The procedure was performed in a conventional OR, equipped with a radiolucent OR table, a navigation platform, and a mobile CBCT device providing both 2D fluoroscopy and 3D CBCT images of high quality for AR navigation. Two porcine cadavers, which were approximately 80 cm in length and 45 kg, were used for the purpose of this study. The specimens were purchased commercially, and their use for this experiment did not require an ethical permit. All the devices, instruments, and software used within the described workflow are listed in the Table of Materials. The following step-by-step procedure was performed and repeated for each specimen.
1. Porcine cadaver specimen
<ol>
	<li>Place the porcine cadaver specimen on the operating table in the operating room.</li>
	<li>Drape the porcine cadaver specimen in sterile covers. Use incision film to cover the skin in the surgical field.</li>
</ol>
2. Identification of the vertebral levels of interest
<ol>
	<li>Using the CBCT scanner, identify the vertebral levels of interest by fluoroscopy. Use the wireless control tablet of the CBCT scanner to move the scanner to the desired position, align the x-ray beam, and to perform the fluoroscopy scan (Figure 1). 
	NOTE: The 2D scans can be immediately reviewed on the tablet. The vertebral levels are identified by looking for ribs on the fluoroscopy scan and counting upward or downward.</li>
	<li>Attach the radiolucent navigation dynamic reference clamp to a spinous process in the area of interest by exposing the spinous process and fastening the clamp using the dedicated screwdriver. Then, attach the reflective spheres of the reference frame to the clamp (Figure 2).</li>
	<li>Perform a CBCT scan, and transfer the scan to the navigation platform (via LAN) (Figure 3). The navigation system camera tracks the CBCT scanner and the dynamic reference frame, enabling automatic patient registration using the Brainlab Loop-X Automatic Registration software on the navigation platform.</li>
	<li>Start the Spine &#38; Trauma Navigation software on the navigation platform. Use the spinal pointer and the 2D navigation views to verify the accuracy of the patient registration on anatomical landmarks.</li>
</ol>
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/64474/64474fig01.jpg" /> 
Figure 1: The wireless control tablet of the CBCT scanner. The tablet showing the fluoroscopy images from the CBCT. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64474/64474fig01large.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/64474/64474fig02.jpg" /> 
Figure 2: A schematic picture of the clamp attached to the spinous process. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64474/64474fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/64474/64474fig03.jpg" /> 
Figure 3: The Loop-X CBCT. The CBCT performing a scan on the draped pig cadaver with the reference attached. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64474/64474fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
3. Instrument calibration
<ol>
	<li>Calibrate a navigated drill guide and a screw driver to the navigation system. For this purpose, select the instrument in the Brainlab Spine &#38; Trauma Instrument Setup software, and then present the real instrument to the camera of the navigation system along with a calibration device. Move the instrument in a rotating motion while in contact with the calibration device until the navigation system recognizes the instrument. Once calibrated, track and visualize the instrument on both the 2D images and the 3D model in the HMD.</li>
</ol>
4. Head-mounted device fitting
<ol>
	<li>Ensure that each surgeon is fitted with a Magic Leap headset (the HMD). Ensure the HMD and the navigation platform are connected to the same network (WLAN connection for the HMD and LAN connection for the navigation platform).</li>
	<li>To establish the communication between the HMD and the Spine &#38; Trauma Navigation software, look at the QR code displayed on the screen of the navigation platform. This starts the corresponding Mixed Reality application running on the HMD and transfer of data to the HMD.</li>
	<li>Perform the mixed reality alignment by looking at the spine reference array through the&#160;HMD for a few seconds. Wait for a 3D model of the spine, rendered based on the CBCT scan, to be accurately augmented onto the specimen in the HMD. In addition to the 3D overlay, look at the 2D navigation views and a second 3D model above the 2D navigation views (hover view) that are displayed in the HMD.</li>
</ol>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/64474/64474fig04v2.jpg" /> 
Figure 4: The view through the HMD. The surgeon&#39;s view through the HMD presenting both 2D and 3D information. The 3D overlay shows the planned 3D screws with protruding trajectory lines assisting instrument alignment. The lower 3D model is augmented onto the spine of the pig; additional information is provided in the 2D and 3D representations floating above, which can be positioned freely in the virtual space and switched on and off. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64474/64474fig04largev2.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
5. Planning the pedicle screw placement
<ol>
	<li>Plan the pedicle screw paths based on the 3D registered augmented model, aligning them with the anatomy of the spine, and visualize in the HMD (Figure 5). Perform fine-tuning of the screw paths on the touchscreen of the navigation platform.</li>
</ol>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/64474/64474fig05v2.jpg" /> 
Figure 5:&#160;Pedicle screw path planning. The paths for the pedicle screws being planned using the HMD and the navigation pointer. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64474/64474fig05largev2.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
6. Beginning the pedicle screw placement
<ol>
	<li>Make small skin incisions approximately 2 cm long with a scalpel for minimally invasive access to the pedicles based on the superimposed 3D model visible through the HMD (Figure 6).</li>
	<li>Using a minimally invasive technique, dissect the soft tissue, and dilate the canal with dilators&#160;until the pedicle entry point on the vertebral surface is reached.</li>
	<li>Adjust the depth of the drill guide to match the length of the screw planned for the pedicle. The planned screw length is displayed on the screen of the navigation system. Position and align the navigated drill guide to the planned path.</li>
	<li>Drill the pedicle using a power drill with a 4.5 mm drill bit (Figure 7). Drill according to the planned path; the drill guide stops the drill from going deeper than the planned depth.</li>
	<li>Estimate the time from the skin incision until the canal is drilled for each pedicle.</li>
</ol>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/64474/64474fig06v2.jpg" /> 
Figure 6:&#160;Minimally invasive incisions. The pig cadaver from above showing the minimally invasive incisions along the spine. To the right is the reference with the reflective spheres clamped to the spinous process. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64474/64474fig06largev2.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/64474/64474fig07v2.jpg" /> 
Figure 7: Drilling the pedicles. The pedicle is drilled with a power drill using the navigation visible through the HMD to align the drill guide to the pre-planned path. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64474/64474fig07largev2.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
7. Visualization of the screw placement
NOTE: No screws were placed to avoid metal artifacts during evaluation.
<ol>
	<li>Perform a second CBCT to acquire X-ray images of the drilled vertebrae for the accuracy analysis. Ensure the drilled canal in the vertebra is clearly visible before using it for subsequent accuracy analyses.</li>
</ol>
8. Cannulating the spine
<ol>
	<li>Repeat the above procedure described in section 2, section 4, section 6, and section 7 to cover the next region of interest until the whole spine is cannulated.</li>
	<li>Repeat the same procedure (sections 1-8) using the second specimen.</li>
</ol>
9. Image analysis
<ol>
	<li>Match the obtained CBCT images to the navigation plan and make corrections according to the laboratory notes taken during the procedure.</li>
	<li>Have an independent reviewer evaluate all the images and grade the cannulations according to the Gertzbein grading scale, from 0 to 3. Grades 0 or 1 are considered accurate. Grades 2 or 3 are considered inaccurate.</li>
	<li>Fuse the trajectories of the planned paths and the cannulations, and define the technical accuracy as the deviation from the path at the entry and target. Measure the angular deviation.</li>
</ol>

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None of the authors who are affiliated with clinical institutions (H.F., G.B., E.E., and A.E.-T.) have financial interests in the subject matter, materials, or equipment or with any competing materials and did not receive any payments from Brainlab. A.E.-T has been a consultant for Brainlab untill October 2022. The other authors affiliated with Brainlab (J.W., F.T., and L.W.) have financial interests in the subject matter, materials, and equipment, in the sense that they are employees of Brainlab. The extent of influence on the data, manuscript structure, and manuscript conclusions by these authors and/or Brainlab was limited to technical knowledge and support for the experiments, as well as performing the technical analysis of the image data. The authors without conflicts of interest had full control of all the data labeling, data analysis, information submitted for publication, and overall conclusions drawn in the manuscript. The prototype system described in this article is currently a research prototype and is not for commercial use.

In this study, a novel workflow for minimally invasive pedicle screw placement using an HMD in sterile conditions is described and its accuracy evaluated. There are several scientific reports on HMD systems for cranial and spinal navigation, two of which have gained FDA approval for clinical use17,18. Other studies have shown promising results in the usability of HMDs in sterile environments19,20, as well as good accuracy in phantom and cadaver studies12,13,21. The results of the current study support the usefulness and feasibility of the workflow in a sterile environment and can serve as an important basis for the clinical introduction of the current device.
This study is distinguished by the step-by-step description of the procedure in the OR. Using an integrated navigation concept, including intraoperative CBCT and HMD, the patient registration and image overlay can be automatized to save time and effort in the OR. Once the setup is completed and the surgeons are equipped with the eye-calibrated HMD, all the other steps can be performed seamlessly. A great advantage of the pre-planning of the screw trajectories is that any deviation from the correct path can immediately be visualized and corrected.
When the planning is complete, the trajectories can be seen through the pedicles and will match the anatomical angulations of the pedicles. Any trajectories not matching the angulation of the others will become evident, and the surgeon can then correct them to facilitate the subsequent rod placement. The planned trajectories are saved, and they can then be used to assess the technical accuracy after fusion to the postoperative scans. In this context, technical accuracy is a combination of the inbound error of the navigation system and the surgeon&#39;s ability to adhere to the planned path. Importantly, the possibility to perform a confirmation CBCT allows for the intraoperative revision of any screw that, despite navigation, may be incorrectly placed.
CBCT is a well-known and widely used imaging device for intraoperative navigation and postoperative verification. CBCT provides 3D images of superior quality compared to the 2D images from a C-arm, a device commonly used in spinal surgery. The image quality and diagnostic accuracy of CBCT are comparable to conventional CT. The time requirement for the setup and sterile draping is similar to that of a standard C-arm but with much better diagnostic quality imaging22,23,24,25.
The difference in technical accuracy between the entry point and the target point is a result of the fact that the accuracy at the entry point is highly dependent on the anatomy at the chosen entry point. If the entry point is placed on a slope on the bone surface, there always is a risk of skiving26,27. When the pedicle is entered, the rigid cortical walls will guide the device, and, hence, the deviation at the target will be smaller due to there being no room for wiggling.
The HMD provides a 3D model that is rendered from the intraoperative CBCT or preoperative imaging and augmented onto the actual spine. In addition, it displays 2D images in the axial, sagittal, and coronal planes, as well as a second 3D model that the surgeon can rotate and position anywhere in the virtual space, based on personal preference. Interaction with the display software is currently performed using a remote control. To use this remote control in a sterile environment, it would have to be placed in a sterile plastic bag. This is standard practice with several non-sterile handheld devices that have to be used in sterile environments. However, in a clinical environment, hand gestures or voice commands would be preferred. During navigation, virtual representations of the tracked instruments in the 2D and 3D views provide visual feedback to aid the surgeon.
The HMD itself has evolved, and the second generation of Magic Leap is lighter and has a larger field of view. The field of view is an important factor in the use of HMDs and represents one of the features that is constantly being developed further. The field of view of the Magic Leap was fully efficient for conducting this experiment and did not pose any limitations to the workflow. Each HMD has its own small computer that the surgeon needs to wear underneath their sterile gowns. The communication between the HMD and the navigation system is via Wi-Fi, and network limitations may result in latency. Despite this product being the first prototype, the current results indicate excellent clinical accuracy and submillimeter technical accuracy.
The limitations of this study are the small sample size and the porcine, cadaveric model. The possible effects of breathing and bleeding on the accuracy could not be evaluated. Although a minimally invasive technique was used, no screws were inserted. However, the screw canals were readily visible and allowed for an accurate assessment of accuracy without interference from metal artifacts.In conclusion, this paper provides a detailed description of a novel workflow for HMD AR navigation. When used for minimally invasive pedicle cannulations in a porcine model, submillimeter technical accuracy and 100% clinical accuracy could be achieved.

The correct placement of pedicle screws is important to avoid damage to neurovascular structures in and around the spine. The placement accuracy using the free-hand technique is highly variable1. By using 3D navigation, the accuracy is improved compared to traditional image-guided methods based on intraoperative fluoroscopy. Higher accuracy reduces the risk of revision surgery2,3.
With the estimation that mean life expectancy will continue to increase, an increasing number of elderly patients will need surgical spine procedures for various pathologies4. Minimally invasive approaches are gaining ground due to their lower morbidity, especially in the elderly5,6. However, these approaches are dependent on accurate navigational solutions. As navigation is image-based, efforts are being made to reduce the intraoperative radiation exposure of patients and staff7,8,9,10.
Augmented reality (AR) is an emerging technology in surgical navigation that aims to improve the accuracy and efficacy in the operating room (OR)11. AR superimposes computer-generated information onto a real-world view. This works especially well when the superimposed information is seen through an HMD. For that purpose, HMDs using head-up display technology have gained attention due to their small size, portability, and the possibility to maintain a direct line of sight. Several HMDs are available on the market today for AR navigation12,13,14,15,16.
The Magic Leap headset is an optical see-through HMD, including several cameras, a depth sensor, and inertial measurement units, which are used to determine the position and orientation of the headset in the environment. The purpose of this study was to evaluate the workflow of the Magic Leap HMD, combined with a conventional navigation system and a state-of-the-art mobile CBCT device, for intraoperative imaging in a realistic surgical environment.

<table><tbody><tr><td>Instrument tracking array spine &amp;amp; trauma&amp;nbsp;4-marker</td><td>Brainlab</td><td></td><td></td></tr><tr><td>Curve Navigation System</td><td>Brainlab</td><td></td><td>Navigation System&lt;br/&gt; &lt;img alt=&quot;Figure 1&quot; src=&quot;/files/ftp_upload/64474/64474eq01.jpg&quot; style=&quot;margin: auto;&quot;/&gt;</td></tr><tr><td>Disposable clip-on remote control</td><td>Brainlab</td><td></td><td>SmartClip</td></tr><tr><td>Drill guide tube, handle with marker spheres, drill guide depth control insertable, drill bits</td><td>Brainlab</td><td></td><td>Drill guide and accessories</td></tr><tr><td>Expedium</td><td>DePuy Synthes</td><td></td><td>Screwdriver&lt;br/&gt; &lt;img alt=&quot;Figure 3&quot; src=&quot;/files/ftp_upload/64474/64474eq03.jpg&quot; style=&quot;margin: auto;&quot;/&gt;</td></tr><tr><td>Instrument calibration matrix</td><td>Brainlab</td><td></td><td>Instrument Calibration Matrix&lt;br/&gt; &lt;img alt=&quot;Figure 4&quot; src=&quot;/files/ftp_upload/64474/64474eq04.jpg&quot; style=&quot;margin: auto;&quot;/&gt;</td></tr><tr><td>Loop-X</td><td>Brainlab</td><td></td><td>CBCT scanner&lt;br/&gt; &lt;img alt=&quot;Figure 5&quot; src=&quot;/files/ftp_upload/64474/64474eq05.jpg&quot; style=&quot;margin: auto;&quot;/&gt;</td></tr><tr><td>Magic Leap 2</td><td>Magic leap Inc.</td><td></td><td>Mixed Reality headset&lt;br/&gt; &lt;img alt=&quot;Figure 6&quot; src=&quot;/files/ftp_upload/64474/64474eq06v2.jpg&quot; style=&quot;margin: auto;&quot;/&gt;</td></tr><tr><td>Navigation pointer spine&amp;nbsp;</td><td>Brainlab</td><td></td><td>Navigation Pointer&lt;br/&gt; &lt;img alt=&quot;Figure 7&quot; src=&quot;/files/ftp_upload/64474/64474eq07v2.jpg&quot; style=&quot;margin: auto;&quot;/&gt;</td></tr><tr><td>Spine reference array for reference clamp carbon (4-Sphere Geometry)</td><td>Brainlab</td><td></td><td>Spine Reference Array&lt;br/&gt; &lt;img alt=&quot;Figure 8&quot; src=&quot;/files/ftp_upload/64474/64474eq08.jpg&quot; style=&quot;margin: auto;&quot;/&gt;</td></tr><tr><td>Spine reference clamp carbon with slider</td><td>Brainlab</td><td></td><td>Spine Reference Clamp&amp;nbsp;&lt;br/&gt; &lt;img alt=&quot;Figure 9&quot; src=&quot;/files/ftp_upload/64474/64474eq09.jpg&quot; style=&quot;margin: auto;&quot;/&gt;</td></tr><tr><td>TruSystem 7500</td><td>Trumpf</td><td></td><td>Operating table</td></tr><tr><td>Software</td><td></td><td></td><td></td></tr><tr><td>Mixed Reality Spine Navigation App for Magic Leap</td><td>Brainlab</td><td></td><td>Run on Curve Navigation System&lt;br/&gt; Version: 2.0</td></tr><tr><td>PDM</td><td>Brainlab</td><td></td><td>Run on Curve Navigation System&lt;br/&gt; Version: 4.2</td></tr><tr><td>Spine &amp;amp; Trauma Instrument Setup</td><td>Brainlab</td><td></td><td>Run on Curve Navigation System&lt;br/&gt; Version: 6.2</td></tr><tr><td>Spine &amp;amp; Trauma Navigation 2.0</td><td>Brainlab</td><td></td><td>Run on Curve Navigation System&lt;br/&gt; Version: 1.6</td></tr></tbody></table>

pedicle screw placement using an augmented reality head-mounted display in a porcine model

This protocol helps assess the accuracy and workflow of an augmented reality (AR) hybrid navigation system using the Magic Leap head-mounted display (HMD) for minimally invasive pedicle screw placement. The cadaveric porcine specimens were placed on a surgical table and draped with sterile covers. The levels of interest were identified using fluoroscopy, and a dynamic reference frame was attached to the spinous process of a vertebra in the region of interest. Cone beam computerized tomography (CBCT) was performed, and a 3D rendering was automatically generated, which was used for the subsequent planning of the pedicle screw placements. Each surgeon was fitted with an HMD that was individually eye-calibrated and connected to the spinal navigation system.
Navigated instruments, tracked by the navigation system and displayed in 2D and 3D in the HMD, were used for 33 pedicle cannulations, each with a diameter of 4.5 mm. Postprocedural CBCT scans were assessed by an independent reviewer to measure the technical (deviation from the planned path) and clinical (Gertzbein grade) accuracy of each cannulation. The navigation time for each cannulation was measured. The technical accuracy was 1.0 mm &#177; 0.5 mm at the entry point and 0.8 mm &#177; 0.1 mm at the target. The angular deviation was 1.5&#176; &#177; 0.6&#176;, and the mean insertion time per cannulation was 141 s &#177; 71 s. The clinical accuracy was 100% according to the Gertzbein grading scale (32 grade 0; 1 grade 1). When used for minimally invasive pedicle cannulations in a porcine model, submillimeter technical accuracy and 100% clinical accuracy could be achieved with this protocol.

In total, 33 navigated cannulations were performed. The time per cannulation and the clinical and technical accuracy were assessed on the postoperative CBCT scans (Figure 8).
<img alt="Figure 9" class="xfigimg" src="/files/ftp_upload/64474/64474fig09.jpg" /> 
Figure 8:&#160;The postoperative scan of a Gertzbein grade 0 cannulation. The scan includes the surgical plan for the pedicle cannulation, presented in the coronal, axial, and sagittal views. Note the close alignment of the virtual screw and the cannulated canal. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64474/64474fig09large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The mean insertion time per cannulation was 141 s &#177; 71 s (median [range]: 151 [43-471]; Figure 9).
<img alt="Figure 10" class="xfigimg" src="/files/ftp_upload/64474/64474fig10.jpg" /> 
Figure 9:&#160;Histogram and box of the distribution of the pedicle cannulation times. Top, histogram of the distribution of the pedicle cannulation times (n = 33); bottom, the corresponding box plot showing the median, interquartile range, and an outlier. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64474/64474fig10large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
All 33 cannulations were considered clinically accurate according to the Gertzbein grading scale (32 grade 0; 1 grade 1; Table 1).
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td></td>
			<td>Gertzbein Grade 0</td>
			<td>Gertzbein Grade 1</td>
			<td>Gertzbein Grade 2</td>
			<td>Gertzbein Grade 3</td>
			<td>Clinically Accurate</td>
			<td>Clinically Inaccurate</td>
			<td>Accuracy</td>
		</tr>
		<tr>
			<td>Number of screws</td>
			<td>32</td>
			<td>1</td>
			<td>0</td>
			<td>0</td>
			<td>33</td>
			<td>0</td>
			<td>100%</td>
		</tr>
	</tbody>
</table>
Table 1:&#160;Clinical accuracy of implanted screws according to the Gertzbein grading scale. Grades 0 or 1 were considered accurate. Grades 2 or 3 were considered inaccurate.
To assess the technical accuracy, the deviation of each cannulation from its planned path was measured at the bone entry and at the bottom of the drill canal (Figure 10). The 3D measurements were performed by fusing the intraoperative scan, including the planned cannulation paths, with the postoperative scan of the cannulations. The angular deviation was calculated based on these data.
<img alt="Figure 11" class="xfigimg" src="/files/ftp_upload/64474/64474fig11.jpg" /> 
Figure 10:&#160;Overview of the measurement model for technical accuracy. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64474/64474fig11large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
This method was previously described by Frisk et al.12. For the 33 pedicle cannulations performed, the technical accuracy was 1.0 mm &#177; 0.5 mm (median [range]: 1.0 [0.4-3.3]) at the entry point (Figure 11) and 0.8 mm &#177; 0.1 mm (median [range]: 0.8 [0.6-4.6]) at the bottom of the drill canal (Figure 12). The angular deviation was 1.5&#176; &#177; 0.6&#176; (median [range]: 1.5 [0.3-5.0]; Figure 13).
<img alt="Figure 12" class="xfigimg" src="/files/ftp_upload/64474/64474fig12.jpg" /> 
Figure 11:&#160;Technical accuracy at the bone entry point. Top, the technical accuracy at the entry; bottom, the corresponding box plot showing the median, interquartile range, and an outlier. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64474/64474fig12large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 13" class="xfigimg" src="/files/ftp_upload/64474/64474fig13.jpg" /> 
Figure 12: Technical accuracy at the target (tip of drill canal). Top, technical accuracy at the target (tip of the drill canal); bottom, the corresponding box plot showing the median, interquartile range, and outliers. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64474/64474fig13large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 14" class="xfigimg" src="/files/ftp_upload/64474/64474fig14.jpg" /> 
Figure 13: Angular deviation compared to the planned path. Top, angle deviation from the planned path; bottom, the corresponding box plot showing the median and interquartile range. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/64474/64474fig14large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Pedicle Screw Placement Using an Augmented Reality Head-Mounted Display in a Porcine Model

The augmented reality head-mounted display, Magic Leap, was used in combination with a conventional navigation system to place pedicle screws in a porcine model by adhering to a novel workflow. With a median insertion time of &lt;2.5 min, submillimeter technical accuracy and 100% clinical accuracy were achieved according to Gertzbein.

This protocol helps assess the accuracy and workflow of an augmented reality (AR) hybrid navigation system using the Magic Leap head-mounted display (HMD) ...

pedicle-screw-placement-using-an-augmented-reality-head-mounted

Nanyang Technological University

Without Section

Research

JoVE Journal

Medicine

2.1K Views.  Karolinska Institutet. In dit protocol bieden we een gedetailleerde gids over het integreren van augmented reality in uw minimaal invasieve workflow voor het vervangen van pedikelschroeven in een varkenskadavermodel. Aangezien augmented reality nog steeds een relatief nieuwe technologie is in de chirurgie, is het waardevol om chirurgen de juiste begeleiding te geven bij het gebruik ervan tijdens operaties. In deze onderzoeksopstelling gebruiken we een conventionele navigatie-opstelling met de toevoeging van een aug...

Video: Pedicle Screw Placement Using an Augmented Reality Head-Mounted Display in a Porcine Model

A Teleoperated Robotic System-Assisted Percutaneous Transiliac-Transsacral Screw Fixation Technique

Transiliac-transsacral screw fixation is challenging in clinical practice as the screws need to break through six layers of cortical bone. Transiliac-transsacral screws provide a longer lever arm to withstand the perpendicular vertical shear forces. However, the screw channel is so long that a minor discrepancy can lead to iatrogenic neurovascular injuries. The development of medical robots has improved the precision of surgery. The present protocol describes how to use a new teleoperated robotic system to execute transiliac-transacral screw fixation. The Robot was operated remotely to position the entry point and adjust the orientation of the sleeve. The screw positions were evaluated using postoperative computed tomography (CT). All the screws were safely implanted, as confirmed using intraoperative fluoroscopy. Postoperative CT confirmed that all the screws were in the cancellous bone. This system combines the doctor's initiative with the Robot's stability. The remote control of this procedure is possible. Robot-assisted surgery has a higher position-retention capacity compared with conventional methods. In contrast to active robotic systems, surgeons have full control over the operation. The robot system is fully compatible with operating room systems and does not require additional equipment.

Teleoperated robotic system-assisted percutaneous transiliac-transsacral screw fixation is a feasible technique. Screw channels can be implemented with high accuracy owing to the excellent freedom of movement and stability of the robotic arms.

Transiliac-transsacral screw fixation is challenging in clinical practice as the screws need to break through six layers of cortical bone. ...

Engineering

A Spine Robotic-Assisted Navigation System for Pedicle Screw Placement

Pedicle screw implantation has excellent treatment effects and is often used by surgeons in spinal fusion surgery. However, due to the complexity of human body anatomy, this surgical procedure is difficult and challenging, especially in minimally invasive surgery or patients with congenital anomalies and kyphoscoliosis deformity. In addition to the abovementioned factors, the surgical experience and technique of the surgeon also affect the recovery rates and complications of the patients after the surgical operation. Therefore, accurately performing pedicle screw implantation has is a constant topic of common concern for surgeons and patients. In recent years, with the technological development, robot-assisted navigation systems have gradually become adopted. These robot-assisted navigation systems provide surgeons with complete preoperative planning before surgery. The system provides 3D reconstructed images of each vertebra, allowing surgeons to understand the patient&#39;s physiological characteristics more quickly. It also provides 2D images of sagittal, coronal, axial and oblique planes so that surgeons can accurately perform pedicle screw placement plan.
Previous studies have demonstrated the effectiveness of robot-assisted navigation systems for pedicle screw implantation procedures, including accuracy and safety assessments. This step-by-step protocol aims to outline a standardized surgical technique note for robotic-assisted pedicle screw placement.

This article presents a standardized surgical technique for robotic-assisted pedicle screw placement by using robotic-assisted navigational systems. We present a step-by-step protocol and describe the workflow and precautions of this procedure.

Pedicle screw implantation has excellent treatment effects and is often used by surgeons in spinal fusion surgery. However, due to the complexity of human ...

Bioengineering

An Anesthesia, Surgery, and Harvest Method for the Evaluation of Transpedicular Screws Using an In Vivo Porcine Lumbar Spine Model

Pedicle screw fixation is the gold standard for the treatment of spinal diseases. However, many studies have reported the issue of loosening pedicle screws after spinal surgery, which is a serious concern. To address this problem, diverse types of pedicle screws have been examined to identify those with good fixation strength and osseointegration in spine bone. The porcine spine is a good alternative for the human spine in the evaluation of pedicle screws due to the anatomical size, mechanical characteristics, and cost. Although several studies have reported that pedicle screws are efficient in the porcine model, no study has described detailed protocols for the evaluation of a pedicle screw using the porcine model. Here, we describe a detailed method for evaluating transpedicular screws using an in vivo porcine lumbar spine model. The technical details for anesthesia, spine surgery, and harvest provided here will facilitate with the evaluation of the transpedicular screw fixation model.

An Anesthesia, Surgery, and Harvest Method for the Evaluation of Transpedicular Screws Using an In Vivo Porcine Lumbar Spine Model

Here, we introduce a method to evaluate transpedicular screws by using an in vivo porcine lumbar spine model.

Pedicle screw fixation is the gold standard for the treatment of spinal diseases. However, many studies have reported the issue of loosening pedicle ...

Combining Augmented Reality and 3D Printing to Display Patient Models on a Smartphone

Augmented reality (AR) has great potential in education, training, and surgical guidance in the medical field. Its combination with three-dimensional (3D) printing (3DP) opens new possibilities in clinical applications. Although these technologies have grown exponentially in recent years, their adoption by physicians is still limited, since they require extensive knowledge of engineering and software development. Therefore, the purpose of this protocol is to describe a step-by-step methodology enabling inexperienced users to create a smartphone app, which combines AR and 3DP for the visualization of anatomical 3D models of patients with a 3D-printed reference marker. The protocol describes how to create 3D virtual models of a patient&rsquo;s anatomy derived from 3D medical images. It then explains how to perform positioning of the 3D models with respect to marker references. Also provided are instructions for how to 3D print the required tools and models. Finally, steps to deploy the app are provided. The protocol is based on free and multi-platform software and can be applied to any medical imaging modality or patient. An alternative approach is described to provide automatic registration between a 3D-printed model created from a patient&rsquo;s anatomy and the projected holograms. As an example, a clinical case of a patient suffering from distal leg sarcoma is provided to illustrate the methodology. It is expected that this protocol will accelerate the adoption of AR and 3DP technologies by medical professionals.

Presented here is a method to design an augmented reality smartphone application for the visualization of anatomical three-dimensional models of patients using a 3D-printed reference marker.

Augmented reality (AR) has great potential in education, training, and surgical guidance in the medical field. Its combination with three-dimensional (3D) ...

Real-Time Dynamic Navigation System for the Precise Quad-Zygomatic Implant Placement in a Patient with a Severely Atrophic Maxilla

Zygomatic implants (ZIs) are an ideal way to address cases of a severely atrophic edentulous maxilla and maxilla defects because they replace extensive bone augmentation and shorten the treatment cycle. However, there are risks associated with the placement of ZIs, such as penetration of the orbital cavity or infra-temporal fossa. Furthermore, the placement of multiple ZIs makes this surgery risky and more difficult to perform. Potential intraoperative complications are extremely dangerous and may cause irreparable losses. Here, we describe a practical, feasible, and reproducible protocol for a real-time surgical navigation system for precisely placing quad-zygomatic implants in the severely atrophic maxilla of patients with residual bone that does not meet the requirements of conventional implants. Hundreds of patients have received ZIs at our department based on this protocol. The clinical outcomes have been satisfactory, the intraoperative and postoperative complications have been low, and the accuracy indicated by infusion of the designed image and postoperative three-dimensional image has been high. This method should be utilized during the entire surgical procedure to ensure ZI placement safety.

Here, we present a protocol to achieve precise quad-zygomatic implant placement in patients with severely atrophic maxilla using a real-time dynamic navigation system.

Zygomatic implants (ZIs) are an ideal way to address cases of a severely atrophic edentulous maxilla and maxilla defects because they replace extensive ...

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 ...

The Use of Mixed Reality in Custom-Made Revision Hip Arthroplasty: A First Case Report

The technology of 3D printing and visualization of anatomical structures is rapidly growing in various fields of medicine. A custom-made implant and mixed reality were used to perform complex revision hip arthroplasty in January 2019. The use of mixed reality allowed for a very good visualization of the structures and resulted in precise implant fixation. According to the authors' knowledge, this is the first described case report of the combined use of these two innovations. The diagnosis preceding the qualification for the procedure was the loosening of the left hip's acetabular component. Mixed reality headset and holograms prepared by engineers were used during the surgery. The operation was successful, and it was followed by early verticalization and patient rehabilitation. The team sees opportunities for technology development in joint arthroplasty, trauma, and orthopedic oncology.

A complex revision hip arthroplasty was performed using a custom-made implant and mixed reality technology. According to the authors&#39; knowledge, this is the first report of such procedure described in the literature.

The technology of 3D printing and visualization of anatomical structures is rapidly growing in various fields of medicine. A custom-made implant and mixed ...

Augmented Reality Navigation-Guided Core Decompression for Osteonecrosis of Femoral Head

Osteonecrosis of the femoral head (ONFH) is a common joint disease in young and middle-aged patients, which seriously burdens their lives and work. For early-stage ONFH, core decompression surgery is a classical and effective hip preservation therapy. In traditional procedures of core decompression with Kirschner wire, there are still many problems such as X-ray exposure, repeated puncture verification, and damage to normal bone tissue. The blindness of the puncture process and the inability to provide real-time visualization are crucial reasons for these problems.
To optimize this procedure, our team developed an intraoperative navigation system on the basis of augmented reality (AR) technology. This surgical system can intuitively display the anatomy of the surgical areas and render preoperative images and virtual needles to intraoperative video in real-time. With the guide of the navigation system, surgeons can accurately insert Kirschner wires into the targeted lesion area and minimize the collateral damage. We conducted 10 cases of core decompression surgery with this system. The efficiency of positioning and fluoroscopy is greatly improved compared to the traditional procedures, and the accuracy of puncture is also guaranteed.

Augmented reality technology was applied to core decompression for osteonecrosis of the femoral head to realize real-time visualization of this surgical procedure. This method can effectively improve the safety and precision of core decompression.

Osteonecrosis of the femoral head (ONFH) is a common joint disease in young and middle-aged patients, which seriously burdens their lives and work. For ...

Virtual Reality-3D Modeling for Minimally Invasive Neuro-Interventional Planning

Pioneering Patient-Specific Approaches for Precision Surgery Using Imaging and Virtual Reality

Endovascular treatment of complex vascular anomalies shifts the risk of open surgical procedures to the benefit of minimally invasive endovascular procedural solutions. Complex open surgical procedures used to be the only option for the treatment of a myriad of conditions like pulmonary and aortic valve replacement as well as cerebral aneurysm repair. However, due to advancements in catheter-delivered devices and operator expertise, these procedures (along with many others) can now be performed through minimally invasive procedures delivered through a central or peripheral vein or artery. The decision to shift from an open procedure to an endovascular approach is based on multi-modal imaging, often including 3D Digital Imaging and Communications in Medicine (DICOM) imaging datasets. Utilizing these 3D images, our lab generates 3D models of the pathologic anatomy, thereby allowing the pre-procedural analysis necessary to pre-plan critical components of the catheterization lab procedure, namely, C-arm positioning, 3D measurement, and idealized road-map generation. This article describes how to take segmented 3D models of patient-specific pathology and predict generalized C-arm positions, how to measure critical two-dimensional (2D) measurements of 3D structures relevant to the 2D fluoroscopy projections, and how to generate 2D fluoroscopy roadmap analogs that can assist in proper C-arm positioning during catheterization lab procedures.

Author Spotlight: Segmentation and VR for Advanced Neurovascular Interventions

Advancements in endovascular treatment have replaced complex open surgical procedures with minimally invasive options, like valve replacement and aneurysm repair. This paper proposes using three-dimensional (3D) modeling and virtual reality to aid in C-arm positioning, angle measurements, and roadmap generation for neuro-interventional catheterization lab procedural planning, minimizing procedure time.

Endovascular treatment of complex vascular anomalies shifts the risk of open surgical procedures to the benefit of minimally invasive endovascular ...

Optimized 3D Reconstruction and Motion Mapping for Remote AR-Assisted Surgery

Automatic Surgery in Transcatheter Aortic Valve Replacement Using Augmented Reality

Augmented Reality (AR) is in high demand in medical applications. The aim of the paper is to provide automatic surgery using AR for the Transcatheter Aortic Valve Replacement (TAVR). TAVR is the alternate medical procedure for open-heart surgery. TAVR replaces the injured valve with the new one using a catheter. In the existing model, remote guidance is given, while the surgery is not automated based on AR. In this article, we deployed a spatially aligned camera that is connected to a motor for the automation of image capture in the surgical environment. The camera tracks the 2D high-resolution image of the patient's heart along with the catheter testbed. These captured images are uploaded using the mobile app to a remote surgeon who is a cardiology expert. This image is utilized for the 3D reconstruction from 2D image tracking. This is viewed in a HoloLens like an emulator in a laptop. The surgeon can remotely inspect the 3D reconstructed images with additional transformation features such as rotation and scaling. These transformation features are enabled through hand gestures. The surgeon's guidance is transmitted to the surgical environment to automate the process in real-time scenarios. The catheter testbed in the surgical field is controlled by the hand gesture guidance of the remote surgeon. The developed prototype model demonstrates the effectiveness of remote surgical guidance through AR.

Author Spotlight: Revolutionizing Remote Surgery with Augmented Reality and Robotics for Enhanced Precision and Accessibility

This article presents the design and implementation of an automatic surgery module based on augmented reality (AR)- based 3D reconstruction. The system enables remote surgery by allowing surgeons to inspect reconstructed features and replicate surgical hand movements as if they were performing the surgery in close proximity.

Augmented Reality (AR) is in high demand in medical applications. The aim of the paper is to provide automatic surgery using AR for the Transcatheter ...

Pedicle Screw Placement Using an Augmented Reality Head-Mounted Display in a Porcine Model

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