What can a doctor do about a broken rib? I've not heard of a "cast" for rib fractures.

Give it time. There is no specific treatment required for a broken rib. These heal in approximately 4-6 weeks.
Depends. It depends on if the broken rib needs surgery or not. Certain rib fracture patterns (multiple consecutive rib fractures/etc) really benefit from surgery. There is good evidence in the scientific literature supporting this. Single rib fracture(s) are typically treated with pain medication and use of the incentive spirometry device.
Pain control. Mostly, the md can provide pain control thru meds. Otherwise, not many options. Strapping or wrapping of rib fractures has fallen out of favor secondary to potential breathing and/or pneumonia concerns. Tight wrapping about the rib cage does help pain, but the wrapping should not be left on 24 hrs. Sleeping almost sitting up with a few pillows helps with night time pain.

Related Questions

At my last check up, I forgot to tell the doctor about rib fracture. Is that ok?

No it is not. This rib frature from truma, could cause lung problems, you should tell him please.Thanks. Read more...
Depends. Is it an old fracture or a newer one? How do you know you have one? If its an older fracture, it should be ok. If its a newer one, you should mention it to your doctor. Read more...