The Stryker Perform and Univers Apex short stems have different patterns of stress shielding but comparably low rates of loosening after reverse total shoulder arthroplasty

Background The purpose of this study was to compare short-term radiographic outcomes between the Apex Univers Revers (Arthrex, Inc.) and the Stryker Perform Reversed (Stryker Inc.) short-stem reverse total shoulder arthroplasty (rTSA) implants. Methods A retrospective review was conducted of patients who underwent rTSA between 2021 and 2023 by 2 fellowship-trained surgeons at separate institutions. Consecutive primary cases with ≥2 years of follow-up were included. Immediate and final post-operative radiographs were reviewed for signs of loosening and stress shielding, which were graded in 5 zones and classified according to the Schnetzke bone adaptation grades. Partial or complete calcar osteolysis was also recorded. Multivariable regression was performed, and multiplicity was controlled within outcome families using the Holm method. Results A total of 40 Univers Revers and 46 Stryker Perform implants met the study criteria. Groups were similar in age, sex, diagnosis, and follow-up duration. By zone, remodeling was more frequent with Univers Revers in Zone 2 (32.5% vs. 7.5%; adjusted P = .05) and Zone 5 (35.0% vs. 10.0%; adjusted P = .070). All other zones showed no significant differences between groups (all adjusted P > .05). Partial calcar osteolysis was observed in 1 Univers Revers (2.5%) and 1 Stryker Perform (2.2%) ( P = 1.000). The proportion of implants at risk for loosening was similar between Univers Revers (2.5%) and Stryker Perform (6.5%) ( P = .620). Subsidence occurred in 1 Univers Revers (2.5%) and 2 Stryker Perform (4.3%) ( P = 1.000); all stabilized without progression or need for revision. One of the Stryker Perform cases demonstrating subsidence also exhibited a minor stem shift, corresponding to 3 unique implants (6.5%) considered at risk for loosening. Conclusion There is no apparent difference in short-term risk for loosening between the Stryker Perform and Arthrex Apex Univers Revers short stem designs in rTSA. Remodeling patterns differed by zone, which may reflect the differing stem designs.