Bisphosphonates for Managing Navicular

Since hitting the commercial equine market four years ago, bisphosphonates have been used primarily to manage horses with navicular disease. But what effect do they really have on navicular region pain and lameness?

Niklas Drumm, DrMedVet, Dipl. ACVS-LA, ECVS, a shareholder and practitioner at Tierklinik Lusche, in Germany, reviewed the existing research on this topic during the 2018 British Equine Veterinary Association Congress, held Sept. 12-15, in Birmingham, U.K.

Bisphosphonates are believed to be the most potent inhibitors of bone resorption, said Drumm; they counter bone loss by killing osteoclasts (cells that absorb bone tissue during growth and healing). Studies in humans and animals also suggest they might also be anti-inflammatory, chondroprotective (protect joints), pain-relieving, and anti-angiogenic (prevent new blood vessel growth).

Two types of bisphosphonates, tiludronate and clodronate, are currently licensed for use in horses in several countries. Researchers have conducted studies on both.

In a 2003 study, Denoix et al. found improved lameness in horses with navicular issues two to six months after tiludronate treatment. A 2009 study on that drug’s effect on horses with back pain due to spinal osteoarthritis showed relief four months post-treatment. And in a 2010 study of horses with bone spavin (osteoarthritis of the lower hock joint), tiludronate resulted in improved lameness 120 days post-treatment.

While fewer studies have been done on clodronate, the drug’s 2010 freedom of information summary showed a 74.7% improvement in navicular lameness two months post-treatment, dropping to 67.4% six months post-treatment, which is comparable to tiludronate, said Drumm. He added that among all bisphosphonate studies, scientists saw the best results two to six months after treatment, with no follow-up longer than six months.

When considering bisphosphonates’ efficacy for managing foot lameness related to the navicular region, said Drumm, it’s important to remember that this disease’s degenerative changes can affect all parts of the podotrochlear apparatus: the navicular bone, deep digital flexor tendon, navicular bursa, and supporting ligaments.

“Many more structures than just the navicular bone can cause palmar heel pain,” he said. “And not all navicular bone pathology involves bone loss or resorption.”

Therefore, only cases of navicular disease with bone lesions should theoretically benefit from bisphosphonate treatment. However, as research into this drug continues, scientists might find that horses with other podotrochlear apparatus issues might also benefit from its anti-inflammatory and analgesic effects, as well.

Ultimately, said Drumm, bisphosphonates might be a fairly short-term adjunctive therapy (e.g., in addition to traditional orthopedic shoeing, intrabursal and intra-articular injections, and non-steroidal anti-inflammatories) for horses with foot lameness stemming from navicular disease.