Background/Purpose: Spondyloarthritides (SpA) are characterized by inflammatory and structural changes in the axial skeleton and in peripheral joints and entheses. Imaging has an essential role in the new classification criteria for axial SpA (axSpA) but not for peripheral manifestations (pSpA). This is largely due to limited knowledge about the value of imaging to detect peripheral arthritis and enthesitis in SpA and whether it differentiates SpA from other conditions (non-SpA). We evaluated the significance of imaging procedures and their influence on treatment decision in patients with peripheral involvement of the lower limbs in pSpA vs. non-SpA.

Methods: Consecutive patients with pSpA (n=30) and non-SpA (n=30), aged <45 years presenting with a painful heel or knee were examined by a rheumatologist, blinded for the patient´s diagnosis, who decided on the further treatment based on the actual clinical findings. Thereafter, several imaging procedures were performed: conventional radiographs, power-doppler ultrasound (PDUS) and magnetic resonance imaging (MRI) of the painful sites. In total 105 entheses, 71 heels and 34 knees were assessed and evaluated. Finally the treatment decisions were re-evaluated.

Results: The groups were similar in mean age (37.2±6.8 years), CRP (0.6±0.9mg/dl), NRS-pain (6.1±2.1) but symptom duration (SpA: 17.2±27.5 vs. non-SpA: 4.4±4.3 months) and HLA-B27 (67% in axSpA vs. 13% in non-SpA) differed (both n<0.005). At presentation <66% of patients were taking NSAIDs, <35% DMARDs and <20% biologics. A total of 71 heels and 34 knees were examined in both groups. There were no differences in the distribution of lesions between patients with pSpA and non-SpA. Pathologic findings were discovered most frequently using MRI of the heel (85.3% of patients), while x-rays were regarded pathologic in only 16.7% of patients (p<0.05). Bone erosions in the Achilles’ insertion as assessed by PDUS occurred more frequently in pSpA than in non-SpA: 48.6 vs. 23.5% (p=0.002) and the patellar tendon at the tibial tuberosity as assessed by MRI was thicker in pSpA: 38±8mm vs. 34±5mm in non-SpA (p=0.011), while inflammatory findings were seen in similar frequencies. Based on the clinical evaluation only, a change in treatment was suggested in 47% and 57% of patients with axSpA and non-SpA, respectively. Imaging (only US and MRI) contributed to 

Conclusion: In symptomatic patients with knee or heel involvement, heel erosions (assessed by PDUS) and patellar tendon thickness (assessed by MRI) helped to differentiate pSpA from non-SpA patients but active enthesitis did not. Imaging of inflammation but also of chronic changes at peripheral sites contributed in addition to the clinical findings to make treatment decisions in a limited number of patients with pSpA but not with non-SpA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/a-prospective-evaluation-of-the-diagnostic-value-of-conventional-radiography-ultrasound-and-mri-in-comparison-to-clinical-examination-for-the-assessment-of-heel-and-knee-enthesitis-in-patients-with-p/