Delayed Nodular Cystic Fat Necrosis and Calcified Oil Cyst Formation Following Conservative Management of a Morel-Lavallée Lesion: A Case Report

Morel-Lavallée (ML) lesions are post-traumatic closed degloving injuries. We present the case of a 35-year-old female patient who developed a bulging mass and depressed contour deformity on her left posterior proximal thigh 1 year after a motor vehicle accident. While the patient’s acute ML lesion initially responded well to conservative compression therapy, ultrasound assessment at her delayed presentation 1 year later demonstrated multifocal hypoechoic lesions with thick, hyperechoic rims within the deep subcutaneous layer. Surgical exploration and gross pathological examination confirmed the presence of nodular cystic fat necrosis alongside distinct calcified oil cysts firmly attached to the peripheral fascia. Complete en bloc excision of the cysts, including their thick fibrous capsules, followed by meticulous dead space obliteration, insertion of a Penrose drain, and primary repair, was performed to restore the contour. This case highlights the need for vigilance regarding delayed complications that can occur long after the initial conservative management of ML lesions. It demonstrates that when chronic inflammatory changes progress to calcified, encapsulated soft-tissue complications, appropriate surgical intervention, including complete en bloc excision of the cysts and meticulous dead-space obliteration, can be effective for optimal soft-tissue reconstruction.