The precision of patient-specific instrumentation guides for the positioning of the glenoid component in total reverse shoulder arthroplasty: an in vivo scanographic study

Objective Optimal position and fixation of the baseplate is essential for the longevity of the reverse shoulder arthroplasty (RSA) and the patient-specific instrumentation (PSI) can help the surgeon to achieve that purpose. The aim of this study was to assess the reliability of the PSI guides for the positioning of the baseplate and the fixation's screws. Method Prospective study involving 35 patients operated for RSA. The PSI guides were planned and used by the senior surgeon in all cases. We compared the planned orientation (frontal and axial) of the baseplate and the screws with the post-operative CT scan. Results The mean difference between the planned measures and the post-op measures was inferior to 2.5 degrees. The screw's length corresponded with the pre-op plan in 70% of the cases. Conclusion The use of a PSI guide to position the glenoid implant in total reverse shoulder arthroplasty is reliable, reduces the risk of positioning errors and improves the quality of fixation with the screws.