TLIF/PLIF MIS Option

Philip K. Louie

Dustin H. Massel

Benjamin C. Mayo

Grant D. Shifflet

William W. Long

Krishna Modi

Kern Singh

REBUTTAL ▪ The Case against MIS TLIF/PLLIF

Todd J. Albert

TLIF/PLIF MIS OPTION INTRODUCTION

Brief Description of Standard Open Technique

Transforaminal lumbar interbody fusion (TLIF) involves a complete facetectomy (superior articular process), which provides more lateral disk space exposure and minimizes the need for neural retraction.¹,² The posterior lumbar interbody fusion (PLIF) utilizes a more medial approach to the disk space, spares a portion of the facet joint (superior articular process) and may require retraction of neural elements to safely perform the diskectomy and interbody fusion. A standard posterior approach to the lumbar spine is performed. Adequate exposure of the transverse process (TP) tips enables performance of an intertransverse fusion if the surgeon elects to do so. Once the pedicle entry point is established at the junction of the TP and the superior articular process, polyaxial pedicle screws are placed bilaterally. Rods and screws or a spinous process distraction is utilized to perform a posterior distraction maneuver, opening the posterior aspect of the disk space. An annulotomy is performed using a scalpel, creating a window to the disk space. In order to perform an adequate diskectomy, the disk space must be prepared using a combination of dilators, shavers, curettes, and rongeurs. Various sizes of interbody grafts are trialed until a proper fitting graft can be placed. The entire disk space should be tightly packed with morselized bone graft material. Compression is applied to the pedicle screw construct while the set screws are fully tightened.

INDICATIONS

Indications for minimally invasive surgery (MIS) TLIF/PLIF are similar to the indications for the open procedure. Common indications include mechanical low back pain due to spondylolisthesis, low-grade spondylolisthesis (grade I or II), and radiculopathy refractory to conservative therapies.³, ⁴, ⁵, ⁶ Spinal instability and symptomatic radiculopathy from degenerative disk disease, recurrent disk herniation, spinal trauma, pseudarthrosis, synovial cysts, or postlaminectomy kyphotic instability may also benefit from interbody fixation.⁷, ⁸, ⁹, ¹⁰

CONTRAINDICATIONS

There are few absolute contraindications to perform an MIS TLIF/PLIF.³,⁸,¹¹, ¹², ¹³ A PLIF is contraindicated above the level of L2 due to the narrow interpedicular distance, proximity to the conus medullaris, and narrow spinal canal. A TLIF can be performed at this level if absolutely necessary, as this approach minimizes retraction of the thecal sac, consequently decreasing the risk of injury to the conus. However, damage to the conus medullaris remains a great concern for both the PLIF and TLIF. Some relative contraindications include high-grade spondylolisthesis (grade III or IV), metastatic disease to the spine, acute spine
fractures, scar tissue from prior spine surgery, and multilevel spinal disease (greater than two levels). Primary pathology that does not originate from the spine including severe osteoporosis, systemic infections, pregnancy or obesity may also represent relative contraindications to this procedure.

POTENTIAL/THEORETICAL PROBLEMS WITH CURRENT OPEN TECHNIQUE

Iatrogenic soft tissue damage, often caused by tissue manipulation and prolonged retraction, is a common complication of an open procedure.⁴,⁸,¹⁴ Creatine phosphokinase MM isoenzyme is a direct marker for muscle injury. Increased levels of this isoenzyme have been found during the immediate postoperative period following an open TLIF.⁶ Persistent pathologic changes in the paraspinal muscles have also been observed in patients following open lumbar surgeries.¹⁵ Patients who undergo open lumbar fusion procedures may have significantly weaker trunk strength than patients who undergo a less invasive open procedure such as a lumbar diskectomy.¹⁶ Innervation to several paraspinal muscles can be disrupted during an open procedure, resulting in a loss of muscular support.⁸,¹⁷ Open TLIF/PLIF procedures are also associated with longer operative times and increased perioperative blood loss.⁶,¹⁸, ¹⁹, ²⁰

DESCRIPTION OF TECHNIQUE

Once access to the disk space has been established, the remaining steps of MIS PLIF and MIS TLIF are identical. The PLIF approach is more medial in orientation and leaves a portion of the facet in place, whereas the TLIF approach is more lateral and a complete facetectomy is performed.

Relevant Anatomy

Musculature of the posterior lumbar spine can be described in three layers:

Superficial: latissimus dorsi, thoracolumbar fascia
Intermediate: serratus posterior, erector spinae muscles (iliocostalis, longissimus, spinalis)
Deep: multifidus, rotator muscles

Paraspinal (Wiltse) approach⁷ involves the muscular plane, which includes multifidus and longissimus portions of the sacrospinalis muscle. The natural posterior tension band, created by the interspinous and supraspinous ligaments, is spared with this approach. The posterior attachments of the contralateral paraspinous musculature are preserved.²⁰

Anatomic Working Zone

The structures bordering the predominant working zone include inferiorly the caudal vertebra pedicle just below the disk of interest, medially the traversing nerve root and the thecal sac, and superiorly the residual pars interarticularis, exiting nerve root, and cephalad vertebra above the disk of interest. Lumbar pedicles are oriented with medial angulation from posterior to anterior in the transverse plane. At L1, they are 10 to 15 degrees angulated, while at L5, they are approximately 30 degrees angulated.¹³

Preoperative Planning

Radiographs are generally the first image modality obtained to evaluate low back pain. Anteroposterior (AP) and lateral views can aid in determining sagittal alignment, disk space height, and the presence of osteophytes. Flexion/extension views are often obtained to detect lumbar instability. To further evaluate for stenosis, magnetic resonance imaging (MRI) is recommended for all patients unless a contraindication exists. If MRI is contraindicated, computed tomography (CT) or CT myelogram is used. The CT myelogram can aid in identifying structural pathology and spatial associations between bone and soft tissue.

Figure 24.1 The patient is placed on a Jackson table in prone position. To avoid pressure on the brachial plexus, a chest pad is placed just below the axilla. The abdomen is positioned to hang freely to prevent venous congestion. Gel pads are placed under the patella. Hip and thigh pads are positioned just inferior to the anterior superior iliac spine.

TECHNIQUE STEP BY STEP

Patient Positioning

The patient is placed in prone position on a Jackson radiolucent table (Fig. 24.1). C-arm (fluoroscopy) and monitor are set up on the opposite side of the surgeon. AP/lateral views are obtained to assess C-arm positioning and proper visualization of spinal anatomy before prepping and draping.¹² The patient’s upper extremities are abducted with elbows flexed to 90 degrees. Padding is placed underneath the axilla, knees, chest, and anterior thigh to prevent positional compression neuropathies (e.g., brachial plexus palsy). Somatosensory-evoked potentials (SSEP) and electromyography (EMG) neuromonitoring tools are positioned.

Surgical Approach

AP fluoroscopy is utilized to identify the sacral pedicle teardrop in order to determine the initial approach. A 22G needle is inserted into the skin at the level of the pathologic disk space on the side with prominent radicular symptoms. A 2-to-3-cm incision is made, centered on this point, approximately 4 to 5 cm lateral to midline.

Pedicle Screw Cannulation

Using a Jamshidi needle, the fascia is penetrated extending deep to the junction between the superior articular facet joint and TP. The needle is placed at the 10-o’clock or 2-o’clock position (12-o’clock is midline and cephalad to the junction) (Fig. 24.2). The needle is advanced
15 to 20 mm, using 5-mm increments. A Kirschner wire (K-wire) is inserted an additional 10 to 15 mm under AP fluoroscopy, taking care to ensure the tip does not penetrate the medial wall of the pedicle. Once the K-wire tip is positioned, a lateral fluoroscopic view is obtained to confirm the K-wire has traversed the pedicle-vertebral body junction. If the K-wire has not crossed the posterior wall of the vertebral body or if it has extended past the medial wall of the pedicle, the Jamshidi needle is repositioned laterally. This procedure is repeated at the pedicle of the inferior level. The K-wires are gently bent outward at the incision site.

Figure 24.2 Intraoperative anteroposterior fluoroscopy demonstrating the correct Jamshidi needle starting point on the right pedicle at the 2-o’clock position.

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