Accuracy and precision of placement of the glenoid baseplate in reverse total shoulder arthroplasty using a novel computer assisted navigation system combined with preoperative planning: A controlled cadaveric study

Abstract Hypothesis RTSA glenoid baseplates will be placed more accurately and precisely with the use of preoperative planning and computer navigation compared to the use of preoperative planning and conventional freehand instrumentation alone. Material and methods Five fellowship trained surgeons preoperatively planned 30 cadaveric scapulae (15 side matched pairs) for an RTSA baseplate using preoperative CT scans and a custom 3D templating software. The specimens were randomized with respect to side and were split into two equal cohorts. One cohort used preoperative planning and conventional freehand instrumentation to implant the baseplate, and the other cohort used preoperative planning and a CT based navigation system to implant the baseplate. Postoperative CT scans were taken, and accuracy and precision for baseplate position and angulation with respect to the preoperative plan was compared for both groups. Results Glenoid baseplates placed using the navigation system demonstrated significantly improved accuracy and precision of positioning, based on the preoperative plan, than those placed using conventional freehand instrumentation without navigation for version (1.9 ± 1.9° vs 5.9 ± 3.5°; P = 0.004) and inclination (2.4 ± 2.4° vs 6.3 ± 6.2°; P = 0.026), with a post hoc power > 95% (α = 0.05). No significant difference was noted for anterior/posterior (AP) positioning, superior/inferior (SI) positioning, and reaming depth. A lower standard deviation was observed for AP positioning in the navigated cohort (0.6 mm vs 1.3 mm; P = 0.017). Conclusion Preoperative planning combined with the navigation system used in this side matched pair cadaveric study is more accurate and precise in achieving the desired version and inclination of the glenoid baseplate in RTSA compared to preoperative planning combined with conventional freehand instrumentation alone. The system may offer less benefit improving AP or SI placement as well as reaming depth.