Horse on our yard had it done for tendon tears. Didn't work and the horse is only now being ridden again after almost a year. I think she had pig stem cells. I think stem cell treatment is so relatively new that it's still in the experimental stage although some vets may advise of quite good success %. I wouldn't have it done having seen the results.
My horse had it done about 4 years ago. It did work and he was out competing (dressage) again within a year. Competed up to elementary affiliated and I decided not to push it beyond that. He has stiff days but he is happy and sound.
We had it done on our 8 (?) year old quarter horse after he tore his suspensory ligament in his front leg. He would have been grand a few months later but we noticed he had strained his other front suspensory so he was on stall rest for a few more months! He's a happy bunny now, perfectly fine, been back to schooling lower level dressage! Unfortunately our jumping career is over