Break Over break down, the Toe

This post is to offer insight on a topic that comes up frequently on Facebook and so many other on-line forums. The toe of the horse and the discussions concerning break-over fascinate me. The most recent post to catch my eye was seen on a popular farrier’s group on Facebook. The farrier was asking why some farriers chose to set the shoe back, leaving in their opinion too much toe exposed forward of the shoe. The question was harmless enough, but because there were so many conflicting opinions the thread became ugly quickly.  How you define break-over and what your take is on toe function is what will ultimately form your opinion.

I spent some time surfing other blogs and forums attempting to get a general consensus of how farriers at large determine break-over.  Yes, I said attempted. There is no general consensus. Oh yes there are the self-proclaimed bibles of horseshoeing that some insist are gospel, but having followed their input it became clear that most practicing farriers view published text on break-over as; how should I put this “more like guidelines”. This is perhaps best given that the only thing the experts can agree on is that the foot needs to be in balance

Before you can discuss break-over with someone you first have to be on the same page when it comes to understanding the function of the toe. What is the function of the toe? Ask any horse person, or non-horse person what the function of the toe is and they will say without hesitation to aid in locomotion, common sense right?  

My take on the function of a structure is based on my understanding that a structures conformation and the property of the tissue that it is composed of determines its function. The toe is comprised of the dorsal hoof wall, its white line, and the sole forward of the point directly below the tip of P3 (in a balanced foot half way between the apex of the frog stay and the junction of the sole to white line). The hoof wall is not homogenous, meaning it is not the same density from its outer surface to its inner surface, but is rather a matrix of densities. The outer most areas of the hoof wall (stratum medium) is dense, consisting of hard horn, and as you progress inward the density within the matrix becomes less. The inner most areas of the hoof wall (Stratum internum) and its inner surface are pliable. The junction or union of the inner most surface (Stratum internum) often called the insensitive lamellae with that of the sensitive lamellae (epidermis to dermis) is an area or zone that must also have its function defined.

The hoof wall matrix of the toe contains primary tubules that originate at the coronary band, and laminae derived horn known as stratum internum. I am simplifying things for the purpose of this blog post, but what is important to understand is that the properties of the hoof wall are determined by the ratio of primary tubules to laminae derived horn. Read more on hoof wall matrix

 Primary tubules are high in density and provide rigidity and structure to the matrix, and laminae derived horn is pliable. The higher the ratio of primary tubule to laminae horn the harder the wall, the more resistance to deformation it possesses. As for the toe, there is a higher ratio of primary tubules to that of laminae derived horn than for example at the heel, where we find a higher ratio of laminae derived horn allowing for deformation without failure. The ratio of tubule to laminae horn is determined by the dermis and foundation conformations. The toe serves many functions, but its primary function is to support locomotion. The hoof wall of the toe with its epidermal to dermal junction also aids in dissipation of excess energies created by the leverage of break-over. 

The functions of the toe and the structures that comprise it are what determine how it is treated in a given situation. Over dressing of the healthy toe compromises its functions, while setting the shoe back to speed break-over shows a disregard for toe function and its roll in over-all foot function.

Disregard for toe function

There are always going to be circumstances where health of a structure dictates intervention, but our efforts should always be to promote healing of the weak structure, while doing our best not to compromise the function of another (Do No Harm).

There are often ways to promote stimulus for the development of health in a given structure without comprising the function of another. It is important to understanding and respect the role each structure plays in foot function. We can then start respecting foot function by applying a balanced trim. In a future series, I will offer my insight into balance and how the application of various appliances affect the toe’s functions.