provide basic information to conduct further studies by evaluating risk and benefit of continuing bisphosphonate.

A review of atypical subtrochanteric femoral fractures in Northern Ireland between 2010 and 2014

The term atypical femoral fractures most commonly occur in the subtrochanteric area. Concerns exist regarding the role of bisphosphonate treatment in their aetiology. Which surgical intervention provides the best outcome remains contentious. We reviewed all atypical subtrochanteric femoral fractures treated in Northern Ireland over 5 years, specifically investigating incidence, prodromal symptoms, association with bisphosphonates and optimal fixation methods. All subtrochanteric fractures treated in the region were identified and reviewed for atypical features. Case notes and imaging were then reviewed for each patient. A total of 364 subtrochanteric femoral fractures were identified during the 5-year study period. Twenty-six of these met the criteria for an atypical fracture (7%). Thirteen patients (50%) had presented with prodromal symptoms prior to complete fracture, six of which had radiological evidence of an incomplete fracture of the lateral cortex. Thirteen patients had a history of bisphosphonate treatment. All were treated operatively, with twenty-five cephalomedullary nails and one dynamic hip screw. Twenty-one patients had follow-up for greater than 2 months, nine of which (42.9%) achieved radiological union with a mean time to union of 297 days. Dynamically locked nails had a higher union rate than statically locked (80% versus 33.3%). Four patients required major revision surgery (15.4%). The quality of reduction was statistically significant in predicting need for revision. Atypical fractures often present with prodromal symptoms. Complete fractures are difficult to successfully manage with longer than expected times to union. Treatment with a dynamically locked, cephalomedullary with a good reduction provided the best results.

High and pointed type of femoral localized reaction frequently extends to complete and incomplete atypical femoral fracture in patients with autoimmune diseases on long-term glucocorticoids and bisphosphonates

Once a localized reaction (beaking) was detected, discontinuation of bisphosphonates (BPs) and switching to vitamin D supplementation or teriparatide therapy effectively improved its shape. When the localized reaction was high, of the pointed type, and/or accompanied by prodromal pain, the risks of complete and incomplete atypical femoral fracture increased and consideration of prophylactic fixation for such patients was required.

INTRODUCTION

Femoral localized reaction (localized periosteal thickening of the lateral cortex, beaking) is reported to precede atypical femoral fractures (AFFs) and to develop in 8-10% of patients with autoimmune diseases taking BPs and glucocorticoids. The aims of the present study were to retrospectively investigate the shapes of localized reaction to consider how to manage the condition.

METHODS

Twenty femora of 12 patients with autoimmune diseases who were on BPs and glucocorticoids exhibited femoral localized reaction. The heights of localized reaction were measured and the shapes classified as pointed, arched, and other. Localized reaction changes were divided into three categories: deterioration, no change, and improvement. A severe form of localized reaction was defined; this was associated with prodromal pain, de novo complete AFF, or incomplete AFF with a fracture line at the localized reaction.

RESULTS

The mean height of localized reaction was 2.3 ± 0.8 mm (range, 1.0-3.7 mm) and the pointed type was 35%. Localized reaction was significantly higher (3.3 ± 0.8 vs. 2.1 ± 0.7 mm; p = 0.003) and the pointed type more common (78 vs. 27%; p = 0.035) in those with the severe form of localized reaction. Seven patients with localized reactions discontinued BPs just after localized reaction was detected, but five continued on BPs for 2 years. Localized reaction deterioration was more common in patients who continued than discontinued BPs (100 vs. 29%; p = 0.027). After 2 years, all patients had discontinued BPs and localized reaction did not deteriorate further in any patient.

CONCLUSIONS

Once a localized reaction was detected, discontinuation of BPs and switching to vitamin D supplementation or teriparatide therapy effectively improved it. When the localized reaction was high, of the pointed type, and/or accompanied by prodromal pain, the risks of complete and incomplete AFF increased and consideration of prophylactic fixation for such patients was required.

Atypical femoral fractures and current management

With the rapid increase in patients receiving bisphosphonates (BPs) for treating osteoporosis, one of the clinical complications associated with its long-term use is atypical femoral fractures (AFFs). Although the absolute risk for AFFs is low and it was a consensus that AFFs were acceptable compared with the amount of osteoporotic fractures BPs have prevented, epidemiological studies have proved that BPs had a strong association with AFFs and possibly more people were going to suffer from this adverse effect with wide prescriptions of this drug. In addition, AFFs seemed to have impaired ability to heal. Thus, to understand the mechanism(s) behind AFFs is important and desirable for considering preventive measures. This article reviewed the clinical features of AFFs as well as potential underlining pathological characteristics, such as the decreased turnover rate caused by BPs that led to multiple-level alternations, e.g., changes not only at cellular and tissue levels, but also related to changes in bone micro- and macrostructure and organic/inorganic contents, leading to potentially compromised mechanical properties of cortical bone when exposed to prolonged BP therapy. Severely suppressed bone turnover may also be the underlying mechanism for impaired fracture healing in patients with AFFs. The rising concerns about the risk for AFFs in nonosteoporotic patients receiving high-dose BPs to treat cancers were also discussed. Detailed investigation will help develop potential targeted pharmacological treatments such as parathyroid hormone. In addition, potential innovative internal fixation implants were discussed with regard to dynamic and biological fixation for enhancing AFF repair.

Patients Receiving Parenteral Bisphosphonates for Malignant Disease and Having Developed an Atypical Femoral Fracture Are at Risk of Concomitant Osteonecrosis of the Jaw: An Evidence-Based Review

PURPOSE

The risk of developing concomitant medication-related osteonecrosis of the jaw (MRONJ) in patients who have sustained an atypical femoral fracture (AFF) in association with parental administration of a bisphosphonate osteoclastic inhibitor medication for malignant disease is unclear. Published data were searched to determine the prevalence of these concomitant adverse medication events, if any.

MATERIALS AND METHODS

A systematic review of published case series in the PubMed database was undertaken to ascertain the prevalence of patients having a concomitant history of AFF and MRONJ. The data were analyzed to provide prevalence rates of these events from the literature.

RESULTS

Two case series were identified that delineated the risk (25 and 33%, respectively) of concomitant development of MRONJ and AFF in recipients of parenteral bisphosphonate medication administered for malignant disease.

CONCLUSION

The published data suggest that approximately 30% of patients receiving parenteral bisphosphonates and having sustained an AFF could develop comorbid MRONJ.

The cumulative incidence of and risk factors for latent beaking in patients with autoimmune diseases taking long-term glucocorticoids and bisphosphonates

SUMMARY

The incidence of beaking, which has been reported to precede atypical femoral fracture, was high and increased over 2 years in patients with autoimmune diseases who were taking bisphosphonates and glucocorticoids. Regular femoral X-rays are strongly recommended to screen for beaking, and bisphosphonate drug holidays should be considered.

INTRODUCTION

Atypical femoral fractures (AFFs) have been recently recognized as complications associated with bisphosphonate (BP) use. AFFs are considered to be stress fractures; localized periosteal thickening of the lateral cortex is often present at the fracture site; this thickening is termed "beaking." Beaking has been reported to precede AFF. The aims of the present study were to evaluate the incidence of latent beaking in patients with autoimmune diseases taking BPs and glucocorticoids and to identify risk factors for beaking.

METHODS

A total of 125 patients with autoimmune diseases who were taking BPs and glucocorticoids was included; 116 patients underwent X-rays and analysis of serum and urine bone metabolic markers annually for 2 years. Mean patient age was 54.5 years; there were 105 (90.5%) females and the mean duration of disease was 13.2 years. Focal lateral cortical thickening in femoral X-rays was defined as beaking.

RESULTS

Beaking was detected in 15 femora of 10 patients (8.0%) at the time of recruitment. Over the 2-year observation period, the incidence of beaking increased to 21 femora of 12 patients (10.3%), and a complete AFF at the location of beaking occurred in one patient. Beaking was associated with a longer duration of BP treatment (6.1 ± 1.0 years vs. 5.0 ± 2.9 years, p = 0.01). Age 40-60 years, BP therapy ≥4 years, and diabetes mellitus were significantly associated with beaking.

CONCLUSIONS

The incidence of beaking was high, and increased over 2 years, in patients with autoimmune diseases who were taking BPs and glucocorticoids. Regular femoral X-rays are strongly recommended to screen for beaking. Long-term BP/glucocorticoid use was a risk factor for beaking in patients with autoimmune diseases; BP drug holidays should be considered.

A rare case of bilateral proximal femoral insufficiency fractures after interlocking IM nailing for bilateral atypical femoral shaft fractures

Atypical femoral fractures have unique radiologic and clinical feature. Most commonly used fixation method for atypical femoral fracture is interlocking intramedullary (IM) nailing. The aim of this paper is to document a rare case of a 76-year-old female who sustained bilateral proximal femoral insufficiency fractures after conventional interlocking IM nailing for bilateral atypical femoral shaft fractures without taking history of bisphosphonates. We recommend the routine use of full-length reconstruction or cephalomedullary-type interlocking IM nail for atypical femoral fractures.

Atypical Femoral Fracture: 2015 Position Statement of the Korean Society for Bone and Mineral Research

Bisphosphonate (BP) is a useful anti-resorptive agent which decreases the risk of osteoporotic fracture by about 50%. However, recent evidences have shown its strong correlation with the occurrence of atypical femoral fracture (AFF). The longer the patient takes BP, the higher the risk of AFF. Also, the higher the drug adherence, the higher the risk of AFF. It is necessary to ask the patients who are taking BP for more than 3 years about the prodromal symptoms such as dull thigh pain. Simple radiography, bone scan, and magnetic resonance imaging (MRI) are good tools for the diagnosis of AFF. The pre-fracture lesion depicted on the hip dual energy X-ray absorptiometry (DXA) images should not be missed. BP should be stopped immediately after AFF is diagnosed and calcium and vitamin D (1,000 to 2,000 IU) should be administered. The patient should be advised not to put full weight on the injured limb. Daily subcutaneous injection of recombinant human parathyroid hormone (PTH; 1-34) is recommended if the patient can afford it. Prophylactic femoral nailing is indicated when the dreaded black line is visible in the lateral femoral cortex, especially in the subtrochanteric area.