Influence of backside seating parameters and augmented baseplate components in virtual planning for reverse shoulder arthroplasty

Abstract

BackgroundThe primary goal of this investigation was to examine the influence of a backside seating percentage variable on volume of reamed bone and contact area in virtual planning for glenoid baseplate placement for reverse shoulder arthroplasty (RTSA). The secondary goal was to assess how the option of augmented glenoid baseplate components affected reamed volume and cortical contact area of virtually positioned baseplates. MethodsNine surgeons virtually planned 30 RTSA cases using a commercially available software system. The 30 cases were chosen to span a spectrum of glenoid deformity. The study consisted of three phases. In Phase 1, cases were planned with the backside seating percentage blinded and without the option of augmented baseplate components. In Phase 2, the backside seating parameter was unblinded. In Phase 3, augmented baseplate components were added as an option. Implant version and inclination were recorded. Using CAD models, total volume of bone reamed as well as reamed cortical volume and cancellous volume were calculated. Total, cortical and cancellous baseplate contact area were also calculated. Finally, total glenoid lateralization was calculated for each phase and compared. ResultsThe mean implant version was clinically similar across phases, but statistically lower in Phase 3 (p = 0.006 compared to Phase 1, p = 0.001 compared to Phase 2). Mean implant inclination was clinically similar across phases, but statistically lower in Phase 3 (p < 0.001). Phase 3 had statistically significantly lower cancellous and total reamed bone volumes compared to Phase 1 and Phase 2 (p < 0.001 for all comparisons). Phase 3 had statistically significantly larger cortical contact area, lower cancellous contact area, and larger total contact area compared to Phase 1 and Phase 2 (p < 0.001 for all comparisons). Phase 3 had significantly greater glenoid lateralization (mean 10.5 mm) compared to Phase 1 (mean 7.8, p < 0.001) and Phase 2 (mean 7.9, p < 0.001). ConclusionsAcross a wide range of glenoid pathology during virtual surgical planning, experienced shoulder arthroplasty surgeons chose augmented baseplates frequently, and the option of a full wedge augmented baseplate resulted in statistically significant greater correction of glenoid deformity, improved total and cortical baseplate contact area, less cancellous reamed bone, and greater glenoid lateralization. Backside seating information does not have a significant impact on how glenoid baseplates are virtually positioned for RTSA, nor does it impact the baseplate contact area or volume of reamed bone.