A robotic surgical instrument , comprising: a housing having a shaft extending therefrom including an end effector assembly at a distal end thereof, the shaft including a drive rod extending therethrough configured to actuate the end effector assembly upon translation thereof; a spring compression assembly supported within the housing, the spring compression assembly including: a proximal hub configured to secure a proximal end of the drive rod disposed therethrough, the proximal hub including a plurality of teeth disposed along an inner peripheral surface thereof; a distal hub spaced from the proximal hub and including a plurality of teeth disposed along an inner peripheral surface thereof; and a compression spring mounted between the proximal and distal hubs; a drive gear including a proximal portion extending therefrom including a plurality of threads disposed thereabout configured to matingly engage the corresponding plurality of teeth of the proximal and distal hubs such that rotation thereof translates the proximal and distal hubs relative to one another and actuates the end effector assembly; and a thumb wheel having at least a portion thereof exposed outside the housing for external manipulation thereof, characterised in that the thumb wheel is selectively positionable between a first, disengaged position spaced relative to the drive gear and a second, engaged position to matingly engage the drive gear and allow manual actuation of the end effector assembly. a housing having a shaft extending therefrom including an end effector assembly at a distal end thereof, the shaft including a drive rod extending therethrough configured to actuate the end effector assembly upon translation thereof; a spring compression assembly supported within the housing, the spring compression assembly including: a proximal hub configured to secure a proximal end of the drive rod disposed therethrough, the proximal hub including a plurality of teeth disposed along an inner peripheral surface thereof; a distal hub spaced from the proximal hub and including a plurality of teeth disposed along an inner peripheral surface thereof; and a compression spring mounted between the proximal and distal hubs; a proximal hub configured to secure a proximal end of the drive rod disposed therethrough, the proximal hub including a plurality of teeth disposed along an inner peripheral surface thereof; a distal hub spaced from the proximal hub and including a plurality of teeth disposed along an inner peripheral surface thereof; and a compression spring mounted between the proximal and distal hubs; a drive gear including a proximal portion extending therefrom including a plurality of threads disposed thereabout configured to matingly engage the corresponding plurality of teeth of the proximal and distal hubs such that rotation thereof translates the proximal and distal hubs relative to one another and actuates the end effector assembly; and a thumb wheel having at least a portion thereof exposed outside the housing for external manipulation thereof, characterised in that the thumb wheel is selectively positionable between a first, disengaged position spaced relative to the drive gear and a second, engaged position to matingly engage the drive gear and allow manual actuation of the end effector assembly. <EOS>