In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
Answering your question, Dar Al-Ifta Al-Misriyyah, states:
It is permissible for a sick person, who is unable to stand up, to offer prayers while sitting on a chair. If unable to prostrate while seated, he should pray while sitting on the ground. And if he is neither able to bow nor prostrate, then he can perform these actions while sitting on a chair.
Almighty Allah knows best.