Technical information for veterinarians
What is osteochondrosis?
Osteochondrosis is a form of developmental orthopedic disease that involves a local or generalized failure of endochondral ossification affecting the epiphyseal and/or metaphyseal cartilage. Larger breeds of dog have a genetic predisposition towards the condition, which results from rapid growth. (The pain from osteochondrosis is similar to the “growing pains” experienced by adolescents.)
Areas most commonly affected by osteochondrosis include the shoulder, elbow, stifle and hock in young dogs. Osteochondrosis can occur bilaterally and may involve several joints. There are several types of osteochondrosis:
Conditions that affect the forelimbs include osteochondritis dessicans (OD) of the elbow or shoulder, fragmented coronoid process (FCP), and ununited anconeal process (UAP). When the elbows are affected, these conditions are often referred to as simply “elbow dysplasia.” Osteochondrosis affecting the hind limbs is less common.
Although osteochondrosis is not a type of arthritis, it frequently leads to degenerative joint disease.
Etiology of osteochondrosis
Endochondral ossification occurs in the bones of the extremities, the vertebral column, pelvis, and base of the skull. Bone is formed from a hyaline cartilage matrix, which becomes ossified. Several steps are involved in normal endochondral ossification. First, chondrocytes mature and enlarge. The intracellular matrix begins to thin and the mature chondrocyte produces alkaline phosphatase. This causes the intracellular matrix to calcify. Calcification of the matrix in turn causes the chondrocytes to die. Vascular penetration of the area then occurs and osteoblasts within the matrix produce bone, which matures to lamellar bone.
Osteochondrosis develops when cartilage cells that have proliferated in a normal manner, mature and differentiate abnormally. Failure of the cartilage matrix to calcify or failure of vascular penetration and osseous replacement causes the cartilage to thicken. Due to the lack of nutritional elements, necrosis develops in the deeper layers, giving rise to fissures. Eventually, a cartilagenous flap (OCD) develops.
Sometimes, the thickened cartilage persists without developing fissures and becomes surrounded by subchondral bone. Adjacent normal cartilage continues its endochondral ossification and the retained cartilage dies. This results in a subchondral cyst-like lesion.
Osteochondritis dissecans (OD)
occurs at the surface of a joint when a thickened area of cartilage develops, loosely attached to the underlying bone. This thicker cartilage may crack and cause a flap of cartilage to break away. When this cartilage flap falls into a certain position, the animal’s discomfort will be minimal but, as it shifts position, pain and joint swelling become acute. OD of the elbow and shoulder usually occurs between four and seven months of age. Breeds most commonly affected include the Labrador, golden retriever and (less frequently) the rottweiler.
Fragmented coronoid process (FCP)
of the elbow joint is the most common and severe type of osteochondrosis, affecting a dog’s forelimbs. FCP results from either a) abnormal development of the cartilage in the coronoid process, or b) abnormal length of the radius and ulna bones. Between four and six months of age, a small piece of the coronoid process may fragment inside the elbow leading to early onset secondary arthritis. (This usually develops between five and ten months of age.) Retrievers, Labradors, rottweilers and Bernese mountain dogs commonly experience FCP.
Ununited anconeal process (UAP)
is a failure of the growth center of the anconeal process to unite properly with the ulna. This fusion should be completed by 16 to 24 weeks of age. The ununited anconeal process is a large piece of bone connected to the ulna by a strand of fibrous tissue. It causes joint instability that may lead to severe secondary degenerative arthritis. UAP disease has been reported in most large breeds, particularly German shepherds and St. Bernards. UAP has also been reported in breeds with short, curved legs such as the basset hound. A dog may not exhibit signs of UAP until the secondary degenerative joint disease begins to develop.
OCD in the stifle joint
Osteochondrosis in the stifle can be difficult to diagnose, as the lameness is frequently obscure and is often confused with the gait of canine hip dysplasia (CHD).
OCD in the hock joint
Affected pets are usually four to five months of age and exhibit slight lameness of the hind limbs. The ankle joints appear straight and swollen and are painful on movement. X-rays show cartilage and bone fragments and bone spurs due to secondary degenerative joint disease.
Symptoms and diagnosis of osteochondrosis
The various forms of osteochondrosis (OCD) do not produce immediate, obvious symptoms. Signs that point to possible osteochondrosis (OCD) include:
- Lameness and pain in the affected joint.
- Restricted movement of the affected joint (e.g. paddling effect).
- Muscle wasting in the most affected side.
The symptoms of osteochondrosis (OCD) depend on where the problem is located. The dog may try to compensate for lameness by restricting the movement of the affected joint. For example, if the elbow is affected, he may swing his leg outward in a circular motion to avoid bending the elbow. Although the condition is usually bilateral, one leg is often worse than the other. As a result, the dog may take extra weight on the better foreleg (for example), resulting in decreased muscle development in the other foreleg.
Treatment options for osteochondrosis
The treatment for osteochondrosis is geared towards inhibiting further breakdown of the hip joint and decreasing pain. Various medical and surgical treatments are available today that can ease discomfort and restore mobility. The type of treatment depends upon several factors, such as the age of the patient, the severity of the problem and financial considerations. Management of the condition usually consists of exercise restriction, body weight management and symptomatic pain management with analgesics and anti-inflammatory drugs.
Restricting the amount and intensity of a puppy’s activity has been shown to reduce the incidence of osteochondrosis. Flaps of cartilage that have not yet broken away from their underlying bone may heal back if the affected joint use is not too intense or prolonged. All large breed puppies should participate in only regular short walks until they have finished growing; this recommendation is particularly important if the dog already has osteochondrosis. Dogs with osteochondrosis should be restricted to the leash and given a maximum of three short (10 -15 minute) walks per day.
Overfeeding contributes significantly to the development of many orthopedic conditions in dogs, including osteochondrosis. Vitamin or mineral supplements should be discontinued unless indicated and an appropriate feed recommended.
Analgesic and Anti-inflammatory medications – Ideally, these should only be used for the short term, when necessary to encourage movement. In most cases these medications act simply as painkillers, and are normally used in conjunction with lifestyle modifications including weight control and good exercise management.
Commonly used analgesics and anti-inflammatories include acetaminophen and various NSAIDs.
For mild to moderate osteochondrosis in dogs, acetaminophen (Tylenol®, Panadol®, Exdol®, etc.) will relieve pain. Since acetaminophen has no anti-inflammatory properties, it can generally be safely combined with anti-inflammatory medications.
Too-high doses of acetaminophen can cause liver damage. Acetaminophen is toxic to cats.
NSAIDs help reduce pain and swelling of the joints and decrease stiffness. When taken at a low dose, NSAIDs reduce pain; when taken at a higher dose, NSAIDs can also reduce inflammation. NSAIDs do not prevent joint damage and when used over the long-term, may accelerate joint breakdown. Taking more than one NSAID at a time increases the possibility of severe side effects such as ulcers and bleeding. (Special buffered ASA is available for dogs.) The newer sub-class of NSAIDs, known as Cox-2 Inhibitors, include Rimadyl® (carprofen), Metacam® (meloxicam) and Etogesic® (etodolac). Ibuprofen is toxic to dogs.
Caution: Vioxx®, a cox-2 inhibitor for use in humans, was just removed from the market place due to lethal side-effects related to heart attack, stroke, rhabdomyolysis and kidney failure due to the mechanism of action. This same mechanism of action is present in all cox-2 inhibitors and it would be wise to take this into consideration.
Cortisone is a corticosteroid that reduces inflammation and swelling. For severe pain and inflammation, cortisone is injected directly into the affected joint. This can provide almost immediate relief for a tender, swollen and inflamed joint.
Pentosan polysulphate (Cartrophen Vet®) is an injectable drug is given by injection at weekly intervals, usually on four separate occasions. Painkillers are not indicated while pentosan polysulphate is being administered.
Visco-supplementation is the process of injecting a gel-like substance into the joint. This substance lubricates the cartilage, reducing pain and improving flexibility. Visco-supplementation decreases friction within the joint, thus reducing pain and allowing greater mobility. This method of treatment requires ongoing injections as benefits are only temporary. Substances used in visco-supplementation include hyaluronic acid, or HA (Legend®, Hylartin® and Synacid®), and poly-sulfated glycosaminoglycans (PSGAGS) such as Adequan®.
Bioflavonoids (plant-based, antioxidant substances with the power to protect plant and animal tissues), have been shown in many scientific studies to help the tissues maintain their youthful structure. Antioxidants from green tea (Camellia sinensis) and grapes (Vitis vinifera) have been shown to have particularly beneficial effects and may be employed preventively or therapeutically to help repair damaged tissues. Nutricol® – available to veterinarians as Recovery®SA – is a proprietary formulation containing both these ingredients.*
Recovery®SA with Nutricol® is a proprietary natural health product developed to improve quality and rate of post-traumatic repair of damaged and inflamed tissue.* It may be used on its own or in combination with prescribed medications. See the Oct and Dec 2003 reviews of Recovery®EQ in the prestigious Horse Journal
If surgery is required for osteochondrosis
A number of surgical techniques are employed in the treatment of osteochondrosis. The goal of the surgical procedure is to remove any loose pieces of cartilage from the joint surface and curette the cartilage defect to encourage the body to refill the dessicated areas. Surgery should always be considered a last resort, when all other attempts to help the condition have failed.
Exercise should be limited for three to four weeks after surgery. Prior to therapy, the owner should be encouraged to limit the animal’s activity to reduce pain and minimize the chance of a fracture occurring.
Since many of pets with osteochondrosis have experienced rapid growth, some veterinarians feel that feeding lower protein diets without supplements may be helpful in decreasing the incidence of the disease.
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