Figure 4.

Scaling and definition of the glenoid inclination/version (${\alpha }_{\mathrm{GI}}$ and ${\alpha }_{\mathrm{GV}}$). The scapula frame $\{{\widehat{x}}_s{\widehat{y}}_s{\widehat{z}}_s\}$ is attached to SN and is defined according to Eq. (15). The ${\alpha }_{\mathrm{GI}}$ is defined in ${\widehat{x}}_s{\widehat{z}}_s$ plane where the two points IG and SG are projected (white circles). It is defined as the angle between the ${\widehat{z}}_s$ and a vector passes through the two projected points of IG and SG. The ${\alpha }_{\mathrm{GV}}$ has a similar definition, but in the ${\widehat{x}}_s{\widehat{y}}_s$ plane and through projections of PG and AG. The adaptation of ${\alpha }_{\mathrm{GI}}$ and ${\alpha }_{\mathrm{GV}}$ results in a scaled GC point that modifies the cone of the stability constraint (Eq. 12).