A horse is pretty much built to the limit of it’s tolerance – with its muscular body, and relatively skinny legs, it really can’t be much bigger than it is. As such, when a horse is running, turning, jumping, pivoting, or otherwise exercising, it’s putting stresses on its limbs that are right up to the maximum of what they can take. When those stresses exceed what the horses limb can take, an explosion goes off in the horse’s leg. As such, the bone not only fractures into a bunch of pieces, but blood vessels can tear, tendons can rupture, and ligaments can shear off the bone.Under such circumstances, there’s not anything left to fix. The limb of a person who had sustained such an injury would usually be amputated – that’s something that’s rarely done in horses. Thats when you have to put them down
It is possible, but it depends on the horse, the break itself (full break or fracture), on the care the vet and owner can provide, and which leg. A front leg bears twice as much weight as a back leg. A big problem when healing broken legs is that the adjacent leg has to compensate for the weight, and can lead to founder in the weight bearing hoof. This is why we had to put my horse down - she foundered in one front hoof, and then while in the hospital the other hoof foundered, and there was no recovering from having both.
So short answer is yes it's possible. Long answer is it's very complicated and very touch and go for a while. Expect bed sores, weight loss, and a long recovery period.