Veterinary TPLO, tibial plateau levelling osteotomy

Tibial Plateau Levelling Osteotomy

These notes do not cover all aspects of tibial plateau levelling osteotomy,
please ask if you require further information.

Why is tibial plateau levelling osteotomy needed?

Injury to the cranial cruciate ligament is the most common cause of lameness in the hind limb of dogs in our clinics. These injuries can occur as a result of trauma (usually the leg being trapped in a gate or in a hole) but are more commonly caused by degeneration ('abnormal wear') of the ligament in normal use. It is recognised that certain breeds are more prone to degeneration of the ligament than others and in these breeds failure of the cranial cruciate ligament in one knee, or in both knees, can occur as young as 6 months of age. The factors that lead to this are very complex and inter-dependent, but an abnormality in the shape of the knee itself is thought to be one important factor. In particular an abnormal backward slope to the upper part of the shin bone (the tibial plateau) increases strain on the cranial cruciate ligament leading to its failure and an unstable knee. Tibial plateau levelling osteotomy is a surgery that can address this abnormality and re-stabilise the knee.

What is involved?

First the diagnosis of cranial cruciate ligament failure must be confirmed. This requires an orthopaedic examination and, in many cases, examination under anaesthesia, radiographs of the knees (and sometimes other structures) and the analysis of joint fluid removed from the knee joints. Tibial plateau levelling osteotomy surgery is a major surgery which needs planning and a considerable amount of equipment and operating theatre time. For this reason it is often not possible to perform the surgery on the day of evaluation.

The initial step in the surgery is to open the knee joint and remove any remnants of damaged ligament. The cartilages (menisci) in the knee are also inspected as these are damaged in about 40% of dogs with cranial cruciate ligament tears. If needed, the damaged part of the cartilage is removed (meniscectomy). Attention then centres on the tibia which is cut in a very precise way to free the top section of the bone. This section can be moved to a new position that corrects for the abnormal backward slope of the tibial plateau. The bone is secured in its new position with a bone plate and screws. X-rays are taken after surgery to check that everything is satisfactory.

How successful is it?

Tibial plateau levelling osteotomy is generally very successful with the vast majority of cases improving significantly, often within 6 to 12 weeks of surgery. The osteoarthritis in the knee may still progress and cause lameness in the future and a small percentage of patients can have complications.

What can go wrong?

Tibial plateau levelling osteotomy is a very major surgery. Though it goes well in the majority of cases, there are potential complications:

The bone sometimes does not heal quite as fast as expected. Often affected dogs
do not progress as well as we would like in the first six weeks and check radiographs
at this time demonstrate the slow bone healing. These dogs usually begin to improve
in the following six weeks.
The change in shape of the knee puts additional strain on some of the structures around the knee. The body adapts ('remodels') to take account of these new strains, but this takes several months. Too much strain in the early stages after the operation can lead to damage to some of the other ligaments in the knee, failure of the implants, or even to bone fractures. This risk is especially present in the first six weeks after surgery.
Long, complex surgeries like tibial plateau levelling osteotomy have a higher risk of post-operative infection than shorter, simpler surgeries. We take every precaution to minimise this risk at the time of surgery.
The cartilages may be normal at the time of surgery, but there is an incidence of cartilage injury in the weeks and months that follow surgery (so called 'late meniscal injury'). This can sometimes account for a setback when there has been good improvement in the first few months. A further surgery can be needed to deal with the cartilage tear.

What are the logistics?

Once a dog is confirmed as a tibial plateau levelling osteotomy candidate, the surgery will
be scheduled.

Most dogs are well enough to go home within 24 hours of surgery. We supply antibiotic and painkilling drugs. Strict rest is essential in the first six weeks and we advise restriction to downstairs in the house with only the shortest possible lead walks for 'toilet breaks'. Most dogs use the leg within a few days of surgery and improve steadily thereafter. Your own vet will normally deal with stitch removal. At week six, we normally perform a re-examination and admit the dog as a day patient to obtain check radiographs under sedation or anaesthesia. We should be alerted sooner if progress is not good or if there are other complications. If all is going well at week six, we will advise short lead walks with a gradual increase in activity. We will then advise a further check about week twelve and if all is going well at this stage we will advise a gradual return to normal activity.

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