Three-Dimensional CT-Based Simulation of Four Central Peg Placement Strategies for a Reverse Glenoid Baseplate

This three-dimensional (3D) CT-based simulation compared the geometric performance of four central peg placement strategies for a reverse glenoid baseplate in older adults. The study included one shoulder from each of 100 unique patients aged 60-87 years. Three-dimensional scapular models were reconstructed, and a 7.5 mm straight central peg was virtually placed. Maximum contained peg depth was recorded, and simulated cortical penetration was assessed for nominal peg lengths of 15, 20, and 25 mm. Angular deviations of 5°, 10°, and 15° were introduced. Two entry points-the glenoid center and a point 12 mm superior to the inferior rim-were combined with the standard centerline (SCL) and alternative centerline (ACL), forming four methods. Method b, placement from the glenoid center along the ACL, achieved the greatest mean initial maximum contained peg depth (24.99 ± 3.64 mm). At 25 mm, method b had the numerically lowest simulated penetration frequency, 46/100 (46%), compared with 52/100 (52%), 56/100 (56%), and 61/100 (61%) for methods a, c, and d, respectively; however, the paired overall comparison was not significant (Cochran's Q(3) = 6.44, P = 0.092). With angular deviation, method b retained the greatest mean depth at 5° (24.91 mm), whereas method c retained the greatest mean depth at 10° (20.23 mm) and 15° (18.29 mm). Inter-rater and intra-rater agreement were excellent. These findings characterize the geometry of the four simulated strategies; they do not establish intraoperative reproducibility, implant fixation strength, or clinical outcomes.