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Musculoskeletal infections consist of different clinical conditions that are commonly encountered in daily clinical settings. As clinical findings and even laboratory tests cannot always be specific, imaging plays a crucial role in the diagnosis and treatment of these cases. Musculoskeletal infections most commonly occur secondary to direct inoculation into the skin involuntarily affected by trauma, microorganism, foreign bodies, or in diabetic ulcers; direct infections can also occur from voluntary causes due to surgery, vaccinations, or other iatrogenic procedures. Hematogenous spread of infection from a remote focus can also be a cause for musculoskeletal infections. Risk factors for soft tissue and bone infections include immunosuppression, old age, corticosteroid use, systemic illnesses, malnutrition, obesity, and burns. Most literature discusses musculoskeletal infections according to the diagnostic tools or forms of infection seen in different soft tissue anatomical planes or bones. This review article aims to evaluate musculoskeletal infections that occur due to direct inoculation to the musculoskeletal tissues, by focusing on the traumatic mechanism with emphasis on the radiological findings., (© 2024. The Author(s).)

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., (© 2024. The Author(s).)

Skin and soft tissues are among the most common sites of infections. Infections can involve the superficial epidermis to deep muscles and bones. Most infections spread through contiguous structures, although hematogenous spread can occur in the setting of an immunocompromised state and with atypical infections. While clinical diagnosis of infections is possible, it often lacks specificity, necessitating the use of imaging for confirmation. Cross-sectional imaging with US, CT, and MRI is frequently performed not just for diagnosis, but to delineate the extent of infection and to aid in management. Nonetheless, the imaging features have considerable overlap, and as such, it is essential to integrate imaging features with clinical features for managing soft tissue infections. Radiologists must be aware of the imaging features of different infections and their mimics, as well as the pros and cons of each imaging technique to properly use them for appropriate clinical situations. In this review, we summarize the most recent evidence-based features of key soft tissue infections., (© 2024. The Author(s), under exclusive licence to International Skeletal Society (ISS).)

Imaging plays an important role in the workup of musculoskeletal infection, in conjunction with clinical history and physical exam. There are multiple imaging modalities that can be of clinical utility in the setting of suspected infection, each with their own benefits and limitations. Radiography is a low-cost, accessible modality providing a broad osseous overview, but can be insensitive for early osteomyelitis. Ultrasound plays a more limited role in the workup of musculoskeletal infection, but can be useful in the pediatric population or for real-time guidance for joint and soft tissue aspirations. Computed tomography (CT) plays an important role in the timely and accurate diagnosis of critically ill patients in the emergency setting. Its superior soft tissue characterization allows for diagnosis of abscesses, and it can help confirm the clinical diagnosis of necrotizing fasciitis when soft tissue gas is present. Magnetic resonance imaging (MRI) is often the modality of choice in the diagnosis of infection, as its superior contrast resolution allows for clear delineation of the presence and extent of both soft tissue infection and osteomyelitis. Additionally, the use of intravenous contrast and advanced imaging sequences such as diffusion weighted imaging (DWI) further increases the diagnostic utility of MRI in the assessment for infection. Familiarity with the diagnostic utility of each imaging modality will allow the radiologist to appropriately guide imaging workup in the setting of clinically suspected infection., (© 2023. The Author(s), under exclusive licence to International Skeletal Society (ISS).)

Objective: To systematically review the accuracy of MRI and CT in diagnosing necrotizing soft tissue infection (NSTI)., Methods: MEDLINE and Embase were searched for original studies which reported the diagnostic performance of MRI or CT in detecting NSTI. Individual study quality was assessed using the QUADAS-2 tool. Sensitivity and specificity of MRI and CT were calculated and, if supported by data from at least two studies, pooled using a bivariate random-effects model., Results: Six MRI studies and 7 CT studies were included. There were no major concerns with regard to study quality and applicability. The included studies used multiple diagnostic criteria, with sensitivities and specificities of both MRI and CT ranging between 0 and 100%. T2 hyperintensity of deep fascia was the most commonly used diagnostic MRI criterion (5 studies), yielding a pooled sensitivity of 86.4% (95% confidence interval [CI] 76.1-92.7%) and a pooled specificity of 65.2% (95% CI 35.4-86.6%). Presence of gas was the most commonly used diagnostic CT criterion (3 studies), yielding a pooled sensitivity of 48.6% (95% CI 37.1-60.2%) and a pooled specificity of 93.2% (95% CI 73.3-98.5%)., Conclusion: T2 hyperintensity of deep fascia at MRI has high sensitivity and moderate specificity in diagnosing NSTI. Presence of gas at CT has low sensitivity but high specificity. A combination of diagnostic criteria may improve diagnostic performance, but this needs further investigation., (© 2021. ISS.)

The occurrence of nontuberculous mycobacterial (NTM) infection is rare, and the involvement of the musculoskeletal system is even less common. However, the incidence of soft tissue and skin NTM infection is increasing, particularly in patients who undergo injections and minor surgical procedures. Given the non-specific clinical manifestations of NTM infection, the lack of knowledge among physicians regarding this rare infection could lead to inaccurate and delayed diagnosis. Herein, we present a case of an isolated subcutaneous NTM infection caused by Mycobacterium abscessus in the upper back of an immunocompetent 68-year-old woman. The clinical presentation, magnetic resonance imaging findings (including diffusion-weighted imaging), and pathologic findings of subcutaneous NTM infection are described and compared with those of tuberculosis and tumor presentations to provide a more accurate clinical picture for a differential diagnosis.

Objective: After implantation of a metal-on-metal total hip arthroplasty (MoM THA), a large incidence of pseudotumor formation has been described recently. Several centers have invited patients for follow-up in order to screen for pseudotumor formation. The spectrum of abnormalities found by CT in MoM THA patients can be unfamiliar to radiologists and orthopedic surgeons. Previously, a CT five-point grading scale has been published. In this paper, a simplification into a three-point classification system gives insight in the morphological distinction of abnormalities of the postoperative hip capsule in MoM implants in relation to the decision for revision. The reliability of this simplified classification regarding intra- and interrater reliability and its association with revision rate is investigated and discussed., Materials and Methods: All patients who underwent MoM THA in our hospital were invited for screening. Various clinical measures and CT scan were obtained in a cross-sectional fashion. A decision on revision surgery was made shortly after screening. CT scans were read in 582 patients, of which 82 patients were treated bilaterally. CT scans were independently single read by two board-certified radiologists and classified into categories I-V. In a second meeting, consensus was obtained. Categories were subsequently rubricated in class A (categories I and II), B (category III), and C (categories IV and V). Intra- and inter-radiologist agreement on MoM pathology was assessed by means of the weighted Cohen's kappa. Categorical data were presented as n (%), and tested by means of Fisher's exact test. Continuous data were presented as median (min-max) and tested by means of Mann-Whitney U test (two group comparison) or Kruskal-Wallis test (three group comparison). Logistic regression analysis was performed in order to study independence of CT class for association with revision surgery. Univariate statistically significant variables were entered in a multiple model. All statistical analysis was performed two-tailed using alpha 5% as the significance level., Results: In total, 664 scores from 664 MoM hips obtained by two observers were available for analyses. Interobserver reliability for the non-simplified version (I-V) was κw = 0.71 (95% CI: 0.62-0.79), which indicates good agreement between the two musculoskeletal radiologists. Intra- and interobserver reliability for the simplified version (A-C) were respectively κw 0.78 (95% CI: 0.68-0.87), and κw = 0.71 (95% CI: 0.65-0.76). This indicates good agreement within and between the two observers. The simplified A-C version is significantly associated with revision exclusively due to MoM pathology, in both patients with unilateral MoM THA (p < 0.001) and patients with bilateral MoM THA (p < 0.044). The simplified A-C version is associated with several clinical measures. In patients with unilateral MoM THA, with or without contralateral THA, in situ time (p < 0.008), cobalt and chromium (p < 0.001) were statistically significant. In patients with bilateral MoM, cobalt (p < 0.001) and chromium (p < 0.027) were statistically significant. Revision is significantly associated with cup size (p < 0.001), anteversion of the cup (p < 0.004), serum ion levels of cobalt and chromium (p < 0.001) and the adapted classification system (p < 0.001). In univariate logistic regression analysis on revision, cup, anteversion of the cup, cobalt-chromium ion serum levels, and the simplified (A-C) CT category system were statistically significant. The simplified (A-C) CT category system was an independent associate of revision, in several multiple logistic regression models., Conclusions: The presented simplified CT grading system (A-C) in its first clinical validation on 48- and 64-multislice systems is reliable, showing good intra- and interrater reliability and is independently associated with revision surgery.

Objective: The present study demonstrates the osseous and soft tissue manifestations of alveolar echinococcosis (AE)., Patients: We report on eight patients with AE with bone or soft tissue involvement confirmed at biopsy or needle cytology., Results: All eight patients showed hepatic involvement. Four exhibited infiltration of the spine as a result of direct spread of the hepatic primary lesion; distant metastases were observed in only three of these patients. Calcifications, which are typical for hepatic manifestations of the disease, were observed in soft tissue in only two of eight cases (25%); we observed no instances of endovesicular daughter cysts., Conclusions: AE manifests itself in the vertebral column as a form of spondylitis and in soft tissue presents similar to an abscess. Since in most of these cases spread of the disease per continuitatem from the liver is present, the diagnosis is easily made from the characteristic hepatic findings.