ISAKOS Congress 2021

2021 ISAKOS Biennial Congress ePoster

 

Lateralized Glenosphere Reverse Shoulder Arthroplasty: Inlay And Onlay Designs Have Similar Clinical Outcomes In Patients With Glenohumeral Osteoarthritis

Prashant Meshram, MBBS, MS, DNB (Ortho), Dubai, Dubai UNITED ARAB EMIRATES
Stephen C. Weber, MD, San Diego, CA UNITED STATES
Uma Srikumaran, MD, MBA, MPH, Columbia, MD UNITED STATES
Edward G. McFarland, Lutherville, MD UNITED STATES
Johns Hopkins Medical Institute, Baltimore, MD, UNITED STATES

FDA Status Cleared

Summary

For patients with glenohumeral osteoarthritis with glenoid bone loss and an intact rotator cuff who underwent RSA using a lateralized glenosphere prosthesis with a 135° NSA, there were no significant differences between the inlay and onlay groups for ROM, PROs, or complication rates.

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Abstract

Background

Whether or how the position of the humeral tray (inlay or onlay) in reverse shoulder arthroplasty (RSA) affects outcomes is unclear. The goal of this study was to compare the clinical and radiographic results of RSA systems with inlay versus onlay designs but with similar neck shaft angles (NSAs) and lateralized glenospheres.

Methods

We screened the institutional database at our tertiary academic center for patients who underwent primary RSA (with a lateralized glenosphere and a 135° NSA) by a single senior surgeon. The indication for surgery was glenohumeral osteoarthritis with glenoid bone loss (Walch classification A2, B2, B3, or C) and an intact rotator cuff from 2009 through 2017. All patients were followed for a minimum of 2 years (mean, 47 months; range, 24–123 months). The humeral tray design was inlay for 79 patients and onlay for 71. All patients underwent preoperative and postoperative evaluations, including a physical examination, radiography, and PROs (visual analog scale [VAS] for pain, American Shoulder and Elbow Surgeons [ASES] score, Simple Shoulder Test [SST], and Western Ontario Osteoarthritis of the Shoulder [WOOS] index). Clinically meaningful improvements in PROs and ROM were determined using previously reported minimal clinically important difference (MCID) values for shoulder arthroplasty. MCID values were as follows: 1.6 points for VAS pain, 13.6 points for ASES score, 1.5 points for SST, 7° for abduction, and 12° for forward flexion. No preoperative demographic characteristics, PROs, or ROM measurements were significantly different between the inlay and onlay groups (all, P > 0.05).

Results

Compared with preoperative values, both groups achieved MCIDs in ROM and PROs at final follow-up. The differences in ROM at final follow up in inlay group for mean abduction (116° vs 124°), flexion (115° vs 125°), and external rotation at 90° abduction (65° vs 60°) was neither statistically significant nor clinically meaningful than that in onlay group. Similarly, the differences in mean PROs in inlay group of VAS for pain (23 vs 28), ASES score (91 vs 86), SST (9 vs 11), and WOOS index (80 vs 78) was neither statistically significant nor clinically meaningful than those in onlay group (P > 0.05). Rates of revision (inlay, 3.8% vs onlay, 1.4%), of baseplate loosening (inlay, 2.5% vs onlay, 1.4%), of scapular notching (inlay, 5.1% vs onlay, 7.0%), of acromial stress fracture (inlay, 0% vs onlay, 2.8%), and of tuberosity resorption (inlay, 25% vs onlay, 27%) were not significantly different between groups (all, P > 0.05). The rate of periprosthetic fracture was also similar (inlay, 6% vs onlay, 4%, P > 0.05) between the two groups. Prosthetic dislocation did not occur in any patient.

Conclusion

For patients with glenohumeral osteoarthritis with glenoid bone loss and an intact rotator cuff who underwent RSA using a lateralized glenosphere prosthesis with a 135° NSA, there were no significant differences between the inlay and onlay groups for ROM, PROs, or complication rates. These findings are limited to this specific off-label indication for RSA.

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