Imaging of Musculoskeletal Soft-Tissue Infections in Clinical Practice: A Comprehensive Updated Review

Abstract

Musculoskeletal soft-tissue infections include a wide range of clinical conditions that are commonly encountered in both emergency departments and non-emergency clinical settings. Since clinical signs, symptoms, and even laboratory tests can be unremarkable or non-specific, imaging plays a key role in many cases. MRI is considered the most comprehensive and sensitive imaging tool available for the assessment of musculoskeletal infections. Ultrasound is a fundamental tool, especially for the evaluation of superficially located diseases and for US-guided interventional procedures, such as biopsy, needle-aspiration, and drainage. Conventional radiographs can be very helpful, especially for the detection of foreign bodies and in cases of infections with delayed diagnosis displaying bone involvement. This review article aims to provide a comprehensive overview of the radiological tools available and the imaging features of the most common musculoskeletal soft-tissue infections, including cellulitis, necrotizing and non-necrotizing fasciitis, foreign bodies, abscess, pyomyositis, infectious tenosynovitis, and bursitis.

Early diagnosis of necrotizing fasciitis: Imaging techniques and their combined application

“…US is convenient and quick to perform at the bedside, 65 making it especially friendly for patients with mobility problems who cannot undergo CT or MRI. 66,67 It is economical, non-invasive, 52 uses non-ionizing radiation, and does not require sedation, making it suitable for examining small paediatric patients. 55 F I G U R E 2 The area marked by the white arrow is the lateral aspect of the right lower extremity, and soft tissue gas along the fascial plane is visible on the radiograph.…”

“…63 Finally, the absence of T2 signal intensity changes in the deep fascia excludes NF. 52,56,58 Compared to CT and US, MRI's large field-of-view and multiplanar capability allow for better delineation of the extent of disease and, in some cases, can identify unexpected sources of infection, which may aid in planning surgical debridement or percutaneous drainage. 54 Furthermore, MRI has higher soft tissue contrast 67 and can be more sensitive in assessing the extent of infection and determining the presence of necrosis and edema.…”

“…If gas is seen to accumulate along fascial planes on radiographs (Figure 2), it is a more specific imaging modality suggestive of NF, with a specificity of approximately 94% 50 but a poor sensitivity of 48.9% 51 . Clinical experience has shown that the absence of gas does not exclude NF, 52 as only rare NF patients (24.8%–55.0% of patients) show the presence of gas at the site of the lesion, which is often possible only in the advanced stages of NF. Furthermore, most patients show only an increase in the thickness of the soft tissue 50,51,53 .…”

“…US is convenient and quick to perform at the bedside, 65 making it especially friendly for patients with mobility problems who cannot undergo CT or MRI 66,67 . It is economical, non‐invasive, 52 uses non‐ionizing radiation, and does not require sedation, making it suitable for examining small paediatric patients 55 . In addition, US effectively assesses possible foreign bodies, ruling out deep vein thrombosis and soft tissue tumours 56 and guiding puncture and aspiration in real‐time 57 .…”

“…In contrast, a superficial soft tissue infection or cellulitis is more likely if deep fascial involvement is thin (<3 mm) or signal intensity changes are present that are limited to superficial fascia or peripheral portions of the deep fascia or involve only small portions of contiguous intermuscular septa, and the infection affects fewer than three compartments 63 . Finally, the absence of T2 signal intensity changes in the deep fascia excludes NF 52,56,58 …”