[An anatomy study of temporal layers : the safe space for hyaluronic acid injection].

Objective: To determine the safe space for hyaluronic acid(HA) injection through anatomy study of temporal layers.
Methods: 6 fresh and 8 formaldehyde-fixed cadaver heads were dissected. The skin soft-tissue layers of temporal region were incised through the cranial coronal plane and elevated layer by layer. The morphological features of layers were observed and documented, as well as the relationship of the superficial temporal artery (STA),the temporal branch of facial nerve (TFN) and the middle temporal vein(MTV) with corresponding layers. Relevant neasurements of the superficial temporal fat pad (sTFD) were recorded. With reference of cardever dissection, temporal region injection with HA was carried out clinically to confirm the safety and effect.
Results: In the temporal region, from surface to the temporal fossa, the layers are skin, subcutaneous tissue, superfiacial temporal fascia (STF),loose areolar tissue, superficial layer of deep temporal fascia(sDTF), sTFD, deep layer of deep temporal fascia (dDTF),deep temporal fat pad (dTFD) and temporalis. The temporal skin is tightly attached with the subcutaneous tissue. The STA runs within the subcutaneous tissue on the STF, whereas the TFN within the areolar tissue was just beneath the STF. The loose areolar tissue is a potential layer space. The DTF splits into two sheets of fascia at the line 1 cm above the upper orbital rim to envelope the sTFD, within which the MTV runs backward. The dTFD is the temporal extension of buccal fat pad. With reference of cadever dissection, the target space of temporal HA injection was beneath the temporalis for the area superior to the MTV, whereas within the sTFD for the area inferior to the MTV.67 cases were completed with good result and no complication.
Conclusions: In the upper area of temporal region adjacent to the frontal border, the sub-temporalis space is the safety space for HA injection, while inferior to the middle temporal vein and near the zygoma, the superficial temporal fat pad is the target space for safe HA injection.