The diagnosis and management of back pain is something of a dark art. Even though we can now image the equine spine in great detail, there is still much discussion or even controversy about equine back pain and the various manipulation or therapy techniques employed to alleviate it.

However, we now know far more about the equine back and how it works than we did 20 years ago. Technology and the miniaturisation of highly sensitive measuring devices have enabled us to examine and analyse many aspects of equine movement.

In a recent French research project, vets used an array of gadgets to see whether the size of the panels of the saddle affects the way in which a horse uses his back.

They started with tiny inertial measurement units (IMUs), which use accelerometer and gyroscopic technology to measure movement, fixing five of these to the midline of the horse’s back — including beneath the saddle. They then fitted the stirrups with tiny strain gauges and used a thin pressure pad beneath the saddle, before fitting the rider with tiny bright sensor dots that were filmed with high-speed cameras as the horse moved. This showed the action and influence of the rider on the horse.

Three highly trained horses from the École Nationale d’Equitation (IFCE) at Saumur were ridden by the same rider, first with a standard CWD 2Gs jumping saddle and then with the same saddle but with panels extended around the middle and rear by 5cm.

The high-tech gear was used to analyse how the horses — and especially their spines — moved in rising trot. When the rider rose there was no difference in overall pressure on the back between the two saddles, which is predictable because the rider had not changed weight. But the distribution of weight was altered by extending the saddle panels, with more pressure forward on the front part of the saddle and less on the rear.

In the sitting phase of the trot, pressure was more evenly distributed over the contact area between saddle and horse by increasing the size of the panels.

When the IMU data were analysed and compared with the pressure data, it was clear that the spinal movement range at rising trot was greater with the larger saddle panels. They were, in fact, much more like the results obtained when horses are exercised without any saddle at all.

These results seem to show that standard saddles restrict the range of movement of the horse’s back, yet this restriction is not mechanical but rather is because the horse adopts a stiffer way of moving. The vets concluded that the increase in movement range seen when the saddle panels are enlarged is because the saddle is more comfortable and the weight of the rider more evenly distributed. No doubt saddle manufacturers are already digesting the implications of such research.

Detecting lameness

Have you ever wondered how your phone or tablet knows how to turn the screen around when you invert the device? Most include an IMU that detects movement and knows which way is up.

Expensive and complex clinical IMUs that can analyse motion, like the ones in the French experiment, are now used to detect lameness, especially in the hindlimbs. Vets at the Royal Veterinary College wondered whether the IMU in a smartphone could be used in the same way to analyse pelvic movement and perhaps detect lameness.

They took an expensive lameness-detection system and fixed the IMU to the top of the pelvis of 20 riding horses. They attached an iPhone 6 at the same time, positioning it behind the IMU.

The data from 17 horses was good enough to compare the two systems. To begin with, the iPhone did not perform as well as the specialised equine motion IMU. Yet when the researchers realised that they needed to readjust the IMU in the phone exactly over the middle of the pelvis, the device produced comparable results.

These encouraging results suggest that a relatively cheap but accurate tool could become available to vets in practice just by using their smartphones. Who knows — a lameness app may soon be available to download.

Ref Horse & Hound; 26 January 2017