What are kissing spines?

A horse with this condition feels consistent, low-grade pain because the spinous processes, or sections of bone attached to the vertebrae, are too close together and impinge on each other, as shown in the x-ray below.

Kissing spines shown on x-ray

Diagnosing kissing spines

“Kissing spines often has very subtle symptoms,” says Dr Svend Kold, a specialist in equine orthopaedic surgery. “We watch the horse being schooled and look at everything, including the horse’s demeanour, limbs, posture, whether he is accepting the bit, whether he unlocked in his back, and the expression on his face.

“The trot is often okay, but the horse invariably struggles to maintain a three-beat canter and frequently gets disunited. He may also get irritable when the girth is done up or when you groom his back.”

As well as X-rays and ultra-sonograms, another method of diagnosis is to inject a local anaesthetic between the spinal processes — basically a nerve block — and ask the rider to school the horse and see if it feels different.

What type of horses are affected?

It is predominantly dressage, event and other competition horses who are referred for treatment. This could be because it is more noticeable in performance horses due to the physical demands on them, while in horses just used for hacking and low-level work, the problem may go unnoticed.

Alternatively, it may be that performance horses are more prone to the condition, due to the physical demands placed on them.

Veterinary literature has suggested that up to 34% of horses (which tend to be over-represented by Thoroughbreds) may show signs of kissing spines on X-rays, but many do not exhibit any clinical signs as a result of them.

Treatment for kissing spines

Surgery is often used to rectify the problem, but the original operation developed in the 1980s has been modified in recent years to offer a far less invasive option.

“Instead of removing sections of the spinal processes, the ligaments between the spinal processes are cut — an Interspinous Ligament Desmotomy (ISLD),” explains Ricky Farr, MRCVS.  “This can be done under standing sedation.

“Some of the ligaments between the spinous processes in the back are cut through a very small incision (usually less than 1-2 cm). This technique has been gaining increasing popularity amongst surgeons due to being minimally-invasive and horses are often back into work within six to eight weeks.”

This can be compared to the original operation, which was developed in the 1980s, and saw significant chunks of bone removed under general anaesthetic with much longer recovery times.

Dr Kold explains: “After the incision, we would cut through the supraspinous ligament. Once all muscular and ligamentous attachments are severed down either side, we cut off around half the spinal processes, removing about three inches of bone. Next, the ligaments and skin are sutured. After the procedure, a void is left, as the bone doesn’t re-grow and a blood clot forms, followed by fibrous tissue.”

But Dr Kold says that deciding whether or not to operate is not always clear-cut. Much depends on the degree of impingement, the individual horse’s tolerance levels and his lifestyle.

“If he’s an athlete and needs to go places, it needs correcting,” he explains. “The important question is what are people going to do with the horse. Alternatively, can we maintain performance with a twice-a-year steroid injection in combination with physiotherapy and training?”

Important role of physiotherapy

Equine surgeon Bruce Bladon points out that a colleague in Sweden who has operated on a lot of kissing spines cases has more recently had excellent results — without surgery — with horses sent to a rider experienced in equine rehabilitation and re-schooling.

“This makes sense,” says Bruce. “We’re talking about the normal flexibility of the spine, occasionally resulting in the edges of the bones ‘kissing’. It’s easy to imagine how a different rider or saddle, or increased muscle tone as a result of physiotherapy and a change in work, might prevent this.

“It’s also easy to see how the results of schooling a horse could be so different, depending on the psychology of the rider,” adds Bruce, who believes that kissing spines surgery can, in some cases, have the effect of a placebo.

“The difference in attitude between a rider concerned that their horse is behaving like it is because it has an underlying disease, and a rider who knows that their horse has had surgery for this disease and is now ‘cured’, will be considerable — and quite rightly so.”