Neue Studien

Detection of sacroiliitis by ultrasound

Feasibility of Second-Generation Ultrasound Contrast Media
in the Detection of Active Sacroiliitis
Klauser AS et al. Arthritis & Rheum 61; 7:909-916, 2009. DOI 10.1002/art.24648

Objective
To determine whether a recently available contrast enhanced ultra-sound technique allows for the detection of active sacroiliitis.

Methods
Examination of 42 consecutive patients (84 SI joints) presenting with a clinical diagnosis of sacroiliitis in 50 SI joints and 21 controls (42 SI joints) were investigated by ultrasound. The ultra-sound technique used second-generation ultrasound contrast media. This method uses a low mechanical index ultrasound technique and is based on non-linear acoustic effects and the interaction with micro-bubbles that makes micro-bubbles more stable and durable, thereby offering the possibility of performing continuous scanning over a specific period of time (this allows for a prolonged US-examination).

Results
This new US-method detected enhancement in all clinically active SI joints, showing an enhancement depth into the dorsal SI joint cleft of 18.5 mm, which was significantly higher compared with both inac-tive joints of patients (3.6 mm) and healthy controls (3.1 mm). All inactive joints were correctly classified based on a lack of deep enhancement in patients with sacroiliitis and controls (both sensi-tivity and specificity at 100%).

Conclusion
This new second-generation ultrasound contrast media allows the dif-ferentiation of active sacroiliitis from inactive SI joints. It proved to be a feasible method for the detection of vascularity in clinically active sacroiliitis.

Comment
MRI is able to differentiate between active and inactive SI joints. However, this method is time consuming and costly. This recently available second-generation ultrasound technique described in this study allows for the detection of SI joint inflammation. Although this is a preliminary study, the results are extraordinary in that both sensitivity and specificity reach a top value of 100%. Cer-tainly, it will be worthwhile to examine this technique in a differ-ent patient setting including several investigators. If this tech-nique proves to be sensitive and specific as described this study, it will add very much to the current utility of ultrasound. As ultrasound is already known to allow for the localisation of precise injections into the SI joint, this will be a welcome addition making ultrasound techniques even more valuable.

Beat A. Michel

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