Vision Based Robotic Navigation: Application to Orthopedic Surgery

Vision guided medical technologies are currently emerging that will influence the way in which orthopedic procedures are diagnosed, planned, simulated, and performed. Medical robotics is one such field that has benefited through the recent advances in the fields of medical imaging and computer vision (Miyamoto, Sugiura et al. 2003). The orthopedic specialty presents several opportunities to the application of vision guided robotic technology. Radiographic imaging technologies such as c-arm fluoroscopy, X-ray and CT (Computed Tomography) can be used as medical imaging modalities for bony anatomy. The latter is of considerable interest as it enables the building of 3D bone models pre-operatively which permits pose estimation during operative procedures. Moreover, unlike soft tissue, the procedures that involve the manipulation of bones are able to withstand an applied force from tools (robotics) without significant deformation. This has lead to the development of orthopedic robotic technologies including several for femur fracture realignment (Joskowicz L, Milgrom C et al. 1998; Graham and Xie 2007; Westphal R, Winkelbach S et al. 2007). Our work focuses on femur fracture orthopedics with an emphasis on a procedure for fracture reduction called closed intramedullary nailing. The procedure initially requires the alignment of the proximal and distal segments of the bone followed by the insertion of a nail into the medullary cavity of the long bone, typically inserted minimally invasively through the proximal part of the femur. Finally lateral locking screws are placed to hold the nail in place. Intramedullary nailing is performed for cases of femur shaft fractures which are commonly caused by high-energy injury mechanisms (e.g. traffic accidents or heavy falls). Statistics gathered by (Westphal, Winkelbach et al. 2007) indicate an approximate femur fracture incidence rate of 37 per 100,000 persons per year, and thus it is a frequently encountered injury. In 2004, 3200 patients with fractures of the thigh bone have been counted in New Zealand (Cure-Research 2004). These figures include fractures in the proximal (hip side) femur as well as the shaft (the middle, diaphyseal) region. Intra-operative fluoroscopy is the imaging modality utilized for visualizing underlying bone and surgical tool positions in femur fracture orthopedic procedures. Fluoroscopic image guidance of robotic systems can be divided into two categories: 1) open loop calibrated guidance 2) closed loop un-calibrated guidance. Open loop calibrated guidance methods 7