The Effectiveness of a Non-Invasive Shot Blocking Device for Reducing Pain of In-office Injections in Hand Surgery

Abstract

Background: The gate control theory asserts that non-painful stimuli can block pain perception. The ShotBlocker™ device is a plastic disk with blunt projections that rests on the skin, and we hypothesize that it will reduce pain during hand injections. Methods: This is a prospective randomized trial of 117 patients undergoing injections for common hand conditions. Patients were randomized into 3 groups: device, placebo (device with projections removed), and control. Patients recorded on an analog pain scale the pain severity of the injection, as well as their most recent tetanus shot. A normalized pain score was obtained from the difference between the injection and tetanus shot pain scores. The mean non-normalized and normalized scores for each treatment group were compared to the control group using the Wilcoxon signed rank test. Results: There were 91 women and 26 men. Common diagnoses included trigger finger (n = 53), DeQuervain’s tendonitis (n = 33), and basal joint arthritis (n = 22). The groups did not differ significantly in age, gender, or diagnosis. Mean pain score in the device group was 5.2 out of 10, and it was 5.7 for the control group. The normalized pain score in the device group was significantly lower than the control group. Normalized and non-normalized pain scores for the placebo group were not significantly lower than the control group. Conclusions: The shot blocking device effectively reduced pain of injection versus controls when pain scores were normalized for pain tolerance. The modified device did not reduce the pain of injection, suggesting that gate control is the mechanism of action.

Investigating 3D-printed disk compressing against skin for pain relief in intradermal infiltration anesthesia: a randomized controlled trial

“…Current physical products for pain relief, such as ShotBlocker®, based on the gate control theory described by Melzack and Wall [ 19 ], have blunt projections to stimulate larger afferent nerve fibers when compressing around the injection site, thus inhibiting pain perception by exerting an inhibitory effect on afferent sensory fibers by activating cells within the substantia gelatinosa in the dorsal horn of the spinal cord. Applying ShotBlocker® for local anesthesia in general places has proven effective for pain relief [ 4 , 5 ]. A recent meta-analysis concluded that the application of ShotBlocker® can reduce IM injection pain in adults [ 20 ], although two additional randomized controlled trials in IM injection and spinal anesthesia reported contradicting results [ 13 , 21 ] These different study results may be affected by heterogeneity of the injection site, volume, and depth [ 22 ].…”

“…In this application, the IM injection site is compressed using a blunt-tipped plastic disk with many projections. Although this method may relieve injection pain intensity [ 2 – 5 ], several studies have contradicting conclusions. Most randomized controlled trials have focused on its application in deep site injection (i.e., IM, spinal, and joint anesthesia).…”