Background: Enthesitis is a remarkable feature of Ankylosing Spondylitis (AS) not specifically approached by the available measuring tools for the disease. Ultrasonography (US) has proved an excellent technique for the assessment of tendon pathology.
Objective: To test a sonographic entheseal index (SEI) of the lower limbs in a cohort of AS patients, as a potential measuring tool.
Methods: 44 AS patients and 10 healthy controls were enrolled. Functional and activity indexes BASFI and BASDAI, pain at entheseal points, severity of symptoms, acute phase reactants, Schober's test and stage of sacroilitis were registered. Patients underwent US examination of 5 entheseal regions from both lower limbs by 2 experts. Hypoechogenicity, increased tendon thickness, peritendinous oedema and bursitis were considered signs of active inflammation. Insertional bone erosions, intratendinous calcifications, decreased thickness and tears were considered signs of chronic injury. Each alteration independently scored 1 point. Data were analysed with Spearman's correlation method.
Results: There was a significant inter-observer correlation in SEI scores (p<0.001) and a fine discriminative power between controls and patients. Acute entheseal lesions predominated (63% vs 37%), the most frequent alteration being tendon hypoechogenicity (43%). 72% of all lesions were located at the foot. The SEI correlated with reduction of Schober's test (p<0.02), but not with other activity or severity parameters.
Conclusions: A scoring method like the SEI here described may be of help to characterise entheseal injury in AS, and for decision making in these patients.
- ankylosing spondylitis
- measuring tools