Osteonecrosis of the femoral head. Pathogenesis and long-term results of treatment.

Except after trauma resulting in an intracapsular fracture of the femoral neck or dislocation of the hip, the causes of pathogenesis in osteonecrosis of the femoral head have yet to emerge. The circulation to the femoral head may be impaired severely following a traumatic episode. Staging of the pathologic process is important as the selection of the appropriate surgical treatment depends upon the stage at the time of diagnosis. Anteroposterior and lateral roentgenograms are sufficiently accurate to make the diagnosis in Stages II to V. Tomography or Magnetic Resonance Imaging (MRI) are prescribed when roentgenograms are consistent with Stage II disease. This recommendation is made because subtle changes may be present that are not apparent on the roentgenogram, such as fracture of the surface or beginning segmental collapse. These changes would change the classification to Stage III rather than Stage II. MRI or core biopsy is required for diagnosis in Stage I. Many surgical treatment options have been proposed for the treatment of osteonecrosis of the femoral head. No one operation has been shown to be superior. Most papers do not have sufficient long-term follow-up evaluation or a significantly large number of cases to allow one to draw firm conclusions about the efficacy of the operation. Total hip replacement or hip arthrodesis is the treatment of choice for the end stages of the disease when the hip joint has degenerated.