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MRI of a Morel-Lavallée Lesion

Brooke Army Medical Center San Antonio, TX 78234
Brooke Army Medical Center San Antonio, TX 78234
Wake Forest University School of Medicine Winston-Salem, NC 27517-1088
Uniformed Services University of the Health Sciences Bethesda, MD 20814-4799
Brooke Army Medical Center San Antonio, TX 78234

Note.—The opinions and assertions contained herein are those of the authors and should not be construed as official or as representing the opinions of the Department of the Air Force, the Department of the Army, or the Department of Defense.

Editor's note.—The reader's attention is directed to the article titled "Long-Standing Morel-Lavallée Lesions of the Trochanteric Region and Proximal Thigh: MRI Features in Five Patients," which appears on page 1289 of this issue.

A Morel-Lavallée lesion is a closed degloving injury associated with severe trauma to the pelvis. It presents as a hemolymphatic mass located over the external aspect of the thigh. Since Morel-Lavallée first described the lesion in the 19th century, the term has been used to describe similar lesions in other anatomic sites such as the lumbar area and over the scapula [1, 2]. We describe the MRI appearance of a Morel-Lavallée lesion.

A 22-year-old man involved in a motor vehicle crash sustained fractures to the left inferior and superior pelvic rami that were considered stable and treated conservatively. A small mass in the anterolateral aspect of the left thigh was noted during a follow-up examination 38 days later and was followed clinically for 2 months. The lesion continued to increase in size and to cause the patient discomfort. Sonography and MRI of the lesion were performed (Figs. 5A, 5B, 5C) before surgery.

View larger version (114K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5A. —22-year-old man who developed Morel-Lavallée lesion after motor vehicle crash. Sonogram of left lateral thigh reveals large hyperechoic mass with distal acoustic enhancement, consistent with complex cystic mass.

View larger version (165K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5B. —22-year-old man who developed Morel-Lavallée lesion after motor vehicle crash. T1-weighted coronal MR image of left thigh shows well-circumscribed high-signal mass with pseudocapsule (arrow) and fat globule (arrowhead).

View larger version (121K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5C. —22-year-old man who developed Morel-Lavallée lesion after motor vehicle crash. T2-weighted axial MR image with fat saturation shows mass with uniformly high signal intensity and containing nodule (arrowhead) isointense relative to fat, consistent with entrapped fat globule in hematoma. Fluid–fluid level (arrow) is also seen.

Closed degloving injuries represent a traumatic severance of the skin and subcutaneous tissue from underlying fascia. This injury disrupts segmental perforating vessels and results in a hematoma composed of hemolymphatic fluid with a mixture of viable and necrotic fat [3]. The mechanism of the injury is a sudden violent shear stress to the anterolateral thigh. Depending on the violence of the injury, the resulting subcutaneous fluid collection may take several forms. An accumulation may develop slowly from shearing of the lymphatics or develop rapidly from trauma to arterial beds [1, 3]. Small lesions may resolve completely with a small incision, drainage, and application of a compression bandage. However, persistent lesions may contain a pseudocapsule that makes them refractory to conservative treatment [2].

Depending on the age of the hematoma, the lesion appears on sonography as anechoic relative to hyperechoic mass. It is located anterior to the muscle layer and posterior to the hypodermis, a hypoechoic layer showing as thin bands of echoes that represent connective tissue. The mass may contain fat globules that appear as hyperechoic nodules along its wall [2]. CT of a Morel-Lavallée lesion may show a fluid–fluid level resulting from sedimentation of cellular blood components, and a capsule may surround the mass. The capsule may help maintain the mass and explain why conservative therapy such as the application of a compression bandage is ineffective. Therefore, the finding of a capsule on imaging could be used to help select surgery over conservative therapy. MRI in this patient showed the exact size and composition of the lesion and the capsule surrounding it. MRI also showed a fluid–fluid level that was not visible on sonography.

A fluid–fluid level was initially thought to be specific for aneurysmal bone cyst. Subsequently, a fluid–fluid level has been reported in various bone neoplasms (fibrous dysplasia, simple bone cyst, malignant fibrous histiocytoma, metastasis, chondroblastoma, giant cell tumor, and osteosarcoma) and soft-tissue neoplasms (hemangioma and synovial sarcoma) [4]. A Morel-Lavallée lesion is another soft-tissue mass that may have a fluid–fluid level.

View larger version (91K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5D. —22-year-old man who developed Morel-Lavallée lesion after motor vehicle crash. Photograph of gross specimen shows entrapped fat globule.

References

1. Kottmeier SA, Wilson SC, Born CT, Hanks GA, Iannacone WM, Delong WG. Surgical management of soft tissue lesions associated with pelvic ring injury. Clin Orthop1996; 329:46 –53[Medline]
2. Parra JA, Fernandez MA, Encinas B, Rico M. Morel-Lavallée effusions in the thigh. Skeletal Radiol1997; 26:239 –241[Medline]
3. Hak DJ, Olson SA, Matta JM. Diagnosis and management of closed internal degloving injuries associated with pelvic and acetabular fractures: the Morel-Lavallee lesion. J Trauma1997; 42:1046 –1051[Medline]
4. Tsai JC, Dalinka MK, Fallon MD, Zlatkin MB, Kressel H. Fluid–fluid level: a nonspecific finding in tumors of bone and soft tissue. Radiology1990; 175:779 –782[Abstract/Free Full Text]

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This Article Figures Only Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Gilbert, B. C. Articles by Dejong, S. Search for Related Content PubMed PubMed Citation Articles by Gilbert, B. C. Articles by Dejong, S. Social Bookmarking                      What's this?