AB1359 DO LATERAL AND AP RADIOGRAPHS TELL DIFFERENT STORY IN PATIENTS WITH PSORIATIC ARTHRITIS?

Abstract

BackgroundThe conventional radiography score that is frequently used in spondyloarthritis patients is mSSASS. This score was developed for Anylosing Spondylitis patients and is also frequently used in Psoriatic arthritis (PsA) (1). The mSSASS score takes into account lateral imaging of the lumbar and cervical radiographs. On the other hand, syndesmophytes can be detected on lumbar anterior-posterior (AP) radiographs, which may not be seen on lateral assessment.ObjectivesThe aim of this study is to determine whether lumbar AP radiographs have an additional contribution to the evaluation of syndesmophytes in PsA patients.MethodsLumbar lateral radiographs and AP radiographs of 274 PsA patients receiving bDMARD therapy were evaluated. A total of 182 lateral lumbar radiographs and 144 AP radiographs were evaluated. On lateral lumbar radiographs each lumbar vertebral unit was evaluated between T12 lower and S1 upper ends. Areas between L1-L5 as AP, right-left, upper and lower vertebral units were evaluated. Syndesmophytes are classified as follows; corner and/or non-marginal syndesmophytes and bridging syndesmophytes. All of the assessments were done by an experienced rheumatologis (UK) and in cases with suspicion, another experienced rheumatologist reviewed the cases (LK) and a consensus was reached.Results182 patients had lumbar radiographs with the mean (SD) age of 44.9 (12.7) years and the mean (SD) PsA duration of 4. 8(6.1) years at the time of the radiographs were taken. The rate of females was 70.3%. When the lateral lumbar radiographs were evaluated, 42/182 (23.1%) patients had at least one syndesmophyte. These 42 patients had a total of 80 syndesmophytes, 41 of which were bridging and 39 were corner syndesmophytes. The distribution of syndesmophytes is shown in the Table 1. The mean number of syndesmophytes in patients with at least one syndesmophyte on the lumbar lateral radiograph is 80/42 (1.9). In patients with at least one syndesmophyte, 14/42 (33.3%) patients had additional syndesmophytes not seen on lateral radiographs but on AP X-ray. Their distribution is as follows: L1 (4 patients), L2 (3 patients), L3 (2 patients), L4 (6 patients) and L5 (1 patient). In addition, 11 corner syndesmophytes and 5 bridging syndesmophytes were detected in the lumbar AP radiograph. When lumbar and AP radiographs are evaluated together, 44/182 (24.2%) patients have at least one syndesmophyte. When the lumbar lateral and AP radiographs are evaluated together, there are 96 syndesmophytes in 44 patients with syndesmophytes, 46 of which are bridging and 50 are corner syndesmophytes. Average number of syndesmophytes were 96 in 44 patients (2.2 per-patient).Table 1.The distribution of syndesmophytes on lateral lumbar radiographsLateral Lumbar X-rayPatients with syndesmophytesTotal syndesmophyte count n(%)Number of bridging syndesmophyteNumber of corner syndesmophyteN (%)n(%)n(%)L1 lower-L2 upper border14291613L2 lower-L3 upper border1421129L3 lower-L4 upper border15211011L4 lower-L5 upper border4624L5 lower-S1 upper border2312ConclusionAP radiographs are not taken into account in conventional radiograph scores accepted as mSSASS. PsA patients have syndesmophytes in approximately one-quarter of patients on lateral radiograph, with an average syndesmophyte number of about 2. On the other hand, when AP radiographs are evaluated, new syndesmophytes that are not seen on lateral radiographs are seen in one-third of patients with at least one syndesmophyte. Although it does not cause a significant change in the number of patients with syndesmophytes, it should be kept in mind that the use of AP radiographs in PsA patients may cause an increase in the total score. Whether there is a difference between PsA and SpA patients should be investigated in further studies.