LUXATING PATELLA

Dislocating Kneecap in Dogs - Article Written by Dr. Daniel A. Degner, Board-certified Veterinary Surgeon (DACVS)

Key Points

Dislocation of the kneecap is painful and results in lameness Evaluation of limb alignment may be recommended, especially in large breed dogs to assess the need to correct this; failure to address this can result in increased failure rates Concurrent cruciate ligament injury may be present in dogs that have a dislocating kneecap, therefore this may also need to be addressed Prognosis generally is very good - the higher the grade of the patellar luxation, the greater the failure rate unless more corrective surgeries are done

Introduction

The patella (commonly known as the kneecap) normally rides in a groove at the bottom of the femur at the level of the knee joint in a groove called the trochlear groove; Fig 1 and 2 show a front view of the knee joint; Fig 1 demonstrates the patella in the groove, where as Fig 2 demonstrates the knee cap dislocated out out of the groove (P=patella; F=femoropatellar ligaments which hold the patella in the groove; PL=patellar ligament; G=trochlear groove that the patella rides in). Fig 3 demonstrates a skyline view of the trochlear groove and the patella - you are looking down the thigh or femur bone toward the knee joint; take note of the deep groove that is found in a normal animal. Patellar luxation is caused by congenital abnormality usually at the level of the hip joint and results in abnormal forces on the kneecap, which cause it to eventually ride outside of the groove. The groove becomes very shallow and the attachment of the ligament of the patella may be malpositioned on the tibia bone. If the patellar luxation occurs in immature animals, the tibia and femur bones become twisted.

Clinical signs

Lameness
Intermittent skipping gait
Pain
Stiffness of the hind limb
Some pets show only a single sign, whereas others show many signs of the condition
Failure to treat the condition could lead progressive debilitating arthritis of the joint

Surgery

If the groove that the patella rides in is shallow or misshapen, it is surgically deepened; we usually use an advanced technique to perform this called the block osteotomy. The illustration right demonstrates elevation of the cartilage/bone plate. I now use a modified procedure in which the cartialge/bone plate is left attached to the soft tissues (periosteum) at the top of the groove, thus minimizing the risk that the cartilage/bone plate will become displaced in the joint.
Additional bone is removed from the raw bone bed and the cartilage/bone plate is replaced creating a deep groove for the patella to ride in. The benefit of the block osteotomy is that it uniformly deepens the groove from top to bottom and preserves the cartilage that the patella rides on.

If the attachment of the patellar ligament to the tibia, called the tibial crest, is in the wrong position, it is repositioned. This is done by creating a cut in the tibial crest (see illustrations below) and reattaching the bone in a position so that the patella is realigned within the trochlear groove. Pins are used to fasten the bone in place; the pins usually do not need to be removed unless they migrate out of position or a bubble of fluid (seroma) develops over the end of the pin.

The soft tissues along the side of the patella usually are stretched and are tightened to provide additional support to keep the patella in the trochlear groove. The femur bone may be twisted in some dogs which worsens the condition of the luxating patella. I find that dogs that have a greater than 14 degree bowing (varus) of the thigh bone should have this surgically corrected. Special alignment x-rays are usually taken in large breed dogs to check for this problem. A support bandage is usually not used after surgery so that rehabilitation therapy can be started soon after surgery.

Convalescence

By 10 to 14 days after the surgery your pet should be touching the toes to the ground at a walk
By 2 to 3 months after surgery your pet should be using the limb well
If your pet does not follow a normal progression of recovery, the surgeon should be notified

Prognosis

Surgery has approximately a 90% success rate. Success is defined as the return of good function of the limb Unfortunately surgery will not remove the arthritis that may already be present in the knee. As a result, your pet may have some stiffness of the limb in the mornings or after laying down for a nap. In addition, your pet may have some lameness after heavy exercise By having the surgery done earlier, the chance of developing significant arthritis is decreased Dogs that have a higher grade of patellar luxation may have increased risk for reluxation of the patella
Large breed dogs that have patellar luxation may have increased risk for reluxation of the patella if a corrective femoral osteotomy is not performed

Potential complications

There is an inherent risk of anesthetic death with any procedure requiring anesthesia, however, this is very small Infection of the surgical site, although not common, can occur Pin migration
Seroma formation over the pins If exercise is not minimized for 8 weeks after the surgery, breakdown of the repair may occur, thus requiring a second surgery

If you are concerned about the health of your pet you should contact your veterinary surgeon at all times.

My thanks to Dr. Daniel A. Degner for allowing me to use his material, original can be viewed at the Vet Surgery Central website.

PROGRESSIVE RETINAL ATROPHY (PRA)

General Information

Progressive retinal atrophy (PRA) is a name given to a group of eye diseases of similar character. PRA causes no pain or discomfort but may result in permanent blindness. The word atrophy means wasting away. PRA develops after birth and in some breeds has been determined to be inherited from both parents. It affects the retina, which lines the back portion of the inside of the eye. The retina contains the light-sensitive rods and cones that change light into energy for transmitting messages to the brain. The retina is similar to the film in a camera; the image or picture is received on it. PRA can occur in all breeds of dogs although certain breeds are at higher risk. It appears earlier in some breeds and can take several years to cause complete blindness. An early sign of PRA is inability to see in dim light or at night. For example, an animal with PRA may hesitate to go from a well-lighted room into a darkened room. Due to PRA's slow progress, most pets adapt very well to the gradual loss of sight. Many owners do not realize their pet is becoming blind. Animals compensate well for blindness, because their senses are much more acute than those of people.

Important Points about PRA:

1. No effective treatment is available.

2. Complete blindness eventually results.

3. The condition, however, is not painful.

4. PRA is prevented through selective breeding of animals with normal eyes.

5. Sometimes cataracts develop secondary to the retinal degeneration. But because of the retinal degeneration, cataract removal would not help the animal regain vision.

6. Poor vision in dim light is the first sign you will see in your dog.

7. You may also eventually see dilated pupils.

If you are concerned about the health of your pet you should contact your veterinary surgeon at all times.

PORTOSYSTEMIC SHUNTS

Article Written by Dr. Daniel A. Degner, Board-certified Veterinary Surgeon (DACVS)

Key Points

A portosystemic shunt, is an abnormal vessel that allows blood to bypass the liver. As a result the blood is not cleansed by one of the bodies filters: the liver. Generally the bile acids levels (after feeding a meal) in patients having a shunt are higher than 100. Surgery is the best treatment for a shunt. The overall success rate is about 85%.

Shunt anatomy and physiology

In the fetus a shunt, called the patent ductus venosus, is present and bypasses blood away from the liver to the placenta so that the mother can cleanse the blood for the fetus.
Once the fetus is born the shunt closes within three days after birth and the puppy's liver must clean the blood. Sometimes the shunt does not close off. A portosystemic shunt, therefore is an abnormal vessel that allows blood to bypass the liver. As a result the blood is not cleansed by one of the bodies filters: the liver. These dogs also have much less blood that flows to the liver which causes the liver to remain small. There are many variations of congential portosystemic shunts that are found at surgery, however there two main groups: shunts located in the liver (intrahepatic shunt) and shunts located outside of the liver tissue (extrahepatic shunt). The intrahepatic shunt is most commonly found in large breed dogs and extrahepatic shunts are seen in small breeds. Above is a diagram showing the blood flow from the intestines, through the shunt (labeled) , then to the heart. Most of the blood does not flow to the liver due to the resistance of the filters in the liver, thus the blood is not cleansed by the liver

Clinical signs

Abnormal behavior after eating
Pacing and aimless wandering
Pressing the head against the wall
Episodes of apparent blindness
Seizures
Poor weight gain
Stunted growth
Excessive sleeping and lethargy
Straining to urinate due to bladder stone formation
Patient with a shunt may have many clinical signs and some have only a single clinical sign
Some dogs do not show signs until they are older

Diagnosis

A variety of blood tests can be used to help to support a diagnosis of a portosystemic shunt.
Bile acid test are always elevated. Generally the bile acids levels (after feeding a meal) in patients having a shunt are higher than 100. Other diseases such as microvascular dysplasia, generalized liver disease, and acquired shunts due to liver cirrhosis can also cause elevated bile acids tests. Sometimes the shunt can be identified with ultrasound imaging. Nuclear scintigraphy is a fairly reliable test to ascertain whether a shunt is present, but may not be able to differentiate acquired from congenital shunts. In most dogs we are able to identify the portosystemic shunt at the time of surgery. Sometimes multiple acquired shunts, caused by end-stage liver disease are found; unfortunately no surgical therapy is useful to treat this (other than liver transplant, which is not practical in dogs). If the shunt cannot be found at the time of surgery, dye is injected into one of the veins going to the liver and x-rays are taken (portogram). This will show the blood supply of the liver and the offending shunt, if it is present.

Treatment

If possible, we prefer to have the patient as stable as possible prior to surgery. This involves having your pet on a low protein diet and administering prescribed medication. Antibiotics are used as bacteria, which are normally removed by the liver, by pass the liver and result in bacteria circulating in the blood. Lactulose is a medication which traps toxins such as ammonia in the stool. It also decreases the transit time of the stool so that toxins are expelled quicker (thus the pet will defecate more often). Low protein diet should be fed in order to decrease poisons that affect the brain. Surgery is the best treatment for a shunt. Usually at the time of surgery the shunt can be identified (arrow showing large vessel) as is seen in photo below.

For pets that have a shunt that is located outside of the liver, an ameroid constrictor ring is placed around the vessel (in photo below see metal ring). This device slowly closes the shunt over a period of 6 weeks.If the shunt is located in the liver the surgery is much more complex. Because these shunts are usually found in large breed dogs, the shunt likewise is frequently very large. We have successfully used large ameroid constrictors for this purpose, but in some cases two surgeries are needed.

Potential complications

Complications can include high blood pressure (portal hypertension) of the vessels going to the liver, which results in fluid accumulation in the belly. If a high level of portal hypertension is present after the shunt is tied off, the pet will die.
About 15 % of the dogs having surgery will develop small-acquired shunts that basically function like the congenital shunt and thus the pet may need medical treatment for life.
Infection is an uncommon but possible complication.
Seizures may occur in the first 3 to 5 days after surgery.
Seizures can be caused by low blood sugar levels, which is easily treated
Seizures can be caused by the imbalances of the chemicals within the brain as the blood is being cleansed. These patients may die if they are not responsive to medication.

Postop care

After surgery your pet will still need to eat a low protein diet. Once bile acid levels (blood test) normalize a regular diet can be fed.
Lactulose and antibiotics are continued for about 10 days after surgery.

Prognosis

The overall success rate is about 85%. Usually the pet will start to feel better with 10 to 14 days after surgery

If you are concerned about the health of your pet you should contact your veterinary surgeon at all times.

My thanks to Dr. Daniel A. Degner for allowing me to use his material, original can be viewed at the Vet Surgery Central website.

TRACHEAL COLLAPSE

Tracheal Collapse in Dogs - Article Written by Dr. Daniel A. Degner, Board-certified Veterinary Surgeon (DACVS)

Key Points

Tracheal collapse is commonly seen in small breed dogs such as Yorkshire terriers, Poodles, and Pomeranians to name a few Tracheal collapse is caused by a progressive weakening of the the tracheal rings When medical treatment is not effective surgery is a good option Prognosis is good following surgery.

Anatomy

• The trachea, commonly known as the windpipe, is a tube that allows passage of air from the back of the throat to the lungs


• There are two regions of the trachea: cervical which is located in the neck and the thoracic trachea which is located in the chest


• The trachea is made of many "C"-shaped cartilage rings and a dorsal tracheal ligament which connects the "C" to form a complete tube


• Each of the cartilages is connected together by fibrous tissue


• The voice box or larynx is the gateway of the trachea and prevents food and water from getting into the trachea Two delicate nerves located on each side of the trachea, called the recurrent laryngeal nerves, control the muscles that open the doors of the voice box; damage to these nerves causes laryngeal paralysis


• Below is a section of a normal trachea illustrating the dorsal tracheal ligament that is on the top side of the trachea and the cartilage rings that maintain the structure of the trachea
  
  

Cause of tracheal collapse

• Tracheal collapse is commonly seen in small breed dogs such as Yorkshire terriers, Poodles, and Pomeranians to name a few


• Tracheal collapse is caused by a progressive weakening of the the tracheal rings. One study showed that dogs with tracheal collapse have less chondroitin sulfate in their tracheal rings


• Cushing's disease (adrenal gland produces too much steroid) can weaken the cartilages


• Below is an illustration showing about 50% collapse of the trachea, as the cartilage rings become progressively weaker, the trachea continues to collapse

Clinical signs

• Goose honking cough is the classic sign of this disease


• Coughing frequently is worsened by hot weather, exercise and excitement


• Fainting spells due to lack of oxygen


• Exercise intolerance

Diagnostic testing

• Complete blood cell count


• Chemistry profile


• Testing for Cushing's disease if clinical signs are present


• Urinalysis


• Fluoroscopy - movie type of x-ray (real time) that allows evaluation of the airway during inspiration and expiration


• Scoping the airways


• Chest radiographs below demonstrates a severely collapsed trachea (dark grey thin stripe labeled as trachea) in a dog; both the trachea in the neck and in the chest are collapsed
  

Treatment

• Medical therapy
  Cough suppressants
  Antibiotics if indicated
  Short course of steroids
  Bronchodilators
  Weight loss
  Use harness instead of neck collar
  Limit excitement
  Keep out of hot environment


• Surgery
  Indicated if collapse is advanced
  Indicated if collapse is not responsive to medical therapy
  Surgery involves suturing the collapsed trachea to plastic rings which are placed around the trachea (see illustration); in the photo below, two clear plastic rings have been sutured to the trachea; an instrument has been passed beneath the trachea in order to pass the third plastic ring.

Aftercare

• Cough suppressants are needed while the trachea is healing - excessive cough can break the repair down


• Pain medication


• Antibiotics


• Exercise restriction for 4 month


• Use harness instead of neck collars


• Weight reduction

Potential complications

• Laryngeal paralysis


• Swelling of the airway


• Necrosis of the trachea


• Recurrence


• Anesthetic death


• Pneumonia


• Infection of surgical site

If you are concerned about the health of your pet you should contact your veterinary surgeon at all times.

My thanks to Dr. Daniel A. Degner for allowing me to use his material, original can be viewed at the Vet Surgery Central website.

Legg-Perthes disease

Key Points A disease of the hip joint that results in abnormal deformity of the ball of the hip joint This is a disease primarily seen in small breed dogs Treatment is femoral head and neck excision Prognosis is very good, providing that rehabilitation therapy is done after surgery

Same disease but different names (synonyms) Calve-Perthes disease Legg-Perthes disease Avascular necrosis of the femoral head Coxa plana Osteochondritis juvenilis What is it? A disease of the hip joint that results in abnormal deformity of the ball of the hip joint The disease starts with an insult to the blood supply to the head of the femur bone As the blood supply is damaged, the bone dies off The bone in the femoral head collapses and the cartilage coating of the femoral head becomes cracked and deformed Arthritis or inflammation of the hip joint results, which causes pain and lameness Cause Not completely understood Genetics - can be autosomal recessive gene in some dogs Injury - compression of the vessels of in the femoral head Abnormal sex hormone activity - preconcious Because of the potential heritability of this disease, affected dogs should not be bred Signalment Typically dogs that are less than 1 year of age (5 to 8 months of age is most common with peak incidence around 7 months of age) Breeds commonly affected Yorkshire Terriers - most common breed Westies Many other small breed dogs Equal risk for males versus females Clinical signs Irritability Chewing at hip of flank region Progressive lameness (may take about 2 months until dog is not bearing any weight on limb) Stiffness of affected limb (85 to 90% of dogs have only one hip affected) Atrophy of muscles of affected limb Pain when moving the hip - especially when extending the limb backward and also to the side Crepitus or crunchy feel of the hip joint on range of motion Diagnosis Physical examination - hip pain Radiographs flattening of femoral head lucencies of femoral head bone spurs - arthritic degeneration increased joint space Below is a radiograph of the hips of a Yorkie that has the disease; take note of the moth-eaten appearance of the femoral head (below left and right) Treatment Conservative treatment with strict cage rest and physical therapy could be successful only if the femoral head is still has its normal shape and is is tightly seated in the socket; monthly radiographs should be made until the pet is 1 year of age Surgery - femoral head and neck excision is the treatment of choice if the radiographs show deformity of the femoral head or looseness of the hip joint; this surgery involves removing the femoral head and neck Below is a photo as the femoral head is being removed from the hip joint shown above; take note of the deformed head of the femur and the cracks in the cartilage. The radiograph below demonstrates a femoral head and neck excision (arrow) Prognosis Femoral head and neck excision usually gives a satisfactory result - the pet is greatly improved; some dogs may have residual lameness, especially with heavy exercise or weather changes Postop care After Care and Convalescence A prescribed analgesic medication should be administered in the postop period at home. Nonsteroidal anti-inflammatory medications are very beneficial to reduce pain at the surgical site and encourage weight bearing. In some cases, antibiotics may be prescribed. Activity is not limited after surgery. In fact, exercise will help to maintain a good range of motion of the hip joint. The owner should do rehabilitation therapy using the TopDog Home Rehabilitation guide for FHO Surgery found at www.fhoguide.com until the pet is using the limb normally. Flexion and extension of the hip joint is essential in the recovery period. Rehabilitation therapy will help prevent adhesions from forming, thus maintaining a good range of motion of the hip region. If possible, swimming should be started after the incision has healed. It is also highly recommended that rehabilitation therapy sessions be scheduled with a professionally trained therapist. Most dogs will start to bear a small amount of weight on the limb within 2 weeks after surgery. Within 4 to 6 weeks the pet should bear a moderate amount of weight on the limb. By 2 to 3 months after surgery, recovery is complete. The pet should be examined 2 weeks and 2 months after surgery to ensure that the hip region is healing well. Most small pets do well following femoral head and neck excision surgery. Larger dogs can also do well, but some weakness on that limb frequently can be seen. This is due to the muscles supporting the region of the hip instead of the actual joint. As a result, heavy exercise can cause the pet to become stiff or lame. Anti-inflammatory medication can be given to give your pet relief if needed. If your pet is a medium to large breed dog, total hip replacement is the preferred technique over the femoral head and neck excision surgery. Complications As with any surgery, complications may arise. Even though rare, anesthetic death can occur. With the use of modern anesthetic protocols and extensive monitoring devices (blood pressure, EKG, pulse oximetry, inspiratory and expiratory carbon dioxide levels, and respiration rate), the risk of problems with anesthesia is minimal. Infection is also an unusual complication, as strict sterile technique is used during the surgery. Poor range of motion of the hip joint can occur and is usually due to a lack of rehabilitation therapy. If your pet is not using the limb very well after 2 to 3 weeks, anti-inflammatory therapy should be continued for another 2 to 4 weeks. Sciatic nerve damage is a rare complication of FHO surgery, but frequently is a transient problem.