A Morel-Lavallée lesion represents a closed degloving injury associated with severe trauma which then presents as a hemolymphatic mass. MRI and ultrasound are useful modalities for evaluation.
Morel-Lavallée lesions typically occur when the skin and subcutaneous fatty tissue traumatically and abruptly separate from the underlying fascia.
The initial injury represents a shearing of subcutaneous tissues away from underlying fascia. The initial potential space created superficial to the fascia is filled by various types of fluid, ranging from serous fluid to frank blood.
The collection may then spontaneously resolve or become encapsulated and persistent.
The lesions classically occur over the greater trochanter of the femur 1. Although strictly speaking a Morel-Lavallée lesion only overlies the greater trochanter, similar biomechanical forces to the lumbar region, over the scapula, or over the knee can result in identical lesions 1,3.
The size of these lesions is variable, ranging from small thin slivers of fluid to thickly encapsulated lesions many centimeters in diameter. When chronic they are typically oval or fusiform in shape and adherent to the underlying fascia.
Typically these lesions are anechoic or hypoechoic; however, internal debris, including fat globules can give rise to echogenic foci or even fluid-fluid levels 1. A capsule of variable thickness may be seen.
MRI is able to clearly determine the relationship of the collection with the underlying fascia. The fluid is of variable signal intensity depending on makeup and may even show a fluid-fluid level 1.
Treatment and prognosis
Once these lesions become established and encapsulated then conservative management is rarely successful (e.g. compression bandages). Surgical drainage may be sufficient, although in some instances the capsule needs to be resected to prevent re-accumulation.
History and etymology
It was first described in 1848 by Victor-Auguste-François Morel-Lavallée, a French surgeon 4.
If in a classic location and with a characteristic appearance then little differential exists. In cases where the lesion is heterogeneous in morphology or fluid-fluid levels are present, the possibilities include 1-2: