When you hear the word ?laminitis? you probably think of grain-room break-ins, retained placenta, serious illness/colic or metabolic disorders. However, there is a more insidious form of laminitis that can threaten the soundness of many more horses than all other causes combined.
The laminae can be compromised when the hoof isn't functioning the way it was designed to function. Although the laminae secure the coffin bone to the hoof wall, the bone column is also meant to be supported from below by a nicely arched, concave sole as well as the frog, bars and digital cushion.
In a healthy hoof with good supporting structures, a lateral X-ray will show the top of the coffin bone (called the extensor process) sitting at the level of the coronary band. When the hoof isn ?t correctly supported from below, the bone column sinks down too far into the hoof capsule, even to the point that part of the pastern is located within the hoof capsule.
In short, the changes seen on radiographs look like a horse with laminitis and sinking. The only difference is that they slowly develop over time rather than being a sudden event. The lameness also develops insidiously.
Characteristics of a hoof with mechanical laminitis include:
- Shallow collateral grooves at the tip of the frog
- Little to no concavity
- ?Thin soles?
- Stretched white line (lamellar wedge)
- May be a flare at the toe on side view
- Long toe length, measured from coronary band to end of toe.
As you might imagine, these horses eventually become ?tender footed? and sensitive to hard or uneven ground. They bruise easily. Hooves tend to flare because of poor laminar attachments. Coffin bone remodeling and bone loss (pedal osteitis) is common. The coffin joint can become inflamed. The progression to lamenesses is accelerated in horses that jump or work at speed. The hoof wall eventually becomes long because the coffin bone and corium are too close to the surface to allow trimming back to a normal length.
If you have been reading Horse Journal for a while, you know we frequently recommend that horses go without shoes when not being actively worked.
If allowing the horse to go barefoot was done more often, we believe this dropping of the bone column and mechanical laminitis would be much less common.
This is because most shoes are set in such a way that the frog doesn't contact the ground and weightbearing occurs only along the walls, rather than the sole and frog. If the horse goes barefoot for a few months, he may rebuild the strength of the sole and frog.
Once the sinking process has begun, these horses quickly become too sensitive to go without shoes, and this creates a real Catch-22. If you don't shoe, the horse is sore, but if you shoe, the problem worsens.
When shoes alone don't keep the horse comfortable, pads are typically added and can help for a while. If possible, a domed pad to stimulate the sole and frog, or the use of hoof packing under a pad, can help to stimulate sole growth. A few shoeings with packing and rocker shoes, which are curved along the ground surface, may also speed up the process.
For a longer-term fix to the problem, Pete Ramey (see sidebar on page 11) recommends rounding or beveling the toe at ground level, from about 10:00 to 2:00 looking at the hoof from the bottom.
This takes the pull off the laminae and also maximally stimulates the sole and frog. The horse is kept in padded boots until sufficient concavity is obtained for the horse to be comfortable barefoot.
Whether the hoof is shod or left barefoot, comfort may be achieved in as short a period as two months. However, it will take several more months for ideal bottom support to occur. Light exercise can resume once the horse is comfortable, but not until.
You can help prevent weakening of the support structures of the hoof by allowing the horse some downtime barefoot every year. If you already have a tender-footed, thin-soled horse that fits the criteria for mechanical laminitis/distal descent, don't use shoes and pads as a Band-Aid. Work with your farrier to achieve better ground support to actually fix the problem before more damage is done.