Disclaimer: I have absolutely no access to specific information about this injury. All of my assumptions are based only on the information publicly available to everyone, which isn't much. This article is all educated guesses and a somewhat-informed medical opinion based on assumptions.
Ike Taylor's arm met Lawrence Timmons' helmet and, not surprisingly, LT's helmet won. We all got to witness what happens when the human machine is subjected to forces beyond its tolerances. For those of you who haven't seen the replay, it's pretty graphic and I wouldn't recommend watching it if you're squeamish about those types of things. Ike's arm is clearly fractured, and the Steelers are left to try to pick up the pieces of an already-questionable defensive backfield.
I'm going to make a wild guess and say that both of the bones in Ike's forearm, the radius and the ulna, were fractured. I think that's a pretty safe assumption based on what we saw on the replay. The fracture appears to be mid-shaft, or diaphyseal for those who like medical jargon. Also, based on the amount of movement we saw after the fracture, it's almost certain that this is a displaced fracture; meaning that the bones were no longer lined up in their original positions immediately after the play and until being reset. Additionally, I didn't see any bones poking through the skin so this isn't an open fracture, it's a closed fracture. That's a good thing because there's a lower chance of infection.
With a displaced fracture like this, it's reasonable to be concerned about complications. For this specific injury, the biggest complication you'd worry about would be damage to a nerve or artery in the forearm. Based on the fact that Ike returned to the field and was comfortable on the sideline during the latter parts of the game, I think it's safe to say there were no vascular injuries in his case. It's possible there might be some nerve damage that would affect Ike's ability to move his hand, but it doesn't appear this will be a problem. It's just not terribly common for fractures in this location.
So what does a closed, displaced, diaphyseal, both-bones fracture of the forearm mean for Ike's season and career? It's not as bad as the replay looks, fortunately. It's certainly very dramatic to watch happen in HD and slow motion; but Ike's season shouldn't be over. He's definitely going to need surgery to realign the bones and to fix them in place with some kind of implants, usually metal plates and screws. This is called open-reduction internal fixation.
Barring complications from said surgery, he should be recovered in three months' time. In fact, one study in 1975 that looked at radius and/or ulna fractures managed like this found that more than 95% of fractures were healed at two months. It's important to note that this study included both-bone fractures with isolated fractures of the ulna or radius, so it can't be used as an exact guideline for both-bone fractures. It is, however, a good estimation of what to expect. At that point (2-3 months after surgery) he should be able to return to contact sports if he wears a brace. The brace should stay on for at least six weeks.
I'd anticipate Ike to be put on the IR designated-to-return list, and for him to be out 2-3 months. I would guess that the Steelers are waiting to see how his surgery goes before making any decisions. Again, barring any complications, we should all get the chance once more to hear from our more passionate comrades about how bad Ike Taylor is before this year is over. Maybe Mike Tomlin could ask the surgeon to realign his radius juuust soo and cure Ike's case of the dropsies. I tried searching the literature for case reports of surgical management for the slipsies, dropsies, and stone hands, but I couldn't find anything.