Fractured

I needed to look up greenstick fracture in the dictionary. Just below it is the entry for grenade-thrower's fracture, defined as "fracture of the humerus caused by muscular contraction, as in throwing a grenade."

Does one throw a grenade in a manner unlike one throws anything else? Is the muscular contraction related to the throwing action per se or to the panic one feels that the object one is about to throw may explode in one's hand?

Who had the honour of naming this variety of fracture? Why not "Molotov-cocktail thrower's fracture"? Or "picked-up-debris-in-the-driveway-that-turns-out-to-be-a-dead-animal-so-fling-it-away-in-a-hurry-thrower's fracture"?