Equine Science Update
Reports from the world of  equine research.
Supraspinous ligament damage.
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Back pain is commonly blamed with 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.

The supraspinous ligament (SSL) runs along the middle of the back attaching to the dorsal spinous processes of the vertebrae.  It may be damaged as the result of direct trauma. But in most cases, injury is thought to be due to overstretching of the ligament fibres, particularly in jumping horses.

Scanning the SSL is now part of the  routine examination for investigating back pain in horses. Signs of damage to the ligament are often apparent.

Changes that might be seen include:
darker (“hypoechoic”) patches - as an indication of  acute active damage to the ligament.
changes in the alignment of the fibres within the ligament.
and brighter areas indicating scarring within the ligament.

But how significant are these changes? Are they necessarily the cause of the horse’s problem?

Scientists at the University of Cambridge looked at whether ultrasonographic changes are related to the use of the horse (ridden or unridden) or the presence of clinical back pain.

Dr Frances Henson and colleagues found no significant difference in the ultrasonographic appearance of the SSL between groups of ridden  and unridden horses, and those with unrelated back pain.

They examined thirty-nine horses as part of the study:
Group 1. (13 horses) had not been ridden and showed no sign of back pain.
Group 2. (13 horses) had been ridden regularly but with no history, or current sign of back pain.
Group 3. (13 horses.) with clinical signs of back pain.

Abnormal ultrasound findings were found in all horses - regardless of whether they had been ridden or not, or shown signs or back pain. Each horse had at least one abnormality in the SSL. Most (61% ) of the abnormalities occurred between the spinous processes; 39% occurred above the dorsal spinous process. Most (68%) of the abnormalities were found in the lower thoracic region (T14 - T17).

So the presence of visible changes in the supraspinous ligament does not necessarily mean they are the cause of back pain.

The scientists conclude that abnormalities may occur in the SSL without any other evidence of clinical disease. To clarify the diagnosis and prove that these lesions cause pain they recommend that local anaesthetic techniques should be used.

“The clinical importance of potentially abnormal ultrasound findings can only be evaluated when combined with clinical history, physical examination, local analgesic techniques and absence of other diagnostic evidence that might explain the origin of the pain.”

For more details see:

Ultrasonographic evaluation of the supraspinous ligament in a series of ridden and unridden horses and horses with unrelated back pathology.
FM Henson, L Lamas, S Knezevic, LB Jeffcott.
BMC Vet Res(2007) 3, 1

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© Copyright Equine Science Update  2007