Glenoid component placement accuracy in total shoulder arthroplasty with preoperative planning and standard instrumentation is not influenced by supero-inferior glenoid erosion

Purpose: Accurate glenoid component placement in total shoulder arthroplasty (TSA) remains challenging even with preoperative planning, especially for variable glenoid erosion patterns in the coronal plane. Methods: We retrospectively reviewed 170 primary TSAs in which preoperative planning software was used. After registration of intraoperative bony landmarks, surgeons were blinded to the navigation screen and attempted to implement their plan by simulating placement of a central-axis guide pin: 230 screenshots of simulated guide pin placement were included (aTSA = 66, rTSA = 164). Displacement, error in version and inclination, and overall malposition from the preoperatively-planned target point were stratified by the Favard classification describing superior-inferior glenoid wear: E0 (n = 89); E1 (n = 81); E2 (n = 29); E3(n = 29); E4(n = 2). Malposition was considered > 10° for version/inclination errors or > 4 mm displacement from the starting point. Results: Mean displacement error was 3.5 ± 2.7 mm (aTSA = 2.7 ± 2.3 mm, rTSA = 3.8 ± 2.9 mm), version error was 5.7 ± 4.7° (aTSA = 5.8 ± 4.4°, rTSA = 5.7 ± 4.8°), inclination error was 7.1 ± 5.6 (aTSA = 4.8 ± 4.8°, rTSA = 8.1 ± 5.7°), and malposition rate was 53% (aTSA = 38%, rTSA = 59%). When compared by Favard classification, there were no differences in any measure; when stratified by TSA type, version error differed for rTSAs (P =.038), with E1 having the greatest version error (6.9 ± 5.2°) and E3 the least (4.2 ± 3.4°). When comparing glenoids without wear (E0) and glenoids with superior wear (E2 and E3), the only difference was greater version error in glenoids without wear (6.0 ± 4.9° vs. 4.6 ± 3.7°, P =.041). Conclusions: Glenoid malposition did not differ based on coronal glenoid morphology. Although, malposition was relatively high, suggesting surgeons should consider alternate techniques beyond preoperative planning and standard instrumentation in TSA. Level of evidence III: Retrospective Cohort Study.