Utility of superior augments in reverse shoulder arthroplasty (Exactech, Equinoxe GPS) without significant glenoid deformity.

BACKGROUND

Superior augment use may help avoid superior tilt while minimizing removal of inferior glenoid bone. Therefore, our goal was to compare superior augments vs. no-augment baseplates in reverse shoulder arthroplasty (RSA) for patients with rotator cuff dysfunction and no significant superior glenoid erosion.

METHODS

A multicenter retrospective analysis of 145 patients who underwent RSA with intraoperative navigation (Equinoxe GPS; Exactech) and 3-year follow-up (mean 32 months' follow-up, range 20-61 months) who had preoperative superior inclination less than 10° and retroversion less than 15°. Patient demographics, radiographic measurements, surgical characteristics, patient-reported outcomes at preoperative and postoperative visit closest to 3 years, and adverse events at final follow-up were obtained. Operative time, planned inclination, and planned version of the baseplate were obtained. χ test was used to compare categorical variables, and Student t test was used to compare the augment and no-augment cohorts.

RESULTS

The study population consisted of 54 superior augment patients and 91 no-augment patients. The augment cohort had lower body mass index (27.2 vs. 29.4, P = .023) and higher native superior inclination (5.9° vs. 1.4°, P < .001). No difference between the augment and no-augment cohorts was found regarding age (P = .643), gender (P = .314), medical comorbidities (P > .05), surgical indication (P = .082), and native glenoid version (P = .564). The augment cohort had higher internal rotation score (4.6 vs. 3.9, P = .023), and all remaining range of motion (ROM) and patient-reported outcomes (PROs) preoperatively were not significantly different. At final follow-up, active ROM in all planes was not different between the cohorts. Regarding PROs, the postoperative Shoulder Arthroplasty Smart score was significantly higher (78.0 vs. 73.6, P = .042), and American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form score trended toward higher (83.6 vs. 77.5, P = .063) in the augment cohort. The augment cohort had a significantly lower proportion of patients who planned to have superior baseplate tilt (1.9% vs. 14.3%, P = .012) and had greater mean inclination correction (6.3° vs. 1.3°, P < .001), compared with the no-augment cohort. Adverse events were rare, and there was no significant difference found between the augment and no-augment cohorts (5.6% vs. 3.3%, P = .509).

DISCUSSION

Superior augmented baseplate in RSA with minimal superior glenoid erosion is associated with similar ROM and adverse events with somewhat improved postoperative PROs compared with nonaugmented baseplates at the 3-year follow-up. Additionally, superior augments resulted in a greater proportion of baseplates planned to avoid superior tilt, and trended toward shorter operative times. Further investigation of long-term glenoid baseplate loosening is imperative to fully understand the cost-effectiveness of superior augments in the setting of minimal glenoid deformity.