Final answer:
Drainage after a radical mastectomy is typically achieved by closed-suction drain placement to prevent fluid accumulation and promote proper healing of the incision.
Step-by-step explanation:
Drainage of an incision following a simple or modified radical mastectomy is commonly accomplished by closed-suction drain placement. This method uses a surgically placed drain to remove fluids that accumulate in the space where the breast tissue used to be, by creating a vacuum that pulls the fluid out into a collection device. This is a critical part of the post-operative care to prevent fluid accumulation (seroma) and to help the incision heal properly. Other methods such as sterile dressings, manual compression, and gravity drainage are not as effective for this purpose.