Q: What is ‘DP imbalance’ and how can I assess it?
A: In addition to balancing the left and right halves of the feet, the farrier will also want to evaluate the balance from front-to-back of the foot. This is called the dorsopalmar balance when talking about the front feet, and the dorsoplantar balance when discussing the hind feet. You may also see the term anterior/posterior balance used for both front and hind feet. Farriers and vets sometimes use the shorthand of DP balance or AP balance when discussing this.
In terms of DP balance what you ideally want to see is a foot with approximately 2/3 of its mass in the back of the foot, behind the true apex of the frog (about ½ inch behind the front point of the frog) and 1/3 ahead of the apex of the frog. This equates to a hoof that has about 50% of its mass both ahead and behind the axis of rotation of the coffin bone, a point which corresponds to the widest point of the foot.
A foot with good DP balance will provide a strong base of support for the limb, maximizing the ability of hoof to bear weight and dissipate concussive forces. Importantly, it will also allow for the point of breakover to be established that puts minimal strain on the joints and soft tissues. When the front part of the foot is longer than the back part, this is called DP imbalance. When a foot has this conformation, as is common in horses with long toe/low heel syndrome, breakover will be delayed, which can cause various problems for the horse.
To assess DP balance draw a line across the widest part of the foot. If approximately 50% of the foot is behind this point and 50% in front of it, then the balance is good. However, it is important to note that the front of the foot measurement must be taken from the line you have drawn to the breakover of the toe, which is the most forward point where the hoof would contact the ground if standing on a flat surface. If there is a bevel in the shoe or toe, the point of breakover is where the bevel starts.