BackgroundReverse total shoulder arthroplasty (rTSA) is a treatment option for a variety of shoulder pathologies, including rotator cuff arthropathy, glenohumeral arthritis, and irreparable rotator cuff tears and fractures. There has been substantial improvement in rTSA implants and surgical techniques, such as augmented baseplates that preserve bone tissue. In this study, we used three-dimensional modeling to determine the extent of bone preservation with augmented baseplates in rTSA. MethodsComputed tomography scans from 50 consecutive patients before they underwent rTSA were used to create three-dimensional models of each glenoid. The virtual positions of reverse shoulder baseplate implants followed strict parameters for adequate fixation as determined through consensus among 4 fellowship-trained shoulder specialists. Parameters for adequate fixations included 100% backside contact, neutral scapular version, and 10° of inferior tilt. The 4 baseplate options trialed on each glenoid were a nonaugmented baseplate, a small 10° half-wedge augment, a medium 20° half-wedge augment, and a large 30° half-wedge augment. The extent of volumetric glenoid bone removal and lateralization of the baseplate was calculated for each scenario. ResultsPreoperative computed tomography imaging showed a mean of 10.7° of retroversion and a reverse shoulder arthroplasty angle of 21.3°. A medium augment (20° half wedge) was determined as optimal in 29 cases, and a large augment (30° half wedge) was considered optimal for the remaining 21 cases. The use of augmented baseplates was calculated to preserve 54% glenoid bone stock (1989 ± 650 mm3 bone removal vs. 4439 ± 1636 mm3 with nonaugmented baseplate; P < .001). The surgeon-selected augmented baseplate was on average 4.1 mm lateral in comparison to the nonaugmented baseplate. ConclusionsThe use of augmented baseplates reduces the volume of bone that needs to be removed in rTSA. Furthermore, augmented baseplates result in relative lateralization of the glenosphere, which has been theorized to improve soft tissue tension and limit impingement and scapular notching. Further exploration of the impact of augmented baseplates on clinical outcomes is needed.
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