Mid-term outcomes of reverse shoulder arthroplasty using the alternative center line for glenoid baseplate fixation: a case-controlled study

Abstract

A critical step in reverse shoulder arthroplasty (RSA) is glenoid baseplate fixation. In cases of glenoid bone loss, use of the anatomic glenoid center line may not provide sufficient bone support for fixation. Anteversion along the alternative center line is a described method for achieving baseplate fixation in these cases. However, concern remains regarding negative consequences in functional outcomes and complications. The purpose of this study was to compare the outcomes of RSA using the anatomic or alternative center line. We performed a retrospective case-controlled study of patients who underwent RSA between November 2006 and August 2017, performed by a single surgeon, with a minimum of 2 years' follow-up. Patients treated with the anatomic center-line technique for baseplate fixation were matched 3:1 based on sex, indication for surgery, and age with patients treated with the alternative center-line technique. Patient-reported outcome measures (PROMs), active range of motion, and the ability to perform functional tasks of internal rotation were compared. Evaluations of the most recently obtained radiographs focused on acromial fractures, scapular notching, and glenoid loosening. A total of 88 patients (66 in anatomic center-line group and 22 in alternative group) participated in the matched analysis, with a mean age of 74.2 years (range, 58-89 years) and mean follow-up period of 53 months (range, 24-130 months). At the final follow-up, we found no significant differences in PROMs, including the Simple Shoulder Test score (P = .829), American Shoulder and Elbow Surgeons score (P = .601), visual analog scale pain score (P = .068), and Single Assessment Numeric Evaluation score (P = .674). Moreover, both the overall improvements in these PROMs and all active motions and functional tasks of internal rotation were not different. No radiographic evidence of glenoid loosening was found in either group, and 2 patients in each cohort (3% of the anatomic group and 9% of the alternative group) experienced an acromial fracture. Low-grade scapular notching developed in 15.2% of the anatomic group and 18.2% of the alternative center line group (P = .736). The alternative center line can be used for baseplate fixation in the settingof glenoid bone loss and leads to similar patient outcomes and functional tasks of internal rotation, as well as a low rate of complications, compared with the anatomic center line following RSA.