Avascular Necrosis of Femoral Head — Double Line Sign

A 38-year-old man with a 15-year history of systemic lupus erythematosus on long-term high-dose prednisolone (20 mg daily for 3 years) and heavy weekend alcohol use presents with progressive right groin pain exacerbated by weight bearing and internal hip rotation. Plain pelvic radiographs are unremarkable with preserved joint space. MRI T2-weighted coronal images show the pathognomonic double line sign of avascular necrosis of the right femoral head. The structure marked **B** in the diagram represents the inner hyperintense line. What tissue does this inner hyperintense line represent, and what is its pathophysiological significance in early-stage avascular necrosis?