What are the steps involved in the double injection technique for botulinum toxin treatment of the chin?

The double injection technique involves injecting botulinum toxin at two points lateral to the midline of the chin. Each injection site receives 2.5 units of botulinum toxin, and the needle is inserted just superior to the mandibular margin within the safety zone. The needle is angled toward the lip, and the injection is made as the needle is withdrawn.

For the double injection technique, the patient is positioned at a 60-degree reclined angle, and the chin safety zone is identified. The mentalis muscle is located by instructing the patient to contract it. Two injection points are selected lateral to the midline, just superior to the mandibular margin within the safety zone. Each site receives 2.5 units of botulinum toxin. The needle is inserted and angled toward the lip, ensuring the tip ends at the chin protuberance, at least 2 cm below the vermillion border. The injection is administered as the needle is slowly withdrawn, using gentle and even plunger pressure. The same procedure is repeated for the opposite side of the chin, ensuring symmetry.