Clinical results of bony increased-offset reverse shoulder arthroplasty (BIO-RSA) associated with an onlay 145° curved stem in patients with cuff tear arthropathy: a comparative study.

BACKGROUND: The main limits of the Grammont design reverse shoulder arthroplasty (RSA) are loss of external rotation and scapular notching. They can be addressed with glenoid or humeral lateralization. The aim of the study was to compare outcomes of lateralized bony increased-offset RSA (BIO-RSA) vs. standard RSA in patients with an onlay 145° curved stem. METHODS: A comparative cohort study of 29 standard RSAs and 30 BIO-RSAs was performed. At 2 years postoperatively, Constant score, American Shoulder and Elbow Surgeons score, visual analog scale score, range of motion, and radiographs were evaluated. After comparison between the groups, patients were analyzed considering patients younger and older than 65 years. RESULTS: All parameters significantly improved after surgery in both groups. Postoperatively, the 2 groups did not show any clinical and radiographic differences (P > .05). In patients <66 years, BIO-RSA showed a significantly higher value of external rotation (49° ± 12° vs. 30° ± 19° [P = .025], elbow at side; 81° ± 17° vs. 56° ± 22° [P = .016], elbow at 90° of abduction) and a positive trend for all other parameters (P > .05). In patients >65 years, standard technique showed a positive trend for all the parameters (P > .05). No other significant differences were found. CONCLUSIONS: At 2 years of follow-up, the use of standard RSA or BIO-RSA in an implant with an onlay 145° curved stem provided similar outcomes. The humeral lateralization alone is sufficient to decrease notching and to improve external rotation. BIO-RSA increases external rotation in patients between 50 and 65 years old. Glenoid bone graft in RSA has a high incorporation rate (completed in 90%).