Routine use of patient specific instruments in reverse shoulder arthroplasty produces significant improvements in the inclination profile of the glenoid component.

The outcome of reverse shoulder arthroplasty (RSA) is strongly correlated to the accuracy of implantation, particularly with regard to inclination of the glenoid component. 3D planning has become more prevalent and with this has come the development of patient-specific instruments (PSI). In our centre, since 2019, all elective RSAs have been planned with a 3D printed PSI. We hypothesised that PSI has improved the inclination of the glenoid component since its introduction. Retrospective analysis identified 50 elective RSAs pre and post the use of PSI. Post-operative radiographs were assessed in the anterior-posterior orientation to identify an inclination angle by two investigators. The interrater reliability (ICC 3K) between the two investigators was 0.960 (CI 0.94-0.97). The mean inclination of the none PSI group was +7.53° (SD ±14.31) while the mean inclination of the PSI group was +2.95° (SD ±7.82) (p = 0.0498). This study demonstrates that routine use of an additional intra-operative adjunct, such as a PSI jig for all cases of RSA should be considered, to improve the ability of the surgeon to reproduce the surgical plan faithfully.