What lies beneath: A case report of Morel-Lavallée lesion

Abstract

A Morel-Lavallée lesion is a rare internal degloving injury that patients present with to the Emergency Department (ED) typically following high impact trauma. The diagnosis is often missed due to its uncommon presentation and emphasis on other concomitant injuries that may have occurred as a result of polytrauma. Potential long-term complications from these closed soft-tissue injuries highlight the need for early recognition. We present one such case encountered in our ED and aim to familiarize readers with the presentation, diagnostic and treatment modalities, and challenges emergency physicians might face when encountering patients with such lesions.

Introduction

Closed Degloving injuries, or Morel-Lavallée lesions (MLLs), are uncommon but significant injuries associated with high impact trauma that are often missed in the Emergency Department (ED). ¹ MLLs are a result of shearing forces that abruptly separate the skin and subcutaneous tissue from the underlying fascia, leading to swelling and cavity formation due to disrupted vessels and lymphatics.^2–4 Patients with MLLs usually present acutely post-trauma; however, there are reports of diagnoses being captured months to years after the initial event.^3,5 Identification of these lesions is important as they can lead to complications such as pseudocapsule formation, infection, and necrosis causing significant morbidity to the patient.^3,6

Case report

A 24 year-old gentleman with a previous history of a right knee ACL repair presented to the ED following a bicycling accident. He described travelling downhill on a paved road at a relatively high speed, when he lost control and crashed into road guard-rail. His right knee was the first point of impact, and he landed on the right side of his body. He was able to stand immediately, however shortly after felt severe pain in his right lower limb and could not weight bear. He reported that his right thigh felt swollen. Physical examination revealed several upper and lower limb abrasions. The right thigh was significantly larger than the left by about 1.5 times, with several superficial abrasions, surrounding bruising, and noted to be tender to palpation with underlying fluctuance suggestive of a hematoma. His other findings were of right knee joint instability. Distal neuro-vascular examination of the right lower limb was unremarkable. Radiographs of the pelvis, both hips, right femur and right knee reported no fractures. Given the above, he was admitted under the Department of Orthopaedics. A CT scan of the right knee performed the next day reported subcutaneous haematomas lateral to the right hip joint and right upper thigh (Figure 1). Subsequently, an MRI was performed which reported a large subcutaneous collection adjacent to the deep peripheral fascia at the anterolateral aspect of the proximal thigh, probably representing a degloving injury (Figure 2). There were associated fractures of the right superior and inferior pubic rami, the right acetabulum, and a possible acute fracture at the medial aspect of the femoral head. Despite extensive discussion, the patient chose not to continue his inpatient stay and opted for outpatient therapy.

Figure 1.

Computed tomography of patient’s thigh with a reported hematoma noted lateral to the right hip joint/upper thigh, superficial to the right iliotibial band and the right vastus lateralis muscle (asterix). (a) axial view and (b) coronal view.

Figure 2.

Magnetic resonance imaging of patient’s right thigh which shows large Morel-Lavallée lesion (asterix) along the anterolateral aspect of the right proximal thigh just superficial to the deep circumferential fascia (red arrow). (a) T1-weighted axial view, (b) T2-weighted axial view, and (c) T1-weighted coronal view.

Discussion

Most MLLs have been related to high impact trauma such as road traffic accidents and industrial crush injuries, however a number of cases have also been associated with low impact injuries such as falls and sports injuries.^3,7 There have also been reports of post-operative MLLs that develop following liposuction and abdominoplasties, although there is debate whether these truly meet the definition of MLLs as no degloving injury has occurred.^6,8

Approximately up to 93% of MLLs have been reported from injuries to the pelvis or lower limbs, the remaining injuries occurring in the lumbro-sacral region (3.4%), abdominal wall (1.5%), head (0.5%), or unspecified areas (2%).^1,5,9 Within the lower body injuries, injuries to the greater trochanter and thigh have the highest reported incidence of development of MLLs.^2,9 The pathophysiology as to the predilection for these sites is likely due to the larger surface area of relatively mobile skin and subdermal tissues that overlie strong fascial tissue such as the fascia lata.^3,10 Following the shearing of these layers, disrupted vessels, lymphatics, and necrotic fat leak into the newly created dead space and form a supra-fascial collection, the size and flow rate of which is dependent on the number of disrupted vessels.^2–4 As the broken-down components from the collection are reabsorbed, the residual hemosiderin causes a local inflammatory reaction and formation of a fibrous pseudocapsule. This prevents further reabsorption of the collection and promotes slow re-accumulation of material into the space, which in turn can become a nidus of secondary bacterial infection. ⁶ In one case series, up to 46% of patients were found to have an infected collection which was not time dependent from diagnosis to intervention. ¹¹ In addition, MLLs may also cause loss of overlying skin in the affected region due to compromised blood flow and increased volume of fluid within the collection.^5,6

The clinical presentation of MLLs is variable. In our case the patient presented acutely with gross swelling of his thigh, fluctuance, ecchymosis and pain. Other signs during acute presentation include skin hypermobility and occasionally hypoesthesia as a result of damage to cutaneous nerve branches. ¹ Interestingly, there have been two case reports of MLLs that have presented to the ED as hypovolemic shock.^12,13 In chronic ML lesions, patient may present with gradually increasing swelling with or without pain and no obvious overlying dermal injury from the initial event.^2,3,7

Diagnostic imaging is key in the confirmation of suspected MLLs. In the ED, most EPs have access to point-of-care ultrasound (POCUS) which can help confirm the presence of a compressible focal heterogenous anechoic/hypoechoic collection deep to the subcutaneous layer and superficial to the muscle fascia. ⁴ However, ultrasound features of MLLs are non-specific, hence indistinguishable from other differential diagnoses such as, abscesses, fat necrosis, and simple hematomas.^4,6,10 In addition, the appearance of MLLs on ultrasound may change based on the time of presentation, as contents of the underlying collection become more homogenous secondary to liquefaction. ⁶

Computed Tomography (CT) imaging is the next readily available modality to assess MLLs for most EPs in tertiary care settings especially in acute trauma cases. ⁶ In particular, contrast enhanced images may demonstrate extravasation of blood into a closed pre-fascial space and may show fluid-fluid levels representing the separation of haemorrhagic and lymphatic fluid within the MLL.^3,4 MLLs can be distinguished from simple hematomas as they have lower density on the Hounsfield scale due to mixing of blood with low density lymphatic fluid within the lesion.^3,4 However in practice it is reported that majority of MLLs are often labelled as “haematomas” or “fluid collections” by radiologists in the setting of acute polytrauma.^3,6

Magnetic Resonance imaging (MRI) is the investigation of choice in diagnosing MLLs due to its excellent soft tissue contrast resolution, ability to differentiate between solid masses, and its ability to provide details on surrounding soft tissue characteristics.^6,14 MRI characteristics of MLLs differ based on the chronicity of the injury – acute lesions are generally hypointense on T1 and hyperintense T2-weighted images, subacute MLLs exhibit hyperintensity in both T1 and T2 images, while chronic lesions exhibit intermediate signal intensity on T1-weighted and heterogeneous hyperintensity in T2-weighted sequences.^4,6,14 The fibrous pseudocapsule formation associated with chronic MLLs is distinctly hypointense on both T1 and T2 weighted images (Figure 3).^4,5 While MR imaging may not be readily available in an EP’s arsenal of diagnostic tools, if a MLL is suspected the physician must make the appropriate referral and/or in-house consult to ensure MR imaging can be arranged for early accurate diagnoses and treatment.

Figure 3.

Axial T1 fat saturated weighted (a) and Coronal STIR (b) images of a well-defined fusiform Morel-Lavallée lesion seen in the right thigh. Image reproduced courtesy of Dr Yasser Asiri, from Radiopaedia.org, rID: 64792 (CC BY-NC-SA).

There have been attempts to classify MLLs based on MRI characteristics ¹⁴ or simply by the presence or absence of a pseudocapsule; ¹⁵ however no formal algorithm, scoring system, or treatment guideline have been globally adopted in the management of this uncommon lesion.^6,10

Treatment of MLLs differ based on chronicity, size, presence of infection, and overall patient condition. ⁶ Generally, for small acute lesions conservative management in the form of compression bandaging, anti-inflammatories, physiotherapy, and rest are recommended.^2,3,5,6 For lesions that fail conservative management and in larger lesions with volumes <50 mls, direct or image guided percutaneous aspiration of the collection with or without placement of drainage catheter has been shown to prevent further complications such as infection and future recurrence.^5,6 However, it was found that lesions with fluid volumes larger than 50 mls and chronic ones with well-formed pseudocapsules have higher rates of failure when managed with aspiration and compression alone, with recurrence rates of up to 83%.^2,3,5,6 The use of a sclerosing agent post-aspiration such as talc, doxycycline, or alcohol, mainly in isolated MLLs without underlying fractures, have been demonstrated to be very efficacious in treatment with 95.7% success rate reported in literature. ¹⁰ In the remainder of recurrent, chronic lesions (especially with pseudocapsule formation) and complex MLLs associated with polytrauma and underlying fractures, open surgical drainage and mass reduction is the preferred intervention, with the aim of reducing dead space and preventing re-accumulation of fluid.^2,6,10 Adjunct measures to open surgical techniques such as placement of quilting sutures, fibrin glue application, and placement and low suction drains have been reported to aid success of this intervention. ¹⁰ In the described case above, the patient's MLL was managed conservatively and he is recovering well.

Conclusion

The diagnosis of Morel-Lavallee lesions in the ED setting is particularly challenging for the clinician due to its rarity, varied presentation and deceptive appearance. Nonetheless, this case highlights the need for a high index of suspicion of MLLs in the ED, early diagnosis and definitive management with a consensus algorithm which will result in better outcomes.