Presentation
Left hip and lower back pain for 2 years. No history of trauma.
Patient Data
Ill-defined mixed sclerotic and lytic lesion of the left femoral head. The articular surface of the left femoral head is flattened in keeping with articular collapse.
No significant left hip joint space narrowing. No osteophytes seen.
Right femoral head is normal.
Irregular cortex with flattening and collapse of the superior part of the femoral head.
Geographic hypointense area on both T1WI and T2WI noted to occupy the whole superior part of the femoral head. It occupies about 75 % of the weight-bearing surface.
"Double-line" sign noted on both T2WI and STIR sequences is pathognomonic for avascular necrosis on an MRI scan. Minimal peripheral enhancement of the abnormal intensity area noted, which can represent the granulation tissue. The left hip joint space is preserved. No secondary degenerative osteophytes.
Adjacent inflammatory left joint hip effusion and left femoral head bone marrow edema noted. No abnormal synovial thickening or enhancement.
Acetabulum margin is normal.
Case Discussion
Left femoral head avascular necrosis. (Stage 3, Ficat and Arlet classification) (stage D Mitchell classification for AVN). The lack of high T2 signal intensity and collapse of the left femoral head are suggestive of longstanding nature of avascular necrosis, No secondary degenerative osteoarthritic changes.