In practice, most joint injections are delivered using clinical examination to guide the injection, but a number of studies have demonstrated inaccuracy rates of up to 63%, which "may contribute to the lack of clinical benefit observed in some patients," senior author Dr. David Kane, from Adelaide and Meath Hospital, Dublin, Ireland, and his co-authors note.
Ultrasound, however, "allows direct visualization of the injection needle within the joint structures in real-time ... and has been shown in small series to improve accuracy of needle placement and joint aspiration compared to clinical examination guidance," they wrote.
Their goal in the present study was to confirm, on a larger scale, that ultrasound guidance does in fact improve the accuracy of needle placement and to see if clinical outcomes are also enhanced.
The randomized study included 184 patients with inflammatory arthritis in the shoulder, elbow, wrist, knee, or ankle. Each patient received a 40-mg injection of triamcinolone into the affected joint, guided either by ultrasonography or clinical exam.
Along with the steroid, the researchers injected x-ray contrast material to allow them to assess accuracy. Pain, function, and stiffness at the targeted joint were evaluated before and two and six weeks after injection using visual analogue scales. Subjects also completed the Health Assessment Questionnaire and the EuroQol questionnaire. Erythrocyte sedimentation rates and C-reactive protein levels were measured at baseline and at two weeks.
Accuracy rates were 83% with ultrasound guidance and 66% when injections were guided by clinical examination (p = 0.01).
Although there were some significant EuroQol differences between the groups, the vast majority of clinical outcomes were comparable in each, according to the report.
The authors did find that when an injection was accurate, joint function at six weeks was enhanced. With an accurate injection, a 31-mm improvement on the visual analogue scale for function was seen compared with a 21-mm improvement with inaccurate injections (p = 0.03).
The results also found that clinicians using ultrasound guidance were better able to determine when an injection was accurate than clinicians without access to ultrasound.
Regarding study limitations, the authors note that "firstly there was a less than expected difference between accuracy rates for ultrasound and clinical exam guided injections." And "secondly, clinical parameters of inflammation were used as criteria for study enrollment but these are less accurate than imaging and may have resulted in the inclusion of patients whose joint was not significantly inflamed." Finally, the steroid dose was fairly high and may have caused systemic effects that could mask between-group differences.
By Anthony J. Brown, M.D.
Arthritis Rheum 2010.
Last Updated: 2010-03-19 9:42:00 -0400 (Reuters Health)
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