Transforaminal and Posterior Lumbar Interbody Fusion

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Transforaminal and Posterior Lumbar Interbody Fusion

Todd J. Albert and Peter M. Fleischut

Description

The goal of transforaminal lumbar interfusion (TLIF) is to safely access the interbody area without significant dural retraction. This allows one to effectively fuse both anteriorly and posteriorly through a posterior only approach. Posterior lumbar interbody fusion (PLIF) achieves similar goals through a bilateral, more medial approach. PLIF requires more dural retraction than TLIF, which is essentially a far lateral PLIF.

Key Principles

Anterior interbody support facilitates deformity correction, increased fusion rate, and disk space distraction, as well as at least unilateral if not bilateral direct foraminal decompression and traversing nerve root decompression.

Expectations

An improved fusion rate compared with a posterior lateral intertransverse process fusion. A PLIF or TLIF at the end of a long fusion decreases the risk pseudarthrosis due to improved anterior column support.

Indications

Isthmic spondylolisthesis (grades 1 to 4), junctional degeneration adjacent to a fusion mass, degenerative disk disease, recurrent disk herniation with significant back pain, the terminal end of long fusion requiring interbody fusion, short segment degenerative scoliosis, postlaminectomy spondylolisthesis.

Contraindications

Severe osteopenia, bleeding disorders, and active infection.

Special Considerations

Preoperative imaging studies including anterior/posterior and flexion/extension lumbosacral spine radiographs are necessary. Additionally, magnetic resonance imaging (MRI) or computed tomography (CT) myelography is necessary for understanding the anatomy and planning the surgical approach (left versus right or unilateral exposures). At times for discogenic back pain, diskography, though controversial, can be useful in determining the level of the pain generator.

Special Instructions, Position, and Anesthesia

The patient should be placed prone with the abdomen decompressed. An Andrews frame is generally used for L4-sacrum exposures. For longer approaches such as adult deformity, a Jackson table is used. Triggered electromyography (EMG) recording can be used to test the accuracy of pedicle screw placement. Free-run EMG recording can be used during insertion of transforaminal lumbar interbody fusion grafts or cages to ensure that undue traction or injury is avoided to the exiting or traversing nerve roots.

Tips, Pearls, and Lessons Learned

Complete radical diskectomy requires use of multiple interbody instruments including angled curettes and osteotomes (straight and angled and double-angled chondrotomes to scrape the end plates and remove the maximum amount of disk material from one side to the other if a unilateral approach is used [TLIF]). Special intervertebral distraction devices are helpful. In the TLIF procedure, the inferior articular process of the vertebra above is taken off to gain access to the transforaminal area and the superior articular process of the vertebra below is skeletonized to maximize the transforaminal opening. Bullet distractors are an optimal distraction instrument to obtain maximum annulotaxis. A large lamina spreader placed between the spinous processes also assists in disk space distraction, though this method risks a kyphosing force on the disk space. This technique of overdistraction is helpful when placing a banana-shaped cage through a unilateral TLIF approach and is often not necessary in a bilateral PLIF cage approach.

For interbody grafting, various approaches can be applied. Carbon fiber, metallic, or poly-ether-ether-ketone (PEEK) type cages in rectangular, bulleted, or banana shapes can be used. Maximum lordosization is achieved by placing the cage, especially a banana-shaped cage, in the anterior part of the disk space. Finally, with the anterior interbody device anteriorly situated, a compressive force is placed across the pedicle screw instrumentation to enhance lordotic alignment. Hemostasis is obtained by using bipolar cautery in the area just medial to the pedicle and in the axilla of the exiting nerve root where the majority of work is to be done.

Difficulties Encountered

Significant bleeding can occur during these procedures, and there may at times be difficulty with interspace distraction. In cases with excessive bleeding, or with difficulty with interspace distraction, a non-structural graft may be used.

Key Procedural Steps

For a TLIF procedure, a straight osteotome is used to create a laminotomy defect, removing a portion of the inferior lamina of the vertebra above and transecting the pars to remove the entire inferior articular process. In a PLIF procedure, the pars is preserved and a partial facetectomy is performed to allow for adequate clearance for bilateral cage or graft placement (Fig. 38.1).
For a TLIF procedure the superior articular process of the vertebra below is removed with the straight osteotome or large rongeur and the pedicle skeletonized with a 4-mm Kerrison rongeur. For a PLIF procedure the lateral pars is protected and the medial border of the pedicles of the caudal vertebral body are exposed. Bipolar cautery is used again to maximally cauterize the epidural veins if necessary just medial to the pedicle of the vertebra below. Minimal retraction is performed at the shoulder of the traversing nerve root to give access to the annulus or transforaminal area in the TLIF procedure. With a PLIF, neural retraction is performed to the degree necessary to allow cage or graft placement (Fig. 38.2).
A sharp annulotomy is created and a radical diskectomy is performed with curettes (Fig. 38.3). Interspace distractors are used in a serial manner (6 to 12 mm) to obtain adequate disk space distraction between curettaging of the disk space. The end plate may be punctured in several regions to create bleeding for fusion enhancement. The interbody cage or graft is then packed with a filler and placed into the anterior disk space under either fluoroscopy or direct vision (Fig. 38.4). Autogenous bone is then packed laterally and posterior to the cage or graft. Pedicle screws, previously placed or placed at this point, are then compressed and are fixed with longitudinal members. An intertransverse fusion is also often performed.