Glenoid Implant Positioning: A New Approach Using Structured Light

ABSTRACT Background: Glenoid implant positioning is an important and challenging step in total shoulder arthroplasty. Accurate glenoid positioning is considered essential to prosthesis longevity and functional outcomes. This paper presents Bullseye, a novel system to ensure accurate glenoid guide pin placement using a hand-held structured light scanner and computer vision algorithms. Methods: Preclinical evaluation of the intra-operative structured light-based Bullseye system was conducted for 10 sawbone and 18 cadaveric procedures. Each scapula was instrumented with a 3.2mm glenoid guide pin. The Bullseye system was used to determine the position of the guide pin within the scapulae. The accuracy of Bullseye for assessing guide pin start-point and trajectory was validated using CT as a gold standard. Results: All procedures were carried out successfully, requiring less than 1 minute of intra-operative imaging time. Guide pin start-point was measured to within 0.37±0.28 mm and 0.38±0.32 mm and trajectory to within 0.92±0.40 degrees and 1.27±0.80 degrees, respectively for the sawbone and cadaveric procedures. There was no significant difference in accuracy between the sawbone and cadaveric procedures. No relationships were found between system accuracy and glenoid version or arthritic grade. Conclusion: Intra-operative structured light imaging can be used to efficiently and accurately evaluate the 3D position of the glenoid guide pin for total shoulder arthroplasty in-vitro and ex-vivo. Clinical validation is required to determine if use of the Bullseye system improves component positioning outcomes and patient clinical outcomes in the context of a randomized controlled trial. Level of Evidence: Level IV; Case Series