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

The 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 total 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.

Nine 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 3 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. By use of computer-assisted design models, total volume of bone reamed, as well as reamed cortical volume and cancellous volume, was calculated. Total, cortical, and cancellous baseplate contact areas were also calculated. Finally, total glenoid lateralization was calculated for each phase and compared.

Mean implant version was clinically similar across phases but was statistically significantly lower in phase 3 (P = .006 compared with phase 1 and P = .001 compared with phase 2). Mean implant inclination was clinically similar across phases but was statistically significantly lower in phase 3 (P < .001). Phase 3 had statistically significantly lower cancellous and total reamed bone volumes compared with phase 1 and phase 2 (P < .001 for all comparisons). Phase 3 had statistically significantly larger cortical contact area, lower cancellous contact area, and larger total contact area compared with phase 1 and phase 2 (P < .001 for all comparisons). Phase 3 had significantly greater glenoid lateralization (mean, 10.5 mm) compared with phase 1 (mean, 7.8 mm; P < .001) and phase 2 (mean, 7.9 mm; P < .001).

Across 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 significantly 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.