What instrument is necessary after drilling an initial hole to assist with screw insertion in orthopedic surgery?

The depth gauge is essential after drilling an initial hole because it accurately measures the depth of the hole created in the bone. This measurement is crucial for ensuring that the screw is adequately inserted without penetrating too deeply or inadequately engaging the bone. Utilizing a depth gauge helps the surgeon determine the correct length of the screw needed to achieve adequate fixation while avoiding potential complications such as screw breakage or injury to surrounding structures.

The other instruments listed serve different purposes; for example, a scalpel is used for making incisions in tissue, a drill bit is part of the initial drilling process, and a hemostat is used to control bleeding by clamping blood vessels. None of these fulfill the specific function of measuring hole depth necessary for safe and effective screw placement in orthopedic procedures.