PRE-SALES radiography has become a standard screening tool for orthopaedic disease; the number of images (‘x-rays’) taken of a horse’s four limbs can be as many as 36. Ultrasound is sometimes added to the mix to give an additional perspective – being better for soft tissue structures (tendons and ligaments), but also sometimes invaluable for hard surfaces (bone and cartilage) too.

Osteochondrosis and OCD, Navicular disease and Wobblers, chips and cysts feature on the list of conditions causing concern. All this imaging is aimed at understanding the ‘fitness for purpose’ of equine athletes. Such animals suffer from a range of conditions, sometimes specific to the breed or indeed breed-line that may affect athletic performance or future stud value.

Screening may be requested by purchasers who then decide whether to buy, or indeed by vendors wanting to present horses for sale in a manner that raises fewer questions. These latter may act on the findings to request that an issue be ‘tidied up’ so that future sets of x-rays appear ‘clean’.

Scrutinise

These days, digitised images can be beamed far and wide for multiple opinions, some informed and some not so. The pressure on vets is often immense to scrutinise series of radiographs in double-quick-time for sometimes subtle changes whose effect on future performance may be unclear. The assessment becomes easier if the horse is older and has a history of significant previous athletic performance but often these are juvenile, untried equids.

If you are a potential purchaser, always gather available, reliable information on past performance and provide it to your advising vet; keep the horse’s future intended purpose front and centre in those discussions; and make pragmatic decisions thereafter based on a best, but accept it may be imperfect, understanding of the position.

It is important that people realise that the interpretation of radiographs (and other images as well as clinical findings more generally) is not an exact science.

Radiologists have long cautioned regarding ‘normal variants’ – findings in a percentage of the population that are generally held (but not guaranteed) to be of no clinical significance. These can include radiographic changes that appear as ‘chips’ and ‘cysts’ associated with a joint, most notably knee (carpus), hock (tarsus) and fetlock (mcp/mtp).

A ‘chip’ may indeed result from an event and be clinically significant, e.g. galloping causes pressure and oft-times trauma to front of knee; landing steep from jumping high stretches the suspensory ligament sometimes pulling bony fragments from rear of fetlock.

BUT:

  • smooth, rounded ‘fragments’ may appear in these locations in youngsters never yet asked to race or jump;
  • separate centres of ossification may be ‘normal variants’ present from birth;
  • usually curved ridges and furrows near joints may appear straighter than normal; and
  • patterns of bone density (sclerosis and lucency) underneath cartilage in the areas where cysts appear can certainly mimic said cysts.

    • All of these might carry little or no current or future clinical significance. Clear as mud!

    Surgery

    An additional issue arises with radiography (but not ultrasound) as it involves the use of radiation: care for the health and welfare of both horses and humans, expose neither to unnecessary hazard. I expect that in future vets will, even more than now, have to justify the use of radiation to screen for disease in young horses not showing clinical disease – after all, these are equines expected to be ‘normal’. And we will increasingly have to explain decisions to anaesthetise and perform surgery on horses if there is any sense of an intent to ‘clean something up’ and not a need to treat a condition of clinical significance to the animal.

    Screening enables us to detect, understand and predict equine disease better; and then treat horses to help them to heal – which is what veterinary medicine is all about when all is said and done.