Early irreversible osteonecrosis versus transient lesions of the femoral condyles: prognostic value of subchondral bone and marrow changes on MR imaging.

OBJECTIVE: The purpose of this study was to determine the MR imaging features that enable differentiation between early irreversible osteonecrosis and transient lesions in nontraumatic lesions of the femoral condyle having the "bone marrow edema" pattern on MR imaging. MATERIALS AND METHODS: We reviewed 23 nontraumatic painful lesions of the femoral condyle in 23 patients (12 men and 11 women; mean age, 62 years). All patients had undergone radiography of the knee with findings that were normal or inconclusive. Also, all patients underwent MR imaging that revealed the bone marrow edema pattern in a condyle. Lesions observed after trauma, surgery, or glucocorticoid medication, or with epiphyseal collapse or degenerative joint disease on initial plain radiographs, were excluded from this study. Of the 23 lesions, 14 showed complete resolution (and were designated as transient epiphyseal lesions). The remaining nine lesions were irreversible and, on follow-up radiographic and MR imaging studies, evolved to collapsed osteonecrosis (and were designated as early osteonecrosis). The presence and size of the subchondral features observed by two radiologists on initial MR studies were compared for both irreversible and transient epiphyseal lesions. RESULTS: Initial MR imaging characteristics indicative of an early irreversible osteonecrosis included a subchondral area of low signal intensity on T2-weighted images with a thickness of more than 4 mm (sensitivity, 100% and 100%; specificity, 82% and 74% for the two observers) or a length of more than 14 mm (sensitivity, 89% and 88%; specificity, 93% and 87% for the two observers), focal epiphyseal contour depressions, and lines of low signal intensity located deep in the affected condyle. The extent of edema was similar for both transient epiphyseal lesions and early osteonecrosis. CONCLUSION: Careful assessment of MR imaging changes occurring in the subchondral area can enable confident differentiation between transient epiphyseal lesions and early irreversible osteonecrosis of the femoral condyle.

Stage I multiple myeloma: value of MR imaging of the bone marrow in the determination of prognosis.

PURPOSE: To determine the prognostic value of bone marrow findings at magnetic resonance (MR) imaging in patients with stage I multiple myeloma. MATERIALS AND METHODS: In 24 patients with stage I multiple myeloma, findings from MR imaging of the vertebral, pelvic, and femoral bone marrow were analyzed and correlated to spontaneous outcome. Progressive multiple myeloma was observed in 12 patients and stable stage I multiple myeloma was observed in 12 after a follow-up period of 4-67 months (median, 27 months). RESULTS: In 17 patients, MR imaging findings were normal, and in seven patients, bone marrow abnormalities were depicted on MR images. Of the 12 patients with progressive multiple myeloma, six had bone marrow abnormalities that were depicted at MR imaging. In the group of patients with progressive multiple myeloma, the six patients with abnormal MR imaging findings showed earlier disease progression (median, 10 months) than the six patients in whom MR imaging findings were normal (median, 32 months) (P < .0001). Multivariate analysis of clinical and MR imaging findings showed that MR imaging (P = .006) were two independent factors in the prediction of disease progression. CONCLUSION: MR imaging of the bone marrow in patients with stage I multiple myeloma is an independent factor in the prediction of disease progression.