Reducing Back Sensitivity

Back pain is often suspected in horses, but most treatments haven't been researched much or at all. Results of a study designed to measure the effects of massage, chiropractic, and phenylbutazone (Bute) on back sensitivity were presented at the 2007 American Association of Equine Practitioners Convention, held Dec. 1-5 in Orlando, Fla. Kevin Haussler, DVM, DC, PhD, assistant professor within the Department of Clinical Sciences at Colorado State University, reported on the study.

Researchers used pressure algometry (a spring-loaded device with a rubber-tipped plunger that measures applied pressure on a gauge readout) to measure mechanical nociceptive threshold (MNT)--the pressure at which a horse reacts painfully--at several locations along the spine. This method of objective pain assessment is also used in humans to evaluate pain due to fibromyalgia, osteoarthritis, and other conditions. A higher MNT means more pressure is required to elicit a response, so the horse is less sensitive or painful.

Researchers theorized that subclinical back pain is present in all ridden horses, so therapy should lessen that pain and raise MNTs. Thirty-eight healthy adult horses with no history of back pain from four farms were used for this study, which aimed to see which treatment modality raised MNTs the most over the course of a week. The horses were treated as follows:

Pressure algometry can help researchers measure pain.

Pressure algometry can help researchers measure pain.

  • Seven horses received Bute (1 g/500 pounds orally every 12 hours) for a week.
  • Eight received one chiropractic treatment using a spring-loaded mechanical force instrument at localized regions of joint stiffness, abnormally high muscle tension, or pain (this mechanism ensured a consistent force/velocity of the treatment).
  • Eight received one directed massage by a certified massage therapist.
  • Seven received no treatment, but continued to be ridden (active controls).
  • Eight received no treatment, but were turned out and rested (inactive controls).
  • All horses' MNTs were evaluated on Day 0 (before treatment) and at Days 1, 3, and 7 post-treatment.

The results of MNT evaluation on different sites on each horse were pooled for evaluation, and the numbers were somewhat surprising, said Haussler.

  • The Bute group actually had a negative response, with 9% and 8% lower MNTs on Days 1 and 3 compared to Day 0. On Day 7, this group had an 8% higher MNT. Bute is much more effective if given when active inflammation is present, noted Haussler.
  • Massage was beneficial throughout the study period, with an 8% higher MNT on Day 1, 9% higher on Day 3, and 12% on Day 7.
  • Chiropractic resulted in a slight (1%) decrease in MNT on Day 1, an 11% increase on Day 3, and a 27% increase on Day 7 on average.
  • Both active and inactive controls' MNTs fluctuated by about 1% across all days.

"We hypothesized that low-grade back pain or inflammation was present in ridden horses, and we found this to be true; otherwise the MNTs would not have increased in all three treatment groups relative to the two control groups," said Haussler. "Massage was beneficial throughout the study; Bute had negative effects for 3 days, then it had a positive effect; and chiropractic had a negative effect on the first day, but then it had the most positive effects.

"Pressure algometry provides an objective tool to evaluate commonly used, but unproven, treatment modalities for the treatment of back pain," he concluded. "Future studies need to evaluate combined treatment effects and long-term MNT changes in horses with documented back pain."

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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