Posted: 12th March 2014 | Back to news feed
HALLMARQ MRI held a hugely successful user meeting about standing equine MRI in Chamonix.
For horse owners, according to a recent survey in America (AAEP Touch 2013), it is particularly important that their vet keeps up to date with the latest discoveries in diagnosis and treatment. Vets themselves are required to do a number of hours of continuing education each year to maintain their licence to practice.
At the beginning of each year Hallmarq provides an opportunity for its customers to achieve some of these hours, with an advanced user meeting.
Sixty-eight vets and six Hallmarq staff assembled in Chamonix, France for the fourteenth Hallmarq clinical user meeting.
MRI first became available for the standing horse, without the need for general anaesthesia, about a decade ago.
It soon became established as a valuable tool to investigate lameness originating in the foot - for centuries both the most common cause of lameness and a frustratingly difficult region to examine.
Later developments in computer hardware and software improved the ability of the Hallmarq scanner to compensate for the swaying motions of a standing horse, and it became practical to obtain diagnostic images further up the leg.
The knee of the horse is not analogous with the knee of a person (that's the stifle). Instead the joint is similar to that of the human wrist. With the shadows of different bones in close proximity being projected onto a standard x-ray is it often difficult to diagnose bone injury in the equine knee, and even more challenging, x-rays cannot be used to visualise soft tissue at all.
At Hallmarq's meeting in 2013 Dr Thibault Vila, based at a veterinary clinic in Chantilly, near Paris, showed how valuable MRI can be to detect bone changes in the knee. This year Dr Meredith Smith of Image Equine showed just how much is now possible with a presentation on the soft tissues (the ligaments and tendons).
With example cases she concluded that, though further advances would help when injury is suspected in the small transverse and intercarpal ligaments, standing MRI can be reliably used to image pathology in the carpal sheath and nearby longitudinal tendons and ligaments, and the proximal part of the suspensory ligament.
No machine ever invented has been able to truly detect a source of pain, and while standing MRI has been a huge advance in diagnosis there are still occasions (about 10% of exams) when the MR image does not fit with the clinical pattern of lameness. This may be because nothing abnormal is seen, or because the extent or location of the changes seen on the image do not correspond with the horse's behaviour.
Dr Natasha Werpy (University of Florida, Gainesville FL, USA) and Dr Ryland Edwards (Fairfield Equine, CT, USA) explored the possibilities when the image does not fit the clinical expectations, concluding that reasons might be:
- the source of pain is outside the region imaged
- the image reader missed the abnormality
- the lesion is too small to be detected
- imaging is performed before or after any changes are visible on MRI
- imaging shows multiple findings, some of which are unrelated to the current lameness
Using specific cases as examples the speakers discussed ways to avoid these problems, and approaches to establishing a diagnosis when imaging alone is not conclusive.
In recent years MRI has shown that the pain relief provided by standard nerve blocks does not strictly follow the standard textbook patterns. For example it is common for a block traditionally considered diagnostic of pain originating in the foot (the palmar digital nerve block) to propagate up the leg and suppress pain originating in the fetlock.
Dr Michael Schramme (Vet-Agro Sup, Lyon, France) led a discussion on blocking patterns and the need to consider different blocks, different images, or both. It was universally concluded that the commonly used palmar digital or abaxial sesamoid nerve blocks alone cannot be considered adequate evidence to restrict imaging to the foot.
An image reading workshop led by four established interpreters of standing MRI rounded off the meeting. With increasing numbers of cases being seen by MRI, and discussed at a high level in meetings such as this, comes a better understanding of the relationship between images and pathology, and an increasing ability to use MRI as part of the overall diagnostic process.
For further information or to find your nearest MRI scanner contact Hallmarq Veterinary Imaging on (01483) 877812 or visit www.hallmarq.net
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