The Lesser Known Morel-Lavallée Lesion

Diagnosis and clinical presentation

Diagnosis requires a comprehensive history and physical examination alongside imaging modalities, typically ultrasound or MRI. The differential diagnosis for Morel-Lavalee lesions includes sarcoma, hemorrhagic prepatellar bursitis, simple soft tissue hematomas, superficial bursitis, or necrotic soft tissue neoplasms^(1-3).

History and physical examination

These injuries mainly occur due to blunt trauma after falls, motor vehicle accidents, and sport-related injuries^(1,2,4-6). Post-operative cases following liposuction have also been reported^(2,5). They often present soon after the inciting traumatic event, although some patients may have delayed presentation.

Clinical presentation
Lesions occur most commonly over the greater trochanter, buttock, thigh, and knee (see figure 3)^(2,5,7).

The most common symptoms include^(1,2,4,5,7):

• Soft, fluctuant area of contour deformity (swelling), which may have skin mobility.
• Localized tenderness due to the pressure effect of the large volume of serosanguinous fluid within a well-defined space (see figure 4).
• Bruising can take several days to develop.
• Decreased cutaneous sensation is often associated with the skin over the area of degloving because of shearing injury to the cutaneous nerves.
• Athletes may present with skin necrosis over the degloving area.
• Associated joint stiffness. However, in some cases, the affected joint has a complete and pain-free range of motion.
• Overlying soft tissue infection or skeletal fracture. The absence of prompt diagnosis and treatment may lead to secondary infection (e.g., cellulitis). The lesions can occur in isolation but are frequently associated with underlying fractures.

Investigations
Clinicians can request ultrasound, MRI, or CT scans to diagnose MLL^(1,2,4,5). On ultrasound, an elevation of the subcutaneous fat layer and superficial fascia layers from the deep fascia causes a fluid collection, which presents as an anechoic (dark) lesion on both longitudinal and transverse ultrasound imaging^(1,2).

Magnetic Resonance Imaging is the modality of choice for characterizing MLLs^(1,2,5). Six types of Morel-Lavallée lesions have been described based on the chronicity and composition of the collections and their MRI appearance (see table 1)^(1,2,4).

Table 1: Morel-Lavallée lesion classification^(1,2).

Treatment

Clinicians should consider several factors when determining the approach to managing an MLL. The lesion size, severity, and proximity to an intended surgical incision for coexisting injury will determine the treatment selection⁽⁴⁾. Management includes conservative treatment, minimally invasive treatment, and surgical intervention^(1,3,9).

Conservative treatment
Lesions with small fluid collections and no overlying pressure changes or underlying fractures can be managed conservatively by compression bandaging and physiotherapy^(1,9,10). Compression bandaging is vital as a form of primary treatment^(1,3,4,9). For hip and buttock lesions, tight cycling shorts may provide adequate compression⁽⁹⁾. Clinicians must educate patients on re-bandaging and recognizing the signs of infection to avoid complications⁽⁹⁾.

Physiotherapy is essential for the best functional outcomes after surgery or conservative management. Rehabilitation helps in reducing pain and regaining functional activities by improving joint ROM, strength, and cardiovascular fitness (see table 2)⁽¹⁰⁾.

Table 2: Post-surgical MLL debridement physiotherapy intervention⁽¹⁰⁾.

Minimally invasive treatments
Minimally invasive treatment options include aspiration or incision and evacuation, with or without injection of sclerosing agents^(1,5,9). Clinicians may use ultrasound-guided aspiration on acute lesions with fluid below 50ml^(4,5,9). The MLL is aspirated to dryness and then compressed with an elastic dressing. Further aspiration may be required if fluid reaccumulates.

When aspiration fails, sclerodesis prevents fluid collection and reduces the risk of recurrence post-aspiration^(5,9,11). Sclerodesis agents (oxycycline, erythromycin, bleomycin, vancomycin, absolute ethanol, tetracycline, and talc) cause cell destruction within the lesion’s periphery, which induces fibrosis⁽¹¹⁾.

Surgery: Open drainage and debridement
If initial percutaneous drainage fails, the skin overlying the lesion is necrotic, or the initial lesion is associated with an underlying open fracture, then open debridement and primary closure are indicated^(5,9,11). Lesions that fail this treatment or infected lesions require open drainage and secondary closure. If overlying skin is viable, open drainage can be achieved through either a single longitudinal incision or several small incisions proximally and distally⁽¹¹⁾. 

Conclusion

Morel-Lavallée lesions are closed degloving-type injuries commonly associated with sports injuries caused by a shearing force, resulting in the separation of the hypodermis from the deeper fascia. Separation of the tissue planes results in a complex fluid collection with areas of fat within it. They usually occur at the thigh, pelvis, knee, gluteal region, lumbosacral area, abdominal area, and lower leg. Diagnosis includes a physical examination, MRI, and or ultrasound imaging. Conservative or minimally invasive treatment is indicated for less severe cases. However, surgical debridement might be necessary for more complex and large MLLs. If not treated in the acute or early sub-acute settings, these collections are at risk for superinfection, overlying tissue necrosis, and continued expansion.

References

1. Emerg Radiol. 2014;21(1):35-43.
2. British Journal of Sports Medicine - Blog. Published 2022. blogs.bmj.com/bjsm/2022/05/08/morel-lavallee-lesions-diagnosis-and-practical-management-of-these-troublesome-injuries/
3. J Clin Diagn Res. Published online 2017.
4. J Am Acad Orthop Surg. 2016;24(10):667-672.
5. J Clin Diagn Res. Published online 2017.
6. BMJ Case Rep. 2021;14(4):e243082.
7. Case Rep Orthop. 2012;2012:1-5.
8. J Clin Orthop Trauma. 2014;5(3):161-166.
9. Journal of Sports Medicine - Blog. Published 2022. blogs.bmj.com/bjsm/2022/05/13/morel-lavallee-lesions-diagnosis-and-practical-management-of-these-troublesome-injuries-2/
10. Cureus. Published online September 24, 2022.
11. J Orthop. 2018;15(4):917-921.