Optimizing Minimally Invasive Spine Surgery: A Fully 3D CT O-Arm Navigated Workflow in MIS TLIF

Summary

This study presents a standardized, fully navigated 3D CT O-Arm-guided workflow for minimally invasive transforaminal lumbar interbody fusion (MIS TLIF), aiming to improve workflow, surgical accuracy, and efficiency with full utility of 3D navigation in maximum steps.

Abstract

Minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) has become increasingly popular due to reduced tissue trauma, decreased blood loss, and faster recovery compared to traditional open procedures. The integration of 3D CT-based intraoperative navigation has significantly enhanced surgical precision and workflow optimization, potentially leading to better outcomes. However, workflow optimization has not been qualitatively or quantitatively assessed in MIS TLIF, and there may be an increase in setup and waiting times between surgeries in exchange for improved precision.

In this retrospective study at a tertiary spine center, 44 patients undergoing fully navigated MIS TLIF were evaluated. A total of 176 pedicle screws were inserted using a sequential, navigation-guided workflow tailored to TLIF and decompression. Surgical accuracy, functional outcomes, perioperative safety, and workflow efficiency were assessed. The findings revealed significant improvements in Oswestry disability index (ODI) and numerical rating scale (NRS) scores, minimal blood loss, short operative times, and high screw placement precision (6.81% Grade 1 breaches). This article supports the clinical reliability and reproducibility of a fully navigated O-arm-assisted MIS TLIF protocol, offering qualitative evidence of improved workflow not previously reported.

Introduction

Minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) offers several advantages over conventional open spinal surgery, including reduced muscle damage, less intraoperative blood loss, and quicker recovery times^1,2,3,4,5,6. Recent advances in intraoperative navigation and three-dimensional (3D) computed tomography (CT) imaging have improved pedicle screw accuracy and reduced complication rates^7,8. Most existing literature focuses on discrete aspects of navigated MIS TLIF, such as pedicle screw accuracy or radiation exposure reduction^9,10,11, with little emphasis on a fully integrated, uninterrupted navigated workflow from preoperative imaging to decompression, cage placement, screw fixation, and final verification.

This workflow is most suitable for adults aged 18-80 years with symptomatic lumbar degenerative pathology such as single-level degenerative spondylolisthesis, lumbar stenosis, or disc degeneration, provided pedicle anatomy is preserved. Contraindications include advanced osteoporosis, severe deformity, or prior instrumentation at the same level.

This retrospective study, conducted at a tertiary spine center, evaluated 44 patients who underwent fully navigated MIS TLIF. In total, 176 pedicle screws were placed using a sequential, navigation-guided workflow customized for TLIF and decompression. The designed workflow was used to evaluate outcomes of a fully navigated 3D CT-assisted MIS TLIF, focusing on implant accuracy, perioperative safety, functional improvements, and workflow efficiency compared against published benchmarks. The findings highlight the clinical reliability and reproducibility of a fully navigated O-arm-assisted MIS TLIF protocol, while also providing novel qualitative evidence of enhanced workflow not previously described in the literature.

Protocol

This study protocol was reviewed and approved by the Institutional Ethics Committee, protocol code: SSHRI/CS/NS/3 D,CT,TLIF/AK/74/04.25, and registered under the Clinical Trial Registry of India (CTRI/2025/04/085975). Written informed consent was obtained from all participants preoperatively.

1. Preoperative planning

1. Explain procedure risks, benefits, and alternatives to each patient, and obtain written informed consent.
2. Acquire dynamic lumbar spine X-rays (anteroposterior, lateral, flexion-extension lateral views) and MRI (T1, T2, Short Tau Inversion Recovery [STIR]) of the lumbar spine.
3. Record preoperative functional status with the Oswestry disability index (ODI) and the numerical rating scale (NRS) for both leg and back pain.
4. Record the indications and applicability of the single-level fusion for the disease.

2. Operating room setup and imaging

1. Under general anesthesia, position the patient prone on a padded, radiolucent spinal table. Secure the patient with chest and pelvic bolsters and non-constrictive cross-body straps to prevent movement. Ensure that there are no pressure points or abdominal compression.
2. Prepare and drape the surgical field using standard aseptic technique.
3. Set up the 3D CT imaging system, navigation workstation, and a high-definition optical visualization system (loupe: set magnification to 2.5x, exoscope, or microscope: set magnification to 5-10×).
4. Register the navigation instruments with the system to ensure accurate tracking.
5. Attach the dynamic reference frame (DRF) to the skin, proximally at the lower thoracic region, using a non-absorbable suture material; check rigid anchorage.
6. Acquire a baseline CT spin using the standard lumbar protocol (parameter: 120 kVp, 200 mAs, 512 × 512 matrix, 1 mm slice thickness).
   NOTE: The radiology staff must wear complete lead protection and remain behind the console, outside the radiation field, during image acquisition. The anesthetist temporarily suspends ventilation, and the entire surgical team moves to a designated sterile, radiation-free zone outside the operating room.
7. Register the acquired 3D image dataset to the navigation system. Use 1-2 anatomic points to interpolate and verify an error ≤1 mm before proceeding.

3. Navigated surgical steps

1. Mark paramedian skin incisions 4-6 cm lateral to the midline at the surgical level using navigation guidance with pedicle access kit (PAK) needle, overlay on the screen.
2. Target the junction of the facet and transverse process with as lateral an entry projection as possible. Incise skin and underlying fascia longitudinally to a length of approximately 4 cm with a No. 22 scalpel blade.
3. Under navigation, advance a 13 G, 150 mm PAK needle to the junction of the facet and transverse process as shown in Figure 1. Enter the center of the index pedicle in both axial and sagittal planes, ensuring a safe trajectory and enhancing convergence.
4. Continuously check intraoperative navigation screens to confirm that the needle tip remains contained within the cortical bone. In cases of smaller pedicles, plan and accept a lateral entry with medial convergence and an extra-pedicular trajectory. Remove the stylet, then railroad and secure a 1.0 mm nitinol steel guide wire through the sheath of the PAK needle into the vertebral body, ensuring the tip is firmly anchored at the bony entry point in the pre-decided trajectory.
5. During guide wire introduction, emphasize tactile feedback and the firm feel of cancellous bone resistance. At the same time, avoid excessive pressure to prevent anterior (ventral) crossing of the guide wire, which could lead to neurovascular injury. Once secured, remove the PAK needle sheath.
6. Bilaterally place and secure four guide pins into the four pedicles of the segment, then bend and tether them to the drapes using Allis forceps, keeping them away from the central operative field as shown in Figure 2.
   ​CAUTION: Advance instruments slowly and visualize the trajectory to avoid medial, lateral, or inferior breach^4,10.
7. For standard lateral recess stenosis (LRS) decompression or over-the-top (OTT) decompression, make a separate medial fascial incision through the same skin incision. Use the PAK needle under navigation to determine the site of this 2 cm fascial incision, which is usually 2-3 cm from the spinous process. The target is to place a guide wire onto the index facet with navigation guidance in LRS unilateral decompression cases (relatively straighter trajectory). For OTT, the target point is the spino-laminar line (converging trajectory).
8. Sequentially dilate the paraspinal muscle layers with 12 mm, 16 mm, and 20 mm dilators over the guide wire. Dock a 22 mm tubular quadrant retractor over the dilators onto the facet as shown in Figure 3 and secure it to the table-mounted arm.
9. Adjust the retractor to the facet and lamina according to the pathology and surgical target, for either LRS decompression or OTT decompression.
10. Bring in the microscope, exoscope, or use loupe magnification ergonomically. Achieve hemostasis and remove peri-laminar and peri-facetal soft tissue. Perform bone decompression using an ultrasonic bone scalpel blade set at medium amplitude (~22.5 kHz) with continuous irrigation maintained at 70% flow rate to prevent thermal injury.
11. Excise the hypertrophic facet component and ligamentum flavum to achieve unilateral or bilateral decompression of the target. Perform foraminal decompression or disc fragment excision when needed to release the neural tissue.
12. With adequate hemostasis, enter the disc space by performing a block-shaped annulotomy within the safe Kambin's triangle.
    1. Use curettes in the standard fashion to prepare the end plates by removing the cartilage and debulking the disc. Remove disc material using pituitary forceps. Confirm the end points by a grating sensation of the end plate and punctate bleeding bone.
    2. Use a sequential shaver-sizer to determine the size of the interbody spacer cage and to distract the interbody space. Insert 5-10 cc of morselized autograft (locally harvested during decompression) into the prepared disc space through a funnel.
    3. Use the sized cage on a navigated cage holder-impactor. Place the selected poly-ether-ether-ketone (PEEK) or titanium interbody cage (8-13 mm in height, 28-32 mm in length as decided by the sizer and projection image) into the prepared interbody space under navigation in a safe trajectory as shown in Figure 4, positioned adequately in the centero-ventral location between both endplates, firmly contained within the biconcave disc space.
13. Reconfirm decompression and remove any remaining debris by giving a wash. Remove the tubular retractor assembly.
14. Place cannulated pedicle screws (5.5-7.5 mm diameter, 40-55 mm length), based on sizing using navigation as shown in Figure 5, bilaterally over guide wires, verifying trajectory and length to cross two-thirds of the vertebral length. Confirm tactile feedback for proper purchase. Remove the guide wire as the screws cross the pedicle.
15. Determine the required rod length intra-operatively using a calibrated rod-caliper, aligned between the screw tulip heads through percutaneous extensions. This method allows accurate measurement without fluoroscopic assistance. Introduce the pre-contoured lordotic measured rod percutaneously with a rod inserter tool.
16. After placement, verify proper engagement of the rod within each screw tulip using a rod position checker. Once confirmed, perform sequential tightening of the set screws with a torque-limiting driver under compression mode (default setting: 8 Nm).
17. Perform a final 3D CT spin to confirm hardware position. Acceptable criteria include proper screw and cage placement, absence of medial or inferior breach, and congruent implant alignment with the spinal midline. Use shielding for radiation safety, and follow all measures as done for preoperative spine CT imaging.
18. Irrigate the wound and achieve meticulous hemostasis. Place a sub-fascial 10 Fr drain at the medial intermuscular site. Close the fascia with continuous 1-0 absorbable sutures, the subcutaneous tissue with interrupted 2-0 absorbable sutures, and the subcuticular layer with 3-0 fast-absorbing sutures.
19. NOTE: Routinely check the navigation reference frame for movement; recalibrate if drift is suspected.

Results

The primary focus of this study was to assess the ease of performing a fully navigated MIS TLIF, which could not be objectively quantified. The setup and waiting times were not prospectively measured in minutes for each case in our series. While no formal time-motion analysis was performed, surgeons and staff qualitatively reported a noticeable reduction in mid-procedure pauses in other workflows where the decompression and interbody fusion work is completed in 2D image guidance, followed...

Discussion

Our experience with a fully navigated 3D O-Arm-guided approach to MIS TLIF highlights and reinforces its capacity to combine precision, reproducibility, and safety^7,8. By anchoring the workflow around navigated pedicle screw placement and confirmation with intraoperative 3D imaging, the chances of technical error are significantly reduced⁹. These observations echo earlier reports, which have shown that 3D navigation can deliver high accura...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Absorbable suture – continuous 1-0	Vicryl (Polyglactin 910)	JE00H[HR26]
Absorbable suture – interrupted 2-0	Vicryl (Polyglactin 910)	J310H[HR26]
Absorbable suture – subcuticular 3-0	Monocryl (Poliglecaprone 25)	W9930[DS24]
Antiseptic solution (povidone-iodine/chlorhexidine)	Betadine	12008-OR
Disc shavers	Medtronic	SMALL-9569453, MEDIUM-9569454, LARGE-9569455
Fenestrated titanium pedicle screws	Medtronic	9012037 SERIES
Interbody cage (PEEK or titanium, 7–9 mm × 28–32 mm)	Medtronic	8557000 series
Magnification system (exoscope)	Zeiss	6640
Medtronic MISS blade retractor	Medtronic	875-149
Medtronic Nav PAK needle	Medtronic	PK1011
Nitinol guide wire	Medtronic	N351804
O-arm surgical imaging system	Medtronic O-arm	BI-700-00028-230
Pituitary forceps	Medtronic	9569525
Radiolucent padded spinal table with bolsters	Stan	CT-OT-01
Sequential dilators	Medtronic	Medtronic METRx II Dilator Set 9560430 series
StealthStation S8 system	Medtronic	9735670
Sterile drapes	Surgiwear	D106
Titanium rods (5.5 mm)	Medtronic	9015503
Torque-limiting driver (set at 8 Nm)	Medtronic	7480146
Ultrasonic bone scalpel (20 kHz, medium setting)	Misonix	110-31-1120
Wound drain (10 Fr subfascial)	Romovac	RD-1010