Synchronous or sequential cementless bilateral total hip arthroplasty for osseous ankylosed hips with ankylosing spondylitis: a retrospective cohort study

Abstract Purpose cementless total hip arthroplasty (THA) for bilateral osseous ankylosed hips with ankylosing spondylitis (AS) is a challenging procedure. No literature compares the clinical outcomes of synchronous and sequential bilateral THA of these special patients. Methods 23 patients (46 hips) were retrospectively analyzed and classified into receiving bilateral THA synchronously (group A) and receiving bilateral THA sequentially (group B). The clinical measurement, radiological assessments and complications were compared. Independent sample T test were used for data analysis. Results Harris Hip Scores (HHS) improved greatly for both groups (P = 0.58) as well as the range of motion (P = 0.64). But group B can realize shorter time (3.6 ± 1.2 days) to walk for the first time postoperatively (P = 0.02). The group A need more blood transfusions (P = 0.028). For group A, no statistic difference was found in bilateral inclination of cup (IC) (P = 0.48) and femoral offset (FO) (P = 0.07). For group B, no statistic difference was observed in bilateral IC (P = 0.37) but in bilateral FO (P = 0.04). The group A showed fewer difference of bilateral IC (P = 0.02), while comparative measurements for two groups in the difference of bilateral FO (P = 0.78) and leg length discrepancy (P = 0.83). For group A, one patient encountered femoral fracture intraoperatively and one patient encountered hip dislocation and delay union of wound as well as three hips encountering heterotopic ossification (HO). For group B, only three hips encountered HO. Conclusion Cementless bilateral THA was a safe and effective technique to improve hip function for patients diagnosed with osseous ankylosed hip due to AS. Synchronous bilateral THA can realize good clinical outcomes and more superior radiographic evaluation compared to sequential bilateral THA.