A robotic surgical system includes a surgical robotic arm an electromechanical instrument an instrument drive unit and a coupling shaft. The electromechanical instrument is configured to be detachably coupled to the surgical robotic arm. The electromechanical instrument includes a shaft having a proximal end and a distal end having an end effector. The instrument drive unit includes a motor configured to actuate the end effector. The coupling shaft defines a longitudinal axis and is configured to be coupled between the instrument drive unit and the surgical robotic arm such that the instrument drive unit is rotatable about the longitudinal axis of the coupling shaft relative to the surgical robotic arm or the electromechanical instrument.
