Total Hip Arthroplasty in Patients with Ankylosing Spondylitis: Midterm Radiologic and Functional Results

Abstract

Introduction: Ankylosing spondylitis (AS) is characterized by progressive joint erosion and the incidence of hip involvement in AS is between 30%-50%. The aim of this study was to evaluate the clinical and radiologic outcomes of THA in patients with AS. Patients and Methods: Retrospective review was included all patients diagnosed with hip involvement of AS and treated with THA between 1997 and 2012. Dorr's classification of proximal femoral geometry, acetabular protrusio, bone ankylosis, acetabular protrusion ,Brooker classification of heterotopic ossification(HO), Gruen and Charnley classifications of implant loosening were included as radiographic assessments. Patients were called back to return for an additional long-term follow-up for functional assesment. Results: There were 61 patients with 105 affected hips (72% bilateral, 28% unilateral). The average patient age at surgery was 41.3±10.2. Cementless total hip arthroplasty was used in 83 hips(79%) and cemented TKA was used in 22 hips(21%). The overall rate of aseptic loosening was 7.6% at a mean follow-up of 5.4 years. Femoral loosening was statistically similar in cemented and cementless femoral components(14% vs. 8%,p=0.089). Acetabular component loosening was statistically higher in patients with any degree of HO(p=0.04). Regardless of the type of femoral implant (cemented or cementless), femoral component loosening was higher in Dorr's type C patients(p=0.005). The average pre-operative HSS was 46.6±16.3, and it improved to 80.7±18.7 at last follow-up(p<0.01). Conclusion: Revision incidence was similar in between ankylosed and non-ankylosed hips. Complication rates are high but significant functional improvement can be achieve after THA in patients with AS. Level IV study DOI: 10.3944/AOTT.2015.16.0286 This abstract belongs to the un-edited version of the article and is only for informative purposes. Published version may differ from the current version.