A cannula is a hollow medical instrument used to introduce or withdraw fluids or materials. Cannulas come in different sizes and designs. Sharp injection needles should be distinguished from blunt cannulas.
For filler treatments, the choice depends on factors including the area, product and technique. A blunt cannula is usually introduced through an entry point made beforehand. It can still injure blood vessels or other structures.
The instrument alone does not make a treatment safe. Anatomical knowledge, appropriate technique, hygiene and the ability to recognise and manage complications are crucial.