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.

A new comprehensive MRI classification and grading system for lumbosacral central and lateral stenosis: clinical application and comparison with previous systems.

PURPOSE: The purpose of our study was to provide a novel schematized and comprehensive classification of causes and severity grading system for lumbosacral stenosis. MATERIALS AND METHODS: The MRI system proposed consisted of a severity grading scale for central and lateral (recess and foramen) stenosis, together with a schematized indication of the main causes of the disease (disc, arthritis, epidural lipomatosis, and their combinations). The system was applied to a cohort of patients from a single Institution in the last 2-years. Two radiologists evaluated all the MRIs to determine intra- and inter-observer reliability according to Cohen Kappa (Kc, for non-ordered categorical variables) and weighted Kappa (Kw, for ordered variables). Two orthopaedic surgeons clinically evaluated all patients and provided a schematic grading system with a central and lateral stenosis clinical score (CS-CS and LS-CS). Associations between ordinals were tested with chi-square test and measured with the Goodman and Kruskal's gamma index (Gi, with 95% confidence interval [95% CI]). Lastly, the most used previous MRI systems were applied, and their performances were compared to the new system proposed. RESULTS: One hundred and twelve patients were included (55 females-mean age 63.3 ± 10.7 years). An almost perfect intra-observer agreement for the assessment of central stenosis, foramen stenosis, and lateral recess stenosis was found (Kw = 0.929, 0.928, and 0.924, respectively). The inter-observer agreement was almost perfect for central stenosis and foramen stenosis and substantial for lateral recess stenosis (Kw = 0.863, 0.834, and 0.633, respectively). Whatever the aetiologies involved in central and lateral stenosis, the intra-observer agreement was perfect (all Kc = 1), whereas the inter-observer agreements were almost perfect for arthritis (Kc = 0.838) and lipomatosis (Kc = 0.955) and substantial for disc (Kc = 0.691) regarding central stenosis. The inter-observer agreement for the causes of lateral stenosis was lower and variable, ranging from perfect (lipomatosis) to fair (disc, Kc = 0.224). The grading system revealed a strong association with CS-CS for both readers, with GI = 0.671 (95% CI 0.535-0.807) and 0.603 (95% CI = 0.457-0.749), respectively. The association with MRI grading and LS-CS was moderate for foraminal stenosis and for the concomitant presence of foraminal and lateral recess stenosis, with Gi = 0.337 (95% CI 0.121-0.554) and Gi = 0.299 (95% CI 0.098-0.500), respectively. A weak association was found between lateral recess grading alone and LS-CS with Gi = 0.102 (95% CI 0.193-0.397). The new grading systems showed higher Gi for associations with clinical symptoms, compared with previous ones, both for CS-CS and LS-CS. CONCLUSIONS: A standardized visual grading system for lumbar spinal stenosis that takes into account all of the major contributing factors-including disc, arthritis, and lipomatosis, for the central canal, lateral recess, and neural foramina could be a useful and practical tool for defining the stenosis, lowering inter-observer variability, and directing the various treatment options.

Whole-tumor 3D volumetric MRI-based radiomics approach for distinguishing between benign and malignant soft tissue tumors.

OBJECTIVES: Our purpose was to differentiate between malignant from benign soft tissue neoplasms using a combination of MRI-based radiomics metrics and machine learning. METHODS: Our retrospective study identified 128 histologically diagnosed benign (n = 36) and malignant (n = 92) soft tissue lesions. 3D ROIs were manually drawn on 1 sequence of interest and co-registered to other sequences obtained during the same study. One thousand seven hundred eight radiomics features were extracted from each ROI. Univariate analyses with supportive ROC analyses were conducted to evaluate the discriminative power of predictive models constructed using Real Adaptive Boosting (Adaboost) and Random Forest (RF) machine learning approaches. RESULTS: Univariate analyses demonstrated that 36.89% of individual radiomics varied significantly between benign and malignant lesions at the p ≤ 0.05 level. Adaboost and RF performed similarly well, with AUCs of 0.77 (95% CI 0.68-0.85) and 0.72 (95% CI 0.63-0.81), respectively, after 10-fold cross-validation. Restricting the machine learning models to only sequences extracted from T2FS and STIR sequences maintained comparable performance, with AUCs of 0.73 (95% CI 0.64-0.82) and 0.75 (95% CI 0.65-0.84), respectively. CONCLUSION: Machine learning decision classifiers constructed from MRI-based radiomics features show promising ability to preoperatively discriminate between benign and malignant soft tissue masses. Our approach maintains applicability even when the dataset is restricted to T2FS and STIR fluid-sensitive sequences, which may bolster practicality in clinical application scenarios by eliminating the need for complex co-registrations for multisequence analysis. KEY POINTS: • Predictive models constructed from MRI-based radiomics data and machine learning-augmented approaches yielded good discriminative power to correctly classify benign and malignant lesions on preoperative scans, with AUCs of 0.77 (95% CI 0.68-0.85) and 0.72 (95% CI 0.63-0.81) for Real Adaptive Boosting (Adaboost) and Random Forest (RF), respectively. • Restricting the models to only use metrics extracted from T2 fat-saturated (T2FS) and Short-Tau Inversion Recovery (STIR) sequences yielded similar performance, with AUCs of 0.73 (95% CI 0.64-0.82) and 0.75 (95% CI 0.65-0.84) for Adaboost and RF, respectively. • Radiomics-based machine learning decision classifiers constructed from multicentric data more closely mimic the real-world practice environment and warrant additional validation ahead of prospective implementation into clinical workflows.

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.

Linear Morphea With Inflammatory Myositis.

Morphea is an autoimmune disorder characterized by sclerosis and inflammation of the skin and soft tissues. Early diagnosis and treatment are essential to minimize morbidity such as joint contracture. In this report, we present the case of a 19-year-old man with linear morphea with inflammatory myositis who presented to our clinic 1 year after symptom onset with severe elbow flexion contracture. Through reviewing this rare disorder, it is hoped that early diagnosis will lead to better outcomes in the future.

A Precise and Reliable Method of Determining Lesion Size in Osteonecrosis of the Femoral Head Using Volumes.

BACKGROUND: To ascertain whether volumetric measurements to characterize lesion size in osteonecrosis of the femoral head using magnetic resonance imaging (MRI) and 3D software are more precise than other previously described methods. METHODS: Twenty-four patients were included in the study. Two musculoskeletal radiologists independently analyzed radiographs and MRIs using the methods described by Kerboul et al [9], Koo and Kim [10], and Cherian et al [11]. Volumetric measurements were calculated from the MRIs using 3D imaging software. Inter-rater reliability was calculated for all 4 methods using the interclass correlation coefficient (ICC). Levene's test was used to compare the variance across methods, serving as a measure of precision of each method. RESULTS: An ICC value of 0.81 was calculated for the volumetric measurements. The ICC values of the Kerboul et al, Koo and Kim, and Cherian et al methods were 0.94, 0.61, and 0.49, respectively. Levene's test for homogeneity of variance using absolute deviations showed the variance was not equal across methods (P < .01). The variance and the corresponding 95% confidence interval were calculated showing that the variance for the volumetric measurements was the smallest among the 4 methods examined, indicating that the volumetric measurements are more precise in characterizing lesion size as compared to the other methods. CONCLUSION: Volumetric measurements of lesion size using 3D MRI imaging software to assess osteonecrosis of the femoral head are more precise than previously described methods and have excellent interobserver reliability. A 3D MRI assessment of volume of osteonecrosis in the femoral head may be useful in clinical decision-making.

Shoulder measurements on MRI: Statistical analysis of patients without and with rotator cuff tears and predictive modeling.

This study aims to determine significant differences between various measurements of shoulder structures and relationships in patients with and without rotator cuff tears and identify a subset of these measurements that may merit further investigation. Shoulder MRIs of 120 patients with rotator cuff tears (RCT group) and 80 patients with normal examinations (No RCT group) were retrospectively identified. Numerous measurements of shoulder anatomy and relationships and pathology characterization were performed for each study. The mean and ranges of measurements for each group were identified, and P-values were calculated to assess differences between the two groups. Classification and Regression Tree (CART) identified prediction models for separating the two groups based on these shoulder MRI measurements. Statistically significant differences were observed for 9 of 18 of the shoulder measurements between the two groups (P < 0.05). Using long head of biceps tendon tear, tendinosis, and subacromial-subdeltoid bursal fluid, the prediction model from CART demonstrated 99.5% accuracy in separating the two groups. Subacromial distance, subacromial spur size, and acromioclavicular osteophyte could also separate the two groups with 97.5% accuracy. Other measures less commonly associated with impingement and rotator cuff tears could also be used to separate the two groups with up to 81.5% accuracy. This study introduces new measures and clarifies ranges for existing measurements on shoulder MRI. Abnormalities of some of these measurements may be associated with subacromial impingement, and combinations of these parameters may be useful for separating patients with or without rotator cuff tears. Clin. Anat. 33:173-186, 2020. © 2019 Wiley Periodicals, Inc.

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.

Clinical Nononcologic Applications of PET/CT and PET/MRI in Musculoskeletal, Orthopedic, and Rheumatologic Imaging.

OBJECTIVE: With improvements in PET/CT and PET/MRI over the last decade, as well as increased understanding of the pathophysiology of musculoskeletal diseases, there is an emerging potential for PET as a primary or complementary modality in the management of rheumatologic and orthopedic conditions. CONCLUSION: We discuss the role of PET/CT and PET/MRI in nononcologic musculoskeletal disorders, including inflammatory and infectious conditions and postoperative complications. There is great potential for an increased role for PET to serve as a primary or complementary modality in the management of orthopedic and rheumatologic disorders.

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.

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.

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.