The unstable nature of the Oov, is designed to facilitate the user to learn to control the lumbar pelvic complex. To help people to learn to control lumbar instability is one of the reasons we designed the Oov.

Osteoporosis and Scoliosis are definitely not contraindications, but may require some nuance in sizing and positioning. 
We have used the Oov with pretty much every pathology, but it does come down to how to size and position the user. There are many variations depending on the Pathology, (too many to list here) but in the course, the first morning addresses all the main pathologies and variations on positioning them.

I hope this helps and thank you for your question.

https://www.pilates.com/store/oov/

Thank you.