Navicular Syndrome is a term that has been used to describe a painful condition in the heel region of the horse that causes
lameness. It has also been called Navicular Disease. But the term Palmar Foot Pain is more encompassing in that there are
several closely related structures in the navicular bone region that can result in similar clinical signs of lameness as frequently
as degeneration of the navicular bone itself. The increased use of MRI to diagnose PFP has redefined navicular syndrome as a complex lameness.
PFP horses show a shortened stride in the lame limb or limbs. This is almost always a front-end problem,
so it can appear as though the horse is stiff in his shoulders.
PFP horses may increasingly stumble with a toe first hoof landing, and seem to have a choppy trot. Head bobbing
at the trot is often noticeable especially if the horse is trotted in a circle on firm ground. Usually one foot
is more sore than the other, but often both feet are affected. The onset may be slow or sudden, depending on
circumstances of shoeing, husbandry and usage.
To localize the lameness to PFP a thorough clinical exam is necessary. Hoof testers applied over the middle of the frog will
often demonstrate pain, and there may be pain when the heels are compressed. Nerve blocks with local anesthetic to temporarily deaden
the foot and coffin joint can isolate the area of pain to the heel region.
Pain in this region rarely comes from deterioration of the navicular bone alone but is often compounded by damage to the navicular bursa, tendonitis
of the deep digital flexor tendon within the hoof wall, the impar ligament, the navicular suspensory ligaments or the collateral ligaments of the coffin joint.
More than one of these structures may be involved at the same time. Bruises, corns, punctures, abscesses and even fractures can also cause heel pain. Therefore,
a diagnosis of palmar foot pain can usually be made, but isolating the individual cause can be more challenging. X-rays are used to examine the bones of the
foot, and ultrasound images can detect some damaged tendons or ligaments in the navicular region.
Referral institutions have advanced diagnostic techniques such as nuclear scintigraphy, MRI and CT available that can be very useful in particularly difficult
cases and are sometimes needed to specifically diagnose the problem.
Treatment is varied depending on the diagnosed cause but always involves careful attention to foot balance and proper shoeing techniques. Protective pads,
raised heels and egg bar shoes have a place in various cases. Usually a rest period with anti-inflammatory medication is prescribed, especially when ligament
damage is diagnosed. Injection of the coffin joint or the navicular bursa with cortisone and hyaluronan (Hyalartin V, Legend HA and others) can be beneficial
in some cases. Shock wave therapy benefits some horses. Recently, IV injections of Tiludronate have been shown to normalize bone metabolism in the navicular bone
itself when that structure is involved in PFP. More refractory horses can be helped with desensitizing the navicular region either by medically treating the palmar
digital nerves, or as a last resort, surgically severing the nerves, which removes sensation to the heel and part of the foot area. Finding the most effective management
methods is sometimes a matter of trial and error. Each horse responds in different ways likely because no two cases of Palmar Foot Pain are exactly the same.
It is also important to note that PFP can be a career ending or career altering condition, but in many cases the horse can still have useful years given proper care.
