This won't help your son out in the near term but long term it may be a better way to fix(instead of constantly treating) the back injuries.  I used to go to the chiropractor when I played football in H.S.. After high school I continued to lift weights and have started to help out some 14 to 18 year olds. Is what I've found is it can take up to 8 months to get the posterior chain(every muscle on the backside of your body from the shoulder blades down to the knees) up to acceptable levels for some of the more gifted athletes. We do lots of box squats, dead lifts, good mornings, lots of ab work, and reverse hyperextensions(http://www.westside-barbell.com/reverse-hyper/).  I have nothing against chiropractors but if more people knew what the r. h. machine was and what it could do for you there would be less of them.  I think you could build your own pretty easy.  J. R.