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  6. Tibial Plateau Levelling Osteotomy (TPLO)

Tibial Plateau Levelling Osteotomy

What is TPLO surgery?
TPLO stands for Tibial Plateau Levelling Osteotomy. It is a surgical procedure that involves adjusting the tibial plateau (the surface at the top of the shinbone) by cutting the bone with a purpose-made surgical saw, rotating the cut portion, and securing it in a new position with a plate and screws.
How does TPLO surgery work?
In dogs, the tibial plateau is slopes downwards (towards the tail). During normal weight-bearing, the cranial cruciate ligament acts to prevent the shinbone (tibia) from slipping forwards relative to the thighbone (femur). In dogs with cranial cruciate ligament disease, this movement is not resisted, which causes the knee joint to ‘give way’, causing pain and lameness.

TPLO surgery works to make the top of the tibia almost flat, so when the dog is weightbearing, the femur rests on the top of the tibial plateau rather than slipping backwards and pushing the tibia forwards. This prevents the sensation of the knee giving way and should remove or reduce the lameness previously seen.

What does TPLO surgery involve?

The procedure may vary slightly depending on your surgeon and they will be able to provide you with more specific information.

All TPLO procedures are performed under a general anaesthetic. Specialised X-rays will be collected, if they have not been taken previously, to allow surgical measurements, which can vary widely between different dogs. Your pet will likely need to have a full clip of the affected leg stretching from the ankle to the hip.

Generally, surgery will start with opening the capsule surrounding the knee joint and assessing for damage to the shock-absorbing cartilage pads that sit between the bones (menisci). If damage is seen, then the damaged portion is removed before the TPLO is performed. This may be done as an open approach or keyhole – with a specialised camera.
The tibia is then exposed and marked with measurements taken from the pre-operative X-rays. The bone is cut with a special curved saw blade, and then the cut portion is turned to a new position. At this point, a special TPLO plate and screws are used to hold the bone in place while it heals.

X-rays are taken at the end of surgery to ensure the plate and screws are in the right position and that the new angle is flat enough.

What does post-operative care involve?

Medication
Your dog will require a course of pain relief and sometimes antibiotics following surgery; these are typically given orally in tablet or liquid form.

Exercise
Exercise is beneficial during the recovery, although this must be strictly controlled and will be significantly reduced during the first eight weeks following surgery. A period of very strict exercise restriction is likely immediately after surgery and will require your dog to be crate-rested or confined to a small room without access to furniture. Your surgeon will provide you with more detailed instructions on how to manage your dog’s exercise following surgery.

Follow up visits
Dependent on how your pet’s surgical wound has been repaired, a follow-up visit to your vet is often needed around two weeks after surgery. Most dogs will need to wear a buster collar until this time to prevent interference with the wound which may lead to infection.
Depending on progress, post-operative X-rays are usually performed around eight weeks after surgery to check healing is progressing well.

Weight control
Unfortunately, regardless of treatment (or lack of treatment), all dogs are likely to be predisposed to the development of osteoarthritis in the affected joint following cranial cruciate ligament disease. Because of this, it is recommended that they maintain a slim body condition. Your vet will be able to give you more information regarding weight control plans if this is required.

Hydrotherapy/physiotherapy
Hydrotherapy and/or physiotherapy can be useful in the post-operative period and can be considered once the skin wound has healed. Your vet can advise you if this is appropriate for your pet.

What is the prognosis following TPLO?
TPLO surgery has a very high success rate, with 90—95% dogs regaining complete or near-complete function of the affected leg and 93% of owners reporting that they are satisfied with the procedure 12 months after surgery.

All dogs with cranial cruciate ligament rupture are expected to eventually develop at least some signs of osteoarthritis in the affected joint, but this is likely to be reduced or delayed in dogs who have had a surgical procedure.

Around 50% of dogs will develop cranial cruciate ligament disease in the other hind limb, in some cases this requires immediate surgery, and in others, it may be many years.

What are the risks of a TPLO?

Unfortunately, complications can occur with any surgical procedure. The complication rate for TPLO surgery is low, but potential complications include:

Infection
Any surgery carries a small risk of infection. Orthopaedic surgery carries a slightly higher risk because bacteria can stick to the metal implants, which makes it difficult for the immune system to reach them. To reduce this risk, all dogs receive antibiotics during surgery. If your dog licks their wound after surgery, they can introduce infection, which is why most dogs will need to wear a buster collar until the surgical wound has healed.

Screw-loosening/Implant failure
In a small number of dogs, the screws that hold the bone in its new position can become loose over time. If this happens, excessive movement of the bone segments against one another can delay healing and, in the worst-case scenario, the screws or plate can break and require replacement. The risk of this happening increases substantially if exercise is not sufficiently restricted following surgery.

Delayed healing of the bone
The bone needs to heal in order to become strong enough to support your dog’s normal activity. All dogs heal at slightly different rates and often patience is required. Insufficient exercise restriction after surgery, as well as some underlying health conditions, can predispose a dog to slow healing.

Fracture of the tibial tuberosity
The movement of the semi-circular segment of bone during a TPLO alters the shape of the tibia and leaves the insertion site of the patellar tendon (known as the tibial tuberosity) slightly weakened. Excessive forces through the joint in the early post-operative period can result in fracture of this bone which would require surgical repair.

Patellar Tendon Damage/Inflammation
The circular cut in the tibia is made very close to the point at which the tendon that attaches to the kneecap (patellar tendon) inserts onto the bone. While every effort is made to protect it, damage to the tendon is possible during the cutting of the bone. The tendon can also become inflamed in the months following surgery due to alteration in the forces acting across the joint.

Subsequent meniscal injury
In up to 7% of cases, the menisci appear normal at the time of surgery but are later damaged due to continued, mild degrees of joint instability. Lameness may persist longer than expected post-surgery, or dogs may seemingly recover before suddenly becoming lame on the leg once more. If this occurs, repeat surgery will be required to inspect the meniscus for damage and cut away any torn portions.

Which dogs will benefit from a TPLO?
Developments in the equipment used for TPLO procedures have made it a possibility for most sizes of dogs, with particular benefits for large or very active dogs. Although evidence is low, some studies have suggested that this procedure does have an advantage in returning dogs to normal function faster than other procedures and so it may be recommended in many cases.

However, TPLO is often more expensive than other procedures and less widely offered, which may affect your decision. It also does typically involve a much stricter period of exercise rest, with greater potential for serious complications if this is not enforced, than procedures such as the lateral suture.

Contraindications for surgery may include:
· Dogs who are receiving medication that suppresses their immune system and makes them likely to experience delayed fracture healing.
· Dogs with limb deformities that may need to be corrected by other procedures.

References
Christopher, SA, Beetem, J, Cook, JL. 2013. Comparison of long-term outcomes associated with three surgical techniques for treatment of cranial cruciate ligament disease in dogs. Veterinary Surgery. 42(3):329-34
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