<h3>Background</h3> Spondyloarthritis (SpA) refers to a group of related but phenotypically distinct disorders: psoriatic arthritis, arthritis related to inflammatory bowel disease, reactive arthritis, a subgroup of juvenile idiopathic arthritis, and ankylosing spondylitis. [1]. Patients with SpA can be distinguished, according to their clinical presentation, as axial SpA or peripheral SpA patients [2]. Each of these diseases is characterized by distinct clinical and laboratory characteristics, and each features a wide spectrum of clinical presentations, facts that highlight the dynamism and progression of SpA. <h3>Objectives</h3> To evaluate the diagnostic performance of radiography in the evaluation of enthesitis in the pelvis and its usefulness in the diagnosis of SpA. <h3>Methods</h3> This study was a historical cohort study from 2005 to 2020. Eligible patients were adults (≥18 years of age) with SpA according to the Assessment of Spondyloarthritis international Society (ASAS) criteria, and the control group were patients with chronic lumbar pain (more than three months) with non-inflammatory characteristics, without meeting ASAS criteria for SPA, and who assisted neurosurgery and rheumatology consultations in the Hospital Militar Central, Bogotá DC. The pelvic radiography had an anteroposterior view with gut preparation with laxative, the coccyx and pubic symphysis were aligned with the midline, and the distance between the tip of the coccyx and the upper limit of the coccyx was more than 2.5 cm. We used three zones of tendinous insertion in the pelvis. Zone one (ZI) is the iliopubic ramus; zone two (ZII) is the pubic symphysis; zone three (ZIII) is the ischiopubic ramus. In addition, a grading system was created from zero to four (grade 0: normal; grade I: periostial wishkering and/or osteopenia; grade II: periostial wishkering, osteopenia, sclerosis and erosions; and grade III: grade II findings in addition to the presence of ripple or waving patterns > 2 mm outside the cortex). The scores of each zone of the REI, without discriminating by laterality, were added to give the total REI as a result. <h3>Results</h3> The cohort have 450 patients, we selected 150 patients for the initial evaluation. Eleven (17.19%) were females and fifty-three (82.12%) were males. In the non-SpA, grade 0 was the most frequent in the three zones of REI, while grades II and III were more frequent in the SpA group; those outcomes were statistically significant. Zone III had the highest degree of enthesitis according to the REI classification (63.4%) in the SpA group, with a probability greater than 99% that these findings are related to SpA and not by chance. <h3>Conclusion</h3> Conventional pelvis radiography is still useful for SpA diagnosis, not just for sacroiliac joint and lumbar spine involvement assessment but also for the evaluation of the pelvic enthesis, which gives essential information for the diagnosis of SpA. <h3>References</h3> [1]Dougados M, Baeten D (2011) Spondyloarthritis. Lancet 377:2127–2137. https://doi.org/10.1016/S0140-6736(11)60071-8 [2]Rudwaleit M, van der Heijde D, Landewé R, et al (2011) The Assessment of SpondyloArthritis International Society classification criteria for peripheral spondyloarthritis and for spondyloarthritis in general. Ann Rheum Dis 70:25–31. https://doi.org/10.1136/ard.2010.133645 <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.
