An instrument device manipulator (IDM) is attached to a surgical arm of a robotic system and comprises a surgical tool holder and an outer housing. The surgical tool holder includes an attachment interface that can secure a surgical tool in a front-mount configuration (where the attachment interface is on a face opposite of a proximal extension of the surgical tool) or a back-mount configuration (where the attachment interface is on the same face as the proximal extension of the surgical tool). The surgical tool holder may rotate continuously within the outer housing. In a back-mount configuration, the surgical tool holder may have a passage that receives the proximal extension of the tool and allows free rotation of the proximal extension about the rotational axis. A surgical drape separates the IDM and robotic arm from a tool, while allowing electrical and/or optical signals to pass therebetween.
