Being very explicit now.
Here is Barbaro's story. Do not read further if easily distressed or are squeamish. Also only click on the links if you are prepared to see a horse with a broken leg and the aftermath. Barbaro was a very successful American racehorse, he won the Kentucky Derby, a huge race. A fortnight later he broke his hind leg on the track. Picture here. He was somehow bundled into the horse ambulance, God knows how since you can't persuade a horse to hop along on 3 legs even when one of his feet is clearly hanging off. As he was a valuable animal and a colt whose semen would be in demand (and because a lot of people loved him
) they decided to put him in a sling and operate on his broken leg. He endured 6 rounds of surgery - the risks each time a horse undergoes a general anaesthetic are immense. He initially seemed to cope well with the first operation, but within a week had developed abcesses and a fever. He next developed laminitis, a condition where the bones in the foot rotate - in his case as a result of keeping his weight off the broken leg. To treat the laminitis, 80% of his hoof in the non-injured leg was removed, a drastic procedure. He now had 2 legs in casts. By 6 months after his leg break, his broken leg was essentially mended but the other leg which had borne the weight was still problematic. Further surgery was prescribed, and shortly after this he developed laminitis in both front legs too. At this point he had not even one leg left to stand on. Barbaro lived the final 6 months of his life in a veterinary hospital, in extreme pain, undergoing experimental procedures. He was considered worth saving because of the value of his sperm, but the more sentimental horse lovers applauded the vets' attempts to save him, as it showed it was possible to save a horse with a broken leg. More pragmatic horse lovers agreed the kinder thing for the horse was to put him out of his misery than to prolong it. here is a picture of him in his sling.
Conversely, Mill Reef and Dubai Millenium are examples of racehorses who have broken legs and been successfully treated. Both were valuable colts who went to stud and made a lot of money. The fact remains that these horses were put through long, painful and arduous recoveries because it was worth keeping them. Outside of racing it would have been likely that the horse would have been put to sleep, even if it was a much loved pet.
Any horse, racehorse or dobbin, is a flight creature. To keep them lame and in pain is not fair on them, whatever their worth. Most horse lovers, whether they be racing fans or not, understand this principle, hence most horses are put to sleep quickly once a diagnosis of broken leg is made. To keep a horse happy and sensible when it cannot be worked is very difficult, and is often asking for trouble. My friend's horse is currently 3 months into a year long rehabilitation for a leg injury, and she is having to sedate the horse just to be able to take it out into a small field, as the horse is very tense after months in a stable and could exacerbate the injury if it ran around in delight at being free again.
Healing a broken leg is not easy in a horse, full stop.