Summary A Morel-Lavallee Lesion (MLL) is a closed traumatic soft tissue degloving injury characterized by separation of the dermis from the underlying fascia due to a shearing force. Diagnosis requires high a index of suspicion with presence of an area of ecchymosis, swelling, fluctuance and skin hypermobility in the polytrauma patient with underlying fractures. Treatment is generally operative irrigation and debridement for most lesions given the proximity to planned surgical incisions and increased risk of infection. Epidemiology Incidence present in up to 8% of acetabulum fractures Anatomic location most often along proximal lateral thigh, in the peritrochanteric region to a lesser extent gluteal, lumbosacral, and abdominal areas due to hypermobility of skin in these regions Risk factors high-energy, shearing trauma Etiology Pathophysiology divided into 4 stages: shearing forces to soft-tissue envelope lead to separation of the dermis from the underlying fascia injured lymphatics and vasculature from the injured subdermal plexus produce these components are then replaced by serosanguinous fluid as the lesion enlarges finally, if left untreated during the acute stage, local inflammation leads to pseudocapsule formation and lesion maturation as the body attempts to sequester the space bacterial colonization of the fluid occurs in up to 46% of lesions Associated conditions orthopaedic conditions pelvic and acetabular fractures proximal femur fractures Anatomy Anatomy of soft tissues (order of layers from superifical to deep) epidermis dermis subcutaneous fat MLL develops deep to subctuaneous fat and superfical to deep fascia deep fascia muscle Presentation History there should be high clinical suspician for a MLL in a polytrauma patient with a high-energy mechanism Symptoms often minimally symptomatic or marginalized due to underlying distracting injuries or patient body habitus up to 33% of lesions are missed at the time of index evaluation chronic lesions may lead to cosmetic issues Physical exam inspection ecchymosis, swelling, fluctuance and skin hypermobility skin discoloration may not be apparent until several days later neurovascular key indicator is paresthesias of overlying skin Imaging Radiographs indications evaluate underlying proximal femur, acetabulum or pelvis fractures findings may show soft tissue swelling CT indications CT of the area of interest often obtained due to high-energy nature of the injury, underlying fracture, or abdominal/pelvic injury findings used to measure size of lesion to determine management soft tissue windows will show slice of fluid within fascial plane Ultrasound indications can be used to localize lesion for percutaneous treatment findings hypoechoic space superficial to fascial layer MRI indications generally not required for diagnosis but will best demonstrate extent of the lesion findings average size reported to be 30 x 12 cm fluid-filled space is often identifiable on T1- and T2-weighted MRI sequences. acute lesions are hypointense on T1-weighted images and hyperintense on T2-weighted sequences subacute lesions are homogenously hyperintense on T1- and T2-weighted sequences, with a peripheral capsule that is hypointense on both T1- and T2-weighted sequences Treatment Nonoperative compressive therapy indications small lesions (< than 50 cm3) outcomes resolutional of smaller lesions can be successful with compressive therapy but this requries high patient compliance percutaneous drainage with drain placement indications small lesions (< than 50 cm3) outcomes considered inferior to open debridement given inability to perform an adequate debridement of necrotic tissue Operative Single-incision irrigation and debridement (I&D) relative indications large lesions (> 50 cm3) or persistent MLL having failed non-operative management lesion is not in the way of surgical approach for fracture outcomes successful resolution of lesion in up to 75% of cases with single I&D more than I&D may be required for very large lesions Dual-incision I&D relative indications lesion overlies surgical approach for fracture management MLL discovered intra-operatively during surgical approach outcomes lesions near a surgical approach have a higher rate of infection and may require serial I&Ds prior to definitive managment of underlying fracture Open debridement with resection of the fibrous capsule relative indication chronic MLLs with pseudocyst formation outcomes mixed, often requires multiple surgeries for eradication Techniques Compressive therapy technique most common modalities are ace wraps, compression bandages, bike shorts (for proximal thigh lesions) Percutaneous drainage with drain placement technique use ultrasound to localize lesion then make 1-2 cm incision overlying leison insert a suction tip into the lesion to remove hemorrhagic fluid irrigate with normal saline Single incision I&D approach incision centered over MLL technique aggressive debridement of cavity performed with scrub brush, Cobb and/or other instruments placement of a drain exiting away from lesion (consider using 15 Fr or larger drain) recommend leaving drain until minimal output (< 20-30 cc/day) primary closure of lesion versus delayed closure controversial depends on size of lesion delayed closure would involve wound vaccum placement and repeat I&D and closure in 48-72 hours Dual-incision I&D approach incision over most proximal aspect of lesion counter incision over most distal aspect of lesion technique similar to single incision for rest of treatment EXCEPT primary closure of most proximal incision during first I&D delayed closure of distal incision with wound vacuum (VAC) return in 48-72 hours for repeat I&D through distal incision and closure Complications Recurrence incidence most common complication up to 56% in patients with non-operative managment and 15-20% in those with open debridements risk factors inadequate debridement, larger lesions treatment repeat I&D and placement of drain use of VAC and secondary healing (requires delayed skin graft) use of sclerotherapy with talc or other sclerosing compound Pseudocyst formation risk factors chronic, untreated MLL treatment open debridement with resection of the fibrous capsule Skin necrosis risk factors delay in treatment, loss of epidermal blood supply due to inciting event or several repeat I&Ds of large MLL lesions treatment skin grafting Peri-operative infection risk factors presence of a MLL has been cited as an independent risk factor for postoperative surgical site infection following pelvic and acetabular surgery Prognosis MLL cited as an independent significant risk factor for postoperative surgical site infection following pelvic and acetabular surgery Overall prognosis varies with lesion chronicity and size improved prognosis with smaller, acute lesions and discontiguous with surgical incisions