Consider the skin’s thickness in different areas of the body, as well as needle trajectory.
The thickness of the facial dermis varies between 0.4mm in lids and 1.2mm in forehead and cheeks. The outer diameter of 26-G needle can be used as a rough gauge to guide the depth of injection as it measures 0.45mm, which is half the thickness of the dermis, or conversely the facial dermis is only about twice as thick as 26-G needle.
So, for a proper intradermal injection, the needle should be inserted at approximately 10° angle and one-needle diameter deeper. For injection into mid-dermis to treat moderate-to-deep folds, the needle should be inserted at an angle of 30°– 40°, and for injection into deep dermis or supraperiosteal region to treat deeper folds, the needle should be directed at an angle of 45°– 90°.
The tip of the needle (usually 30 gauge) is barely injected into the skin at approximately a 30- degree angle as superficially as possible and tiny droplets (0.005-0.01) are placed as small wheal-like appearances. Localised blanching is acceptable because the droplets are so small.
This technique is indicated for superficial wrinkles and lines such as those along the cheeks ladder to oral commissures or in the glabella area. Only less viscous hyaluronic acid fillers should be injected using this technique. The needle should be changed once or twice during the treatment to ensure it remains as sharp as possible number.
To place filler along a fold or groove the needle is inserted to the desired depth advanced and withdrawn slowly as product is expressed into the cavity created by the needle in front of it This technique is also used to define the Vermilion border or enhance the body of the lips although it is difficult to be sure of the precise depth of the needle in the skin steady resistance is felt when the needle is advanced through the dermis whereas the sub dermal plane offers little resistance to the needle. To reduce the likelihood of intravascular injection in the periorbital area syringe should be aspirated gently before injection followed by slow retrograde movement of the syringe.
The needle is inserted, often to the hilt, and filler is injected during withdrawal in a linear retrograde threading, however before the needle tip exits the skin it is redirected so that further product is placed next to the first thread. This manoeuvre is repeated through the same needle puncture until a fan, or a triangular place shipped layer filler is laid out.
This is a grid like pattern that a filler is placed through multiple injection points so that the final series of threads is parallel to one another. The second series of threads placed perpendicular to the first set this provides structural support to the area it is particularly appropriate for firm fillers.
A Bolus of filler is injected deeply to provide volume and projection. This can be delivered with a needle or cannula. The needle will be introduced at a perpendicular angle to the skin and deposited periosteal.
This technique has been described for filling the tear trough using a fine cannula, a small depot of filler is placed super periosteal in the orbital groove then the small pool of filler is pushed or massaged gently through using the thumb along the tear trough deformity medially. This technique avoids multiple punctures with a needle and could be applied to other facial areas.