Multimodal imaging quantitation of the lesion size in osteonecrosis of thefemoral head

Early diagnosis of osteonecrosis of the femoral head is important for initi ating early treatment, which is associated with a more favorable outcome fo r patients. Confusion in evaluating the severity of the disease, and the cl inical outcome after treatment partially is attributed to the use of variou s staging systems that are based on qualitative rather than quantitative cr iteria. At the authors' institution, 45 patients (77 hips) with osteonecros is of the femoral head were evaluated using a multimodal imaging approach t hat included conventional radiography, bone scintigraphy, and magnetic reso nance imaging. A computerized image analysis program that allowed quantific ation of the lesion size on radiographs and magnetic resonance images was u sed. Measurements of the extent of involvement on radiographs and selected serial magnetic resonance images were compared in 33 hips (42.9%) before co llapse versus 44 hips (57.1%) after collapse. The size of the necrotic lesi on varied significantly according to the specific stage of disease. Quantif ication of the lesion during the course of the disease provided a record of the progression of osteonecrosis, despite a spurious stability in staging, In general, conventional radiography closely approximated measurements of the lesion size obtained by magnetic resonance imaging. Bone scintigraphy a nd magnetic resonance imaging were well suited for detection of osteonecros is at an early stage. Finally, precise quantification of the lesion size wa s an optimal preoperative means for evaluating the extent of involvement of the femoral head in the early and advanced stages of osteonecrosis.