Imaging of lower extremity infections: predisposing conditions, atypical infections, mimics, and differentiating features.

Imaging evaluation for lower extremity infections can be complicated, especially in the setting of underlying conditions and with atypical infections. Predisposing conditions are discussed, including diabetes mellitus, peripheral arterial disease, neuropathic arthropathy, and intravenous drug abuse, as well as differentiating features of infectious versus non-infectious disease. Atypical infections such as viral, mycobacterial, fungal, and parasitic infections and their imaging features are also reviewed. Potential mimics of lower extremity infection including chronic nonbacterial osteomyelitis, foreign body granuloma, gout, inflammatory arthropathies, lymphedema, and Morel-Lavallée lesions, and their differentiating features are also explored.

Lower extremity infections: Essential anatomy and multimodality imaging findings.

In modern practice, imaging plays an integral role in the diagnosis, evaluation of extent, and treatment planning for lower extremity infections. This review will illustrate the relevant compartment anatomy of the lower extremities and highlight the role of plain radiographs, CT, US, MRI, and nuclear medicine in the diagnostic workup. The imaging features of cellulitis, abscess and phlegmon, necrotizing soft tissue infection, pyomyositis, infectious tenosynovitis, septic arthritis, and osteomyelitis are reviewed. Differentiating features from noninfectious causes of swelling and edema are discussed.

The role of 18 F-FDG PET/CT in retroperitoneal sarcomas-A multicenter retrospective study.

BACKGROUND: The role of 18 F-fluorodeoxyglucose positron emission tomography/computed tomography (18 F-FDG PET/CT) in the evaluation of retroperitoneal sarcomas is poorly defined. We evaluated the correlation of maximum standardized uptake value (SUVmax) with pathologic tumor grade in the surgical specimen of primary retroperitoneal dedifferentiated liposarcoma (DDLPS) and leiomyosarcoma (LMS). METHODS: Patients with the above histological subtypes in three participating institutions with preoperative 18 F-FDG PET/CT scan and histopathological specimen available for review were included. The association between SUVmax and pathological grade was assessed. Correlation between SUVmax and relapse-free survival (RFS) and overall survival (OS) were also studied. RESULTS: Of the total 58 patients, final pathological subtype was DDLPS in 44 (75.9%) patients and LMS in 14 (24.1%) patients. The mean SUVmax was 8.7 with a median 7.1 (range, 2.2-33.9). The tumors were graded I, II, III in 6 (10.3%), 35 (60.3%), and 17 (29.3%) patients, respectively. There was an association of higher histological grade with higher SUVmax (rs = 0.40, p = .002). Increasing SUVmax was associated with worse RFS (p = .003) and OS (p = .003). CONCLUSION: There is a correlation between SUVmax and pathologic tumor grade; increasing SUVmax was associated with worse OS and RFS, providing a preoperative noninvasive surrogate marker of tumor grade and biological behavior.

Imaging Coccygeal Trauma and Coccydynia.

The coccygeal region has complex anatomy, much of which may contribute to or be the cause of coccyx region pain (coccydynia). This anatomy is well depicted at imaging, and management is often dictated by what structures are involved. Coccydynia is a common condition that is known to be difficult to evaluate and treat. However, imaging can aid in determining potential causes of pain to help guide management. Commonly, coccydynia (coccygodynia) occurs after trauma and appears with normal imaging features at static neutral radiography, but dynamic imaging with standing and seated lateral radiography may reveal pathologic coccygeal motion that is predictive of pain. In addition, several findings seen at cross-sectional imaging in patients with coccydynia can point to a source of pain that may be subtle and easily overlooked. Radiology can also offer a role in management of coccygeal region pain with image-guided pain management procedures such as ganglion impar block. In addition to mechanical coccyx pain, a host of other conditions involving the sacrococcygeal region may cause coccydynia, which are well depicted at imaging. These include neoplasm, infection, crystal deposition, and cystic formations such as pilonidal cyst. The authors review a variety of coccydynia causes, their respective imaging features, and common management strategies.©RSNA, 2020.

Adhesive capsulitis: review of imaging findings, pathophysiology, clinical presentation, and treatment options.

Adhesive capsulitis, commonly referred to as "frozen shoulder," is a debilitating condition characterized by progressive pain and limited range of motion about the glenohumeral joint. It is a condition that typically affects middle-aged women, with some evidence for an association with endocrinological, rheumatological, and autoimmune disease states. Management tends to be conservative, as most cases resolve spontaneously, although a subset of patients progress to permanent disability. Conventional arthrographic findings include decreased capsular distension and volume of the axillary recess when compared with the normal glenohumeral joint, in spite of the fact that fluoroscopic visualization alone is rarely carried out today in favor of magnetic resonance imaging (MRI). MRI and MR arthrography (MRA) have, in recent years, allowed for the visualization of several characteristic signs seen with this condition, including thickening of the coracohumeral ligament, axillary pouch and rotator interval joint capsule, in addition to the obliteration of the subcoracoid fat triangle. Additional findings include T2 signal hyperintensity and post-contrast enhancement of the joint capsule. Similar changes are observable on ultrasound. However, the use of ultrasound is most clearly established for image-guided injection therapy. More aggressive therapies, including arthroscopic release and open capsulotomy, may be indicated for refractory disease, with arthroscopic procedures favored because of their less invasive nature and relatively high success rate.

Coracoid process fractures: anatomy, injury patterns, multimodality imaging, and approach to management.

The coracoid process of the scapula is in close proximity to major neurovascular structures, including the brachial plexus and the axillary artery and vein. In addition, it serves as a major site of attachment for multiple tendons and ligaments about the shoulder. Isolated coracoid fractures are rare; however, they can be easily overlooked on routine shoulder radiographs. Importantly, when these fractures go undiagnosed, they are at high risk for nonunion. In this paper, we will review the relevant anatomy of the coracoid process, classification schemes for coracoid fractures, mechanisms of injury how these fractures typically present, multimodality imaging findings, and associated injuries. Finally, we will briefly discuss the clinical management of these fractures.

Intra-articular tongue-type fractures of the calcaneus: anatomy, injury patterns, and an approach to management.

Intra-articular tongue-type fractures may develop skin breakdown and often require urgent surgical reduction and fixation. Recognition of the imaging findings, accurate interpretation, and timely communication may prevent devastating clinical outcomes including soft tissue coverage procedures and amputation. This article reviews the anatomy of the calcaneus, as well as the clinical presentation and imaging findings of intra-articular tongue-type fractures. Imaging interpretation and clinical management of these fractures are discussed.

Fibular groove morphology and measurements on MRI: correlation with fibularis tendon abnormalities.

PURPOSE: Fibular (peroneal) groove morphology may influence fibularis tendon pathology, including tendinosis, tears, and luxation. The study goal was to evaluate the inter-reader agreement of morphologic characterization and measures of the fibular groove at two different levels on MRI and correlation with fibularis tendon pathology. MATERIALS AND METHODS: 47 ankle MRIs in patients without lateral ankle pain were reviewed by two musculoskeletal radiologists. Fibular groove morphology and various measurements were assessed at both the level of the tibial plafond and 1 cm proximal to the tip of the lateral malleolus. Fibularis tendon pathology and other variants were also recorded. Intraclass correlation (ICC) and kappa statistic (κ) were applied to assess inter-observer agreement. Receiver operating characteristic (ROC) and area under the curve (AUC) analysis were performed to determine correlation between fibular groove morphometry and fibularis (peroneus) brevis tendon tears. RESULTS: Between readers, there was fair-to-excellent agreement (ICC = 0.61-0.95) for performed fibular groove measurements and moderate-to-very good agreement for identification and description of fibular groove and fibularis tendon morphology and pathology and normal variants in this region (κ = 0.46-1), with the exception of fibular groove morphology at 1 cm proximal to the lateral malleolar tip (κ = 0.34). Individually, no measurement or description of pathology could discriminate between patients with or without fibularis brevis tendon tears except fibularis brevis tendinosis (AUC = 0.87 for reader 1). CONCLUSION: There is overall moderate-to-excellent inter-reader agreement for various measurements and descriptors of fibular groove and fibularis tendon morphometry and pathology, including novel measurements introduced in this study.

Detection of Traumatic Pediatric Elbow Joint Effusion Using a Deep Convolutional Neural Network.

OBJECTIVE: The purpose of this study is to determine whether a deep convolutional neural network (DCNN) trained on a dataset of limited size can accurately diagnose traumatic pediatric elbow effusion on lateral radiographs. MATERIALS AND METHODS: A total of 901 lateral elbow radiographs from 882 pediatric patients who presented to the emergency department with upper extremity trauma were divided into a training set (657 images), a validation set (115 images), and an independent test set (129 images). The training set was used to train DCNNs of varying depth, architecture, and parameter initialization, some trained from randomly initialized parameter weights and others trained using parameter weights derived from pretraining on an ImageNet dataset. Hyperparameters were optimized using the validation set, and the DCNN with the highest ROC AUC on the validation set was selected for further performance testing on the test set. RESULTS: The final trained DCNN model had an ROC AUC of 0.985 (95% CI, 0.966-1.000) on the validation set and 0.943 (95% CI, 0.884-1.000) on the test set. On the test set, sensitivity was 0.909 (95% CI, 0.788-1.000), specificity was 0.906 (95% CI, 0.844-0.958), and accuracy was 0.907 (95% CI, 0.843-0.951). CONCLUSION: Accurate diagnosis of traumatic pediatric elbow joint effusion can be achieved using a DCNN.

The anterior knee: normal variants, common pathologies, and diagnostic pitfalls on MRI.

The anterior aspect of the knee is host to an array of normal variants and potential pathology. These normal anatomic variants are often encountered and may mimic pathologies, leading to unnecessary work-up and treatments. On the other hand, there are several subtle abnormalities that may be easily overlooked or mistaken for variants or other injuries or diseases. Recognition of these diagnostic challenges is essential for radiologists to make an accurate diagnosis. This article reviews normal anatomical variants of ligaments, tendons, bones, and other important structures of the anterior knee, focusing on magnetic resonance imaging features. Commonly encountered injuries and abnormalities of the anterior knee and their diagnostic pitfalls are also discussed, highlighting findings on magnetic resonance imaging.

Scapulothoracic pathology: review of anatomy, pathophysiology, imaging findings, and an approach to management.

Symptomatic scapulothoracic disorders, including scapulothoracic crepitus and scapulothoracic bursitis are uncommon disorders involving the scapulothoracic articulation that have the potential to cause significant patient morbidity. Scapulothoracic crepitus is the presence of a grinding or popping sound with movement of the scapula that may or may not be symptomatic, while scapulothoracic bursitis refers to inflammation of bursa within the scapulothoracic articulation. Both entities may occur either concomitantly or independently. Nonetheless, the constellation of symptoms manifested by both entities has been referred to as the snapping scapula syndrome. Various causes of scapulothoracic crepitus include bursitis, variable scapular morphology, post-surgical or post-traumatic changes, osseous and soft tissue masses, scapular dyskinesis, and postural defects. Imaging is an important adjunct to the physical examination for accurate diagnosis and appropriate treatment management. Non-operative management such as physical therapy and local injection can be effective for symptoms secondary to scapular dyskinesis or benign, non-osseous lesions. Surgical treatment is utilized for osseous lesions, or if non-operative management for bursitis has failed. Open, arthroscopic, or combined methods have been performed with good clinical outcomes.

Isolated greater tuberosity fractures of the proximal humerus: anatomy, injury patterns, multimodality imaging, and approach to management.

The greater tuberosity is an important anatomic structure and its integrity is important for shoulder abduction and external rotation. Isolated fractures of the greater tuberosity are often subtle and may not be detected on initial radiographs. Clinically, these patients display symptoms which mimic a full thickness rotator cuff tear. It is important to differentiate these two entities, as their treatment is different (typically nonsurgical management for minimally displaced fractures versus rotator cuff repair for acute full thickness rotator cuff tears). When greater tuberosity fractures are significantly displaced and allowed to heal without anatomic reduction, they can lead to impingement. This article will review greater tuberosity anatomy and function, as well as the clinical presentation and multimodality imaging findings of greater tuberosity fractures. Imaging optimization, pitfalls, and clinical management of these fractures will also be discussed.

Differences in Functional Expression of Connexin43 and NaV1.5 by Pan- and Class-Selective Histone Deacetylase Inhibition in Heart.

Class-selective histone deacetylase (HDAC) inhibitors were designed to improve safety profiles and therapeutic effectiveness in the treatment of multiple cancers relative to pan-HDAC inhibitors. However, the underlying mechanisms for their therapeutic and cardiotoxic potentials remain poorly understood. Cardiac sodium currents (INa) and gap junction conductance (gj) were measured by whole cell patch clamp techniques on primary cultures of neonatal cardiomyocytes. Cardiac NaV1.5 sodium channel and connexin43 (Cx43) gap junction protein levels were assessed by Western blot analyses. Panobinostat produced concentration-dependent reductions in ventricular gj, peak INa density, and NaV1.5 protein expression levels. Membrane voltage (Vm)-dependent activation of INa was shifted by +3 to 6 mV with no effect on inactivation. Entinostat (1 µM) did not affect ventricular gj, peak INa density, or INa activation. However, the INa half-inactivation voltage (V½) was shifted by -3.5 mV. Ricolinostat had only minor effects on ventricular gj and INa properties, though INa activation was shifted by -4 mV. Cx43 and NaV1.5 protein expression levels were not altered by class-selective HDAC inhibitors. The lack of effects of class-selective HDAC inhibitors on ventricular gj and INa may help explain the improved cardiac safety profile of entinostat and ricolinostat.

Musculoskeletal Imaging Findings of Hematologic Malignancies.

Hematologic malignancies comprise a set of prevalent yet clinically diverse diseases that can affect every organ system. Because blood components originate in bone marrow, it is no surprise that bone marrow is a common location for both primary and metastatic hematologic neoplasms. Findings of hematologic malignancy can be seen with most imaging modalities including radiography, computed tomography (CT), technetium 99m (99mTc) methylene diphosphonate (MDP) bone scanning, fluorine 18 (18F) fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT, and magnetic resonance (MR) imaging. Because of the diversity of imaging appearances and clinical behavior of this spectrum of disease, diagnosis can be challenging, and profound understanding of the underlying pathophysiologic changes and current treatment modalities can be daunting. The appearance of normal bone marrow at MR imaging and FDG PET/CT is also varied due to dynamic compositional changes with normal aging and in response to hematologic demand or treatment, which can lead to false-positive interpretation of imaging studies. In this article, the authors review the normal maturation and imaging appearance of bone marrow. Focusing on lymphoma, leukemia, and multiple myeloma, they present the spectrum of imaging findings of hematologic malignancy affecting the musculoskeletal system and the current imaging tools available to the radiologist. They discuss the imaging findings of posttreatment bone marrow and review commonly used staging systems and consensus recommendations for appropriate imaging for staging, management, and assessment of clinical remission. ©RSNA, 2017.

Hypertrophic Osteoarthropathy: Clinical and Imaging Features.

Hypertrophic osteoarthropathy (HOA) is a medical condition characterized by abnormal proliferation of skin and periosteal tissues involving the extremities and characterized by three clinical features: digital clubbing (also termed Hippocratic fingers), periostosis of tubular bones, and synovial effusions. HOA can be a primary entity, known as pachydermoperiostosis, or can be secondary to extraskeletal conditions, with different prognoses and management implications for each. There is a high association between secondary HOA and malignancy, especially non-small cell lung cancer. In such cases, it can be considered a form of paraneoplastic syndrome. The most prevalent secondary causes of HOA are pulmonary in origin, which is why this condition was formerly referred to as hypertrophic pulmonary osteoarthropathy. HOA can also be associated with pleural, mediastinal, and cardiovascular causes, as well as extrathoracic conditions such as gastrointestinal tumors and infections, cirrhosis, and inflammatory bowel disease. Although the skeletal manifestations of HOA are most commonly detected with radiography, abnormalities can also be identified with other modalities such as computed tomography, magnetic resonance imaging, and bone scintigraphy. The authors summarize the pathogenesis, classification, causes, and symptoms and signs of HOA, including the genetics underlying the primary form (pachydermoperiostosis); describe key findings of HOA found at various imaging modalities, with examples of underlying causative conditions; and discuss features differentiating HOA from other causes of multifocal periostitis, such as thyroid acropachy, hypervitaminosis A, chronic venous insufficiency, voriconazole-induced periostitis, progressive diaphyseal dysplasia, and neoplastic causes such as lymphoma. ©RSNA, 2016.

US and MR Imaging of Pectoralis Major Injuries.

During the past 2 decades, the frequency of pectoralis major muscle injuries has increased in association with the increased popularity of bench press exercises. Injury of the pectoralis major can occur at the muscle origin, muscle belly, musculotendinous junction, intratendinous region, and/or humeral insertion-with or without bone avulsion. The extent of the tendon injury ranges from partial to complete tears. Treatment may be surgical or conservative, depending on the clinical scenario and anatomic characteristics of the injury. The radiologist has a critical role in the patient's treatment-first in detecting and then in characterizing the injury. In this article, the authors review the normal anatomy and anatomic variations of the pectoralis major muscle, classifications and typical patterns of pectoralis major injuries, and associated treatment considerations. The authors further provide an instructive guide for ultrasonographic (US) and magnetic resonance (MR) imaging evaluation of pectoralis major injuries, with emphasis on a systematic approach involving the use of anatomic landmarks. After reviewing this article, the reader should have an understanding of how to perform-and interpret the findings of-US and MR imaging of the pectoralis major. The reader should also understand how to classify pectoralis major injuries, with emphasis on the key findings used to differentiate injuries for which surgical management is required from those for which nonsurgical management is required. Familiarity with the normal but complex anatomy of the pectoralis major is crucial for performing imaging-based evaluation and understanding the injury findings. ©RSNA, 2017 Online supplemental material is available for this article.

Determination of the True Inclination Angle of the Main Bronchi Relative to the Median Sagittal Plane for Placement of a Left-Sided Double-Lumen Tube.

OBJECTIVES: This study aimed to determine the true inclination angle of the main bronchi relative to the median sagittal plane, using CT imaging to help increase accuracy of double-lumen tube (DLT) placement. DESIGN: In this retrospective study, 2 investigators independently measured normal chest CT scans from 50 male and 50 female patients. To determine the true AP axis, a mid-sagittal plane reference line (MSPRL) was drawn, intersecting the midsternum and the vertebral spinous process at the level of mid-carina. Lines were drawn through the center of each main bronchus to determine the inclination angle with regard to the MSPRL. SETTING: Research was conducted at a single institution, the Los Angeles County and University of Southern California Medical Center. PARTICIPANTS: Normal chest CT images from 50 women and 50 men. MAIN RESULTS: The mean true inclination angle between the main bronchi and trachea in the mid-sagittal plane was 108.4° on the left compared with 96.2° on the right (p<0.0001). INTERVENTIONS: No specific interventions were done because this was a retrospective study and CT scan analysis. CONCLUSION: The data suggested that the trachea does not merely branch in the horizontal plane but branches posteriorly as well, with a true mean anatomic angle between the left main bronchus and trachea of 108.4°. This finding concurred with the authors' suggestion that the DLT be rotated to 110° counterclockwise instead of the routine practice of 90°. The authors suggest clinicians rotate the DLT an additional 20° counterclockwise and direct the top of the DLT to the 11 o'clock position.

The iliotibial tract: imaging, anatomy, injuries, and other pathology.

The iliotibial tract, also known as Maissiat's band or the iliotibial band, and its associated muscles function to extend, abduct, and laterally rotate the hip, as well as aid in the stabilization of the knee. A select group of associated injuries and pathologies of the iliotibial tract are seen as sequela of repetitive stress and direct trauma. This article intends to educate the radiologist, orthopedist, and other clinicians about iliotibial tract anatomy and function and the clinical presentation, pathophysiology, and imaging findings of associated pathologies. Specifically, this article will review proximal iliotibial band syndrome, Morel-Lavallée lesions, external snapping hip syndrome, iliotibial band syndrome and bursitis, traumatic tears, iliotibial insertional tendinosis and peritendonitis, avulsion fractures at Gerdy's tubercle, and Segond fractures. The clinical management of these pathologies will also be discussed in brief.

Inferior glenohumeral ligament (IGHL) complex: anatomy, injuries, imaging features, and treatment options.

The inferior glenohumeral ligament (IGHL) complex is comprised of three components supporting the inferior aspect of the shoulder. It consists of an anterior band, a posterior band, and an interposed axillary pouch. Injuries to the IGHL complex have a unifying clinical history of traumatic shoulder injury, which are often sports or fall-related, with the biomechanical mechanism, positioning of the arm, and individual patient factors determining the specific component of the ligamentous complex that is injured, the location of the injury of those components, and the degree of bone involvement. Several acronyms are employed to characterize these features, specifying whether there is involvement of a portion of the anterior band, posterior band, or midsubstance, and if there is avulsion from the humeral attachment, glenoid attachment, or both. Imaging recommendations for the evaluation of the IGHL complex include magnetic resonance imaging (MRI), and injuries to this complex are best visualized with magnetic resonance arthrography. Additionally, a brief description of clinical management of inferior glenohumeral ligament injuries is included.

Changes in cardiac Nav1.5 expression, function, and acetylation by pan-histone deacetylase inhibitors.

Histone deacetylase (HDAC) inhibitors are small molecule anticancer therapeutics that exhibit limiting cardiotoxicities including QT interval prolongation and life-threatening cardiac arrhythmias. Because the molecular mechanisms for HDAC inhibitor-induced cardiotoxicity are poorly understood, we performed whole cell patch voltage-clamp experiments to measure cardiac sodium currents (INa) from wild-type neonatal mouse ventricular or human-induced pluripotent stem cell-derived cardiomyocytes treated with trichostatin A (TSA), vorinostat (VOR), or romidepsin (FK228). All three pan-HDAC inhibitors dose dependently decreased peak INa density and shifted the voltage activation curve 3- to 8-mV positive. Increases in late INa were not observed despite a moderate slowing of the inactivation rate at low activating potentials (<-40 mV). Scn5a mRNA levels were not significantly altered but NaV1.5 protein levels were significantly reduced. Immunoprecipitation with anti-NaV1.5 and Western blotting with anti-acetyl-lysine antibodies indicated that NaV1.5 acetylation is increased in vivo after HDAC inhibition. FK228 inhibited total cardiac HDAC activity with two apparent IC50s of 5 nM and 1.75 µM, consistent with previous findings with TSA and VOR. FK228 also decreased ventricular gap junction conductance (gj), again consistent with previous findings. We conclude that pan-HDAC inhibition reduces cardiac INa density and NaV1.5 protein levels without affecting late INa amplitude and, thus, probably does not contribute to the reported QT interval prolongation and arrhythmias associated with pan-HDAC inhibitor therapies. Conversely, reductions in gj may enhance the occurrence of triggered activity by limiting electrotonic inhibition and, combined with reduced INa, slow myocardial conduction and increase vulnerability to reentrant arrhythmias.