Review Topic
  • Overview
    • 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
      • often seen in the polytrauma patient with underlying pelvis or proximal femur fractures
      • operative irrigation and debridement recommended 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
    • 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 
  • 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 a fluid collection mixture of blood, lymph, and fatty debris  
      • 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
  • Prognosis
    • MLL cited as an independent significant risk factor for postoperative surgical site infection following pelvic and acetabular surgery
    • overall prognosis varies with lesion chronicty and size
      • improved prognosis with smaller, acute lesions and discontiguous with surgical incisions
  • 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
  • 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
  • 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
  • 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  
  • 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
  • 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

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