Source: Ortho Bullets
No, this isn't a French language course and don't feel bad if you have never heard of this injury before. This was uncharted territory for me too - until I received a Level I trauma center follow-up on a pretty significant head-on MVC where someone crossed left of center several months ago. There isn't a whole lot we can do for this in the pre-hospital space, but an interesting case study none the less. Morel-Lavallée lesions (MLLs) were first described by Dr. Maurice Morel-Lavallée in the mid-19th century after observing a subcutaneous fluid collection in a patient who had fallen off a train.
In short, this lesion is a closed degloving injury seen in blunt trauma specifically when shearing or tangential/rotational forces are present. It is a rare occurrence as a result of high energy trauma and our radiology friends typically find this septate fluid collection pattern during MRI scans. The image above shows the exact mechanism as well as what is left behind in this new potential space. The skin and subcutaneous tissue get separated from the underlying fascia. In my patient's case, it was mostly blood which required two separate trips to the OR for exploratory laparotomies and fluid evacuation as well as multiple transfusions of packed red cells because exsanguination was an active life-threatening problem.
These injuries can happen essentially anywhere - however, the lower extremities and the abdomen/hips/pelvis with underlying fractures are very common locations. My encounter was centered on the patient's lower abdomen secondary to the dash and steering wheel. Below is an illustration demonstrating the areas of the body in which these lesions can occur.
Source; JAAOS
Presentations are delayed most of the time so repeated imaging is best, because missing a diagnosis like this comes with consequences like skin necrosis. This sequela occurs because the epidermal blood supply can be interrupted, infections in and around this newly formed capsule are quite common as well. You can imagine in the cases of multi-system trauma identification delays could happen easily because other more obvious injuries may distract from their presence. Lesions typically present within hours-to-days after trauma; however, up to one-third of cases present months-to-years later and may be difficult to associate with a specific inciting event. Clinical presentation can range from obvious external soft tissue damage with edema, ecchymosis, and epidermal or dermal injury, to no outward signs of underlying tissue trauma.
Management of this condition depends on several factors including size and location. Smaller asymptomatic lesions will be treated non operatively with compression dressings, analgesics, and observation (we can do this in the field setting). Larger lesions are treated with percutaneous aspiration with a drain or with surgical debridement and irrigation.
October 7, 2024
Author: Joshua Ishmael, MBA, MLS(ASCP)CM, NRP
Pass with PASS, LLC
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