25.1 Introduction

Pedicle screw constructs are a widely accepted modality for deformity correction and spinal stabilization. Implantation can be technically challenging particularly in patients with severe deformity, osteoporosis, or malignancy. Misplaced screws may lead to devastating neurologic and vascular complications. Pedicle screw–related complications have been reported to range from 1 to 6%. ^{1 ,​ 2 ,​ 3 ,​ 4 ,​ 5 ,​ 6} This has led to the development of new techniques to improve safety and accuracy. One such advancement involves a computer-assisted robotic device that guides pedicle screw placement based on a preoperatively planned trajectory (MAZOR Robotics, Ltd., Israel). ^{7 ,​ 8} This chapter will focus on the surgical technique of the Renaissance System, which is composed of two main components, the Renaissance Workstation and the RBT device (Fig. 25‑1).

The technique can be divided into four steps: (1) Planning; (2) Frame construct; (3) Registration; and (4) Screw insertion. All four steps will be discussed below, followed by a section on additional pearls. Use of the robotic system is possible for open or percutaneous techniques.

25.2 Planning

The patient undergoes a preoperative computed tomographic (CT) scan of the thoracic spine following Mazor’s Renaissance low-dose protocol (~150–200 mA) with continuous, 1-mm cuts. This can be done using any CT scanner. Using a flash drive or DVD, the CT scan is then transferred to any computer that has been loaded with Mazor’s Renaissance software. The surgeon is then able to evaluate the patient’s anatomy, and plan all aspects of screw decision-making such as screw size, location, starting point, and trajectory. Screw accuracy is confirmed in axial, sagittal, and coronal planes. This allows for ideal screw position in each pedicle. Once all the screws have been planned, rods are virtually added, allowing the surgeon to view the planned construct in multiple planes. This is an extremely helpful step as screw adjustments can be made as needed to allow for better alignment of the entire construct. The plan is then transferred via flash drive to Mazor’s intraoperative workstation, available for the day of surgery, and can be further edited directly on the workstation at any time if needed. Another option, if available, is to perform an intraoperative CT scan after the patient has been placed under anesthesia and positioned for surgery, then directly transfer the CT images to the Mazor workstation and construct the plan directly on the workstation in the OR.

25.3 Frame Construct

There are four mounting options for the Mazor robotic system depending on the clinical indication and preference: a clamp mount, a multidirectional bridge mount, a bed mount, and a Hover T mount. All mounting options are rigidly attached to the patient’s spine to ensure maximum accuracy of screw placement. When instrumenting the thoracic spine, the Hover T is a popular option due to its bony fixation to the patient. It may be utilized in open and MIS procedures. Typically for thoracic pedicle screws, side block assemblies will be mounted on the cross bar so that the ball-and-socket joints face the feet of the patient. The side blocks are fixed to the patient using 4-mm Schantz pins. Afterward, the bridge is inserted through the cross bar and stabilized cranially using a 2.5-mm head pin inserted into the spinous process (Fig. 25‑2). The spinous process selected should be two levels above the planned vertebra to be instrumented. The bridge should hover freely without any external pressure but be placed as close as possible to the skin.

In open procedures, the clamp is a commonly utilized option and is attached to the spinous process centered over the area of interest. After performing a bilateral paraspinal exposure, the clamp mount may be attached. Next, a bridge is connected and fixed on each end with a K-wire inserted into the adjacent spinous processes maximizing stability (Fig. 25‑3). This technique is typically utilized for scoliosis and similar deformity cases. However, it may be utilized in MIS cases as well. At the minimum, a 3-cm incision is required in order to seat the clamp.

The multidirectional bridge is another mounting option that provides maximum stability. Prior to draping, bed adapters are attached to the bed rail on each side of the patient. These are typically placed just caudal to the planned incision. After draping, the bed adapters may then be fixed to the bed rail via an adapter that is underneath the drapes. The bed adapters should be positioned across from each other. The adapters should be maximally tightened because failure to do so may lead to wobbling of the bridge and inaccurate screw placement. A 2.5-mm head pin is then inserted directly into a spinous process above the planned instrumentation. It is essential that the pin has good purchase in the spinous process to maximize stability of the bridge. The multidirectional bridge is then attached so that it hovers directly over the patient. There should be minimal contact between the bridge and the patient as this can result in undue pressure on the bridge leading to screw malposition. The bridge may now translate laterally in either direction parallel to the patient’s spinal column.