Fractures in the back of racehorses are more common than previously thought, according to a new study. Dr. Liz Collar said at the AAEP convention that lumbar vertebral fractures can be catastrophic for racehorses and the jockey.  The lumbar area is about 3-4 hand widths behind the rear of the saddle and these fractures occurred more commonly in quarter horses than thoroughbreds.  At the University of Tennessee, a study looked at anatomical findings in the lumbosacral spine of 16 quarter horses that were euthanized for reasons other than lumbosacral disease. The horses were newborn to 22 years of age, including only one racehorse. 

Interesting findings were that out of the 16 horses, all had six lumbar vertebrae except one only had five vertebrae.  Almost 70 % of the horses had disease in the facet joints where the vertebral processes attach to the spinal processes and 62% had disease of the intervertebral discs.  So over 60% of the horses has disease in their spinal area and since the study included very young horses, it is likely that most mature quarter horses have some degree of spinal disease that increases as they age.  Nine of these horses had lesions in the bones indicating regions of stress and could lead to a stress fracture.  Also, 92% of the horses had some cartilage retention in the growth plate that should have become bone, which indicates stress in the growth plates not found in other areas of the horse’s body.  Conclusions of her study were that lumbosacral growth plates are inactive in quarter horses by 2 years of age and disease in the horse’s lower back seems to be much more common than was previously thought.