637   Increasing Incidence of Avascular Necrosis of the Hip in HIV-Infected Patients.

J. C. Keruly*, R. E. Chaisson, and R. D. Moore.
Johns Hopkins Univ. Sch. of Med., Baltimore, MD.

Background:Avascular necrosis (AVN) of the hip has been reported increasingly in HIV-infected patients.

Methods:We assessed all cases of AVN which were diagnosed in the Johns Hopkins HIV Clinic Cohort from January 1995 through August 2000. Cases were identified by a review of all clinical diagnoses (based on clinical presentation of hip pain) and all radiology (hip x-ray, CT, or MRI).

Results and Conclusions:A total of 15 symptomatic AVN cases were diagnosed over 7900 person-years of follow-up time for an incidence rate of 1.9 per 1000 person-years. The population-based incidence of AVN is 0.04 per 1000 person-years (Bauer et al., Pharmacoepidemiol. Drug Safety9:187, 2000). There was a significant (p < 0.01) annual trend for 1995 through 2000 in diagnoses (1995: 0/1000 PY; 1996: 0.4/1000 PY; 1997: 1.0/ 1000 PY; 1998: 2.8/1000 PY; 1999: 3.6/1000 PY; 2000: 4.8/1000 PY). Compared to the rest of the cohort, factors associated included steroid use (34% of cases), CD4 <200 cells/mm³(60%) and time since HIV diagnosis >5 years (53%). There was not an association with age, race, sex, HIV transmission risk group, concurrent lipodystrophy, or hyperlipidemia or with use of a protease inhibitor (53% of cases), non-nucleoside (20% of cases), or specific nucleoside RTI compared to the rest of the cohort. Almost half of our AVN cases had never used a PI or NNRTI. The factors most strongly associated were low CD4 and length of time since HIV diagnosis, suggesting the etiologic importance of duration of HIV infection.