AB0886 Does radio-anatomic feature of hip arthritis in spondyloarthritis predict functional impairment?

Background Axial spondyloarthritis (AS) is a chronic inflammatory disease that primarily affects the axial skeleton. Hip involvement is common in AS patient. The reported prevalence of clinical hip involvement in AS ranges from 24% to 36% and prevalence of radiographic hip arthritis ranges from 9% to 22%.1, 2 Several radio-anatomic feature are described with often significant clinical impact. Objectives To assess for an association between the radio-anatomic feature of hip arthritis and its clinical impact in patients with AS. Methods Cross-sectional study including patients with AS according to the ,ASAS criteria of 2009 with hip arthritis. All patients had pelvic X-rays. This one allowed to distribute the patients according to five radio-anatomic feature of the hip arthritis: destructive, protrusive, ankylosing, mimicking osteoarthritis and early hip arthritis. To evaluate the functional impairement, two clinical indices were calculated: Lequesne index and Intermalleolar distance between the two medial malleoli in centimetre. The comparison of qualitative variables was performed with the Chi square test and the comparison of qualitative variable and quantitative ones was performed with the Student’s test. The significance level was set at 0.05. Results One hundred patients were included with 176 hips arthritis. The delay between onset of AS and hip arthritis was on average 5.6 years [0–34]. The distribution of coxitis according to the radio-anatomic feature was as following: destructive (110 cases), protrusive (10 cases), mimicking osteoarthritis (29 cases), ankylosing (7 cases) and early hip arthritis (20 cases). According to the Larsen classification for destructive hip arthritis: a grade 4 was found in 41 cases, a grade 2 in 33 cases, a grade 3 in 33cases and a grade 1 in 3 cases. The destructive form had the most important functional impairment with the highest Lequesne index in comparison with other forms (13,05 vs 9,7, p=0,000) and the smallest intermalleolar distance (74,40 vs 87,29, p=0,010). The early hip arthritis and protrusive forms had the least important functional impact in with the following scores: Lequesne index (8,83 vs 12,29, p=0,015) and (10,78 vs 11, 96, p=0,000) and the intermalleolar distance (76,36 vs 65,00 p=0,015) and (105,56 vs 70,22, p=0,002) respectively. Scores were comparables for osteoarthritis and ankylosing forms. Conclusions Our study showed that radio-anatomic feature of hip arthritis could influence functional impairment. Distinguishing these forms may allow the rheumatologist to select the hip arthritis that deserves more attention because of the highest risk of functional impairement. References [1] Jeong H, Eun YH, Kim IY, Kim H, Lee J, Koh EM, et al. Characteristics of hip involvement in patients with ankylosing spondylitis in Korea. Korean J Intern Med. 2017;32(1):158–64. [2] Zhao J, Zheng W, Zhang C, Li J, Liu D, Xu W. Radiographic hip involvement in ankylosing spondylitis: factors associated with severe hip diseases. J Rheumatol. 2015;42(1):106–10. Disclosure of Interest None declared