There could have been emergency cases tying up the operating room he had scheduled, and had to give way for. He could have been waiting for the right amount of nurses or anesthesia guys to have on hand so your husband had the right amount of help. After waiting for emergencies to clear they MUST scrub that room like the queen is coming, due to how easily bones can get infected.
I am sorry you had to wait so long. Waiting is very hard whether its for ice cream, or a loved one. I am glad your hardest hours are over. Now ...let the healing begin!