SUMMARY OBJECTIVE:

Our study aimed to explore the potential risk factors for radiological hip joint involvement in patients with ankylosing spondylitis (AS).

METHODS:

This cross-sectional convey collected the clinical data, laboratory indicators, and radiographic data of patients with AS. Radiographic hip joint involvement was defined as a Bath Ankylosing Spondylitis Radiology Hip Index (BASRI-hip) score ≥2. Multivariate logistic regression analyses were conducted to explore the potential risk factors for radiological hip involvement in patients with AS.

RESULTS:

Based on BASRI-hip score, all enrolled 386 patients with AS were classified as patients involving with radiological hip joint involvement (BASRI-hip ≥2; n=203) and those without it (BASRI-hip ≤1; n=183). Mean age of enrolled patients with AS were 36.7±11.9 years, and 320 (82.9%) patients were male. Mean course of disease was 10.7±8.3 years, and 349 (90.4%) patients were with a positive HLAB27. Multivariate analyses indicated that Juvenile onset (onset age ≤16 years) (odds ratio [OR]=4.159, 95% confidence interval [CI], 1.779-9.721, p<0.001), body mass index (BMI) <18.5 kg/m2 (OR=1.986, 95%CI 1.187-3.323, p=0.009), continuous nonsteroidal anti-inflammatory drug (NSAID) use (OR=0.351, 95%CI 0.155-0.794, p=0.012), and bone mass below the expected range for age (Z score ≤-2) (OR=2.791, 95%CI 1.456-5.352, p=0.002) were independently associated with radiological hip joint involvement in patients with AS.

CONCLUSIONS:

The potential risk factors for radiological hip joint involvement were juvenile onset, lower BMI, and bone mass below the expected range for age. Furthermore, continuous NSAID use was the protective factor for radiological hip joint involvement in these population.