This is a very good question. Both medications are anti-androgens. Androgen is a helpful anabolic hormone and deficiency might negatively impact a fusion.
However, I have had fracture patients on these medications and the fractures still healed normally so I would say there could be a theoretical impairment but probably not a clinical problem.
I am unaware of any studies to this subject but you might search Pubmed for any articles on this.
Dr. Corenman