Fracture in Irradiated Rat Femur: A Description of an Experimental Model and Evaluation of its Effectiveness / Fratura em fêmur irradiado de rato: Descrição de um modelo experimental e avaliação de sua eficácia

Abstract Objective We aim to describe an experimental model for studying femoral fractures in rats after exposure to ionizing radiation, demonstrating a way to apply a substance for analysis, the method for patterning fracture and irradiation, and how to evaluate its effectiveness based on radiographic studies. Methods We used 24 rats divided into 2 groups of 12 animals each. The STUDY group was exposed to ionizing radiation and treated with saline solution, and the CONTROL group was not exposed to radiation and was treated with saline solution. All animals were subjected to standardized fracture of the right femur that was fixed with intramedullary wire. The efficiency of the bone union was assessed by radiographic exam. Results Fracture healing was more efficient in bones not exposed to ionizing radiation (p = 0.012). All fractures met the criteria of being simple, diaphyseal, transverse or short oblique. Conclusion The experimental model presented is an efficient alternative for the study of fractures in irradiated bones in rats.

Resumo Objetivo Nosso objetivo é descrever um modelo experimental para estudo de fraturas de fêmur em ratos após exposição a radiação ionizante, demonstrando uma forma de aplicação de uma substância para análise, o método de padronização de fratura e irradiação e a forma de avaliação de sua eficácia com base em estudos radiográficos. Métodos Utilizamos 24 ratos divididos em dois grupos de 12 animais cada. O grupo ESTUDO foi exposto à radiação ionizante e tratado com soro fisiológico, enquanto o grupo CONTROLE não foi exposto à radiação e foi tratado com soro fisiológico. Todos os animais foram submetidos à fratura padronizada do fêmur direito e sua fixação com fio intramedular. A eficácia da consolidação óssea foi determinada por exame radiográfico. Resultados A cicatrização de fraturas foi mais eficiente em ossos não expostos à radiação ionizante (p = 0,012). Todas as fraturas atenderam aos critérios de serem simples, diafisárias, transversas ou oblíquas curtas. Conclusão O modelo experimental apresentado é uma boa alternativa para o estudo de fraturas em ossos irradiados em ratos.

Acute Presentation of a High-Grade Myxofibrosarcoma Originating in the Thoracic Wall: A Case Report.

We report the first case of a patient with myxofibrosarcoma (MFS) who presented acutely with a rib fracture and developed a rapidly expanding loculated hemothorax after chest trauma. The patient was taken to the operating room for evacuation of hemothorax, and samples and biopsy specimens were taken for cytologic and pathologic examination. Final report with immunohistochemical staining showed a high-grade MFS. After the procedure, there was clinical and radiological improvement, and the patient was followed up as an outpatient. Myxofibrosarcoma is a very rare and aggressive connective tissue neoplasm with variable presentations. Surgical resection is the preferred treatment. Prompt diagnosis and adequate management of these tumors are important to reduce their high local recurrence and distant metastasis rates. Therefore, it is important to be aware of its common and uncommon presentations.

Multidisciplinary management of solitary hypervascular metastatic recurrence of renal cell carcinoma presenting with pathological femoral fracture.

Renal cell carcinoma (RCC) frequently presents with osseous metastasis, predominantly lytic and prone to pathological fracture. The metastatic lesion in the extremity presents with local swelling, pain and immobility due to pathological fracture. The solitary or oligometastatic lesions should be treated with curative intent, which can help the patient to lead a more prolonged and disability-free life. The RCCs and their metastases are hypervascular with an exuberant arterial supply. Surgery can lead to uncontrolled life-threatening haemorrhage. Preoperative transarterial embolisation reduces tumour vascularity significantly and reduces intraoperative blood loss. We present a 46-year-old male patient with solitary hypervascular metastatic recurrence of RCC with a pathological femoral fracture with an infeasible initial surgery due to profuse haemorrhage. He was successfully treated by preoperative transarterial embolisation, followed by surgical resection and implantation of a megaprosthesis. Multidisciplinary management reduces patient morbidity and mortality with successful treatment in solitary hypervascular metastasis from RCC.

Evaluation of different treatment modalities for fractured and non-fractured simple bone cyst: A single-center review of 68 patients.

ABSTRACT: Simple bone cysts (SBCs) occur most frequently in the proximal aspect of the humerus and femur in growing age and are associated with intercurrent pathological fractures in up to 87%. Therapeutic management of SBCs remains controversial. The aim of this study was to examine the outcome of conservative and various surgical treatment modalities considering the specific anatomic location and integrity of the SBC.In this retrospective study, we analyzed 68 cases of SBCs who underwent a conservative or surgical treatment between 2009 and 2020 with a mean follow-up of 30.1 months. The epidemiological characteristics, complications, clinical, and radiographic outcome after conservative or surgical treatment were assessed.The study includes 50 male (73.5%) and 18 female (26.5%) patients with a mean age of 9.1 years. The most common locations were the proximal humerus (69.2%, n = 47) and femur (16.2%, n = 11). In 43 cases (63.2%; upper limb n = 40, lower limb n = 3) a pathological fracture occurred. Fifty patients (73.5%; upper limb n = 40, lower limb n = 10) underwent a conservative treatment. In 11 cases (16.2.1%; upper limb n = 4, lower limb n = 7) an intralesional curettage and defect reconstruction with bone substitute without stabilization were performed. Five patients (7.3%; upper limb n = 4, lower limb n = 1) received an osteosynthesis, in two cases (2.9%; upper limb 1; lower limb 1) combined with an intralesional curettage and defect reconstruction with bone substitute. All 32 pathological fractures treated conservatively (upper limb n = 31, lower limb n = 1) healed within 6 weeks; 17/43 patients (39.5%) suffered at least one second fracture. After intralesional curettage and defect reconstruction with bone substitute local recurrence was observed in 5/13 cases (38.5%). Spontaneous consolidation, at least partially, was observed in three cases (4.4%) following conservative treatment after fracture. No relevant secondary angular or torsional deformity was observed after treatment.The majority of SBCs can be treated conservatively, especially in the upper extremity. However, if a fracture is completely dislocated, joint affecting, unstable or open, surgical treatment is necessary. Load-dependent pain or the inability to mobilize timely after fracture can necessitate surgical treatment in SBCs affecting the lower extremity. Spontaneous resolution, especially after fracture, can be seen in rare cases.

Safety and Efficacy of Multilevel Thoracolumbar Vertebroplasty in the Simultaneous Treatment of Six or More Pathologic Compression Fractures.

PURPOSE: To assess the safety and efficacy of multilevel thoracolumbar vertebroplasty in the simultaneous treatment of ≥ 6 painful pathologic compression fractures. MATERIALS AND METHODS: Retrospective review was conducted of 50 consecutive patients treated with vertebroplasty for ≥ 6 pathologic compression fractures in a single session for pain palliation at a tertiary single cancer center from 2015 to 2019. Outcomes measured included procedural safety according to Common Terminology Criteria for Adverse Events (CTCAE), change in 4-week postprocedure back pain by numeric rating scale (NRS), comparison of daily opioid medication consumption, and development of skeletal-related events. RESULTS: A total of 397 pathologic compression fractures were treated during 50 sessions (mean, 7.9 per patient ± 1.5). Mean procedure duration was 162 minutes ± 35, mean postoperative hospitalization duration was 1.6 days ± 0.9, and mean follow-up duration was 401 days ± 297. Seven complications were recorded, including 1 case of symptomatic polymethyl methacrylate pulmonary embolism. No major complications (CTCAE grade 4/5) were reported. NRS pain score was significantly decreased (5.0 ± 1.8 vs 1.7 ± 1.4; P < .0001), with a mean score decrease of 3.3 points (66%). Opioid agent use decreased significantly (76 mg/24 h ± 42 vs 45 mg/24 h ± 37; P = .0003), with a mean decrease of 30 mg/24 h (39%). Skeletal-related events occurred in 7 patients (14%). CONCLUSIONS: Multilevel vertebroplasty for ≥ 6 pathologic compression fractures is safe and provides significant palliative benefit when performed simultaneously.

Interventional radiology for treatment of bone metastases.

Therapeutic advances in oncology have led to longer survival in many forms of cancer, including those complicated by bone metastases. When a bone metastasis is painful or when there is a risk of fracture, interventional radiology procedures can be carried out for pain control and/or stabilisation. All of these techniques can be performed under local anaesthesia. Cementoplasty and vertebroplasty are stabilisation procedures consisting in the percutaneous injection of acrylic cement into a lytic bone lesion. The effect on pain can be explained by the consolidation of weakened, fractured or pre-fractured bone, but also to a lesser extent by the toxic, chemical and thermal effect of the cement. Tumour ablation techniques include alcoholisation or thermal ablation (by heat with radiofrequency and microwave or cold by cryoablation). Percutaneous thermal ablation of bone tumours is most often performed as a palliative measure resulting in a significant and lasting reduction in symptoms. Radiofrequency ablation consists in placing needles through which an electrical current passes. Microwave ablation acts by causing very high frequency vibrations of water molecules. Cryoablation releases argon gas at the tip of the needle, forming an "ice ball" effectively destroying tumour cells. Any of these techniques can be combined to radiation therapy, performed before or after radiation. Finally, tumour embolisation can have a goal of pain control, or preparation of surgery to reduce the risk of peroperative haemorrhage.

Osteoporosis Management in the Era of COVID-19.

Osteoporosis is a chronic condition that reflects reduced bone strength and an associated increased risk for fracture. As a chronic condition, osteoporosis generally requires sustained medical intervention(s) to limit the risks for additional bone loss, compromise of skeletal integrity, and fracture occurrence. Further complicating this issue is the fact that the abrupt cessation of some therapies can be associated with an increased risk for harm. It is in this context that the COVID-19 pandemic has brought unprecedented disruption to the provision of health care globally, including near universal requirements for social distancing. In this Perspective, we provide evidence, where available, regarding the general care of patients with osteoporosis in the COVID-19 era and provide clinical recommendations based primarily on expert opinion when data are absent. Particular emphasis is placed on the transition from parenteral osteoporosis therapies. It is hoped that these recommendations can be used to safely guide care for patients with osteoporosis until a return to routine clinical care standards is available. © 2020 American Society for Bone and Mineral Research.

External Validation of PATHFx Version 3.0 in Patients Treated Surgically and Nonsurgically for Symptomatic Skeletal Metastases.

BACKGROUND: PATHFx is a clinical decision-support tool based on machine learning capable of estimating the likelihood of survival after surgery for patients with skeletal metastases. The applicability of any machine-learning tool depends not only on successful external validation in unique patient populations but also on remaining relevant as more effective systemic treatments are introduced. With advancements in the treatment of metastatic disease, it is our responsibility to patients to ensure clinical support tools remain contemporary and accurate. QUESTION/PURPOSES: Therefore, we sought to (1) generate updated PATHFx models using recent data from patients treated at one large, urban tertiary referral center and (2) externally validate the models using two contemporary patient populations treated either surgically or nonsurgically with external-beam radiotherapy alone for symptomatic skeletal metastases for symptomatic lesions. METHODS: After obtaining institutional review board approval, we collected data on 208 patients undergoing surgical treatment for pathologic fractures at Memorial Sloan Kettering Cancer Center between 2015 and 2018. These data were combined with the original PATHFx training set (n = 189) to create the final training set (n = 397). We then created six Bayesian belief networks designed to estimate the likelihood of 1-month, 3-month, 6-month, 12-month, 18-month, and 24-month survival after treatment. Bayesian belief analysis is a statistical method that allows data-driven learning to arise from conditional probabilities by exploring relationships between variables to estimate the likelihood of an outcome using observed data. For external validation, we extracted the records of patients treated between 2016 and 2018 from the International Bone Metastasis Registry and records of patients treated nonoperatively with external-beam radiation therapy for symptomatic skeletal metastases from 2012 to 2016 using the Military Health System Data Repository (radiotherapy-only group). From each record, we collected the date of treatment, laboratory values at the time of treatment initiation, demographic data, details of diagnosis, and the date of death. All records reported sufficient follow-up to establish survival (yes/no) at 24-months after treatment. For external validation, we applied the data from each record to the new PATHFx models. We assessed calibration (calibration plots), accuracy (Brier score), discriminatory ability (area under the receiver operating characteristic curve [AUC]). RESULTS: The updated PATHFx version 3.0 models successfully classified survival at each time interval in both external validation sets and demonstrated appropriate discriminatory ability and model calibration. The Bayesian models were reasonably calibrated to the Memorial Sloan Kettering Cancer Center training set. External validation with 197 records from the International Bone Metastasis Registry and 192 records from the Military Health System Data Repository for analysis found Brier scores that were all less than 0.20, with upper bounds of the 95% confidence intervals all less than 0.25, both for the radiotherapy-only and International Bone Metastasis Registry groups. Additionally, AUC estimates were all greater than 0.70, with lower bounds of the 95% CI all greater than 0.68, except for the 1-month radiotherapy-only group. To complete external validation, decision curve analysis demonstrated clinical utility. This means it was better to use the PATHFx models when compared to the default assumption that all or no patients would survive at all time periods except for the 1-month models. We believe the favorable Brier scores (< 0.20) as well as DCA indicate these models are suitable for clinical use. CONCLUSIONS: We successfully updated PATHFx using contemporary data from patients undergoing either surgical or nonsurgical treatment for symptomatic skeletal metastases. These models have been incorporated for clinical use on PATHFx version 3.0 (https://www.pathfx.org). Clinically, external validation suggests it is better to use PATHFx version 3.0 for all time periods except when deciding whether to give radiotherapy to patients with the life expectancy of less than 1 month. This is partly because most patients survived 1-month after treatment. With the advancement of medical technology in treatment and diagnosis for patients with metastatic bone disease, part of our fiduciary responsibility is to the main current clinical support tools. LEVEL OF EVIDENCE: Level III, therapeutic study.

Percutaneous microwave ablation with osteoplasty and interventional internal fixation for impending pathologic fracture of the proximal humerus.

Humerus is the long bone second-most commonly affected by metastases. An impending pathologic humeral fracture requires rigid surgical stabilization to prevent it from fully fracturing. In the present study, we report a case of a 71-year-old male patient with a visual analog score of 10 (indicating extreme pain) and an impending pathologic fracture that allowed for combined treatment with percutaneous microwave ablation and simultaneous injection of bone cement during Kirschner wire insertion. The procedure was performed successfully with no complications. The patient reported pain relief and improved quality of life and functional status 1 day, 7 days, 1 month, and 2 months after his procedure.

Current Trends and Variations in the Treatment of Unicameral Bone Cysts of the Humerus: A Survey of EPOS and POSNA Members.

BACKGROUND: A variety of treatment methods have so far been described for unicameral bone cysts (UBC). However, to the best of our knowledge, no particular consensus has yet been reached on when to operatively treat a patient with a humeral UBC. Therefore, members of the European Pediatric Orthopedic Society (EPOS) and Pediatric Orthopedic Society of North America (POSNA) were surveyed to characterize current treatment preferences. METHODS: An online electronic questionnaire was sent out to all registered EPOS and POSNA members. The survey comprised 45 questions related to the diagnosis, treatment, and follow-up characteristics of patients with UBCs of the humerus. Particular questions related to the nonoperative or surgical treatment of pathologic proximal humerus and humeral shaft fractures were also included. RESULTS: In total, 444 participants (132 EPOS and 292 POSNA members) responded, of whom 400 were actively involved in UBC treatment. The preferred diagnostic modalities to confirm the diagnosis of a UBC in the humerus were radiographs (88%), MRI in cases of questionable diagnosis (58%) or CT scan (8%). For painless UBCs 67% prefer no treatment at all except when the fracture risk is deemed high (then 53% recommend surgery); 71% of respondents would treat painful UBCs with surgery. Most common surgical techniques comprise curettage (45%), artificial bone substitutes (37%), corticosteroid injection (29%), or intramedullary stabilization (eg, rodding; 24%).Fractured, nondisplaced and mildly displaced proximal humerus UBCs and mildly displaced pathologic humerus shaft fractures are all preferably treated nonoperatively (94%, 91%, 83%, respectively). Severely displaced pathologic proximal humerus fractures are treated less often conservatively (36%) than surgically (40%), and severely displaced humerus shaft fractures are preferably treated surgically (63%) by intramedullary stabilization (60%). CONCLUSIONS: There is great variation among EPOS and POSNA members with regards to the diagnosis and treatment of UBCs in the humerus. Although some consensus on general treatment principles is seen, specific surgical treatment indications vary.Prospective randomized-controlled studies are needed to evaluate the outcomes of the different surgical approaches compared with nonoperative strategies. LEVEL OF EVIDENCE: Level V-expert opinion.

A Specialized Orthosis for Suppressing Bony Destruction from Multiple Myeloma and to Enhance Healing of a Pathologic Fracture in an Appendicular Lesion.

Appendicular metastasis from multiple myeloma (MM) frequently presents with a pathologic fracture. In this case report, a patient with a long history of MM and an associated pathologic fracture was treated using a specialized brace. This orthosis uses a deforming element to asymmetrically increase the soft tissue pressure around the pathologic fracture. The patient experienced rapid pain relief and bony healing without surgical intervention.

Pathological fracture of non-ossifying fibroma associated with neurofibromatosis type 1.

We report the management of a pathological fracture through a proximal tibial non-ossifying fibroma (NOF) in a 13-year-old girl with neurofibromatosis type 1 (NF1). The fracture was minimally displaced, and the lesion had clinical features of a NOF, and therefore biopsy was not required. Operative fixation has been the preferred method of treatment for pathological fractures through NOF associated with NF1. Multiple NOFs associated with NF1 are rare but can coalesce resulting in large lesions with an increased risk of pathological fracture. In cases which permit, non-operative treatment with cast immobilisation can yield satisfactory results.

Successful treatment of pathologic femoral shaft fracture associated with large arteriovenous malformations using a 3-dimensional external fixator and teriparatide: a case report.

BACKGROUND: Arteriovenous malformations (AVMs) are rare congenital vascular lesions associated with early quiescence, late expansion, and, ultimately, infiltration and destruction of local soft tissue and bone. The extremities are a common location. Incidence of bony involvement by AVM has been reported as high as 31%. However, there are few reports on management of pathologic fracture associated with AVM. Teriparatide is a recombinant parathyroid hormone (PTH) analogue consisting of the 1-34 fragment of PTH. Recently, some reports have shown the ability of teriparatide to improve fracture healing. Here, we present a case of pathologic femoral shaft fracture associated with large AVMs that was treated successfully by external fixation and teriparatide. CASE PRESENTATION: A 68-year-old Japanese woman, previously diagnosed as having large AVMs, sustained a right femoral shaft fracture due to a fall. At the time of admission, she presented with massive swelling and venous varicosities of the right thigh. Plain radiography of the right thigh revealed femoral shaft fracture with bony erosion and calcification of soft tissue. We planned closed reduction and intramedullary nailing with a unilateral external fixator following embolization of the feeding artery. However, closed reduction using the fracture table was difficult. When we attempted open reduction, massive bleeding (1000 mL) after incision of subcutaneous tissue occurred. Finally, we carefully applied a Taylor Spatial Frame. Fracture displacement was corrected successfully and bony union was obtained with administration of teriparatide 15 months after the initial surgery. The patient is able to walk using 1 cane. CONCLUSION: We present the first report of pathologic fracture associated with large AVMs that achieved bony union using a 3-dimensional external fixator and teriparatide.

Magnetic resonance imaging of subchondral insufficiency fractures of the lower limb.

Subchondral insufficiency fracture (SIF) is a non-traumatic condition that has historically been associated with elderly, osteoporotic women and patients with systemic conditions. There has been much work done to determine the pathogenesis of SIF, which has previously been regarded as idiopathic, rapid-progressive osteoarthritis or osteonecrosis of the hip, spontaneous osteonecrosis of the knee (SONK), osteochondral defect (OCD) of the talus and adult-onset Freiberg infraction of the metatarsal head. Early diagnosis and management are crucial to prevent subchondral collapse, secondary osteonecrosis and early-onset osteoarthritis. Magnetic resonance imaging (MRI) plays an important role in the diagnosis of SIF, which is often inconspicuous on initial radiographs. In this article, the authors provide an update on the role of MRI in identifying key imaging features of SIF in various joints of the lower limb to aid in its correct diagnosis.

Practical Input on Bone Tumor Imaging: Pathological Fracture, Risk Features, and When to Contact Orthopaedics.

Awareness of risk factors associated with impending fracture and its radiologic appearance allows early diagnosis, supports prophylactic surgical treatment, and prevents the multiple complications of a pathologic fracture. Because the femur is the most common long bone affected by metastatic bone lesions, we address this clinically relevant site in this review. The key to early detection of risky bone lesions is familiarity with the possible clinical presentation, biomechanical effects of the anatomical site (femoral head and neck, intertrochanteric zone, proximal diaphysis), and the lesion types (lytic, blastic, or mixed). Awareness of the possible treatment strategies depending on the characteristics just listed allows high-quality targeted reporting.

Delayed, Atraumatic Index Metacarpal Fracture After Trapeziectomy and Suture-Button Suspensionplasty for Thumb Carpometacarpal Osteoarthritis: A Report of Three Cases.

Trapeziectomy with suture-button suspensionplasty is a surgical treatment option for thumb carpometacarpal osteoarthritis refractory to nonsurgical management. We describe the cases of 3 patients who presented with index metacarpal fracture, in the absence of traumatic injury, over 4 months after trapeziectomy with suture-button suspensionplasty. All 3 fractures demonstrated the same pattern: short oblique/spiral, oriented proximal radial to distal ulnar with the distal end in the vicinity of the index metacarpal button, presumably after the orientation of the metacarpal drill hole. Two of the fractures were treated with surgical fixation. Fracture healing was obtained in all cases. Two of the 3 patients remained symptomatic with thumb pain, but decided against revision treatment for the carpometacarpal osteoarthritis. The third underwent restabilization of the suture button at the time of fracture fixation. Although uncommon, index metacarpal fracture after trapeziectomy with suture-button suspensionplasty can present without trauma several months after surgery.

Epidemiology, Therapeutic Strategies, Outcomes, and Complications of Pathologic Fractures.

Much can be learned about the epidemiology of metastatic disease of bone through large databases. Secondary data analyses add substantial knowledge of the incidence, prevalence, cost, complications, risk factors, and treatment variability by using modern statistical methods in a large patient cohort. Investigators must be aware of the intentions of these data sources as well as the limitations in any conclusions drawn. Large databases are primarily beneficial in generating hypotheses and will likely continue to be an important source of information. For the general orthopaedist, surgical management of metastatic skeletal disease can be a challenging problem with many potential risks. Complications are often encountered and can be influenced by the patient's medical conditions, stage of disease, and the selected surgical procedure. Patients diagnosed with skeletal metastases are often at higher risk of having perioperative complications, such as infection and thromboembolism, than is the general population. A case-based approach highlights potential risks with examples of common scenarios that can arise.

Proceedings of the 2018 Santa Fe Bone Symposium: Advances in the Management of Osteoporosis.

The Santa Fe Bone Symposium is an annual meeting devoted to clinical applications of recent advances in skeletal research. The 19th Santa Fe Bone Symposium convened August 3-4, 2018, in Santa Fe, New Mexico, USA. Attendees included physicians of many specialties, fellows in training, advanced practice providers, clinical researchers, and bone density technologists. The format consisted of lectures, case presentations by endocrinology fellows, and panel discussions, with all involving extensive interactive discussions. Topics were diverse, including an evolutionary history of calcium homeostasis, osteoporosis treatment in the very old, optimizing outcomes with orthopedic surgery, microbiome and bone, new strategies for combination and sequential therapy of osteoporosis, exercise as medicine, manifestations of parathyroid hormone excess and deficiency, parathyroid hormone as a therapeutic agent, cell senescence and bone health, and managing patients outside clinical practice guidelines. The National Bone Health Alliance conducted a premeeting on development of fracture liaison services. A workshop was devoted to Bone Health TeleECHO (Bone Health Extension for Community Healthcare Outcomes), a strategy of ongoing medical education for healthcare professions to expand capacity to deliver best practice skeletal healthcare in underserved communities and reduce the osteoporosis treatment gap.

Imaging Features and Management of Stress, Atypical, and Pathologic Fractures.

Traumatic and atraumatic fractures are entities with distinct but often overlapping clinical manifestations, imaging findings, and management protocols. This article is a review of terminology, etiology, and key imaging features that affect management of atraumatic fractures including stress fractures, atypical femoral fractures, and pathologic fractures. The terminology of atraumatic fractures is reviewed, with an emphasis on the distinctions and similarities of stress, atypical, and pathologic fractures. The basic biomechanics of normal bone is described, with an emphasis on the bone remodeling pathway. This framework is used to better convey the shared etiologies, key differences, and important imaging findings of these types of fractures. Next, the characteristic imaging findings of this diverse family of fractures is discussed. For each type of fracture, the most clinically relevant imaging features that guide management by the multidisciplinary treatment team, including orthopedic surgeons, are reviewed. In addition, imaging features are reviewed to help discriminate stress fractures from pathologic fractures in patients with challenging cases. Finally, imaging criteria to risk stratify an impending pathologic fracture at the site of an osseous neoplasm are discussed. Special attention is paid to fractures occurring in the proximal femur because the osseous macrostructure and mix of trabecular and cortical bone of the proximal femur can function as a convenient framework to understanding atraumatic fractures throughout the skeleton. Atraumatic fractures elsewhere in the body also are used to illustrate key imaging features and treatment concepts. ©RSNA, 2018.