Morel-Lavallee Lesions-Review of Pathophysiology, Clinical Findings, Imaging Findings and Management

Abstract

Morel-Lavallee lesion is a post-traumatic soft tissue degloving injury. This is commonly associated with sports injury caused by a shearing force resulting in separation of the hypodermis from the deeper fascia. Most common at the greater trochanter, these injuries also occur at flank, buttock, lumbar spine, scapula and the knee. Separation of the tissue planes result in a complex serosanguinous fluid collection with areas of fat within it. The imaging appearance is variable and non specific, potentially mimicking simple soft tissue haematoma, superficial bursitis or necrotic soft tissue neoplasms. If not treated in the acute or early sub acute settings, these collections are at risk for superinfection, overlying tissue necrosis and continued expansion. In this review article, we discuss the clinical presentation, pathophysiology, imaging features and differential diagnostic considerations of Morel-Lavallee lesions. Role of imaging in guiding prompt and appropriate treatment has also been discussed.

Keywords: Computed tomography; Degloving injury; Magnetic resonance imaging; Trauma; Ultrasound.

[Table/Fig-1]:

A 57-year-old man with medial thigh swelling status post fall. Ultrasound images of right medial thigh a) and b) demonstrates heterogeneous collection with internal septations (yellow arrow) and echogenic focus (blue arrow). Please note that there is no internal vascularity within the echogenic focus (blue arrow).

[Table/Fig-2]:

CT scan of the same patient as in [Table/Fig-1]. CT right thigh a) axial and b) coronal section demonstrate hypodense collection in medial thigh subcutaneous planes. Foci of fat attenuation within the collection (white arrowhead).

[Table/Fig-3]:

A 50-year-old man with back swelling status post-trauma. CT abdomen, a) axial and b) sagittal images demonstrate a large heterogeneous collection with fluid, fat (yellow arrowhead) and blood attenuation areas in the subcutaneous planes of right posterior lower back consistent with Morel Lavallee lesion (sub-acute haematoma). There is fat infiltration in adjacent soft tissue (white arrows).

[Table/Fig-4]:

A 17-year-old man, status post-trauma with lower back swelling. CT lumbar spine, a) sagittal and b) axial images demonstrate a large well circumscribed thick walled hypodense collection (black asterix) in the subcutaneous plane overlying the thoracolumbar fascia. There is mild wall enhancement (white arrowheads) and adjacent subcutaneous fat infiltration (yellow arrows).

[Table/Fig-5]:

Same patient as in [Table/Fig-4]. MRI lumbar spine sagittal a) T1, b) T2 and; c) and d) axial T1 & T2 images demonstrate a lenticular shaped collection between the thoracolumbar fascia and overlying subcutaneous fat and superficial fascia consistent with Morel-Lavallée. There is mild T1 hyperintensity relative to muscles with an internal area of T1 and T2 hypointensity (yellow arrowheads) representing retracted clot. There is hypointense capsule (blue arrow) and internal septations. Ultrasound images of the same region e) and f) demonstrate hypoechoic collection with septations (white arrowheads).

[Table/Fig-6]:

A 16-year-old man, post fall with marked tenderness at lumbosacral region and right leg numbness. MRI lumbar spine a) sagittal T1 weighted, b) T2 and c) STIR images demonstrate a small T1 hypointense (white asterix) and T2 and STIR hyperintense homogeneous collection (black asterix). The collection is between the thoracolumbar fascia (yellow arrows) and overlying subcutaneous fat and superficial fascia (blue arrows) consistent with Morel-Lavallée lesion.

[Table/Fig-7]:

A 26-year-old man with motor vehicle crash. CT images of the pelvis a) axial and b) sagittal images shows a well circumscribed lenticular shaped hypodense collection (black asterix) with enhancing rim. Please note the preserved fat plane (yellow curved arrow) between the paraspinal muscles and the collection signifying the collection is external to the fascia. Blue arrow signifies the inflamed fascia.

[Table/Fig-8]:

A 55-year-old woman, who had been in a motor vehicle accident with right hip pain. CT scan pelvis performed in 12 hours, a) axial and b) coronal images demonstrate heterogeneous irregular soft tissue attenuation posterolateral right thigh (white arrowhead), which can mimic a necrotic soft tissue tumour. Follow up CT pelvis after 12 days, c) axial and d) coronal images demonstrate a well defined organized fluid collection (yellow arrows) with a partially defined capsule superficial to tensor fascia lata/iliotibial band (black arrowheads). There is a mild peripheral enhancement.