Research has highlighted a lack of evidence to support the usefulness of taking neck X-rays in pre-purchase examinations (PPEs).

A new paper by Royal Veterinary College (RVC) researchers has reviewed findings from previous studies on cervical X-rays, to answer whether they should be included in PPEs. The researchers said neck X-rays are more frequently being requested in vettings – but concluded that current evidence suggests “most findings present on cervical radiographs acquired at PPEs are of unknown or low significance in a clinically normal horse” – and there is “little evidence to support these as part of a PPE”.

It was also found that there is “minimal evidence of the progression of subclinical abnormalities found in cervical X-rays and their future impact on performance”.

Rupert Freddie Dash, lead author and RVC staff clinician in equine diagnostic imaging, told H&H as radiologists his team is often asked to look at PPE X-rays and that the neck “can often be an area that is quite tricky for us”.

“We find that sometimes, due to no fault of the vet taking the X-rays, they can be of lesser diagnostic quality than, for example, limb X-rays. If they are of reasonable quality, even then the findings can be quite difficult to interpret, so we thought it would be a good idea to review all of the evidence and see whether these are worthwhile X-rays to be taking,” said Dr Dash, adding that although the neck is a well-researched area, there is limited research around PPEs in general and on this issue.

“There’s almost no evidence that will tell us if we find something [on a cervical X-ray] in the PPE, how likely that is going to inhibit or reduce the horse’s performance.”

The paper also addressed the difficulties of cervical X-rays being taken in an ambulatory setting such as at someone’s yard, as portable machines are not as powerful as those used in a hospital. This means the images are “often underexposed”, which can “reduce image quality and hinder thorough evaluation”.

Dr Dash said a portable X-ray machine is more suited to limbs, so “perfectly diagnostic” images can be obtained.

“In my opinion there is still a place for X-rays of the limbs in PPEs,” he said. “There is still relatively limited research about how findings will go on to affect performance, however there is more research than on the neck, and vets may have more depth of experience to draw from with issues relative to the limbs.”

Dr Dash said that when it comes to PPEs “there is more evidence currently that a physical exam of the neck is more valuable in terms of predicting if there’s an issue”.

“Vets should palpate and manipulate the neck, including doing tests that may involve getting some feed and making sure that the horse can reach its flanks. I would say that would be more useful than radiographs,” he said.

Lucy Grieve, the British Equine Veterinary Association’s projects officer, told H&H that X-rays are very common now in PPEs, but buyers “should beware of their limitations”.

“At one end of the spectrum, there is clear evidence that deviations from the normal in neck and back X-rays are of no predictive value for future soundness or athletic potential, where the PPE and history have not raised suspicions,” she said.

“At the other end, some abnormalities seen on limb X-rays will have a significant predictive value – but buyers should remember that there are still many deviations seen in limb X-rays that are not indicators of future problems.”

Ms Grieve added that misjudging the significance of abnormalities seen on X-rays alone “can and does result in many sales falling through unnecessarily” – and advises owners to discuss any findings with their vet.

You might also be interested in:

New research reveals most common findings in pre-purchase horse vettings

Buying horses: why you can’t legally rely on a seller’s vetting

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The world of diagnostic imaging is changing fast.

Most equine vets now use digital radiography rather than traditional photographic X-ray plates, while MRI and ultrasound scans have become routine.

Fewer diagnostic centres currently have access to computerised tomography, or CT. This high-resolution radiography development can produce images of a virtual “slice” of the region that is being examined.

In an X-ray of the foot of a horse, for example, taken from front to back, all the bone structures are superimposed upon one other. The resulting flattened image can be difficult to interpret. A CT scan, on the other hand, allows the vet to look at the same structures slice by slice.

Vets in Belgium and the Netherlands compared the X-ray results and CT scans of 30 horses suspected of having lower limb fractures to see which type of image enabled the most accurate diagnosis. They asked four experienced orthopaedic equine vets to interpret the necessary images, without allowing them

to confer.

The results, published in the EVJ, showed that agreement between the vets’ diagnoses was very good. The level of correlation between the two types of image, however, was not so impressive.

Both imaging methods showed up most of the fractures, but the CT images appeared to reveal more tiny cracks around the main fracture and more fragments.

The horses were standing and weight-bearing for the X-rays, but the CT scans were carried out under anaesthesia. While it’s possible that the fractures were more “opened up” for the CT scans, this method was still judged to provide a better assessment.

The vets make the point, however, that both types of image are just a projected picture.

There is no substitute for surgical evaluation of the bone in the operating theatre.

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What is ultrasound and how does it work?

Roger Smith MRCVS, professor of equine orthopaedics at the Royal Veterinary College, explains: “Ultrasound imaging uses the principles of sonar developed for ships at sea.

“As sound passes through the body, it produces echoes that can identify the distance, size and shape of objects.

“Attached to a box of electronics is a probe [or transducer], which is made of tiny crystals.

“Sound waves leave the transducer and enter the body, where they reflect off the bone and soft tissue to produce an echo that is analysed by a computer in the ultrasound machine and transformed into moving pictures of the organ or tissue that is being examined.

“Bone, which is dense, is identified on screen as a bright line, whereas a tendon appears as a dotted pattern.”

What do vets use ultrasound for?

Examining soft tissue, particularly tendons and ligaments, but also many other structures including joints and even eyes.

Advantages of ultrasound

• Ultrasound images are real-time, so unlike X-rays, where you can only see a static image, with ultrasound movement can be seen

• Doppler ultrasound, which is a relatively new technology, can measure the speed of blood flow in soft tissues, allowing a vet to determine the extent of injury

Disadvantages of ultrasound

• Ultrasound cannot be used to examine the deeper structures in bone as bone matter is too dense

• Problems can arise when ultrasound is used to look at curved tendons and ligaments because if the surface is not parallel to the ultrasound, the sonic beam will be reflected elsewhere

How much does ultrasound cost?

An average ultrasound scan will cost around £160.

This extract is from an article on diagnostic techniques first published in Horse & Hound (15 April, 10)

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For many years, X-rays have been the major imaging technique for evaluation of the foot, for both diagnosis and, more recently, as a screening procedure as part of a pre-purchase examination.

However, new imaging techniques such as scintigraphy (bone scanning), ultrasound and magnetic resonance imaging (MRI) have enhanced our knowledge of problems that can cause foot pain and lameness.

So how useful are X-rays, either for diagnostic purposes in a lame horse or as a predictor of future soundness? What do they tell us?

X-rays enable us to see the bones of the foot, but provide only limited information about the soft tissues. With severe deep digital flexor tendon damage, there may be either mineralisation within the tendon that can be seen on X-rays, or new bone at the tendon’s attachment to the pedal bone. With severe damage to collateral (supporting) ligaments of the coffin joint, a cyst-like area may develop in either the pedal bone or, less commonly, the short pastern bone, which can be seen on X-rays. However, with milder injuries of either of these structures, X-rays may be completely normal.

The anatomy of the foot is complex and the bones that can be seen on X-rays represent only a small proportion of the anatomical structures. Moreover, there must be at least a 40% change in bone structure before abnormalities can be seen on an X-ray. If an area of damage is deep within the bone it may be obscured by normal bone on either side.

Bones are three-dimensional structures, but X-rays give two-dimensional images. It is therefore crucial to obtain images from a variety of different views.

Mud on the foot or the presence of a shoe will result in shadows on an X-ray that confuse interpretation or obscure part of the bones, and can potentially hide abnormalities. Packing the foot with a substance such as Playdoh can reduce confusing shadows.

There is no doubt X-rays can provide crucial information provided they are high quality and that a sufficient number of different views have been obtained. In most circumstances, the shoe should be removed, so that no part of the bones is obscured. This will also facilitate proper cleaning of the foot.

There is also little doubt that advances in technology mean digital or computerised radiography can enhance the diagnostic capabilities of X-rays, provided such sophisticated systems are used in the best possible way. Badly used systems will produce bad X-rays, offering no advantage over conventional techniques. In fact, poor quality digital X-ray images, saved as jpeg files and sent via e-mail, may provide much less information than conventional X-rays.

Top-quality X-rays still have a major role to play in lameness diagnosis, despite their limitations. In a lame horse, ultrasound, scintigraphy or MRI may provide valuable complementary information.

• This veterinary feature was first published in Horse & Hound (11 May 06)
• Read more about diagnostic techniques in the H&H Online horse care archive

While a detailed clinical examination can allow a vet to determine a lot of information about what is wrong with an ill or lame horse, further investigation is often needed to clarify the details of the horse’s condition, including the source of the problem. This will help the vet to determine the best treatment and advise the owner on the horse’s chances of making a full recovery.

Blood tests

Blood tests can pick up signs of infection, blood disorders, hormonal, liver, kidney, bowel, bone and heart problems, as well as conditions such as azoturia. They also aid assessment of severity and prognosis and can be used to monitor long-term conditions or to check response to treatment.

In most blood tests, a vet takes a sample from the jugular vein in the neck, which is then examined at a lab. Routine blood-screening tests comprise haematology, biochemistry and electrolyte components, the first allowing assessment of red and white blood cell numbers and function, and the others comprising tests for levels of enzymes, proteins and salts that give an indication about a range of diseases.

Blood tests can be taken at home or at a referral lab, with results available the same day or within a few days. Blood tests usually cost £30-£150, depending on number of tests, but complex tests, such as for hormonal diseases, can cost more.

Biopsies

Biopsies (tissue analysis) and tests on body fluids can allow identification of abnormal cells, and are indicators of inflammation and infection. Biopsies and fluid samples are often collected endoscopically or via a needle using ultrasound images for guidance. Because of the need for ultrasound, biopsies are usually done at a referral lab with results available the same day or within a few days. Examination of tissue samples costs around £50-100, plus cost of the ultrasound.

Endoscopy

Endoscopy is used with respiratory problems, and to evaluate the sinuses and internal organs, such as the oesophagus (particularly useful in horses prone to choke), stomach (for example, to check for ulcers), or bladder. It involves inserting a fibre-optic tube containing a camera into the horse, which allows the vet to see what is at the tip of the tube through a small eyepiece, or on a TV screen.

For respiratory problems, an endoscope is inserted up the horse’s nose, either while it is at rest, or while it is exercising on a treadmill, so that the inner surfaces of the trachea and nasal passages can be evaluated. Samples of discharge and biopsies can also be taken at the tip of the endoscope, and a laser can be used via the instrument to perform some types of surgery.

For evaluating sinuses, the endoscope is inserted through a small hole in the front of the head. To assess other organs, it can be inserted via the penis or female urethra into the bladder, via the vagina into the womb, and it may be used rectally to assess the colon.

Small endoscopes can also be used in anaesthetised horses to assess the inner surface of the joints (arthroscopy) and, via a hole in the abdominal wall, to examine the surface of abdominal

organs (laparoscopy).

Endoscopy can be undertaken at the owner’s premises, vet’s surgery or referral centre depending on the type of investigation needed. Results are usually available immediately unless samples are taken.

The cost ranges from around £50 for a very basic examination to around £550 for more thorough evaluation on a treadmill. Sedation of the horse requires extra cost, approximately £20-£50 – though some procedures may cost considerably more.

Ultrasound scanning

This can be helpful in the investigation of tendon, ligament and muscle lesions, as well as evaluating the chest lining, abdominal organs and eyes. Rectal use of an ultrasound probe allows imaging of the pelvic structures and is particularly useful for tracking changes in the ovaries, which aids pregnancy diagnosis. Ultrasound images can also be used when a biopsy is being taken, to guide the progress of a needle into an internal structure.

The area is spread with a special gel (first having been shaved), then a handset is moved over the skin. High-frequency sound is directed from the handset through the body to allow an image to be formed on a screen that represents the reflection and absorption of sound by the different types of surface tissue (the sound rapidly weakens so no information comes back from deeper tissues).

It can be undertaken at the owner’s premises or those of the vet or referral centre. Results are usually available immediately, unless the vet wishes to confer with a colleague. The cost ranges from around £30 for some basic reproductive work to £100-£200 for more time-consuming examinations with higher-resolution machines.

Electrocardiography

Electrocardiography (producing an electrocardiogram, or ECG), measures the electrical activity of the heart. It can be used to assess a variety of heart problems.

Electrodes are applied to the horse’s skin with small clips or adhesive patches, and are then connected to an ECG machine, a radio transmitter, or a small machine that records data that can be analysed by computer. The latter two methods are useful if intermittent problems are suspected, or the condition is only seen at exercise, as they allow long periods of heart activity to be recorded.

This can be done at the owner’s premises or those of the vet or referral centre. Results are usually available within a few days, as records have to be analysed. Costs from around £30-£100.

Radiography

Radiographs (X-rays) are particularly useful when examining broken bones and arthritic conditions, but can also be helpful when investigating lung and abdominal diseases, particularly in small horses and foals. However, the power of X-rays is insufficient to achieve good images of these areas in large horses.

Radiography machines work by emitting a focused beam of X-rays that passes through soft tissues, leaving a shadow on photographic film where the X-rays are stopped by harder tissues, including bone, and non-organic material such as metal.

The resulting negative image is blackest where the tissues are softest (more X-rays are allowed through), and whitest where a dense structure casts a shadow on the film. Changing the power of the X-rays results in images that show up the detail of the soft or hard structures to different degrees.

Alternatively, where computer plates, rather than photographic film, are used, images can be enhanced by the computer to allow visualisation of the detail of different structures. Computer analysis can also allow three-dimensional images to be built up from serial radiographs (a procedure known as computed tomography, or CT). The horse may require sedation for these tests.

Many veterinary practices have portable X-ray machines that can be used for examining some conditions at the owner’s premises, particularly if concerns exist about whether or not the horse can be moved. Better images can be achieved using higher-energy static machines located at practices and referral centres. Results are available immediately unless the vet wishes to confer with a colleague.

X-rays costs around £100-£400, depending on number of radiographs taken and the time involved.

Nerve blocks and joint blocks

These are most commonly used to identify a painful area when this is unclear during clinical examination. Once such an area has been identified, techniques such as radiography or ultrasound can be used to find the actual lesion that is causing the pain.

A local anaesthetic is injected around the nerves or into the joints in areas thought to be painful. If a particular nerve block removes the horse’s symptoms of pain (for example, it stops being lame), the source of the pain can be identified.

This can be undertaken at the owner’s premises or those of the vet or referral centre. Results are usually available immediately. It costs approximately £50-£150, depending on the number of blocks used.

Thermography

Changes in surface temperature are measured and formed into an image of the skin’s surface. This can allow identification of areas of increased blood flow, which may indicate inflammation due to injury. However, as it only shows changes in surface blood flow (rather than deep blood flow, as in the case of nuclear scintigraphy), this procedure is thought to be of less value than the other techniques mentioned here, and is less widely used.

The skin does not need to be specially prepared for thermal imaging, and as the technique is completely non-invasive, there is no recovery period. Thermography costs around £100 and can be carried out at the owner’s premises or at a hospital or referral centre. Results are usually available immediately.

Scintigraphy (gamma imaging)

Scintigraphy can be used to look at a number of conditions, but most often used to investigate pain and lameness to identify areas of the body where there is inflammation, or to monitor healing.

The horse is injected with a radioactive material that is taken up in greatest quantities by the cells that are dividing the fastest, or have the highest blood flow (inflamed areas). A gamma camera detects the radioactive particles, identifying the areas in the body where they are accumulating.

This has to be undertaken at a referral centre, where the horse must remain for 24 hours afterwards so that its waste (which contains radioactive particles for a short period) can be disposed of properly. Results available when the horse is collected. Scintigraphy costs around £600, includes sedation.

Magnetic resonance imaging (MRI)

MRI (or nuclear magnetic resonance, NMR) is particularly useful for elucidation of foot problems, which can be otherwise hard to diagnose, and can also be used to produce images of other areas of the limbs and the head.

This procedure involves detecting the differing magnetic properties of tissue, which generally relate to the concentration of liquid within them. MRI gives particularly good images of soft tissue structures, but because the area to be scanned has to be placed within a magnetic field (usually a cylindrical magnet), there are limitations as to which parts of the horse can be examined in this way.

This procedure takes place at a referral hospital. Results are usually available when the horse is collected, unless the vet wishes to confer with a colleague. It costs around £1,500 for high-resolution scans done under general anaesthesia; less for lower-resolution imaging done with the horse standing and sedated.

This guide to veterinary investigation techniques was first published in HORSE magazine (January ’05)

Diagnosing lameness requires identification of the lame limb followed by detection of the location of pain within that limb.

Sometimes, isolation of pain is straightforward. Careful clinical examination of the limb reveals an obviously painful focus, usually associated with some degree of heat or swelling.

However, there are often no clues and nerve blocks are required to desensitise different areas of the limb in turn to see if there is any improvement in the degree of lameness.

Having identified the source of the pain, a variety of imaging techniques, including X-rays, ultrasound scans and, if necessary, more specialised bone scans and magnetic resonance imaging, can be used to identify the cause.

So where do problems arise? Occasionally, an obvious focus of pain is not actually the cause of lameness. There may be painful swelling in the pastern region associated with cracked heels but the source of pain causing lameness may be in the hock.

Nerve blocks are not completely reliable either. They aren’t easy to perform and require considerable practice, while the interpretation of the response is not always straightforward. They also have their limitations on where they can be successfully used on the horse’s body.

Sometimes clinical clues and veterinary technology can provide useful extra information. Areas of bone damage in higher parts of the leg may be identified using a bone scan, and major muscle tears can also be detected.

If a ligament has been damaged, abnormalities may be seen on a bone scan, where the ligament attaches to the bone. Mild damage to a deep muscle can be notoriously difficult to identify.

Obviously, lameness can only be diagnosed successfully if the correct limb is identified and investigated. This is not always as easy as it sounds, especially if there is more than one lame limb. The lameness itself can also be confusing. A head nod is usually evident with forelimb lameness, but can also be apparent with some hindlimb lamenesses.

Lameness that is very sporadic in nature can be extremely difficult to investigate. Episodic bleeding into a joint can cause transient, very severe lameness. Equally a mobile bone fragment may cause lameness that is only evident under certain circumstances.

Lameness that is only apparent when the horse is ridden can also be challenging to the vet. Sometimes, lameness that is low-grade in-hand or on the lunge is much more obvious when the horse is ridden. This can make further investigation through nerve blocks easier. However, lameness that is only apparent when the horse is ridden may be caused by the rider or by ill-fitting tack.

Lameness diagnosis requires a broad-minded but logical approach, experience and time. A detailed clinical examination, repeated if necessary, is essential to identify potential sources of pain.

If an obvious source of pain is not readily apparent, then nerve blocks are needed, but these must be interpreted in the light of the results of the clinical examination. If the pieces of the jigsaw don’t fit together, it may be necessary to start again or seek the advice of a specialist.

This article was extracted from Horse & Hound’s veterinary clinic feature (24 July 2003). To read the article in full contact (tel: 020 8532 3628) to purchase a back issue.

Scintigraphy, or bone scanning, involves injecting a radioactive bone-seeking substance (radiopharmaceutical) into the jugular vein. This flows into the blood and is rapidly absorbed by the soft tissues, such as muscle, and finally the bone. After three hours most of the substance will be in the bone, rather than the surrounding soft tissues.

The radioactivity emitted from the horse can be detected using a special camera sensitive to gamma rays which, when linked with a computer, can be displayed on a screen. Images of each area examined are usually taken over a two-minute period.

In order to get high-quality images with no blurring, movement must be avoided as much as possible, which means sedating the horse and restraining it in stocks. Blinkers and ear plugs also help to keep the horse quiet.

Bandages are applied to the limb at least 12hr before injecting the radiopharmaceutical to try to ensure good blood flow and are kept in place until the scans are obtained.

Radiography is excreted in the urine and, legally, horses have to be hospitalised for at least 24hr after the injection, as the urine is potentially dangerous until the radioactivity has decayed.

With recent technology, images can be acquired dynamically and corrections made for any movement. This enhances image quality and sensitivity, particularly when examining the upper limb joints such as the shoulder and the stifle, and also the back, sacroiliac and pelvic regions.

Recognising hot spots

Scintigraphy allows the assessment of blood flow, soft tissue abnormalities and bone function. An increase in blood supply or bone turnover will result in increased absorption of the radiopharmaceutical, producing a “hot spot”.

A more sensitive indicator of abnormalities of bone function than radiography, scintigraphy gives less precise anatomical information than an X-ray.

Modern computer software enables us to evaluate the images quantitatively, so that, if a hot spot is identified, a statistical comparison can be made with the opposite leg, which, in turn, enhances our ability to determine whether the hot spot is likely to be clinically significant. However, a hot spot is not always associated with pain.

Using advanced technology, X-ray images are scanned into a computer and superimposed over a scintigraphic image, to help to determine the precise anatomical location of the hot spot.

The types of clinical situation in which scintigraphy proves invaluable are varied, such as detecting the source of a forelimb lameness, discovering a stress fracture, revealing a large bone cyst or confirming raised levels of muscle enzymes in the blood.

Scintigraphy is not a substitute for a thorough, comprehensive clinical examination, nerve blocks, X-rays or ultrasonography. It is a complementary technique, best used when focused on a specific area.

Some horses, particularly older ones, have poor uptake of the radiopharmaceutical substance. Called a “cold leg”, it makes interpretation difficult. In others, multiple hot spots may be identified which are red herrings and can be misleading.

The technique, therefore, should only be employed as a diagnostic aid as part of an investigation. But it can provide valuable information to achieve a diagnosis which otherwise might not be reached.

• This article was originally published in Horse & Hound magazine

Q: My horse has been lame for about a month now. The vet thinks there could be a serious problem, such as a hairline fracture or disease in the bone. He suggested we X-ray the bones using a method called “scintigraphy”. Could you please explain what this is?

Harvey Carruthers MRCVS replies: Scintigraphy is a technique which is used to picture the equine skeleton using a special imaging camera.

Though other techniques can be used, such as ultrasound, the scope of scintigraphy is most comparable to traditional radiographic (X-ray) techniques although the equipment required is highly specialised making it considerably more expensive. Both techniques rely on using radioactive materials, which demand high safety standards.

Radiography can be used to identify structural changes, such as major fractures or advanced remodelling of bone. Scintigraphy, on the other hand, is used to detect bone growth, remodelling of bone associated with disease, and the healing of hairline and stress fractures.

The technique allows the vet to more accurately assess changes which occur during bone disease and repair processes, often giving a snap-shot of those changes before they’re apparent with radiographic techniques.

Healthy bone is a surprisingly active material which relies on maintaining a balance between absorption and construction by cells called osteoclasts and osteoblasts. This allows for the turnover of materials while retaining the bone’s strength and density at the same time.

Natural changes to bone characteristics may occur through alterations in physical activity and diet. Phosphate is a vital component of bone and a deficiency leads to an imbalance of the usual absorption/construction equilibrium resulting in weak bones.

To assess thesechanges, scintigraphy involves injecting your horse with a harmless radioactive compound in a process known as “radio labelling”. This is a means of attaching a radioactive molecule (technetium) to a phosphate compound that can be incorporated into the horse’s bone structure.

The injection releases the compound into the horse’s blood stream and variations in the rate of its absorption into the bone (determined by metabolic activity and the rate of bone turnover) can be calculated using a’gamma camera’. This camera is a heavy piece of equipment which is usually mounted on an automatic lifting device.

Used in conjunction with sophisticated computer software, it’s possible to count and analyse the amount of radioactivity emanating from the horse’s bones and/or soft tissue, scanning the horse’s body region by region.

Graphic illustrations are produced to show ‘hot spots’ of activity, representing areas of new bone growth, deposition or damage.

Scintigraphy hasproven highly valuable in cases of lameness where other investigations have been inadequate, especially in the detection of stress-induced injuries to the shins of young racehorses as these types of injuries are difficult to detect with a traditional X-ray machine.