AB1525 THE PRESENCE OF POWER DOPPLER SIGNALS IN THE DELTOID LIGAMENT, ESPECIALLY WITH A BROAD AND DEEP DISTRIBUTION, MAY PROVIDE DIAGNOSTIC CLUES FOR SPONDYLOARTHRITIS, PARTICULARLY UNDIFFERENTIATED SPONDYLOARTHRITIS

Abstract

BackgroundPower Doppler (PD) signals are occasionally detected in the deltoid ligament on musculoskeletal ultrasound (MSUS) examination of symptomatic ankles in nontraumatic inflammatory rheumatic diseases. However, it is often neglected due to its unclear clinical significance.ObjectivesTo evaluate the significance of PD signals in the deltoid ligament detected by MSUS in inflammatory rheumatic diseases.MethodsWe reviewed the record of MSUS examined in Japanese Red Cross Medical Center between April 2015 and October 2022. We examined the characteristics of medical record information and images of cases in which power Doppler signals were observed in the deltoid ligament. Patients with only a few punctate signals or less were excluded. Patients with only traumatic or degenerative disorders were also excluded.ResultsPD signals more than a few punctate signals were observed in the deltoid ligament in 31 cases. The disease categories and diagnoses of the patients were as follows: 13 spondyloarthritis (SpA) patients (9 undifferentiated SpA (USpA), 2 psoriatic arthritis, 2 reactive arthritis), 10 rheumatoid arthritis (RA) patients (6 early RA, 4 established RA), 7 crystal-induced arthritis (CIA) (6 gout, 1 CPPD), and 1 primary Sjögren’s syndrome. All SpA patients met the ASAS criteria for peripheral SpA and all RA patients fulfilled the 2010 ACR/EULAR classification criteria.In SpA cases, PD signals tended to distribute widely to the deep layer of the ligament (broad distribution, 10 out of 13 cases), while they tended to be predominant on the outer surface of the ligament in RA cases (superficial distribution, 7 out of 10 cases). There was a significant difference in the PD signal distribution pattern between SpA and RA by Fisher’s exact test (p=0.0397). In all CIA patients, hyperechoic materials were detected in the ligament.ConclusionAccording to literature reports, SpA is considered relatively rare in Japan, where the HLA-B27 positivity rate is < 0.3%, with an estimated population prevalence of < 0.01%[1]. The estimated prevalence of patients with RA in Japan is 0.65%[2], similar to the rest of the world. Considering the prevalence of each disease, we speculate that PD signals in the deltoid ligament are more characteristic of SpA. The presence of PD signals in the deltoid ligament, especially with a broad and deep distribution, may provide diagnostic clues for SpA, particularly USpA.