A rotator cuff tear is a tear in the tissues connecting muscle to bone tendons around the shoulder joint. Having a torn rotator cuff can be a painful experience and most patients prefer to have the least invasive surgery as possible. If the measurement you are giving me is correct the rotator cuff is probably not repairable. Retraction of that amount generally can’t be fixed with open or arthroscopic means. If it is 8 mm instead of cm then either method would work just fine.