IMAGING

DETECTION OF SUBCHONDRAL FRACTURES IN OSTEONECROSIS OF THE FEMORAL HEAD: COMPARISON OF CONVENTIONAL RADIOGRAPHY, CT AND MRI

Philipp Lang, Shi-Uk Lee, Kathryn Stevens, Natalie Salem, Caroline Tao, Calise Cheng, Alexandre-Valentin-Opran
Department of Radiology, Stanford University Medical Center, Stanford, CA 94305, Genetics Institute, Cambridge, MA 02104

Purpose: Compare x-ray, CT and MRI sensitivity in detecting subchondral fractures in osteonecrosis.

Methods: 45 patients enrolled in a multicenter study to evaluate the effectiveness of rhBMP-2 as an adjuvant treatment to core decompression were evaluated at 6 and 12 months with x-ray, CT, and MRI.

Results:

On MRI subchondral fractures were depicted as a high signal intensity line (fluid signal) on T2-weighted scans. In all patients that demonstrated the high signal intensity line on T2-weighted MRI scans, CT showed a break in the subchondral bone.

Conclusion: CT has the highest sensitivity in detecting subchondral fractures. The high signal intensity line seen on T2-weighted MRI scans appears to represent fluid accumulating in the subchondral fracture. While the fluid may extravasate from the distal bone marrow into the fracture, it may also be the result of an extension of the fracture through the overlying subchondral bone and cartilage.