Procedure 33 Transforaminal Lumbar Interbody Fusion
Indications
Spondylolisthesis (particularly isthmic and degenerative etiology)
Symptomatic degenerative disk disease
Radiculopathy caused by foraminal stenosis from loss of disk height
Augmentation of distal end of long posterior scoliosis fusion constructs
Segmental coronal collapse and tilt with unilateral radiculopathy
Examination/Imaging
Pertinent preoperative history and physical are essential to the diagnosis and surgical decision making. The most symptomatic side (right versus left) is selected for the transforaminal lumbar interbody fusion (TLIF) approach.
Plain radiographs are obtained to assess for listhesis, other deformities, osteopenia, and spina bifida occulta. Dynamic studies should be performed to rule out dynamic instability. Figure 33-1, A to C shows anteroposterior (AP) and flexion extension films demonstrating a grade I degenerative spondylolisthesis at L4-5 in a 60-year-old male who had undergone laminoforaminotomy and facet cyst excision years earlier and then presented with recurrent leg and back pain.
Magnetic resonance imaging (MRI) is done to identify degenerated intervertebral disks and possible compression of neuronal elements. Figure 33-2 shows T2-weighted sagittal MRI in the same patient, showing facet cyst and severe stenosis at the level of L4-5 spondylolisthesis.
Surgical Anatomy
It is important to expose the ipsilateral spinous process, lamina, facet, and transverse process. The working zone for the TLIF approach is bounded medially by the traversing nerve root and thecal sac, superiorly by the exiting nerve root, and inferiorly by the pedicle of the vertebra below the disk space. Note that the exiting root hugs the undersurface of the superior pedicle, allowing for a safe work zone.
Figure 33-3 shows lateral (A) and cross-sectional (B) schematics demonstrating working zone for TLIF and the relationship of exiting and traversing roots to the disk space.
Positioning
The patient is prone with the abdomen free of any compression to reduce venous congestion.
The thigh is neutral or slightly extended.
Check the final positioning on the operating room table with a plain radiograph or fluoroscopy.
Positioning Pitfalls
• The hip-flexed position will open the posterior interbody space and may improve access to the disk; however, this position reduces lumbar lordosis and can lead to fixed sagittal imbalance. Therefore the authors do not recommend it.
• High-grade isthmic spondylolisthesis or significant kyphosis at the level of the slip may necessitate a bilateral PLIF rather than a TLIF, if a posterior interbody approach is being taken.
Portals/Exposures
The standard midline incision with subperiosteal exposure of the pertinent posterior osseous elements may be performed.
Alternatively, the surgical exposure may be achieved by the Wiltse paraspinal approach.
Some minimally invasive approaches (e.g., with tubular retractors) use a muscle-splitting technique.
Procedure
Step 1
A subperiosteal exposure is performed. The facet complex corresponding to the disk space being fused is exposed in its entirety. The transverse process and pars interarticularis of the caudal level are also exposed. The pars and transverse process of the rostral level are exposed, while making sure the supraadjacent facet capsule is not violated.
The inferior facet is removed from the cephalad level using a 
osteotome. This should be done by making a transverse cut in the pars interarticularis just above the lower vertebrae’s pedicle. Although this usually corresponds to the top of the superior articular facet of the lower vertebrae, one must be cautious while doing this in the degenerative spine, because one may be pushed upward by the osteophyte and inadvertently make the cut higher along the pars, which could injure the exiting nerve root. The authors confirm the position on fluoroscopy before making the cut. Figure 33-4 is an intraoperative fluoroscopic image showing the position of the osteotome at the level of the top of the lower segment’s superior articular facet. This corresponds to the disk space and is well below the superior segment’s pedicle.
