University of Florida veterinarians successful in rare equine hip surgery

August 13, 2018

A femoral head ostectomy in a horse? Not a problem, since the patient in question was a miniature horse and able to benefit from a surgery normally used in even smaller companion animals.

Rico one year after surgery with large animal surgery resident Dr. Andrew McClain at UF. (Photo courtesy of Dr. Taralyn McCarrel/University of Florida)Rico, a miniature horse, arrived at the University of Florida (UF) last year after a sustaining a dislocated hip.

“Rico was found down and non-weight-bearing lame last spring in a field,” says Taralyn McCarrel, DVM, DACVS-LA, an assistant professor of equine surgery at UF, in a university release. “His veterinarian diagnosed a dislocated right hip and contacted us to see what we would do and what it might cost.”

Although it was unclear what had caused Rico's injury, Dr. McCarrel says trauma of some kind was suspected.

Rico's veterinarian, Jennifer Miller, DVM, said his injury was not one she'd seen often, and “certainly not in a full-sized horse.”

A bonus for Rico and his family: At the time Dr. Miller responded to Rico's owner's call, she had a UF veterinary medical student working with her on a clinical rotation. The student was aware of an internal fund that was sometimes used to offset the cost of veterinary care in certain equine cases for teaching purposes and in cases of financial hardship on the part of the owner.

Dr. Miller knew that Rico's owner, Shelby Lewis, a college student, had limited funds, and that the type of surgery that might typically be conducted to fix the hip joint and hold it in place in foals with similar injuries would have been cost-prohibitive. She relayed the situation to Dr. McCarrel, who was able to obtain permission from UF Veterinary Hospital administrators to offset some of Lewis' costs through the Boone Memorial Fund.

A plan of action, tweaked for a horse

Dr. McCarrel researched her approach, delving into the small animal literature and limited equine literature to prepare for a femoral head ostectomy in Rico-a procedure seldom performed in horses.

“I'd never done one before, but I got as much information as possible about the different aspects of the procedure,” says Dr. McCarrel. “One of the important things that was emphasized was that if an animal has good muscle mass, that's a positive. So that boded well for him.”

Rico still had good muscle mass because he came in for surgery soon after his injury, she says, adding that in long-standing cases, the muscles become small and weak due to lack of use from pain.

Dr. McCarrel was mostly concerned about accessing Rico's hip joint with minimal trauma, as the joint in a mini horse is much deeper than in a dog due to the very muscle mass that would help him retain strength in his recovery.

“As equine surgeons, we don't typically approach the hip joint,” says Dr. McCarrel.

The femoral head ostectomy involves cutting and removing the top part of the femur. This eliminates the hip joint and transfers weight bearing to the muscles of the limb until a pseudoarthrosis forms through extensive physiotherapy, she says.

“Due to the depth of the joint and the approach needed to access the area, there is a risk of the incision falling apart after surgery due to fluid accumulation,” says Dr. McCarrel. “Therefore, Rico had a drain placed at surgery to remove excess fluid from the incision.”

Rico's road to recovery

The drain was removed several days later and Rico's incision healed without complication. Rico went home about one week after his surgery, with instructions for his owners to conduct physical therapy in the form of passive range of motion of his leg daily for two weeks. After that, the passive range of motion exercises continued along with forced walking, and he was eventually allowed in a small area daily.

Lewis admits the process of recovery was not easy for her or for Rico.

“When he first came back, I wasn't sure I'd have enough time, but I had a friend who helped me work with him,” says Lewis. “About six months ago, I started taking him swimming, and that has also helped him.”

Just over a year after his procedure, he shows little sign of the trauma he endured. “He's just my little angel,” says Lewis.