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Soft-tissue fillers (Table 254-1) are either injected through a sharp needle or through a blunt cannula. The level of injection into the skin and the chosen length of the needle depend on the type of filler injected, the properties of the filler, the area injected, and the desired result. Threading is a technique in which the needle is inserted into the skin and the filler is deposited in a linear fashion along the track of the needle as it is being withdrawn. Fanning is a type of threading in which, instead of inserting the needle into a new area each time, the needle is just withdrawn so that a new track can be made radially adjacent to the last. In the “push-ahead” technique, an injection is made in an antegrade direction, so that the injectable material flows from the tip of the needle and hydrodissects the tissues as it flows. This technique is often used in areas in which bruising is more likely to occur along the needle track, such as the upper lid and brow. In the depot method of injection, small “pearls” of material are deposited serially, usually along a fold or deep by bone. Cross-hatching is an approach used to diffusely cover an area with the injected material. In this method, linear threads are lined up in succession and a second series of rows is then layered at right angles on top of the first. Figure 254-1 illustrates the different injection techniques. In addition to the methods just described, highly viscous fillers emerging on the US market will most likely be injected in a deep subcutaneous bolus through a blunt cannula or large bore needle. Whatever the technique chosen, care should be taken in highly vascular areas to avoid intravascular injection of filling material. The plunger of the syringe should be pulled back to check for blood flow, and if it is found, the needle should be withdrawn and repositioned.
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