Morel-Lavallee Lesion

                                  Dr. KS Dhillon

Introduction

Maurice Morel-Lavallee, a French surgeon, in 1863 first described the Morel-Lavallee lesion. It is a closed degloving injury that occurs following trauma where the deep fascia gets separated from the skin and superficial fascia creating a potential space [1,2,3]. As a result of the trauma, lymphatics and blood vessels that lie in the vicinity are injured leading to the accumulation of lymph and blood in this potential space. A chronic inflammatory reaction sets in, which later leads to the formation of an encapsulated lesion lined by a fibrous capsule and filled with necrotic fatty tissue, debris, blood products, and fibrin [2].

The Morel-Lavallee lesion presents as a painful fluctuant swelling at the site of the trauma. The lesion is also termed as Morel-Lavallée seroma, Morel-Lavallée effusion, posttraumatic soft tissue cyst, or post-traumatic extravasation [4].The Morel-Lavallee lesion can be missed during the initial assessment and it can present later. This can lead to difficulty in management and long-term morbidity [3,5].

Etiology

The common causes of Morel-Lavallee lesions are blunt trauma, crush injuries, and high-velocity trauma [6]. About 25% of patients who develop Morel-Lavallee lesions have been involved in a road traffic accident [6,7]. This lesion is commonly associated with underlying fractures, especially of the acetabulum, proximal femur, and pelvis. 

The most commonly involved region is the greater trochanter and it accounts for more than sixty percent of the cases [5]. There are several predisposing factors that make the femoral site a common region for such lesions and these include the superficial position of the femoral bone, a large surface area, the strength of the underlying tensor fascia lata, and relative mobility of the subdermal soft tissue [8].  A body mass index of 25 kg/m or greater is a secondary predisposing factor.

Other less common sites for such lesions include the buttocks, scapular region, trunk region, and lumbosacral region. Direct-blow sports injuries to the knee can produce a Morel-Lavallee lesion [9,10]. In rare instances, these lesions have also been reported following abdominoplasty and liposuction [11].

Epidemiology

The true prevalence of this condition is not known. These lesions are often underdiagnosed and not often seen in practice. The prevalence after acetabular fractures is around 8.3%. It has a male predominance with an approximate 2:1 male to female ratio. This may be due to the male predominance in polytrauma patients [3,5].

Pathophysiology

Generation of shearing effect in between underlying deep fascial layers and superficial subcutaneous tissues due to trauma leads to a Morel-Lavallee lesion, and this results in the development of a cavity in the pre-fascial plane [12].  The Morel-Lavallee lesion develops predominantly in areas where the overlying skin is mobile, and the underlying fascia is tough, such as the quadriceps fascia, proximal to the knee, and the fascia lata in the proximal aspect of the lateral thigh [6]. The shearing force that causes separation of the layers leads to disruption of lymphatic vessels, locules of subdermal fat, and transaponeurotic capillaries [5]. 

The disruption of lymphatic vessels and capillaries leads to the leakage of blood and lymph into this cavity and results in the collection of a hemolymphatic fluid. The rate of formation will depend on the flow into the cavity and the number of vessels disrupted. With time, the blood components within the cavity gradually start to reabsorb leaving only the serosanguinous fluid in the cavity surrounded by a haemosiderin layer. The haemosiderin layer induces a cascade of inflammation in the surrounding peripheral tissues. This results in the formation of a fibrous capsule that prevents further reabsorption of fluid and leads to the formation of a chronic Morel-Lavallee lesion.[3][6]

 

 

Clinical presentation

The Morel-Lavallee lesion may present acutely or may appear days after the injury. The presentation depends on several factors. The extent and rate of hemolymphatic accumulation within the cavity, and the patient’s body habitus, will determine the clinical identification of the lesion. 

The soft tissue degloving injuries usually occur simultaneously with fractures of the proximal femur, acetabulum and pelvis. This association is related to the high-energy nature of injuries.

Letournel and Judet [13] reported that these lesions were found in 8.3% of their series of 245 acetabular fractures. Other authors [14] have suggested that the incidence of Morel-Lavallee lesion associated acetabular and pelvis fractures maybe even higher than what is reported because small lesions were likely overlooked.

In patients with Morel-Lavallee lesions, the injured area can demonstrate areas of ecchymosis, soft tissue swelling, fluctuance, or skin hypermobility. Superficial discoloration of the skin can be delayed for several days.

Hudson [15] estimated that as many as one-third of these lesions go undiagnosed at the time of acute trauma. With time the area can become painful and firm, indicating the formation of a capsule. Chronic lesions can mimic other soft-tissue lesions, including neoplasm. If left untreated, infection or necrosis of the soft-tissue envelope can occur.

The diagnosis of a Morel-Lavallee lesion is made by physical examination of the patient. Advanced imaging modalities, however, can be used to provide additional information. Especially in patients with pelvic or acetabular fracture a CT scan of the area can be obtained. The CT scan can identify small as well as large lesions. Six lesion patterns have been described depending on the lesion age and MRI findings [16].

Type 1.  Simple seroma. 

Type 2.  Subacute hematoma.

Type 3.  Mature organized hematoma. 

Type 4.  Closed fatty laceration complicated by perifascial dissection. 

Type 5.  Perifascial nodular lesion. 

Type 6.  Infected lesion with sinus tract, septations, and capsular formation.

 In general, each type is correlated with increasing complexity and chronicity of the lesion. The fluid-filled pocket is identifiable on T1-and T2-weighted MRI sequences. Many lesions occupy an extensive surface area; the average size is reported to be 30 x12 cm [17].

The MRI characteristics can help to define the age of the lesion. Acute lesions are hypointense on T1 weighted images and hyperintense on T2 weighted sequences. Subacute lesions are homogenously hyperintense on both T1 and T2 weighted sequences, with a peripheral capsule that is hypointense on both T1 and T2 weighted sequences [18]. The area may demonstrate heterogeneous composition, depending on the age of its varied contents. Other atypical MRI features include perifascial dissection, fatty layer lacerations, and development of multiple septations.

Treatment

Currently, there are no specific guidelines in the literature regarding the management of Morel-Lavallee lesions. There are multiple low evidence studies that show variable results of multiple treatment modalities. The treatment modalities include conservative management, percutaneous aspiration, sclerodesis, and open surgery.

Conservative treatment

Small acute Morel-Lavallee lesions (less than 50 cm x 3) with no capsule can be treated conservatively. This can be done by application of a compression bandage to soft tissue swelling. This, however, requires high patient compliance.

In chronic cases and in patients with large lesions, nonoperative management is not suitable, and surgical intervention is usually required [19].

 

 

Percutaneous Aspiration

Percutaneous aspiration can be carried out for small lesions ((less than 50 cm x 3). There are few studies that show effective results after percutaneous aspiration of the Morel-Lavallee lesion. The recurrence rate, however, is high, especially in lesions with a volume of more than 50 ml, for which multiple aspirations are usually required.

Sclerodesis

Sclerodesis has been successfully used in the treatment of Morel-Lavallee lesions, especially in patients in whom percutaneous aspiration had failed. The agents that are commonly used for sclerosing include doxycycline, vancomycin, tetracycline, erythromycin, bleomycin, talc and absolute ethanol. These agents produce cellular destruction within the periphery of the lesion, and this later leads to fibrosis. The overall efficacy of sclerodesis in managing Morel-Lavallée lesions is 95.7% [20]. 

Open Drainage and Mass Resection

Operative treatment is carried out for large lesions and in those where other forms of treatment have failed. There are 3 types of surgery that can be carried out.

1.Single-incision irrigation and debridement (I&D)

Single incision irrigation and debridement is carried out for large lesions (> 50 cm x 3) or persistent lesions that have failed non-operative management. The lesion should not be in the way of surgical approach for an underlying fracture. The outcome is a successful resolution of the lesion in up to 75% of cases with a single I&D and more than one I&D may be required for very large lesions.

2.Dual-incision I&D

A dual incision I&D is carried out in patients whose lesion overlies the surgical approach for fracture management and also in patients in whom the lesion is discovered intra-operatively during surgical approach. The lesions near a surgical approach have a higher rate of infection and may require several I&Ds prior to definitive management of the underlying fracture. 

 

 3.Open debridement with resection of the fibrous capsule

Open debridement with resection of the fibrous cyst is carried out in patients who have chronic lesions with pseudocyst formation. The outcome of treatment is mixed. Often multiple surgeries are required for eradication of the lesion. If the skin overlying the lesion is necrotic, then the dead tissue has to be debrided, and reconstruction of the soft tissue envelope carried out [21,22]. In patients where open drainage has failed, the last treatment modality is en masse resection of the lesion with an intact capsule [3].

Differential Diagnosis

The differential diagnosis of the Morel-Lavallee lesion includes, post-traumatic fat necrosis, post-operative seroma, coagulopathy-related hematoma, and post-traumatic myositis ossificans with diffuse subcutaneous edema. Postoperative seromas hold various pathological similarities with Morel-Lavallee lesions. Since Morel-Lavallee lesions can clinically, pathologically, and radiographically simulate multiple other conditions, a prior history of trauma can play a pivotal role in arriving at the diagnosis [2].

Prognosis

The prognosis of a Morel Lavallee lesion depends on several factors. Small acute lesions usually heal themselves without operative management and have an excellent prognosis. Larger lesions pose a risk factor for postoperative surgical site infection for the associated fractures. They may also dictate the timing of surgical intervention and the surgical approach chosen for the fractures. In chronic lesions the formation of the pseudocapsule prevents reabsorption of the contents, and that leads to undesirable sequelae leading to a poor prognosis.[23]

Complications

1.Recurrence

Recurrence is the most common complication. Recurrence occurs in upto 56% of patients who had non-operative treatment and in 15-20% of patients who had open debridements. The risk factors for recurrence are inadequate debridement and larger lesions. The treatment for recurrence include, repeat debridement and placement of drain, use of wound vacuum with secondary healing that usually requires delayed skin graft, and use of sclerotherapy with talc or other sclerosing compounds.

2.Pseudocyst formation

The risk factor for pseudocyst formation is a chronic untreated Morel-Lavallee lesion. The treatment is open debridement with resection of the fibrous capsule.

3.Skin necrosis

The risk factors for skin necrosis are delay in treatment, loss of epidermal blood supply due to inciting events or several repeat debridements of large lesions. The treatment is skin grafting.

3.Peri-operative infection

The presence of a Morel-Lavallee lesion has been cited as an independent risk factor for postoperative surgical site infection following acetabular and pelvic surgery.

Conclusion

Morel-Lavallee Lesion is a closed degloving injury that occurs following trauma where the deep fascia gets separated from the skin and superficial fascia creating a potential space. It presents as a painful fluctuant swelling at the site of the trauma. The lesion is also termed as Morel-Lavallée seroma, Morel-Lavallée effusion, post traumatic soft tissue cyst, or post-traumatic extravasation. It can be missed during the initial assessment and it can present later. 

Diagnosis requires a high index of suspicion with presence of an area of ecchymosis, swelling, fluctuance and skin hypermobility in the polytrauma patient with underlying fractures.

Treatment for most lesions is operative irrigation and debridement given the proximity to planned surgical incisions and increased risk of infection.

Complications such as recurrence, pseudocyst formation, skin necrosis, and infection are common.

The overall prognosis varies with chronicity of the lesion and size of the lesion.

 

 

References

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