Suggest Treatment For Balance Problem

I HAVE LUMBAR FUSIONS FROM L4 - S1. There is the possibility that I will have to undergo another fusion between L3-4. What part of the body does this area of the spine control. I am having problems with my balance but I am also scheduled to have bilateral knee replacement. To now confuse the issue, my neurosurgeon performed a craniotomy on the upper left side of my brain in 2012. He did a recent MRI and there was no indication of any atrophy. He was proud to show me the screws were he screwed my skull back together. I am 69 years old and as long as doctors can cut me open and screw me back together I am fine. There is just this balance thing to the right side as I walk. I have also had my right shoulder replaced with titanium ball and rod almost to my elbow. (reverse shoulder procedure) I worked too hard too long.