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.