To evaluate peri-operation period management, operation strategy and the medi-term effectiveness of total hip arthroplasty in the treatment of ankylosed hip complicated with protrusio acetabuli in later stage of ankylosing spondylitis(AS) .

Between July 2003 and October 2013, 19 cases (23 hips with four bilater hips) of ankylosed hip complicated with protrusio acetabuli, all met the diagnostic criteria of 2010 ankylosing spondylitis diagnostic criteria of Assessment of Spondylo-Arthritis International Society(ASAS). The patients were treated with cementless total hip arthroplasty , 16 males and three females, with an average age of (41.5±0.5)years (range, 32~65 years). The AS disease duration was (22.3±1.3) years (range, 10~42 years). Clinical results were evaluated by Harris scores and total range of motion (ROM) were assessed. The Harris scores and ROM before and after the operation were analyzed by paired sample t-test.

Only 17 patients were followed up for (45.2±2.7)months. The pain score at the last follow-up was(40.50±0.71), which was significantly higher than the preoperative one(11.80±3.32)(t= 11.17, P <0.01). The hip joint function score increased from preoperative (7.10±1.10) to postopreative(39.70±2.02); the difference was statistically significan(t=8.83, P<0.01). The X-ray showed that all the acetabular prostheses were in true acetabulum, and bone graft healed with no sign of re- protrusion. ROM was also significantly improved after the operation (t=8.78, P <0.01).

Total hip arthroplasty is safe and effective treatment of AS complicated with protrusio acetabuli with cementless prosthesis and bone grafting, which may have satisfactory mid-term clinical results.