Microanatomical Location of Hyaluronic Acid Gel Following Injection of the Upper Lip Vermillion Border: Comparison of Needle and Microcannula Injection Technique.

Abstract

To compare needle and microcannula injection techniques in regards to the microanatomical location of hyaluronic acid (HA) gel injected in the upper lip vermillion border of cadaver specimens. The upper lip vermillion border was injected transcutaneously with HA gel in 8 fresh hemifaces of 4 female human cadavers. Each hemiface was injected by a single experienced injector, the right side using a 27-gauge microcannula and the left side using a 30-gauge needle. A 2-cm region of each lip was excised lateral to a point 1-cm lateral to the philtrum. Specimens were fixed in 95% alcohol, embedded in paraffin, and stained with hematoxylin-eosin for histologic examination. Most HA injected with either a needle or a microcannula was located within the orbicularis oris muscle, and the remaining HA resided within the subcutaneous fat. In 3/4 right (microcannula) hemifaces, 100% of the HA was located within the muscle. Only 2/4 left (needle) hemifaces had at least 95% of the HA located within the muscle. Overall, in right (microcannula) hemifaces, 93% of the filler was located within the muscle, and in left (needle) hemifaces, 79% of the filler was located within the muscle (p =0.14). Most HA filler injected into the vermillion border after either microcannula or needle injection resides within the orbicularis oris muscle rather than in a subcutaneous/submucosal location. Injection with a microcannula shows a trend for more uniform intramuscular location compared with needle injection.