The European Robotic Spinal Instrumentation (EUROSPIN) Study

Introduction A decade ago, minimally invasive surgery (MIS) was considered a promising development in spine surgery, yet the value of the pioneering technologies was questionable. With the growing number of experienced MIS surgeons, the influx of evidence in favour of MIS is rapidly increasing. This makes a compelling argument towards MIS offering distinct clinical benefits over open approaches in terms of blood loss, length of stay, rehabilitation, cost-effectiveness and perioperative patient comfort. Due to the limited or inexistent line-of-sight in MIS procedures, surgeons need to rely on imaging, navigation, and guidance technologies to operate in a safe and efficient manner. Therefore, a plethora of new and ever improving navigational systems have been developed. These systems allow a consistent level of safety and accuracy, on par with results achieved by very experienced free hand surgeons, with a reasonably short learning curve. Computer-based navigation systems were first introduced to spine surgery in 1995 and while they have been long established as standards in certain cranial procedures, they have not been similarly adopted in spine surgery.

Designed to overcome some of the limitations of navigation-based technologies, robot-guided surgery has become commercially available to surgeons worldwide, like SpineAssist® (Mazor Robotics Ltd. Caesarea, Israel) and the recently launched ROSA™ Spine (Zimmer-Biomet, Warsaw, Indiana, USA). These systems are rapidly challenging the gold standards. SpineAssist®, and its upgraded version, the Renaissance®, provides a stable drilling platform and restricts the surgeon's natural full range of motion to 2 degrees of freedom (up/down motion and yaw in the cannula). The system's guidance unit moves into the trajectory based on exact preoperative planning of pedicle screws, while accounting for changes in intervertebral relationships such as due to distraction, cage insertion or changes between the supine patient position in the preoperative CT and the prone patient on the operating table. Published evidence on robot-guided screw placement has demonstrated high levels of accuracy with most reports ranging around 98% of screws placed within the pedicle or with a cortical encroachment of less than 2 mm.4 Although the reliability and accuracy of robot-guided spine surgery have been established, the actual benefits for the patient in terms of clinical outcomes and revision surgeries remain unknown. We have recently conducted cohort studies that showed some evidence that robotic guidance lowers the rate of intraoperative screw revisions and implant related reoperations compared to free hand procedures, while achieving comparable clinical outcomes. We now want to assess these factors, among others, on a higher level of evidence. We aim to conduct a prospective, multicenter, multinational controlled trial comparing clinical and patient reported outcomes of robotic guided (RG) pedicle screw placement vs. navigated (NV) vs. free hand (FH) pedicle screw placement using pooled data from three centers.

Study Design The European Robotic Spinal Instrumentation (EUROSPIN) study is a prospective, international, multicentre, pragmatic, open-label, non-randomized controlled trial comparing the effectiveness of three techniques for pedicle screw instrumentation, namely RG, NV (CT-, O-Arm, or 3DFL-based), and FH. Following the baseline evaluation, patients will receive one of the three treatments, and will subsequently be followed up for 24 months (Figure 1). The primary analysis will be conducted using the 12-month data.

Sample Size Calculation It was determined that, to detect an intergroup difference of 5% in the primary endpoint, 205 patients are required per group to achieve a power of 1 - beta = 0.8 at alpha = 0.05. The incidence rates were based on the published literature, with an approximated incidence rate of the primary endpoint of 0% for the intervention and 5% for the control group. Because the study protocol is in line with the normal clinical follow-up of most centers, a low dropout rate is expected. This led to a minimum total sample size of 615 patients.

Monitoring An epidemiologist from the sponsor institution will organize an initiation monitor visit at every participating center before starting recruitment. This monitor visit will check whether all study staff are properly trained and the delegation of tasks are well documented (complete Investigator Site File, training and delegation logs). An additional audit will be carried out at 6 months after initiation of recruitment to check whether source documentation and eCRF documentation is similar. Throughout the entire study additional queries by the monitor are send to the investigator in the data capturing system to ensure proper data capturing.