Minimally Invasive Transforaminal Lumbar Interbody Fusion

Illustrative Case

The patient is a 67-year-old male presenting with low back and right buttock pain radiating to the lateral right leg that has been present for more than 2 years but more problematic in the last 6 months. He reports low back pain as well as right leg pain that radiates down the posterior thigh and calf to the top of the right foot. The symptoms are worsened with standing, walking, and lying down and improved with sitting. The patient has failed extensive conservative management including physical therapy and multiple epidural steroid injections. Radiographs of anteroposterior (AP) view (Figure 23-1A) and lateral view (Figure 23-1B) demonstrate L4-5 spondylolisthesis and disk height loss. MRI of the lumbar spine sagittal view (Figure 23-1C) and axial T2 view (Figure 23-1D) shows the stenosis of the central and lateral recesses at L4-5.

Figure 23-1 ▪ A, Radiograph anteroposterior view lumbar spine. B, Radiograph lateral view lumbar spine. C, MRI lumbar spine T2 sagittal view. D, MRI T2 axial view of L4-5.

Figure 23-1 ▪ (continued)

Radiologic Assessment

Standing radiographs lumbar spine AP and lateral views. Evaluate degree of spondylolisthesis and determine the type of spondylolisthesis (degenerative vs pars defect). Determine disk height and segmental and global sagittal alignment. Rule out significant coronal plane malalignment (lateral listhesis or scoliosis). Assess pedicle diameter on AP view. Determine presence of congenital stenosis affecting multiple areas. Optional flexion and extension views to assess degree of instability.
MRI lumbar spine if possible (CT myelogram [CTM] if unable to get MRI). Assess location of stenosis—central, lateral recess, or foraminal. Determine disk height, sagittal plane alignment, and pedicle diameter and length. Determine decompression strategy—amount of lamina and facet that need to be removed. Look for possible aberrant neuroanatomy (conjoined nerve root).
Ensure consistent vertebral level labeling between radiographs and MRI (or CTM).

Positioning

Prone position with hip and chest padding with free abdomen (to reduce venous congestion and encourage lordosis)
Radiolucent table as above
Wide draping to allow significant medial lateral trajectory of the pedicle screw and retractor tubes
Ensure posterior iliac crest is prepped and draped if harvesting autograft.

Anesthesia/Neuromonitoring Concerns

Typically somatosensory evoked potential/motor evoked potential is not used, but some surgeons use triggered electromyography for additional verification of the safety of percutaneously placed instrumentation.
Localize skin incisions with fluoroscopy on AP view at each vertebral level (Figure 23-2A, B). The skin incision should be about 2 to 3 cm lateral to the center of the pedicle depending on the obliqueness of the pedicle and depth of the soft-tissue envelope. Use a K-wire to localize the skin incision. Typically, this is on the lateral part of the transverse process. A mark is made for each pedicle and the surgeon can draw lines to connect the marks as desired for skin incision.

Figure 23-2 ▪ A, Anteroposterior (AP) C-arm view of L4-5. B, AP C-arm view of L5-S1.
- The precise distance lateral to the pedicle may be localized using oblique fluoroscopic views to place the skin incision directly in line with the planned screw trajectory.
- Single incisions may be used for multiple adjacent levels, or separate percutaneous incisions may be utilized at the surgeon’s discretion. Typically using a single incision results in a more cosmetic incision.
Ensure same counting nomenclature is used between preoperative and intraoperative imaging for localization.

Approach

Skin incision with no. 10 blade, incise through dermis
Raytec ×2 to dab and help tension skin while using cauterizing skin bleeders
Cautery for hemostasis, continue dissection through subcutaneous tissue
Cerebellar retractor to elevate tissue until fascia visualized
Cautery through fascia. May undermine to release fascia proximally and distally in preparation for eventual rod placement.
Avoid digital dissection deep to fascia to feel lateral border of facet because this leads to unnecessary bleeding.

Instrumentation: K-Wire Placement

Make sure to use nitinol K-wires to reduce K-wire bending mishaps.
Start at cranial-most level and work caudal to keep K-wires organized.
At each level, both surgeon and assistant place Jamshidi needle(s) at starting points.
- Feel for transverse process, walk tip medially to facet joint, start with the bevel (arrow) aimed medially.
- Ideal starting point is at the 9 o’clock position for the left pedicle and 3 o’clock position for the right pedicle. Starting points at the cranial-most level may be adjusted slightly caudal in order to minimize interference between the screw head and adjacent intact facet capsule.

Hold Jamshidi needle with ring forceps while making fine adjustments under C-arm. Figure 23-3A shows the right Jamshidi needle already through the pedicle and the left needle in a good starting position.

Figure 23-3 ▪ A, Right Jamshidi needle already through the pedicle and the left needle is in a good starting position. B, Both needles just lateral to the medial pedicle wall on anteroposterior view. Change to lateral C-arm. C, Tips of the needles are in the vertebral body. Note that one of the central trocar is partially retracted to identify which of the needles on the C-arm corresponds to the right or left. D, Two K-wires at the anterior cortex of the vertebral body to reduce the chances of accidental K-wire removal. E, Left K-wire in the middle of the pedicle.

Only gold members can continue reading. Log In or Register to continue