Ultrasound Features of the Posterior Tibialis Tendon and Peroneus Brevis Tendon Entheses: Comparison Study Between Healthy Adults and Those With Inflammatory Arthritis.

OBJECTIVE Limited literature exists on the sonographic appearance of the posterior tibialis tendon (PTT) and the peroneus brevis tendon (PBT) entheses. We determined the anatomic features and best imaging techniques of normal PTT and PBT using musculoskeletal ultrasound and compared these findings to subjects with inflammatory arthritis. METHODS Adult subjects were enrolled as healthy controls (HCs), rheumatoid arthritis (RA) patients, or spondyloarthropathy (SpA) patients. Bilateral PTT and PBT entheses were imaged longitudinally, comparing 2 angles of insonation: perpendicular to the skin surface and 45° cephalad. Images were scored on semiquantitative scales assessing pathology. RESULTS A total of 78 subjects were enrolled (37 HC, 21 RA, and 20 SpA). Complete enthesis visualization was achieved more frequently in the perpendicular than in the cephalad view for the PBT (76.3% versus 58.7%), but more frequently in the cephalad view for the PTT (58.0% versus 19.6%). RA and SpA subjects had higher rates of PTT fiber disruption (P < 0.001), PTT tenosynovial effusion (P < 0.001), and Doppler signal (P < 0.001) than HCs. No significant differences existed at the PBT enthesis. In multivariate analysis, RA and SpA subjects were found to be 5.1 times (P < 0.001) and 3.6 times (P < 0.001) more likely to exhibit ultrasound-detected pathology, respectively, than HCs. CONCLUSION The perpendicular transducer aim is optimal for imaging the PBT, while the cephalad transducer orientation was more effective for evaluation of the PTT. Unlike distal PBT imaging, PTT imaging distinguished healthy and disease states, with both RA and SpA patients showing features of PTT enthesopathy. Distal PTT imaging is a useful technique for musculoskeletal ultrasound.