Spondyloarthritis is a chronic rheumatic disease that requires prolonged radiographic follow-up. This repetitive exposure to ionizing radiation puts at risk the radiosensitive organs exposed in the field of irradiation. A new low-dose imaging system has emerged. This technique, called EOS, offers the advantage of lower irradiation associated with high images quality. Our goal through this work was to evaluate the reliability of the EOS imaging system compared to conventional radiography in the evaluation of the structural damage of SpA.

Spondyloarthritis (SpA) is a chronic inflammatory disease that can affect the sacroiliac joints, the spine and / or the peripheral joints. It is characterized by a progressive and slow evolution over several years with a risk of ankylosis of the spine. It requires long-term follow-up of patients with repeated x-rays to assess structural damage. This repeated and cumulative exposure to radiation ionization puts at risk the radiosensitive organs that are in the field of irradiation.

EOS is a new low dose X-ray system that significantly reduces X-ray doses compared to conventional radiography. This system allows the global assessment of the entire skeleton from head to toe, static spine and lower limbs with the obtaining of two-dimensional images of high quality with the possibility of a three-dimensional reconstruction. Although the benefits of the EOS system are promising with regard to radiation dose reduction, few studies have investigated its use in SpA and little evidence has supported its reliability in assessing the structural damage caused by the disease.

Inclusion Criteria:

• Patients with Spondyloarthritis (SpA) meeting the criteria of Amor and / or Assessement of spondyloarthritis International Society (ASAS)
• Indication of standard radiography for the follow-up of the patients.

Exclusion Criteria:

• the presence of a contraindication to the performance of conventional radiography (CR) or EOS imaging
• any disease affecting cognition
• Patients who have had surgery on the spine and / or hip.

General data demographics , disease characteristics [symptom duration, disease presentation (axial/peripheral), SpA features (psoriasis, uveitis, Human Leukocyte Antigen(HLA) B27 positivity)], disease activity: Bath ankylosing spondylitis disease activity index ( BASDAI) and C-reactive protein (CRP) and disease severity:Bath Ankylosing Spondylitis Functional Index (BASFI) data were collected.

CR technique: All patients underwent a posteroanterior pelvic CR and a lateral and anteroposterior CR of the full spine.

EOS technique: all patients undewent a full spine and pelvis 2D EOS imaging.