Which screw is identified as being flat-ended?

The correct answer is the cortical screw, which is specifically designed with a flat-ended tip. This design allows for optimal engagement with the dense cortical bone, enabling better stability and fixation during surgical procedures. The flat end helps to effectively penetrate the cortical layer of bone, providing the necessary grip and anchorage in orthopedic applications. This characteristic is essential for ensuring that the screw can withstand the forces exerted during movement and support bone healing.

In contrast, cancellous screws typically have a self-tapping point that is designed to work with the softer, cancellous bone. A plate bender is a tool used to shape orthopedic plates rather than a type of screw, and McPhail's needle holder is a surgical instrument used for suturing rather than screw fixation. Understanding these distinctions is crucial in mastering the identification and application of various veterinary surgical instruments.