My father had several open heart by-p surgeries ....?

My father had several open heart by-p surgeries and following the last attempt two years ago, his rib cage won't mend. He has been told that he will need a bone graft for the rib cage but because he is a high-risk patient it has to be done in a minimally invasive way. What would be his best option for this type of surgery? Are there any clinics which are specialized in this type of surgery for high-risk patients (preferably in Canada but alternatively in the U.S.)? Thank-you.