Nontraumatic Osteonecrosis of the Femoral Head: An Update.

➢ Nontraumatic osteonecrosis of the femoral head should be suspected in patients who are <50 years of age who have persistent hip pain despite normal radiographs.➢ Bilateral involvement is common; magnetic resonance imaging (MRI) of the contralateral hip is recommended.➢ MRI is the most sensitive modality for detecting early disease.➢ Femoral head sphericity is assessed on anteroposterior, lateral, and 30º view radiographs.➢ Small pre-collapse lesions have the best prognosis. Large lateral lesions and subchondral collapse predict rapid progression.➢ Systemic risk factors and multifocal disease should be actively evaluated.➢ Joint-preserving procedures are most effective before structural collapse.➢ Total hip arthroplasty remains the most reliable treatment after femoral head collapse.