A 24-year-old woman presented to the emergency department with leg pain. She was involved in a motor vehicle crash three weeks earlier, in which she jumped out of a moving truck and was subsequently struck by a vehicle at low speed. She sustained left proximal and distal fibular fractures, as well as fractures of several metatarsal bones.
She returned to the emergency department because of increased pain in her distal thigh and proximal lower leg and increasing drainage from some old wounds sustained during the crash. Her vital signs were notable for a heart rate of 120 bpm but otherwise normal.
Laboratory values were notable for a white blood cell count of 15,000 (76% neutrophils), a C-reactive protein of 202 mg/L, and an erythrocyte sedimentation rate of 65 mm/hr, all of which were unchanged from the time of discharge after the crash. Remaining laboratory values, including a lactate and basic metabolic panel, were within normal limits. An x-ray of the affected thigh is shown. What is the diagnosis?
Find the diagnosis and case discussion on the next page.
Diagnosis: Morel-Lavallée Lesion
The Morel-Lavallée lesion (MLL) is a post-traumatic closed degloving injury of the soft tissue. (J Am Acad Orthop Surg. 2016;24:667.) It is rare, but usually seen in high-energy traumas, most commonly in motor vehicle collisions. It was originally described in 1853 by Maurice Morel-Lavallée, a French physician, and typically occurs over the greater trochanter and lateral thigh. A retrospective review of MLLs found that 82 percent of cases were associated with trauma, and most of them occurred in conjunction with motor vehicle collisions and underlying fractures. (J Orthop. 2018;15:917; http://bit.ly/2OO8v1q.)
An MLL occurs when the skin and soft tissues are separated from the underlying fascial plane as a result of a high-energy shearing force. This leads to disruption of the bridging blood and lymphatic vessels and formation of a post-traumatic hematoma or seroma. These lesions often contain fibrin and liquefied fatty debris. The lesion can become encapsulated over time as the body attempts to isolate the fluid collection. These fluid collections can become colonized by bacteria and can sometimes be associated with necrosis of the overlying skin as the pressure further disrupts its vascular supply.
These lesions are rare and can be difficult to diagnose at the time of initial injury. Subsequently, they routinely present in the emergency department days to weeks after the initial injury. (J Emerg Med. 2015;49:e1.) The overlying skin may appear normal in the acute phase (immediately following injury) but develop discoloration, fluctuance, and tenderness over the following days to weeks. (Photo.)
Infection is a common complication and frequently the impetus for working up the condition. Multiple imaging modalities can be used to evaluate these lesions, including CT, ultrasound, and MRI. MRI has the best ability to characterize these lesions because of the heterogeneity of their appearance on other modalities. It should be considered the gold standard for diagnosis, and is the preferred method, especially for early diagnosis, when an MLL is suspected. (J Orthop. 2018;15:917; http://bit.ly/2OO8v1q.) That said, an MLL can frequently present similarly to a necrotizing soft tissue infection, as seen in this patient, with gas visible on the plain film. In such cases, postponing surgical consult or initiation of antibiotics to obtain further imaging is not advised.
As a result of MLLs' rarity, numerous management approaches have been suggested, but high-quality data to determine the relative efficacy of each are lacking. Some authors have reported success with treating small lesions more conservatively, with interventions ranging from compression bandages and local wound care to needle aspiration. Larger lesions with a greater amount of lymphatic and blood vessel disruption, however, are unlikely to heal with more conservative management, and appear to have lower rates of recurrence if managed with open operative debridement.
Operative debridement is considered standard of care and should be performed rapidly for patients with overlying skin necrosis or necrotic fat and subcutaneous tissue, like our patient. These patients are often managed postoperatively with negative-pressure therapy (e.g., wound VAC or a similar device) and ultimately receive skin grafting if tension-free closure is not feasible due to the extent of the lesion. (J Trauma Acute Care Surg. 2014;76:493.)
The most important differential diagnosis for an MLL is necrotizing soft tissue infection (NSTI). The history can suggest an MLL over an NSTI, but only biopsy or debridement can distinguish between the two; rapid surgical evaluation is imperative for all patients with concern for NSTI.
Our patient was given broad-spectrum antibiotics and taken for emergent operative debridement of the lateral thigh because of the subcutaneous gas seen on the plain radiograph. Necrotic skin and subcutaneous tissue of the distal thigh were debrided. The patient had a prolonged postoperative course and underwent numerous irrigation and debridement procedures over several weeks, ultimately requiring reconstructive skin grafting with plastic surgery and several weeks of negative-pressure wound therapy.
The patient regained ambulatory function with crutches, and was discharged home with family after significant physical and occupational therapy.
Dr. Lecceseis an emergency medicine resident at Denver Health Medical Center in Denver, CO. Dr. Barrettis an assistant professor of emergency medicine at the University of Colorado School of Medicine in Aurora and an attending physician at Denver Health Medical Center. She is also an associate medical director for the Denver Health Paramedic Division and the medical director for the paramedic school.