I keep ornamental crabs in a marine fish tank as a hobby and once in a while the crabs will fight and rip each other's claws and legs off. They grow back at the next molt which is usually in a few months. Sometimes both claws are ripped off. They always survive to the next molt where new claws and legs reappear. That's all I'm saying. Not here to comment on the act of the original post; just stating what I've seen with regards to crabs regrowing arms and claws. Of course, not all crabs are equal.
This is from the wiki link
Effects on mortality[edit]
Florida stone crab claws served as food
Under experimental conditions, but using commercially accepted techniques, 47% of Florida stone crabs that had both claws removed died after declawing, and 28% of single claw amputees died; 76% of the casualties died within 24 hours of declawing. The claws constituted 51% of the total weight of the crabs before declawing.[8] In the wild, where declawed crabs must compete for food, mates, and shelter, and avoid predators, the mortality rate is likely to be higher. Declawed crabs survive by switching from predation to scavenging.[9] The occurrence of regenerated claws in the fishery harvest is low, with studies calculating from less than 10% (1978),[8] 13% (2006),[7] to 20% (2010).[10] Larger, older crabs generally do not survive long enough to regrow their claws, as they are near the end of their lifespan.