ABSTRACT: Introduction: As robotic-guidance and minimally invasive approaches become more prevalent in spine surgery, there is a growing interest in high-level scientific evidence of their clinical value. MIS ReFRESH is the first prospective, comparative, multi-center study designed to assess differences in surgical complication and revision rates, and exposure to intra-operative radiation, in adult degenerative conditions, operated in a minimally invasive (MIS) approach in 1-to-3 level fusions. Materials and Methods: Multicenter data (9 sites) were prospectively collected from 379 adult patients indicated for fusion surgery, including demographics, complications, need for revision surgery and use of intra-operative fluoroscopy (in seconds). A single site randomized patients between arms, while other sites enrolled exclusively to one arm. We compared of incidence of revision surgeries and clinical complications (surgical and medical) through a logistic regression model (Cox) as well as intra-operative fluoroscopy use. Results: Altogether, 9 sites enrolled 379 cases: 287 in the robot-guided arm (RG), and 92 in the fluoro-guided arm (FG). One site randomized patients, 15 to RG and 11 to FG. Mean age of RG patients was 59.1 years vs. 62.4 for FG (p = 0.032) and BMI was 31.4 vs. 28.0, respectively (p < 0.001). Sex distribution was similar at 62.0% females in RG and 57.4% in FG (p = 0.468). Charlson Comorbidity Index was 0.5 ± 0.8 in RG vs. 0.3 ± 0.6 in FG (p = 0.022). There were 4.8 ± 1.2 pedicle screws per case in RG vs. 4.3 ± 0.9 screws in FG (p < 0.001). In RG 33% of cases were 2-levels and 5% 3-levels, while in FG 16% were 2-level fusions, and 1% were 3-level fusions. Use of fluoroscopy for the instrumentation phase was 3.8 ± 3.9 seconds/screw in RG vs. 16.9 ± 9.2 in FG (p < 0.001). Average follow up was 174 days in RG and 159 in FG. Within the first year of follow up there were 28 (9.7%) complications in RG vs. 35 (38.0%) in FG, and 4 (1.4%) revisions in RG vs. 4 (4.3%) in FG. When evaluated in a Cox logistic regression model that includes age, gender, BMI, Charlson Comorbidity Index and number of executed screws, the Relative Risk (RR) for a complication was 5.3 times higher in FG compared to RG (95% Confidence Interval (CI): 3.0-9.5, p < 0.001). RR for a revision surgery were 7.1 times higher for a fluoro-guided surgery compared to the robot-guided cases (95% CI 1.6-32.6, p = 0.012). Conclusion: We report our findings from a prospective, multi-center, comparative study of MIS lumbar fusions performed with robotic-guidance in 287 patients vs. fluoro-guidance in 92 controls. RR for a complication or a revision surgery was significantly higher in FG during the first year of follow-up compared to RG (5.3-fold and 7.1-fold, respectively). RG reduced fluoroscopy exposure time per case by 78%, or almost a minute, helping offset the patients’ exposure during the pre-operative CT scan required for planning the robotic procedure.
