Distinguishing transient osteoporosis of the hip from avascular necrosis.
BACKGROUND
To review the circumstances surrounding the misdiagnosis of transient osteoporosis of the hip (TOH) as avascular necrosis (AVN) and to increase physician awareness of the prevalence and diagnosis of this condition in young men, we reviewed a series of cases seen in the orthopedic unit at St. Michael's Hospital, University of Toronto.


METHODS
We studied the charts of patients with TOH referred between 1998 and 2001 with a diagnosis of AVN for demographic data, risk factors, imaging results and outcomes.


RESULTS
Twelve hips in 10 young men (mean age 41 yr, range from 32-55 yr) were identified. Nine men underwent magnetic resonance imaging (MRI) before referral, which showed characteristic changes of TOH. All 10 patients were referred for surgical intervention for a diagnosis of AVN. The correct diagnosis was made after reviewing patients' charts and the scans and was confirmed by spontaneous resolution of both symptoms and MRI findings an average of 5.5 months and 7.5 months, respectively, after consultation.


CONCLUSIONS
Despite recent publications, the prevalence of TOH among young men is still overlooked and the distinctive MRI appearance still misinterpreted. Symptoms may be severe but resolve over time with reduced weight bearing. The absence of focal changes on MRI is highly suggestive of a transient lesion. A greater level of awareness of this condition is needed to differentiate TOH from AVN, avoiding unnecessary surgery and ensuring appropriate treatment.
Balakrishnan
Anita
A
Upper Extremity Reconstructive Service, St. Michael's Hospital and the University of Toronto, Toronto, Ont.
Schemitsch
Emil H
EH
Pearce
Dawn
D
McKee
Michael D
MD
D000328:Adult; D001851:Bone Diseases, Metabolic / Q000000981:diagnostic imaging; D003937:Diagnosis, Differential; D005271:Femur Head Necrosis / Q000175:diagnosis* / Q000000981:diagnostic imaging; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000175:diagnosis*; D011859:Radiography; D012189:Retrospective Studies; D012307:Risk Factors