CLINICAL, FUNCTIONAL, AND RADIOLOGICAL OUTCOMES OF INVERTED-BEARING REVERSE SHOULDER ARTHROPLASTY AT MINIMUM TWO-YEAR FOLLOW-UP

Inverted-Bearing Reverse Shoulder Arthroplasty (IB-RSA) is an alternative reverse bearing construct characterized by an ultra high molecular weight polyethylene glenosphere combined with a CoCr metallic humeral liner. This concept was designed both to minimize bearing wear as well as reduce the potential for scapular notching seen with more traditional-bearing RSA systems. This study reports on clinical outcomes, functional scores, pain scores, and radiographic incidence of scapular notching in a series of IB-RSA at a minimum of two year follow-up. A retrospective study of patients who underwent primary IB-RSA between 2016–2019 was performed. At two years minimum follow-up, patients were evaluated clinically for DASH score (DS), American Shoulder and Elbow score (ASES), EQ-5D Health Questionnaire (EQ-5D), Global Rating of Change score (GRC), Single Assessment Numeric Evaluation score (SANE), pain, and active range of motion. Presence and grade of radiographic scapular notching was assessed using the classification of Sirveaux. Overall, 56 consecutive patients were assessed at a mean post-operative followup of 36.8 months (range, 24.0–72.0 months). IB-RSA exhibited high patient-reported outcomes including DASH (12 +/−6), ASES (86 +/− 15), GRC (4 +/−1), and SANE (84 +/−11). Scapular notching was radiographically present in 20 (38%) patients (fourteen grade 1, six grade 2), with all cases showing evidence of mechanical notching while no (0) grade 3 or 4 cases were observed. The presence of scapular notching did not influence on clinical outcome scores including DASH, ASES, EQ-5D, GRC, and SANE (P=>0.05). Pain scores (P = .73) and active range of motion (P = .86) did not significantly differ between groups. IB-RSA demonstrates high patient-reported and functional outcome scores at a minimum of two years follow-up. The additional lower incidence of advanced scapular notching may indicate an advantage of this implant's design as well as the inversion of bearing composition in our series.