Objective. To determine whether lidocaine test injections would increase the success rate of corticosteroid injection for treatment of impingement syndrome.
Methods. Two hundred thirty-nine patients diagnosed with impingement syndrome were allocated to the lidocaine test (LC) group (N = 139) and the subacromial (SA) group (N = 100). The LC group received 1 ml of 1% lidocaine injection into the subacromial bursa under ultrasound guidance and a second injection of the steroid solution into the subacromial bursa or glenohumeral joint according to the response. The SA group received the same amount of steroid injection into the subacromial bursa without a prior lidocaine injection. Categorical outcomes were utilized and subjects were grouped based on percentage pain relief. Clinical improvement was expressed in terms of the patient’s global impression of change (PGIC) as ‘not improved,’ ‘slightly improved,’ and ‘much improved.
Results. In the LC group, 76 of the 139 patients (54% [95 CI 46-63%]) showed ‘50-80% improvement’ and 15 (11% [95% CI 6.6-17%]) patients showed ‘more than 80% improvement’ at 3 weeks after the injection. While in the SA group, 29 of the 100 patient (29% [95% CI 21-39%]) showed ‘50-80% improvement’ and 13 (13% [95% CI 7.7-21%]) showed ‘more than 80% 3 weeks after the injection (χ2 = 15.073, P = 0.001). This difference persisted at 3 months (χ2 = 8.015, P = 0.018). The chi-square test of PGIC at 3 weeks also showed significant differences (P < 0.001).
Conclusions. This was the first study to show that a lidocaine pre-injection increases the success rate of steroid injection in patients suspected of having impingement syndrome.