What is the diagnosis?

Morel-Lavallée Lesion (MLL)

• Pearl: This is an internal degloving injury resulting in a hemolymphatic collection between subcutaneous tissue and the underlying fascia that often develops after trauma or postoperatively [1,2]. Most commonly found in the proximal thigh overlying the greater trochanter, but may also be found on the trunk, low back, pelvis, knee and scapula [1-3].

Image 2. Image 1 with annotations by editor, Alex Tomesch, MD

What is the mechanism of injury?

High-energy blunt trauma (MVC, sports-related injury) that results in shearing of subcutaneous tissue off of the underlying fascia, leading to disruption of lymphatic and blood vessels [1,2].

What physical examination findings are expected?

Skin hypermobility, ecchymosis, tenderness to palpation, fluctuance, or soft tissue swelling [1,6].

• Pearl: One-third of MLL initially go undiagnosed because skin discoloration may take several days to fully develop [6].

Which imaging modalities can be used?

Plain films are used to assess for acute fractures or dislocations. Ultrasound and CT imaging are appropriate for initial emergency evaluation [5]. 

• Pearl: Ultrasound findings include a hypoechoic fluid collection that is deep to the hypodermis and superficial to the muscle fascia with no internal flow with Doppler [1]. The collection is usually compressible and may have internal debris including fat globules [1,5].

• Pearl: MRI is the imaging modality of choice as it provides the best characterization of the lesion due to its improved soft tissue contrast [1,5]. 

Image 3. Ultrasound images demonstrate a hypoechoic fluid collection deep to the subcutaneous fat and superficial to the fascia and musculature. Authors’ own image. Annotated by peer-reviewer. 

What are the complications?

Progressive expansion of the lesion, skin breakdown and necrosis, recurrence, and infection [1,3,5].

How are these injuries managed?

The decision regarding conservative versus operative management is based on chronicity, size of the lesion, clinical presentation, and imaging findings [1,3,5]. Management options include close observation without intervention, percutaneous drainage, sclerodesis, or operative intervention [1,6]. 

• Pearl: Compressive bandaging may be utilized in acute lesions located in extremities that are small and have no capsule formation [1,3]. Percutaneous drainage may be performed, but there is a high likelihood of recurrence [1,5]. Sclerodesis has a high rate of success with less recurrence [1-3]. Sclerodesis involves aspirating the fluid in the MLL, then injecting a sclerosing agent like doxycycline, and then subsequently aspirating the solution [1]. 

• Pearl: Orthopedic consultation for operative intervention with debridement is indicated if the overlying skin is necrotic [1]. Open drainage or mass resection is indicated for chronic MLL especially with fibrous capsule formation [1,3].