Aneurysmal Bone Cyst Expansile

A 14-year-old girl presents with a 3-month history of slowly enlarging painful swelling over the outer aspect of the right knee just below the joint line. Examination reveals a firm, non-pulsatile swelling over the proximal fibula with intact neurovascular function. Radiographs show a well-defined eccentric expansile lucent lesion marked **A** in the diagram, arising from the metaphysis with internal soap-bubble septations, a thin ballooned cortical shell, no matrix mineralisation, and a narrow zone of transition. MRI confirms multiple fluid-fluid levels with a thin peripheral rim. Which of the following is the most appropriate definitive management for this lesion?