A randomized clinical study of the heated lidocaine/tetracaine patch versus subacromial corticosteroid injection for the treatment of pain associated with shoulder impingement syndrome

BACKGROUND: Treatment for pain due to shoulder impingement syndrome (SIS) typically begins conservatively with nonsteroidal anti-inflammatory drugs and physical therapy and can include subacromial injection of corticosteroids, particularly in patients unresponsive to conservative measures. The heated lidocaine/tetracaine (HLT) patch has been reported to reduce SIS pain in a small case series. METHODS: This was a prospective, randomized, open-label clinical trial in which adult patients with SIS pain lasting at least 14 days, with an average intensity of ≥4 on a 0–10 scale (0= no pain, 10= worst pain) were randomized to treatment with the HLT patch or a single subacromial injection of triamcinolone acetonide (10 mg). Patients in the HLT patch group applied a single HLT patch to the shoulder for 4 hours twice daily, with a 12-hour interval between treatments during the first 14 days, and could continue to use the patch on an as-needed basis (up to twice daily) during the second 14-day period. No treatment was allowed in the final 14-day period. At baseline and at days 14, 28, and 42, patients rated their pain and pain interference with specific activities (0–10 scale). RESULTS: Sixty patients enrolled in the study (average age =51 years, range 18–75, n=21 female). Average pain scores declined from 6.0±1.6 at baseline to 3.5±2.4 at day 42 in the HLT patch group (n=29, P<0.001) and from 5.6±1.2 to 3.2±2.6 in the injection group (n=31, P<0.001). Similar improvements were seen in each group for worst pain; pain interference with general activity, work, or sleep; and range of motion. No significant between-group differences were seen for any pain or pain interference scores at any time point. CONCLUSION: These results suggest that short-term, noninvasive treatment with the HLT patch has similar efficacy to subacromial corticosteroid injections for the treatment of pain associated with SIS.