 | This article includes a list of general references, but it lacks sufficient corresponding inline citations .(December 2008) |
Bone spavin is a bony growth within the lower hock joint of horses or cattle. It is caused by osteoarthritis, and the degree of lameness that results can be serious enough to end a horse's competitive career.
Bone spavin is osteoarthritis, or the final phase of degenerative joint disease (DJD), in the lower three hock joints. It usually affects the two lowest joints of the hock (the tarsometatarsal and the distal intertarsal joints), with the third joint, the proximal intertarsal, being the least likely to develop bone spavin. This condition has various types: jack spavin when there is significant bony enlargement over the tarsal bones, and high spavin when the pathology occurs higher in the joint than is typical. Conversely, occult spavin does not produce any significant exostoses on the small tarsals, whilst bog spavin and blood spavin do not involve bony changes.
Excessive compression can cause, over time, the cartilage between the upper and lower surfaces of the lower tarsal bones to become compressed and eroded. The joint spaces then become smaller, and new bone growth may occur in the area.
Uneven loading causes excessive compression of the cartilage and bone on one side, and strain in the joint capsule and supporting ligaments on the other side. When the joint is repeatedly overloaded on the edge of its surface, exostoses, or "bone spurs," occur. Strain of the supporting ligaments can cause exostosis around the joint as well.
There are several conformational defects that contribute to bone spavin. Those that cause uneven loading of the hocks, such as sickle hocks and cow hocks, are especially noteworthy. Poor trimming or shoeing can also contribute to bone spavin in any horse, no matter what their conformation.
Certain types of activities may also contribute to uneven or repeated loading of the lower hock joints, and thus bone spavin. These include sports that require a great deal of hock flexion (dressage), stress (jumping), sudden stops or turns (western events, such as reining), or a great deal of concussion (Standardbred racing).
"Juvenile spavin" is the occurrence of bone spavin in horses less than 3 years old. It usually occurs before the animal has done much work. While osteochondrosis lesions are the likely cause in some cases, this condition can also occur secondary to the distortion of the cuboidal bones which can occur in premature or dysmature foals.
Initially, signs of bone spavin may include sporadic and vague hindlimb lameness. Some horses may become uncomfortable in one lead, or may demonstrate stiffness walking downhill.
In many cases lameness worsens, becoming more obvious and consistent. Advanced cases may have a bony swelling on the hock, typically on the inside of the joint. Lameness, although usually worse in one leg, is commonly bilateral.
The affected limb usually lands toe-first, wearing down that foot faster than the other. The affected limb usually has a shorter, lower arc than the other foot, as the horse is trying to reduce the painful flexion of the joint, so the leg appears to drag.
A flexion test of an affected limb often produces a temporary worsening of the lameness. Such a response to a flexion test would support the diagnosis of bone spavin. A flexion test involves holding the hock in forced flexion for a period of time before trotting the horse away immediately.
A provisional diagnosis of bone spavin should usually be supported by further investigation in order to confirm the diagnosis.
Typical radiographic changes include spurs, new bone, bone destruction and/or joint narrowing or loss.
Anaesthesia of an affected joint is a more definitive way of confirming the presence of pain arising from that joint. Introduction of local anaesthetic into a joint should abolish or at least significantly lessen the lameness. This technique is not absolutely specific, as the distal pouches of the tarsometatarsal joint are immediately adjacent to the suspensory ligament. This means that anaesthetic in the tarsometatarsal joint can occasionally desensitize pain arising from suspensory ligament, giving the false impression that joint pain had been the cause of the lameness.
Scintigraphy (bone scan) can help to differentiate between suspensory origin desmitis and bone spavin.
Bony changes of the lower hock joint are irreversible. It is possible, however, to manage the problem and thereby slow the progression of the bone spavin, ease the pain, and control the lameness. Surgery is an option for horses that do not respond to conventional treatments.
NSAIDs, or non-steroidal anti-inflammatory drugs, may help improve the lameness in the horse. However, it is important to note that high doses of NSAIDs given over several days can cause kidney damage, as well as ulcers and right dorsal colitis. NSAIDs may also be illegal in competition, so it may be necessary to stop treatment with NSAIDs several days before the horse competes.
Corticosteroid injections into the lower hock joints may resolve the lameness of the horse for several weeks or months. Again, it is important to check association rules to see if corticosteroids are not allowed in competition, so that they may be discontinued before the horse competes.
Orthobiologics such as PRP, autologous conditioned serum, or autologous protein solution often have similar effects but without the side effects of corticosteroids.
Tiludronic acid, a bisphosphonate, tradenames Tildren and Equidronate (UK) has been beneficial in the treatment of some cases of bone spavin. It is administered by slow infusion (30 mn) mixed with saline.
Other joint medications, like hyaluronic acid and Adequan, may help alleviate the pain if the horse has mild bone spavin. However, they are less useful for treating moderate of severe cases.
Nutritional supplements containing MSM, glucosamine, and other ingredients may also help horses with moderate bone spavin.
Proper shoeing is critical in the management of a horse with bone spavin. Shoes most helpful for these horses include shoes that assist in breakover (like a square or rolled toe, or shoes with wedge pads). Shoes with heel support may also help horses with bone spavin, such as egg bar shoes. A set toe can be applied to protect the toe from increased wear, as lack of flexion in the hock will cause the horse to drag its toe. A trailer or lateral extension can be fitted to prevent an axial swing developed by the horse, allowing the horse to make contact with the ground earlier and prevent rotation within the hock. Each case of bone spavin should be shod independently depending on the severity of the case and the horses needs, there is not a specific shoe to be applied.
It is best for a horse with bone spavin to be exercised daily. Preferably, this should be ridden or driven work, as round pen or longeing exercise places uneven stress on the joint. Pasture turnout may not be beneficial if the horse does not move much.
It is best to decrease the intensity of the workload for a horse with bone spavin. However, even with careful management, bone spavin will progressively get worse, and the animal may not be able to continue at the level of competition it was first used for once the lameness is consistent. Many horses can still be successful in a less-strenuous career. Light exercise is better than no exercise at all, and a change of career may prolong the horse's useful life.
Fusion of the affected joint may end the lameness, as the joint has then become stable. However, this may take several years, or never occur. In these cases, surgery may be an option.
In a facilitated ankylosis procedure, some of the joint cartilage is destroyed with a drill bit or a laser, and the holes are sometimes filled with bone grafts.
Alternatively, the veterinarian may also inject a caustic agent into the joint to destroy the cartilage, as opposed to drilling the joint. After the procedure, the horse will be lame for weeks or months, until the joint has fused.
Exercise can help accelerate the fusion of the bones, so the horse may be hand-walked after the injection. NSAIDs are usually given to ease the pain.
A cunean tenectomy can be performed with good success in some cases. The cunean tendon runs diagonally across the inside of the joint. When there is excessive bone here, it is thought that this can cause irritation on the tendon and its associated bursa. In this procedure, a section of the tendon is removed,
The prognosis for bone spavin varies, depending on several factors including:
Most horses cannot continue at a high level of competition for long. However, many horses can continue happily for use as a trail or pleasure horse, or for light work.
The foot is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made up of one or more segments or bones, generally including claws and/or nails.
The hock, tarsus or uncommonly gambrel, is the region formed by the tarsal bones connecting the tibia and metatarsus of a digitigrade or unguligrade quadrupedal mammal, such as a horse, cat, or dog. This joint may include articulations between tarsal bones and the fibula in some species, while in others the fibula has been greatly reduced and is only found as a vestigial remnant fused to the distal portion of the tibia. It is the anatomical homologue of the ankle of the human foot. While homologous joints occur in other tetrapods, the term is generally restricted to mammals, particularly long-legged domesticated species.
Laminitis is a inflammation of laminae that affects the feet of ungulates and is found mostly in horses and cattle. Clinical signs include foot tenderness progressing to inability to walk, increased digital pulses, and increased temperature in the hooves. There is also swelling in foot in some cases.Severe cases with outwardly visible clinical signs are known by the colloquial term founder, and progression of the disease will lead to perforation of the coffin bone through the sole of the hoof or being unable to stand up, requiring euthanasia.
Navicular syndrome, often called navicular disease, is a syndrome of lameness problems in horses. It most commonly describes an inflammation or degeneration of the navicular bone and its surrounding tissues, usually on the front feet. It can lead to significant and even disabling lameness.
Bog spavin is a swelling of the tibiotarsal joint of the horse's hock which, in itself, does not cause lameness. The joint becomes distended by excess synovial fluid and/or thickened synovial tissue bringing about a soft, fluctuant swelling on the front of the joint, as well as in the medial and lateral plantar pouches. Bog spavin is generally an indication of underlying pathology within the joint.
Tendinitis/tendonitis is inflammation of a tendon, often involving torn collagen fibers. A bowed tendon is a horseman's term for a tendon after a horse has sustained an injury that causes swelling in one or more tendons creating a "bowed" appearance.
Equine conformation evaluates a horse's bone structure, musculature, and its body proportions in relation to each other. Undesirable conformation can limit the ability to perform a specific task. Although there are several faults with universal disadvantages, a horse's conformation is usually judged according to its intended use. Thus "form to function" is one of the first set of traits considered in judging conformation. A horse with poor form for a show jumper could have excellent conformation for a cutting horse or draft horse. Every horse has good and bad points of conformation and many horses excel even with conformation faults.
Ringbone is exostosis in the pastern or coffin joint of a horse. In severe cases, the growth can encircle the bones, giving ringbone its name. It has been suggested by some authors that such a colloquial term, whilst commonly used, might be misleading and that it would be better to refer to this condition as osteoarthritis of the inter-phalangeal joints in ungulates.
Splints is an ailment of the horse or pony, characterized by a hard, bony swelling, usually on the inside of a front leg, lying between the splint and cannon bone or on the splint bone itself. It may be "hot," meaning that it occurred recently and is still painful; or "cold," meaning that the splint has completely recovered and there is no longer any pain associated with it. Bucked shins are sometimes called 'shin splints,' which involve small stress fractures of the dorsal cannon bone, often seen in race training, and discussed elsewhere.
A Lisfranc injury, also known as Lisfranc fracture, is an injury of the foot in which one or more of the metatarsal bones are displaced from the tarsus.
The flexor digitorum longus muscle or flexor digitorum communis longus is situated on the tibial side of the leg. At its origin it is thin and pointed, but it gradually increases in size as it descends. It serves to flex the second, third, fourth, and fifth toes.
Sesamoiditis is inflammation of the sesamoid bones.
Osselet is arthritis in the fetlock joint of a horse, caused by trauma. Osselets usually occur in the front legs of the horse, because there is more strain and concussion on the fetlock there than in the hind legs. The arthritis will occur at the joint between the cannon bone and large pastern bone, at the front of the fetlock.
A sickle-hocked leg structure is one in which the back leg joints of an animal, usually a horse or other equine mammal, are set with too much angle, resulting in the hock also being excessively angled. This can result in uneven hoof wear, which is incredibly painful for the affected horse. If the leg joints are not set properly, there is a high chance that the back joints are also set incorrectly, resulting in a poorly conformed horse.
A flexion test is a preliminary veterinary procedure performed on a horse, generally during a prepurchase or a lameness exam. The purpose is to accentuate any pain that may be associated with a joint or soft-tissue structure, allowing the practitioner to localize a lameness to a specific area, or to alert a practitioner to the presence of sub-clinical disease that may be present during a pre-purchase exam.
The skeletal system of the horse has three major functions in the body. It protects vital organs, provides framework, and supports soft parts of the body. Horses typically have 205 bones. The pelvic limb typically contains 19 bones, while the thoracic limb contains 20 bones.
Lameness is an abnormal gait or stance of an animal that is the result of dysfunction of the locomotor system. In the horse, it is most commonly caused by pain, but can be due to neurologic or mechanical dysfunction. Lameness is a common veterinary problem in racehorses, sport horses, and pleasure horses. It is one of the most costly health problems for the equine industry, both monetarily for the cost of diagnosis and treatment, and for the cost of time off resulting in loss-of-use.
Tarsal coalition is an abnormal connecting bridge of tissue between two normally-separate tarsal (foot) bones, and is considered a sort of birth defect. The term 'coalition' means a coming together of two or more entities to merge into one mass. The tissue connecting the bones, often referred to as a "bar", may be composed of fibrous or osseous tissue. The two most common types of tarsal coalitions are calcaneo-navicular and talo-calcaneal, comprising 90% of all tarsal coalitions. There are other bone coalition combinations possible, but they are very rare. Symptoms tend to occur in the same location, regardless of the location of coalition: on the lateral foot, just anterior and below the lateral malleolus. This area is called the sinus tarsi.
The limbs of the horse are structures made of dozens of bones, joints, muscles, tendons, and ligaments that support the weight of the equine body. They include two apparatuses: the suspensory apparatus, which carries much of the weight, prevents overextension of the joint and absorbs shock, and the stay apparatus, which locks major joints in the limbs, allowing horses to remain standing while relaxed or asleep. The limbs play a major part in the movement of the horse, with the legs performing the functions of absorbing impact, bearing weight, and providing thrust. In general, the majority of the weight is borne by the front legs, while the rear legs provide propulsion. The hooves are also important structures, providing support, traction and shock absorption, and containing structures that provide blood flow through the lower leg. As the horse developed as a cursorial animal, with a primary defense mechanism of running over hard ground, its legs evolved to the long, sturdy, light-weight, one-toed form seen today.
The treatment of equine lameness is a complex subject. Lameness in horses has a variety of causes, and treatment must be tailored to the type and degree of injury, as well as the financial capabilities of the owner. Treatment may be applied locally, systemically, or intralesionally, and the strategy for treatment may change as healing progresses. The end goal is to reduce the pain and inflammation associated with injury, to encourage the injured tissue to heal with normal structure and function, and to ultimately return the horse to the highest level of performance possible following recovery.
King, Christine; Mansmann, Richard (1997). Equine Lameness. Grand Prairie, TX: Equine Research. pp. 839–847. ISBN 0935842128.