Robot-assisted Percutaneous Transfacet Screw Fixation Supplementing Oblique Lateral Interbody Fusion Procedure: Accuracy and Safety Evaluation of This Novel Minimally Invasive Technique

Abstract

Objectives: Percutaneous transfacet screw fixation (pTSF) is a minimally invasive posterior fixation technique supplementing oblique lateral interbody fusion (OLIF) for lumbar spinal disorders. Accurate screw insertion is difficult to achieve and technically demanding under 2-D fluoroscopy. Recently developed robot-assisted spinal surgery demonstrated a high level of accuracy of pedicle screw insertion and a low complication rate. No published study has reported this combination technique. The aim of our study was to evaluate the accuracy and safety properties of the combination of both minimally invasive techniques: robot-assisted pTSF supplementing the OLIF procedure.

Methods: This was an experimental and prospective study. Selected consecutive patients with lumbar degenerative disorders received robot-assisted pTSF supplementing the OLIF procedure using the TianJi Robot system operated by one senior surgeon from March to October 2018. The accuracy of screw insertion and perioperative screw-related complications were evaluated. Assessment of the accuracy of screw insertion included intraoperative robotic guidance accuracy and incidence of screw encroachments. Intraoperative robotic guidance accuracy referred to translational and angular deviations of screws, which were assessed by comparing the planned and actual screw trajectories guided by the robot on reconstructed images using TianJi Robot Planning Software. Screw encroachments were evaluated on postoperative CT images and classified by a grading system (A, excellent; B, good; C, poor). Screw-related complications including intraoperative pin skidding, screw malposition and adjustment, together with postoperative neurological symptoms that correlated with screw malposition were recorded.

Results: Ten patients, with an average age of 60.2 years, were selected and recruited in this study. All cases were degenerative lumbar spinal disorders, out of which there were 6 cases of Meyerding Grade I degenerative spondylolisthesis. Twenty-four transfacet screws were inserted by robotic assistance. Instrumented levels included nine segments at L_4-5 level and three segments at L_3-4 level. Two patients had both L_4-5 and L_3-4 level fixation. The average surgical time was 3.3 h (SD, 0.8 h). The mean blood loss was 90 mL (SD, 32 mL). Intraoperative guidance accuracy showed 1.09 ± 0.17 mm (ranging from 0.75 to 1.22 mm) translational deviation and 2.17° ± 0.39° (ranging from 1.47° to 2.54°) angular deviation. The gradings of screw encroachment were: 17 screws (71%) with Grade A, 6 screws (25%) with Grade B, and 1 screw (4%) with Grade C. Only one pin skidding occurred intraoperatively and revised subsequently. No postoperative neurological complications were found.

Conclusion: Our preliminary study of robot-assisted pTSF supplementing the OLIF procedure showed a high level of accuracy for screw insertion and this minimally invasive combination technique was found to be a feasible and safe procedure.

Keywords: Accuracy; Lumbar disorders; Oblique lateral interbody fusion; Robot; Transfacet screw.

Figure 1

TianJi Robot system.

Figure 2

Trajectory planning on robotic workstation. Green and yellow screw represented the trajectory of transfacet screws.

Figure 3

Guiding pin insertion with assistance of robot.

Figure 4

The process of transfacet screw insertion. (A) Optimal pin position confirmed by reconstructed fluoroscopic images. (B) Insertion of the cannulate AO screw along the pin guidance. (C) Screw position confirmation. (D) 1.5‐cm tiny incision at midline.

Figure 5

Step 1: Sample fused images, planned images as background images (color pink); K‐wire placement images as float images (color green). Bony structures aligned well in three planes: (A) Axial plane, (B) Sagittal plane, and (C) Coronal plane. Step 2: Pick up the 3‐D coordinates (EX, EY, EZ) of entry point and target point of the planned screw trajectory. Identify and pick up the 3‐D coordinates (TX′, TY′, TZ′) of the K‐wire placement: (D) Preplanned entry point and target point and (E) K‐wire entry point and target point. Step 3: Euclidean distance was used to calculate this deviation.

Figure 6

Grading system for screw positions: (A) Grade A, no cortex perforation; (B) Grade B, cortex perforation within 2 mm; and (C) Grade C, cortex perforation beyond 2 mm.