Incidence and risk factors for aseptic baseplate loosening of reverse total shoulder arthroplasty

Background: Aseptic glenoid baseplate loosening (AGBL) is a catastrophic complication after reverse total shoulder arthroplasty (RTSA). Our goals were to determine the incidence of AGBL in patients who underwent RTSA and identify risk factors for AGBL after RTSA. Methods: We analyzed 202 shoulders that underwent primary or revision RTSA using 1 implant system and evaluated baseplate loosening at a minimum 2-year follow-up. The associations between AGBL and the following variables were investigated: patient age, sex, primary vs. revision RTSA, scapular notching, use of bone graft, and type of baseplate screw fixation. Results: AGBL occurred in 6 shoulders (3.0%). The incidence of AGBL after revision RTSA (10%) was significantly higher than that after primary RTSA (1.2%; P =.014). There were significant associations between AGBL and the use of bone graft and the use of nonlocking screws. Scapular notching, glenosphere center-of-rotation offset, patient age, and sex were not associated with AGBL. Multiple logistic regression analysis showed that the use of all peripheral nonlocking 3.5-mm screws (odds ratio, 10.6; 95% confidence interval, 1.1- 39) and the use of bone graft (odds ratio, 7.5; 95% confidence interval, 1.9-30) were independent risk factors for AGBL. Conclusions: The rate of baseplate failure after primary RTSA is low (1.2%) but is significantly higher after revision RTSA (10%). Major risk factors for baseplate failure are the use of all 3.5-mm nonlocking screws for peripheral baseplate fixation and the use of a bone graft to address deficiencies in bony support beneath the baseplate.