Transforaminal Lumbar Interbody Fusion (TLIF)

Indications

The primary objective of any interbody fusion is to stabilize the spine. Table 8.1 shows the indications for lumbar interbody fusions. Table 8.2 presents the relative contraindications for the procedure.

Technique

The patient is first placed under general anesthesia, intubated, and then positioned prone on a radiolucent surgical table ( Fig. 8.1 ). Intravenous antibiotics should be administered prior to performing the skin incision. The surgeon must avoid placing the patient in a flat-back or kyphotic position before performing the TLIF, because the patient may be fused into that nonphysiologic position. Positioning the patient in optional lordosis is accomplished by providing maximal hip extension during positioning. Pressure points are appropriately padded, and the surgical field is prepared and draped in a sterile fashion. Biplanar fluoroscopy may then be used to localize the indexed level accurately. A vertical incision (5–7 cm) is performed and the muscles and soft tissues are retracted laterally to expose the spinous processes, lamina, facet joints, and transverse process ( Fig. 8.2 ). A laminectomy, facetectomy, or both are performed, depending on the clinical presentation. Minimally, a unilateral laminotomy and partial facetectomy are performed on the more symptomatic side. The exiting nerve root is identified and carefully preserved.

Once the neural elements are adequately decompressed, pedicle screws are placed in a standard fashion. The disk space is then identified and a standard diskectomy is performed. Adequate removal of the cartilaginous endplate is necessary; however, preservation of the bony endplates is required to prevent graft subsidence. With the use of a combination of interspace wedges and serial distraction of the pedicle screws, an increase in disk height is accomplished and maintained ( Fig. 8.3 ).

An interbody graft of the adequate size is prepared and packed with autograft or other fusion substrate. A nerve retractor is placed against the traversing nerve root to protect it during graft placement while always trying to minimize the retraction of the thecal sac. The first cage is impacted until it is just under the posterior edge of the vertebral body. It is important to begin moving the cage medially just as it sinks within the disk space. This allows the mesh to be placed across the vertebral body, making room for the second cage on the ipsilateral side ( Figs. 8.4 and 8.5 ).

After the interbody construct is placed, the pedicle screws are attached to and compressed on the rod, thereby restoring lumbar lordosis while maintaining the restored disk height. This restores lordosis and compresses the interbody graft to prevent graft migration and facilitate fusion.

A multilayer closure is performed using absorbable sutures in the lumbodorsal fascia and subdermis. Staples or nylon sutures are used to close the skin.

Limitations

As opposed to other types of interbody fusion, open TLIF is versatile. The main limitations of the procedure are on the number of levels applied and the greater risk of failure in the osteoporotic spine. Although a TLIF may be applied at all levels of the lumbar spine, it is generally indicated for one to three levels. At more than this number of levels, the time to perform such a procedure may be excessive. Moreover, care must be taken when performing TLIF at the upper lumbar levels. As one approaches the conus medullaris, there is less retraction of the thecal sac (i.e., dura), thus limiting TLIF at L1-2 and potentially L2-3.

The chance of endplate damage is greater in the osteoporotic spine. If this occurs during endplate preparation or cage placement, subsidence may occur and hence construct failure. If TLIF is used in the setting of osteoporosis, significant care must be utilized during endplate preparation and implant placement.