What is a club foot?
To understand what a club foot is, requires an explanation of two concepts: dorsal hoof wall angle and hoof pastern axis.
In previous blogs, I have written about both the ideal dorsal hoof wall angle (53°) and low dorsal hoof wall angles (below 48°). However, some horses have a dorsal hoof wall angle which is larger than the ideal. An angle which is about 60° (or higher), may be caused by either club foot or a broken forward hoof pastern axis.
The hoof pastern axis is basically defined as a line drawn through the centre of the coffin, pastern and fetlock joints. This line should be straight and parallel to the dorsal hoof wall.
Note that the dorsal hoof wall angle is 61.25° and the hoof pastern angle is 61.21° - this horse has club foot.
When the hoof pastern axis is straight and the angle of the dorsal hoof wall is increased, this is a club foot.
But what is actually going on?
Scientifically, a club foot is a flexor contraction of the coffin joint, preventing normal extension.
But, what does that actually mean? That statement may not mean much to anyone that doesn’t have a significant equine anatomical and biomechanics understanding.
So, let’s break it down.
The coffin joint is the joint between the pedal bone (P3) and the short phalanx (P2).
The flexor tendons - the superficial and deep digital flexor tendons flex (think flexion test) the lower limb. The superficial flexor tendon inserts onto P2. The deep flexor tendon inserts onto the navicular bone and P3. The tendons on the front of the limb are extensor tendons, meaning that they extend the limb, making it straight.
Horses with club foot have a shortened deep digital flexor tendon, making it impossible to extend the coffin joint - so although the extensor tendons are not actually effected, because the deep flexor tendon is shorter than it is supposed to be, it cannot be stretched/ elongated enough to allow for extension of the limb.
This results in more weight bearing further forward as the horse can’t easily put down its heel, eventually resulting in increased heel development and a steeper toe.
This does not always affect both feet. Growth rings on the affected foot are generally wider at the heels than at the toe. The hoof wall can then start to become dished, and the tip of the pedal bone can start to change shape and fracture.
Club foot in foals
This can be:
Congenital (born with it) - generally affects the right fore.
Acquired (develop over the first 6-8 months of life).
Lameness is not usually severe, and radiographs would be exceptionally useful to assess any joint changes.
Conservative treatment with anti-inflammatories and muscle relaxants can be performed in mild cases, together with gentle lowering of the heels and rolling of the toe every two weeks. If the sole bruises, a composite can be applied to protect it.
In more severe cases, which are unresponsive to trimming and medical treatment, surgery to cut the accessory ligament of the deep digital flexor tendon may be recommended.
Club foot in older horses
Club foot in mature horses can lead to decreased athletic ability and lameness as more weight is loaded onto the dorsal hoof wall and sole growth rate decreases. This causes poor performance as the stride length shortens.
As the load is transferred through the front of the foot, encouraging toe-first landing, these horses are more likely to get toe cracks, white-line disease and chronic laminitis.The high hoof angle can also lead to coffin joint inflammation (and subsequently arthritis) and increased strain on the suspensory ligament of the navicular bone.
The top two photos show the foot after the farrier performed the trim that he was comfortable doing based on visual assessment of the hoof. After obtaining the radiographs, we were more confident in being able to remove more of the heel, resulting in a significantly improved dorsal hoof wall angle. This horse will be having a few days off and some anti-inflammatories to help acclimatise to its new biomechanics.
Farriery should be carried out every 4 weeks to gently reduce the heel height in a tapered way from the apex towards the heel. A shoe with a rolled toe can decrease the strain on the deep digital flexor tendon.
The amount of heel to be trimmed away can be ‘measured’ by putting a wedge under the toe. This would strain the deep digital flexor tendon. If the horse copes well with that degree of strain, then that amount of heel may be removed.
Using glue-on polyurethane shoes may be necessary due to the poor hoof quality and to help contracted heels to relax, and impression material can be used to help load the sole evenly.
In more severe cases, surgery can be performed to decrease the strain through the deep digital flexor tendon by cutting the check ligament, followed by a 3-6 month period of rest and continued remedial trimming.
Conclusion
Although club foot is generally a genetic condition, getting on top of it early can help to reduce long term orthopaedic issues and improve long term performance capabilities.
Further reading
Hunt, R., 2012. Management of Clubfoot in Horses: Foals to Adults. In: AAEP Annual Convention.