Surgical Testing Comparison of Single Position Robot-Assisted Navigation Versus Conventional MIS Bilateral Screw Trajectory During LLIF Procedure: An In-vitro Study

Presented at SMISS Annual Forum 2019
By Themistocles Protopsaltis MD
With Jeffery Larson MD, Richard Frisch MD, Kade Huntsman MD, Todd Lansford MD, Robert Brady MD, Chris Maulucci MD, Gerald Hayward II BS, Jonathan Harris MS, Jorge Gonzalez BS, Brandon Bucklen PhD,

Disclosures: Themistocles Protopsaltis MD B; Globus Medical. Jeffery Larson MD B; Globus Medical., Richard Frisch MD A; Globus Medical. B; Globus Medical. F; Globus Medical., Kade Huntsman MD B; NuVasive. F; NuVasive, Titan Spine, ODC-SCI., Todd Lansford MD A; Orthofix, Globus Medical. B; Stryker K2M., Robert Brady MD A; Globus Medical. C; Globus Medical., Chris Maulucci MD None, Gerald Hayward II BS E; Globus Medical., Jonathan Harris MS E; Globus Medical, Inc., Jorge Gonzalez BS None, Brandon Bucklen PhD E; Globus Medical Inc.,


Lateral lumbar interbody fusion (LLIF) provides indirect decompression of the neural elements while minimizing the potential vascular complications associated with anterior lumbar interbody fusion (ALIF). Posterior fixation may be applied through various techniques such as conventional minimally invasive surgery (CMIS), requiring the patient to be repositioned prone to provide access to both pedicles. Conversely, robot-assisted navigation (RAN) of pedicle screws can be performed from a single position without flipping the patient. RAN is theorized to reduce patient surgical time, radiation, and blood loss due to positioning and workflow effects.


Evaluate the effect of RAN compared to CMIS methods in terms of surgical time and radiation exposure.


Twelve unembalmed human torsos were implanted with 2 level static LLIF cages, followed by posterior bilateral pedicle screw fixation using either CMIS (n=6) or RAN (n=6). Preoperative computed tomography (CT) RAN workflow utilized CT scans of the specimen taken offsite and transferred to the robotic system during setup. Screw planning was performed using these CT scans, which were merged with intraoperative fluoroscopy. Surgical times, radiation exposure, and breach score were measured. Patient flip time from a consecutive patient series was included.


Significant differences in surgical time and radiation dosages were found between groups. Surgical times for RAN and CMIS were 64.7±4.1 and 123.0±13.7 minutes, respectively. Posterior fixation times were 29.2±4.9 and 30.8±7.1 minutes, respectively (p>0.05). Times per screw for RAN and CMIS were 2.7±0.6 and 4.3±1.3 minutes, respectively (p<0.05). RAN resulted in significantly lower surgical time compared to CMIS (p<0.05). Radiation dosage and time were separated into interbody and posterior fixation, and sorted by imaging workflow. RAN and CMIS radiation exposure during screw and rod insertion were 0.4±0.2 and 2.7±1.6 rads, respectively (p<0.05). RAN had a single grade-2 breach, averaging a breach score of 1.03, while CMIS had 4 total breaches with 2 grade-2 breaches and 2 grade-5 breaches averaging a breach score of 1.28 (p<0.05).


Significant differences were found between conventional MIS and RAN technigues, with RAN resulting in shorter surgical times, less radiation exposure to the surgeon, and lower breach scores than CMIS. Consideration should be given to single-position LLIF procedures that utilize RAN to instrument the spine with bilateral pedicle screws.

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