Lumbar disc herniation in ankylosing spondylitis - A dual role of discovertebral enthesopathy

Lumbar disc herniation (LDH) is rare in patients with ankylosing spondylitis (AS). Discovertebral enthesopathy is a characteristic feature of AS. The aim of this study was to determine whether there was a relationship between LDH and discovertebral enthesopathy. Sixty-six patients with AS were included in this study. Magnetic resonance imaging was taken to detect LDH. The clinical and radiologic objective findings of lumbar discovertebral enthesopathy (limitation of lumbar spinal motion in sagittal and frontal planes, vertebral squaring, discovertebral erosions, syndesmophytes, and bamboo spine) were assessed. The vertebral squaring, discovertebral erosion, syndesmophyte, and bamboo spine were evaluated by plain x-ray of lumbosacral spine. Seven (10.6%) patients had LDH. Forty-six patients had limitation of lumbar spinal mobility. Fifty-two cases had vertebral squaring, 9 discovertebral erosions, 28 syndesmophytes, and 11 bamboo spines. A risk for LDH in relation to discovertebral enthesopathy was found to be higher in patients with than in those without discovertebral erosions (odds ratio = 28.42, P = 0.004), to be lower in patients with than without the limitation of lumbar spinal motion (odds ratio = 0.009, P = 0.001), and vertebral squaring (odds ratio = 0.048, P = 0.009). The present study suggests that the discovertebral enthesopathy may have a dual effect on LDH development in patients with AS.