This paper presents the evaluation of two detachable MR-Conditional needle driver designs for our 4-degree-of-freedom (DOF) robotic platform for MRI-guided spinal injections. Compared to their predecessor, the new designs open up the possibility of intraoperative needle driver attachment, and in order to evaluate the feasibility of such an approach, force and torque requried during the needle driver attachment process are captured to evaluate which of the two designs are better suited for such purpose. A simulated clinical scenario is also carried out to measure the possible position change of the 4-DOF robot with respect to the patient due to intraoperative tool attachment, thus providing future guidance to the proposed clinical workflow in the framework of body-mounted robotic surgical devices.