Thermal image of a horse with inflammation in the flexor tendon just below the knee.
Thermal image of a horse with inflammation in the flexor tendon just below the knee. Cool or normal temperatures are in the blue - green - yellow end of the spectrum. More active areas show up with a localized accumulation of red or white in the hottest or most inflamed area.

Thermography

Thermography is a non-invasive technique, whereby a camera with a sensor measures the infra-red emissions from a horse’s body. Once the information is recorded, it enters the camera and the temperature variations are depicted in the display with different colors corresponding to different temperatures.

Essentially what we can see is the horse’s body, then we look at specific areas and compare them between one leg or one site and another. After images are recorded in the camera they are then downloaded into a computer that analyzes the data and generates a report which indicates the relevance of the temperature variations.

The reason that heat detection is important is because the presence of heat is considered one of the cardinal signs of inflammation. The human hand is able to appreciate, in some circumstances, a change in temperature of 1.0 degrees C, while this camera can detect changes down to 0.1 degrees C, a ten-fold improvement. In addition to heat, the camera will also appreciate cold areas. Heat or inflammation is generally a result from hemorrhage, external or internal trauma, tendon or joint inflammation and/or infection. Conversely, cold may be seen with decreased circulation, non-active swelling such as edema or in the presence of obstruction of blood flow.

Thermal image of heat emission from the inside of the fetlock area. The affected site is circled and compared with the region on the other limb and a statistically significant lesion was found. Ultrasound examination yielded information on damage to the ligaments.

There are many applications for this technology in equine practice and we intend to use it as follows: early lameness detection, hoof balance, saddle fit, back soreness, and any lameness condition that may involve joints, muscles and/or tendons. As you can see it has a role in almost all aspects of soundness evaluation. The ability to diagnose a mild unevenness before it becomes an active clinical problem will be of immense benefit. There are many early soft tissue - tendon, muscle or ligament - injuries that are not apparent until they become more active and difficult to manage.

Hoof balance is a difficult area to appreciate in some horses, but an instability in how the foot contacts the ground can influence a horse’s soundness. By using Thermography, "hotter" contact areas would indicate excessive pressure or an imbalance in certain parts of the foot. This may be of benefit to the farriers and for all of us when we are trying to discuss a condition that is not always obvious.

Thermography works as an excellent screening tool. Prior to a show or for a pre-purchase examination, the camera could be used to determine if there are any active areas, even if the horse is currently sound. We wouldn’t recommend that Thermography be used for anything more than screening during a pre-purchase as the rest of the exam plus radiographs will be necessary to validate any findings.

Thermal image of a horse's hocks, the picture was taken from the front legs looking back to the hind limbs. The increased accumulation of red in the left hock (right side of image) indicates active inflammation. This horse subsequently had the hocks injected and her unsoundness improved. Thermography was chosen because the unsoundness was mild and the x-rays did not indicate any obvious reason for this problem.

Its use in the location of temperature variations between limbs or other areas on the body will be the most common role. Being able to quickly include or exclude a region during a lameness work-up will decrease the time spent on a diagnosis and allow for a more comprehensive approach to treatment. Frequently we will see a horse, for example, with a sore fetlock joint, but not fully appreciate the soreness in the suspensory ligament or maybe a hock soreness linked with a back problem. It may be easy to diagnose the primary or active problem, but to not fully appreciate the secondary problem that may have developed. By imaging other regions it's possible to see these less active areas that may not readily present themselves during a typical lameness work-up.

Saddle Fitting and Thermography

Thermographic image looking from hips forward to withers.
Thermographic image looking from hips forward to withers.
Thermographic image evaluating underside of saddle. Increased heat detected indicates increased saddle pressure and improper fit.
Thermographic image evaluating underside of saddle. Increased heat detected indicates increased saddle pressure and improper fit.

In these two images Thermography is used to identify back inflammation and issues with saddle fit. In the left image there is an increase in heat output in the left hip and sacro-iliac region relative to the right side. Based on the depth of the hip area this would be considered a significant amount of heat output. Further forward of this there is a very localized area of inflammation (see the red area) that corresponds to excess saddle pressure. Checking this region with palpation would very likely indicate back soreness. The image on the right is an example of how thermography can be used to direcly evaluate saddle fit. Just after a horse has been ridden, the saddle is removed and evaluated. As with examining a horse's back, direct imaging of the saddle may indicate where uneven pressure correlates to back soreness and saddle fit issues.

In the past, when we have difficulty locating a lameness through traditional methods, horses have been referred for procedures such as thermography or nuclear scans. We are quite excited to be able to provide part of the service that previously would have only been available at larger, specialty centers. There still may be a need for nuclear scans, but we expect to be able to diagnose the majority of those difficult lameness cases here.