It's no trouble at all. During an Argantuan's maturation phase, the bone grows out from their internal skeleton, through the skin (protrusions) and over the skin (plates.) The plates act to reinforce the skin in various places all over the body, but they do not interlock. The protrusions are in the form of spikes of various thicknesses that protrude from the shoulders and arms....the largest coming out of the forehead. The shoulder and arm spikes are quite short and are therefore cannot be made into the larger sword-type weapons. For that the larger internal bones must be used.

If a spike or plate is damaged before hibernation, it can be regrown/repaired. White bone that has been through the hibernation of a mature Argantuan cannot be regrown, however it is incredibly durable. Only a white bone-grinder, guided by the power of a Blodhur can shape mature bone.