Another small diameter working port for interbody fusion instruments is inserted under the guidance of Nitinol wire and serial dilators. The intervertebral disc space is further cleaned, and the end plate is prepared with a drill, expandable butterfly-featured blade, back-bite instrument, and stainless brush (Fig. 9.3). A curved probe can be utilized to confirm completion of cartilage removal and end plate preparation. A balloon, which can be filled with radio-opaque contrast, is inflated in the disc space to demonstrate the thoroughness of discectomy and to evaluate the size of the intervertebral cage required (Fig. 9.4). Recombinant human bone morphogenetic protein (rhBMP)-2 is inserted into the disc space to facilitate bone fusion. Instead of the rigid cage commonly used for regular MIS-TLIF, an expandable cage (OptiMesh cage, Spineology) is then placed into the disc space. The OptiMesh cage is filled with allograft matrix, which is able to inflate and lift the disc height, and reduced by the spondylolisthesis (Fig. 9.4). The OptiMesh cage should be placed anteriorly and centrally to enhance lumbar lordosis.

Pedicle screws are placed percutaneously with true anterioposterior (AP) fluoroscopic imaging. Small skin incisions are made for each screw. When the C-arm is aligned to produce a true AP image, Jamshidi needles are docked on the base of each transverse process, adjacent to the lateral aspect of facet joint. The Jamshidi needle is advanced 2 cm into the bone without breaching the medial wall of the pedicle. At this point, the tip of the Jamshidi needle should be at the junction of the pedicle and vertebral body. The Jamshidi needle is further advanced into the body and then exchanged with K-wire. The depth of the Jamshidi needle and K-wire can be checked with lateral-view fluoroscopy. The Jamshidi needle shaft is then removed, while the K-wire is kept inside the vertebral body. The K-wire is vital during the screw placement and should always be held in place (Fig. 9.5). Insertion of the insulated sheath, awl, and tap is performed step by step under the guidance of the K-wire before placement of each percutaneous screw. The procedure of percutaneous screw placement may vary depending on the instrument system used. Rods are inserted percutaneously in an extension maneuver. This allows the spine to be further realigned for spondylolisthesis and better lordosis curvature. Final set screws are tightened and locked in position (Fig. 9.6).

Each small incision made for the endoscope and percutaneous screws is sutured and closed layer by layer in the normal fashion. There is usually no drain placement required.

Due to the nature of the non-general anesthesia in awake TLIF, patients’ recovery from surgery is quite fast and favorable. There is usually less consumption of analgesic and narcotic medications. The majority of the patients are discharged from the hospital on postoperative day 1.

Further postoperative care was much the same as with a standard TLIF procedure. A lumbar brace was recommended. Lifting heavy weight, excessive forward bending, and smoking were relatively prohibited. Nonsteroid anti-inflammatory drugs were not suggested for pain control in the first several months after surgery to avoid interfering with the bone growth. Regular follow-up clinic visits and radiographic film examination for bone fusion are recommended.

Standard MIS-TLIF is performed throughout the world with the assistance of the surgical microscope. While successful outcomes and a low-risk profile can be accomplished with the standard MIS-TLIF, surgeons desire even less tissue injury and blood loss, faster recovery, and shorter hospital stays. Fundamental technical changes were required to achieve an even less invasive surgery, the awake TLIF (Table 9.1).

Anesthesia is one of the most significant aspects of any operation. Awake TLIF is possible only with the aid of awake anesthesia. Awake anesthesia generally involves (but is not limited to) an oxygen supply without endotracheal intubation, airway management of a prone-positioned patient, adequate status of conscious sedation with intravenous infusion of propofol, and intraoperative organ status monitoring. This usually requires an experienced anesthesiologist to deal with the entire situation intraoperatively. Postoperative recovery is a part of awake anesthesia. Proper management of postoperative pain, fluid status, organ metabolism, glucose and insulin metabolism, and homeostasis requires a multidisciplinary team, consisting of neurosurgeons, anesthesiologists, the recovery unit, and nurse practitioners. Awake anesthesia also involves the concept of enhanced recovery after surgery (ERAS^®), which is scarcely applied in the neurosurgical field. ERAS is discussed in greater detail below.

Standard MIS-TLIF requires a tubular or expandable retractor and a microscope to access the targeted structure. Dissection and injury of subcutaneous and muscular tissue are inevitable with this approach. With the evolution of illumination and camera systems, Dr. Parviz Kambin first visualized and removed a herniated lumbar disc using endoscopic instruments in 1988. Endoscopy advanced the era of direct visualization to image-assisted surgery, allowing surgeons to cut an 8-mm incision and operate with the aid of a high-resolution scope lens and image screen. The soft tissue injury is minimal, as there is no real tissue dissection during the establishment of the endoscopic working channel. The discectomy and fusion procedure is then performed inside the 8-mm working channel with specialized instruments, which minimize trauma to the surrounding tissues.

It is more restrictive to insert a rigid and conformal cage device into intervertebral disc space through a small working channel for interbody fusion. Intraoperative nerve root and dural injury is possible and may cause serious sequela such as cerebrospinal fluid (CSF) leakage, paresthesia, or motor deficit. Proper cage sizing must be carefully considered as well. Previous case series reported a high risk of cage migration with rigid stand-alone percutaneous titanium cages in endoscope-assisted TLIF [3]. Other series have adopted expandable cages, for example, the expandable mesh cage (OptiMesh cage, Spineology), the titanium expandable cage (Opticage, Interventional Spine Inc., Irvine, CA, USA), or the B-twin expandable spinal spacer, to achieve interbody fusion. Much less complications of cage migration were reported using an expandable cage. In addition to migration, cage subsidence and pseudo-arthrodesis have been documented using expandable cages. Since posterolateral fusion is less feasible, solid interbody fusion is necessary for awake TLIF. Bone morphogenetic protein (BMP)-2 is another key to the success of solid interbody fusion. BMP-2 is one of the most potent growth factors to induce mesenchymal stem cell and osteoprogenitor cell differentiation into osteoblasts. Recombinant human bone morphogenetic protein (rhBMP)-2, a highly osteoinductive bone graft, is inserted before expandable cage to promote interbody arthrodesis in awake TLIF.

The percutaneous screw and rod fixation system is one of the hallmarks of minimally invasive spine surgery. It also plays an important role in awake TLIF. Before the interbody fusion is robust following awake TLIF, percutaneous screws and rods help to hold the spine in a fixed position and facilitate bone union. The percutaneous method of screw and rod insertion helps to minimize surgical trauma.

Local analgesia is achieved with the aid of Exparel^®. Exparel^® is a long-acting liposome injection of bupivacaine, which is indicated for administration to the surgical site for postsurgical analgesia. Twenty milliliters of Exparel^® is injected into the musculocutaneous tract of the percutaneous screws to achieve excellent pain control for a few days. It must be certain that Exparel^® is not injected into disc space. Additionally, Exparel^® is an amide-type local anesthetic which is metabolized by the liver and so should be used cautiously in patients with hepatic disease.