42 MIS-TLIF with Total Navigation and Expandable Interbody Cages
Summary
Keywords: interbody fusion spinal fusion pseudoarthrosis spondylolisthesis tubular surgery expandable cage
42.1 Introduction
The transforaminal lumbar interbody fusion (TLIF) surgical technique is a versatile technique to treat different lumbar disorders such as spondylolisthesis, stenosis, and instability.1 The TLIF technique relies on a single posterior approach to achieve a 360-degree stabilization and spinal canal and neural foramina decompression. Also, it can reduce listhesis, restoring and maintaining lumbar lordosis especially today with the availability of expandable cages. The TLIF far-lateral surgical corridor is ideal to avoid dural and nerve root manipulation/retraction, which decreases the incidence of the intraoperative durotomy and postoperative radiculitis in comparison with PLIF.2
The minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) is a modification of the original technique, performed through a paramedian transmuscular corridor.3 The MIS-TLIF approach decreases collateral muscle damage and detachment, preserving ligaments and facet joint integrity most of the times.4 In addition, MIS-TLIF has shown to decrease the estimated blood loss (EBL), hospital stay, and postoperative pain when compared to conventional approaches, while maintaining similar clinical and radiographical outcomes.5,6,7
Minimally invasive techniques depend on an indirect localization of anatomical structures using X-rays, fluoroscopy, or intraoperative computed tomography (CT) (iCT) scanners. However, reducing radiation exposure is still a challenge. Some authors have reported that there is significantly longer patient fluoroscopic exposure in the MIS-TLIF group compared with the open TLIF.8,9 More recently, we have been able to adapt the MIS-TLIF technique using a portable iCT scanner, Airo (Brainlab AG, Feldkirchen, Germany), combined with state-of-the-art computer navigation, not only for navigated instrumentation but also for intraoperative planning throughout the procedure, inserting the cage and eliminating the need for fluoroscopy. Moreover, our group published this modification in a “total navigation” modality, which can reduce staff radiation exposure to 0 by navigation/augmented reality, real time over iCT obtained images that can be acquired while the surgical staff is protected or outside the operating room (OR).10 With the iCT-CAS and image-guided navigation, real-time and virtual intraoperative imaging of screws and their planned trajectory is feasible. This helps surgeon’s orientation during instrumentation and also helps to predict cage placement and size.10
The purpose of this chapter is to describe our latest experience in navigated MIS-TLIF procedure. More details about the alternatives on how to perform an MIS-TLIF procedure will be included in Chapter 43.
42.2 Patient Selection: Indications and Contraindications
a)Indications:
1.Central stenosis, with lateral recess and foraminal stenosis.
2.Radicular symptoms due to foraminal or lateral recess radicular compression.
3.Primary degenerative disc disease (DDD) causing discogenic low back pain for 12 to 16 weeks that do not respond to conservative therapy.
4.Segmental instability causing low back pain with or without nerve root compression:
a)Idiopathic or traumatic grade I or II spondylolisthesis.
b)De novo or iatrogenic biomechanical instability, including pseudoarthrosis.
c)Bilateral facet joint cysts with unilateral nerve compression.
b)Relative contraindications:
1.Severe deformity and/or severe sagittal and coronal imbalance of the lumbar spine.
2.Multilevel disease (more than two).
3.Systemic and local infection.
4.Tumors—either local or metastatic lesions.
5.Severe osteoporosis.
6.Previous surgery with extensive epidural scarring on magnetic resonance imaging (MRI).
7.Grade III or IV spondylolisthesis.
8.Acute spinal end-plate fracture.s
42.3 Preoperative Planning
a)Patient’s previous history and physical examination are key.
b)Diagnostic testing and imaging studies: Imaging information (e.g., MRI, CT scan, and flexion/extension X-rays) should be sufficient to determine the appropriate level or levels requiring surgery, as well as the characteristics of the pathology (e.g., calcified disc, migrated disc, synovial joint cyst, etc.).
Recommended routine preoperative investigations are:
a)Full body standing anteroposterior (AP) and lateral X-rays including the pelvis and femoral heads are mandatory.
b)For all our patients, we measure: SVA, PI-LL, Cobb angle, and C2 plum line.
c)Flexion/extension X-rays are extremely useful in cases of spondylolisthesis. They provide basic information about important parameters concerning sagittal balance and coronal balance, which are clinical outcomes prognostic factors.
d)MRI provides accurate information regarding the perineural structures, for example, disc, muscle, scars, fibrotic tissue, etc.
e)CT scans are especially important in those pathologies where either bone structures or calcification of soft tissue is expected. For example, bony foraminal spurs, stenotic calcified foramens, calcified discs, and calcified facet joint cysts. Also, they are useful to predict the pedicle dimensions.
42.4 Patient Positioning
a)After endotracheal general anesthesia, all pertinent monitoring extensions, such as the intubation tube, Bovie, and suction, are positioned through the gantry of the Airo (Fig. 42.1a–c).
b)The patient is taped down and fixed to the table to ensure immobilization of skin and soft tissue especially in overweight patients. This helps to prevent shift during intraoperative navigation (Fig. 42.1a–c).
c)The posterior midline and iliac crests are marked, and then the patient is scrubbed and draped in regular fashion (Fig. 42.1d–e).
d)The patient reference array is fixed to the left iliac crest using two Steinmann pins. Two sterile half sheets are used to cover the surgical site, leaving exposed only the reference array (Fig. 42.1d–f).
e)First scan: All the staff leave the OR, including the radiology technician, who brings the Airo touch screen outside the door to control the scan. Therefore, not wearing lead aprons is possible for the surgical staff (Fig. 42.1g).
f)When the scan is complete, the images are automatically transferred to the Brainlab Curve navigation system (Brainlab Curve, Brainlab AG, Feldkirchen, Germany) (Fig. 42.1h).
g)After registration, data is transferred to the navigation unit. Confirmation of the anatomical landmarks to confirm accuracy is performed and the trajectory to reach the pedicles is identified and marked over the skin/ioban using a marking pen (Fig. 42.1i).
Fig. 42.1 (a) Patient is positioned prone and all the bony prominences are covered and padded. (b) Patient is taped down to the frame to prevent shifting. (c) The final position and orientation of the gantry and the table. (d) Steinmann pins are inserted into the superior iliac crest ideally deep enough to reach but not perforate the ventral cortex of the iliac crest. (e) Final position of the reference array (aiming medially and inferiorly. Preferably, contralateral to the side of the facetectomy/cage insertion site. (f) The patient is covered with two sterile half sheets and the technician makes sure the area to scan is visible. (g) The technician leaves the operating room (OR) and the patient is hold on apnea while everyone leaves the room and the scan is obtained. (h) The incision is then navigated and planned. (i) The tools to be used are then registered and calibrated (Video 42.1).
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