Radiology Rounds
Round # 14
Correct Diagnosis: Idiopathic Transient Osteoporosis of the Hip
Discussion:
Idiopathic Transient Osteoporosis of the Hip is a rare and often unrecognized cause of hip pain in otherwise healthy young adults. The condition typically affects middle-aged men and women in the third trimester of pregnancy. Symptoms often present insidiously with pain developing in the affected hip, followed by progressive gait disturbance and functional disability. The diagnosis is suggested once other more common causes of hip pain in young adults are ruled out, such as stress fractures, infections, and malignancy. Laboratory findings are usually normal, although slight elevations in the ESR are sometimes seen. Radiographs may initially be unremarkable, but marked localized demineralization can usually be seen within 1 month of symptoms onset. The diagnosis can be confirmed by T1 and T2-weighted MRI, which usually demonstrates characteristic hypointense T1 and hyperintense T2 signal of the affected region.
Most cases resolve spontaneously within 6-12 months regardless of therapy. Multiple therapeutic modalities have been described, including NSAIDs, calcitonin, intravenous/oral bisphosphonates, steroids, sympathetic blockade, casting, and rest. Recovery is noted radiographically as well, with complete remineralization of the previously osteoporotic area.
The etiology of this rare condition is unknown, but several hypotheses have been proposed. These include mechanical compression of local nerves, fibrinolytic system abnormalities leading to early AVN, unmasking of pre-existing subclinical osteoporosis in young women, and the development of regional neuropathies. However, none of these theories adequately account for the transient nature of the condition.
References:
- Bijl M, van Leeuwen MA, van Rijswijk MH.Transient osteoporosis of the hip: presentation of (a)typical cases and a review of the literature. Clin Exp Rheumatol 17(5): 601-4, 1999.
- Arayssi TK, Tawbi HA, Usta IM, Hourani MH. Calcitonin in the treatment of transient osteoporosis of the hip. Semin Arthritis Rheum 32(6): 388-97, 2003.
- Schapira D. Transient osteoporosis of the hip. Semin Arthritis Rheum 22(2): 98-105, 1992.
- Schapira D, Braun Moscovici Y, Gutierrez G, Nahir AM. Severe transient osteoporosis of the hip during pregnancy. Successful treatment with intravenous biphosphonates. Clin Exp Rheumatol 21(1): 107-10, 2003.
