IEEE TRANSACTIONS ON ROBOTICS AND AUTOMATION, VOL. 19, NO. 5, OCTOBER2003 893 Bone-Mounted Miniature Robot for Surgical Procedures: Concept and Clinical Applications Moshe Shoham, Member, IEEE, Michael Burman, Eli Zehavi, Leo Joskowicz, Senior Member, IEEE, Eduard Batkilin, and Yigal Kunicher Abstract—This paper presents a new approach to robot-assisted spine and trauma surgery in which a miniature robot is directly mounted on the patient’s bony structure near the surgical site. The robot is designed to operate in a semiactive mode to precisely po- sition and orient a drill or a needle in various surgical procedures. Since the robot forms a single rigid body with the anatomy, there is no need for immobilization or motion tracking, which greatly en- hances and simplifies the robot’s registration to the target anatomy. To demonstrate this concept, we developed the MiniAture Robot for Surgical procedures (MARS), a cylindrical 5 7 cm , 200-g, six-degree-of-freedom parallel manipulator. We are currently de- veloping two clinical applications to demonstrate the concept: 1) surgical tools guiding for spinal pedicle screws placement; and 2) drill guiding for distal locking screws in intramedullary nailing. In both cases, a tool guide attached to the robot is positioned at a planned location with a few intraoperative fluoroscopic X-ray im- ages. Preliminary in-vitro experiments demonstrate the feasibility of this concept. Index Terms—Image-based robot registration and targeting, medical robotics, orthopaedics, surgical robots. I. INTRODUCTION R OBOT-ASSISTED surgery (RAS) is an emerging inter- disciplinary field whose aim is to provide surgeons with tools that enhance and complement their free-hand abilities during surgery. The goals are to improve the outcome of surgical procedures, to reduce intraoperative time, to reduce the invasiveness of a procedure, or to enable new procedures altogether. Since their inception in the early 1990s, a few dozen surgical robot prototypes have been developed, with the most prominent being the commercial system ROBODOC (Integrated Surgical Systems) and more recently the Da Vinci (Intuitive Surgical) and Zeus (Computer Motion) systems for remotely manipulated minimally invasive procedures. For recent surveys in medical robotics, see [6] and Troccaz et al., 2002. The main expected advantages of surgical robots are: • higher accuracy; Manuscript received February 24, 2003. This paper was recommended for publication by Associate Editor P. Dario and Editor R. Taylor upon evaluation of the reviewers’ comments. M. Shoham is with the Faculty of Mechanical Engineering, Technion—Is- rael Institute of Technology, Haifa 32000, Israel (e-mail: shoham@tx.tech- nion.ac.il). M. Burman, E. Zehavi, E. Batkilin, and Y. Kunicher are with Mazor Surgical Technologies, Caesarea 38900, Israel. L. Joskowicz is with the School of Computer Science and Engineering, The Hebrew University of Jerusalem, Israel (e-mail: josko@cs.huji.ac.il). Digital Object Identifier 10.1109/TRA.2003.817075 • ability to work according to preplanned image-based pro- gram; • reduction of the surgeon’s hand tremor ([18], [26]); • ability to operate in remotely manipulated minimally in- vasive procedures; • reduction of the surgeon and operating staff radiation ex- posure ([20], [25]); • reduction of operating room staff. Despite this extensive and promising list of advantages, and of more than ten years of RAS research, the impact of surgical robots has been very limited, so far, to remotely manipulated minimally invasive procedures. The total worldwide number of surgical robots is less than 1000. While it is common knowl- edge that the medical profession is conservative and slow in its adoption of new developments, it appears that the potential of surgical robotics should have resulted in more than a handful of applications. There are several reasons for the slow assimilation of surgical robots in the operating room. We focus in particular on three main limitations of surgical robots. • Contemporary medical robots are voluminous. They oc- cupy too much precious operating room space and raise safety issues. • Commercial surgical robot systems are expensive ($300 000 to $1 000 000). Their use is thus limited to the few large research hospitals that can afford them. • The patient anatomy needs to be immobilized by fixing it to the operating room table, or compensated for by tracking it in real time and adjusting the fixed robot position accordingly. In this paper, we propose a new approach to medical robotics that addresses these issues with a miniature robot that is directly mounted on the patient anatomy. Table I summarizes the char- acteristics of this type of system as compared to navigation and fixed floor- or bed-mounted robots. We first describe the con- cept, an embodiment of it, and discuss two clinical applications currently under development: 1) surgical tool guiding for spinal pedicle screws placement; and 2) drill guiding for distal locking screws in intramedullary nailing. II. BONE-MOUNTED MINIATURE ROBOT: RATIONALE AND SYSTEM CONCEPT Many minimally invasive clinical applications for which RAS is applicable require a small operating workspace. Examples include spine surgery, femoral head fracture fixation, cardiac 1042-296X/03$17.00 © 2003 IEEE