A Quantitative Assessment of the Accuracy and Reliability of Robotic Guidance for Lumbar Fusion: A Technique and Application Accuracy

Presented at SMISS Annual Forum 2018
By Cory Hartman MD, MBA

Disclosures: Cory Hartman MD, MBA None


Minimally-invasive (MIS) approaches to the anterior column such as lateral (LIF) or transforaminal lumbar interbody fusion (TLIF) require percutaneous screw fixation to achieve circumferential instrumentation. Robotic guidance represents a new technology for augmenting the surgical workflow to improve screw placement accuracy and decreasing the ionizing radiation exposure to the surgical team.


Here we report our initial surgical experience with robotically assisted percutaneous screw placement following LIF and review our surgical workflow.


Consecutive patients undergoing single level fusion with robotically assisted percutaneous pedicle screw fixation (PSF) in prone or lateral decubitus position were identified. A novel CT-guided robotic guidance arm was used for screw placement (ExcelsiusGPS) in combination with the O-Arm (Medtronic). Demographic data, surgical timing, and perioperative complications were collected. Postoperative thin cut CT scans were used for screw localization. X, Y, Z coordinates of the screw tip and tail were calculated and compared with the intended target trajectory to assess targeting error. A breach was defined as violation of lateral or medial pedicle wall.


Twenty-seven patients with lumbar pathology underwent robotic minimally invasive lumbar interbody fusion with 112 robotically assisted percutaneous pedicle screws. The breach rate was 2.7%. Across 17 patients, the mean 3D accuracy was 4.8±2.3mm, mean 2D accuracy was 2.6±1.2mm, and mean angular offset was 5.5±4.1°. 3D accuracy was correlated with age (R=0.25, p=0.037) and BMI (R=0.252, p=0.038); accuracy did not differ between vertebral body levels (p>0.22). Mean operative time for percutaneous screws was 183±54 minutes and did not improve significantly over time.


Robotic guidance system provides for accurate percutaneous pedicle screw placement in the majority of cases. Nonetheless, the technology still represents an early phase of development, with a steep learning curve that trends towards improved surgical times with subsequent use. Future studies are needed to demonstrate the utility of this novel guidance system and continued improvement in workflow.