Radiographic Findings. One of the hallmarks of ankylosing spondylitis is involvement of the sacroiliac joints, and this has been the key radiographic finding that is needed to help confirm the diagnosis. In patients in whom ankylosing spondylitis is highly suggested and the plain radiographs do not reveal sacroiliac joint involvement, MRI has become the test of choice because it is more sensitive than plain radiographs to detect early changes of sacroiliac joint involvement. The earliest sign of involvement on MRI is bone marrow edema of the sacroiliac joint.

In the early stage of the disease, the bone on both sides of the sacroiliac joint and the bony borders are indistinct (see Plate 5-31). Later, the cartilage space narrows and erosions appear in the bordering bone. In the late stages, radiographs show complete ankylosis of the sacroiliac joints (see Plate 5-30). After the disease has progressed to involve the lumbar and thoracic spine, the facet borders become indistinct; then the cartilage space appears narrowed, and, later, bony ankylosis is apparent. Ossification of the outer layers of the anulus fibrosus is usually first seen at the L1-2 and T11-12 levels; later, the perispinous calcification spreads upward and downward. In severe, advanced disease, the calcification is continuous throughout the spine, producing a “bamboo spine” radiographic appearance (see Plate 5-30). There are specific proliferative changes in the last stages of ankylosing spondylitis, such as syndesmophytes, bridging syndesmophytes, ankylosis of the facet joints, calcification of the anterior longitudinal ligament, and anterior atlantoaxial (C1-2) subluxation, that are characteristic. Fractures can also be seen on radiographs, because minor movements with little trauma in late-stage disease may lead to spinal fractures. In advanced disease, there is radiographic evidence of bony ankylosis in many facets, together with the perispinous calcification. Axial joints can also be affected in ankylosing spondylitis, which include the hips and shoulders, with radiographic changes that are similar to those seen in rheumatoid arthritis (see Plate 5-30).

Treatment/Prognosis. There has been remarkable advance in the management of ankylosing spondylitis over the past decade. The basis for these updates involves the development and validation of a new disease activity score and the new classification criteria for axial spondyloarthritis. New guidelines for the management of ankylosing spondylitis from the 2010 updated consensus of the ASAS/EULAR committee that include evidence-based disease management recommendations have been published. In general, the recommendations include a multidisciplinary approach using both pharmacologic and nonpharmacologic therapies. In addition, tailored approaches to manage ankylosing spondylitis now have included more focused treatment aimed at the predominant symptoms of ankylosing spondylitis, axial involvement, and enthesitis-related or predominantly peripheral arthritis. Extra-articular manifestations should also be treated. Although treatment of ankylosing spondylitis may be similar to that of rheumatoid arthritis in certain aspects, the new recommendations continue to recommend a very restricted role for traditional DMARDs, such as sulfasalazine or methotrexate, and systemic corticosteroids. When peripheral arthritis is predominate, sulfasalazine may be helpful; however, there are few high-quality, controlled trials of methotrexate in the treatment of ankylosing spondylitis. Regarding the recommendation for the use of anti–TNF-α agents, there are two changes. The use of anti–TNF-α agents is recommended for patients fulfilling modified New York criteria for definitive ankylosing spondylitis or the ASAS criteria for axial spondyloarthropathy. The pretreatment period using at least two NSAIDs before biologic therapy is significantly shorter—4 weeks, compared with 3 months. This leads to an earlier initiation of treatment within the ankylosing spondylitis disease spectrum.