Devices and techniques for separating tissue

Devices, systems, and techniques are described for creating pockets in tissue for accepting implantable medical devices. For example, a surgical tool includes a shaft defining a proximal end, a distal end, and a longitudinal axis, a handle coupled to the proximal end of the shaft, and one or more blades configured to move between a retracted configuration and a deployed configuration, wherein the one or more blades extend, in the deployed configuration, substantially perpendicular to the longitudinal axis at the distal end of the shaft. The one or more blades may be configured to separate tissue in the deployed configuration.