To explore the distinctive ultrasonographic characters of enthesitis in patients with spondyloarthritis (SpA) and evaluate the diagnostic value of ultrasonography in SpA by comparing ultrasonography of enthesis in the lower limbs of patients with SpA, rheumatoid arthritis (RA) and osteoarthritis (OA).
Entheses in the lower limbs (quadriceps tendon, proximal patellar ligament, distal patellar ligament, achilles tendon and plantar aponeurosis) were detected in SpA, RA, OA patients and health controls by ultrasonographic examination.
A total of 46 SpA, 23 RA and 12 OA patients were enrolled in this study, with 26 SpA and 7 RA patients complaining of heel pain (P<0.05). There were 126 enthesal sites (126/460, 27.2%) were detected abnormal in SpA group, compared with 54 of 230 (23.5%) sites in RA group and 27 of 120 (22.5%) sites in OA group (P>0.05). Sixty five (70.7%) sites of the distal patellar ligaments were abnormal in SpA group, while that were 19 (41.3%) in RA group (P<0.05) and 13 (54.2%) in OA group. Twenty six sites of tendon thickness and 22 sites of bone erosion in the distal patellar ligaments were found in SpA group, while only one site of each in RA group (P<0.05) and 4 sites of tendon thickness in OA group (P<0.05) were found.Tendon thickness, bursal synovitis and bone erosion coexisting in one distal patellar ligament indicated SpA, the sensitivity, specificity and the area under the curve (AUC) of which were 70.7%, 65.5% and 0.740, respectively.
Tendon thickness and bone erosion of entheses were more likely the distinctive ultrasonographic characters of enthesitis in SpA patients. Tendon thickness, bursal synovitis and bone erosion in the distal patellar ligament could be an ideal tool for SpA diagnosis.