Aseptic glenoid baseplate loosening after reverse total shoulder arthroplasty with a single prosthesis.

BACKGROUND

Early reverse total shoulder arthroplasty (rTSA) designs had high failure rates, mainly from loosening of the glenoid baseplate. The purpose of this study was to determine the incidence of aseptic glenoid baseplate loosening after primary rTSA using a contemporary medialized glenoid-lateralized humerus system and identify significant risk factors associated with loosening.

METHODS

A total of 7162 patients underwent primary rTSA with a single-platform rTSA system between April 2007 and August 2021; of these primary rTSA patients, 3127 with a minimum 2-year follow-up period were identified. Patients with aseptic glenoid baseplate loosening were compared with all other primary rTSA patients without loosening. Univariate and multivariate analyses were performed to compare these cohorts and identify the demographic characteristics, comorbidities, operative parameters, and implant characteristics associated aseptic glenoid loosening after rTSA. Odds ratios (ORs) were calculated for each significant risk factor and for multiple combinations of risk factors.

RESULTS

Irrespective of minimum follow-up, 53 of 7162 primary rTSA shoulders (31 female and 22 male shoulders) experienced aseptic glenoid loosening, for an overall rate of 0.74%. At latest (2-year minimum) follow-up, 30 of 3127 patients experienced aseptic glenoid loosening and showed significantly lower clinical scores, function, and active range of motion and higher pain scores than patients without loosening. Univariate analysis identified rheumatoid arthritis (P = .029; OR, 2.74) and diabetes (P = .028; OR, 1.84) as significant risk factors for aseptic glenoid loosening after rTSA, and multivariate analysis identified Walch glenoid types B2 (P = .002; OR, 4.513) and B3 (P = .002; OR, 14.804), use of expanded lateralized glenospheres (P = .025; OR, 2.57), and use of augmented baseplates (P = .001; OR, 2.50) as significant risk factors.

CONCLUSION

The incidence of aseptic glenoid baseplate loosening was 0.74% for the evaluated medialized glenoid-lateralized humerus rTSA system. Numerous risk factors for aseptic loosening were identified, including rheumatoid arthritis, diabetes, Walch type B2 and B3 glenoids, posteriorly-superiorly augmented baseplates, and expanded lateralized glenospheres. Finally, analysis of multiple combinations of risk factors identified patients and implant configurations with the greatest risk of aseptic glenoid loosening.