Idiopathic Transient Osteoporosis of the Hip

56YOM presented with disabling left hip pain. Plain x-ray was normal. MRI shows high T2 and low T1 signal in left femoral head and neck down to the intertrochantric region. Follow up after 3 months shows marked clinical and radiological improvement.
ITOH:
-Usually is a self limited clinical entity of unknown cause.
-Although the underlying cause in not certain, a vascular basis almost certainly exists. There is some controversy as to whether ITOH represents a very early, reversible stage of AVN.
-Affects middle age men with M:F ratio 3:1. When women are affected; it is usually during 3rd trimester of pregnancy. Generally, only one hip is affected at a time. Recurrence in the same hip can occur.
-It resolves spontaneously within 6-8 months after protected weight-bearing and symptomatic support.
DD:
-AVN (Absence of subchondral low signal on T2WI or contrast enhanced T1WI suggests favorable outcome e.g. reversible diseases).
-Stress fracture.
-Septic arthritis.
Reference: Kaplan et al. Musculoskeletal MRI: Hips and Pelvis. W.B. Saunders,2001.
Credit: Dr Ahmed Haroun
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