LAUSR

Rationale: Myositis ossificans circumscripta (MOC) is a rare disorder that causes heterotopic bone formation in soft tissues. It usually occurs after trauma and affects large muscles of the extremities. MOC of the pectineus muscle is extremely rare and has not been reported to be treated surgically. Patient concerns: A 52-year-old woman presented with left hip pain and dysfunction 4 months after a traffic accident that caused pelvic and humeral fractures and cerebral hemorrhage. Diagnoses: Radiological imaging revealed isolated ossification of the left pectineus muscle. The patient was diagnosed with MOC. Interventions: The patient underwent surgical resection of the ossified pectineus muscle followed by local radiation and medical therapy. Outcomes: At 12 months postoperatively, she was asymptomatic and had normal hip function. No recurrence was observed on radiography. Lessons: MOC of the pectineus muscle is a rare condition that can cause severe hip dysfunction. Surgical resection combined with radiation and anti-inflammatory drugs can be an effective treatment option for patients who do not respond to conservative management.