When to change needles during neuromodulator injections-An electron-microscopy investigation into needle tip deformation.

Abstract

Neuromodulator injections are minimally invasive procedures performed across the globe. Despite their ubiquity, there is a dearth of information on whether and how needle tips used for neuromodulator procedures are deformed after repeated injections. We investigated the magnitude of needle tip deformation following sequential injection passes (3×, 5×, and 10×) during facial neuromodulator injections with three commonly used needle sizes (30G, 31G, and 32G). Neuromodulator was administered for four different aesthetic indications. Each collected needle was mounted and imaged in a Philips XL-30 Scanning electron microscope. Images were processed using ImageJ photo analysis software. Forty-five needle tips were investigated. When comparing the facial regions of interest, a statistically significant difference in deformation percentage was found when injecting 10× (p = 0.044) with greatest damage after injecting the glabella (38.4%), followed by lateral canthus (27.9%), forehead (27.5%), and midface (23.1%). Independent of facial region targeted, the mean percentage of needle deformation at 3× was 14.8%, at 5× 19.6%, and at 10× 29.2% with p < 0.001. Smaller needle size corresponded to smaller percentage of damage. Exchanging needles after more than five injection passes will minimize needle deformation and likely increase injection precision.