Embodiments of the invention include a system for guiding an instrument. The system may include a frame and a bearing assembly supported by the frame. The bearing assembly may include an outer tubular member supported by the frame and including a proximal end and a distal end. The bearing assembly may also include a bearing at least partially disposed within at least one of the proximal end and the distal end of the outer tubular member. The channel may extend through the outer tubular member and the bearing.
