Parameters of Hoof Balance

Hoof-pastern axis and a common problem called “negative palmar angle.

The term “hoof-pastern axis” refers to the alignment of coffin bone and pastern bones. The textbook ideal is a straight line through P3, P2, and P1 (coffin, short and long pastern bones). An x-ray will confirm bone alignment. But the “eye-ball” method of looking at external hoof and pastern can give you a general idea. Bone alignment is important for biomechanical efficiency, which means a horse will move with as little effort and as little damage to himself as possible. Most horses do not have textbook perfect hoof pastern alignment. But one of the goals of hoof care is to balance the foot to achieve the best alignment for each horse.

To assess the hoof pastern alignment, look at your horse from the side, so you see a lateral view of the hoof and leg. Make sure the horse is standing square with the cannon bone perpendicular to the ground. As discussed last week, some horses have trouble standing square if holding their limbs ahead or behind normal is their preferred posture. You cannot properly evaluate the hoof pastern axis unless the horse is standing with cannon bones perpendicular to the ground because the joint angles will cause an optical illusion making the hoof pastern axis appear abnormal.

Seen from the side, if you draw an imaginary line through the hoof at the angle of the dorsal hoof wall, notice if that line continues through the pastern. Deviations from normal include a broken forward or broken back hoof pastern axis. A club footed horse is an example of a broken forward axis. A horse with an under-run heel often has a broken backward axis. Sometimes the hoof pastern axis can be easily corrected by trimming or shoeing changes. In other cases, conformation limits what a farrier can do to change the hoof pastern axis. Remember this is only one parameter of hoof balance. If other aspects of hoof balance are good, a horse with some deviation in hoof pastern axis can be fine with no lameness or performance problems.

Before Trim

Now I will cover a variant of a broken back hoof pastern axis that occurs more commonly in the hind feet. Look at this photo, taken before trimming. (See Image : before trim) Notice the broken back axis. When x-rayed, feet that look this way tend to have the coffin bone tipped backwards (the tip of the bone points up, the opposite of what happens in laminitis rotation). Sometimes these feet have a “bull-nosed” appearance to the dorsal hoof wall. In this case there was too much hoof wall growth in the front of the foot, creating a long toe.

After trimming the front of the hoof only; no heel was removed, you can see the appearance of the hoof pastern axis has improved greatly. (See Image : after trim).

After Trim

What causes this broken back axis? Sometimes it is the way the horse stands. As discussed in last week’s blog, posture has a significant impact on hoof growth. If the horse stands camped under with the hind feet, heels will wear down and toes will become longer in between farrier appointments. This kind of abnormal angle tends to develop slowly, usually over the course of several shoeing cycles. A little extra toe wall length doesn’t look abnormal at first. But by the time it becomes obvious to our eye, this problem has been progressing for some time. At first the horse adapts and no problems are seen. Eventually horses with negative palmar angles will start to have performance problems. Commonly they get sore hocks and eventually pain in their lumbar spine and pelvis.

If you think your horse is developing negative palmar angles on the hind feet (it can happen in front, its just more common behind), talk to your farrier as well as your veterinarian. Trimming should help but if the cause is from abnormal posture, your vet may find  joint or myofascial pain that causes the horse to stand abnormally. Do not be quick to blame anyone! Some horses just have this tendency. Once identified, you can often change it with a combination of more frequent farrier appointments and musculoskeletal treatments from your vet.


Copyright © 2012 ~ Dr. Lisa Lancaster DVM, WDAA Blog Author

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