15 Robotic Instrumentation for Lumbosacral Spondylolisthesis

10.1055/b-0039-172726

15 Robotic Instrumentation for Lumbosacral Spondylolisthesis

Michael R. Conti Mica, Michael P. Silverstein, R. Alden Milam IV, and Eric B. Laxer

Abstract:

Instrumentation for the surgical treatment of lumbosacral spondylolisthesis can be performed with the use of a surgical robotic guidance system. This chapter discusses the use of the Mazor Renaissance Guidance System for posterior instrumentation of isthmic and degenerative spondylolisthesis. We describe an approach to preoperative planning, building the appropriate frame construct, registration, and the execution of percutaneous conventional pedicle screws or open cortical pedicle screws in combination with either an anterior lumbar interbody fusion or transforaminal lumbar interbody fusion. Pearls to avoid common complications and pitfalls are presented.

15.1 Introduction

The most common type of spondylolisthesis that occurs at L5–S1 is isthmic. ¹ While the vast majority of patients are asymptomatic, symptomatic patients tend to present with mechanical back, buttock, and referred posterior thigh pain due to segmental instability. Patients may also present with L5 radicular symptoms due to foraminal stenosis caused by fibrous tissue emanating from the pars defect and spondylosis of the disk. Less frequently, degenerative spondylolisthesis may occur, with a similar presentation of back and leg pain in the L5 or S1 distributions.

This chapter describes the techniques for robotic-assisted instrumentation for the treatment of lumbosacral spondylolisthesis using the Mazor Renaissance Guidance System (MRGS; MAZOR Robotics, Inc., Orlando, FL).

15.2 Surgical Indications, Contraindications, and Options

The primary surgical indications for lumbosacral spondylolisthesis are persistent symptoms refractory to nonsurgical care, neurological deficit, and slip progression. Contraindications include, but are not limited to, active infection and uncontrolled medical comorbidities. Patients with such conditions should be medically optimized prior to surgery. ²

Surgical options include the following:

Anterior lumbar interbody fusion (ALIF) combined with posterior percutaneous pedicle screws.
Transforaminal lumbar interbody fusion (TLIF) combined with cortical screws or conventional pedicle screws.
Pars repair with direct screw insertion and bone grafting. While robotic guidance can be used for this technique in the setting of spondylolysis, this technique is not discussed in this chapter.

Options 1 and 2 provide for stabilization of the segmental instability and indirect foraminal decompression. Foraminotomy can be added if direct decompression is preferred by the surgeon; however, this is typically not the approach of the authors. The role of the robot during these cases is to assist the surgeon with safe and accurate screw placement.

This chapter will focus on the general steps common to all procedures using the Mazor Renaissance Guidance System, followed by additional details on the first two surgical options listed earlier based on the techniques we use.

15.3 Steps for Use of the Mazor Renaissance Guidance System

There are four steps that are common to all cases when using the MRGS:

Preoperative planning. A preoperative thin section CT scan from the lower thoracic spine to the sacrum is performed following the manufacturer’s protocol. This is typically obtained prior to the day of surgery, but may be done on the day of surgery with an intraoperative CT scanner. The images are then loaded into a computer with Mazor’s proprietary planning software. Planning is based on full details of vertebral, spinal canal, and foraminal anatomy. The software allows for the assessment and selection of optimal screw position and trajectory. Additionally, planning is useful for screw head alignment to facilitate the seating of the rods. The plan is then transferred to Mazor’s intraoperative computer workstation.
Frame construct. Once the patient is placed under anesthesia, positioned, prepped, and draped for surgery, a frame is constructed using several different options based on the surgical plan. The frame requires a cephalad spinous process pin, and either a set of caudad pelvic pins or table-mounted posts called “Condors.” The frame is completed by attaching a bridge to these cephalad and caudad anchoring points to which the robotic device will be attached.
Registration. Intraoperative fluoroscopy is used to register the patient’s spine anatomy with the preoperative CT scan. This allows the planning software to recognize the patient’s spine and execute the operative plan.
Screw preparation and insertion. The surgical team works with the manufacturer’s intraoperative staff and uses the robotic guidance system to sequentially drill a pathway, insert guidewires, and place screws.

15.4 Details of the ALIF and TLIF Techniques

15.4.1 Anterior Lumbar Interbody Fusion Combined with Posterior Percutaneous Conventional Pedicle Screws Using the Mazor Bed Mount Assembly

Following completion of a standard ALIF, the patient is subsequently positioned prone on a Jackson table.

The following steps are then performed:

The cephalad anchoring point is attached. A spinous process pin is drilled into the L1 or L2 spinous process. Fixation of this pin must be secure. Fluoroscopy is used to confirm the correct level, pin depth, and orientation. The entrance point usually corresponds to the level of the disk space just caudad to the spinous process. For example, the L1 spinous process pin will usually be in line with the L1–L2 disk space.
The caudad anchoring point is attached. A single Condor is connected to the table using a table clamp. Fixation of the clamp to the Jackson table and fixation of the Condor to the clamp must be secure. Any toggle of the Condor could result in inaccurate screw insertion.
The bed mounted platform and bridge are connected to the spinous process pin cephalad, and the Condor caudad (Fig. 15‑1 , Fig. 15‑2).
Registration is performed by securing the yellow three-dimensional (3D) marker on the bridge at the level of surgery and taking 60- and 90-degree fluoroscopic images, which are then sent to the workstation and used to match the operative plan to the patient’s intraoperative position.
A pedicle is selected for screw insertion. The robotic device is secured to the bridge (Fig. 15‑3); the workstation sends the screw trajectory coordinates to the robotic device which then positions itself to the desired starting point and trajectory. There are several attachment options to the robotic device and the surgeon assembles those designated by the workstation onto the robot. There is a short arm that extends from these attachments that represents the planned trajectory.
The surgeon passes a scalpel through the arm and makes a small skin incision at the point of entry based on the screw trajectory. This is extended slightly and deepened past the lumbodorsal fascia. A trocar and cannula are passed through the arm, tissues, and docked onto bone. Tactile awareness is important to audit for any potential skive. If that is a concern, the surgeon may remove the trocar and use the Peteron device through the sleeve to flatten the point of bone contact and minimize the skive risk. The drill guide is then inserted and a lateral fluoroscopic image is obtained to verify that the trajectory is consistent with what was planned. The screw pathway is then drilled. A reduction tube and safety guidewire are then passed together through the drill guide and seated into bone, passing through the pedicle and into the back of the vertebral body. The surgeon can feel the crepitus of the cancellous bone, as this occurs until a firm endpoint is reached. The reduction tube is then removed, and care must be taken to protect the guidewire. This is repeated for the three other screws.
Anteroposterior (AP) and lateral fluoroscopic images are obtained to confirm all four guidewires are well placed.
The screws are then inserted and the wires removed (Fig. 15‑4).
Incisions are extended as needed and the construct is completed by inserting rods and caps.
The incisions are irrigated and hemostasis is obtained. The fascia is closed with 0 Vicryl suture as needed; the subcutaneous tissues approximated with 2–0 Vicryl suture; and the skin is closed with a buried, running 3–0 Monocryl subcuticular suture. Sterile dressings are placed.

Fig. 15.1 Illustration of the bed mount frame, platform, and bridge. Note the spinous process pin cephalad and the bed mount Condor caudad with the large tightening knob on top. (From the Mazor Renaissance Surgical Technique guide for Hover-T, Bed Mount, and Multidirectional Bridge. Image provided by Medtronic.)

Fig. 15.2 Assembled bed mount frame, platform, and bridge. Cephalad is to the right. Note the spinous process pin cephalad and the bed mount Condor caudad on the far side of the table, with the large tightening knob at the top.

Fig. 15.3 Robotic device (blue, right side of image) attached to frame and ready for use.

Fig. 15.4 Screw preparation and insertion. Note the blue Mazor robotic device is on the other side of the screwdriver (just to the right of the blue arrow).