A sonographic enthesitic index of lower limbs is a valuable tool in the assessment of ankylosing spondylitis.
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 to be 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 patients with AS, as a potential measuring tool.


METHODS
44 patients with AS and 10 healthy controls were enrolled. Bath Ankylosing Spondylitis Functional Index and Bath Ankylosing Spondylitis Disease Activity Index, pain at entheseal points, severity of symptoms, acute-phase reactants, Schober's test and stage of sacroiliitis were recorded. Patients underwent US examination of five entheseal regions from both lower limbs by two 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 one point. Data were analysed with Spearman's correlation method.


RESULTS
A significant interobserver correlation in SEI scores (p<0.001) and a fine discriminative power between controls and patients were observed. 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 such as the SEI may be of help in characterising entheseal injury in AS, and for decision making in these patients.
Alcalde
M
M
Department of Rheumatology, Fundación Jiménez Díaz, UAM, Avda, Reyes Católicos 2, 28040 Madrid, Spain.
Acebes
Juan C
JC
Cruz
M
M
González-Hombrado
L
L
Herrero-Beaumont
G
G
Sánchez-Pernaute
O
O
D000208:Acute Disease; D000328:Adult; D000368:Aged; D000843:Ankle Joint / Q000000981:diagnostic imaging; D002062:Bursitis / Q000000981:diagnostic imaging; D002114:Calcinosis / Q000000981:diagnostic imaging; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D012680:Sensitivity and Specificity; D013167:Spondylitis, Ankylosing / Q000000981:diagnostic imaging*; D013710:Tendons / Q000000981:diagnostic imaging*; D014463:Ultrasonography