Lucky, ZooMontana’s bighorn sheep, isn’t living up to his name.

On Wednesday, the 1-year-old zoo resident broke the humerus in his right, front leg into five piece. On Saturday afternoon, surgeons at Montana Equine Medical and Surgical Center in Three Forks spent four hours repairing the damage to the bone.

What complicated the surgery, said Peter Heidmann, head veterinarian at Montana Equine, was that the head of the humerus — near the sheep’s shoulder — was dislocated.

“The muscles contract, which makes it difficult to replace it back into the scapula,” Heidmann said by phone.

Dr. Jack Schneider served as the head surgeon for the operation and Dr. Al Flint was surgical assistant, said Heidmann, an internal medicine specialist who acted as anesthesiologist.

The surgeons put two large bone plates into the humerus, the more technical part of the operation. More time consuming was the effort to reposition the dislocated bone, Heidmann said.

Lucky first arrived at the zoo last June. A rancher found the sheep kid in the Gardiner area, and the Montana Department of Fish, Wildlife and Parks picked up the animal and delivered it to MontanaZoo.

The bighorn sheep lives in a spacious enclosure at the zoo constructed especially for bighorn sheep.

Zoo officials told Heidmann they weren’t certain how the injury occurred.

“They don’t know how it happened, and he’s not talking,” the veterinarian said.

Lucky first appeared lame on Wednesday, but because the pieces of the bone stayed perfectly aligned, the fracture remained invisible, Heidmann said. A follow-up X-ray revealed the injury and the zoo contacted Montana Equine.

By Saturday evening Lucky was back in his stall, off anesthesia and gradually recovering his strength. The biggest question that remained, Heidmann said, was how damaged the leg’s nerves were at the time of the injury and whether they will fully heal.

Another question is whether a nutritional deficiency contributed to the injury of the wild animal, the vet said.

“There’s no evidence of that,” Heidmann said. “His bones are in really good shape.”