Clinical and radiological outcomes when using standard versus retentive polyethylene humeral cups in Delta III reverse shoulder arthroplasty

Background. The most common postoperative complication relating to reverse total shoulder arthroplasty (rTSA) is instability. To prevent luxation, we can insert a retentive polyethylene humeral cup. The purpose of this study was to evaluate the clinical outcomes, the incidence of luxation and scapular notching between standard versus retentive polyethylene humeral cups in Delta III rTSA. Materials and methods. Consecutive patients undergoing primary Delta III sTSA between September 2018 and December 2023 using standard versus retentive polyethylene humeral cups were retrospectively reviewed. The minimum clinical follow-up was of 12 months. Results. Fifty-one patients underwent rTSA during the study period: 35 with standard humeral cups and 16 with retentive polyethylene humeral cups. We found no prosthesis luxation in either of the two study groups. At the end of the follow-up, there were no differences in forward flexion, abduction or internal rotation between the two groups. There was a lower mean for external rotation in the retentive polyethylene humeral cup group but it was not statistically significant. There was no statistical difference in the postoperative Constant score at the end of the follow-up. The incidence of scapular notching was 62.8% and 62.5% for the standard and retentive polyethylene humeral cups, respectively. Conclusion. The Delta III rTSA using standard vs retentive polyethylene humeral cups provide functional improvement and pain relief. There were no differences between the two groups in clinical mobility, forward flexion, abduction, internal rotation, external rotation, incidence of luxation and scapular notching Level of evidence: Level III; Retrospective Cohort Comparison; Treatment Study