53 Minimally Invasive Transforaminal Lumbar Interbody Fusion (MIS TLIF)

Michael Y. Wang

I. Key Points

– Minimally invasive transformational lumbar interbody fusion (MIS TLIF) can be utilized to achieve lumbar spinal decompression, fixation, and fusion.

– The intent behind this approach, which is still unproven, is to reduce soft-tissue injury, blood loss, recovery time, and length of hospital stay associated with open TLIF.

– It is important to recognize the anatomic landmarks at the interpedicular space, referred to as a Kambin triangle: medial (traversing root), lateral (exiting root), and base (inferior pedicle)

II. Indications

Harms first described the transforaminal lumbar interbody fusion (TLIF) technique for circumferential fusion in 1982 using an interbody spacer and a supplemental pedicle screw construct.¹ This procedure was a departure from the traditional posterior lumbar interbody fusion (PLIF) in that the TLIF required only a unilateral facetectomy and a single interbody cage. TLIF then became popular due to the lower rates of nerve root injury given the reduced surgical manipulation of neural elements, and it was also found to be effective for revision surgery because the midline dural sac did not have to be exposed.

A minimally invasive approach for accomplishing the TLIF procedure was subsequently developed.² This technique utilized the advantages of expandable working tubes and percutaneous pedicle screw technology to reduce the soft-tissue injury that has been documented to result from open surgery.³ Although no class I evidence exists to demonstrate the superiority of MIS TLIF over open TLIF, comparative studies suggest a trend toward reduced postoperative pain, hospital length of stay, infection rates, and blood loss.⁴ MIS TLIF can generally be applied in all situations where an open TLIF can be used.

– Single-or two-level degenerative disc disease with correlative clinical symptoms

– Spondylolisthesis less than Meyerding grade III

– The patient is positioned prone on a Jackson operating room table, which offers several advantages. The location of the incision is targeted under fluoroscopy, and two paramedian skin incisions are made between 3 and 4 cm lateral to the midline. Sharp incision of the fascia allows for blunt finger dissection between the longissimus and multifidus muscles along a modified Wiltse plane (Fig. 53.1).⁵ This not only minimizes trauma to muscular tissues but also minimizes intraoperative bleeding and creates a natural plane that allows for efficient maintenance of the trajectory of the retractors. The approach, if unilateral, is taken from the side where decompression is most necessary.

– Tubular dilator retractors are then placed through this plane and the level confirmed with fluoroscopy. Monopolar cautery is then used to clear any muscle tissue over the facet joint, making sure to expose the lateral aspect of the joint.

– Once the surgeon has confirmed the location of the pars and the lower pedicle, a quarter-inch osteotome or high-speed burr is used to remove the facet joint. Either a partial or complete facetectomy can be performed, with greater bone removal for cases with more medial compression. Care must be taken not to drill into the pedicle. After facet removal the lateral aspect of the ligamentum flavum is visualized. This is resected until the lateral thecal sac is seen (Fig. 53.2). Autograft bone is saved for later grafting purposes.

– Further decompression can then be performed as needed, with removal of ipsilateral ligamentum flavum, decompression under the pars, or contralateral decompression. This is best achieved by angling the retractors more medially. Alternatively, bilateral decompression can be accomplished through dual ports placed on each side.

– After palpation of the caudal pedicle and confirmation of the location of the exiting and traversing nerve roots, the annulus is incised, followed by aggressive intervertebral disc removal and end plate preparation, as with the open technique. This is followed by intervertebral cage placement.

– The neural elements are reinspected. If a posterolateral fusion is desired, the dura is covered with Gelfoam (Pfizer, New York) and the lateral facets and transverse processes are decorticated with a drill. This is followed by bone graft application.

– Supplemental pedicle screw placement can then be accomplished either using a mini-open technique (through the re-tractor with visualization) or percutaneously before or after the decompression. For the mini-open method, the screw placement is very similar to open TLIF. Various methods are used for percutaneous targeting, including (1) AP only, (2) the owl’seye en face approach, (3) biplanar fluoroscopy, and (4) image guidance. All percutaneous methods involve placement of a joshed needle into the pedicle, followed by the use of a cannulated awl and tap to create a screw entry tract. Finally, screw placement and rod tunneling are used to connect the construct components.

– A drain is not typically used.

Fig. 53.1 Axial magnetic resonance image (MRI) showing the modified Wiltse plane between the longissimus and multifidus muscles. High MRI signal can be seen along this plane between the muscles, giving direct access to the facet joints.

Fig. 53.2 A Kambin triangle.

– Screw misplacement is most commonly the result of poor targeting technique. Thus, close familiarity with one technique for ensuring that the pedicle is not breached is essential. The anteroposterior (AP) targeting techniques are excellent for preventing neural injuries.

– Self-distracting cages, usually with a “bulleted” nose, will allow the placement of larger interbody cages, as it is difficult to use pedicle screw manipulation of a laminar spreader to open the disc space in MIS surgery.

Related posts:

Tumors of the Spine Thoracic Pedicle Technique Spondyloarthropathies Pedicle Subtraction Osteotomy/Smith Peterson Osteotomy Physical Examination Retroperitoneal Approaches to the Thoracolumbar Spine

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