Morel-Lavallée Lesion: Review with Emphasis on MR Imaging

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Anatomic considerations

ML effusions may involve the subcutaneous tissues of the abdominal wall, the buttock, the lower lumbar spine, the scapular region, or the calf. ML lesions of the trochanteric region and proximal thigh are especially frequent and typically dissect perifascial planes adjacent to the fascia lata and iliotibial band [2].

In the thigh region, the superficial fascia represents the deepest portion of the cellular subcutaneous tissue. It occasionally separates into two or more layers, between which

Clinical considerations

ML effusions typically result from tangential trauma, most commonly in the setting of high-speed motor vehicle crashes. ML lesions of the trochanteric region and proximal thigh are particularly frequent in motorcycle accidents, usually in association with pelvic and acetabular fractures [2], [15], [16], [17], [18], [19]. They also may occur after plastic surgery, especially when liposuction and abdominoplasty are combined [4].

ML effusions represent abnormal dissection of the virtual space

Diagnostic imaging

The use of diagnostic imaging for detecting, characterizing, or staging ML lesions rarely has been addressed in the literature [6], [9], [10], [11], [12], [13]. Plain radiography may reveal a nonspecific, noncalcified soft tissue mass [6], [10]. The ultrasound appearance of ML lesion is that of a complex cystic mass, either anechoic or mildly hyperechoic [6], [11], [13]. On CT, ML lesions appear as well-defined, encapsulated fluid collections that occasionally show fluid-fluid levels [6], [10],

MR imaging features

ML lesions typically are found within the subcutaneous perifascial planes of the trochanteric region and anterolateral proximal thigh (Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8). They may be bilateral, may reach variable, occasionally large dimensions, and usually manifest some mass effect, generating contour abnormalities or compressive deformities on adjacent muscle bellies. ML lesions are usually well defined and oval or fusiform in shape and may have tapering margins

Differential diagnosis and treatment

The differential diagnosis of ML lesions includes other subcutaneous lesions of posttraumatic origin, such as fat necrosis and pseudolipoma, coagulopathy-related hematoma, and some soft tissue tumors.

Subcutaneous fat necrosis in children may present as a posttraumatic palpable lump [22]. The interval between trauma and lesion detection may be considerable [23]. The MR characteristics of fat necrosis vary depending on the age of injury. On MR imaging, subcutaneous fat necrosis may appear as

Summary

MR imaging is the diagnostic imaging modality of choice in the assessment of ML lesions in the hip region. Given their typical location, morphology, signal behavior, and enhancement pattern, ML lesions can be identified readily on MR examinations of the hip and proximal thigh. Correct preoperative MR diagnosis of ML lesions can be useful for treatment planning.

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