KISSING SPINES Just how much of a problem are they?
horses being diagnosed (and condemned) for suffering with ‘kissing spines’. But just what are they? And how much more have we learnt about them in the intervening years?
T
Anatomy Just like us, a horse’s spine is made up of cervical, thoracic, lumbar, sacral and coccygeal vertebrae. The thoracic vertebrae(T1-T18) make up the withers and the part of the back the saddle sits on. As you can see, these vertebrae have very long spines (or ‘dorsal spinous processes’ – DSPs).
Figure 4. Radiographically evident over riding DSPs. . Arrows mark the worst radiographically affected areasThis horse had coped for several years, but aſter developing a hindlimb lameness, he also started to show signs of back pain.
In the more advanced over riding image (Fig 4), you can see how there is marked irregularity in the shape of the DSPs caused by the trauma neighbouring DSPs create by interfering with one another.
The most common region for kissing spines to occur is directly beneath the saddle (T13-T18). As the radiographic changes can be pretty dramatic, it is easy to see how a diagnosis of ‘kissing spines’, with all its negative connotations, can be quickly reached.
HOWEVER Many apparently completely normal horses can have dramatic ‘kissing spines’ on radiographs – which do not in any way affect them! The incidence of radiographically abnormal DSPs in clinically normal horses can be above 80%.
So how do we know which cases are significant? This is done by asking the following three questions:
Figure 1. A horse’ s skeleton Near the withers, these DSPs point back, but further back these point for-
ward. ‘Kissing spines’ describes a condition where the long dorsal spines of the thoracic vertebrae rub or overlap with each other. These conditions are more specifically described as ‘impinging’ dorsal spinous processes (DSPs) or ‘over riding’ DSPs. Example radiographs of each are shown below.
1) Does the horse show classic signs of back pain? • Pain/resentment/guarding/aggression on back palpation • Weak/poorly developed back muscles in the saddle area • Reluctance to liſt up his girth and flex his back • ‘Cold backed’ behaviour on mounting • Tight/tense/mis behaviour under saddle • High head carriage • Refusing jumping • Deterioration in behaviour
2) Do radiographs show kissing spines?
3) Does diagnostic analgesia (‘blocking’) confirm that this kissing spines are causing the undesired/pain behaviour? Diagnostic Analgesia
Figure 2. A horse with no evidence of ‘kissing spines’
Local anaesthetic is infiltrated around the areas of concern shown on radiographs and the horse is lunged or ridden again. If there is a significant improvement then it confirms that the impinging or over riding DSPs ARE likely to be a significant source of discomfort. Diagnostic analgesia is THE crucial step in the diagnosis of pain relating to kissing spines! Horses that show only very intermittent symptoms can be tricky – in these horses I will still try blocking them as oſten they will appreciably move more freely aſter blocking, however if there is no obvious response to blocking I will sometimes go on to treat these horses and have had good resolution of the intermittent behaviour.
In some cases horses will undergo nuclear scintigraphy (‘bone scan’) as part of the diagnostic process. This involves intravenous injection of a radioactive isotope which is selectively taken up by bone being modelled. In horses with active kissing spines which are interfering with each other, these areas will usually show up ‘hot’ on scintigraphy. However once again this still needs to be confirmed with diagnostic analgesia as just because an area of bone is ‘active’ it is not necessarily ‘painful’.
Figure 3. Radiographically evident impinging DSPs. These were not clinically significant in this horse.
’ 24 THE WINTER SPECIAL 2019 For the latest news
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wenty years ago, the first digital x-ray machines became available. This meant there was suddenly a quick and easy way to radiograph a horse’s back. This in turn led to an enormous rise in the number of
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