Advanced Clinical and Radiological Features of Ankylosing Spondylitis: Relation to Gender, Onset of First Symptoms and Disease Duration.

To determine the frequency of advanced clinical and radiological features of AS with reference to gender, onset of symptoms and disease duration. Fifty-seven patients diagnosed with AS were included in this study. Functional evaluation of the musculoskeletal system detected advanced clinical features: rubber-ball phenomenon, flattening of the chest anterior wall, diastasis of rectus abdominis muscle, steel back phenomenon, umbilical extrusion, skiing posture. Conventional radiographs of sacroiliac joints, pelvis and axial skeleton were obtained in order to analyze signs of sacroiliitis, syndesmophytes, vertebral squaring and ligamentous ossification. Statistical significance is found in the distribution of particular advanced clinical and radiological features of AS between men and women: rubber-ball phenomenon (p = 0.002), flat chest (p = 0.002), diastasis of rectus abdominis muscle (p = 0.002), skiing position (p = 0.000), syndesmophytes (p = 0.009) and ligamentous ossification (p = 0.030) in thoracic and lumbar spine. Onset of first disease symptoms (> 20 years of age) is significantly associated with radiological changes in thoracic spine (ligamentous ossification, p = 0.015) and cervical spine (vertebral squaring, p = 0.032). Longer disease duration (> 10 years) is significantly associated with the appearance of particular clinical features: rubber-ball phenomenon, p < 0.01; rectus abdominis diastasis, p=0.042) and radiological changes of sacroiliac joints (grade IV sacroileitis, p = 0.012), thoracic and lumbar spine (syndesmophytes, p = 0.015; ligamentous ossification, p = 0.027). Our study shows that the occurrence of clinical and some radiological features of AS appears to be gender dependent. Furthermore, onset of first disease symptoms (> 20 years of age) and longer disease duration (> 10 years) are associated with the higher risk of developing particular clinical signs and radiological features in sacroiliac joints and axial skeleton.