If you've been nearby horses for any distance of time, you probably know of some unlucky equine who has been diagnosed with navicular disease (or navicular syndrome). Navicular is the most coarse source of performance-limiting lameness in the front legs of horses today. Sadly, the actual cause of this lameness is poorly understood, probably because it's difficult to pinpoint the true cause of foot pain.
Disease or Syndrome?
Artisan Riding
Over the past decade, I've seen veterinarians diagnosing fewer and fewer cases of true navicular disease. Instead many elect to naturally classify any horse with navicular region pain as a navicular syndrome horse.
So what is the dissimilarity between a disease and a syndrome? The truth is, not very much. Disease is defined as a pathological condition of a part, organ, or law of an organism resulting from various causes, such as infection, genetic defect, or environmental stress, and characterized by an identifiable group of signs or symptoms.
A syndrome is more generally defined as a group of symptoms that collectively indicate or reveal a disease, psychological disorder, or other abnormal condition.
By using the term syndrome, a veterinarian may feel he has left his options somewhat open. He doesn't have to deal with the stigma that surrounds a determination of true navicular disease, where the determination is seen as very poor. The term "disease" implies a known cause and a definite treatment but by calling it a syndrome, determination is left to the discretion of the attending veterinarian.
The approved View
Conventional veterinary treatment views navicular disease as lasting forelimb lameness connected with pain originating from the distal sesamoid (navicular bone) and its closely connected structures, along with the distal impar ligament, collateral ligaments of the navicular bone, the navicular bursa, and the deep digital flexor tendon. These communal structures are sometimes referred to as the navicular apparatus. Navicular disease is carefully degenerative in nature, resulting in progressively worsening lameness.
Conventional veterinary treatment defines navicular disease as a particular disease. Given the variety of symptoms that manifest in lameness of the fore foot, however, it is likely that any distinct conditions, with distinct origins, are responsible for pain connected with the navicular region. Mri evidence confirms that many other problems in horses cause the same clinical signs as those in horses diagnosed with navicular disease. This has lead some researchers to quiz, the term "navicular disease", feeling that it no longer applies to many of the horses being evaluated for foot lameness problems.
Clearing Up the Confusion
Researchers have been unable to reproduce navicular disease in experiments, so they can only suspect about what causes it. In fact, today's veterinarian can subscribe to any theories on how the condition occurs and this will determine how he decides to treat it.
One law suggests vascular problems as the cause of navicular disease. Researchers reportedly observed thrombosis (clotting) and arteriosclerosis (thickening arterial walls), important to ischemia (insufficient blood supply) within the navicular bone in horses diagnosed with navicular disease. This theory, however, has been largely rejected because of a failure to reproduce clinical signs or pathological changes when researchers sell out blood supply to the navicular bone of horses in clinical studies.
A second theory, which focuses on postmortem studies of horses with long-term lasting lameness and radiograph abnormalities, suggests that biomechanical factors may promote this degenerative disease. Proponents of biomechanics as a cause define navicular disease as pathological changes of the soft tissue of the navicular apparatus -- the navicular bursa, and the articular cartilage of the joint. They suggest that the pathological changes are the effect of inflammation caused by vibration and friction.
In other words, this law suggests that environmental influences can effect in stress on the navicular area during movement. Horses that work over hard surfaces, for example, touch excessive vibrations that effect in changes to the mechanics of joint movement. This leads to greatest compression of the navicular bone by the deep digital flexor tendon. Toe first landing and foot imbalance are other examples of negative influences that can adversely influence the biomechanics of joint movement.
The Holistic View
In my not so approved practice of Applied Equine Podiatry, we seldom use the term "navicular disease". Taking a more holistic approach, we embrace any principles, theorems, and philosophies. At its foundation is the confidence that structure plus function equals doing (S+F=P). We also know that a horse has an innate ability to heal himself, provided the environment is conducive to healing.
What does this mean to the treatment of the condition defined as navicular disease? First, we have to understand that in advent to a point where a particular disease is defined, as is often the case in approved veterinary medicine, we have narrowed our focus, and become reactive. As new investigate provides evidence that there are complicated causes for the clinical manifestations of the lameness connected with navicular disease, it is only logical that a series of events have led to the condition observed.
As theorized, changes in general biomechanics of joint movement may lead to inflammation of the soft tissues of the navicular apparatus, but the quiz, is: what is general biomechanics of joint movement of the navicular apparatus?
To write back this question, you must subscribe to a definite model of foot function. We subscribe to a model that defines the Internal Arch Apparatus.
Understanding the Internal Arch Apparatus
The Internal Arch Apparatus is responsible for both energy utilization and energy dissipation within the foot, and is comprised of the coffin bone, navicular bone, distal articulating exterior of the short pastern, all connective tissues (ligaments, tendons, fascia), the digital cushion, and all corium (inner layer of foot, containing nerves and blood vessels). In short, the Internal Arch Apparatus constitutes all structures of the foot, without the hoof capsule. Applied Equine Podiatry recognizes that true foot function sees all structures working in concert to supply performance. Because this model includes the navicular apparatus as part of the whole, a manifestation of pain within the navicular apparatus would indicate a loss of structure and/or function of the Internal Arch Apparatus.
Taking things a step further, it is understood that the coria (corium) of the Internal Arch Apparatus yield the hoof capsule. It is often said of the foot that the exterior is a mirror image of the inside. If one subscribes to this belief, it is only natural that one would become reactive, being held slave to the foot's internal conformation. I teach and effect the premise that "everything on the inside is a mirror image of that on the outside." Is this semantics? Hardly -- with an understanding that the internal structure's condition is the effect of external stimulus, we become empowered.
Where am I going with this? I am saying that true navicular disease (lameness due to bone change) is only apparent following a long series of recurring events. In this chain of events, soft tissue is the first to feel convert in response to an environmental alteration (balance change, increased vibration, disagreement and/or pressure), followed by changes to the horn. Before any modifications to the bone become apparent, the hoof capsule will show deformity (flare, excessive wear or growth). As the horse reacts to pain, he changes the way he loads the foot, and deformity appears. The deformity can be minimal, but it will occur.
On rare occasions, a horse may show an acute-onset unilateral (affecting one limb) lameness, which leads to a determination of navicular disease. It is my confidence that short of a catastrophic insult (injury), pronounced unilateral lameness is more often the effect of lasting loss of structure (fallen arch) and permissible foot function.
How is it Treated?
Conventionally, either the determination is disease or syndrome, most veterinarians will suggest corrective shoeing. Most commonly, this means an egg-bar shoe (said to give added preserve to the heel), accompanied by a rolled or rocker toe, wedge pads when needed to precise hoof pastern angle, and impression material for cushioning. But other shoeing protocols are used too. Conventionally speaking, corrective shoeing, regardless of the shoe used, is dependent on the horse's hoof-pastern angle. If the horse already had a well-conformed foot, little will be achieved with corrective shoeing in the industrialized stages of the disease.
In addition, vets may suggest non-steroidal anti-inflammatory medications to control foot pain, as well as phenylbutazone (bute), but not all horses with navicular pain write back to phenylbutazone. Medications to increase blood supply have also been prescribed. As a last resort, your vet may accomplish a surgical course known as a neurectomy. This course severs the nerve supplying the back of the foot, but the results are often temporary.
How Does Applied Equine Podiatry Differ?
When presented with a horse diagnosed with navicular disease, it is imperative to value the foot structure. As I do not subscribe to the approved definition of a well-conformed foot, I correlate the foot with an eye on the condition of the Internal Arch Apparatus. I have found that navicular pain results from a loss of those structures that help in maintaining permissible biomechanical function of the joint, and in the positioning of the coffin bone in its relation to the joint and the distal limb. These structures comprise not only the distal sesamoidean ligaments and tendons, but also the lateral cartilage and digital cushion.
Where approved reasoning focuses on the stress exerted by the deep digital flexor tendon on the navicular bursa, and reacts to sell out this stress by reducing break-over or expanding foot angle, I find myself more involved with heel placement and the effect it has on the biomechanics of joint movement, circulation, and neurological function. Where are the heels in connection to the center axis of the joint? No shoe can alter the position of heels in connection to this center axis, but it does alter the military acting on the joint. This may temporarily sell out pain, but it's seldom prosperous in stopping the progression of the disease.
This approved arrival ignores the importance of the Internal Arch Apparatus and the role it plays in energy utilization. The key to treating navicular pain is to reconsider the whole. naturally trimming the heels to get them to the widest part of the frog, or reducing break-over, does not address the underlying cause of the pain -- the loss of structure causing undue stress on the supporting structures of the joint.
Instead we supply the precise stimulus that will finally effect in reducing the stresses connected with the progression of the disease process, and help restore sound structure and permissible function. I have found that pain management is important during this time, and that pain can effectively be managed homeopathically and by the use of concluded cell foam pads as a rehabilitative strategy.
Over the past eight years, I have worked on many horses diagnosed with navicular syndrome/disease, and most had weak structure to the caudal (back) aspect of the foot. But with precise trimming to accomplish balance of the hoof capsule to that of the Internal Arch Apparatus, the suitable application of stimulus (exercise/pressure) to aid in the return of precise structure, and sound pain management practices, I was able to eliminate the condition.
For more information on Applied Equine Podiatry, please visit http://www.appliedequinepodiatry.org
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How to Know if Your Horse has Navicular
Most people effect a more conventional, reactive way of thinking, so they consult with their veterinarian only after a steady loss of doing from their horse. The horse may have exhibited a shortened stride, with forelimb stiffness, intermittent shifting of weight from one forelimb to the other, or pointing of intermittent limbs. The observant horse owner may even recall that the horse had previously warmed out of its lameness, but the warm-up took progressively longer, until the horse no longer worked out of the lameness. In industrialized cases, it may have been observed that the horse had packed mounds of bedding beneath his heels, or that he rested his hindquarters on a manger or fence rail.
If you effect Applied Equine Podiatry or a similar proactive approach, you'll understand that even a little loss of doing over a short period, coupled with the occurrence of mild hoof deformity (flare, imbalance, increased asymmetry), could lead to pain within the Internal Arch Apparatus, and a determination of navicular syndrome/disease.
Learning about permissible foot structure will help you become proactive. witness your horse when he is sound; watch him move under saddle both in a level line and circling. Make a reasoning picture of your horse's movements. Have x-rays taken when your horse is sound, and know what a good foot should look like.
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