Musculoskeletal ultrasonography of the Achilles tendon and plantar fascia in spondyloarthritis patients

Aim of the work: To assess the frequency and severity of peripheral enthesitis in spondyloarthritis (SpA) patients using musculoskeletal ultrasound (MSKUS) in B mode associated with power Doppler (PD) compared to a group of patients with mechanical low back pain (M-LBP). Patients and methods: The study included 40 SpA patients and 20 M-LBP patients as a control group. Ultrasound (US) in B mode and PD was performed at Achilles tendon (AT) and plantar fascia (PF). Results: The mean age of SpA patients was 41.9 ± 14.3 years and disease duration 8.4 ± 5.8 years. Axial form was found in 36 cases (90%) and peripheral form in 4 (10%). The mean ESR was 28.3 ± 23.2 mm/1sth and the CRP was 22.9 ± 31.2 mg/l. In SpA patients 109/160 (68.1%) of the assessed entheseal sites were significantly abnormal compared to 27/80 (33.8%) in M-LBP patients (AT p < .0001 and PF p = .02). Compared to the M-LBP patients, a significant difference was found in AT for hypoechogenicity (p = .006) and bone erosion (p = .005) and at both entheses for cortical hypervascularisation (AT: p < .0001 and PF: p = .03). Otherwise, in SpA patients, 60.2% (53/88) of non tender entheses showed at least one ultrasound abnormality compared to 77.8% (56/72) of tender entheses. A significant correlation was identified between clinical and ultrasound assessment (r = 0.4, p = .01). Conclusion: The frequency of enthesitis was high among SpA compared with M-LBP patients and AT was the most affected enthesis. Abnormal vascularization in the cortical bone insertion of entheses was detected especially in SpA patients, and there was great evidence of subclinical enthesitis. Keywords: Enthesis, Spondyloarthritis, Mechanical low back pain, Ultrasonography, Power dopple