Have the Yearly Trends of Total Hip Arthroplasty in Ankylosing Spondylitis Patients Decreased?

INTRODUCTION: Ankylosing spondylitis (AS) is characterized by spinal inflammation and structural damage, primarily to the axial skeleton and sacroiliac joints. Between 25% and 70% of patients may experience progressive peripheral joint involvement, which, despite advancement in pharmacologic therapy, may necessitate surgical intervention. Total hip arthroplasty (THA) yields improved pain and functional outcomes for AS patients with hip involvement. It is unclear whether the annual rates of patients undergoing THA have changed due to newer pharmacologic management. Therefore, the purpose of this study was to evaluate the annual trends of AS patients who underwent THA. Specifically, we evaluated: 1) the annual trends of THAs due to AS in the United States population, and 2) the annual trends in the proportion of THAs due to AS in the United States.

MATERIALS AND METHODS: This study used the Nationwide Inpatient Sample to identify all patients who underwent THA between 2002 and 2013 (n=3,135,904). Then, an additional query was performed to identify THA patients who had a diagnosis of AS, defined by the International Classification of Disease 9th revision diagnosis code 720. The incidence of THAs with a diagnosis of AS in the United States was calculated using the United States population as the denominator. Regression models were used to analyze the annual trends of AS in patients who underwent THA.

RESULTS: Review of the database identified 5,562 patients with AS who underwent THA. The overall annual prevalence of THA in the AS population significantly decreased during the 12-year study period from 2.24 per 1,000 THAs in 2002 to 1.73 per 1,000 THAs in 2013 (R2=0.445; p=0.018).

CONCLUSION: Annual THA trends in AS patients have significantly declined from 2002 to 2013. This decline may be attributed to improvements in medical management that delay the time from disease onset to requirement of a THA. Since THA is an option with advanced disease, the observed declining trends may indicate the efficacy of current medical management.