To investigate the efficacy and prognostic risk factors of total hip replacement (THR) in the patients with ankylosing spondylitis (AS) involving hip joint lesions.

The clinical data of 84 AS patients with hip joint lesions treated by cementless THR in Linyi Lanshan District People's Hospital from February 2016 to January 2019 were retrospectively analyzed. All the patients met the New York diagnostic criteria and the surgical indications, were accompanied with intolerable hip joint lesions, and accepted the primary THR. Exclusion criteria: allergic history to implants, severe femoral deformity, severe cardiac or renal diseases, incomplete data. Harris hip score, visual analogue scale (VAS score) and range of motion of hip were used to assess the prognosis of the patients. Paired t test was used for pairwise comparison. Univariate analysis of variance was used for multi-groups comparison. Rank sum test was used to analyze the related risk factors such as abnormal erythrocyte sedimentation rate, family history of rheumatism, age of onset and course of disease. Multivariate logistic regression analysis was used to analyze the independent prognostic factors.

The follow-up rate of 84 patients was 100%, and the average follow-up time was (35±6) months. The bone healing time was(3.5±1.2)months, and the excellent and good rate of hip function was 90.48% at the last follow-up. Harris score and total hip motions significantly increased at the last follow-up, VAS score and angles of joint flexion deformity significantly decreased (t=77.490, 54.360, 65.740, 105.100, all P<0.001). Before the treatment, the longer of the disease course, the Harris score was lower in the patients with family history of rheumatism and abnormal erythrocyte sedimentation rate (t=34.240, 4.246, 3.522, all P<0.001). After the treatment, the shorter of the disease course, the Harris score was the higher in the patients without family history of rheumatism and normal erythrocyte sedimentation rate (t=53.190, 8.642, 6.351, all P<0.001). The results of multiple logistic regression analysis showed that abnormal erythrocyte sedimentation rate, family history of rheumatism, onset age ≤50 years, course > five years of the disease were independent risk factors affecting the prognosis of AS patients with hip joint lesions (χ²=4.776, 6.138, 4.875, 4.135, all P<0.05).

Cementless THR can significantly alleviate the pain of AS patients involved hip joint lesions, improve hip function, and has a significant clinical effect. Preoperative abnormal erythrocyte sedimentation rate, family history of rheumatism, low age of onset and long course of disease are independent risk factors affecting the prognosis.