A 55-year-old male patient presented with swelling in the lateral aspect of right thigh since 1 month following a history of fall on right thigh 5 months back. There was no history of pain at the site or fever at present.
USG examination showed an anechoic thick-walled lesion (Fig 1 ) with fluid debris level ( arrow in Fig 2 ) and a mobile hyperechoic structure suggestive of a fat globule ( arrow in Fig 3) in subcutaneous plane in the anterolateral aspect of right thigh. MR imaging showed a well-defined oval-shaped altered signal intensity lesion adherent to the deep fascia overlying the greater trochanter. The lesion (arrow) appeared hypointense in axial T1WI with hyperintense focus medially (Fig 4), hyperintense in coronal STIR image with the small medial focus being completely suppressed (green circle in Fig 5), and hyperintense in axial T2WI with fluid levels ( Fig 6). Axial T1WI post gadolinium contrast-enhanced image showed peripheral rim enhancement of the lesion with enhancement of adjacent soft tissue posteriorly (Fig 7). Coronal T2* GRE images showed blooming within the lesion suggestive of haemorrhage (Fig 8).
First described by the French physician, Victor-Auguste-François Morel-Lavallée in 1863, it is a type of closed traumatic soft-tissue degloving injury [1]. A consequence of high energy trauma and shear stress, it occurs due to the separation of hypodermis from the underlying fascia disrupting perforating vascular and lymphatic structures and creating a collection of blood, serosanguinous fluid, and necrotic fat with a tendency to expand and grow. [2] Gross pathological examination reveals a well-defined collection with an outer pseudo capsule formation in later stages filled with blood clots, fibrin, necrotic and normal fat globules with secondary microbial infection in up to 46% patients [3].
The most common site of involvement is the greater trochanter as a result of its large surface area, overlying mobile skin and large underlying dense capillary network with other common sites being thigh, pelvis and knee [4]. The lesion is notorious for its under detection in early stages due to late superficial skin discolouration following the traumatic episode [5]. Local examination findings include ecchymosis, soft tissue swelling, fluctuance, skin hypermobility, and associated pelvic and acetabular fractures.
Ultrasound examination reveals large well defined, oval or fusiform, compressible lesions with partial/complete septae, fluid levels, absent internal vascularity and a variable internal echogenicity within depending on the age of hematoma [2]. Though not pathognomic, rounded mobile hyperechoic foci within the lesion suggestive of sheared, disrupted fat globules is fairly specific to this condition [6]. Magnetic resonance imaging (MRI) is the investigation of choice and can reveal six types based on signal intensity (SI) characteristics and age of the lesion [2]. Type 1 lesions are most common and they are seromas in nature, type 3 is a chronic organizing hematoma, whereas type 2 lesion is a subacute hematoma as in our case which shows hyperintense SI on T1 and T2WI, internal inhomogeneity caused by entrapped fat globules, internal septations, fluid-fluid levels, thick peripheral capsule with close abutment of fascial planes being a common feature of all subtypes. The last three subtypes are rare, longstanding and atypical lesions demonstrating perifascial dissection and fatty layer lacerations [2].
This lesion can be managed conservatively, by percutaneous drainage, or open debridement and irrigation as was done in our case [7]. To the treating orthopedician, this is an important diagnosis as it is a significant cause of underlying peri operative infection, with early USG evaluation by the radiologist assuming critical importance [8].
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Morel-Lavallée Lesion
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1. On the ultrasound images, a relatively clear fluid-related hypoechoic area is visible between the subcutaneous fat layer and the deep fascia layer, appearing elliptical or fusiform. Partial septations and heterogeneous echoes can be seen internally, mostly indicating hemorrhagic or fatty components.
2. No apparent internal blood flow signal is observed, suggesting the lesion mainly consists of fluid or mixed fluid content rather than a highly vascularized solid lesion.
3. On MRI sequences (T1 and T2-weighted images), it appears as a fluid-signal lesion with relatively regular contours, accompanied by remnants of fatty components (visible as high-signal patches on T1 and T2). A capsule or stromal septations are visible. The lesion is closely adjacent to the surrounding fascial plane.
4. The lesion is limited to the space between the deep fascia and subcutaneous tissue on the lateral side of the right thigh, with no obvious bony destruction or signs of fracture, nor any definite changes in joint or bone marrow signal.
Based on the patient’s history of trauma, clinical presentation, and the characteristic imaging finding of “subcutaneous fascial fluid,” the most likely diagnosis is: Morel-Lavallée Lesion (closed soft tissue degloving injury).
The diagnosis is further supported by the typical imaging findings (MRI showing both T1 and T2 hyperintensity, with partial fatty content and septations) together with the history of trauma and the absence of any significant clinical manifestations of infection.
1. Treatment Strategy:
· For small cystic fluid collections without significant symptoms, conservative management can be attempted, including compression bandaging, appropriate rest, and local physical therapy.
· In cases of larger lesions or persistent hemorrhagic effusion, ultrasound or imaging-guided aspiration can be considered, with sclerosing agent injection or compression bandaging to reduce recurrence.
· If there is recurrent fluid accumulation, a risk of infection, or functional impairment, surgical intervention is required, including incision to remove the fluid and necrotic fat, irrigation of the wound, and placement of a drain if necessary.
2. Rehabilitation and Exercise Prescription (FITT-VP Principle):
(1) Initial Phase:
3. Lifestyle and Regular Follow-up:
· In addition to exercise, patients are encouraged to control body weight, maintain a balanced diet, and avoid smoking and alcohol to promote tissue repair and reduce postoperative complications.
· Regular outpatient visits should be scheduled, and imaging studies repeated as necessary to assess the cavity’s recovery and prevent recurrent fluid accumulation.
Disclaimer:
This report is based solely on the provided medical history and imaging data for reference purposes and does not replace an in-person consultation or the professional judgment of a physician. Patients should follow the advice of a specialist and attend follow-up appointments in a timely manner.
Morel-Lavallée Lesion
