Interesting case this week!!!
38 yr old male patient presents with marked bruising to the proximal lateral right thigh and hip, two weeks following a fall during a football match.
The mechanism of injury was a high energy fall onto the right leg at pace. Over the following 48 hrs, the patient reports the development of marked fluctuant swelling and ecchymosis to the proximal thigh.
The patient presented at the accident and emergency department (ED) two weeks following the initial injury following concerns of no resolution of the swelling and persisting bruising. A suspicion of a deep vein thrombosis (DVT) was proposed by the ED team and the patient was referred for a vascular ultrasound scan to rule out a DVT.
No evidence of a DVT on scan, however, in the region of the ecchymosis, there was a 9 cm x 4 cm ovoid, fluctuant, anechoic fluid collection arising between the subcutaneous fat and the deep fascia. The collection extends from the level of the greater trochanter into the proximal thigh (image 1).
Image 1: Panoramic longitudinal ultrasound image of the fluctuant collection (image courtesy of inner-vision musculoskeletal ultrasound scans)
In view of the mechanism of injury, location and considering that the interval between initial injury and scan was too short for complete liquefaction of a potential haematoma, the primary diagnosis is a Morel-Lavallee lesion.
An orthopaedic opinion was recommended.
Background
Morel-Lavallee lesions are described as degloving injuries, as the result of shearing forces which tear away the subcutaneous fat from the deep fascia (image 2).
Image 2: Mechanism of injury for Morel – Lavallee lesion (Case courtesy of Matt Skalski, Radiopaedia.org, rID: 22762)
Consequently, the perforating vessels and lymphatics are disrupted. This results in haematolymphatic fluid filling the new potential space which has been made by the separation of the subcutaneous fat/superficial fascia from the muscle/deep fascia (Image 2).
Image 3: Longitudinal magnified view of the Morel-Lavallee lesion demonstrating the separate layers and the intervening haematolymphatic fluid. (image courtesy of inner-vision musculoskeletal ultrasound scans)
A superb MSK radiologist at my NHS trust provided a very good simile for this lesion, comparing this lesion to an internal blister.
Morel-Lavallee lesions are most prevalent in the lateral hip/trochanteric region and proximal thigh. Other sites include the trunk, lumbar, prepatellar and scapular regions (image 4)
Image 4: Illustration highlighting the location of Morel-Lavallee lesions.
Morel-Lavallee lesions can develop a peripheral, enveloping capsule as a consequence of the associated inflammatory reaction. This is considered the attributing factor in the perpetuation of these lesions.
Ultrasound features
The chronology of the lesion is crucial to differentiate the lesion to its main differential, haematoma. Other differentials include fat necrosis, seroma, bursitis and abscess.
Typically, Morel-Lavallee lesions are characterised by the location of the collection and also:
- are anechoic or hypoechoic due to the mixture of blood and lymphatic fluid.
- may contain some internal debris such as fat globules or even fluid-fluid levels.
- Development of a fibrous pseudo-capsule over time
- Tapered ends/fusiform shape as the fluid is contained in the potential space between the fascia
1. Acute MLL (Less than 2 weeks old): hypoechoic, arising in the characteristic location and demonstrating typical tapered ends
2. Echogenic nodules within represent fat elements (yellow arrows)
Another distinguishing factor
Haematomas on the other hand tend to demonstrate a myriad of appearances depending on the chronicity and degree of reparative organisation:
- Acute
o More echogenic than Morel-Lavallee lesion
o Pseudo-solid appearance
o Surrounding soft tissue oedema
o Underlying muscle or soft tissue tear
o Ill defined margins
- Chronic
o More well defined margin/distinct capsule
o Organisation of the haematoma is demonstrated as solid coagulated blood with cystic areas representing areas of liquifation and internal fibrin septations
o Reduces in size over serial scanning (unless it continues to bleed or bleeding reoccurs) and becomes more anechoic with liquefaction of the haematoma
1. Ill-defined margins initially with a diffuse, homogenous, echogenic collection within
2. Organisation of the haematoma is demonstrated as solid coagulated blood with cystic areas representing areas of liquifation and internal fibrin septations
3. With full liquefaction of the haematoma, the contents reduce in size and become anechoic with progressing chronicity
Treatment
Conservative treatment
Small lesions without a capsule are typically managed with compression bandages, anti inflammatories, physiotherapy and bed rest. However, in the larger lesions and also where the presence of a fibrous pseudo capsule exists, percutaneous drainage and compression bandages are required to prevent the lesion refilling.
The presence of the fibrocapsule typically means that the lesion is at risk of reoccurrence with percutaneous drainage and open debridement being the only suitable option.
Chronic presentation
Surgical evacuation of the lesion to prevent infection in the chronic presentation is inevitable. If infection/fat necrosis has taken hold debridement and removal of necrotic tissue is also necessary.
Percutaneous Sclerodesis is an emerging less invasive, safer treatment option which encourages adhesion of the MLL cavity. Tissue tightness, contour deformities and longer recovery however are complications which cause some patients, particularly athletes, to opt for open surgery.
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