Factors associated with blood loss in ankylosing spondylitis patients with hip involvement undergoing primary total hip arthroplasty: a cross-sectional retrospective study of 243 patients

Background Total hip arthroplasty (THA) can cause considerable blood loss and perioperative transfusion in ankylosing spondylitis (AS) patients. This study aimed to identify the factors related to blood loss in AS patients with hip involvement undergoing THA. Methods We analyzed 243 AS patients with advanced hip involvement undergoing primary THA from 2012 to 2017. Bilateral THA was performed by a one-stage operation during one general anesthesia session. The patients were divided into three groups according to the grade of blood loss, as determined by the Advanced Trauma Life Support hypovolemic shock classification system. Ordinal logistic regression was used to identify factors associated with blood loss in the patients. Results The proportion of patients who were male, underwent bilateral THA, had a hip range of motion (ROM) = 0[degrees], had a BASRI-hip score of 4, underwent iliopsoas and adductor release, and underwent autologous or allogenic transfusion increased significantly with the grade of blood loss, while that of the patients who received tranexamic acid (TXA) decreased significantly (P < 0.05). The preoperative hemoglobin (Hb) level, hematocrit level, and operating time also increased significantly with the grade of blood loss (P < 0.05). The ordinal logistic regression results identified the factors related to blood loss during THA in AS patients with hip involvement to be the male sex (odds ratio [OR] = 3.287; 95% confidence interval [CI] 1.022, 10.567), bilateral THA (OR = 13.896; 95% CI 4.950, 39.011), hip ROM = 0[degrees] (OR = 2.513; 95% CI 1.277, 4.946), an elevated erythrocyte sedimentation rate (ESR) level (OR = 3.042; 95% CI 1.320, 7.014), an elevated preoperative Hb level (OR = 1.043; 95% CI 1.017, 1.070), a long operating time (OR = 1.009; 95% CI 1.003, 1.016), and the administration of TXA (OR = 0.252; 95% CI 0.134, 0.472). Conclusions The male sex, bilateral THA, a hip ROM = 0[degrees], an elevated ESR level, a high preoperative Hb level, and a long operating time are risk factors associated with blood loss in AS patients with hip involvement undergoing THA, while the administration of TXA is a protective factor. These results might help determine the risk of bleeding in the perioperative assessment and develop more efficient blood management strategies for THA in AS patients with hip involvement. Keywords: Ankylosing spondylitis, Hip involvement, Total hip arthroplasty, Blood loss