Horse Care – From the Hip
Early detection and a strict recovery regimen can help improve return from pelvic fractures
story by Hope Ellis-Ashburn
Pelvic fractures account for approximately 0.5-4.4 percent of all fractures seen in racehorses, making a review of their epidemiology a worthwhile endeavor. Remarkably, a high percentage of pelvic fractures are secondary to stress fractures or fatigue fractures, rather than resulting from trauma. The good news is that many horses suffering from pelvic fractures not only survive the injury but can also return to athletic careers.
Katy Dern, DVM, MS, DACVS (LA), a surgeon at Rood and Riddle Equine Hospital in Lexington, Ky., said that the most common types of stress-related pelvic fractures seen in racehorses are ilial and ischial stress fractures. She adds that the best-case scenarios are when these types of fractures are detected early, often first presenting as a hind-limb lameness.
At this early stage, a diagnostic lameness exam is performed. Lameness resulting from pelvic stress fractures cannot be blocked, an important clue for further examination. The next diagnostic step is usually nuclear scintigraphy or a bone scan after the intravenous injection of a radionucleotide.
“We see increased radiopharmaceutical uptake or a ‘hotspot’ in the area of the pelvis,” Dr. Dern explained.
The corresponding area of the pelvis is then imaged using ultrasonography, radiographs or both to determine the exact location of the fracture and the degree of displacement of the fracture segments.
There are many fractures that are only evident on bone scan. These are termed “stress fractures.” Dr. Dern said that these early-detection fractures are the result of accumulated stress on the bone, leading to micro-damage that further leads to structural failure.
There are specific parts of the pelvis that are more likely to fracture than others, and they tend to occur in the same places regardless of the cause (see diagram). The ileal wing is the most common, followed by the ischium and the ileal shaft.
“The least common is the acetabulum,” Dr. Dern said. “The acetabulum is the part of the pelvis that makes up the coxofemoral or hip joint. It’s good that it is the least common location because it’s also associated with a poorer prognosis for a return to racing.”
While there is not a good surgical treatment for pelvic fractures due to musculature and the forces applied on the pelvis, many horses will heal with a period of strict stall rest.
“When you look at the horse, probably their most notable muscle group is their hindquarters. And those are what is pulling the fractured segment apart every time they move,” Dr. Dern explained. “For this reason, we don’t recommend even hand-walking pelvic fracture patients.”
After 60 days of stall rest, patients are reevaluated, often with a lameness exam and ultrasonography. Ultrasonography allows the veterinarian to determine whether a callus is forming, indicating the stability of the fracture. Although healing time varies, one study showed that the median time for Standardbreds to return to racing following a pelvic fracture is six months.
While horses with stress fractures will most likely return to racing, patients with fractures that are unstable or involve the coxofemoral (hip) joint are sometimes so in pain that euthanasia is the only option.
“A return to athleticism is one thing, but it is not our be-all, end-all situation in any type of horse,” Dr. Dern said. “When we have involvement of the hip joint and [questionable] stability of the hip joint itself, some of these horses won’t even get sound enough to be comfortable in the pasture.”
Dr. Dern elaborated on factors such as the configuration of the fracture and its location in the pelvis as being determinants of how sound the horse can eventually become.
“Some of them, based on their fracture configuration—you know there is a chance that we can get a racehorse out of this or just a happy horse out of this,” she said.
Euthanasia becomes the only option when it is impossible to achieve a comfort level such that the horse can bear enough weight on both limbs to prevent support-limb laminitis.
Indicators to Investigate
Dr. Dern said that horses who are not training well are often first seen by track veterinarians who rule out any basic reasons for their performance. They also sometimes see horses who are slightly off, perhaps with a lameness that isn’t showing improvement with rest. These horses are then referred for additional workup. Dr. Dern credits the observant eyes of trainers and trackside veterinarians for these early saves and for seeking out timely treatment to prevent this scenario from worsening. But, she said, sometimes it is more complicated.
She elaborated that pelvic fractures in Thoroughbreds are sometimes known as “starting gate injuries” because breaking from the gate can be the most profound use of a horse’s gluteal musculature. Sometimes this ultimate exertion also occurs during a race. But, she said that the injury results from something that is more than instantaneous, resulting instead from a silent buildup of micro-damage over time.
However, the behavior of some racehorses can make early detection difficult. Those who are especially enthusiastic about their job can make early signs difficult, if not impossible, to see.
“They can override subtle signs of lameness for a long time, especially if they are training at a very high level,” Dr. Dern said. “Even in the most well managed barns, occasionally we will see one that breaks [its pelvis] pushing out of the starting gate.”
In effect, the horse’s behavior concealed the early warning signs even from well trained eyes.
Once the injury has been diagnosed, a gradual retraining of the musculoskeletal system is recommended following the mandatory two months of stall rest.
Unlike rehabilitation from other types of fractures that incorporate turnout and other types of movement to encourage stress remodeling, pelvic fractures require careful handling to prevent the large muscle groups involved from displacing the fracture. Instead, after imaging suggests that the horse is ready, hand-walking and, later, small paddock turnout are often be the first steps to a comeback.
Additional rest is required for horses who are not yet showing a callus over the top of the bone at the two-month mark.
A Rare Occurrence
Dr. Dern explained that the big caveat with pelvic stress fractures—and why trainers and veterinarians become concerned despite generally successful outcomes—is the risk of the fracture becoming displaced and severing the nearby iliac artery, resulting in a massive hemorrhagic event. Horses can die from this type of occurrence.
“There is no way to prevent this,” said Dr. Dern. “During their recovery period, they can take a wrong step, goof around in the stall or move wrong during shipping, and they can sever the iliac artery. We have no way to reach or fix this.
“For this exact reason, we don’t recommend shipping horses with displaced pelvic fractures. We will often keep them in one location until we feel the fracture is stable enough to make damage to the iliac artery less likely.”
The risk of catastrophic fracture displacement and artery rupture also means that clinicians tread a fine line between keeping the horse comfortable enough to decrease the risk of support-limb laminitis, but not so comfortable that it moves around excessively in the stall.
When a Performance Career Isn’t Possible
While many horses recover from pelvic fractures and make a successful return to racing, others do not. Dr. Dern reiterates that while a return to an athletic career may not be possible for some, many of these horses can still go on to enjoy success as breeding stallions, broodmares, or even pets. An evaluation from a veterinarian of a horse’s comfort level and ability to move three to four months out from the initial injury will often let you know what their future comfort level and performance expectations will be.
While it may not be possible to entirely prevent pelvic fractures, Dr. Dern advises not ignoring subtle signs of lameness or a reluctance to perform. Instead, back off from training, have these issues evaluated early, and, if necessary, take more aggressive diagnostic steps. Catching the fracture when it is simply a stress fracture and before any displacement has occurred is the best possible situation.
Even then, she said, it can be tricky, as pelvic fractures can be easier to diagnose when the lameness is in one hind limb, as opposed to those with bilateral stress remodeling where the horse is often simply not training well or not performing up to its potential. Regardless, early detection is key. HB
Hope Ellis-Ashburn is a freelance writer living in Tennessee. To comment on this story, email us at email@example.com.