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Background: Hip involvement is present in 25 to 35 percent of patients with ankylosing spondylitis (AS) and is associated with higher degrees of disability and a worse prognosis. Thus, early detection of hip arthritis is important for future prevention of disability.
Objectives: To predict the demographical, clinical and laboratory parameters related with hip involvement.
Methods: This study included 262 AS patients. Clinical, laboratory, and radiographic data were retrospectively analyzed. Bath AS radiology index (BASRI) hip index was used to define the radiological hip involvement. We also assessed Bath AS Functional Index (BASFI), Bath AS disease activity index (BASDAI), and Bath AS metrology index (BASMI). The AS disease activity scores (ASDAS) of the patients were calculated. Based on the radiographs, a score of at least 2 was used for the definition of hip joint involvement. Logistic regression analyses were used to investigate the factors associated with the severity of hip arthritis.
Results: There were 262 patients (men, 201, 76.7%). Mean age and disease duration of the patients were 44±11 and 19±10 years respectively. 57 patients (21.8%) had radiographic hip involvement and 135 (54.2%) patients had syndesmophytes. Comparison of radiological hip arthritis patients with no hip disease showed that hip arthritis group had significantly higher disease duration, male predominance, reported higher frequency of groin pain, increased BASMI, BASFI, CRP and ASDAS-CRP values (P <0.05). On the other hand, intermalleolar distance was significantly shorter and frequency of syndesmophytes were significantly higher in patients without hip arthritis group compared to those with hip arthritis patients (P<0.05). Other demographic and clinical features of groups are presented in table 1. Male sex, disease duration, presence of syndesmophytes, history of groin pain, inter-malleolar distance, BASMI, BASFI, CRP, ASDAS-CRP showed significant correlations with BASRI-hip (P<0.05, r =0.1, 0.2, 0.2, 0.2, -0.5, 0.4, 0.3, 0.3 and 0.2 respectively). Regression analysis showed that only male sex, history of groin pain, intermalleolar distance, and BASFI variables were predicting the radiological hip involvement (beta =32.3, 5, 0.93, and 1.42).
Table 1. Demographic and clinical features of the groups
Patients with radiographic hip involvement Patients with no radiographic hip involvement P (n=57) (n=205) Age, mean ± SD 47±14 43±10 0.066 Males, n (%) 50; 87.7 151; 73.7 0.026 Symptom duration, years, mean ± SD 24±11 18±10 <0.001 Ever smoker, n (%) 38; 66.7 153; 75.4 0.189 Education level, years, mean ± SD 8.5±4.2 9.7±3.8 0.056 Frequency of groin pain, n (%) 40; 87.7 128; 62.4 <0.001 Intermalleolar distance, cm, mean ± SD 78±22.6 110±19.7 <0.001 Sindesmofit any, n; % 40; 75.5 95; 48.5 <0.001 BASMI, mean ± SD 5.7±1.8 3.4±1.6 <0.001 BASFI, mean ± SD 4.7±2.9 2.3±2.1 <0.001 BASDAI, mean ± SD 3.7±2.3 3.2±2.1 0.127 CRP, mean ± SD 47.7±37.8 26.1±30.4 <0.001 ASDAS-CRP, mean ± SD 3.2±1.2 2.6±1.1 0.001 HLA B 27, n; % 18; 66.7 80; 73.4 0.486
Conclusions: Hip involvement is present about one out of the five patients with AS and is associated with male sex, impaired functioning reflected by higher BASFI scores, limitation of hip movement assessed by intermalleolar distance and clinical history of groin pain.
Disclosure of Interest: None Declared