The present disclosure provides a modular instrument system for accessing a site within a patients body, such as for example, to inject or remove material. In one exemplary embodiment, an access device is coupled to an adapter and power drilled into a site within a patient. Once the access device is in position, the adapter may be further attached to other instruments, or to an injection or extraction system. The adapter may accommodate various other connectors to make the instrument system compatible with a variety of other surgical instruments and tools.