I guess I'd be interested to know exactly what injury your son suffered. Mine ended up with a bi-lateral pars defect. The kid had to wear a body brace to three months I think, and do PT. At the end of the three months the chiropractor ordered another MRI. In the next visit he looked at the results and told him he was released, go have fun. He still does his core exercises. the only problems he has is a stiff back if he stands for long periods of time.
Like I said, pars defect grade I, which means the vertebra has slipped 3mm or less over the one under it. Freaks me out. Of course Andre Agassi won four majors with a grade II. And you would never know anything was wrong watching him.