By Robert Moats DVM & Marian Moats DVM
For a number of years (since 1982), when Rick Redden introduced me to the concept, I have encouraged owners and farriers to rely on radiographs when abnormalities of the foot are involved. This is especially true when laminitis is thought to be or known to be a problem.
This can be a challenge because veterinarians and farriers often don?t cooperate very well. In my experience with these situations I usually find the procedure to be a positive knowledge building and bonding experience where all three parties ? the horse, farrier and veterinarian benefit.
With the advent of modern radiology and crucial knowledge of laminitis and the foot from the likes of Redden, O?Grady, Chapman, and Pollitt, the only x-ray you?re sorry for is the one you didn?t take. To quote Mark Twain ?It isn?t what you don?t know that hurts you, it?s what you know for sure that?s wrong that really hurts you.?
This article is a brief outline of a number of reasons why ?farrier x-rays? are important.
In my practice ?farrier x-rays? historically refer to views of the foot to detect front wall thickness and rotation and accurately measure both. It also detects other details of laminitis and look-alike disorders.
Positioning and aiming the x-ray beam is critical to accuracy. The system I use is to stand both forefeet on lazy susan round blocks. This is amazingly well tolerated. The block is custom built so the top is exactly plumb with the horizontal ?cross hairs? of the collimator of my x-ray machine. The collimator is a lighted site like the crosshairs of a rifle scope. My blocks are round (never out of line to position the cassette). They have lazy susan bearings so that the horse can adjust to small misalignments and have a wire ring embedded in the top. (Figure 1 & 2).
The reason for the wire is to confirm that the aiming is exact. If the positioning is correct the ring appears as a straight line under the foot. (Figure 3). If the floor is off level or the operator (me) makes a mistake the ring appears as an oval and has to be repeated. (Figure 4)
All laminitis is not created equal and is not always obvious. Sometimes an increase in front wall thickness is th only sign. One of the gems of knowledge from Dr. Pollitt?s lecture is the geometry that allows calculation of the normal front wall thickness. Everything above this thickness is abnormal and laminitic and as stated above can be the only sign.
By measuring from the tip of the coffin bone to the navicular joint and dividing by 4, the maximum normal front wall thickness for that foot is calculated.
Prior to Dr. Pollitt?s work, all we had were breed approximations which were inexact in marginal cases. These measurements are now very precise.
The side bonus of farrier x-rays is detecting related abnormalities that may otherwise be hidden.
Seedy toe which often masquerades as laminitis or is combined with it. The separation in these cases occurs from the ground up and often intrudes close to the coffin bone. (Figure a)
Laminitis with separation between sensitive and insensitive laminae which is a much more serious situation when present. (Figure b)
Club feet with contracted deep digital flexor tendon (Figure 6)
X-rays of these cases look dramatic and terrible but often have a much better outcome than laminitis. The case here responded very well to check ligament desmotomy to decrease the tendon pull and allow lowering of the heel and reshaping of the toe. (Figure 7)
With fairly routine follow-up farrier care this horse went from three legged lame to a mid-level riding horse and brood mare.
Additional changes seen on farrier x-rays:
i. Club feet often have remodeling of the ?point? of the coffin bone
ii. Marginal (on the edge) fractures of the coffin bone
iii. Osteomyelitis ? which are changes caused by infection
The above information shows the truth of the adage ?Knowledge is power?. Knowing what you?re dealing with gives much better opportunity for a good treatment outcome.