Tumor necrosis factor inhibitors prevent structural damage in hips in ankylosing spondylitis-time to reconsider treatment guidelines? A case series and review of literature

Tumor necrosis factor inhibitors (TNFi) are indicated to treat ankylosing spondylitis (AS), also termed radiographic axial spondyloarthritis (axSpA). The main indication for TNFi is symptom relief, and whether they retard spinal structural damage as assessed by radiography is debated. Hips are the most common "non-spinal" joints involved in AS patients leading to major incapacitation. No major treatment guidelines mention measures to prevent peripheral joint damage, especially hips, in individuals with AS. We present our experience of prevention of structural damage in hips by TNFi in 4 AS patients from our practice. We conducted a literature review looking for articles describing prevention of structural damage progression in hips by TNFi. Over a 10-year period, three out of four patients were treated with TNFi and had no progression in hip damage as assessed by imaging. Only one patient that withdrew the TNFi due to infectious complications developed rapid worsening and required hip arthroplasty. Our literature review showed multiple case series with similar results suggesting that use of TNFi in patients with AS may prevent structural damage and at least postpone a hip replacement at a young age. Based on our experience, as well as from the literature review, we believe that treatment guidelines in axSpA should recommend prompt institution of TNFi following identification of hip involvement in patients to prevent a major source of disability. Whether interleukin (IL)-17 inhibitors or targeted synthetic anti-rheumatic drugs have hip sparing effects in patients with AS should also be investigated. Key Points • Hip involvement in ankylosing spondylitis is a major source of disability. • TNFi prevent hip damage in ankylosing spondylitis. • Prompt institution of TNFi should follow suspicion of hip involvement in ankylosing spondylitis.