Measuring the Hoof
Metron supports a process called "Guided Mark-Up" in which the user is prompted to pick key points in certain images of the equine digit, and Metron then uses those picked points to compute many important parameters of the hoof's conformation. The notion of "Guided Mark-Up" is powerful because it gives a repeatable means for different practitioners to measure certain quantities. Prior to the advent of Metron's method, practitioners used terms liks "contracted heels", "broken-back pastern", "long toe", "rotated coffin bone", and more without very much in the way of a repeatable definition by which to really quantify these things. Guided Mark-Up also allows anyone, whether a hoof expert or not, to do the work of gathering images and doing the mark-up. This fact allows many veterinarians using Metron to assign much of the effort to a vet tech or other person at their clinic, helping the veterinarian make the best use of his or her scarce time.
Metron supports Guided Mark-Up for 5 different images of the foot: 2 are radiographs: the lateral and the DP (sometimes called "AP"), and 3 are
photographs: lateral, frontal, and solar. Each of these images shows different aspects and allows different measurements to be made. The Metron user can use any one of these 5 images, or all 5 of them when analyzing the hoof.
What things of importance does Metron measure? If the 2 radiographic images of the foot are used, Metron generates a total of 17 different
measurements. These 17 measurements include virtually every measurement described in the veterinary literature, and more. In the typical use of Metron, the practitioner selects anywhere from one to five of these measurements to overlay on the image and display, but all 17 are computed and are in the Metron database. The developers of Metron have spent many hours in discussions with prominent veterinarians and farriers who have an interest in the equine digit, among them Richard Mannsman, Ric Redden, Mike Savoldi, Gene Ovnicek, Robert Bowker, Chris Pollit, Barbara Page, Dave Duckett, Hans Castelijns, Stephen O'Grady, and Tracy Turner. Through discussions with these experts we have confirmed our techniques and made additions to our method. Listing and explaining all 17 of the radiographic parameters measured in Metron would be a lengthy discussion, but here are perhaps the top 7 measurements that are important to equine podiatry:
1. "The Palmar Angle" - The angle between the underside of the pedal bone and ground. Around 5 degrees in a healthy horse, this measure is one way that some practitioners like to measure rotation of the coffin bone.
2. "P3 Distance to Ground" - This gives a measure of the thickness of the sole, which most practitioners measure just under the tip of the pedal (or "P3" bone). Metron's ability to accurately calibrate the image and compensate for the inherent magnification in radiographs is important for this and any other linear measurement.
3. "P3 Descent" - The vertical distance from the hairline at the center of the front hoof wall down to the highest point on the P3 bone. This is used as a measure of the bone "sinking" relative to the hoof capsule, a condition which can occur as a side effect of founder.
4. "Toe/Support %" - This measures the length of the foot in front of the articulation center of the coffin joint as a percentage of the entire foot length. This is a measure of whether the hoof has a "long toe" or "short toe" in a biomechanical sense, relative to the joint axis.
5. "Coffin Angle" & "Pastern Angle" - These are measures of how the horse is standing, and they quantify terms such as "broken-back pastern" that one hears in the field.
6. "Coffin-Joint Tilt" - This measure, made from the DP (or "Frontal") radiograph measures what is called "medial-lateral balance" by measuring how nearly parallel the coffin-joint's biomechanical axis of rotation is to the ground. The common belief is that the hoof should be trimmed so that this is parallel to ground.
7. "Hoof Angle" - This is a very basic measure, the angle made between the front hoof wall and the ground. This parameter is computed in Metron from the lateral radiograph or the lateral photograph.
There are 10 more parameters computed from the lateral and DP radiographs in Metron. These other 10 are perhaps of somewhat less frequent use in the literature, but are important to certain practitioners and in certain cases. It is extremely likely that any measurement of interest to the equine podiatrist is already supported as a standard measure in Metron. From the 3 photographs that Metron analyzes using Guided Mark-Up, there are
an additional 24 measurements made. Thus, Metron can produce a total of 41 measurements of the hoof if all 5 images are used in the analysis. Of course, there is no requirement to use all these images -- the lateral radiograph, itself generating 10 measurements in Metron, is the single most important
image to analyze. From digital photos of the hoof, Metron measures important parameters such as Hoof Angle, Heel Angle, heel height, Contraction of Heels, Widest part of Foot, Toe Length, Medial and Lateral Flares, etc.
Published papers by independent university researchers have tested the Metron system for accuracy and have concluded that it is capable of making accurate and useful measures of the hoof. No other software system exists which makes these measurements - one reason is that the Metron system has been granted a US patent.
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