There is some, although fairly weak evidence that ultrasound may be able to demonstrate reductions in synovial thickness (ST), effusion, and power Doppler signal a week after the administration of intra-articular corticosteroid (IACS) therapy, an exploratory study suggests.
Further evaluation may eventually identify a role for ultrasound as a responsive imaging outcome tool of potential use in clinical trials, the investigators indicated in their report, appearing in Rheumatology.
Action Points
- Note that this small cohort study of patients with knee OA demonstrated that ultrasound measurement of the power Doppler score may have diagnostic and prognostic significance.
- Be aware that the study was very small, and findings should be considered exploratory.
In a total of 33 patients with osteoarthritis (OA) of the knee, 19 of whom received IACS and 14 of whom did not, ST decreased in 16 out of 19 IACS patients along with two others who did not receive IACS, at a mean between-group difference of 4.7 mm (95% CI 1.1-8.2, P<0.012).
However, absolute reduction in ST was not associated with an absolute reduction in pain (P=0.289).
Decreased ST did show a trend toward reduced pain greater than or equal to the minimum clinically important improvement (MCII) in pain at 52.9% versus 23.1% (P=0.098). The MCII was defined as an improvement on the visual analog scale of ≥20 mm.
Absolute changes in pain and power Doppler score were only weakly associated (P=0.049) while a decreased power Doppler score was associated with a reduction in pain greater than or equal to the MCII (64.3% versus 18.8%, P= 0.011).
"Imaging techniques such as ultrasound are well placed to be used as objective outcome tools in knee arthritis," at the University of Western Australia in Perth, and colleagues wrote.
"[But] until appropriate and responsive imaging outcome tools are developed, the ability to rigorously examine the mode of action and efficacy of therapies in vivo is limited," the researchers stated.
"[Still], an ultrasound model of short-term synovial response has great potential, and, in particular, the validity and utility of power Doppler in assessing synovitis in knee."
Subjects completed a symptom assessment and ultrasound examination at baseline and returned for follow-up at 1 and 4 weeks later.
Those whom the treating physician felt needed treatment received 80 mg of IACS (methylprednisolone)) mixed with 2 mL lidocaine 1% at the baseline visit.
The remaining subjects had no therapeutic intervention between baseline and week four but were asked to maintain stable doses of analgesics over the observation period.
Subjects were also asked to mark on a 100 mm visual analog scale (VAS) how bad their knee pain had been during physical activities over the past 48 hours.
All 19 subjects in the IACS cohort and 14 out of 16 others attended the 1 week follow-up and all but one of the IACS cohort and all 14 others attended the follow-up at 4 weeks.
"There was some evidence that both ST and effusion were reduced at 1 week in the IACS group whereas no consistent reduction in either pathology was identified in the others," researchers point out.
The change in total power Doppler score indicated that the groups differed at 1 week (median change, others 0.0 (IQR -0.3 to 1.3) versus the IASC group at -1.0 (IQR -5.0 to 0.0), P=0.004) but at week four, there were no longer substantive differences between the groups in ST, effusion size, or power Doppler score.
Changes in pain at 1 week indicated that among patients not receiving IACS, none reported a clinically meaningful improvement in pain VAS at 1 week whereas in the IACS group, all but one patient reported at least some reduction in pain while almost two-thirds of IACS recipients reported clinically meaningful improvement in pain.
In evaluating the relationship between symptoms and synovial responses, some 79% of individuals who did not receive IACS showed an increase in ST at 1 week, but there was no clinically important change in pain in most patients.
No consistent pattern was seen in either an increase or a reduction in effusion after 1 week in those who did not receive IACS.
Again in the IACS group, the size of effusion was reduced in close to 74% of patients, but greater reductions in effusion were not observed in patients whose pain had improved during the week compared with those whose change in pain remained within measurement error.
In the injection group, total power Doppler score decreased in approximately 68% of the group while in those who did not receive IACS, the power Doppler score tended to remain stable or increase at 1 week.
The authors caution that this was an exploratory study only and was not powered, and the lack of statistical powering means that findings must be regarded with this in mind.
They also point out that their study was purely observational and followed patients who were treated according to their need so no randomized control group was available for comparison.
Imaging was done with the knee in 30 degrees of flexion; at this degree of flexion, quadriceps contract might have affected the Doppler signal, they add.
"The purpose of this study was to determine whether ultrasound is able to detect early changes in synovial pathology in response to anti-inflammatory therapy," investigators observed.
"Despite the limitations of the study, the findings from this study are of importance in both the developing and testing of IA therapies in OA."
"In particular, a well-designed, adequately powered trial randomizing patients to a potential anti-synovial therapy (most likely CS) or placebo would further aid development of an ultrasound outcome tool in OA," they conclude.
Disclosures
No specific funding was received from any funding bodies to support the study.
One of the authors has done consultancy and speaker work for General Electric. None of the other authors declared any conflicts of interest.
Primary Source
Rheumatology
Keen H, et al "Ultrasound assessment of response to intra-articular therapy in ostseoarthritis of the knee" Rheumatology 2015; DOI: 10.1093/rheumatology/keu529.