A 9 year old caucasian girl presents with acute pain in her right hip for 1 day. She gives a history of chronic, progressively worsening pain in the same hip for the last 6 months. There is no history of trauma and she is otherwise asymptomatic. Her medical history is unremarkable and she is not on any medications.
WBC/DC: 7,800/mm3 Lymphocytes: 35% Neutrophils: 62% Hb: 12.2 g/dL Hct: 37% Platelets : 230,000/mm3
The ESR is 5 mm in the first hour (normal). The C-Reactive protein level is < 6 g/l (normal).
The X-ray of the right hip shows sclerosis and flattening of the right femoral head with early fragmentation. The lateral pillar height is decreased by < 50%. The pelvis and left hip appear normal.
The MRI shows flattening, sclerosis and early fragmentation of the right femoral head, with a small joint effusion. The double-line sign is present.