Morel-Lavallee Lesion - Comprehensive Review

1. Definition and Historical Note

2. Etiology

Risk factors: Obesity significantly increases risk, as greater trochanteric shear forces are amplified by increased subcutaneous fat mass. The lesion is frequently missed in the acute setting because attention is directed toward distracting fractures.

• Campbell's Operative Orthopaedics 15th Ed 2026, Chapter 58
• StatPearls - Morel-Lavallee Lesion, NCBI Bookshelf

3. Pathophysiology

The Shearing Mechanism

• The overlying skin is highly mobile (thigh, hip, knee, lumbar back, shoulder)
• The underlying fascia is tough and adherent to bone (quadriceps fascia, fascia lata, iliotibial band)

1. Transaponeurotic perforating capillaries - causing hemorrhage
2. Lymphatic vessels - causing lymphorrhea
3. Subdermal fat lobules - causing fat necrosis

Stages of Evolution

• PathologyOutlines.com, Morel-Lavallee lesions, 2024
• Campbell's Operative Orthopaedics 15th Ed 2026

4. Common Anatomical Locations

Approximately 8% of patients who sustain a blow to the greater trochanter have a clinically significant MLL. - Campbell's Operative Orthopaedics 15th Ed 2026

5. Clinical Presentation

• Swelling - often disproportionate to the apparent surface injury
• Ecchymosis / skin bruising and discoloration
• Fluctuance - a "fluid wave" palpable in the subcutaneous tissue
• Skin hypermobility - skin slides freely over the deeper tissue
• Pain / tenderness (variable; may be surprisingly mild)
• In late presentations: skin necrosis, tense bullae, wound breakdown

6. Pathological Features (Histology)

• Reactive fibroadipose tissue with fibrosis
• Fat necrosis
• Hemorrhage (acute and hemosiderin-laden macrophages in chronic lesions)
• Pseudocyst formation lined by granulation tissue with reactive myofibroblasts
• The pseudocyst contains fibrin bands and hemorrhage
• No evidence of neoplasm or malignancy

7. Investigations

7.1 Plain Radiography

• Limited utility for the lesion itself
• Important for detecting associated fractures (pelvis, acetabulum, femur)
• May show soft-tissue swelling

7.2 Ultrasonography

• Rapid, bedside-available, no radiation
• Can show: fluid collection in the pre-fascial plane, internal echogenicity, fat globules
• Point-of-care ultrasound (POCUS) is valuable in acute trauma settings
• Useful for guiding aspiration
• Less specific than MRI for lesion characterization

7.3 CT Scan

• Often the first imaging obtained in polytrauma patients
• Shows a hypodense, lens-shaped or elliptical fluid collection in the subcutaneous plane
• Can detect associated fractures simultaneously
• Should be "scrutinized for a fluid collection in the subcutaneous tissues" in any pelvic fracture patient

7.4 MRI - Investigation of Choice

8. Differential Diagnosis

9. Treatment

9.1 Conservative Management

• Observation with compression bandaging
• Suitable for very small, acute lesions (< 50 mL)
• Risk of recurrence is high; infection rate ~19% even with observation
• Not recommended for large or chronic lesions

9.2 Percutaneous Aspiration

• Needle/catheter aspiration of the fluid collection
• Quick and minimally invasive
• High recurrence rate
• Infection rate of 56% with aspiration alone vs. 19% with observation vs. 15% with excision
• Appropriate only for very small, acute collections

9.3 Percutaneous Drainage (Tseng-Tornetta Technique)

1. Position patient to expose the lesion
2. Make a 2-cm incision over the distal aspect of the lesion
3. Make a second 2-cm incision at the superior/posterior extent
4. Determine extent with a suction tip
5. Additional incisions as needed for large lesions
6. Send fluid for culture and sensitivity
7. Drain the hematoma with suction
8. Debride loose fat with a plastic brush
9. Irrigate with pulsed lavage until fluid is clear
10. Place a medium closed suction drain throughout the cavity
11. Close incisions tightly
12. Connect drain to wall suction until output < 30 mL/24 hours (may take up to 8 days)
13. Continue IV cephalosporin or specific antibiotics for 24 hours post drain removal

Tseng and Tornetta reported good results in 19 patients using this percutaneous technique performed within 3 days of admission.

9.4 Sclerotherapy

• Aspiration followed by injection of a sclerosing agent into the cavity
• Common agents: doxycycline, ethanol, talc
• Effective for lesions up to 400 mL
• Prevents recurrence by obliterating the cavity
• Risk: contour deformities at the injection site
• Increasingly used as a minimally invasive first-line option

9.5 Fibrin Sealant Injection

• After aspiration, fibrin glue is injected to seal the space
• Limited evidence; used in selected cases

9.6 Open Surgical Debridement and Excision

• Preferred for large (> 50 mL), chronic, recurrent, or infected lesions
• Includes complete excision of the fibrous pseudocapsule
• Higher morbidity but lowest recurrence rate
• Negative pressure wound therapy (NPWT) may be used post-operatively
• Infection rate reported as high as 12% with repeated postoperative debridement when operating through an infected MLL

9.7 Endoscopic Debridement

• Emerging technique combining endoscopic debridement with percutaneous cutaneo-fascial suture
• Allows thorough cavity debridement via small portals
• Reported 3-year follow-up data shows favorable outcomes with rapid return to activity (Injury, 2024)

Treatment Algorithm Summary:

Acute / Small (< 50 mL)         → Observation + compression
Acute / Small, persistent        → Percutaneous aspiration ± sclerotherapy
Acute / Large (> 50 mL)         → Percutaneous drainage (Tseng-Tornetta) or sclerotherapy
Subacute / Chronic, non-infected → Open drainage + debridement + excision of capsule
                                   OR endoscopic debridement
Infected                         → Urgent open debridement + IV antibiotics
                                   + delayed fracture fixation (24h after drain removed,
                                   output < 30 mL/day)

10. Complications

11. Special Considerations in Fracture Surgery

1. Perform percutaneous decompression and debridement first
2. Wait at least 24 hours after drain removal with output < 30 mL/day
3. Consider using an anterior approach to avoid the affected lateral hip area
4. Do not proceed with posterior ORIF through an active/infected MLL

12. Key Takeaways

• MLL is a closed degloving injury from shearing trauma - skin/fat separated from deep fascia
• Most common at the greater trochanter and proximal lateral thigh (> 60% of cases)
• Frequently missed or delayed in diagnosis due to distracting fractures
• MRI is the investigation of choice - elliptical subcutaneous collection with hypointense rim in chronic lesions
• Collections > 50 mL are at high risk of infection and should be managed surgically
• Definitive treatment for chronic lesions is open debridement with complete excision of the fibrous capsule
• Operating through an undebrided MLL significantly increases surgical site infection risk

• Campbell's Operative Orthopaedics 15th Ed 2026, Chapter 58 (Soft Tissue Injury) and Chapter on Acetabular Fractures
• Bailey and Love's Short Practice of Surgery 28th Ed, Chapter 3 (Degloving)
• Grainger & Allison's Diagnostic Radiology, Chapter 42 (Traumatic Lesions)
• Rockwood and Green's Fractures in Adults 10th Ed 2025, Chapter 16 (Degloving Injuries)
• Sarani N et al. "Morel-Lavallée lesion: What you need to know." J Trauma Acute Care Surg. 2026. [PMID: 40905976] (Systematic Review, Level I evidence)
• PathologyOutlines.com, Morel-Lavallée lesions, 2024