Sandra Moore MD, PRESENTER: Nothing to Disclose

Abstract: HTML Purpose: The association of so-called spontaneous osteonecrosis of the femoral condyle (SOFC) with meniscal tears, first reported by arthrography and recently by MRI, suggests loss of protective mechanism of the menisci promoting subchondral insufficiency fracture as the possible etiology. We undertook a retrospective study to determine the validity of this hypothesis through correlation of meniscal pathology with the stages of SOFC. Methods and Materials: Search of our electronic database identified 68 knee cases diagnosed as spontaneous osteonecrosis; we selected 48 cases fulfilling MRI criteria for this diagnosis, excluding those with knee surgery or risks for osteonecrosis. A 4-stage grading system was based on observation of lesion pattern. Grade1: ill-defined subchondral signal abnormality, Grade 2: focal subchondral signal abnormality, Grade 3: subchondral low signal with edematous rim, Grade 4: subchondral fracture line or collapse. Scans were assessed by consensus for lesion grade, location, size, and meniscal pathology by 2 experienced musculoskeletal radiologists and one musculoskeletal fellow. Results: MR studies of 48 patients, 31 women and 17 men, ages 25-83 years were reviewed. 42 lesions involved the medial femoral condyle, 4 the lateral femoral condyle, 2 multiple surfaces. 44 lesions were at weight bearing surfaces. Lesion size ranged from 0.5--2.3 cm in transverse, 0.8-3.4 cm in AP dimension. Seven Grade 1, nineteen Grade 2, eleven Grade 3, and eleven Grade 4 lesions were observed. 8 horizontal, 22 complex, 11 root and 7 radial meniscal tears, and 21 extruded menisci were noted. 89% of meniscal tears involved the medial meniscus posterior horn. Osteochondral lesion grade was significantly associated with increasing age (p=0.036), transverse size of lesion p=0.012, and meniscal tear type (p=0.012); 67% of the patients with complex and horizontal tears had grade 1 or 2 lesions. Grade 3 and 4 lesions showed a higher percentage of meniscal extrusions and radial and root tears than complex and horizontal tears (but not a statistically significant correlation by lesion grade). Conclusion: The presumption of osteonecrosis of the knee is rarely subject to histological proof. The association of meniscal tears and location of SOFC strongly support osteochondral insufficiency fracture due to loss of meniscal protection as the etiology. Graded by severity, these lesions are more similar to traumatic lesions than osteonecrosis. Correlation with advanced age may indicate increasing susceptibility to osteoporotic fractures.      

Moore MD, S, Spontaneous Osteonecrosis of the Femoral Condyle: Is It an Insufficency Fracture? MRI Evaluation of Lesion Grade Correlated with Meniscal Pathology.  Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL. http://archive.rsna.org/2003/3104873.html