MRI for Equine Foot Lameness: The Sooner the Better
When your horse has unexplained lameness in the foot, you might prefer to avoid the cost and inconvenience of magnetic resonance imaging (MRI). But given the higher recovery rates horses with acute lameness experience following this diagnostic procedure, it might be a worthwhile investment, according to newly published research.

Study horses undergoing MRI due to acute lameness—beginning within the past 12 weeks—healed better than horses whose lameness had become chronic, said Drew W. Koch, DVM, resident in equine surgery in the Department of Clinical Sciences at Colorado State University’s College of Veterinary Medicine and Biomedical Sciences, in Fort Collins.

He attributed this, in part, to improvements in technology and veterinary skills. “As we’ve started to use MRI more regularly in horses, especially in cases of foot-related lameness, we’ve become more able to directly identify issues, and we’ve felt we could more accurately focus treatment,” Koch said.

Eight Years of MRI Cases

Koch and his fellow researchers examined the veterinary records of 95 horses that presented with recent (acute) or long-term (chronic) lameness in the foot and underwent MRI at either Pioneer Equine Hospital in Oakdale, California, or Colorado State University Veterinary Teaching Hospital between 2009 and 2016. Veterinarians had already localized the source of lameness to the foot using diagnostic analgesia (nerve blocks).

Study horses were mainly Quarter Horses and Warmbloods, ridden primarily in the fields of hunter/jumper, dressage, Western performance/pleasure, trail riding, eventing, barrel racing, or roping. Their MRI evaluations pointed to issues involving the navicular bone, deep digital flexor tendon (DDFT), distal interphalangeal (DIP) joint, collateral ligaments, and/or other foot structures.

Follow-Up a Year (or More) Later

When Koch and his study co-authors contacted the horses’ owners at least a year after the MRI, they found that the horses with acute lameness had improved significantly more than those whose lameness had become chronic. They had better resolution of their lameness and better return to former athletic activity.

Careful scientific analysis allowed the researchers to conclude that the improvements were not solely a result of the horses’ lameness being acute or chronic, they stated. The MRI itself made a significant difference, because treatment had been ineffective up until then. For the researchers, the MRI findings appeared to help veterinarians prevent acute cases from becoming chronic.

MRI: 3D and Multitissue

Unlike radiography and ultrasound, which give two-dimensional images, MRI allows three-dimensional imaging, Koch said. Radiography is limited to hard tissues and ultrasound to soft tissues, whereas MRI provides visibility of both.

These advantages are particularly useful in such a complex bodily region as the equine foot, which is a common site of inaccurate diagnoses, said the researchers. “Difficulties in fully assessing pathology (disease or damage) of the equine digit may lead to incomplete or inaccurate diagnoses and, thus, prescription of prolonged, ineffective, or contraindicated treatment,” they wrote.

“Because the anatomy of the digit is so complex in the horse, MRI gives this nice, broad perspective of structures that could be affected,” Koch added. “There are definitely horses out there where radiographs and ultrasound can be used to make an accurate diagnosis, which is less costly than MRI. But in cases where these modalities just aren’t connecting the severity or chronicity of lameness with what’s identified, MRI can be that final tool that really brings everything into perspective.”

High Initial Cost, but a Good Investment?

While MRI is an expensive tool, its benefits might make it a wise choice to prevent prolonged expenses over time due to poor healing, Koch said. “In horses with chronic lameness that are unresponsive to treatment, people are likely spending much more money for repeat radiographs or ultrasound, treatment, time off work, and rehabilitation, which actually ends up being a larger monetary investment long-term than if they would have spent the money up front for MRI,” he said, adding that a cost analysis study could be useful in the future.

“In my opinion, MRI can be a really great option for an owner when their horse has had chronic lameness and the typical strategies—like medicating joints, farriery, non-steroidal anti-inflammatory (NSAID) therapy, time off work, rehabilitation—haven’t been beneficial,” said Koch. “That’s especially true in those cases when radiographs and ultrasound are inconclusive.

“At that point it starts to become a conversation of whether it might be more beneficial, in the long run, to spend that chunk of money up front examining both the bony and soft tissue structures in the area of concern in three dimensions and then implementing treatment instead of somewhat guessing at the best treatment plan,” he continued. “An added benefit is peace of mind for an owner as the horse returns to work if MRI doesn’t reveal major pathology.”

The study, “Comparison of lameness outcomes in horses with acute or chronic digital lameness that underwent magnetic resonance image,” was published in the New Zealand Veterinary Journal.