Modular baseplate augmentation: a simple and effective method for addressing eccentric glenoid wear

Abstract

Background: Augmented baseplates can be effective at addressing eccentric glenoid wear in reverse total shoulder arthroplasty. However, these implants often come in a limited number of predetermined shapes that require additional reaming to ensure adequate glenoid seating. This typically involves complex instrumentation and can have a negative impact on implant stability. Modular baseplate augmentation based on intraoperative measurements may allow for more precise defect filling while preserving glenoid bone. The purpose of this investigation was to assess the stability of a novel ringed baseplate with modular augmentation in comparison with nonaugmented standard and ringed baseplate designs.

Methods: In this biomechanical study, baseplate micromotion was tested for 3 constructs according to the American Society for Testing and Materials guidelines. The constructs included a nonaugmented curved baseplate, a nonaugmented ringed baseplate, and a ringed baseplate with an 8-mm locking modular augmentation peg. The nonaugmented constructs were mounted flush onto polyurethane foam blocks, whereas the augmented baseplate was mounted on a polyurethane block with a simulated defect. Baseplate displacement was measured before and after 100,000 cycles of cyclic loading.

Results: Before cyclic loading, the nonaugmented and augmented ringed baseplates both demonstrated significantly less micromotion than the nonaugmented curved baseplate design (81.1 μm vs. 97.2 μm vs. 152.7 μm; P = .009). After cyclic loading, both ringed constructs continued to have significantly less micromotion than the curved design (105.5 μm vs. 103.2 μm vs. 136.6 μm; P < .001). The micromotion for both ringed constructs remained below the minimum threshold required for bony ingrowth (150 μm) at all time points.

Conclusions: In the setting of a simulated glenoid defect, locked modular augmentation of a ringed baseplate does not result in increased baseplate micromotion when compared with full contact nonaugmented baseplates. This design offers a simple method for tailored baseplate augmentation that can match specific variations in glenoid anatomy, limiting the need for excessive reaming and ultimately optimizing the environment for long-term implant stability.

Keywords: Augmented baseplate; biomechanical study; eccentric glenoid wear; glenoid bone loss; implant stability; micromotion; modular augmentation; reverse total shoulder arthroplasty.