AB0872 B-Flow Imaging of Synovial Tissue in Osteoarthritis

Background The development of disease modifying medication for osteoarthritis (OA) is desirable, but the target tissue of such treatment remains unclear. We have previously shown that proliferative and hyperemic synovial tissue is rare in joints affected by erosive osteoarthritis (EOA), if power Doppler ultrasound (US) is used as the detecting instrument. (1) Doppler ultrasound gives indirect information about blood flow by assessing amplitude or velocity of a frequency shift. In contrast, B-flow ultrasound directly visualizes blood flow, and can visualize synovial hyperemia in a precise (flow only in the vascular lumen) and sensitive (small vessels) fashion. No previous studies have used B-flow ultrasound to assess synovial hyperemia. Objectives To assess synovial proliferation and synovial hyperemia in proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints of patients with a radiologic diagnosis of OA or EOA using high-frequency B-mode gray scale US (GSUS) and B-flow US. Methods Joints affected by OA or EOA based on bilateral hand radiographs in 3 planes were then examined sonographically. For enrollment, the assessment of the MSK radiologist was counted. Gray scale US, native B-flow US and color B-flow still images and 3-second video clips were obtained by a rheumatologist with 20 years of experience in MSK US, certified in rheumatologic US (RT). All US and B-flow scans were performed on a GE Logiq E9 built 2014 machine, with an 18 MHz small footprint probe using a B-flow software package. Vascular factory settings were optimized for low flow in fingers. Distension of the hyperechoic, fibrous joint capsule was scored for GS synovitis from 0-3 (absent, mild, moderate, severe), analogous to scoring for RA. Intra-articular synovial blood flow was scored from 0-3 (no flow, individual signals, involving less, and equal to/more than half the area of detected synovitis). Total scores for EOA patients were compared with OA patients. Results 559 still images and video clips were obtained. 84 joints of 20 consecutive OA and EOA patients were examined: DIP n=55; IP/PIP n=29. EOA patients, n=11 (55%); OA, n=9, (45%) as determined prior to US by the reading radiologist. Age range was 51-88 years; mean age 68. Female, n=16; male, n=4. Resulting scores: Gray scale (score=n) 0=45; 1=31; 2=4; 3=2. B-flow (score=n) 0=81; 1=4; 2=1; 3=0. Mean GS score EOA=56.6; OA=53. Scores for intra-articular B-flow were too low to compare. Conclusions B-flow US was well suited to detect blood flow in small digital vessels. While physiologic flow in soft tissues adjacent to joints was seen in all images and video clips, intra-articular, synovial blood flow was rarely observed in OA or EOA patients. Synovial proliferation, if present, was mild and appeared to be due to mechanical distension of the joint capsule by osteophytes. No significant difference in mean GS synovitis score was observed between OA and EOA patients. References Thiele RG, Anandarajah AP. Erosive Osteoarthritis is Not Associated With Invading Synovial Tissue: An Ultrasound Study. Arthritis Rheum 2010 Oct;62(10):S674 Disclosure of Interest None declared