Robotic-assisted navigated minimally invasive pedicle screw placement in the first 100 cases at a single institution

Pedicle screw constructs are widely used for posterior fixation in spinal surgery because of their biomechanical superiority and significant correction. However, safe pedicle screw placement is paramount to achieving successful spine surgery [1]. Specialty training is required to avoid the catastrophic neurovascular complications of misplaced screws, which occur in about 4.2% of patients [2]. Nevertheless, pedicle screws are widely used in both young and adult patients, with numerous articles documenting a favorable risk-to-benefit ratio for spinal treatment [3].

Various techniques have been used to guide and confirm pedicle screw placement [4]. The use of anatomic landmarks, plain film radiography, fluoroscopic imaging (standard or image guidance), and computed tomography (CT) image guidance are examples of these techniques [5, 6]. The procedure, benefits, and limitations of each method, as well as comparisons between different approaches, have been widely published [7, 8]. Advances in medical imaging have improved the accuracy of pedicle screw placement from fluoroscopic-guided to computer-aided navigation [8]. The most recent advancement is the use of a navigated robotic-assisted spine surgery system designed to increase the accuracy of pedicle screw placement compared to freehand placement. Clinical outcome studies are required to determine pedicle screw placement accuracy when minimally invasive navigated robotic-assisted spine surgery was performed on the first 100 patients at a single institution.

An Institutional Review Board-exempt retrospective chart review was conducted from October 2017 to September 2018 on the first 100 navigated robotic-assisted spine surgeries. The demographic, intraoperative, and perioperative data of 100 patients who underwent lumbosacral pedicle screw placement with minimally invasive navigated robotic guidance using preoperative or intraoperative CT were analyzed. Pedicle screw malposition and reposition rates based on the surgeon’s intraoperative radiographic observations were collected. Secondary outcome measures included patient demographics, robot workflow, length of surgery, length of hospital stay, and intraoperative blood loss.

In the first 100 robotic cases, the average age was 63 ± 8 years and 48% (48/100) were female. The average body mass index was 30 kg/m² (range 17–44 kg/m²). Twenty-five percent of patients were either current or former smokers. Forty-two percent of patients were retired (Table 1). Of the 100 cases, 55 were lateral lumbar interbody fusion (LLIF), 16 were anterior lumbar interbody fusion (ALIF), and 29 were posterior lumbar interbody fusion (PLIF). The three most common numbers of vertebral levels with pedicle screws inserted were 2-level (36%), 3-level (39%), and 4-level (20%). Intraoperative CT was used in 73 cases, while preoperative CT was used in the remaining 27 cases (Table 2). The most common level with screws inserted was either L4 (30%) or L5 (30%) (Fig. 2). Among the 100 cases, the majority of diagnoses for surgery was degenerative spondylolisthesis with neurogenic claudication (45%) and degenerative spondylolisthesis (17%). A total of 582 pedicle screws were placed. Of the 582 screws, 20 were placed without the robot due to surgeon discretion, leaving 562 pedicle screws inserted by navigated robotic guidance. Of the 562 screws, only 7 had to be repositioned manually due to surgeon discretion to reach a screw placement success rate of 99% (Fig. 3). There were no returns to the OR reported for screw-related complications.

Navigated robotic-assisted spine procedures are in the early development [9]. In this study, a 99% screw placement success rate was reported for pedicle screw placement using minimally invasive navigated robotic-assisted spine surgery. In contrast, the pedicle screw accuracy rate reported by Kosmopoulos and Schizas [10] in a review of 130 studies with 37,337 pedicle screws was 95% with navigation and 90% without navigation [11]. According to Tang et al. [12], pedicle screw placement is variable even with new technologies; however, when compared to freehand screw placement, computer-navigated screws had substantially less risk of cortical damage [13]. Some inaccuracies may be attributed to a learning curve and adapting to a new workflow such as three-dimensional (3D) navigation. The 99% pedicle screw placement success rate using navigated robotic guidance recorded in the current study of the first 100 cases seems to indicate an extremely short learning curve.

Technological advances including navigation have improved the safety and accuracy of pedicle screw fixation. In a meta-analysis by Mason et al. [14], data were gathered from over 30 studies analyzing 9000 pedicle screws and found that the traditional fluoroscopy had an accuracy of 63.1%, two-dimensional navigation had 84.3% accuracy, and 3D navigation was most accurate at 95.5%. Gelalis et al. [15] performed similar analyses and concluded that navigation provides pedicle screw placement with higher accuracy. Jin et al. [16] reported a malposition rate of 9.8% in a series of 1145 screws placed with an intraoperative 2D/3D imaging navigation system.

This initial study of the first 100 cases at a single institution in the clinical use of navigated, robot-assisted spine surgery demonstrated a high pedicle screw placement success rate. There were no postoperative screw malpositions requiring a return to the OR. While this is a single-surgeon, single-site retrospective study, the pedicle screw placement success rate is better than the rates reported in the literature using robot-assisted techniques.

Navigated robotic guidance provides successful pedicle screw placement at a rate of 99% at this single institution, with a 0% return to OR rate.