Costo-sternal joints

Hi all,
This is Noemi.

I am trying to reproduce a scoliosis by Anybody 7.1 and an articulated AMMR_Thorax. In the latter the articulations of the ribs through deformable costal cartilages and synovial joints to the sternum where modeled as 6dof joints for all ribs.

My problem is when adjusting the vertebrae to get the exact spine conformation of a scoliotic patient, the ribs are not anymore aligned with the correspondent part of sternum.
Do you know there is a way to manipulate the distance between the sternum and the ribs, by using the costo-sternal joints for example? Or is there a way to define a distance between 2 parts to keep it fixed? The aim would be making the software to adjust the ribs by itself.

Thanks in advance.
Kind regards,
Noemi