Any slip generally means there is some incompetence in the disc which is a problem. There are some strikes against you for pars repair. Your age is one. Younger patients tend to heal better and faster although I have repaired some pars fractures in twenty-something patients with not-unreasonable results but the success rate is lower and healing slower. Disc degeneration is another problem. Disc degeneration can lead to progressive disc thinning and incompetence.
The type of each pars fracture is important. Displacement is a negative factor. Non-displaced does better. 3mm displacement is a real issue. Atrophy at the end of the fracture is another negative factor. Of course, if the fracture end is hypertrophic and non-displaced, that would be a positive for repair.
Don’t be too worried if you are not a candidate for repair but are for fusion as many of these patients are very happy with fusion results.
Normally, most insurance companies welcome a second opinion.
Dr. Corenman