Percutaneous placement of lumbar pedicle screws via intraoperative CT image–based augmented reality–guided technology

Abstract

<jats:sec><jats:title>OBJECTIVE</jats:title><jats:p>The authors aimed to assess, in a bone-agar experimental setting, the feasibility and accuracy of percutaneous lumbar pedicle screw placements using an intraoperative CT image–based augmented reality (AR)–guided method compared to placements using a radiograph-guided method. They also compared two AR hologram alignment methods.</jats:p></jats:sec><jats:sec><jats:title>METHODS</jats:title><jats:p>Twelve lumbar spine sawbones were completely embedded in hardened opaque agar, and a cubic marker was fixed on each phantom. After intraoperative CT, a 3D model of each phantom was generated, and a specialized application was deployed into an AR headset (Microsoft HoloLens). One hundred twenty pedicle screws, simulated by Kirschner wires (K-wires), were placed by two experienced surgeons, who each placed a total of 60 screws: 20 placed with a radiograph-guided technique, 20 with an AR technique in which the hologram was manually aligned, and 20 with an AR technique in which the hologram was automatically aligned. For each K-wire, the insertion path was expanded to a 6.5-mm diameter to simulate a lumbar pedicle screw. CT imaging of each phantom was performed after all K-wire placements, and the operative time required for each K-wire placement was recorded. An independent radiologist rated all images of K-wire placements. Outcomes were classified as grade I (no pedicle perforation), grade II (screw perforation of the cortex by up to 2 mm), or grade III (screw perforation of the cortex by &gt; 2 mm). In a clinical situation, placements scored as grade I or II would be acceptable and safe for patients.</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p>Among all screw placements, 75 (94%) of 80 AR-guided placements and 40 (100%) of 40 radiograph-guided placements were acceptable (i.e., grade I or II; p = 0.106). Radiograph-guided placements had more grade I outcomes than the AR-guided method (p &lt; 0.0001). The accuracy of the two AR alignment methods (p = 0.526) was not statistically significantly different, and neither was it different between the AR and radiograph groups (p &lt; 0.0001). AR-guided placements required less time than the radiograph-guided placements (mean ± standard deviation, 131.76 ± 24.57 vs 181.43 ± 15.82 seconds, p &lt; 0.0001). Placements performed using the automatic-alignment method required less time than those using the manual-alignment method (124.20 ± 23.80 vs 139.33 ± 23.21 seconds, p = 0.0081).</jats:p></jats:sec><jats:sec><jats:title>CONCLUSIONS</jats:title><jats:p>In bone-agar experimental settings, AR-guided percutaneous lumbar pedicle screw placements were acceptable and more efficient than radiograph-guided placements. In a comparison of the two AR-guided placements, the automatic-alignment method was as accurate as the manual method but more efficient. Because of some limitations, the AR-guided system cannot be recommended in a clinical setting until there is significant improvement of this technology.</jats:p></jats:sec>

Augmented reality navigation in spine surgery: a systematic review

“…Ten studies used intraoperative cone beam computed tomography (CBCT), with simultaneous patient position registration, to align radiological imaging with the patient in the operating room (OR) [ 2 , 8 , 16 – 22 , 38 ]. Eight studies used intraoperative computed tomography (CT) with simultaneous patient position registration [ 10 – 13 , 32 , 35 , 36 , 40 ]. The remaining studies used preoperative CT in some fashion, either coupled to manual alignment with hand gestures, fluoroscopy, or custom-made pointers to register bone surfaces in the OR [ 1 , 23 , 30 , 33 , 37 , 42 , 45 , 46 ].…”

“…Seven studies compared AR to FH with or without fluoroscopy for pedicle screw placement [ 14 , 18 , 19 , 22 , 32 , 38 , 42 ]. The study with the highest available evidence grade was performed by Elmi-Terander et al, comparing a prospective cohort of 20 patients to 20 retrospectively enrolled patients where FH with or without fluoroscopy had been used [ 19 ].…”

“…However, the study was small and carried no statistical analysis. Liu et al compared HMD-AR to fluoroscopy-guided FH pedicle screws in a study on phantom models [ 32 ]. No significant difference was found (HMD-AR: 94% vs. FH: 100%, p = 0.106).…”

“…Three studies reported shorter and one longer operating times when using AR compared to FH with or without fluoroscopy [ 2 , 32 , 45 , 46 ]. Ten studies reported favorable impact on surgical time but lacked controls, or reported qualitatively positive workflow results for AR navigation [ 11 , 13 , 20 , 21 , 23 , 30 , 36 , 38 , 42 ].…”

Robotic Spine Surgery and Augmented Reality Systems: A State of the Art

“…A similar experimental setup was utilized for lumbar pedicle screw placement simulated by Kirschner wires inser-tion. Visualization of the spine hologram through the HoloLens resulted in > 90% correct screw placement with faster insertion times [62][63][64] and no significant difference in accuracy between ARnavigated screw placement and conventional navigation. 65 Comparable outcomes were reported in a cadaveric study conducted by Urakov et al 66 comparing the accuracy of screw placement with either AR or traditional fluoroscopic guidance.…”