Augmented Reality Versus Freehand Spinopelvic Fixation in Spinal Deformity: A Case-Control Study

Purpose: This study sought to compare screw placement accuracy and outcomes between freehand (FH) and AR-guided pelvic fixation. While pelvic fixation is a critical technique in spinal deformity surgery, S2-alar iliac (S2AI) screw placement poses challenges. Methods: We conducted a case-control study of 50 consecutive patients who underwent spinopelvic fixation at a single institution. AR guidance was performed using a head-mounted display (Xvision, Augmedics). Patient demographics, surgical characteristics, spinopelvic parameters, and screw breach grade were compared using univariate and multivariate statistics. Results: Pelvic fixation was performed FH in 21 patients (median age, 64; female, 38.1%; median BMI 32.3 kg/m²) and AR-guided in 29 patients (median age, 66; female, 51.7%; median BMI 28.4 kg/m²). Mean follow-up was longer in the FH group (28 mos vs 11 mos, P < 0.001). Pelvic fixation in the FH group was performed using either S2AI (90.5%) or dual S2AI (9.5%) screws. There were no significant differences in length of surgery (FH, 439 minutes; AR, 490 minutes; P = 0.1) or estimated blood loss (FH, 2.1L; AR, 1.9L; P = 0.7). Accuracy of FH pelvic fixation was 95.6% (43/45 screws) and accuracy of AR pelvic fixation was 96.5% (55/57 screws). Multivariable logistic regression for screw breach revealed no significant association with AR guidance when controlling for age, BMI, osteoporosis, and smoking. Conclusions: We present the first case-control study of AR-guided spinopelvic fixation, with findings suggesting parity between FH and AR-guidance, serving as foundation for prospective controlled studies with longitudinal follow-up to interrogate the benefits of AR-guidance in spinal deformity surgery.