Back pain is commonly blamed for loss of performance in horses. The complex structure of the back makes it a challenge to identify the exact nature of the problem. As well as damage to the vertebrae themselves, the muscles and ligaments may be involved. Some back pain is secondary to problems elsewhere - often the hind legs.
Identifying the site of pain can be difficult. But advances have been made in recent years. Techniques such as nuclear scintigraphy (“bone scan”), radiography, ultrasonography may pinpoint the problem.
Arthritis of the joints between the vertebrae is one possibility. As well as being joined together by the “intervertebral disc”, the vertebral bodies each have two pairs of articular processes at the front and back. These form synovial joints (“articular process - synovial intervertebral joint”: AP-SIVJ) with the corresponding processes of the neighbouring vertebra. They provide stability yet allow some movement between adjacent vertebrae.
Degenerative joint disease (arthritis) of these joints is common in older horses - and is often found in horses with back pain. However, it is not present in all horses with back pain, nor do affected horses always show back pain.
Injecting anti-inflammatory medication, such as corticosteroids, into the area may ease the discomfort.
A possible new treatment for back pain associated with bone lesions has been suggested by work at the Centre d’Imagerie et de Recherche sur les Affections Locomotrices Equines, at the French National Veterinary School of Alfort. Dr Virginie Coudry and her colleagues found that tiludronate, a drug that inhibits bone reabsorption, offers an effective treatment for these cases.
Tiludronate is licensed in some countries for the treatment of bone spavin and navicular disease. It blocks the activity of the osteoclasts, the cells that reabsorb bone as part of the bone remodelling process. Osteoclast activity is thought to be painful - so blocking them should reduce the pain.
Twenty-nine horses completed the study. All had arthritic changes at the AP-SIVJ - mostly in the lumbar region. Many also had abnormalities of the spinous processes.
Fifteen horses were treated with tiludronate (1mg/kg) given as a single intravenous infusion. The rest received a placebo, which looked identical but was inactive. The investigators did not know which horses had received tiludronate or the placebo until after the final assessment.
Rather than assess back pain during a static examination by manipulating the back, the researchers chose to assess it under more natural conditions, as the horses were moving. They observed the horses walking, trotting and cantering. Each horse was then given a score according to flexibility of the back.
Horses treated with tiludronate were significantly better 60 days after treatment than before. They also moved significantly better than did horses treated with the placebo.
Dr Coudry suggests that tiludronate offers an effective treatment for horses with back pain associated with bone damage.
For more details see:
Efficacy of tiludronate in the treatment of horses with signs of pain associated with osteoarthritic lesions of the thoracolumbar vertebral column. V Coudry, D Thibaud, B Riccio, F Audigié, David Didierlaurent, Jean-Marie Denoix. Am J Vet Res (2007) 68, 329 - 337