Teaching Case

A 38 years old male patient referred with disabling pain in the right hip without a history of underlying trauma or infection. Pelvic X-ray films were within the normal limits.

A 38 years old male patient referred with disabling pain in the right hip without a history of underlying trauma or infection. Pelvic X-ray films were within the normal limits. MRI study of the hips was performed on a 1.5 T MR scanner with SE T1, fat-suppressed FSE T2 weighted sequences on three orthogonal planes. There was bone marrow edema pattern on the right femoral head and neck with slightly low signal intensity on T1- weighted images, high signal intensity on T2-weighted images. And also, T2 weighted images demonstrated synovial effusion in the joint space. Scintigraphy demonstrated intense uptake of Tc-99m MDP in the affected right femoral head and neck, corresponding to the region of abnormal signal intensity on MRI. A conservative management was tried for the patient. The control MRI and scintigraphic examination of patient showed total resolution of the findings on 3rd month when the clinical findings also totally disappeared.

Transient bone marrow edema syndrome (BE) is a rare benign condition characterized by progressive disabling pain in joints, especially involving the hips. The etiology of BE is still unknown. Although the condition was first described in pregnant ladies, it is generally seen in middle aged men. There is usually no abnormal finding on X-ray films, but osteopenia may be seen in femur and acetabulum. Bone scintigrams demonstrate intense uptake of Tc-99m MDP around the affected joint. MRI findings of BE is characterized by a nonspecific ill–defined marrow area of low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. The histopathological findings may reveal immature fibrovascular tissue, inflammatory tissue, and bone marrow necrosis. The differential diagnosis involves epiphyseal stress fracture, epiphyseal osteonecrosis, osteomyelitis, and infiltrative tumor. The distinction between these entities is very important because of considerable differences in treatment and prognosis. BE and stress fracture are self-limiting diseases which do not require surgical treatment. BE is differentiated from osteonecrosis by demarcation subchondral abnormalities which is characterized by decreased signal on T1-weighted images and increased signal on T2-weighted images. Mitchell et al described pathognomonic ’’double line sign’’, characterized by a high signal intensity rim inside a low signal margin, surrounding the osteonecrotic lesion on T2-weighted images. Transient ischemic osteoporosis (TIO) is a clinical entity that demonstrates the BE pattern. It is characterized by marked osteoporosis of the spongious bone on standard radiographs. Osteomyelitis may easily extend to the epiphysis in adults, but periosteal reaction and involvement of soft tissue help distinguish osteomyelitis from BE. An infiltrative tumor often demonstrates more focal signal changes, and may cause cortical destruction and an associated soft tissue mass. The treatment of BE is conservative with spontaneous resolution within 6 to 12 months. Finally, in the proper clinical setting (middle aged male or pregnancy), MR images are specific ( location, ill defined morphology) and allow diagnosis of BE so that inappropriate surgical intervention for this reversible disease can be avoided.