Equine Science Update
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Encouraging Shock Wave Trial.
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Preliminary reports suggest that a new treatment may improve the chances of recovery from hind limb proximal suspensory desmitis.

Proximal suspensory desmitis (PSD, or high suspensory disease) is being increasingly identified as a cause of lameness in the horse. Strain of the origin of the suspensory ligament at the top of the cannon bone may occur in either the fore limb or the hind limb. The prospect of a full return to work is poorer if the hind limb is affected, or if bony changes are visible on radiography. A previous study 1 in which horses were treated conservatively, ( ie they were given box rest followed by a graduated exercise regime) found that only 17% of cases of PSD of the hind limb returned to full work.

A study at the Royal Veterinary College, London, carried out in collaboration with the Animal Health Trust, has shown an encouraging response to using shock wave therapy (SWT) to treat PSD of the hind limb.

Shock wave therapy is a method of applying high intensity ultrasonic shock waves to tissues. It was first used in the 1980`s in human medicine as a non-invasive technique that avoided the use of conventional surgery in the treatment of kidney stones. Subsequently, it has been used to treat non-healing fractures and damaged ligaments. It has also been found to be useful in relieving pain in soft tissues adjacent to bony structures.

Oliver Crowe, spokesman for the London group, recently reported their interim results and described their experience with the technique.

Horses were included in the study if the site of the lameness was localised to the upper suspensory ligament of the hind leg by diagnostic local analgesic techniques, and the diagnosis was confirmed by ultrasound and radiographic examination.

Horses were treated on an out-patient basis. They were sedated and treated standing. The equipment used was a Swiss Dolorcast Vet (EMS Optident) unit. The shock waves are administered by means of a small probe which is moved over the area to be treated. Good contact is required with the skin, so the leg is clipped and cleaned, and coupling gel is applied. Each treatment consists of 2000 pulses at 10Hz. and takes about 5 minutes to complete. Each horse receives a total of three treatments at two week intervals.

The first few horses treated were confined to box rest for 8 weeks. Later on it appeared that this was not necessary and that in fact a degree of controlled exercise was beneficial. Subsequent horses were hand-walked for 6 weeks after which they were given a gradually increasing regime of ridden work.

Eleven horses have now been treated with SWT for hind limb proximal suspensory desmitis. Six of them (55%) are sound and have returned to full work. Two improved while being treated but deteriorated once treatment stopped. Three horses showed no change.

"Our findings suggest that shock wave therapy may give better results than conservative therapy for proximal suspensory desmitis. " said Mr Crowe. "Further studies are needed to discover the mode of action and to assess whether the response to treatment persists."

1 ref Dyson: Proceedings of the Bain Fallon Memorial Lectures 15; 55-62, (1993.)

Source: presentation at British Equine Veterinary Association Congress, September 2001.