Deformation of Needle Tips during Facial Soft Tissue Filler Injections: An Electron-Microscopic Study.

BACKGROUND Injectable soft tissue fillers are used on a global scale for a variety of aesthetic indications. Despite their widespread use, there is a dearth of information regarding the potential repeated injections into tissue have to cause needle deformation. Repeated injections with the same needle result in an increase in force used by the injector to achieve dermal penetration, potentially resulting in decreased precision and increased patient discomfort. OBJECTIVES The objective of this study is to quantify the magnitude of needle tip deformation utilizing Scanning Electron Microscopy (SEM) image analysis. METHODS An observational study was performed evaluating four differently sized needles following soft tissue filler injections for five different aesthetic indications (zygomatic arch, infraorbital, mid cheek, nasolabial sulcus and perioral) in patients aged 36-64 years old. Following treatment, each needle was visualized and imaged through SEM, and the percentage of deformation in relation to the total amount of needle tip surface was calculated. RESULTS The most influencing factor for needle tip damage was revealed to be the number of injection passes, ie, dermal transitions. Per injection procedure, an increase in needle tip damage of 4.7% occurred. Touching the bone deformed the needle tip by 9.6% and the increase in needle size allowed for 0.13% more damage. CONCLUSIONS To the authors' knowledge, this is the first SEM investigation to provide objective evidence for the deformation of needle tips after repeated facial soft tissue filler injections. This data may help improve patient safety and comfort during these minimally invasive procedures.