Is it permissible for a patient with a disc prolapse to pray sitting if he is unable to pray standing to avoid pain and the impact of movement on his spine?

Standing in the obligatory prayer is a pillar without which the prayer is not valid, except in cases of inability. If the pain is slight and bearable during bowing (ruku') or prostration (sujud), then praying on a chair is not valid. However, if the pain is severe and difficult to endure, then it is permissible to pray on a chair, indicating for bowing and prostration, with the indication for prostration being lower than that for bowing.