Which instrument is used for cutting bones in large dogs?

The instrument used for cutting bones in large dogs, specifically in orthopedic surgical procedures, is Gigli wire. This tool consists of a flexible wire saw that is particularly effective at cutting through bone. It is often employed in situations where precise cutting is necessary, such as during the amputation of a limb or the resection of bone.

The design of Gigli wire allows it to be manipulated around the bone, providing the veterinarian with the ability to control the depth and angle of the cut. During surgery, it is typically used in conjunction with handles or other instruments to apply tension and leverage for efficient cutting.

The other instruments listed serve different purposes. Cancellous screws are used for fastening bone fragments together, Steinmann pins are utilized for stabilizing fractures, and McPhail's needle holder is intended for gripping and manipulating surgical needles rather than cutting bone. Thus, Gigli wire stands out as the appropriate choice for this specific task.