Case Report: Chronic Morel-Lavallée lesion: dynamic MRI progression, histopathological findings and surgical treatment.

BACKGROUND

The Morel-Lavallée lesion (MLL) is a closed soft tissue avulsion injury resulting from shear force trauma. Chronic Morel-Lavallée lesions present significant management challenges due to the formation of fibrous caps, persistent fluid accumulation, and a tendency for recurrence. Nevertheless, the pathogenesis and imaging characteristics of these lesions remain poorly understood.

METHODS

This study presents a case of a chronic Morel-Lavallée lesion located in the right hip, with a disease progression lasting over 10 years. The MRI characteristics of the lesion were compared across different stages. The patient underwent open resection of the lesion, along with excision of excess skin and subcutaneous tissue, followed by negative-pressure drainage surgery. The efficacy of the treatment was evaluated through a 1-year postoperative follow-up.

RESULTS

MRI examinations at different time points revealed a progression of the lesion from a chronic organized hematoma (Mellado-Bencardino classification Type III) to a coexistence of a chronic organized hematoma (Type III) and subacute hematoma-like lesions (Type II), indicating dynamic progression rather than static stability of the chronic Morel-Lavallée lesion. Characteristic MRI findings included hematoma organization, fibrous capsule formation, round fat globules or fat septa, and layered fluid distribution within the cyst. Open surgery achieved complete resection of the lesion along with excess skin and subcutaneous tissue, followed by negative-pressure drainage, resulting in excellent wound healing; no recurrence was observed during the one-year follow-up, and hip joint function remained normal.

CONCLUSION

The chronic progression of Morel-Lavallée lesions is a dynamic process characterized by MRI findings such as fat globules or fat septa, fluid level stratification, hematoma organization, and capsule formation, all of which aid in definitive diagnosis. For large, recurrent chronic Morel-Lavallée lesions, open surgical resection of the lesion, along with the excision of excess skin and subcutaneous tissue, combined with adequate negative pressure drainage, effectively eliminates dead space and reduces the risk of recurrence.