Stress shielding of the Univers Revers system in reverse shoulder arthroplasty is minimal and does not progress substantially from short- to midterm follow-up.

Abstract

The purpose of this study was to compare short- to midterm signs of stress shielding with an inlay press-fit reverse shoulder arthroplasty (rTSA) humeral component. A retrospective review was conducted on primary rTSAs with a minimum 5-year follow-up that were implanted with a press-fit 135° inlay humeral component (Univers Revers and Revers Apex; Arthrex, Inc.) designed to achieve metaphyseal fixation. Patient-reported outcomes (PROs) and range of motion (ROM) values were collected preoperatively and compared with 2 and 5 years postoperative values. Radiographic signs of stress shielding, including cortical thinning, radiolucent lines, calcar osteolysis, and greater tuberosity (GT) resorption, were assessed and compared between 2 and 5 years postoperatively. One hundred thirteen patients with a mean age of 68 ± 6.6 years at the time of surgery met the study criteria. There were no differences in ROM or PROs between the 2- and 5-year postoperative time points (P > .05). Partial calcar osteolysis was observed in 15% of the patients at 2 years and 24% at 5 years, with no statistical difference (P = .093) between the time points. No cases of complete calcar osteolysis were observed at either time point. Partial GT resorption was observed in 5.4% of the cases at 2 years, which increased to 9.8% at 5 years (P = .207). There was no case of complete GT resorption at either time point. Bony adaptive changes were classified as low in 91% of cases at the final follow-up, and no stems were considered as "at risk for loosening." Stress shielding appears to be minimal at midterm follow-up after press-fit fixation of the Univers Revers, a 135° rTSA humeral component designed for metaphyseal fixation. Partial proximal bony resorption was uncommon at short-term follow-up and may progress slightly at midterm follow-up, but complete resorption was not observed. Furthermore, ROM and PROs reached at short-term follow-up are maintained at midterm follow-up, suggesting that the impact of these bony changes is not clinically important.