The Kissing Spines Debate
It would appear that the incidence of 'kissing spines' cases is increasing at a worrying rate. For those not familiar with the term, kissing spines occurs when two or more dorsal spinal processes on a horse's back meet painfully as the horse moves. In simpler terms, the spines crunch off one another and cause acute pain. This most commonly occurs when under the weight of a rider and frequently leads to bouts of severe protest, or absolute refusal to be ridden.
The condition is generally diagnosed on the basis of radiographs or scans and different operatives report varying degrees of success through surgery aimed at relieving the contact. The vertebrae involved are usually those in the thoracic spine, from the withers to the end of the rib cage, though I recently saw a horse that had been operated on in the sacral area, which defies reason as the sacrum is a fused organ and its spines, however important, are denied the luxury of a kiss.
History
The horse's boney spine is a complex piece of anatomy whose main objective is to protect the more delicate nervous tissues it contains from trauma. It has to do this while accomodating normal everyday movement, including all the physical exertions of an athletic animal.
It is frequently said that the horse was not intended by nature to jump and its back was never designed for the kind of challenge placed on it by today's equestrian sports. This is plausible, but, whether it's true or not, 'stuff happens' and equine backs are subjected to a variety of challenges they quite commonly manage to deal with.
There has even been wide debate within the profession about the extent to which the spine is capable of independent movement and the possibility of whether or not this can actually lead to pain. Suffice it to say that the balance of evidence strongly supports the view that back pain is a major factor in inhibiting movement and causing reluctance to be ridden. The fact that the sources of this pain are increasingly identified, and reversed, adds to the view, whatever the academic arguments.
Anatomy
The boney spine starts at the back of the skull and consists of cervical (7), thoracic (18), lumbar (6), sacral (5)and coccygeal, or tail bones, (15-21). These are bound together by a complex of ligaments and afford attachment to a wide range of muscles whose purpose is to provide body movement as well as support and integrity to the spine itself.
Fundamentally, the spine is the central boney structure of the body that defines the whole range of vertebrate species. It forms the framework onto which limbs are attached, movement is allowed, and through which a complex sensory system can operate.
Its complexity leaves a whole range of anatomical structures that can be injured, through which pain can be felt and movement restricted. Firstly, the vertebrae themselves: while the amount of movement is limited, less in the horse than cat, obviously, less than in man too, anyone who has experienced back pain knows what it's like and how good it is to have it physically relieved by a practitioner. The same applies to the horse. While it may be difficult to objectively assess the pain source, and impossible to pinpoint using modern technology in most cases, those at the cutting edge know when their horse is restricted and when it's not.
The explanation given for the pain varies with the situation, but it can be accepted that pressure on nerves and (possibly) wedging of vertebrae is a primary problem. Inevitably, the ligamentous structures can also be injured and so contribute, but, in my experience, this would appear a less common aspect of spinal-origin pain.
Muscular injuries, on the other hand, are a constant source of back problems, not just by injury to muscles directly attached to specific vertebrae, but by creating prolonged uneven pressure on the spine, particularly at lumbar and pelvic level. As I have said elsewhere here, a significant number of muscular injuries start in the near hind, on the surface of the pelvis where the large motor muscles are attached and where they apply considerable force to engage in sudden explosive movements.
Such movements may occur in jumping, or correcting, when an error or imbalance has occurred - like a slip on an icy surface. They may also occur in flight, as from a predator, or similar take-off in a domesticated situation.
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Cause
The most common form of quarter muscle injury would suggest the problem doesn't arise as an immediate detectable tear, rather as a progression of recurring aggravations once the original injury has occurred. There may be no detectable lameness; instead, a gradual change in stride length and pattern. Evident lameness comes with growing pain, though it will be subtle in development. The damaged tissues then tend to become indurated, having lost their ability to contract. This alters the balance of forces applied to the spine and, over a period of time (while not producing detectable nodding lameness) causes increasing back pain as well as compensatory complications in other limbs.
Diagnosis
The diagnosis must include two elements. First, inevitably, there has to be acute pain when a horse is ridden and the source has to be attributable to the boney spine. This may include detectable pain on palpation. Secondly, radiographs should show evidence of a significant clinical process, even in recent cases. Thirdly, there should be no other obvious source of pain affecting the back.
Many horses presented with back problems show signs of unspecified fore or hindlimb lameness that may (or may not) be significant in the circumstances. An actively kissing spine does not influence spinal reflexes, so should therefore not affect movement in any limb, especially when the horse is in hand or loose.
Any such an abnormality needs to be stringently assessed as there is no point in subjecting an animal to surgery if the source of its problems are elsewhere.
The understanding of obscure lameness, generally, is a great weakness in modern equine practice and something the profession has to come to terms with. Academic medicine appears to have little or no understanding of this and technological, evidence based medicine has not found a satisfactory method of diagnosing obscure lameness or of teaching graduates, or specialists, how to see it.
The problem with Horatio Nelson at the recent Derby may, or may not, have been a consequence of this, but it would be a sad reflection on the modern profession if lay people were better able to observe and comment on structure and movement than trained graduates, which often is the case.
Treatment
Any true kissing spines problem is possibly only going to be resolved by surgery. But that would be in an animal whose pain is severe, whose reaction is violent and dangerous, and where there is no doubt that the horse cannot be ridden with safety.
In less painful situations, there is a wider variety of options, though it is critical that the source of pain be pinpointed and the influence of outside causes eliminated. Many horses with 'cold backs' or who have suffered trauma, maybe by rolling on a hard object (like a stone), will show radiographic changes that have to be assessed. It is important to be objective and conservative in such cases, as there is little point in operating unless it can be fully expected the problem will be relieved.
There are many horses going the rounds who have been diagnosed as having kissing spines and have had no surgery. Many are being ridden without objection.
Peter Gray
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