From the Guidelines
Sacroiliac joint fusion occurs in approximately 30-50% of patients with ankylosing spondylitis, typically developing within 10-15 years after disease onset. This fusion represents a hallmark feature of advanced disease and results from chronic inflammation that leads to bone formation (ankylosis) across the joint. The process usually begins with bilateral sacroiliitis, which can be detected on imaging before clinical symptoms become severe. The progression to complete fusion varies significantly between individuals and depends on several factors including genetic predisposition (particularly HLA-B27 status), disease severity, age of onset, and treatment effectiveness.
Key Factors Influencing Sacroiliac Joint Fusion
- Genetic predisposition, especially HLA-B27 status
- Disease severity
- Age of onset
- Treatment effectiveness
Early and aggressive treatment with TNF inhibitors (such as adalimumab, etanercept, or infliximab) or IL-17 inhibitors (secukinumab) may slow or potentially prevent sacroiliac joint fusion by controlling inflammation before irreversible damage occurs, as suggested by the 2019 update of the American College of Rheumatology/Spondylitis Association of America/Spondyloarthritis Research and Treatment Network recommendations for the treatment of ankylosing spondylitis and nonradiographic axial spondyloarthritis 1. Regular monitoring with imaging studies like X-rays or MRI helps track disease progression and guide treatment decisions. Once fusion has occurred, it is irreversible, highlighting the importance of early intervention in ankylosing spondylitis management.
Treatment Recommendations
- Early and aggressive treatment with TNF inhibitors or IL-17 inhibitors
- Regular monitoring with imaging studies
- Consideration of treatment effectiveness and adjustment as necessary
The most recent guidelines, such as those from 2019, emphasize the importance of tailored treatment approaches based on the individual patient's disease characteristics and response to therapy 1. By prioritizing early intervention and closely monitoring disease progression, healthcare providers can optimize outcomes for patients with ankylosing spondylitis and potentially reduce the likelihood of sacroiliac joint fusion.
From the Research
Frequency of Sacroiliac Joint Fusion in Ankylosing Spondylitis
- The frequency of sacroiliac joint fusion in patients with ankylosing spondylitis is not explicitly stated in most of the provided studies 2, 3, 4, 5.
- However, one study suggests that sacroiliac joint fusion is associated with hip involvement in patients with ankylosing spondylitis 6.
- This study found that 38.8% of patients with ankylosing spondylitis had radiological hip involvement, and 88.5% of these patients were male 6.
- Logistic regression analysis identified older age, sacroiliac joint fusion, and pincer type as independent risk factors for hip involvement in patients with ankylosing spondylitis 6.
Sacroiliac Joint Fusion and Ankylosing Spondylitis
- One case report describes a 45-year-old male with newly diagnosed ankylosing spondylitis who already had fused sacroiliac joints, lumbar spine, and cervical spine 2.
- This case report suggests that sacroiliac joint fusion can occur in patients with ankylosing spondylitis, but does not provide information on the frequency of this occurrence 2.
- Another study discusses the use of tumor necrosis factor alpha inhibitors in the treatment of ankylosing spondylitis, but does not mention the frequency of sacroiliac joint fusion 3.
- A study on the feasibility of US-CT image fusion to identify the sources of abnormal vascularization in posterior sacroiliac joints of ankylosing spondylitis patients does not provide information on the frequency of sacroiliac joint fusion 4.
- A review of the use of TNF-α inhibitors in active ankylosing spondylitis treatment does not mention the frequency of sacroiliac joint fusion 5.