Morel-Lavellée lesions: MRI characteristics in the pediatric patient.

BACKGROUND: A closed degloving injury is often referred to as a Morel-Lavellée lesion regardless of location despite traditionally being associated with the hip in adults. It results from a shearing injury that separates the subcutaneous layers from the fascia with fluid filling a potential space.

OBJECTIVE: While the most common location and cause have been described in adults, there is limited literature in pediatric patients. We have seen pediatric Morel-Lavellée lesions commonly occurring at the knee after sports. We set out to describe the magnetic resonance imaging (MRI) characteristics.

MATERIALS AND METHODS: A retrospective analysis was performed. All patients with trauma to the pelvis and lower extremities with a subcutaneous fluid collection seen on MRI were evaluated. Age, gender, mechanism of injury, time interval to imaging, and treatment were recorded. The collections were evaluated for location, size, shape and signal characteristics including the presence of fat, blood and septations.

RESULTS: Twenty-one patients ages 7 to 17 years old had findings of degloving injury on MRI. The most common etiology was sports related (18/21, 85.7%). The anterior knee was most often affected (18/21, 85.7%). Lesions were ovoid and centered over the medial retinaculum (8/18, 44.4%) or lateral retinaculum (7/18, 38.9%). A capsule was weakly associated with later presentation (P=0.12).

CONCLUSION: Pediatric Morel-Lavellée lesions commonly occur in a location not classically described, the anterior knee, and often after sports injury. Commonly, the collections are ovoid and always located at the subcutaneous fat/fascial interface. Recognition of specific imaging characteristics in a common location after sports injury allows for early identification. While most patients recover with conservative management, some need additional intervention with aspiration or debridement.