The osseous exposure of the TLIF often requires a complete, unilateral facetectomy; while some surgeons may prefer to leave a medial bridge of the lamina and articular process, we strive to maximize our decompression of the neural elements. This is begun by performing a hemilaminotomy and connecting this to a transverse osteotomy at the level of the pars interarticularis (Fig. 27.1b). The remainder of the superior articular process of the caudal vertebrae is removed to the level of the pedicle (Fig. 27.1c). The ligamentum flavum is resected and the lateral dural edge is exposed; this may be tailored to the degree of central stenosis. This should provide exposure of the axilla of the exiting nerve root; any retraction is rarely needed to access the disk (Fig. 27.1d). Bleeding from the epidural venous plexus is controlled with bipolar cautery and hemostatic agents. The annulus is incised, posterior osteophytes are removed, and a diskectomy is performed using curettes, rongeurs, and disk shavers. The trajectory of the diskectomy and the interbody graft is at a 45° angle to the disk space (as opposed to the directly ventral trajectory of the PLIF interbody graft) in order to achieve a graft placement that crosses the midline of the vertebral body (Fig. 27.1e). The end plates are prepared with a variety of instruments according to surgeon’s preference and an interbody graft is placed with fluoroscopic guidance. Interbody graft placement may vary by case: more anteriorly placed grafts provide increased lordosis in cases where deformity correction is prioritized, and more posteriorly positioned grafts provide increased foraminal decompression. Biomechanically, the TLIF interbody graft should cross the midline to avoid inducing a coronal imbalance, cover more than 20 % of the end plate surface [50], and avoid the central region where the end plate is structurally weakest [51]. Uni- or bilateral pedicle screw instrumentation, posterolateral fusion, hemostasis, and wound closure are performed in the usual manner (Fig. 27.1f). Off-label utilization of rhBMP-2 is also utilized by some surgeons in the interspace (inside or outside the allograft) or the posterolateral space, particularly in patients at high risk of pseudarthrosis.

Mini-open and tubular variations of TLIF are also favored by our group. Utilizing fluoroscopy or intraoperative navigation, a paramedian incision is planned 4 cm off the midline. A series of tubular dilators are used to create a transmuscular (Wiltse-type) working channel. Ideal docking position for a TLIF is over the ipsilateral pars interarticularis with an expandable (mini-open variant) or fixed 26 mm working tube. Neural element decompression and preparation of the interspace are performed in the same manner utilizing adapted instruments with a bayoneted shaft so as not to obstruct the field of view. Expandable dilators allow for a working space of 45–50 mm, so single-level pedicle screw instrumentation can then be placed under direct vision; otherwise percutaneous instrumentation is utilized. Given the increased radiation exposure inherent to mini-open TLIF procedures, a further alternative is to replace fluoroscopy with O-arm guidance, thus decreasing radiation exposure [52, 53] and potentially improving accuracy of pedicle screw insertion [54].