MIS: Rory J. Petteys, Anthony Conte, and Faheem A. Sandhu
Open: Jason C. Eck

The patient is brought to the operating room where general endotracheal anesthesia is administered. A Foley catheter is inserted, pneumatic compression devices and neurophysiological monitoring leads placed, and an arterial line may be used if indicated. The patient is then positioned prone on a Jackson flat top table with chest roll(s) to maintain lumbar lordosis. Preoperative antibiotics are then administered. The fluoroscopic arm is then positioned such that the base of the device is on the side opposite the surgeon. The surgeon should stand on the side of the most significant pathology or symptoms.

Using anteroposterior fluoroscopy, the midline is marked on the skin and a parallel line is drawn 4 to 4.5 cm away on the side nearest the surgeon. Then, using lateral fluoroscopy, the correct levels are identified and marked. For two-level TLIF, the incision should span the intervening vertebral body from one disc space to the next along the paramedian line that was previously marked with the incision centered over the pedicle of the middle lumbar level. The patient is then draped after antiseptic is applied and the skin is infiltrated with local anesthetic. The level with the worst pathology or referable symptoms should be addressed first. A small puncture is made with a number 11 blade over the disc space and a Kirschner wire or Steinmann pin is inserted along a slight medial trajectory under fluoroscopic guidance. The goal is to “dock” the wire on the ipsilateral facet joint of the level in question. Once “docked” at the appropriate level, the incision is lengthened to accommodate a 25-mm tubular retractor. Serial dilators are then inserted followed by the tubular retractor, which is secured by a table-mounted arm. Final placement is then confirmed by fluoroscopy.

With the working channel in place, it is important to confirm placement under direct visualization. Ideally, the laminofacet junction should be in the lateral half of the working field and the lateral half of the lamina in the medial field. Electrocautery is then used to clear the field of remaining muscle and soft tissue until the facet and lamina are exposed. The sublaminar plane is defined with curettes and the ligamentum flavum elevated from the underside of the lamina. This will help ensure the ligamentum remains intact during bone removal, thus minimizing the risk of dural injury. A generous hemilaminotomy and facetectomy is then performed with curettes, rongeurs, and high-speed drill, and should extend from the rostral to the caudal pedicle. Bone fragments can be harvested to use later as autograft.

Once the discectomy is completed, pedicle screws can then be placed under direct visualization. If a two-level TLIF is planned, the retractor is then removed and a Steinmann pin or Kirschner wire is advanced through the skin incision under fluoroscopic guidance toward the facet of the next level to be addressed. Typically, this will require more rostrocaudal angulation than is used for a single-level TLIF. Serial dilators are advanced and the retractor is “docked” at the laminofacet junction in the manner described above. The removal of bone and ligament and discectomy proceeds as described above. A second interbody graft is placed once the discectomy and end-plate preparation is completed. Pedicle screws are then placed at the remaining two levels under direct visualization and a rod is placed. The disc spaces can then be compressed prior to securing the rod. The lumbodorsal fascia and skin are then closed in layers. Percutaneous pedicle screw fixation is then performed on the contralateral side.

The patient is brought to the operating room and undergoes general anesthesia with endotracheal intubation. The patient is then turned to the prone position on the Jackson table with standard precautions to avoid decubitus ulcers and minimized upper extremity neuropraxia. The patient should be positioned to maintain the normal lordotic lumbar spine curvature. Positioning should allow for intraoperative radiographic imaging to confirm spinal alignment and implant position.

A lateral fluoroscopic image can be obtained to verify the location of the operative levels. A midline posterior incision is made over the operative levels, and the erector spinous muscles subperiosteally elevated to expose the posterior elements of the spine bilaterally. The spinous processes, laminae, facet joints, pars interarticularis, and transverse processes are visible. Self-retaining retractors are placed to maintain exposure and should be released and repositioned at least each hour to maintain adequate soft-tissue perfusion. A lateral image can then be obtained to verify operative levels.

Exposure for the TLIF is achieved by removing the superior and inferior articulating processes of the facet joint and performing a hemilaminotomy and partial resection of the pars interarticularis. This provides a rectangular window through which you can visualize the underlying disc space, lateral edge of the dura, and the exiting nerve root.

The disc space can then be exposed by removing the overlying ligamentum flavum and fatty tissues. With careful nerve root protection, a 15-blade scalpel can then be used to incise the posterolateral annulus. The annulotomy should be large enough to pass the interbody implant after the disc space is final prepared. A lamina spreader can be utilized if needed for further distraction to facilitate passage of instruments into the disc space. A series of curettes and pituitary rongeurs can be used for removal of the disc material. The end plates can be prepared with a variety of curettes and shavers. Meticulous discectomy and end-plate preparation are essential for facilitating interbody fusion. Once the disc space is prepared, trial inter-body spacers are placed to determine the optimal implant size. Implants are available in a wide variety of sizes, shapes, and materials based on surgeon preference. The implant should be selected to maximize the contact of the implant and the prepared end plates. Morselized bone graft is then placed into the periphery of the disc space, followed by placement of the implant. Any previously placed distraction should be removed, and the implant should be assessed for adequate tightness in the interbody space. Any remaining voids in the interbody space can be filled with additional morselized bone graft.

Pedicle screws are then placed bilaterally in the vertebrae above and below the disc to be fused. Placement of the pedicles screws can be performed through a variety of techniques including anatomic placement, fluoroscopically guided placement, or computer navigation–assisted placement. After placement of the pedicles screws, connecting rods are placed, set caps applied, and final tightened to the rods. Anteroposterior and lateral images should be obtained to verify proper placement of the interbody implant and pedicle screws. Decortication of the transverse processes and remaining lamina and placement of additional bone graft allow for a 360° fusion. A standard layered closure is then performed after achieving meticulous hemostasis.

There are no level I studies available.

To date, there has been no level I study comparing MIS and open TLIF, although a number of level III/IV retrospective studies have been performed. Several studies since the initial report by Foley et al have also demonstrated benefits of MIS TLIF over standard open techniques in head-to-head comparison.