Navicular Disease and Fracture
Q. - I have a 17-year-old Paint who was diagnosed with navicular disease when he was 2. Recently I had him X rayed again and found out that he has a fractured navicular bone that has calcified. I have seen magnetic bell boots available on the market and was wondering if these would help with the pain. Also, is there any type of treatment or surgery that can repair this?
A. - Navicular syndrome, a degenerative disorder of the navicular bone and the surrounding heel structures, is one of the most common causes of lameness in horses. The navicular bone is a small bone that lies within the horse’s hoof, behind the coffin joint and near the back of the heel. The deep digital flexor tendon runs down the back of the limb and behind the navicular bone, using it as a fulcrum to flex the coffin joint. Navicular syndrome generally causes a chronic lameness affecting both forelimbs, though the horse is often more sore in one foot than the other. Owners may notice that their horse has a stiff or shuffling, short-strided gait. A mild intermittent lameness may be present first, along with difficulty turning sharply, but the lameness can worsen to severe and debilitating over time. Several factors can contribute to navicular syndrome development, including poor conformation, heavy work, and improper trimming and shoeing.
Navicular syndrome is managed rather than cured. Therapeutic hoof
trimming or shoeing is a cornerstone of treatment, and your veterinarian
and farrier should work together to restore hoof balance, reduce strain
on the navicular region, and protect the injured areas. Joint and/or
bursa injections might help reduce heel pain and inflammation.
Non-steroidal anti-inflammatories such as phenylbutazone can provide
occasional pain relief. Sometimes other medical treatments are used, but
no single treatment works for all horses. Palmar digital neurectomy, a
surgical procedure to cut the nerve that provides sensation to the heel,
should be used as a last resort for pain control. This procedure may
have several adverse effects and does not offer a permanent solution to
lameness, as many horses regain sensation in two to three years.
To fully understand your horse’s condition, it would help to know how
lame he currently is and the fracture’s configuration, because those
will affect the treatment options. One fracture type involves small oval
or round fragments on one or both sides of the navicular bone’s distal
(lower) border, embedded within the impar ligament. These distal border
fragments are pieces of bone that have pulled off of the navicular. They
are found in 24-40% of horses with navicular syndrome and are likely a
result of the bone degeneration I described earlier.
Another type of fracture occurs due to trauma, such as when a horse
kicks a wall. Most of these break in a vertical direction, causing the
bone to split into two parts. Unlike the progressive bilateral lameness
of navicular syndrome, a horse with a traumatically fractured navicular
bone has acute lameness that affects only the fractured limb and may be
severe.
Conservative treatment for a fractured navicular bone involves an
extended rest period and corrective shoeing to stabilize the foot and
relieve stress on the bone. Even after a prolonged healing period, the
navicular bone often heals with fibrous tissue instead of a true bony
union. The prognosis for return to soundness is unfavorable, and a
neurectomy is often necessary if athletic work is the goal. Surgical
repair using a screw is an option to provide greater stability and
healing potential, but the procedure requires a facility with special
equipment. With surgery the outlook for athletic use is still guarded,
but pleasure riding may be possible.
