Total hip arthroplasty in Japanese patients with ankylosing spondylitis

The purpose of this study was to examine the postoperative results following THA for ankylosing spondylitis, which is very rare in Japanese. We performed uncemented THA in 31 hips between 1982 and 2007. Patients were followed up for a mean of 12 years. The 10-year survival rate was 100%, and the 15-year survival rate was 63.5%. Revision surgery was performed in 4 hips. Complications developed in 5 cases. Two patients sustained an intraoperative non-displaced fracture at the level of the calcar femorale. Three patients experienced postoperative dislocation. Although the study scale was small because of the very low prevalence (0.0065%) of the disease in Japan, the survival rate was similar to those reported overseas. All revision cases were due to mechanical loosening of the acetabular component of Lord THA, suggesting that the low survival rate was due to the performance of the prosthesis and not the pathology of ankylosing spondylitis.