MR arthrography of the shoulder using an anterior approach: optimal injection site.

Objective: The purpose of our study was to optimize anterior MR arthrography of the shoulder by comparing three injection sites.

Materials And Methods: Seventy-eight patients were divided into three groups of 26 each, according to the injection site selected: the upper third of the medial part of the humeral head, the lower third of the medial part of the humeral head, or the area between the middle and lower thirds of the glenohumeral joint. A marker plate with radiopaque coordinates was used in performing the technique. Radiologist time and exposure time were recorded, and the intensity of the patient's pain was measured using a Visual Analogue Scale (VAS). Groups were compared using variance analysis and the least significant difference method.

Results: Shoulder arthrography was considered satisfactory for all three injection sites. Mean exposure time was 20.9 +/- 7.8 (SD) milliseconds, and mean radiologist time was 6.4 +/- 0.8 minutes. Mean pain intensity registered by the VAS was 1.7 +/- 0.9, the lowest values tending to be those recorded by patients who received an injection in the upper third. Exposure and radiologist times were lower for these latter patients; differences between the upper third and the other two areas were statistically significant (p < 0.005).

Conclusion: The optimal injection site for anterior MR arthrography of the shoulder is the upper third of the humeral head, a simple, rapid procedure that is well tolerated by patients and reduces the radiation dose administered.