We would like to acknowledge UCSF Medical Center and the Department of Neurosurgery for allowing us to pursue this endeavor.

All procedures and research activities were performed with institutional review board approval (CHR #17-21909).
1. Pre-operative Preparation
<ol>
	<li>Induce general anesthesia in the patient, and position the patient prone on the Jackson table with chest bolster and hip pads.</li>
	<li>Prep and drape the patient&#39;s back in the usual sterile fashion.</li>
</ol>
2. Surgical Procedure
<ol>
	<li>Make a small stab incision using a #15-blade over the PSIS contralateral to the side of the planned TLIF.</li>
	<li>Place a biopsy needle through the stab incision into the ilium to harvest bone marrow aspirate (Figure 1A). Drive the navigation reference frame into the PSIS in a trajectory that places the reference arc inferior and medial, thereby avoiding interference with the standard trajectory of an S1 pedicle screw (Figure 1B).</li>
	<li>Cover the wound with a sterile drape with the reference arc exposed and perform an intraoperative CT scan.</li>
	<li>Plan pedicle screw trajectories using the navigation system (Figure 1C); they are generally 3.5 cm lateral to the midline through a one-inch incision on each side for single level fusion (1.5 inch for two levels, and 1.75 inch for three levels).</li>
	<li>Use a navigated drill guide and 2-3 mm bit and high-speed drill to cannulate the pedicles and utilize K-wires to mark these trajectories.</li>
	<li>Place the cannulated pedicle screws with reduction towers over the k-wires on the side opposite the TLIF.</li>
	<li>Determine the trajectory along the disc space using the first tubular dilator which is oriented using the navigation system (Figure 1D). Place additional dilators followed by the TLIF retractor, which is connected to a self-retaining arm mounted to the bed.</li>
	<li>Confirm the retractor positioning via navigation.</li>
	<li>Perform the laminotomy, flavectomy, and facetectomy in standard fashion under the microscope.
	<ol>
		<li>Use a high-speed drill to perform the laminotomy and facetectomy; if just a laminotomy is desired, avoid drilling into the facet joint in order to preserve the structural integrity of the posterior column.</li>
		<li>Ensure that the lateral border of the laminotomy is the medial aspect of the facet joint, while the medial border of the laminotomy should be the medial edge of the lamina. Utilize a Woodson elevator to dissect the ligamentum flavum off the dura. Once this is achieved, use a 2 or 3 mm Kerrison rongeur to remove the ligamentum flavum. 
		NOTE: Navigation allows for maximal safe decompression without violation of the pedicle (Figure 1D, E).</li>
	</ol>
	</li>
	<li>If contralateral decompression is needed, angle the retractor across the midline and remove the underside of the contralateral lamina, ligamentum flavum, and hypertrophic facet capsule using a 2 or 3 mm Kerrison rongeur.</li>
	<li>Use the navigation again to identify the trajectory along the disc space to facilitate a safe and thorough discectomy.</li>
	<li>Prepare the disc space with shavers and distractors.</li>
	<li>Upon completing the discectomy, use intermittent fluoroscopy to visualize the degree of distraction required during the interbody cage trial placement to ensure preservation of the endplates (Figure 2A).</li>
	<li>Mix the allograft cellular bone matrix with the autologous bone marrow aspirate harvested at the beginning of the operation and carefully pack it into the disc space.</li>
	<li>Insert the interbody cage (polyetheretherketone [PEEK]), and confirm its position via lateral and anterio-posterior (AP) fluoroscopy (Figure 2B).</li>
	<li>Once TLIF has been completed, place the remaining pedicle screws.</li>
	<li>Carefully drive a pre-bent rod through the screw heads below the dorsal lumbar fascia. Use periodic fluoroscopy to confirm adequate rod length.</li>
	<li>Gently compress the rods to induce lordosis before securing them with locking set screws.</li>
	<li>Obtain a final fluoroscopy prior to closure.</li>
	<li>Close the thoracodorsal fascia with an 0 polyglactin 910 suture, close the subcutaneous tissue with 3-0 polyglactin 910, and approximate the skin edges with skin closure strips. Apply a water tight dressing.</li>
</ol>
3. Post-surgical Care
<ol>
	<li>Ambulate patients on postoperative day 1 with a soft lumbar brace, and obtain standing 36-inch X-rays prior to discharge (Figure 2C).</li>
	<li>Provide patients a patient-controlled analgesia (PCA) pump with morphine or hydromorphone overnight and ambulate on postoperative day 1.</li>
	<li>Transition patients to oral pain medications on the first day and discharge on postoperative day 2-3 with follow-up in 6 weeks.</li>
</ol>

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L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Minimally+invasive+pedicle+screw+fixation+utilizing+O-arm+fluoroscopy+with+computer-assisted+navigation:+Feasibility,+technique,+and+preliminary+results.">Minimally invasive pedicle screw fixation utilizing O-arm fluoroscopy with computer-assisted navigation: Feasibility, technique, and preliminary results.</a> Surg Neurol Int. 1, 44 (2010).</li><li>Van de Kelft, E., Costa, F., Vander Planken, D., Schils, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+prospective+multicenter+registry+on+the+accuracy+of+pedicle+screw+placement+in+the+thoracic,+lumbar,+and+sacral+levels+with+the+use+of+the+O-arm+imaging+system+and+StealthStation+Navigation.">A prospective multicenter registry on the accuracy of pedicle screw placement in the thoracic, lumbar, and sacral levels with the use of the O-arm imaging system and StealthStation Navigation.</a> Spine (Phila Pa 1976). 37 (25), E1580-E1587 (2012).</li><li>Kim, T. 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A systematic review.</a> Clin Orthop Relat Res. 472 (6), 1738-1748 (2014).</li><li>Villard, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Radiation+exposure+to+the+surgeon+and+the+patient+during+posterior+lumbar+spinal+instrumentation:+a+prospective+randomized+comparison+of+navigated+versus+non-navigated+freehand+techniques.">Radiation exposure to the surgeon and the patient during posterior lumbar spinal instrumentation: a prospective randomized comparison of navigated versus non-navigated freehand techniques.</a> Spine (Phila Pa 1976). 39 (13), 1004-1009 (2014).</li><li>Tabaraee, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intraoperative+cone+beam-computed+tomography+with+navigation+(O-ARM)+versus+conventional+fluoroscopy+(C-ARM):+a+cadaveric+study+comparing+accuracy,+efficiency,+and+safety+for+spinal+instrumentation.">Intraoperative cone beam-computed tomography with navigation (O-ARM) versus conventional fluoroscopy (C-ARM): a cadaveric study comparing accuracy, efficiency, and safety for spinal instrumentation.</a> Spine (Phila Pa 1976). 38 (22), 1953-1958 (2013).</li><li>Theologis, A. 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U., Tsiouris, A. J., Hartl, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Navigated+guide+tube+for+the+placement+of+mini-open+pedicle+screws+using+stereotactic+3D+navigation+without+the+use+of+K-wires:+technical+note.">Navigated guide tube for the placement of mini-open pedicle screws using stereotactic 3D navigation without the use of K-wires: technical note.</a> J Neurosurg Spine. 18 (2), 178-183 (2013).</li><li>Lian, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Total+3D+Airo(R)+Navigation+for+Minimally+Invasive+Transforaminal+Lumbar+Interbody+Fusion.">Total 3D Airo(R) Navigation for Minimally Invasive Transforaminal Lumbar Interbody Fusion.</a> Biomed Res Int. 2016, 5027340 (2016).</li><li>Navarro-Ramirez, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Total+Navigation+in+Spine+Surgery;+A+Concise+Guide+to+Eliminate+Fluoroscopy+Using+a+Portable+Intraoperative+Computed+Tomography+3-Dimensional+Navigation+System.">Total Navigation in Spine Surgery; A Concise Guide to Eliminate Fluoroscopy Using a Portable Intraoperative Computed Tomography 3-Dimensional Navigation System.</a> World Neurosurg. 100, 325-335 (2017).</li></ol>

Dr. Aaron Clark is a consultant for Nuvasive. Dr. Pekmezci, Safaee, and Oh have nothing to disclose.

There are several critical steps to the procedure described. The first critical step is the process of registration. The reference arc must be placed in solid bone and should be oriented appropriately to avoid interfering with the S1 pedicle screw placement if needed. The second critical step is maintaining accuracy of the navigation after an intraoperative CT scan is performed, which can be done by identifying normal anatomic structures and confirming the correct positioning. The accuracy should be periodically verified. Perhaps one of the limitations of the described technique is that the navigation can be inadvertently altered in the middle of an operation. Registration is derived from a fixed patient position on the operating table. As a result, any translational movement of the patient or the reference frame itself can dramatically influence the accuracy of navigation. Great caution must particularly be taken when applying any downward forces (such as during the placement of pedicle screws)20. Nevertheless, if there are any concerns regarding accuracy, the surgeon must not hesitate to repeat the registration to ensure high fidelity of the navigation.
Another critical step is the preparation of the disc endplates for interbody cage placement, as the endplates must not be violated, which can result in cage subsidence. The rates of PEEK cage subsidence in MIS-TLIF can be as high as 15%21, thus optimizing the cage fit can dramatically reduce the risk of migration, subsidence, and collapse; the endplate preservation is critical to achieving this goal22,23. Intermittent fluoroscopy can be helpful at this point to visualize the amount of distraction and end plate preservation. Final fluoroscopy can also be performed to confirm satisfactory cage positioning and placement24. In that manner, fluoroscopy remains a critical tool for this technique, particularly during discectomy, distraction, and cage placement. While image-guidance navigation allows for pedicle screw placement, intermittent fluoroscopy provides a &#34;real-time&#34; view to evaluate endplate preservation during discectomy and confirm the appropriate cage trajectory and final placement.
Apart from navigation registration errors, another limitation to the proposed technique is that contemporary navigation protocols do not exist for guidewire navigation. This leads to a theoretical risk of threading the guidewire deep past the vertebral body and causing intraabdominal injury. In order to minimize this risk, we recommend pulling the guidewire back by several inches after cannulating the proximal pedicle20.
There is a general consensus that MIS techniques are associated with increased radiation exposure when compared to traditional open techniques due to their reliance on fluoroscopy25. Developing strategies to reduce radiation exposure and shorten operative time are critical to improving outcomes while minimizing the dangers of radiation overexposure25. Incorporating the intraoperative CT scan for navigation allows for the placement of pedicle screws without the need for constant fluoroscopy. Villard et al. found that radiation exposure using freehand techniques was almost 10 times higher than with navigation-guided techniques in a cohort of patients who underwent standard open posterior lumbar instrumentation26. Tabaree et al. demonstrated that the use of the O-arm resulted in similar breach rates as the C-arm, and radiation exposure was lowered for the surgeon but increased for the patient27. In another cadaveric study for iliosacral screw placement, Theologis et al. confirmed that the use of the O-arm increases radiation exposure to the patient28.
There are limited data on radiation exposure associated with the technique described in this manuscript; previous studies present radiation exposure as the total fluoroscopy time in seconds, while much of these data are generated from studies comparing traditional open TLIF to MIS-TLIF. Using image-guidance for pedicle screw placement, we found a reduction in the total fluoroscopic time compared to historical studies (42 s compared to 45-105 s). Furthermore, the average radiation dose in our study was 62.0 mGy with intraoperative CT scan accounting for 57% (35.4 mGy) of the radiation exposure; this compares favorably to a study performed by Mendelsohn et al., where intraoperative CT for navigation during spinal instrumentation increased the total radiation dose to the patient by 8.74 times29. However, the reduction in radiation was associated with an increase in operative time given that image acquisition can result in delays related to equipment transport and in some cases the need for multiple rounds of image acquisition. The results of this technique compare favorably to historical studies with respect to EBL and length of stay.
An advantage to our approach is that in certain cases, it eliminates the need for preoperative CT scan since these images can be acquired in the operating room. There are limited data on patient BMI and associated radiation exposure. Larger body habitus often requires increased radiation dosage to penetrate the soft tissue and may require additional exposures as the dosage is optimized intraoperatively. Bivariate correlation statistics found a Pearson correlation of 0.358 between BMI and fluoroscopy dose (p=0.013), but a value of 0.003 between BMI and fluoroscopy time (p=0.983), confirming that increased radiation dose, not increased time, was correlated with BMI.
This study is limited by its retrospective design. Additionally, there is frequently a high demand for intraoperative CT scan and these machines are not always available, resulting in a &#34;wait time&#34; for this part of the operation. Coordinating intraoperative CT scan availability with the OR start time has the potential to shorten total operative time by decreasing the &#34;wait time.&#34; Radiation exposure associated with intraoperative CT scan is relatively fixed, however, fluoroscopy represents an area for further radiation exposure reduction. Use of low dose protocols can be utilized, but their viability in obese patients and multilevel MIS-TLIFs is not yet validated. We are encouraged that even in these preliminary data, the average fluoroscopy time of 41.6 s compares very favorably to historical reports; when considering that our study included two and three level fusions, these data are even more promising. Future studies will incorporate streamlined communication with operating room staff and radiation technologists as well as low-dose fluoroscopy protocols.
In conclusion, in this article, we describe a single-surgeon experience using a novel technique incorporating a mixture of intraoperative CT-guided navigation and traditional fluoroscopy when performing an MIS TLIF. Such a technique represents an intermediary in the transition towards exclusively using navigation in the future30,31,32. One of the potential benefits of this technique is the reduction of radiation exposure to the patient as well as the surgeon. Preliminary results show promise, and future studies may prove further benefits with this technique.

The TLIF is one of several options available when considering interbody fusion for degenerative disc disease and spondylolisthesis. The TLIF technique was initially developed in response to complications associated with the more traditional posterior lumbar interbody fusion (PLIF) approach. More specifically, the TLIF minimized retraction of neural elements, thereby reducing the risk of nerve root injury as well as the risk of dural tears, which can lead to persistent cerebrospinal fluid leak. As a unilateral approach, the TLIF technique also affords better preservation of the normal anatomy of the posterior elements1. The TLIF can be performed either open (O-TLIF) or minimally invasive (MIS-TLIF), and MIS-TLIF has proven to be a versatile and popular treatment for lumbar degenerative disease and spondylolisthesis2,3,4. Compared to the O-TLIF, the MIS-TLIF has been associated with decreased blood loss, shorter hospital stay, and less narcotic use; patient-reported and radiographic outcome measures are also similar between open and MIS approaches, thus suggesting the MIS-TLIF is an equally effective but potentially less morbid procedure5,6,7,8,9,10,11.
However, a frequent limitation of the traditional MIS technique is the heavy reliance on fluoroscopy which exposes the patient, surgeon, and operating room staff to non-trivial radiation doses and fluoroscopy time ranging from 46-147 s12. More recently, however, the use of intraoperative CT-guided navigation has been studied, with several different systems available and described in the literature including the O-arm/STEALTH, Airo Mobile, and Stryker Spinal Navigation Systems.13,14 This type of navigated technique has been shown to result in accurate pedicle screw placement while also minimizing the radiation risk to the surgeon15,16,17,18,19. In this article, we present a novel technique for MIS-TLIF that utilizes image-guidance-based pedicle screw placement followed by cage and rod placement with traditional fluoroscopy. This strategy has the potential to increase the speed and accuracy of the pedicle screw placement while minimizing the radiation exposure to both the patient and operating room staff.

<table><tbody><tr><td>O-arm intraoperative CT</td><td>Medtronic, Minneapolis, MN</td><td></td><td></td></tr><tr><td>Stealth Navigation System</td><td>Medtronic, Minneapolis, MN</td><td></td><td></td></tr><tr><td>Jamshidi Needles</td><td></td><td></td><td>for bone marrow biopsy</td></tr><tr><td>Cefazolin&amp;nbsp;</td><td></td><td></td><td>antibiotic.</td></tr><tr><td>Vicryl Sutures</td><td></td><td></td><td></td></tr><tr><td>Steri-Strips</td><td></td><td></td><td>for skin closure</td></tr><tr><td>Telfa dressing</td><td></td><td></td><td></td></tr><tr><td>Tegaderm</td><td></td><td></td><td>for dressing</td></tr><tr><td>Jackson table</td><td></td><td></td><td></td></tr><tr><td>15-blade</td><td></td><td></td><td></td></tr><tr><td>High-speed bone drill</td><td></td><td></td><td></td></tr><tr><td>Tubular dilator</td><td></td><td></td><td></td></tr><tr><td>K-wires</td><td></td><td></td><td></td></tr><tr><td>Reduction towers</td><td></td><td></td><td></td></tr><tr><td>TLIF retractor</td><td></td><td></td><td></td></tr><tr><td>2 or 3 mm Kerrison rongeur</td><td></td><td></td><td></td></tr><tr><td>Woodson elevator</td><td></td><td></td><td></td></tr><tr><td>Disc shaver and distractor</td><td></td><td></td><td></td></tr><tr><td>Fluoroscopy</td><td></td><td></td><td></td></tr><tr><td>Allograft cellular bone matrix</td><td></td><td></td><td></td></tr><tr><td>Interbody cage</td><td></td><td></td><td></td></tr><tr><td>Rod</td><td></td><td></td><td></td></tr><tr><td>Soft lumbar brace</td><td></td><td></td><td></td></tr><tr><td>X-ray</td><td></td><td></td><td></td></tr><tr><td>Patient-controlled analgesia pump</td><td></td><td></td><td></td></tr></tbody></table>

cone beam intraoperative computed tomography-based image guidance for minimally invasive transforaminal interbody fusion

Transforaminal lumbar interbody fusion (TLIF) is commonly used for the treatment of spinal stenosis, degenerative disc disease, and spondylolisthesis. Minimally invasive surgery (MIS) approaches have been applied to this technique with an associated decrease in estimated blood loss (EBL), length of hospital stay, and infection rates, while preserving outcomes with traditional open surgery. Previous MIS TLIF techniques involve significant fluoroscopy that subjects the patient, surgeon, and operating room staff to non-trivial levels of radiation exposure, particularly for complex multi-level procedures. We present a technique that utilizes an intraoperative computed tomography (CT) scan to aid in placement of pedicle screws, followed by traditional fluoroscopy for confirmation of cage placement. Patients are positioned in the standard fashion and a reference arc is placed in the posterior superior iliac spine (PSIS) followed by intraoperative CT scan. This allows for image-guidance-based placement of pedicle screws through a one-inch skin incision on each side. Unlike traditional MIS-TLIF that requires significant fluoroscopic imaging during this stage, the operation can now be performed without any additional radiation exposure to the patient or operating room staff. After completion of the facetectomy and discectomy, final TLIF cage placement is confirmed with fluoroscopy. This technique has the potential to decrease operative time and minimize total radiation exposure.

Fifty patients underwent surgery with this technique under a single surgeon (AC). The average age was 53 years (range 29-84 years) with 30 women and 20 men. Patients presented with the following pathology: spinal stenosis (n=45), spondylolisthesis (n=29), facet cysts (n=5), degenerative scoliosis (n=3), and cauda equina syndrome (n=1). Symptoms were back and leg pain in 42 cases, back pain alone in 2 cases, and lower extremity radiculopathy in 6 cases. In 10 cases, patients had undergone previous surgery at the level of pathology. Results are summarized in Table 1.
A left-sided approach was used in 25 cases and right-sided in 25 cases. There were 33 single level fusions, 15 two level fusions, and 2 three level fusions. Fusion levels were as follows: L4-5 (n=35), L5-S1 (n=27), L3-4 (n=7), and L2-3 (n=2). The average cage height was 10.2 mm. The mean operative time was 240 min and the average EBL was 80 mL. There was a significant difference in operative time when comparing the number of levels fused; 200 min for single level, 306 min for two levels, and 393 min for three levels (p&#160;&#60; 0.001). The average radiation dose was 62.0 mGy, with 35.3 mGy from the intraoperative CT scan and 26.2 mGy from fluoroscopy. The average duration of fluoroscopy was 42.2 s, with 5.2 s from intraoperative CT scan and 37.1 s from traditional fluoroscopy. The average length of stay after surgery was 3 days (range 1-7 days). The results are summarized in Table 2.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/57830/57830fig1.jpg" /> 
Figure 1: CT-based navigation for MIS-TLIF. A bone marrow biopsy needle is placed through a stab incision into the ilium to harvest bone marrow aspirate (A). The navigation reference frame is placed in the posterior superior iliac spine in a trajectory that places the arc inferior and medial to avoid interference with the standard trajectory of S1 pedicle screws (B). Pedicle screw trajectories are visualized using the navigation system (C). The trajectory along the disc space is determined using the first tubular dilator by navigation (D). The use of intraoperative navigation allows for maximal safe decompression by identifying the location of the superior (E) and inferior (F) pedicles. <a href="https://www.jove.com/files/ftp_upload/57830/57830fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/57830/57830fig2.jpg" /> 
Figure 2: Intraoperative fluoroscopy for interbody cage placement. Fluoroscopy is used during the endplate preparation and distraction to ensure the appropriate height restoration and to avoid violation of the endplates (A). Imaging is used to confirm the appropriate final position (B). Standing 36-inch X-rays (lumbar region shown) are obtained on all patients prior to discharge (C). <a href="https://www.jove.com/files/ftp_upload/57830/57830fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Variable</td>
			<td>N=50</td>
		</tr>
		<tr>
			<td>Age&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>&#160;&#160; Mean (range)&#160;</td>
			<td>53 (29-84)</td>
		</tr>
		<tr>
			<td>Gender</td>
			<td></td>
		</tr>
		<tr>
			<td>&#160;&#160; Male</td>
			<td>20 (40%)</td>
		</tr>
		<tr>
			<td>&#160;&#160; Female</td>
			<td>30 (60%)</td>
		</tr>
		<tr>
			<td>BMI</td>
			<td></td>
		</tr>
		<tr>
			<td>&#160;&#160; Mean (range)</td>
			<td>30 (21-41)</td>
		</tr>
		<tr>
			<td>Pathology</td>
			<td></td>
		</tr>
		<tr>
			<td>&#160;&#160; Stenosis</td>
			<td>45 (90%)</td>
		</tr>
		<tr>
			<td>&#160;&#160; Spondylolisthesis</td>
			<td>29 (58%)</td>
		</tr>
		<tr>
			<td>&#160;&#160; Facet cyst&#160;</td>
			<td>5 (10%)</td>
		</tr>
		<tr>
			<td>&#160;&#160; Scoliosis&#160;</td>
			<td>3 (6%)</td>
		</tr>
		<tr>
			<td>&#160;&#160; Cauda equina</td>
			<td>1 (2%)</td>
		</tr>
		<tr>
			<td>Symptom location</td>
			<td></td>
		</tr>
		<tr>
			<td>&#160;&#160; Back</td>
			<td>2 (4%)</td>
		</tr>
		<tr>
			<td>&#160;&#160; Leg</td>
			<td>6 (12%)</td>
		</tr>
		<tr>
			<td>&#160;&#160; Both</td>
			<td>42 (84%)</td>
		</tr>
		<tr>
			<td>Previous surgery</td>
			<td>10 (20%)</td>
		</tr>
	</tbody>
</table>
Table 1: Patient demographics. 
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Variable</td>
			<td>N=50</td>
		</tr>
		<tr>
			<td>Approach&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>&#160;&#160; Left</td>
			<td>25 (50%)</td>
		</tr>
		<tr>
			<td>&#160;&#160; Right</td>
			<td>25 (50%)</td>
		</tr>
		<tr>
			<td>Number of levels fused</td>
			<td></td>
		</tr>
		<tr>
			<td>&#160;&#160; One</td>
			<td>33 (66%)</td>
		</tr>
		<tr>
			<td>&#160;&#160; Two</td>
			<td>15 (30%)</td>
		</tr>
		<tr>
			<td>&#160;&#160; Three</td>
			<td>2 (4%)</td>
		</tr>
		<tr>
			<td>Levels fused</td>
			<td></td>
		</tr>
		<tr>
			<td>&#160;&#160; L2/3</td>
			<td>2</td>
		</tr>
		<tr>
			<td>&#160;&#160; L3/4</td>
			<td>7</td>
		</tr>
		<tr>
			<td>&#160;&#160; L4/5</td>
			<td>35</td>
		</tr>
		<tr>
			<td>&#160;&#160; L5/S1*</td>
			<td>27</td>
		</tr>
		<tr>
			<td>Cage height (mm)</td>
			<td>10.2 (7-14)</td>
		</tr>
		<tr>
			<td>Estimated blood loss (ml)</td>
			<td>80 (10-550)</td>
		</tr>
		<tr>
			<td>Operative time (min)</td>
			<td>240 (88-412)</td>
		</tr>
		<tr>
			<td>Radiation dose (mGy)</td>
			<td></td>
		</tr>
		<tr>
			<td>Intraoperative CT</td>
			<td>35.3 (21.5-68.7)</td>
		</tr>
		<tr>
			<td>&#160;&#160; Fluoroscopy&#160;</td>
			<td>26.5 (4.3-64.3)</td>
		</tr>
		<tr>
			<td>&#160;&#160; Total</td>
			<td>62.0 (28.9-120.7)</td>
		</tr>
		<tr>
			<td>Radiation exposure (sec)</td>
			<td></td>
		</tr>
		<tr>
			<td>Intraoperative CT</td>
			<td>5.2 (1.0-24.5)</td>
		</tr>
		<tr>
			<td>&#160;&#160; Fluoroscopy</td>
			<td>37.1 (8.7-94.6)</td>
		</tr>
		<tr>
			<td>&#160;&#160; Total&#160;</td>
			<td>42.2 (12.2-100.0)</td>
		</tr>
		<tr>
			<td>Length of stay (days)</td>
			<td>3.1 (1-7)</td>
		</tr>
		<tr>
			<td colspan="2">* One patient with L5/L6 interbody fusion</td>
		</tr>
	</tbody>
</table>
Table 2: Surgical characteristics.

Watch this Scientific Journal Video about Cone Beam Intraoperative Computed Tomography-based Image Guidance for Minimally Invasive Transforaminal Interbody Fusion at JoVE.com

Cone Beam Intraoperative Computed Tomography-based Image Guidance for Minimally Invasive Transforaminal Interbody Fusion

The purpose of this article is to provide image-guidance for minimally invasive transforaminal interbody fusion.

Transforaminal lumbar interbody fusion (TLIF) is commonly used for the treatment of spinal stenosis, degenerative disc disease, and spondylolisthesis. ...

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6.2K Views.  University of California, San Francisco. The purpose of this article is to provide image-guidance for minimally invasive transforaminal interbody fusion.

Video: Cone Beam Intraoperative Computed Tomography-based Image Guidance for Minimally Invasive Transforaminal Interbody Fusion

Improved Registration of 3D CT Angiography with X-ray Fluoroscopy for Image Fusion During Transcatheter Aortic Valve Implantation

The fusion of 3D anatomical models derived from high-fidelity pre-interventional computed tomography angiography (CTA), and x-ray (XR) fluoroscopy to facilitate anatomical guidance is of huge interest for complex cardiac interventions like TAVI procedures with cerebral protection. Co-registration of CTA and XR has been introduced either based on additional intraoperative non-/contrast-enhanced cone-beam computed tomography (CBCT) or two separate aortograms. With the related increase of radiation exposure and/or contrast agent (CA) dose, a potential additional risk for the patient is introduced. Here, we propose a modified co-registration approach making use of arteriograms of the iliofemoral arteries, routinely performed during the femoral puncture and sheath introduction. On-the-fly refinement of the co-registration during the on-going procedure enables accurate co-registration without any additional angiograms, thus reducing CA, XR dose and procedure time, while simultaneously improving operator confidence and procedure safety.

The aim of this study was to improve the co-registration for image fusion (IF) of pre-interventional CT data with real-time x-ray (XR) fluoroscopy during transfemoral transcatheter aortic valve implantation (TAVI).

The fusion of 3D anatomical models derived from high-fidelity pre-interventional computed tomography angiography (CTA), and x-ray (XR) fluoroscopy to ...

A Mobile Outside-in Technique of Transforaminal Lumbar Endoscopy for Lumbar Disc Herniations

Percutaneous endoscopic transforaminal lumbar discectomy (PETLD) has now become a standard of care for the management of lumbar disc disease. There are two techniques for the introduction of a working cannula with respect to disc&#8212;outside-in and inside-out. The aim of this prospective study is to describe the technical aspects of a novel mobile outside-in method in dealing with different types of disc prolapse. A total of 184 consecutive patients with unilateral lower limb radiculopathy due to lumbar disc prolapse were operated on with the mobile outside-in technique of PETLD. Their clinical outcomes were evaluated based on the type of disc prolapse they had, a visual analog scale (VAS) leg pain score, the Oswestry Disability Index (ODI), and the Macnab criteria. The completeness of the decompression was documented with a postoperative magnetic resonance imaging. The mean age of the patients was 50 &#177; 16 years and the male/female ratio was 2:1. The mean follow-up was 19 &#177; 6 months. A total of 190 lumbar levels were operated on (L1&#8211;L2: n = 4, L2&#8211;L3: n = 17, L3&#8211;L4: n = 27, L4&#8211;5: n = 123, and L5&#8211;S1: n = 19). Divided into types, the patient distribution was central: n = 14, paracentral: n = 74, foraminal: n = 28, far lateral: n = 13, superior-migrated: n = 8, inferior migrated: n = 38, and high canal compromise: n = 9. The mean operative time was 35 &#177; 12 (25 - 56) min and the mean hospital stay was 1.2 &#177; 0.5 (1&#8211;3) days. The VAS score for leg pain improved from 7.5 &#177; 1 to 1.7 &#177; 0.9. The ODI improved from 70 &#177; 8.3 to 23 &#177; 5. According to the Macnab criteria, 75 patients (40.8%) had excellent results, 104 patients (56.5%) had good results, and 5 patients (2.7%) had fair results. Recurrence (including early and late) was seen in 15 out of the 190 levels that were operated on (7.89%). This article presents a novel outside-in approach that relies on a precise landing within the foramen in a mobile manner and does not solely depend upon the enlargement of the foramen. It is more versatile in application and useful in the management of all types of disc prolapse, even in severe canal compromise and high migration.

Here we present a protocol of a novel outside-in technique of transforaminal endoscopic discectomy for lumbar disc herniations. The technical aspects of the technique, the wide indications of use, and the results of the treatment in 184 patients are described in detail.

Percutaneous endoscopic transforaminal lumbar discectomy (PETLD) has now become a standard of care for the management of lumbar disc disease. There are ...

Intraoperative Ultrasound in Spinal Surgery

Since the 1980s, there have been several reports for the use of intraoperative ultrasound as a useful adjunct in spinal surgery. However, with the advent of newer cutting-edge imaging modalities, the use of intraoperative ultrasound in spine surgery has largely fallen out of favor. Despite this, intraoperative ultrasound continues to provide several advantages over other intraoperative techniques such as magnetic resonance imaging and computed tomography including being more cost-effective, efficient, and easy to operate and interpret. Additionally, it remains the only method for the real-time visualization of soft tissue and pathologies. This paper focuses on the advantages of using intraoperative ultrasound, especially in cases of intradural lesions and lesions ventral to the thecal sac when approaching posteriorly.

Here, we present a protocol on the use of intraoperative ultrasound in spinal surgery, particularly in cases of intradural lesions and lesions in the ventral spinal canal when using a posterior approach.

Since the 1980s, there have been several reports for the use of intraoperative ultrasound as a useful adjunct in spinal surgery. However, with the advent ...

Three-dimensional Navigation-guided, Prone, Single-position, Lateral Lumbar Interbody Fusion Technique

Lateral interbody fusion provides a significant biomechanical advantage over the traditional transforaminal lumbar interbody fusion due to the large implant size and optimal implant position. However, current methods for lateral interbody cage placement require either a two-staged procedure or a single lateral decubitus position that precludes surgeons from having either full access to the posterior spine for direct decompression or comfortable pedicle screw placement.
Herein is one institution's experience with 10 cases of a prone single-position approach for simultaneous access to the anterior and posterior lumbar spine. This allows both lateral lumbar interbody cage placement, direct posterior decompression, and pedicle screw placement, all in one position. Three-dimensional (3D) navigation is utilized for increased precision in both approaching the lateral spine and interbody cage placement. The traditional blind psoas muscle tubular dilation was also modified. Tubular retractors and lateral vertebral body retractor pins were used to minimize the risks to the lumbar plexus.

The single-position, prone, lateral approach allows for both lateral lumbar interbody placement and direct posterior decompression with pedicle screw placement in one position.

Lateral interbody fusion provides a significant biomechanical advantage over the traditional transforaminal lumbar interbody fusion due to the large ...

Neuroscience

C-arm-Free Simultaneous OLIF51 and Percutaneous Pedicle Screw Fixation in a Single Lateral Position

Oblique lumbar interbody fusion (OLIF) is an established technique for the indirect decompression of lumbar canal stenosis. However, OLIF at the L5-S1 level (OLIF51) is technically difficult because of the anatomical structures. We present a novel simultaneous technique of OLIF51 with percutaneous pedicle screw fixation without fluoroscopy. The patient is placed in a right lateral decubitus position. A percutaneous reference pin is inserted into the right sacroiliac joint. An O-arm scan is performed, and 3D reconstructed images are transmitted to the spinal navigation system. A 4 cm oblique skin incision is made under navigation guidance along the pelvis. The internal/external and transverse abdominal muscles are divided along the muscle fibers, protecting the iliohypogastric and ilioinguinal nerves. Using a retroperitoneal approach, the left common iliac vessels are identified. Special muscle retractors with illumination are used to expose the L5-S1 intervertebral disc. After disc preparation with navigated instruments, the disc space is distracted with navigated trials. Autogenous bone and demineralized bone material are then inserted into the cage hole. The OLIF51 cage is inserted into the disc space with the help of a mallet. Simultaneously, percutaneous pedicle screws are inserted by another surgeon without changing the lateral decubitus position of the patient.
In conclusion, C-arm-free OLIF51 and simultaneous percutaneous pedicle screw fixation are performed in a lateral position under navigation guidance. This novel technique reduces surgical time and radiation hazards.

C-arm-free oblique lumbar interbody fusion at the L5-S1 level (OLIF51) and simultaneous pedicle screw fixation are performed in a lateral position under navigation guidance. This technique does not expose the surgeon or operating staff to radiation hazards.

Oblique lumbar interbody fusion (OLIF) is an established technique for the indirect decompression of lumbar canal stenosis. However, OLIF at the L5-S1 ...

Full Endoscopic Transforaminal Thoracic Discectomy Operative Technique

Thoracic disc herniations are a degenerative pathology of the thoracic spine wherein a portion of nucleus pulposis herniates into the epidural space, potentially causing spinal cord or nerve root compression. Traditional surgical treatment for patients with thoracic disc herniations requires relatively invasive anterior or posterolateral approaches that involve extensive muscular dissection and removal of bone in order to access and remove the disc herniation without causing undue compression of the spinal cord. Full endoscopic thoracic discectomy is a minimally invasive technique which allows for the resection of thoracic disc herniations through a small (1 cm) incision, minimizing collateral tissue trauma and obviating the need for the extensive muscle dissection and bony removal required for traditional surgical approaches. In this article, we describe in detail the operative technique for full endoscopic thoracic discectomy and discuss the pearls and pitfalls of the technique. We also provide a review of the outcomes and complications as seen in the literature.

This protocol demonstrates the surgical technique for full endoscopic transforaminal resection of thoracic disc herniations.

Thoracic disc herniations are a degenerative pathology of the thoracic spine wherein a portion of nucleus pulposis herniates into the epidural space, ...

Application of the O-arm Intraoperative Imaging System to Assist Anterior Cervical Screw Fixation for Odontoid Fractures

Odontoid fractures account for a large proportion of cervical spine fractures in the elderly, causing pain in the occiput and the back of the neck and restricting neck movement. Anterior cervical screw fixation is a common surgical procedure to treat odontoid fractures. Due to the special location and complex anatomy of the odontoid, surgeons need to perform intraoperative fluoroscopies repeatedly to ensure correct screw position and avoid damage to the peripheral nerves and vessels of the odontoid. The traditional anterior cervical screw fixation is usually conducted with the assistance of a C-arm. However, compared to the C-arm, an O-arm intraoperative imaging system can provide 3D images during surgery, which improves the accuracy of screw placement. This study retrospectively analyzed patients with anterior cervical odontoid fractures treated in our hospital. The application of the O-arm intraoperative imaging system for assisting screw placement in the treatment of odontoid fractures can reduce intraoperative blood loss, operation time, and trauma to the patients.

This study describes the application of the O-arm intraoperative imaging system in odontoid fractures.

Odontoid fractures account for a large proportion of cervical spine fractures in the elderly, causing pain in the occiput and the back of the neck and ...

Clinical Application of Microscope-Assisted Minimally Invasive Anterior Lumbar Interbody Fusion

This study aims to investigate the technical aspects of microscope-assisted anterior decompression fusion and to introduce a spreader system suitable for minimally invasive anterior lumbar interbody fusion (Mini-ALIF). This article is a technical description of anterior lumbar spine surgery under a microscope. We retrospectively collected information on patients who underwent microscope-assisted Mini-ALIF surgery at our hospital between July 2020 and August 2022. A repeated-measures ANOVA was used to compare imaging indicators between periods. Forty-two patients were included in the study. The mean volume of intraoperative bleeding was 180 mL, and the mean operative time was 143 min. The mean follow-up time was 18 months. Apart from one case of peritoneal rupture, no other serious complications occurred. The postoperative foramen and disc height were both higher on average than before surgery. The spreader-assisted micro-Mini-ALIF is simple and easy to use. It can provide good intraoperative disc exposure, good discrimination of important structures, adequate spreading of the intervertebral space, and the restoration of the necessary intervertebral height, which is very helpful for less experienced surgeons.

The technique described in this article is well-suited to the Mini-ALIF procedure, allows for excellent exposure and decompression, and facilitates microscope-assisted manipulation.

This study aims to investigate the technical aspects of microscope-assisted anterior decompression fusion and to introduce a spreader system suitable for ...

Oblique Lumbar Interbody Fusion at L5-S1 Segment Through an Approach Between the Psoas Muscle and the Great Vessels

Over the years, the oblique lateral interbody fusion (OLIF) technique has gained significant recognition for treating various spinal conditions in lumbar segments L2-L5. However, the adoption of OLIF for the L5-S1 segment has not been widely embraced by the spinal surgery community, given that significant concerns remain regarding the applicability of OLIF for lumbosacral fusion. In this study, a cohort of 20 patients underwent interbody fusion at the L5-S1 level using the OLIF technique through a single retroperitoneal oblique approach positioned between the Psoas muscle and the great vessels. The procedure involved discectomy and endplate preparation accomplished through a surgical window created on the anterolateral side of the L5-S1 disc. For secure interbody fusion cage placement, a supplementary cage insertion approach was employed. All patients were followed up for a minimum of 12 months. The mean preoperative visual analog scale (VAS) score for lower back pain was 6.3 &#177; 1.5 and experienced a significant reduction to 1.2 &#177; 0.8 at 12 months. The VAS score for lower limb pain significantly decreased from 5.6 &#177; 1.4 preoperatively to 0.8 &#177; 0.3 at 12 months after the surgery. Furthermore, the preoperative Oswestry disability index (ODI) improved from 82.4% &#177; 16.2% to 8.1% &#177; 2.0% at 12 months. Radiographic evaluations after surgery confirmed improved lumbosacral junction reconstruction for all patients. At the final follow-up, successful bony fusion was observed in all cases. Based on these findings, the OLIF technique for L5-S1 fusion represents an attainable approach for lumbosacral reconstruction. The procedure&#39;s success hinges on a comprehensive preoperative plan and precise intraoperative techniques.

The protocol presents an OLIF L5-S1 technique that offers a more feasible approach for lumbosacral fusion sharing a common surgical plane with OLIF L2-5. This facilitates reproducible multi-level interbody fusions extending from L2 to S1 through a retroperitoneal oblique corridor between the Psoas muscle and the great vessels.

Over the years, the oblique lateral interbody fusion (OLIF) technique has gained significant recognition for treating various spinal conditions in lumbar ...

Full-Endoscopic Foraminoplasty and Lumbar Discectomy for Single-Level Lumbar Disc Herniation

The Transforaminal Endoscopic Surgical System (TESSYS) technique has gained popularity for the treatment of lumbar disc herniations. Foraminoplasty is the key procedure in TESSYS. However, it requires advanced skills and long-term learning, which hinder its widespread adoption among surgeons. Recently, the introduction of full-endoscopic solutions has made the process more manageable. The main difference from traditional single-portal endoscopic surgery is that full-endoscopic surgery is equipped with a larger working channel, allowing full visualization of foraminoplasty and decreasing reliance on intraoperative fluoroscopy. Recently, published studies have shown that full-endoscopic foraminoplasty and lumbar discectomy (FEFLD) could achieve comparable results to conventional microdiscectomy in terms of pain relief and functional outcomes, while enhancing postoperative recovery. This study describes the technique of FEFLD in detail, including every crucial step, such as patient positioning, puncture trajectory, endoscopic dissection of the superior articular process (SAP), endoscopic foraminoplasty, and more. We hope this will be helpful to beginners who wish to apply this approach.

Compared to conventional transforaminal endoscopic surgery, full-endoscopic foraminoplasty and lumbar discectomy (FEFLD) is a unique technique that allows full visualization of foraminoplasty and reduces the need for intraoperative fluoroscopies. This article describes the surgical steps involved in the FEFLD technique, shedding light on surgical tips and potential pitfalls to ensure outstanding performance.

The Transforaminal Endoscopic Surgical System (TESSYS) technique has gained popularity for the treatment of lumbar disc herniations. Foraminoplasty is the ...