The Role of Intraoperative Navigation in Orthopaedic Surgery

Alexa J. Karkenny, MD; Joseph R. Mendelis, MD; David S. Geller, MD; Jaime A. Gomez, MD


J Am Acad Orthop Surg. 2019;27(19):e849-e858. 

In This Article

Principles of Intraoperative Navigation

Intraoperative navigation can be fluoroscopy- or CT-based, or can rely on an imageless system. Table 1 summarizes navigation systems widely available in the United States. Fluoroscopy-based systems recognize markers that are placed on anatomic landmarks and captured on radiographs, whereas other systems can import an intraoperative CT or perform 3D reconstruction of two-dimensional images. These images are then coupled to a navigation software platform. Figure 1, A and B demonstrates the use of intraoperative navigation software coupled with an intraoperative CT for pedicle screw placement. Imageless systems, on the contrary, typically require the surgeon to place markers on anatomic landmarks that are recognized by an optical camera, and then a computer processes these markers in conjunction with a stored CT (preoperative or intraoperative) to generate a virtual model. Further, navigation systems can be categorized as passive or active. Passive navigation platforms provide imaging information without placing any restraint on the surgeon's actions.[4] For instance, a preoperative CT can be merged with the intraoperative robotic-arm guidance to help a joint arthroplasty surgeon adhere to planned joint resection boundaries, providing visual feedback to the surgeon when those boundaries are respected or violated. In contrast, active navigation systems directly perform a task or prevent a surgeon from violating a predetermined boundary or pathway. For example, Figure 2, A and B shows an imageless active navigation system, in use during pedicle screw placement for adolescent idiopathic scoliosis. A preoperative spine CT is used to 3D-print models of each vertebral level, which are then used to create patient-specific guides for each vertebral level which constrain drills to predetermined pedicle screw trajectories.

Figure 1.

A, Photograph showing how the surgeon uses intraoperative navigation coupled with an intraoperative CT to place pedicle screws during posterior spinal fusion for adolescent idiopathic scoliosis. The reference array is placed on the spinous process (bottom right). The silver markers on the reference array and the coupled pointer (center) are recognized by an optical camera. B, The photograph shows the intraoperative navigation software interface during pedicle screw placement. The surgeon uses navigation to confirm safe pedicle screw placement by placing the coupled pointer into the pedicle screw tract created, which is superimposed on the axial (left) and sagittal (right) CT cuts visible to the surgeon.

Figure 2.

A, The photograph shows the use of the FireFly system, an example of imageless, active navigation. A preoperative CT is used to create a three-dimensional (3D)-printed model of the spine (bottom center). Pedicle screw trajectories are planned preoperatively and used to 3D-print the corresponding jigs for each vertebral level (center). The jig is held at the corresponding vertebral level, and drill guides are placed into the jig. B, The drill guide placed into the jig actively guides the surgeon to drill in the pre-determined pedicle trajectory.

Regardless of the imaging modality or anatomic location, the basic principles of intraoperative navigation remain the same. The spatial relationship between preoperative imaging or intraoperative imaging and patient-specific anatomy must first be established.[4] Navigation software establishes this relationship through the registration of patient anatomy. Anatomic landmarks such as a spinous process or iliac crest are registered, or matched, to the corresponding points on the preoperative or intraoperative imaging that was imported into the navigation software. The registration process may occur before navigation, in which case any inadvertent movement of the landmarks at any time after registration can disrupt the accuracy of navigation. On the other hand, if intraoperative 3D imaging is used, the registration process may be automated during the operation.