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.
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).
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.