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 border="0" cellpadding="0" cellspacing="0" style="width:899px;" width="899">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">O-arm intraoperative CT</td>
			<td style="width:288px;">Medtronic, Minneapolis, MN</td>
			<td style="width:136px;"></td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">Stealth Navigation System</td>
			<td style="width:288px;">Medtronic, Minneapolis, MN</td>
			<td style="width:136px;"></td>
			<td style="width:191px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">Jamshidi Needles</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td>for bone marrow biopsy</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cefazolin&#160;</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td>antibiotic.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">Vicryl Sutures</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">Steri-Strips</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td>for skin closure</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">telfa dressing</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">tegaderm</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td>for dressing</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">Jackson table</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">15-blade</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">High-speed bone drill</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">Tubular dilator</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">K-wires</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">Reduction towers</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">TLIF retractor</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">2 or 3 mm Kerrison rongeur</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">Woodson elevator</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">Disc shaver and distractor</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">Fluoroscopy</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">Allograft cellular bone matrix</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">Interbody cage</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">Rod</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">Soft lumbar brace</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">X-ray</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:284px;">Patient-controlled analgesia pump</td>
			<td style="width:288px;"></td>
			<td style="width:136px;"></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.remotexs.ntu.edu.sg/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.remotexs.ntu.edu.sg/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

Dual-phase Cone-beam Computed Tomography to See, Reach, and Treat Hepatocellular Carcinoma during Drug-eluting Beads Transarterial Chemo-embolization

The advent of cone-beam computed tomography (CBCT) in the angiography suite has been revolutionary in interventional radiology. CBCT offers 3 dimensional&#160;(3D) diagnostic imaging in the interventional suite and can enhance minimally-invasive therapy beyond the limitations of 2D angiography alone. The role of CBCT has been recognized in transarterial chemo-embolization (TACE) treatment of hepatocellular carcinoma (HCC). The recent introduction of a CBCT technique: dual-phase CBCT (DP-CBCT) improves intra-arterial HCC treatment with drug-eluting beads (DEB-TACE). DP-CBCT can be used to localize liver tumors with the diagnostic accuracy of multi-phasic multidetector computed tomography (M-MDCT) and contrast enhanced magnetic resonance imaging (CE-MRI) (See the tumor), to guide intra-arterially guidewire and microcatheter to the desired location for selective therapy (Reach the tumor), and to evaluate treatment success during the procedure (Treat the tumor). The purpose of this manuscript is to illustrate how DP-CBCT is used in DEB-TACE to see, reach, and treat HCC.

Dual-phase cone-beam computed tomography (DP-CBCT) is a useful intraprocedural imaging technique for transarterial chemo-embolization treatment with drug-eluting beads of hepatocellular carcinoma. DP-CBCT has been used to perform three major steps in oncologic interventional radiology: tumor localization (see), navigation and intraprocedural catheter guidance (reach), and intraprocedural evaluation of treatment success (treat).

The advent of cone-beam computed tomography (CBCT) in the angiography suite has been revolutionary in interventional radiology. CBCT offers 3 ...

Minimally Invasive Establishment of Murine Orthotopic Bladder Xenografts

Orthotopic bladder cancer xenografts are the gold standard to study molecular cellular manipulations and new therapeutic agents&#160;in vivo. Suitable cell lines are inoculated either by intravesical instillation (model of nonmuscle invasive growth) or intramural injection into the bladder wall (model of invasive growth). Both procedures are complex and highly time-consuming. Additionally, the superficial model has its shortcomings due to the lack of cell lines that are tumorigenic following instillation. Intramural injection, on the other hand, is marred by the invasiveness of the procedure and the associated morbidity for the host mouse.
With these shortcomings in mind, we modified previous methods to develop a minimally invasive approach for creating orthotopic bladder cancer xenografts. Using ultrasound guidance we have successfully performed percutaneous inoculation of the bladder cancer cell lines UM-UC1, UM-UC3 and UM-UC13 into 50 athymic nude. We have been able to demonstrate that this approach is time efficient, precise and safe. With this technique, initially a space is created under the bladder mucosa with PBS, and tumor cells are then injected into this space in a second step. Tumor growth is monitored at regular intervals with bioluminescence imaging and ultrasound. The average tumor volumes increased steadily in in all but one of our 50 mice over the study period.
In our institution, this novel approach, which allows bladder cancer xenograft inoculation in a minimally-invasive, rapid and highly precise way, has replaced the traditional model.

The established technique to inoculate primary invasive orthotopic bladder cancer xenografts requires laparotomy and mobilization of the bladder. This procedure inflicts significant morbidity on the mice, is technically challenging and time-consuming. We therefore developed a high-precision, percutaneous approach utilizing ultrasound guidance.

Orthotopic bladder cancer xenografts are the gold standard to study molecular cellular manipulations and new therapeutic agents&#160;in vivo. Suitable ...

Encapsulation Thermogenic Preadipocytes for Transplantation into Adipose Tissue Depots

Cell encapsulation was developed to entrap viable cells within semi-permeable membranes. The engrafted encapsulated cells can exchange low molecular weight metabolites in tissues of the treated host to achieve long-term survival. The semipermeable membrane allows engrafted encapsulated cells to avoid rejection by the immune system. The encapsulation procedure was designed to enable a controlled release of bioactive compounds, such as insulin, other hormones, and cytokines. Here we describe a method for encapsulation of catabolic cells, which consume lipids for heat production and energy dissipation (thermogenesis) in the intra-abdominal adipose tissue of obese mice. Encapsulation of thermogenic catabolic cells may be potentially applicable to the prevention and treatment of obesity and type 2 diabetes. Another potential application of catabolic cells may include detoxification from alcohols or other toxic metabolites and environmental pollutants.

Here, we present a protocol for encapsulation of catabolic cells, which consume lipids for heat production in intra-abdominal adipose tissue and increase energy dissipation in obese mice.

Cell encapsulation was developed to entrap viable cells within semi-permeable membranes. The engrafted encapsulated cells can exchange low molecular ...

Electromagnetic Navigation Transthoracic Nodule Localization for Minimally Invasive Thoracic Surgery

The increased use of chest computed tomography (CT) has led to an increased detection of pulmonary nodules requiring diagnostic evaluation and/or excision. Many of these nodules are identified and excised via minimally invasive thoracic surgery; however, subcentimeter and subsolid nodules are frequently difficult to identify intra-operatively. This can be mitigated by the use of electromagnetic transthoracic needle localization. This protocol delineates the step-by-step process of electromagnetic localization from the pre-operative period to the postoperative period and is an adaptation of the electromagnetically guided percutaneous biopsy previously described by Arias et al. Pre-operative steps include obtaining a same day CT followed by the generation of a three-dimensional virtual map of the lung. From this map, the target lesion(s) and an entry site are chosen. In the operating room, the virtual reconstruction of the lung is then calibrated with the patient and the electromagnetic navigation platform. The patient is then sedated, intubated, and placed in the lateral decubitus position. Using a sterile technique and visualization from multiple views, the needle is inserted into the chest wall at the prechosen skin entry site and driven down to the target lesion. Dye is then injected into the lesion and, then, continuously during needle withdrawal, creating a tract for visualization intra-operatively. This method has many potential benefits when compared to the CT-guided localization, including a decreased radiation exposure and decreased time between the dye injection and the surgery. Dye diffusion from the pathway occurs over time, thereby limiting intra-operative nodule identification. By decreasing the time to surgery, there is a decrease in wait time for the patient, and less time for dye diffusion to occur, resulting in an improvement in nodule localization. When compared to electromagnetic bronchoscopy, airway architecture is no longer a limitation as the target nodule is accessed via a transparenchymal approach. Details of this procedure are described in a step-by-step fashion.

Presented here is a protocol for lung nodule localization using dye marking via electromagnetically navigated transthoracic needle access. The technique described here can be accomplished in the peri-operative period to optimize nodule localization and to successful resection when performing minimally invasive thoracic surgery.

The increased use of chest computed tomography (CT) has led to an increased detection of pulmonary nodules requiring diagnostic evaluation and/or ...

A Pre-clinical Rat Model for the Study of Ischemia-reperfusion Injury in Reconstructive Microsurgery

Ischemia-reperfusion injury is the main cause of flap failure in reconstructive microsurgery. The rat is the preferred preclinical animal model in many areas of biomedical research due to its cost-effectiveness and its translation to humans. This protocol describes a method to create a preclinical free skin flap model in rats with ischemia-reperfusion injury. The described 3 cm x 6 cm rat free skin flap model is easily obtained after the placement of several vascular ligatures and the section of the vascular pedicle. Then, 8 h after the ischemic insult and completion of the microsurgical anastomosis, the free skin flap develops the tissue damage. These ischemia-reperfusion injury-related damages can be studied in this model, making it a suitable model for evaluating therapeutic agents to address this pathophysiological process. Furthermore, two main monitoring techniques are described in the protocol for the assessment of this animal model: transit-time ultrasound technology and laser speckle contrast analysis.

Here, we describe a pre-clinical animal model for studying the pathophysiology of ischemia-reperfusion injury in reconstructive microsurgery. This free skin flap model based on the superficial caudal epigastric vessels in the rat may also allow for the evaluation of different therapies and compounds to counteract ischemia-reperfusion injury-related damage.

Ischemia-reperfusion injury is the main cause of flap failure in reconstructive microsurgery. The rat is the preferred preclinical animal model in many ...

Evaluation of Capnography Sampling Line Compatibility and Accuracy when Used with a Portable Capnography Monitor

Capnography is commonly used to monitor patient&#8217;s ventilatory status. While sidestream capnography has been shown to provide a reliable assessment of end-tidal CO2 (ETCO2), its accuracy is commonly validated using commercial kits composed of a capnography monitor and its matching disposable nasal cannula sampling lines. The purpose of this study was to assess the compatibility and accuracy of cross-paired capnography sampling lines with a single portable bedside capnography monitor. A series of 4 bench tests were performed to evaluate the tensile strength, rise time, ETCO2 accuracy as a function of respiratory rate, and ETCO2 accuracy in the presence of supplemental O2. Each bench test was performed using specialized, validated equipment to allow for a full evaluation of sampling line performance. The 4 bench tests successfully differentiated between sampling lines from different commercial sources and suggested that due to increased rise time and decreased ETCO2 accuracy, not all nasal cannula sampling lines provide reliable clinical data when cross-paired with a commercial capnography monitor. Care should be taken to ensure that any cross-pairing of capnography monitors and disposable sampling lines is fully validated for use across respiratory rates and supplemental O2 flow rates commonly encountered in clinical settings.

The goal of this study was to evaluate the accuracy of capnography sampling lines used in conjunction with a portable bedside capnography monitor. Sampling lines from 7 manufacturers were evaluated for tensile strength, rise time, and ETCO2 accuracy as a function of respiratory rate or supplemental oxygen flow rate.

Capnography is commonly used to monitor patient&#8217;s ventilatory status. While sidestream capnography has been shown to provide a reliable assessment ...

Time-Resolved, Dynamic Computed Tomography Angiography for Characterization of Aortic Endoleaks and Treatment Guidance via 2D-3D Fusion-Imaging

In the United States, more than 80% of all abdominal aortic aneurysms are treated by endovascular aortic aneurysm repair (EVAR). The endovascular approach warrants good early results, but adequate follow-up imaging after EVAR is imperative to maintain long-term positive outcomes. Potential graft-related complications are graft migration, infection, fraction, and endoleaks, with the last one being the most common. The most frequently used imaging after EVAR is computed tomography angiography (CTA) and duplex ultrasound. Dynamic, time-resolved computed tomography angiography (d-CTA) is a reasonably new technique to characterize the endoleaks. Multiple scans are done sequentially around the endograft during acquisition that grants good visualization of the contrast passage and graft-related complications. This high diagnostic accuracy of d-CTA can be implemented into therapy via image fusion and reduce additional radiation and contrast material exposure.
This protocol describes the technical aspects of this modality: patient selection, preliminary image review, d-CTA scan acquisition, image processing, qualitative and quantitative endoleak characterization. The steps of integrating dynamic CTA into intra-operative fluoroscopy using 2D-3D fusion-imaging to facilitate targeted embolization are also demonstrated. In conclusion, time-resolved, dynamic CTA is an ideal modality for endoleak characterization with additional quantitative analysis. It can reduce radiation and iodinated contrast material exposure during endoleak treatment by guiding interventions.

Time-Resolved, Dynamic Computed Tomography Angiography for Characterization of Aortic Endoleaks and Treatment Guidance via 2D-3D Fusion-Imaging

Dynamic computed tomography angiography (CTA) imaging provides additional diagnostic value in characterizing aortic endoleaks. This protocol describes a qualitative and quantitative approach using time-attenuation curve analysis to characterize endoleaks. The technique of integrating dynamic CTA imaging with fluoroscopy using 2D-3D image fusion is illustrated for better image guidance during treatment.

In the United States, more than 80% of all abdominal aortic aneurysms are treated by endovascular aortic aneurysm repair (EVAR). The endovascular approach ...

Sample Preparation for Computed Tomography-based Three-dimensional Visualization of Murine Hind-limb Vessels

Blood vessels are complex networks with tree-like structures, and vascular networks are essential for maintaining both circulation and maintaining organ function. Clarifying the mechanism of blood vessel formation is therefore extremely useful for elucidating developmental processes and pathological mechanisms. Murine hind-limb vessels are often used as a model for physiological and pathological angiogenesis. Evaluation is mainly performed via a two-dimensional method using tissue sections. However, methods for evaluating three-dimensional (3D) vascular morphology are particularly limited. This paper introduces a method for visualizing murine hind-limbs using computed tomography (CT). Radiation-opaque resin is injected through the descending aorta, and whole vessels are filled with dye. By adjusting the time of dye injection, arterial-specific filling is also possible, and samples can be obtained with any micro-X-ray CT device. This contrast method provides a basic technique for the 3D evaluation of murine blood vessels in the lower extremities. Furthermore, this method can be used to visualize all blood vessels below the diaphragm and evaluate blood vessels in the abdominal organs.

Here, we describe a visualization and quantification method for murine hind-limb vessels using micro-X-ray computed tomography.

Blood vessels are complex networks with tree-like structures, and vascular networks are essential for maintaining both circulation and maintaining organ ...

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 ...

3D Cephalometric Landmark Annotation Demonstration on Human CBCT Scans

Three-Dimensional Cephalometric Landmark Annotation Demonstration on Human Cone Beam Computed Tomography Scans

Craniofacial cephalometric analysis is a diagnostic tool used for the assessment of the relationship of various bones and soft tissues in the head and face. Cephalometric analysis has been traditionally conducted with the use of 2D radiographs and landmark sets and restricted to size, linear and angular measurements, and 2D relationships. The increasing use of 3D cone beam computed tomography (CBCT) scans in the dental field dictates the need for the evolution to 3D cephalometric analysis, which incorporates shape and a more realistic analysis of longitudinal development in all three planes. This study is a demonstration of 3D cephalometric analysis with the use of a validated set of skeletal tissue landmarks on human CBCT scans. Detailed instructions for the annotation of each landmark on a 3D volume are provided as part of a step-by-step protocol. The generated measurements and 3D coordinates of the landmarks can be exported and used both for clinical and research purposes. The introduction of 3D cephalometric analysis in basic and clinical craniofacial studies will lead to future advancements in the field of craniofacial growth and development.

Author Spotlight: Three-Dimensional Cephalometric Landmark Annotation Demonstration on Human Cone Beam Computed Tomography Scans  

Presented here is a detailed protocol for the conduction of three-dimensional cephalometric analysis with the use of human cone beam computed tomography scans.

Craniofacial cephalometric analysis is a diagnostic tool used for the assessment of the relationship of various bones and soft tissues in the head and ...