Table 2 Diagnostic criteria
Clinical features | Pain is primarily localized in the hip, occasionally accompanied by leg and knee pain, most of the patients shows limited hip internal rotation. Patients often have a history of practice of high impact sports, smoke exposure, and deprivation |
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X-ray imaging | Anteroposterior and frog-leg positioning are the basic X-ray positions used for diagnosis of ONFH, and the X-ray manifestations are typically osteosclerosis, cystic change, and a “crescent sign” in earlier stages. After collapse, there is a loss of sphericity of the femoral head and degenerative arthritis in the late stages (Fig. 2A, B) |
Magnetic resonance imaging | MRI seems to be the best method, MRI may show proximal femoral abnormalities before radiography in the setting of Legg–Calvé–Perthes disease, allowing appropriate diagnosis and prompt treatment. MRI can also assess for revascularization, healing, and multiple complications. MRI examination has a high sensitivity for ONFH, demonstrated as a limited subchondral linear-shaped low signal intensity in T1-weighted images (T1WIs) or a “double-line sign” in T2-weighted images (T2WIs) |
Computed tomography scanning | Computed tomography (CT) scanning usually reveals zones of osteosclerosis surrounding the necrotic bone and repaired bone or shows subchondral bone fracture |