2014 Equine Podiatry 101 Written and presented August 2014 by R.F. (Ric) Redden, DVM
Club feet are one of the most common deformities throughout the horse world. There are many unverified hypothesis regarding the trigger mechanism for this syndrome, however none have been scientifically proven. It is universally accepted that the deep flexor muscle fibers have an abnormal degree of persistent contraction, thereby shortening the overall length of the muscle belly, which creates a shorter distance from origin to insertion at the base of the coffin bone. The DDFT can only stretch about 1% of its full length and increased contraction suspends the caudal aspect of the coffin bone and increases the palmar angle (PA). The higher the grade, the greater the PA becomes.
In the early 1980s the author developed very simple yet specific criteria for four basic grades of club feet. This simple classification system has helped vets and farriers better communicate and provides a precursor for developing a treatment protocol. See diagram below of the four grades.
This syndrome affects the foot in several different ways to a degree that is relative to severity:
The heels grow at an accelerated rate as they do not incur natural internal download. As the PA increases, so does heel growth. The heel, however, does not grow and push the horse upward. Rather the PA is suspended and the heel only lightly loaded, which accelerates growth.
The frog is short, narrow and set well into the foot as internal download is inadequate. It is also suspended in a very unnatural position.
The digital cushion becomes quite large and can be seen filling the heel bubs and lower pastern in mid to higher grades. It is also suspended as it is carried upward with the PA.
Growth rings in the heel soon become wider as the grade increases and heel growth accelerates.
Growth rings at the toe are diminished in width as the blood supply to the germal centers is compromised by internal forces. Therefore growth is slowed relative to the degree of contraction.
The wall starts to dish, especially if the heel is reduced in height as a means to make the foot appear more normal. The bending action is the result of increased tension from the DDFT on the toe, which in most all cases is a weaker component than the tendon, especially in growing, developing feet.
Sole growth is slowed or ceased altogether as a result of increased DDFT tension on the apex of the coffin bone, causing it to tip downward and press into the sole corium. The cup of the foot vanishes as the sole is pushed towards the ground surface.
The coffin bone begins to remodel due to the unrelenting pressure of the very thin and very sharp-edged palmar rim against the sole corium, which compresses the blood supply that nourishes it.
The wall at the toe becomes very thin and unable to protect the terminal laminae and adjacent sole. Cracks and fissures develop due to lack of adequate horn protection. Tenderness and lameness frequently occur because the horse is out of foot.
If the foot is subjected to a wet environment and water, bacteria and debris find their way into the fissures described above. This often results in an abscess in the young foot that many times will break at the coronary band. Individuals that toe out tend to break on the inside of the toe, while those that toe in often break an abscess on the outside of the toe, and a few will break center toe. Reviewing the past history of many cases with unilateral white line disease, the author finds a direct correlation exists between white line disease and where the abscess breaks on a club foot. The vast majority of all white line disease cases have been in the club or higher heeled foot.
How to manage the club syndrome
Club feet can be managed by reducing the forces at play. Decreasing the tension on the DDFT relative to the required mechanical release greatly diminishes heel growth and accelerates toe growth. When this occurs, there will be rapid sole proliferation. The cup of the foot will reappear and the dish will grow itself off in a few months. Mechanics are a management tool that can offer a great option when surgery is not feasible.
Most low grades clubs (1-2) do quite well by simply rockering the shoe at a point directly beneath the center of articulation (about the widest part of the foot) and loading the heel at the widest point of the frog, establishing a zero PA with the palmar rim and heel branch and maintaining maximum heel mass.
Higher grade clubs (2 to 3) may require an inferior check desmotomy as an aid to lengthening the musculotendinous unit. Creating a 0° PA with the load surface of the shoe and a slight toe extension prior to surgery offers best results. Maximize the gap between the severed ends of the check ligament as much as possible at the time of surgery. PA should be weaned down slowly after surgery to prevent post op pain as many other structures are involved and need time to relax.
A DDFT tenotomy may be required for the high grade 3 and 4 cases. This offers maximum lengthening of the musculotendinous unit. Even cases with a 40-45° PA are candidates for this procedure. The earlier in life the check and/or tenotomy is performed, the less scar tissue is present and the better the long term prognosis for athletic soundness. Surgery should be considered before irreversible bone damage has occurred.
When PA cannot be maintained and heel continues to outgrow the toe, surgery should be considered provided breed rules approve of the procedure.
Inferior check desmotomy:
Trim goals: establish a small flat area at the heel parallel to the palmar rim. Use an aluminum shoe glued on with Equilox. Avoid Equilox on the sole and protect any small fissures with wax or clay to avoid an abscess.
The foot must be held up while glue is curing. Once the Equilox has cured apply a large wedge of Advance Cushion Support (ACS) or similar product and tape it on. This offers protective mechanics that prevent further damage as the shoe alone greatly increases DDFT tension. Leave the rubber wedge on for a few hours post-surgery, whether performed under general anesthesia or standing (the author’s preferred method). Trim 1/3 of the rubber height off every few hours or days as a slow wean down aid. This greatly reduces post op pain.
Mid-cannon DDFT tenotomy: