Navigation increases the accuracy of glenoid component implantation in reverse total shoulder arthroplasty in shoulders with severe glenoid wear: a comparative cohort study.

Background: Indications for reverse total shoulder arthroplasty (rTSA) have increased over the years and seem to yield satisfactory functional results even in patients with severe glenoid wear. New technologies, such as navigation, have gained in popularity intending to increase implantation precision, which is a crucial factor for long-term implant survivorship. However, these technologies remain costly and their widespread use for everyday cases has yet to be determined. Objectives: This study aimed to compare the accuracy of glenoid component implantation in consecutive series of patients undergoing rTSA with and without navigation, according to the wear patterns of the glenoid. Study Design & Methods: Two consecutive series of patients operated on by the same shoulder surgeon for rTSA, with and without navigation using the NextAR system (Medacta, Castel San Pietro, Switzerland), were prospectively included in the study. Revision procedures or rTSA requiring glenoid bone graft were not included. Patients' demographics (age, sex, side, and body mass index), preoperative diagnosis, and glenoid wear patterns in both the coronal and axial planes were analyzed and defined as mild and severe. Postoperative implantation accuracy measurements were carried out on postoperative computed tomography scans and consisted of rTSA angle, version, maximal bone purchase of peripheral screws and central peg, and glenosphere eccentricity from the inferior glenoid neck. Results: 56 shoulders were included, 28 in each group. There were no significant differences in patient demographics, preoperative diagnosis, and wear pattern severity between both groups. In the navigated group, patients with severe bone wear presented a significantly higher accuracy in all analyzed parameters, whereas patients with mild glenoid defects did not show significant differences in the glenoid implantation version and glenosphere position from the inferior glenoid neck. Conclusion: Navigation significantly improves glenoid implantation accuracy, particularly in patients with severe glenoid wear patterns. While its applicability in standard cases is debatable for experienced shoulder surgeons, it could prove valuable for patients with severe bone defects. Further studies are needed to assess if this will impact clinical and long-term implant survival outcomes.