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Dog Legs And Paws, Neck And Back

Disk Disease

The spinal column is made up of a number of small bones called vertebrae that are lined up like building blocks. A hole in the center of each vertebra forms a tunnel in which the spinal cord lies. The spinal cord is extremely important because it carries the messages from the brain to the rest of the body. It is also extremely delicate, and the bony vertebrae help to protect it. Between each vertebrae, just underneath the spinal cord, is a little cushion, called an intervertebral disk, which cushions the vertebrae from one another and provides flexibility to the spine during movement. As a part of the normal aging process, these disks deteriorate, resulting in disk disease. Normally, each disk consists of an outer fibrous ring and an inner gelatinous center. (A good analogy would be a jelly donut). With age this “doughnut” changes in consistency; the outer fibrous ring becomes fragmented and the inner “jelly” center hardens to a consistency of hard cheese. The fragmented outer fibrous ring may no longer be able to hold this hard center in place, and movement of the vertebrae on either side may suddenly squeeze the disk out of its normal position. Unfortunately,

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Cauda Equina Syndrome

Anatomy The spine consists of 27 bones, not including those in the tail. Disks are located between the bones of the spine and serve as shock absorbers. Each disk consists of an outer fibrous ring (annulus fibrosus) that surrounds inner pocket of gelatinous material (nucleus pulposus). Ligaments and many muscles support each of the bones of the spine. The spinal cord runs through a large canal within the spinal bones, thereby protecting it from injury. Each disk is located beneath the spinal cord, where each of the spinal nerves exits the spine. The spinal cord terminates at approximately the sixth lumbar vertebral bone (lower back). Nerves to the hind limbs, bladder, rectum and tail extend off the terminal part of the spinal cord and exit the spine to their respective areas. The area where all of the nerves come off the terminal spinal cord looks like a horse’s tail, hence it is called the cauda equina. Causes of cauda equina syndrome Cauda equina syndrome is a condition in which the nerves of the hind limbs and rear end are compressed. Disease processes that can compress the sciatic and sacral nerves include degenerative arthritis of the spine; congenital deformity of the

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Cranial Cruciate Ligament (CrCL) Tears

The canine knee joint, known as the stifle joint, is similar to a human’s knee. The joint is made up of the femur (thigh bone), tibia (shin bone), and the patella (kneecap) that are firmly held together by ligaments. Ligaments are strong, dense structures consisting of connective tissues that connect the ends of two bones across a joint. The function of ligaments is to stabilize the joint. The stifle has two very important ligaments called the cranial (CrCL) and caudal (CaCL) cruciate ligaments (cruciate means a cross or crucifix) that cross in the center of the joint. The CrCL (known as the ACL in humans) restrains the backward and forward motion of the joint, in addition to inward twisting and hyperextension of the joint. It is the structure that is most commonly injured in dogs. In fact, more than 600,000 dogs in the U.S. have surgery for this problem every year. The stifle also has two half-moon shaped cartilage structures between the weight-bearing bone ends called menisci. There are two menisci in each stifle, one on the inner side of the joint called the medial meniscus and one on the outer side of the joint called the lateral meniscus. The

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Patella Luxation (Dislocating Kneecap)

What is a luxating patella? A luxating, or dislocating, kneecap is a condition in which bony abnormalities result in distortion of the knee joint so that the forces applied to the kneecap cause it to hop out of a groove (trochlea) located at the bottom of the thigh bone. The abnormalities of the knee that allow the kneecap to dislocate include a too-shallow trochlear groove; a twisted shin bone resulting in a misaligned tibial crest; torn (or stretched) soft tissues that normally hold the kneecap in place; and in some cases significant bowing or twisting of the bottom of the femur bone. Dislocation of the kneecap also causes the shin bone to turn inward, which may cause the cranial cruciate ligament (CrCL) to tear. In fact, about 20 to 25% of the dogs that have a patellar luxation sustain an injury to this main-stabilizing ligament of the knee. Clinical signs of a dislocating kneecap include lameness, intermittent skipping gait, intermittent crying out or unwillingness to jump on elevated surfaces. Diagnosis The diagnosis is made on physical examination, in which the surgeon can feel the kneecap dislocate out of place. In some cases, X-rays of the knee and thigh bone will

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Hip Dysplasia

What is hip dysplasia? The hip joint attaches the hind limb to the body. This joint is a ball and socket that is held together by muscles, joint capsule and a ligament. The inside of the joint is covered with glistening cartilage that allows the joint to move smoothly. The joint fits tightly and remains in the socket during rest and play. Hip dysplasia is a condition in puppies that begins with looseness of the supporting muscles, ligament and joint capsule of the hip. As the ball separates from the socket, the joint gradually becomes deformed and no longer fits well together. With time, arthritis of the hip develops. Although defective genes cause hip dysplasia, limited food consumption frequently will slow the growth of affected puppies and prevent the development of this condition. Signs Dogs are commonly five to eight months of age when signs first appear. Any breed can develop this condition; however, large breeds are most commonly affected. Some dogs, however, are quite geriatric when the problem is found. Warning signs of hip dysplasia may include an awkward gait that is frequently dismissed as “a clumsy puppy.” Waddling of the hind quarters when walking; bunny hopping; stiffness when

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Hypertrophic Osteodystrophy

Anatomy The ends of bones of growing puppies have a zone called the growth plate. The bone adjacent to the growth plate is soft and very developmentally active. Cause The cause of hypertrophic osteodystrophy in dogs is largely unknown. Proposed causes include distemper virus infection, vaccination with distemper virus, bacterial infection and other viral infections. Vitamin C deficiency is unlikely to be a cause of this disease, as previously believed. With HOD, a series of events take place at the microscopic level within the affected bones. First, the blood vessels near the growth plate become distended and bleed into the bone. Next, the bone in this region dies, gets resorbed and develops microfracturing due to weakening of the bone structure (arrow in photo). In response to this, new bone is laid on the surface of the bone (star in photo). Signs and diagnosis Clinical signs of HOD include fever, anorexia and depression. Lameness is always seen with this disease and may vary from mild to severe. With multiple limbs affected, the patient may be reluctant to stand or walk. Typically, the ends of the long bones become thickened. The radius, ulna and tibia are most commonly affected; however, the ribs,

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Iliopsoas Muscle Tears

Anatomy The iliopsoas muscle consists of the fusion of the iliacus and psoas major muscles. The psoas muscle attaches along the under side of the backbones, and the iliacus attaches on the inner side of the pelvis. These two muscles join together and form a common tendon that attaches onto the lesser trochanter of the thigh bone (femur). The function of this muscle is to externally rotate and flex the hip joint. Animals can function without this muscle. Iliopsoas strain (tear) results from excessive stretching of this muscle during highly athletic activities such as agility training or fetching a tennis ball. The injury occurs commonly at or near the muscle-tendon junction, the weak link. Slipping into a splay-legged position, jumping off an elevated surface, excessive training or play, and roughhousing with other pets are common causes of the muscle strain. Clinical signs and diagnosis Iliopsoas muscle tears are a relatively common yet infrequently diagnosed injury in dogs. Tearing of this muscle is very painful and causes pain and lameness. Commonly, exercise exacerbates the lameness with this condition. Pain is noted when stretching the affected muscle, either by putting the hip in extension with abduction or by putting the hip in

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Legg-Calve-Perthes Disease

This disease of young small breed dogs results in destruction of the head (ball) of the femur bone. The underlying cause of this condition is likely genetic. The condition typically affects only one hip, but 17% of dogs have both hips affected. This disease is due to a disturbance of the blood supply within the femoral head that subsequently results in death and resorption of the bone. The femoral head collapses which results in hip pain. Signs LCP affects small breeds of dogs with the Yorkshire terrier most commonly affected. Warning signs of LCP that are most commonly seen by pet owners may include hind limb lameness, muscle atrophy, stiffness on the affected limb when first getting up from a nap, exercise intolerance, and pain upon petting the hip. The lameness initially is mild but with time becomes severe. Examination by a veterinarian typically reveals pain on extending or spreading the affected hip(s) apart. Diagnosis The diagnosis of LCP is based on the evaluation of X-ray images of the pelvis. In order to obtain properly positioned X-rays, your dog may need to receive sedation. Typical signs on the X-rays include a moth-eating appearance of the femoral head, a misshapen femoral

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Long Digital Extensor Tendon Avulsion

Anatomy The long digital extensor tendon attaches onto the bottom of the thigh bone (femur), runs through the knee joint and then forms a muscle located along the side of the shin bone (tibia). Cause of long digital tendon avulsion Generally this type of condition occurs in very young large breed dogs. At this early age the bones are very soft; thus the long digital extensor tendon can tear out of the bone with minimal trauma. The avulsed end of the tendon always has a small bone fragment that has broken out of the femur bone. Signs Breeds most commonly affected include great Danes, golden retrievers, and Labrador retrievers. Dogs develop this problem when they are typically under one year of age; however, two reports have cited great Danes that were 14 and 16 months of age. Clinical signs of this condition include lameness and swelling on the outer side of the knee over the region of the avulsed tendon. Diagnosis X-rays and physical examination findings support the diagnosis of a long digital extensor avulsion. Uncommonly, CT scan or MRI of the knee is needed to arrive at a diagnosis. Exploratory surgery is the most definitive way to diagnose and

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Panosteitis

Anatomy Bones consist of two basic components: the cortex and the marrow. The cortex of a bone, which provides its structural support, is composed of calcium and other organic materials. The marrow contains a very rich blood supply, fat and the cells that produce blood. Because bones are highly innervated (rich nerve supply), many diseases of the bones are very painful. What is Panosteitis? The word panosteitis can be broken down into “pan,” which means “all” and “osteitis,” which means “inflammation of the bone.” Many synonymous names have been given to the condition; these include eosinophilic panosteitis, enostosis, endosteal proliferation of new bone, juvenile osteomyelitis, wandering lameness, growing pains, pano, and eopan. This condition typically affects the long bones of the limbs and is a painful disease in which the bone marrow becomes very dense. Upon microscopic examination of the affected bones, no inflammation is typically seen (which makes the name panosteitis a misnomer); however, the primary finding is the presence of scar tissue, which subsequently changes into bony tissue. New bone is also formed on the inner (endosteal reaction) and outer surfaces of the bone (periosteal reaction). The cause of panosteitis is largely unknown. Because the German shepherd breed

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Salivary Mucocele

Anatomy Dogs have many salivary glands located both within the lining of the mouth and in the head and neck region. The most important salivary glands include the zygomatic (located by the eye), mandibular (located just behind the jaw bone), sublingual (located under the tongue), and parotid salivary glands (located around the ear canal). Causes of salivary mucoceles The inciting cause of a salivary mucocele is usually not definitively identified; however, trauma from a choke chain, bites to the neck, and sudden hyperextension of the neck are suspected causes. These can cause stretching or tearing of the salivary gland or the duct that drains saliva from the gland to the mouth. Saliva accumulates under the skin and incites a marked inflammatory response. The body attempts to contain the leaking saliva by creating a layer of connective tissue around the saliva (called a mucocele). Signs and diagnosis Mucoceles are primarily found in dogs, but are rarely seen in cats. Mucoceles are more commonly seen in dachshunds, German shepherds, poodles, and silky terriers that are at any age. The clinical signs associated with a mucocele are dependent on the gland that is affected: Cervical mucocele is caused by damage to the mandibular

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Shoulder Osteochondritis Dissecans

Osteochondritis dissecans (OCD) affects young, large-breed dogs and causes forelimb lameness. It is a condition in which a region of the cartilage surface, usually the size of a dime, fails to undergo normal development. This region of cartilage becomes thicker than normal. Because nutrients penetrate cartilage by diffusion, the deep part of the abnormal cartilage does not get nourished, as it is too thick. Subsequently, some of the cartilage cells die off which results in weakening of the cartilage. This area of cartilage then separates from the underlying bone in the form of a cartilage flap. Sometimes the cartilage flap becomes detached from its bed and falls into a pouch of the joint (called the cul de sac of the shoulder). Occasionally a fragment of the OCD flap will migrate down the sheath of the biceps tendon (which communicates with the shoulder joint) and causes inflammation of the tendon’s sheath. Signs and diagnosis A diagnosis of OCD is based on findings of X-ray images, in addition to finding signs of pain upon flexion or extension of the shoulder joint. A side view X-ray of the shoulder usually reveals evidence of OCD (flattening of the humeral head). Treatment Traditional surgery used

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Superficial Digital Flexor Tendon Luxation

Anatomy The Achilles tendon is attached to the heel bone (calcaneous bone) of the hind limb and is responsible for keeping the heel bone elevated off the ground. The Achilles tendon is actually composed of five distinct tendons: the gastrocnemius (G), superficial digital extensor (SDF), and three other less significant tendons called the gracilis, semitendinosus, and the biceps femoris tendons (B). The gastrocnemius tendon is quite large and attaches onto the calcaneous bone. The superficial digital flexor widens over the calcaneous bone to form a cap that is attached to the bone on each side by fibrous tissue (called a retinaculum). As this tendon passes down the backside of the paw it splits into four separate tendons that attach onto each of the four toes (digits) of the hind limb. Cause of tendon dislocations If the retinaculum that keeps the superficial digital flexor tendon in place gets torn due to a traumatic injury, the tendon will pop off to the side of the calcaneous bone and cause lameness. In shetland sheepdogs and collies, the end of the calcaneous bone may be malformed, which predisposes the tendon to dislocate. Signs and diagnosis Most dogs that have this kind of injury are

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Infraspinatus Tendon Contracture

Anatomy The shoulder is supported by a set of tendons and ligaments. Tendons attach a muscle to the bone, whereas a ligament attaches one bone to another. The infraspinatus muscle is responsible for external rotation and extension of the shoulder joint. Injury to the infraspinatus muscle usually takes place during hunting or other athletic activities. Initially, this will cause lameness, but subsequently as the muscle heals with scar tissue the muscle becomes very tight (contracture) and the limb becomes externally rotated. Signs and diagnosis The most common sign of an infraspinatus muscle contracture is external rotation of the limb. When walking or trotting a swinging or circumducting movement of the affected limb is seen. On physical examination, the limb cannot be internally rotated at the shoulder due to the frozen muscle. X-rays of the shoulder may be recommended to rule out other problems of the shoulder. Blood testing is performed prior to surgery to ensure a safe anesthesia. Treatment An incision is made over the side of the affected shoulder. The tendon of the contracted infraspinatus muscle is isolated and a section of the tendon is removed to free up the movement of the shoulder. Results Dogs that receive surgery

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Supraspinatus Tendinopathy

Anatomy The shoulder is supported by numerous tendons and ligaments. Tendons attach a muscle to the bone; whereas a ligament attaches one bone to another bone. The supraspinatus muscle is responsible for extension of the shoulder joint. Its tendon attaches onto the front part of the humerus bone of the forelimb. Cause of supraspinatus tendinopathy Tendonopathy means “disease of a tendon.” Injury to the supraspinatus tendon usually occurs during hunting or other athletic activities. Extreme and rapid hyperflexion of the shoulder is likely the cause of tear or damage to the supraspinatus tendon. The body’s response to the injury is to lay down calcium deposits within the injured tendon. The calcified material is irritating to the dog and can cause pain and lameness. In some dogs, the calcified tendon does not cause any pain; yet in other dogs it does. Signs and diagnosis The most common sign of a supraspinatus tendinopathy is lameness on the affected limb. Sometimes the lameness is subtle, and the owner may only note that the dog is not as powerful on that limb when swimming; thus the dog tends to turn toward the affected limb. Physical examination generally is fairly unremarkable; however, some patients may

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Wobbler Syndrome

Anatomy The spine of the dog extends from the base of the skull and includes the neck, back, and the tail. The spine is made of many interlocking bones called vertebrae. A shock absorbing structure called the intervertebral disc is located between each vertebra, except for the first and second vertebrae located in the neck. The spinal cord runs through a large canal within the bones of the vertebrae. The spinal cord is similar to a telephone cable that has many wires, which transmits signals from the brain to control the internal organs and the muscles. What is wobbler syndrome? Wobbler syndrome, also called cervical spondolytic myelopathy, is a multifactorial disease that compresses the spinal cord in the neck. This results in damage and dysfunction of the spinal cord. Abnormalities of the spine that contribute to this condition include narrowing of the vertebral canal; protrusion of the intervertebral disk; thickening of the ligament located immediately beneath the spinal cord; partial dislocation of the neck bones; and thickening of the joints of the vertebrae. The compression of the spinal cord may be static, meaning that flexion, extension or traction of the neck does not change the amount of compression on the

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Carpal Hyperextension Injury

Anatomy The carpus of the dog can be equated with the wrist in man. It is made of many small bones that form three major joints. Normally, the top joint is very flexible, whereas the remaining joints have limited range of motion. The backside of the carpus is supported by a very strong ligamentous structure called the palmar fibrocartilage, which prevents the joints from overextending (hyperextension). Cause of carpal hyperextension injury The cause of a hyperextension injury is due to tearing of the palmar fibrocartilage. This type of injury can be due to a single isolated traumatic event, such as jumping off a roof or out of a window. In other cases, it is due to repeated injury to the palmar fibrocartilage due to jumping off elevated surfaces or out of vehicles. Once the palmar fibrocartilage tears, conservative measures such as splinting or casting the limb are consistently ineffective in nearly all cases. Signs and Diagnosis Carpal hyperextension injury is most commonly seen in large active dogs; however, small breeds certainly can sustain a similar injury. Warning signs of this condition include lameness that worsens with exercise. Swelling and hyperextension of the carpus also are common clinical signs. The diagnosis

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Digital (Toe) Tumors

Tumors of the digits (toes) most commonly include squamous cell carcinoma, melanoma, osteosarcoma, hemangiopericytoma, benign soft tissue tumors and malignant soft tissue tumors. Squamous cell carcinoma accounts for more than 50% of all digital tumors. This tumor originates from skin cells, is very locally invasive, and commonly destroys the bone in the digit. Melanoma, the second most common tumor, accounts for 16% of all digital tumors. These tumors originate from the pigment-producing cells in the skin called melanocytes, which are responsible for giving humans a tan with sun exposure. Melanomas of the nail bed spread rapidly to other areas of the body. At the time of diagnosis of a digital melanoma, one-third of all affected dogs will have detectable spread (metastasis) to the lungs. Melanomas of the digits that do not involve the nail bed and are confirmed to be benign on the biopsy usually do not metastasize. Signs and diagnosis Squamous cell carcinoma is most commonly seen in large breed dogs with black coats. Overrepresented breeds include Labrador retrievers and standard poodles. Digital tumors cause the toe to swell see photo below right) and may cause lameness. Initially, a tumor of the digit may mimic the appearance of an

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Biceps Tenosynovitis

Anatomy The biceps tendon attaches onto the shoulder blade bone (scapula), passes through the shoulder joint and then through a groove in the top of the humerus bone (bicipital groove). The tendon widens into the belly of the biceps muscle and then attaches into the radius and ulna bones of the forelimb. Contraction of the biceps muscle flexes the elbow and extends the shoulder joint. What is Biceps Tenosynovitis Biceps tenosynovitis is inflammation of the tendon of the biceps muscle (same muscle that we have in our upper arm) and its sheath. The causes of this problem are repeated injury to the biceps tendon, acute severe trauma, and chronic osteochondritis dissecans of the shoulder joint. Signs and diagnosis Most dogs that develop biceps tenosynovitis are mature, medium to large breeds; however, small breed dogs also can develop this condition. Intermittent or continuous lameness, which is exacerbated by exercise, is a common clinical sign of biceps tenosynovitis. Your companion’s veterinarian may find pain upon hyperflexion of the shoulder and extension of the elbow, as this stretches the inflamed biceps tendon. Direct palpation of the tendon near the shoulder joint also may elicit a painful response. Atrophy of the muscles of the

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Angular Limb Deformity

Anatomy In dogs, the growth plates are responsible for longitudinal bone growth, which takes place primarily during the fourth to eighth months after birth. On an X-ray, growth plates appear as a black lines at the ends of the bones. By one year of age, most growth plates have disappeared and growth, for the most part, ceases. The growth plate is the softest part of the bone; therefore, it is prone to injury. If an injury to the growth plate has occurred during the period of rapid growth, the bone may not grow to a normal length, or it may become twisted. Cause of angular limb deformity of the forelimb The forelimb has two bones between the carpus (wrist) and the elbow joint, the radius and ulna. The growth plate of the ulna, located near the carpus, is particularly susceptible to becoming injured, as it is shaped like a cone (indicated by the white arrow). This V-shaped (conical) growth plate of the ulna is responsible for about 90% of the bone’s longitudinal growth. Therefore, following damage to this growth plate, the ulna will be shorter than normal. The result is a “bow-string” effect in which the radius becomes bowed. This

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