MRI OF THE OSTEOPHYTOSIS IN EXPERIMENTAL OSTEOARTHRITIS OF THE KNEE

Purpose: The value of MRI for the detection of knee osteophytosis was determined in an animal osteoarthritis model. Methods: 10 dogs with ex perimentally induced unilateral osteoarthritis of the knee were invest igated with MRI including 2-D-spin echo (SE) and 3-D-gradient. echo (G E) imaging. The results were correlated with gross and histopathologic findings and with radiography. Results: Osteophyte formation appeared early in the osteoarthritic process. Pathological analysis yielded 65 osteophytes. With 3-D-GE imaging, 91 % of the osteophytes were detect ed, while 68 % were visible on 2-D-SE images. With two-level radiograp hy, 43 % of the osteo osteophytes were diagnosed. Additional use of tu nnel view and conventional tomography increased the detection rate to 65 %, Independent of the imaging technique, MRI revealed three differe nt signal patterns of the osteophyte bone structure, Compared with the histologically evident fat marrow content and the grade of bone scler osis, best agreement was achieved with 2-D-SE sequences. However, a di screpancy remained in 22 %. A fibrocartilaginous layer at the osteophy te surface could be delineated especially on 3-D-GE images. Conclusion s: MRI provides the highest standard in noninvasive diagnosis of osteo phytes in the knee. 3-D-GE imaging in particular can demonstrate early and small osteophyte formation.