Purpose
With age, the subcutaneous fat, temporalis muscle and temporal bones are thought to thin resulting in temporal hollowing. A restorative and more youthful appearance can be accomplished using hyaluronic acid (HA) filler rejuvenation. Hyaluronic acid fillers have been commonly used to address temporal fossa hollows by injecting either deep to the temporalis muscle or subcutaneously. However, there have been case reports of vascular injury when injecting within this area. This study aims to investigate the histologic location of HA gel following subcutaneous injection for temporal fossa hollows in cadaver specimens.
Methods
Bilateral temporal fossas of 3 fresh cadaver specimens (6 samples) were dissected following subcutaneous injection of HA, Belotero Balance (Merz Aesthetics, Inc., Greensboro, NC, USA). Each injection was delivered in a fan and cross-hatch pattern directly within a subcutaneous injection plane (Figure 1). Conservative post-injection molding to the smooth the contour was performed on each specimen similar to that used in a clinical setting. The soft tissue specimens were grossly dissected to the supraperiosteal plane. The specimens were fixed, stained with H&E and then histologically examined.
Results
Hyaluronic acid was directly visualized in all specimens as shown in Figure 2. The majority (95%) of HA was noted to be deposited in subcutaneous fat in all but one specimen. In one specimen HA was noted to be in close proximity to a muscular artery (Figure 2).
Conclusions
This study presents the first histoanatomical view of the position of HA following subcutaneous injection of the temporal fossa. Subcutaneous injection of filler in the temporal region may pose risk for inadvertent intravascular injection due to the proximity of the superficial temporal fascia and associated temporal vessels. Care should be taken to superficially inject filler when injecting subcutaneously for temporal hollows.