Bilateral Knee Osteonecrosis in an Adolescent With Leukemia on Prolonged Corticosteroids: Discordant Femoral–Tibial Findings on Bone Scan SPECT – CT

ABSTRACT

Osteonecrosis (avascular necrosis, AVN) is a disabling complication of corticosteroid exposure and is well recognized in adolescents treated for hematologic malignancies, including acute lymphoblastic leukemia (ALL). We report a 17‐year‐old female with ALL and later acute myelogenous leukemia (AML) after hematopoietic stem cell transplantation (HSCT), who received documented post‐HSCT prednisolone therapy and presented with progressive bilateral knee pain. MRI demonstrated multifocal osteonecrosis involving both distal femoral condyles and proximal tibiae, with classic serpiginous infarct morphology and a double‐line sign. A [99mTc]‐MDP three‐phase bone scan with hybrid SPECT/CT demonstrated discordant activity: intense uptake and marked sclerosis in the femoral condyles but minimal uptake in the tibial lesions. This pattern may reflect heterogeneous lesion activity or different reparative stages rather than a validated predictor of collapse. The case highlights the potential value of bone scintigraphy/SPECT/CT as an adjunct to MRI for lesion activity mapping and surveillance planning in selected high‐risk pediatric oncology patients while emphasizing that its prognostic role requires longitudinal validation.