Back Pain in Horses – Expaxial Musculature

27th October 2008

Background

Back pain and diseases of the spine and pelvis are significant problems in all types of performance horses, potentially causing poor performance, lost training days and wastage. As a result, back pain represents a considerable economic and welfare issue for the equine performance industries.

Evaluation of back problems in performance horses is an important part of physiotherapy and veterinary practice. Yet back pain syndromes are insidious and difficult to diagnose due to the variability of presenting signs ranging from overt lameness or pain on palpation of the back to subtle gait alterations or even behavioural changes. Complicating matters further, multiple problems often coexist, particularly lameness and back pain.

Research to date has been led by the veterinary profession with a focus on pathoanatomical problems underlying back pain. However, advances in human back pain have been led by physiotherapy research. Physiotherapy research has focussed on the neuromotor control model1 and the associated dysfunction, especially of the epaxial or deep back muscles that occurs as a result of back pain from different forms of pathology.

Aim

The overall aim was to increase the knowledge of back pain in horses by using this novel approach. Specifically; how pathology of the back itself or other parts of the musculoskeletal system is reflected in the epaxial muscles and to determine the relationship between atrophy or dysfunction of these muscles and pain and/or poor athletic performance.

Objectives

In order to do this we divided the research into three phases with the following objectives:

Phase I: To describe the anatomy, biomechanics and function of the equine epaxial muscles.

Phase II: To reliably measure the equine epaxial muscles using ultrasonography.

Phase III: To objectively measure the response of equine epaxial muscles to back pain syndromes using ultrasonography.

Key findings

The results of this project have shown that the anatomy and function of the equine epaxial muscles are comparable to that of humans. A difference, however, is the equine spinal anatomy and its variations, especially in the lumbosacral region, with the variations occurring in about a third of Thoroughbred horses, and but none of the Standardbreds. These variations could have a major effect on stability of the lumbosacral joint and affect performance through altered mobility and or a predisposition to pathology during an athletic career. Ultrasonography was found to be a repeatable and reliable tool for measurement of the equine epaxial muscles and when examined in clinical cases of equine back pathology, there was a clear reduction of the epaxial muscle size at the level of and close to areas of significant injury or pathology. While ultrasonography was focused on epaxial muscle size, it was found that bony pathology was also detectable using this non-invasive tool. Another finding of particular interest was the high prevalence of serious back pathology in horses at the end of their athletic careers, justifying the importance of new, and more sensitive methods to detect such pathology.

For more information on the neuromotor control model in human or equine back pain please see link to paper McGowan CM, Stubbs NC, Jull GA. Equine physiotherapy: a comparative view of the science underlying the profession. Equine Vet J. 2007 Jan; 39(1):90-4.

Conclusions and recommendations

In conclusion, use of a novel approach to equine back pain, using the human neuromotor control model, has advanced knowledge of the equine back, its function and the epaxial muscle response to back pathology. Ultrasonography of the epaxial muscles is a valuable non-invasive tool that will help detect back pain and associated pathology in horses. This information will be valuable to veterinarians and physiotherapists managing back pain and poor performance syndromes in athletic horses and will lead onto future work on the effect of physiotherapeutic intervention on the recovery of epaxial muscle function following back pain.

The full report can be found at www.rirdc.gov.au/fullreports/index.html or www.rirdc.gov.au/eshop