National trends and in hospital outcomes for total hip arthroplasty in avascular necrosis in the United States

While a majority of total hip arthroplasty (THA) is performed for osteoarthritis (OA), a significant portion is performed in the setting of avascular necrosis (AVN). The purpose of this study is to evaluate recent trends, patient demographics, and in hospital outcomes for primary THA in the setting of AVN in the United States. The National Hospital Discharge Survey database was searched for patients admitted to US hospitals after a primary THA for the years 2001-2010. Patients were then separated into two groups by ICD-9 diagnosis codes for OA and AVN. The rates of THA for AVN (r = 0.65) and THA for OA (r = 0.82) both demonstrated a positive correlation with time. The mean patient age of the AVN group was significantly lower (56.9 vs 65.9 years, p < 0.01). Men accounted for 51.9 % of the AVN group and 43.0 % of the OA group (p < 0.01). The AVN group had a significantly higher percentage of African Americans (11.2 % vs 5.4 %, p < 0.01) when compared to the OA group. The AVN group had a higher rate of myocardial infarction (0.3 % vs 0.07 %, p = 0.0163) and a higher average number of medical co-morbidities (5.16 vs 4.77, p < 0.01). Patients undergoing THA for AVN were more likely to be younger, male, African American, have more medical co-morbidities, and more likely to have a myocardial infarction than those with OA. While the number of primary THAs performed for AVN in the United States has increased over the past ten years, the rate of primary THA for OA increased at a much more rapid rate.