Why Is My Husband Leaning Severely Towards The Right?

My 89 year old husband suffered a compression fracture of L2 four months ago. He had successful surgery and 3 months of rehab. He is now home and declining. He has had Normal Pressure Hydrocephalysis (sorry for spelling) for over 10 years which makes walking very difficult.....now almost impossible. He also takes warfarin for Atrial Fib. He has just started leaning to one side or the other or the other when sitting. Today he is leaning severely to the right. What could this mean?