Is testicular atrophy happened 4 years ago due to tesitcular torsion curable?

If "curable" means whether the atrophic testicle will return to normal size, the answer is no: it won't happen. It's harder to know whether it is still a functional organ, i.e. producing sperm (probably not) or testosterone and related hormones (possibly, yes). If your concern is cosmetic -- how your scrotum looks and feels -- a testicular prosthesis is a consideration. See a urologist.