Unexpected Artifact on 99mTc-Methylene Diphosphonate Bone Scintigraphy

Asymmetric hot spots in the axial skeleton on bone scintigraphy may confound diagnosis. We describe an unexpected artifact of 99mTc-methylene diphosphonate near the breast in a 55-y-old woman with breast cancer. The initial whole-body bone scintigraphy revealed a solitary focal lesion in the anterior ribs on the left side. After careful tracking, we determined that this hot spot originated from the adhesive bandage. The patient had placed it in her left front pocket after removing it from the injection site. She was rescanned after the bandage had been removed from her pocket.

Bone and soft tissue tumors at the borderlands of malignancy

This review examines findings of musculoskeletal neoplasms whose equivocal imaging and/or histopathologic features make it difficult to determine if they will show aggressive behavior. We include both intermediate tumors as defined by the World Health Organization (WHO), and a single low-grade malignancy, low-grade central osteosarcoma, which mimics a benign lesion on imaging and histology. Intermediate tumors are a broad category and are subdivided into tumors that have risk of local recurrence only, and ones that have a risk of distant limb and pulmonary metastases. Difficult intermediate musculoskeletal lesions include atypical cartilaginous tumor/grade 1 chondrosarcoma, atypical lipomatous tumor/grade 1 liposarcoma, and solitary fibrous tumor. We review diagnostic criteria, differential diagnosis, and recommendations for surveillance.

Beyond the abdominal and pelvic cavity: abdominal wall and spinal "Aunt Minnies"

Abdominal wall and spinal soft tissue findings are frequently encountered on CT or MR imaging of the abdomen and pelvis. Many of these entities have specific imaging findings, for which a definitive diagnosis can be made without the need for further work up. These abdominal wall and spinal findings may be diagnostically challenging for sub-specialized abdominal radiologists who are unfamiliar with their appearance and appropriate management. This review article describes and illustrates pathognomonic or characteristic abdominal wall and spinal pathologies, which reside outside the abdominopelvic cavity. The cases selected all have findings that allow a confident diagnosis without further imaging or intervention. The cases presented include myonecrosis, intramuscular abscess, myositis, iliopsoas bursitis, Morel-Lavallée lesion, hydrocele of canal of Nuck, Klippel Trenaunay Weber syndrome, neurofibroma with target sign, perineural cysts, filum terminale lipoma, calvarial bone flap, transverse rectus abdominis muscle (TRAM) flap, liposuction, and hidradenitis suppurativa, among others. Although not all-encompassing, this paper will help abdominal radiologists to accurately diagnose a variety of abdominal and pelvic extra-cavitary soft tissue pathologies by identifying key radiologic findings.

A Retrospective Analysis of Sternal Lesions Detected on Breast MRI in Patients Without History of Cancer

OBJECTIVE

To determine the imaging characteristics and stability over time of sternal lesions identified on breast MRI in patients without history of cancer.

METHODS

An IRB-approved retrospective analysis of all breast MRIs performed at our institution from September 1, 2017 to December 1, 2021 that included one of several key words related to the sternum. Studies with history of non-dermatologic malignancy including breast cancer, absence of a true sternal lesion, or presence of symptoms during the examination were excluded. Imaging was reviewed for size, distribution, signal characteristics, and presence of contrast enhancement, perilesional edema, periosteal edema, or intralesional fat. Available comparison imaging, clinical history, and follow-up recommendations were reviewed. Descriptive statistics were used to summarize lesion data.

RESULTS

Of 60 lesions included from 60 patients, 40 lesions with more than two years of comparison imaging were either stable or decreased in size and none demonstrated change in signal characteristics. The majority of these presumed benign lesions demonstrated hypointense signal on T1-weighted sequences (21/40, 52.5%), hyperintense signal on fluid-sensitive sequences (33/40, 82.5%), contrast enhancement (32/40, 80.0%), and absence of clear intralesional fat (29/40, 72.5%). One patient who did not have comparison imaging was diagnosed with malignancy (multiple myeloma) eight months following their MRI. This lesion demonstrated uniquely diffuse and heterogeneous enhancement but did not undergo biopsy.

CONCLUSION

Sternal lesions in women without history of non-dermatologic malignancy have a very low likelihood of malignancy. Common imaging characteristics of the presumed benign lesions can inform imaging recommendations when incidental sternal lesions are discovered.

Incidental chest findings on coronary CT angiography: a pictorial essay and management proposal

Many health systems have been using coronary CT angiography (CCTA) as a first-line examination for ischaemic heart disease patients in various countries. The rising number of CCTA examinations has led to a significant increase in the number of reported incidental extracardiac findings, mainly in the chest. Pulmonary nodules are the most common incidental findings on CCTA scans, as there is a substantial overlap of risk factors between the population seeking to exclude ischaemic heart disease and those at risk of developing lung cancer (i.e., advanced age and smoking habits). However, most incidental findings are clinically insignificant and actively pursuing them could be cost-prohibitive and submit the patient to unnecessary and potentially harmful examinations. Furthermore, there is little consensus regarding when to report or actively exclude these findings and how to manage them, that is, when to trigger an alert or to immediately refer the patient to a pulmonologist, a thoracic surgeon or a multidisciplinary team. This pictorial essay discusses the current literature on this topic and is illustrated with a review of CCTA scans. We also propose a checklist organised by organ and system, recommending actions to raise awareness of pulmonologists, thoracic surgeons, cardiologists and radiologists regarding the most significant and actionable incidental findings on CCTA scans.

Contribution of positron emission tomography/magnetic resonance imaging in musculoskeletal malignancies

Positron emission tomography/computed tomography (PET/CT) is a promising hybrid imaging technique for evaluating musculoskeletal malignancies. Both technologies, independently are useful for evaluating this type of tumors. PET/MR has great potential combining metabolic and functional imaging PET with soft tissue contrast and multiparametric sequences of MR. In this paper we review the existing literature and discuss the different protocols, new available radiotracers to conclude with the scarce evidence available the most useful/probable indications of the PET MR for the for musculoskeletal malignancies.

Society of Skeletal Radiology- white paper. Guidelines for the diagnostic management of incidental solitary bone lesions on CT and MRI in adults: bone reporting and data system (Bone-RADS)

The purpose of this article is to present algorithms for the diagnostic management of solitary bone lesions incidentally encountered on computed tomography (CT) and magnetic resonance (MRI) in adults. Based on review of the current literature and expert opinion, the Practice Guidelines and Technical Standards Committee of the Society of Skeletal Radiology (SSR) proposes a bone reporting and data system (Bone-RADS) for incidentally encountered solitary bone lesions on CT and MRI with four possible diagnostic management recommendations (Bone-RADS1, leave alone; Bone-RADS2, perform different imaging modality; Bone-RADS3, perform follow-up imaging; Bone-RADS4, biopsy and/or oncologic referral). Two algorithms for CT based on lesion density (lucent or sclerotic/mixed) and two for MRI allow the user to arrive at a specific Bone-RADS management recommendation. Representative cases are provided to illustrate the usability of the algorithms.

Common Skeletal Neoplasms and Nonneoplastic Lesions at 18F-FDG PET/CT

Numerous primary and metastatic osseous lesions and incidental osseous findings are encountered at fluorine 18 (¹⁸F) fluorodeoxyglucose (FDG) PET/CT. These lesions show varying degrees of FDG uptake. Malignancies are generally more FDG avid than are benign lesions, but many exceptions exist. Although aggressive lesions tend to be more FDG avid than nonaggressive lesions, this concept holds true particularly for lesions of the same histologic subtype. In addition, some benign osseous processes such as Paget disease have variable degrees of FDG avidity on the basis of disease metabolic activity. This creates a diagnostic dilemma for radiologists and clinicians, especially in patients with known malignancies, and can result in unnecessary diagnostic imaging or interventions for incidental osseous lesions. Evaluation of morphologic CT characteristics of osseous lesions at FDG PET/CT can be a valuable adjunct to metabolic analysis to further characterize lesions, enhance diagnostic and staging accuracy, and avoid unnecessary invasive biopsy procedures. The authors review the common primary and metastatic bone lesions at FDG PET/CT, with an emphasis on morphologic CT assessment of lesions to help narrow the differential diagnosis. Imaging manifestations of common incidental nonneoplastic bone lesions at FDG PET/CT are discussed to provide information on differentiation of these lesions from osseous neoplasms. The guidelines of the National Comprehensive Cancer Network (NCCN) for common primary osseous malignancies are also summarized. Online supplemental material is available for this article. ^©RSNA, 2021.

Apparent diffusion coefficient (ADC): A potential in vivo biological surrogate of the incidentally discovered bone lesions at 3T MRI

PURPOSE

To probe the potential of apparent diffusion coefficient (ADC) to rectify the incidentally detected bone lesion on MRI into benign or malignant lesions.

MATERIALS AND METHODS

We retrospectively recruited 44 patients (24 males and 20 females); with 52 bone lesions, who underwent diffusion weighted (DW) imaging using multiple b-values on 3 T MRI. ADC maps were derived and analyzed by two radiologists; blinded to the final diagnosis. The mean ADC values were used for statistical analyses. The diagnosis was deduced by histopathological confirmation; in 32 lesions and strict clinical and imaging follow-up for at least 12 months; in 20 lesions.

RESULTS

The mean ADC value (mean±SD) of all malignant tumors (including cartilaginous neoplasms) was [0.92 ± 0.40] × 10-3 mm2/s. This significantly differed from those of both primary benign tumors [1.14 ± 0.24] × 10-3 mm2/s, (p = 0.011), and all non-malignant lesions collectively [1.29 ± 0.44] × 10-3 mm2/s, (p < 0.001). Using mADC value of ≤ 1.1 × 10-3 mm2/s resulted in 86.1% sensitivity and 62.5% specificity for characterizing a lesion as a malignant. The inter-rater reliability was almost perfect (95% CI = 0.954-0.985).

CONCLUSION

ADC could be a non-invasive in-vivo surrogate that may be able to discern the incidentally discovered osseous lesions into benign and malignant pathologies and guide further diagnostic workup.

Diagnosis of bone metastases in breast cancer: Lesion-based sensitivity of dual-time-point FDG-PET/CT compared to low-dose CT and bone scintigraphy

We compared lesion-based sensitivity of dual-time-point FDG-PET/CT, bone scintigraphy (BS), and low-dose CT (LDCT) for detection of various types of bone metastases in patients with metastatic breast cancer. Prospectively, we included 18 patients with recurrent breast cancer who underwent dual-time-point FDG-PET/CT with LDCT and BS within a median time interval of three days. A total of 488 bone lesions were detected on any of the modalities and were categorized by the LDCT into osteolytic, osteosclerotic, mixed morphologic, and CT-negative lesions. Lesion-based sensitivity was 98.2% (95.4-99.3) and 98.8% (96.8-99.5) for early and delayed FDG-PET/CT, respectively, compared with 79.9% (51.1-93.8) for LDCT, 76.0% (36.3-94.6) for BS, and 98.6% (95.4-99.6) for the combined BS+LDCT. BS detected only 51.2% of osteolytic lesions which was significantly lower than other metastatic types. SUVs were significantly higher for all lesion types on delayed scans than on early scans (P<0.0001). Osteolytic and mixed-type lesions had higher SUVs than osteosclerotic and CT-negative metastases at both time-points. FDG-PET/CT had significantly higher lesion-based sensitivity than LDCT and BS, while a combination of the two yielded sensitivity comparable to that of FDG-PET/CT. Therefore, FDG-PET/CT could be considered as a sensitive one-stop-shop in case of clinical suspicion of bone metastases in breast cancer patients.

Salvage therapy for prostate cancer after radical prostatectomy

More than 40% of men with intermediate-risk or high-risk prostate cancer will experience a biochemical recurrence after radical prostatectomy. Clinical guidelines for the management of these patients largely focus on the use of salvage radiotherapy with or without systemic therapy. However, not all patients with biochemical recurrence will go on to develop metastases or die from their disease. The optimal pre-salvage therapy investigational workup for patients who experience biochemical recurrence should, therefore, include novel techniques such as PET imaging and genomic analysis of radical prostatectomy specimen tissue, as well as consideration of more traditional clinical variables such as PSA value, PSA kinetics, Gleason score and pathological stage of disease. In patients without metastatic disease, the only known curative intervention is salvage radiotherapy but, given the therapeutic burden of this treatment, importance must be placed on accurate timing of treatment, radiation dose, fractionation and field size. Systemic therapy also has a role in the salvage setting, both concurrently with radiotherapy and as salvage monotherapy.

An Unexpected Location of Enostosis, a Pediatric "Never Mind" Bone Lesion

Enostoses, also known as bone islands, are common benign sclerotic bone lesion that usually represent incidental findings. They constitute a small focus of compact bone within cancellous bone. Enostoses can be seen on radiographs, CT, and MRI, and are considered one of the skeletal do not touch lesions.

Prostate adenocarcinoma with osteolytic metastases: Case report and review of the literature

Prostate cancer is one of the most common malignancies among males and commonly metastasizes to bone in advanced stages. Although such osseous metastases are typically osteoblastic, osteolytic lesions are also seen. Here, we present a case of an 81-year-old male with known prostate cancer who presented due to a pathologic right humerus fracture. After skeletal survey and further workup, he was found to have two osteolytic lesions within his right femur. Bone curettage of the right femur revealed metastatic adenocarcinoma from a prostate primary. This case exemplifies the importance of recognizing the potential for prostate cancer metastases to present as osteolytic lesions.

Validity of negative bone biopsy in suspicious bone lesions

Background

The presence of malignant cells in bone biopsies is considered gold standard to verify occurrence of cancer, whereas a negative bone biopsy can represent a false negative, with a risk of increasing patient morbidity and mortality and creating misleading conclusions in cancer research. However, a paucity of literature documents the validity of negative bone biopsy as an exclusion criterion for the presence of skeletal malignancies.

Purpose

To investigate the validity of a negative bone biopsy in bone lesions suspicious of malignancy.

Material and Method

A retrospective cohort of 215 consecutive targeted non-malignant skeletal biopsies from 207 patients (43% women, 57% men, median age 64, and range 94) representing suspicious focal bone lesions, collected from January 1, 2011, to July 31, 2013, was followed over a 2-year period to examine any additional biopsy, imaging, and clinical follow-up information to categorize the original biopsy as truly benign, malignant, or equivocal. Standard deviations and 95% confidence intervals were calculated.

Results

210 of 215 biopsies (98%; 95% CI 0.94-0.99) showed to be truly benign 2 years after initial biopsy. Two biopsies were false negatives (1%; 95% CI 0.001-0.03), and three were equivocal (lack of imaging description).

Conclusion

Our study documents negative bone biopsy as a valid criterion for the absence of bone metastasis. Since only 28% had a confirmed diagnosis of prior cancer and not all patients received adequately sensitive imaging, our results might not be applicable to all cancer patients with suspicious bone lesions.

Imaging Review of Pediatric Benign Osteocytic Tumors and Latest Updates on Management

Pediatric benign osteocytic tumors include osteoma, enostosis, osteoid osteoma, and osteoblastoma. In pediatric populations, benign bone tumors are more common than malignancies. Benign osteocytic tumors may have a unique clinical presentation that helps narrow the differential diagnosis. A systemic imaging approach should be utilized to reach the diagnosis and guide clinicians in management. Radiographs are the most prevalent and cost-effective imaging modality. Cross-sectional imaging can be utilized for tissue characterization and for evaluation of lesions involving complex anatomical areas such as the pelvis and spine. Computed Tomography (CT) is the modality of choice for diagnosis of osteoid osteoma. CT scan can also be utilized to guide radiofrequency ablation, which has been found to be highly effective in treating osteoid osteoma and osteoblastoma. Enostosis is a no-touch lesion. Osteoma is commonly located in the paranasal sinuses. Osteoma needs an excision if it causes complications due to a mass effect.

Bone lesions on baseline staging rectal MRI: prevalence and significance in patients with rectal adenocarcinoma

A T1 sequence on routine baseline staging rectal magnetic resonance imaging (MRI) is thought to help detect bone lesions. Our primary aim was to evaluate the incidence of bone lesions encountered on baseline staging rectal MRI, particularly the prevalence of bone metastases. This retrospective study included patients with rectal adenocarcinoma who underwent baseline rectal MRI at our institution between January 2010 and December 2017. The MRI report was reviewed for presence of bone lesions. When found, lesion type, presence of axial T1 non-fat-suppressed sequence, primary tumor T-stage, and presence of other organ metastases were recorded. In the absence of bone biopsy, the reference standard was follow-up imaging via computed tomography (CT), MRI, and/or positron emission tomography/CT (PET/CT) ≥ 1 year after the baseline MRI. The Wilcoxon rank-sum test and Fisher's exact test were used to compare clinicopathologic data of patients with malignant or benign bone lesions. A total of 1197 patients were included. 62/1197 patients (mean age 56.8 years (SD: 13.8), with 39 men) had bone lesions on baseline imaging, with 6 being bone metastases (0.5%, 95% CI 0.2%-1.1%). Of the 6 patients with bone metastases, 5/6 had other metastases (i.e., liver, lung) at baseline. Bone metastases on baseline rectal MRI performed for rectal adenocarcinoma are extremely rare. Furthermore, bone metastases without other organ (i.e., liver, lung) involvement is extremely rare.

Enostosis-related epilepsy

Unexpected bone lesions of the skull present a common dilemma, where radiological appearance and patient’s clinical background are crucial to avoid misdiagnosis.

Enostosis are benign sclerotic bone lesions; its aetiology is still unknown and its management is usually conservative, with good prognosis. Most of these lesions are asymptomatic and neurological involvement is rare. We present the first report of enostosis-related epilepsy.

Sclerotic bone lesions caused by non-infectious and non-neoplastic diseases: a review of the imaging and clinicopathologic findings

Bone sclerosis is a focal, multifocal, or diffuse increase in the density of the bone matrix on radiographs or computed tomography (CT) imaging. This radiological finding can be caused by a broad spectrum of diseases, such as congenital and developmental disorders, depositional disorders, and metabolic diseases. The differential diagnosis can be effectively narrowed by an astute radiologist in the light of the clinical picture and typical findings on imaging. Some of these lesions are rare and have been described as case reports and series in the literature. This article aims to collate the clinical-radiologic findings of non-infectious and non-neoplastic causes of bone sclerosis with relevant imaging illustrations.

An international expert opinion statement on the utility of PET/MR for imaging of skeletal metastases

BACKGROUND

MR is an important imaging modality for evaluating musculoskeletal malignancies owing to its high soft tissue contrast and its ability to acquire multiparametric information. PET provides quantitative molecular and physiologic information and is a critical tool in the diagnosis and staging of several malignancies. PET/MR, which can take advantage of its constituent modalities, is uniquely suited for evaluating skeletal metastases. We reviewed the current evidence of PET/MR in assessing for skeletal metastases and provided recommendations for its use.

METHODS

We searched for the peer reviewed literature related to the usage of PET/MR in the settings of osseous metastases. In addition, expert opinions, practices, and protocols of major research institutions performing research on PET/MR of skeletal metastases were considered.

RESULTS

Peer-reviewed published literature was included. Nuclear medicine and radiology experts, including those from 13 major PET/MR centers, shared the gained expertise on PET/MR use for evaluating skeletal metastases and contributed to a consensus expert opinion statement. [18F]-FDG and non [18F]-FDG PET/MR may provide key advantages over PET/CT in the evaluation for osseous metastases in several primary malignancies.

CONCLUSION

PET/MR should be considered for staging of malignancies where there is a high likelihood of osseous metastatic disease based on the characteristics of the primary malignancy, hight clinical suspicious and in case, where the presence of osseous metastases will have an impact on patient management. Appropriate choice of tumor-specific radiopharmaceuticals, as well as stringent adherence to PET and MR protocols, should be employed.

CT Attenuation Values Do Not Reliably Distinguish Benign Sclerotic Lesions From Osteoblastic Metastases in Patients Undergoing Bone Biopsy

BACKGROUND. CT attenuation thresholds that accurately distinguish enostoses from untreated osteoblastic metastases have been published. In the Mayo Clinic practices, these thresholds have been applied more broadly to distinguish benign sclerotic bone lesions other than enostoses from osteoblastic metastases. OBJECTIVE. The purpose of this article is to determine if CT attenuation thresholds allow the distinguishing of benign sclerotic bone lesions from osteoblastic metastases in patients undergoing bone biopsy. METHODS. A retrospective search was conducted to identify sclerotic lesions described on CT between October 7, 1998, and July 15, 2018, that underwent subsequent biopsy. Two musculoskeletal radiologists recorded lesions' maximum and mean attenuation. Using previously published attenuation thresholds, sensitivity and specificity for differentiating benign sclerotic lesions from osteoblastic metastases were calculated. ROC curve analysis was performed to determine if more appropriate attenuation thresholds exist. Intraclass correlation coefficients (ICCs) were computed. RESULTS. A total of 280 patients met inclusion criteria. Of those, 162 had malignant biopsy results and 118 had benign biopsy results. Of the 162 malignant lesions, 81 had received prior treatment. Maximum and mean attenuation were not significantly different between benign and malignant lesions for either reader (all p > .05). For reader 1, to distinguish benign from malignant lesions, a maximum attenuation threshold of more than 1060 HU resulted in sensitivity of 23.7%, specificity of 87.0%, and accuracy of 60.6%. A mean attenuation threshold of greater than 885 HU resulted in sensitivity of 19.5%, specificity of 90.7%, and accuracy 60.7%. ROC curve analysis showed AUCs for mean and maximum attenuation thresholds of 51.8% and 54.6%, respectively. Subgroup analyses of benign versus malignant and treated versus untreated lesions had similar results. Similar findings were obtained for reader 2. The two readers' ICC was 0.946 for maximum attenuation and 0.918 for mean attenuation. CONCLUSION. Published attenuation thresholds for distinguishing enostoses from osteoblastic metastases had slightly decreased specificity and markedly decreased sensitivity when applied to the differentiation of benign sclerotic lesions from osteoblastic metastases in our sample of biopsy-proven lesions. ROC analysis showed no high-performing attenuation threshold alternative. CLINICAL IMPACT. Published CT attenuation thresholds intended for distinguishing enostoses from osteoblastic metastases should not be used more broadly. More accurate alternative thresholds could not be derived.

Pearls and Pitfalls for Soft-Tissue and Bone Biopsies: A Cross-Institutional Review

Management of soft-tissue and bone neoplasms depends on a definitive histologic diagnosis. Percutaneous image-guided biopsy of bone and soft-tissue tumors is a cost-effective and accurate method to obtain a histopathologic diagnosis. Biopsy requests must be approached thoughtfully to avoid numerous potential pitfalls. Hasty biopsy planning places the patient at increased risk for misdiagnosis, delayed therapy, repeated invasive procedures, and substantial morbidity. Biopsy planning begins with a thorough review of the relevant clinical history and pertinent imaging. The biopsy route must be planned in concert with the referring orthopedic oncologist to preserve limb-sparing options. Carefully selecting the most appropriate imaging modality to guide the biopsy increases the chances of reaching a definitive diagnosis. It is also critical to identify and target with expertise the part of the lesion that is most likely to yield an accurate diagnosis. Percutaneous biopsy is a safe procedure, and familiarity with preprocedural laboratory testing parameters, anticoagulation guidelines, and commonly used sedation medications minimizes the risk of complications while ensuring patient comfort. Nondiagnostic biopsy results are not infrequent and may still have value in guiding patient treatment. Awareness of the imaging manifestations of tumor recurrence is also important. The aim of this article is to provide a comprehensive review of pertinent preprocedural, periprocedural, and postprocedural considerations for bone and soft-tissue musculoskeletal biopsies.The online slide presentation from the RSNA Annual Meeting is available for this article.^©RSNA, 2020.

Development of a clinical diagnostic tool to differentiate multiple myeloma from bone metastasis in patients with destructive bone lesions (MM-BM DDx)

BACKGROUND

Most patients with destructive bone lesions undergo a comprehensive diagnostic procedure to ensure that proper treatment decisions are pursued. For patients with multiple myeloma, this can lead to delays in diagnosis and treatment initiation. This study was conducted to develop a diagnostic rule that could serve as a tool for early identification of multiple myeloma and promote timely referral of patients to haematologists.

METHODS

The clinical prediction rule was developed using a retrospective case-series of patients with multiple myeloma (MM) and those with bone metastasis (BM) at Chiang Mai University Hospital from 2012 to 2015. Multivariable fractional polynomial logistic regression was used to derive a diagnostic model to differentiate between MM and BM patients (MM-BM DDx).

RESULTS

A total of 586 patients (136 MM patients and 450 BM patients) were included. Serum creatinine, serum globulin, and serum alkaline phosphatase were identified as significant indicators for the differentiation of MM and BM patients. The MM-BM DDx model showed excellent discriminative ability [AuROC of 0.90 (95%CI 0.86 to 0.93)] and good calibration.

CONCLUSIONS

This MM-BM DDx model could potentially allow for early myeloma diagnosis and improvement of overall prognosis. A prospective validation study is needed to confirm the accuracy of the MM-BM DDx model prior to its application in clinical practice.

Mimickers of Hill-Sachs Lesions [Formula: see text]

The purpose of this article is to describe the imaging appearance, etiology, clinical features, and treatment of rare presentations of common bone and joint diseases known to mimic Hill-Sachs lesions. Knowledge of uncommonly encountered manifestations of ankylosing spondylitis, rheumatoid arthritis, septic joint, hyperparathyroidism, hydroxyapatite deposition disease, malignant bone tumors, and benign bone cysts which mimic traumatic Hill-Sachs lesions is important for radiologists to guide the clinical care of patients who present with shoulder symptoms.

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.