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.

Keywords: interventional; magnetic resonance imaging; multidetector computed tomography; radiography; soft tissue infections; ultrasonography.

Figure 1

Conventional radiography (anterior–posterior oblique projection) of the right foot in a 44-year-old woman, who were presented to the emergency department with complaints about worsening pain and swelling in the plantar external region. The examinations confirmed local swelling of soft tissue and revealed the presence of thin foreign bodies, sea urchin quills (arrows and in enlargement), which was confirmed after surgical excision and anamnestic confirmation.

Figure 2

Ultrasound examination of a soft-tissue abscess of lateral aspect of the left harm in a patient who were recently operated for humeral fracture. The needle’s tip is placed inside the abscess (arrows) under ultrasound guidance (in-plane approach); during the fluid aspiration, the reduction of the abscess can be appreciated (dotted lines). H = humerus, A = abscess.

Figure 3

A 50-year-old man with left volar mid-palm pain after recent injury by glass. Grayscale US (a) demonstrates a 4 mm linear echogenic retained foreign body (arrows), with a surrounding hypoechoic halo (foreign body reaction/granuloma) in the subcutaneous tissues, and a color comet-tail artifact (arrowhead) on color Doppler (b).

Figure 4

A 30-year-old man with right hand pain after climbing a telephone pole. Axial (a) and sagittal (b) CT images demonstrate a 1.4 cm linear density compatible with a wood splinter (arrows), extending from the palmar subcutaneous tissues to the flexor retinaculum.

Figure 5

A 49-year-old man with left index finger pain and laceration after a wood-working injury at 6 weeks prior. Axial T1 (a), T2 FS (b), post-contrast T1 FS (c), and Cor PD FS (d) MRI demonstrate an 8 mm linear hypointense foreign body (arrows) with surrounding enhancement (arrowheads) and fluid signal intensity (curved arrow), compatible with a foreign body granuloma.

Figure 6

Deep-seated abscess of the right popliteal region in a 13.5-year-old boy presenting with a soft tissue painful swelling, fever, and inflammatory syndrome on blood analysis. The MRI comprises the following sequences: (A) coronal T1-weighted imaging (WI), (B) coronal T2-WI, (C) axial TRACE of diffusion MRI, (D) apparent diffusion coefficient (ADC) map, (E) axial T2, and (F) axial T1 with gadolinium chelate injection and fat suppression. On MRI, the abscess is presented as a fluid-like collection (white arrowhead) with high signal intensity (SI) on T2-WI, low SI on T1-WI, low SI on TRACE, and high ADC value and no contrast enhancement.

Figure 7

CE MRI in a 10-year-old boy presenting with limping and fever. Coronal ad axial T1 vibe FS post-contrast images (Panel A) demonstrate a bone infectious focus in the acetabulm (arrow) and a large abscess in the iliac and pettineus muscle with a peripheral rim enhancement (arrowhead). Coronal stir (Panel B) shows bone marrow edema in the acetabulum with enlargement and inflammation of surrounding muscular structures (oval dotted line).

Figure 8

MRI (Panel A and B, T2w axial; Panel C, T2w coronal sequence) of a 39-year-old male complaining of progressively increasing swelling of the right wrist and hand shows a marked tenosynovitis involving the common flexor digitorum sheaths (arrows), as well as the flexor pollicis longus (dotted arrows) and the flexor of the third digit (arrowhead). Both synovial thickening and fluid collection can be detected. The final diagnosis is tenosynovitis related to mycobacterium tuberculosis.