Final answer:
The commonly used surgery for a #12 blade on a #7 handle is plastic surgery due to the need for precise and intricate incisions.
Step-by-step explanation:
The question asks about the common surgical use of a #12 knife blade on a #7 handle. A #12 blade is a small, pointed, crescent-shaped blade that is typically used for making short and precise incisions. It is most commonly associated with plastic surgery procedures. This type of blade is ideal for intricate work that is characteristic of plastic surgery where precision is paramount. The sharpness of a knife is crucial for clean cuts, which is why surgeons choose specific blades like the #12 for different surgeries.
Cardiovascular, orthopedic or neurosurgery might use different types of blades depending on the procedure. However, for intricate and precise work such as in plastic surgery, a #12 blade on a #7 handle is the preferred choice.