Son had a unilateral (one side) pars fracture. We found a sports PT about an hour from our house and the owner had seen the injury numerous times in rotational athletes. My son was in a brace for approximately 12 weeks and was not able to swing for 5 months. He followed all the instruction of his therapist and never missed the at home work he was prescribed in between (core exercises). A year later he has been playing with no restrictions at a high level with zero pain and zero flareups. He continues to keep his core strong, wears a weight belt when performing squats and deadlifts, and he makes sure to keep proper form when lifting.
There's also an excellent podcast out there discussing this injury by MLB recommended Dr. Watkins that is very informative.