Effect of glenosphere diameter and lateralization in primary reverse shoulder arthroplasty: a randomized clinical trial

Abstract

Background

Within reverse total shoulder arthroplasty (RSA), prior studies have suggested that smaller glenosphere diameters may result in higher rates of scapular notching and polyethylene wear, while lateralized glenospheres may allow for better range of motion (ROM); however, supportive data remains limited. Therefore, the purpose of this study was to report the outcomes of a prospective randomized clinical trial comparing 4 different glenosphere configurations based on diameter and lateral offset.

Methods

Between 2016 and 2020, 113 primary RSAs with a diagnosis of either rotator cuff tear arthropathy (n = 48, 42%), irreparable rotator cuff tears (n = 22, 19%), or primary glenohumeral osteoarthritis with subluxation or glenoid bone loss (n = 43, 38%) were enrolled into a blinded prospective randomized clinical trial. The mean age of the patients included in the study was 73 ± 7 (range, 50-89) years, and 58 (51.3%) were males. All procedures were performed by two surgeons utilizing the ReUnion RSA system (Stryker, Mahwah, NJ, USA). Patients were randomized into four possible groups based on the diameter and lateral offset of the glenosphere implanted: 36 mm diameter with 2 mm (n = 34, 30.1%) or 6 mm (n = 28, 24.8%) of lateralization and 40 mm diameter with 2 mm (n = 29, 25.7%) or 6 mm (n = 22, 19.5%) of lateralization. Outcomes collected included pain, active ROM, strength, satisfaction, patient-reported outcome measures (PROMs), complications, reoperations, and revisions. PROMs included the Oxford Shoulder Score, the American Shoulder and Elbow Surgeons, and the quick Disabilities of the Arm, Shoulder and Hand questionnaire. All patients were followed for a minimum of 2 years.

Results

With the numbers available, glenosphere diameter and lateralization resulted in no differences in pain, ROM, strength, satisfaction, and PROMs at 1 year, 2 years, or final follow-up (All P > .05). However, all 3 complications (10.7% vs. 0% vs. 0% vs. 0%; P = .025) and 2 revision surgeries (7.1% vs. 0% vs. 0% vs. 0%; P = .103) occurred in males, with the 36 + 6 cohort.

Conclusions

Using this particular RSA design, implantation of glenospheres with 36 mm or 40 mm of diameter and 2 mm or 6 mm of sphere lateralization did not translate into significant differences when primary RSA was performed in shoulders with rotator cuff tear arthropathy, irreparable cuff tears, or primary glenohumeral osteoarthritis. However, all observed complications occurred in males with the smallest diameter and lateralized glenosphere.