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Navicular Syndrome

16 August 2011 No Comment

Navicular Syndrome
By: Ride ‘Da Kur

Navicular syndrome (NS), is the most common cause of lameness in the front legs of horses. We are still unsure why NS occurs. Navicular “disease” has never been justly defined, therefore, Researchers and Lameness Specialists have substituted the term “disease” with “syndrome”. Syndrome: a commonly recurring group of symptoms of unknown cause.
It is not always possible to reveal the exact cause of NS. A very large diversity of problems can cause NS, so it is very difficult to diagnose and treat the syndrome. NS is determined by many conditions which all have the same symptoms: pain in the back of the front feet.

The Navicular Bone & Deep Digital Flexor Tendon:

The navicular bone is located directly behind the coffin bone, wedged in between the short pastern and coffin bone. By being wedged in between the two bones, the navicular bone increases the size of the coffin joint, permitting the joint to absorb more force and concussion.

The deep digital flexor tendon stretches from the coffin bone, under the navicular bone, to the upper back part of the horse’s leg. The navicular bone acts as a pulley on the deep digital flexor tendon, which takes a sufficient amount of stress off the coffin bone by absorbing a majority of it.

The Difficult Diagnosis:

Since Researchers have not directly proven a cause for NS, diagnosis can be very difficult. Keep in mind that after all diagnosis, you could still be left guessing. The diagnosis must consist of (1) verifying that the navicular area is where the lameness is originating, and (2) ruling out known causes of lameness in that area.

Researched Causes For NS:

There are many causes for lameness in the horse’s foot. Here’s a bundle of them: Corns caused by many factors (shoes left on for too long, tearing of the laminae, inward movement of the hoof wall) all resulting in bruising in the area; quarter cracks and cracks in the wall of the foot, puncture wounds and/or subsolar bruising on the frog, sheared heels, thrush, synovitis of the coffin/navicular joint area, contracted feet, lack of oxygen circulation, cross-firing/over-reaching injuries, inflammation, infection of the lateral cartilage, sidebone, adhesions, fractured navicular bones, joint soreness, deteriorating cartilage, bones and/or tendons…etc, etc, etc.

Okay, now let’s take a look at a few of these in detail:

Cartilage: This is the most common indicator of NS. 50% of horses with NS have cartilage problems. The bottom surface of the navicular bone (which rubs against the DDFT, acting as a pulley), may deteriorate, causing sharp edges that will damage the deep digital flexor tendon.

Ligaments: The navicular bone is connected to other bones in the foot by the impar ligaments. The impar ligaments have many nerves which may be disturbed, therefore, causing pain.

Ischemia: Low oxygen levels in the tissues and bones are caused by blood clots. When the navicular bone (or any bone) cannot get enough oxygen, it becomes painful for the horse. Researchers hypothesize that, in time, the bone is likely to degenerate, resulting in permanent lameness.

Tendons: The deep digital flexor tendon runs down the back of the horse’s leg, connecting to the coffin bone. This tendon’s angle is maintained by the navicular bone (which acts as a pulley). This tendon can become damaged in many ways: (1) adhesions – limits the tendon’s movement and may cause erosion of the navicular bone, (2) lesions – bruises and torn fibers causing pain, (3) fillibration – frayed and/or brittle tendons are a common symptom of NS.

Treatment:

I think everyone agrees that the best treatment for any problem is prevention. Studies show that horses stay healthier when pasture-kept with less physical demands. Provide the best possible hoof care for your horse on a regular schedule. Don’t work horses on hard or irregular surfaces (ex. pavement or gravel). Be sure to sufficiently warm-up and cool-down your horse before and after every ride. Avoid repetitive movements that cause concussion to the horse’s feet (ex. sloppy jumping, pavement riding, endless gallops, and poor riding posture).

Since there are several causes of NS – some still unknown, one treatment will not work in all cases. Be patient and talk with your veterinarian and farrier on all appropriate options. Studies show that horses have nearly 90% chance of recovering if they have been lame for no longer than 1 year. A definite change in work will be needed for the horse to heal properly, including pastured turnout.

Shoeing: 30% of horses improve with good trimming and/or shoeing. Talk with your farrier about different shoeing possibilities. Have your farrier correct any imbalances in the horse’s foot, and consider using egg-bar shoes or pads to protect the rear part of the foot.

Isoxsuprine: This medication is banned by the AHSA. It has an overall success rate of 60% and is available at a low cost. This drug is known to increase circulation to the horse’s feet.

Corticosteroids: These drugs reduce pain and inflammation, but only supply temporary relief and are not a cure-all! Some nonsteroidal anti-inflammatory drugs reduce blood clotting. These drugs only mask the problem, and don’t “fix” it.

Polysulfated Glycosaminoglycans: These drugs are known to help arthritic horses by protecting the joint cartilage from further deterioration. There is documented success on these drugs and is becoming an increasingly popular alternative for NS and arthritis.

Palmar Digital Neurectomy: This is a surgery where the palmar digital nerves are severed. This is done in such a way that the horse can still feel his toe. The results from this surgery will last for about 1 year, since the nerves will usually re-grow.

Desmotomy: This surgery involves cutting the suspensory navicular ligaments. It is usually done on horses with “club-foot”, to enable the deep digital flexor muscle to stretch.

Chemical Neurectomy: Involves injecting the palmar digital nerve with ammonium chloride or an alcohol extract, blocking pain. This was designed for the same reason Palmar digital neurectomy was: it blocks pain to the horse’s foot, allowing the horse to use his foot normally. This way, the mechanics of his foot can work correctly again.

Is Your Horse at High Risk?

Horses that have NS are mostly middle-aged. Fast-growing breeds with small feet (ex. Quarter Horse) are at a higher risk than breeds that grow slower and have larger feet in comparison to body size (ex. Ponies, Arabians and Draft breeds). Horses at high risk of NS are usually confined or stall-kept, have strong physical demands placed on them, or work over hard footing (pavement/gravel).

Is NS hereditary?

Some Researchers believe that NS may be hereditary. However, some disagree. It is advised not to breed horses with this condition. Many symptoms of NS are caused by poorly conformed hooves and weak pastern angles.

Work diligently with your veterinarian and farrier to help you make your horse as comfortable as possible. Your horse might not be a spectacular performance horse any more, but there are an abundance horses out there with NS that have created a world of happiness for many special people! Love your horse and care for him the best that you can – he depends on you.

About the author:

Cheryl’s goal is to educate horse owners on how to develop a trusting and respectful partnership with their horses. The training methods she uses and teaches are ones that promote a horse’s confidence and willingness to please.

As the President of Equusite.com (The Ultimate Horse Resource), Cheryl teaches her methods of horsemanship online in a simple step-by-step fashion to ensure that horsemen and women of all ages and disciplines are able to understand and use her methods easily.

For more information, see Cheryl’ bio page or contact her:

Cheryl McNamee-Sutor
President, Equusite.com
cheryl@equusite.com
(630) 267-9397

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