TIBIAL PLATEAU LEVELING OSTEOTOMY

For treatment of cranial cruciate ligament injury
The most common cause of hind leg lameness in the dog is injury to the cranial cruciate ligament of the knee (stifle). This injury leads to degenerative changes (osteoarthritis) in the joint including cartilage damage, bone spur (osteophyte) production, and cartilage pad (meniscal) injury.

KNEE JOINT FUNCTION

The knee joint of the dog is held together by five ligaments and two cartilage pads. There are straight ligaments on the inside, outside, and front of the knee as well as two ligaments (the cranial and caudal cruciate ligaments) within the joint that cross over to provide forward and backward stability (Figure 1). Although the knee joints of dogs and humans have similar anatomy, the forces applied to these joints during standing, walking, or running are different.
Humans can stand easily with little stress on our knee ligaments because our hip, knee and ankle joints are parallel to each other and perpendicular to the bones. Dogs, however, stand on their toes with their knees bent forward. The upper portion of the tibia bone (the tibial plateau) is sloped and weight-bearing creates a force that pushes the femur bone down this slope.
The tibia bone is thereby moved forward with a force called cranial tibial thrust. This force is only opposed by the cranial cruciate ligament. With every step a dog takes, stress is applied to the ligament. In dogs with a steep tibial plateau slope or that have a less-bent knee conformation, enormous forces are placed on the ligament (Figure 2). Over time, this can result in ligament injury or complete ligament rupture. When the knee becomes unstable due to rupture of the cranial cruciate ligament the cartilage pads are also prone to injury.

SYMPTOMS

When the ligament is injured, pain and swelling in the knee joint occur. This is usually accompanied by hind leg lameness which can be mild or severe depending on the degree of injury. The joint will typically settle down after rest and some pain relief but the lameness persists. The pain and swelling tend to reoccur easily even with only minimal activity. If not treated surgically, the joint will become arthritic and medication will have little effect on the pain and lameness the dog experiences.

DIAGNOSIS

A thorough orthopaedic and neurologic examination is performed evaluating the dog when walking and by manipulating all four limbs and the spine. Swelling. pain, and joint looseness (instability) can frequently be felt in the affected knee. Sedation or anaesthesia and x-rays are necessary to show signs of arthritis and to measure the tibial slope.

SURGERY

Traditional surgery for cranial cruciate ligament injury involves restricting the joint instability by placing nylon outside of the joint or the dog’s own tissue inside the joint in the same direction as the original ligament. Whilst these techniques have reasonable results, the joint instability returns and arthritis continues to develop rapidly.
The TPLO is used to neutralise the forces of cranial tibial thrust. The procedure “levels” the tibial plateau eliminating the need for the cranial cruciate ligament. The procedure involves cutting a circular bone cut in the top of the tibia (Figure 3). The tibial plateau portion is rotated before applying a small metal plate and metal screws (Figure 4). Injuries to the cartilage pads are also corrected during surgery.

RESULTS

Healing of the bone takes about two months and most dogs can return to full activity 3-4 months after surgery. Dogs, particularly those larger than 30kg, show excellent results with minimal progression of arthritis, few complications and normal function.

DISK FUNCTION

The intervertebral disk of the dog acts as a cushion between the spinal bones (vertebrae) to absorb the shocks and movements of normal activity. The normal disk is like a “jelly doughnut” with a gelatinous centre and an outer ring of stronger fibrous tissue. In certain breeds of dog (Dachshund, Poodle, Beagle, Spaniel, Corgi), the disk degenerates at a very early age. As the dog ages, the jelly like component of the disk becomes more gritty and less resistant to pressure. The disk is then no longer able to cushion the spine and the contents of the centre may forcibly squirt out and bruise the spinal cord. Alternatively, the outer part of the disk may bulge up putting pressure on the spinal cord.

DIAGNOSIS

A thorough neurologic examination is performed evaluating the head, all four limbs, and the spine. Pain can frequently be felt at the site of the affected disk. Anaesthesia and X-rays can help to show signs of narrowed disk spaces and degenerative disks. To confirm the diagnosis, a CT scan is recommended as this provides us with the best information on the spine. A special X-ray test called a myelogram can be helpful, in addition to a CT scan. Some dogs have an associated instability of the vertebrae that has contributed to the disk degenerating.

SURGERY

Dogs that have severe neck pain.or significant spinal cord damage are also candidates for surgery. The most common procedure is a ventral slot, which involves drilling a slot in the base of the vertebrae to relieve the spinal cord pressure and allow the delicate extraction of the disk material. Sometimes, the central portion of adjacent degenerative disks is removed to reduce the chance of further disk

SYMPTOMS

Syleptoms typically develop, in order of severity, from neck pain to weakness and wobbliness then finally to unwillingness to stand depending on the speed or the amount of the disk rupture. In the most severe cases, dogs lose the ability to walk and become quadriplegic.

MEDICAL TREATMENT

Some dogs with only mild symptoms will respond to medical treatment. Generally this involves three or four weeks of strict confinement to a cage with the dog only allowed out to go to the toilet. Pain relief (cortisone or aspirin-like medication) is given at the same time but this does not mean the dog can be more active. Dogs that do not improve or get worse with medical treatment are candidates for surgery.

RESULTS

Dogs that have retained the ability to walk prior to surgery have a 95% chance of complete recovery following surgery. Complete healing of the spinal cord can take up to six months to occur. Regular progress in spinal cord recovery is seen during this time. Dogs with unstable vertebrae have an increased risk of further instability developing later in life.

Rupture

For dogs with instability of the vertebrae, additional surgical stabilisation may be performed. This is done using metal plates and screws or bone cement.

PROGNOSIS

The prognosis for recovery is mostly dependent on the severity of the damage to the spinal cord. The ability to walk before treatment is the key indicator for prognosis in dogs with a slipped disk in the neck.

POSTOPERATIVE CARE

EXERCISE CONTROL

To allow the bone to heal following the surgery, complete restriction of exercise is absolutely necessary for the first 6 weeks. Your dog can be walked on a lead for toileting Light (5-15 minutes) lead walks can begin after 4 weeks.

BANDAGE AND SUTURE REMOVAL

A bandage is generally placed over the stitches for protection. This bandage should be removed 2-3 days after surgery. The skin stitches need to be removed 10-14 days following surgery. These tasks can be done by your regular veterinarian. Please call our hospital if there is any swelling, discharge or redness around the stitches.

MEDICATION

Most dogs are sent home with medication for additional pain relief. Sometimes, antibiotics are also dispensed. Give the medications as prescribed. It is possible that a longer course of treatment will be necessary. Please let us know two days before suture removal if you think more medication is required or you may be charged an urgent fee.

PHYSIOTHERAPY

Physiotherapy is an important part of your dog's recovery. We strongly recommend a consultation with a recognised animal physiotherapist. Home-based physiotherapy should consist of a warm compress applied to the region of the stitches for 15 minutes followed by gentle massage of the muscles. This can be followed by gentle flexing and extending of the leg.

After the bone has healed, your dog can begin more active physiotherapy with regular controlled exercise. Running without leash control is recommended for only short periods. Regular swimming is an excellent way of providing active exercise without joint stress.

FURTHER X-RAYS

Your dog should return to our hospital for further x-rays six weeks after surgery to evaluate the bone healing. The dog will require sedation to get good x-rays. Do not feed your dog on the morning of this visit. This assessment will incur an additional cost.

LONG-TERM TREATMENT

Some dogs will need long-term medication to control the arthritis already present in the knee prior to the surgery. Cartilage-protecting agents (oratiga fatty acids, glucosamine, green-lipped musel, fish oil) may help lubricate the joint and keep cartilage healthy. Generally, lifelong supplementation is necessary.

Dogs with knee arthritis may benefit from feeding with Hill's Prescription Diet j/d Canine Mobility. This diet can improve your dog's signs of arthritis with a clinically proven combination of nutrients.

Anti-inflammatory medication (aspirin-like drugs) can be helpful in reducing pain but should only be necessary occasionally.

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