MR findings predict short-term pain relief after intra-articular injection

(Radiology Review) A recent Swiss study published in the American Journal of Roentgenology determined that the success of pain relief after intra-articular injection of the acromioclavicular joint could be determined on MRI.

"The purpose of this study was to evaluate which MRI findings in the acromioclavicular joint are predictive of pain relief after intra-articular injection," wrote Dr. Klaus Strobel and colleagues from the Orthopedic University Hospital in Zurich. They found that pain relief was more significant in patients with capsular hypertrophy.

Fifty patients had MRI and intra-articular injections under fluoroscopic control. MR findings, including osteophytes, subchondral cysts and irregularities, bone marrow edema, joint effusion, and joint capsule hypertrophy (capsular thickness equal to or greater than 3 mm) were assessed.

"Patients graded pain relief on a visual analogue scale (0%-100%) after 15 minutes," the authors wrote. This subjective assessment of pain level by the patient was quantified by scoring 0% for no pain relief and 100% for complete pain relief. The treatment was considered successful when a pain relief score of 70% or more was achieved.

Two MRI scanners were used and the sequences varied depending on the system: a 1-tesla scanner or a 1.5-tesla scanner with a dedicated receive-only shoulder coiled was used. Patients were scanned with the shoulder in a neutral position and patients were given an intra-articular injection of gadopentetate unless contraindicated.

The results determined that "the sensitivity in diagnosing a successful injection was highest for caudal osteophytes (82%) and capsular hypertrophy (73%)."

Furthermore, "the specificity (range, 51-97%) was highest for subchondral cysts (97%), subchondral bone marrow edema (95%), and joint effusion (92%)," the authors reported.

"Pain relief after intra-articular injection is significantly related to capsular hypertrophy diagnosed on MRI. MRI findings have a reasonable sensitivity and a high specificity in predicting relevant short-term pain relief after intra-articular injection," they concluded. Because surgery often was performed shortly after the corticosteroid injection, long-term follow-up of pain relief was not possible.

MRI features of the acromioclavicular joint that predict pain relief from intra-articular injection
Strobel, K. et. al.
Department of radiology, Orthopedic University Hospital, Zurich.
AJR 2003 September; 181:755-760

By Radiology Review
October 20, 2003

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