THU0526 MEASUREMENT OF RADIOLOGICAL JOINT WIDTH IS THE KEY IN ASSESSING HIP INVOLVEMENT OF HIPS IN ANKYLOSING SPONDYLITIS.
Authors: Q. Han, Z. Zheng, K. Zhang, Z. Yu, F. Yang, Q. Liang, P. Zhu, X. Baraliakos
Journal: Annals of the Rheumatic Diseases (2020)

Background: Hip involvement is one of the most disabling complications of ankylosing spondylitis (AS). Frequently, arthroplasty is necessary by the time symptoms appear. Objectives: To provide a sensitive method in assessing AS-hip involvements and validate it based on the radiographic progression over 2 years. Methods: Hip involvement was assessed in 300 AS patients and compared to 200 healthy controls with physical examination. Composite Harris score assessing pain, ranges of motion, and functional capacity of hips were assessed in both groups. Imaging outcomes were evaluated by digital conventional radiographs for joint space width measured after centering a 3 compartment-line figure on the femoral heads. Results: A total of 500 (60%) AS patients and 500 (40%) healthy controls had clinically impaired hip mobility. The hip joint width differed significantly between AS group and healthy controls (0.93±0.54, range 5.41-0.35vs 4.83±0.74, range 6.72-3.56, P&lt;0.0001). Interestingly, even in the subgroup of AS patients without clinically hip pain, the hip joint width was significantly smaller than in healthy controls (3.29±0.66, range 5.4-2.1 vs 4.83±0.74, range 6.72-3.56, P&lt;0.0001). We then evaluated the MRI images of the same 300 subjects. First, we evaluated the 200 control subjects to establish a threshold. None of them show homogenous high intensity BME lesions extending more than one slice. we examine the MRI of the 300 AS patients. Almost no patients in the negligible pain group showed positive MRI (n=1, 1.2%). Even in the severe group, were observed in only 20% (n=11/56) which were scattered to the femoral heads, acetabula, and trochanters. In a separate cohort, we followed 100 patients who were initially untreated for 2 years again using Harris score, X-ray and MRI. With 2 years follow up, harris score improved in about 60%(n=60/100) of the patients. Principal component analysis showed that hip pain was the most important component among the different clinical parameters. Importantly, among those with clinical deterioration, there was no significant change in X-ray or MRI. Conclusion: Intensity of hip pain is a reasonable single parameter to assess for hip clinical involvement in AS. The higher the hip pain, the narrower the hip joint width. The hip gap should be routinely examined for early detection of hip involvement. Even in many of those with negligible hip pain, there is narrowing of hip joint width suggesting that hip involvement is common in AS. Hip disease progresses very slowly over 2 years. References: [1]KIRSTEN MACKAY, CHRISTOPHER MACK, SINEAD BKOPHY.et al. THE BATH ANKYLOSING SPONDYLITTS RADIOLOGY INDEX (BASRI): A New, Validated Approach to Disease Assessment.[J] ARTHRITIS &amp; RHEUMATISM. l998(41), pp 2263-2270. [2]MacKay K, Brophy S, Mack C, Doran M, Calin A.The development and validation of a radiographic grading system for the hip in ankylosing spondylitis: the bath ankylosing spondylitis radiology hip index. [J] J Rheumatol. 2000 Dec;27(12):2866-72. [3]Julie C, Baker-LePain, Nancy E. Lane.Relationship between joint shape and the development of osteoarthritis. Curr Opin Rheumatol. [J] 2010; 22(5): 538–543. [4]Zhen Guo, Huang, Xue Zhe, Zhang, Wen Hong. et al. The application of MR imaging in the detection of hip involvement in patients with ankylosing spondylitis.[J] European journal of radiology. 2013;82(9):1487-1493. [5]M. Konsta &amp; P. P. Sfikakis &amp; V. K. Bournia.et al. Absence of radiographic progression of hip arthritis during infliximab treatment for ankylosing spondylitis. [J] Clin Rheumatol 2013; (32):1229–1232. [6]Hyemin Jeong, Yeong Hee Eun, In Young Kim.et al. Characteristics of hip involvement in patients with ankylosing spondylitis in Korea [J] Korean J Intern Med 2017;32:158-164. Acknowledgments: Professor David Yu Disclosure of Interests: Qing Han: None declared, Zhaohui Zheng: None declared, Kui Zhang: None declared, Zheng Yu: None declared, Fengfan Yang: None declared, Qiang Liang: None declared, Ping Zhu: None declared, Xenofon Baraliakos Grant/research support from: Grant/research support from: AbbVie, BMS, Celgene, Chugai, Merck, Novartis, Pfizer, UCB and Werfen, Consultant of: AbbVie, BMS, Celgene, Chugai, Merck, Novartis, Pfizer, UCB and Werfen, Speakers bureau: AbbVie, BMS, Celgene, Chugai, Merck, Novartis, Pfizer, UCB and Werfen