Cranial Cruciate Ligament Rupture (CCL) & Tibial Plateau Levelling Osteotomy (TPLO) 

Rupture of the cranial cruciate ligament (CCL) is the most common cause of persistent hindlimb lameness in adult dogs. Certain breeds, such as Labrador retrievers, Rottweilers, Great Danes, and West Highland White terriers, are particularly prone to it, but any breed can be affected.

The cranial cruciate ligament is one of four ligaments in the dog’s stifle joint (the same as the human knee). Its job is to stop the tibia from moving too far forward or excessively internally rotating. In people, injury to the equivalent ligament, the anterior cruciate or ACL, is normally due to an accident involving excessive force, commonly a football or skiing injury. While a traumatic rupture is possible in dogs, this is a spontaneous and slowly progressive condition in most cases. The exact cause is unknown, but the canine stifle has a design flaw where the ligament is not strong enough to resist the daily forces.

In the early stages, the ligament’s tearing of a few fibres starts occurring. Some dogs will then have mild persistent lameness for months or years. Osteoarthritis develops, and affected dogs can also tear a specialised cartilage within the joint called a meniscus. In other cases, the ligament becomes progressively weaker without the dog showing any pre-existing lameness. The weakened ligament can then fully rupture, resulting in severe lameness without any apparent accident. Some dogs can appear to have ruptured the ligament accidentally when, in fact, the ligament was going to fail anyway. Sometimes, dogs spontaneously partially or fully rupture the CCL in both hindlimbs simultaneously.

The signs or symptoms of CCL rupture are very variable. Some dogs may show stiffness after rest which wears off within a few minutes. Sometimes this is simply assumed to be old age or arthritis. Other dogs show mild persistent lameness over several months. They may appear normal during short walks, but lameness and pain develops during or following more strenuous exercise. Other dogs can show severe lameness and sometimes are completely unable to use the leg. This severe lameness may or may not be preceded by period of less severe lameness or stiffness.

Some dogs can have bilateral ruptures, where the ligaments in both back legs fail at the same time. These are harder to recognise as the dogs may not limp. Owners may notice stiffness on rising, reluctance to exercise, pain after exercise, or difficulty jumping. Frequently, this is misdiagnosed as arthritis or old age.

The specific test is the cranial drawer test when the tibia is forced forward. Movement greater than normal is diagnostic for CCL rupture. This test can be painful; some dogs will not allow it without sedation or anaesthesia. In some dogs with a partial rupture, there is enough remaining ligament for this test to be negative, even when the dog suffers moderate to severe pain and lameness. Other dogs that have a slowly progressive rupture will develop joint thickening. This can make detecting an abnormal cranial drawer motion impossible despite the ligament being fully ruptured.

Radiographs (X-rays) are almost always recommended. The ruptured CCL cannot be seen on a radiograph, but joint swelling and or osteoarthritis with no other cause are strongly suggestive. Radiographs are essential to rule out other causes of lameness before proceeding with surgery, and special views are needed to plan certain surgeries, such as a tibial plateau levelling osteotomy (TPLO). Joint fluid analysis is sometimes performed to rule out infectious immune system causes of joint pain or swelling.

In some cases the diagnosis is only confirmed during surgery. The ligament can be inspected with either an arthrotomy (small incision) or arthroscopy (camera based, keyhole joint surgery). Joint inspection is also performed to assess the meniscal cartilages within the joint which frequently become torn after the CCL fails.

Some smaller breed dogs can have acceptable outcomes without surgery. The hope is that joint thickening and secondary scar tissue will stabilise the joint and effectively take over the function of the ruptured ligament. This is most effective in toy-breed dogs who do not exercise heavily.

Treatment involves strict rest for 6 – 8 weeks while the scar tissue forms. Small dogs that previously enjoyed long and strenuous walks may never return to function. Non-surgical treatment can be attempted in larger dogs, but in most cases, lameness and pain will persist. Sometimes, due to other health concerns, surgery is not possible. The severity of the pain and lameness may be reduced by long-term use of medications.

In the majority of cases, surgery is recommended. There are two main types of surgery – ligament replacement or a tibial osteotomy. Ligament replacement was one of the original methods, and there are many different types and descriptions, such as extracapsular stabilisation or a lateral suture. Newer ligament replacement techniques, such as the “Tightrope” procedure, have been developed using stronger implants. It is important to remember that in most dogs, the original ligament failed without any accidents.

Furthermore, mechanical testing shows that all current implants are weaker than the original ligament, which has already failed. For this reason, we expect all ligament replacement implants to fail, stretch, or loosen within the first few months. It is thought that the dogs that improve from this technique do so by producing scar tissue around the joint rather than the implant providing long-term stability. This approach is, therefore, unpredictable. Some dogs appear to do acceptably well, but others can have ongoing persistent lameness.

As ligament replacement has been shown to have variable results, an alternative approach is to change the biomechanics of the dog stifle (knee) such that the joint is stable during motion when no CCL is present. The tibial plateau levelling osteotomy (TPLO) was the first commonly used technique to achieve this aim. Dogs have a naturally backward-facing joint surface – the tibial plateau. The force of weight bearing causes the femur and tibia to be pushed together (open arrows). Due to the tibial plateau angle, this pushing together forces the tibia forward (solid arrow). The cranial cruciate ligament resists this force. The TPLO aims to eliminate this forces so the ligament is no longer required.

A TPLO involves making a curved bone cut (osteotomy) and rotating the top of the tibia with the joint surface. This aims to eliminate the force pushing the tibia forward during weight-bearing. The osteotomy is stabilised with a bone plate and screws.

Newer techniques, such as tibial tuberosity advancement (TTA), triple tibial osteotomy (TTO), and modified Maquet (MMT), have since been described. The TPLO is the only technique that has been shown in clinical trials to be superior to ligament replacement. Recent studies also show that TPLO has better outcomes and fewer complications than the other dynamic techniques.

The implants are strong enough to allow immediate and full weightbearing after surgery. Most dogs will be confident to use the leg well within a few days. The greatest challenge is preventing excessive use. We recommend confining the patient to a cage, pen or small room when unattended for eight weeks. Walks are limited for toilet purpose only for the first two weeks prior to gradually increasing lead walks. We perform radiography (X-rays) eight to ten weeks after surgery before giving the all clear to return to off lead exercise. While most dogs are substantially improved by this stage lameness can take up to six months to fully resolve.

We expect most dogs to make a full recovery and return to function very similar to before surgery. Osteoarthritis will slowly progress but it does not typically cause lameness or require treatment with medications.

Sometimes, TPLOs are done by a general practice (GP) vet or visiting surgeons in a GP clinic. This may be because the owner feels more comfortable having the surgery in a clinic they know. There are some advantages to full referral to our specialty hospital.

• Consultation – owners will get a chance to meet the surgeon. All our surgeons are either specialists or under specialist supervision. TPLO is a complex procedure with potential serious complications; however, these complications are rare when performed by an experienced surgeon. Using a combination of detailed history taking, patient examination and further tests if needed (joint fluid analysis, X-rays or CT), our surgeons use this experience to ensure that the diagnosis is correct and the planned treatment is the best option for the patient.
• Team approach – not every patient is simple. Commonly our surgical patients have other medical concerns. When needed we have on-site medicine and anaesthesia specialists to ensure that the entire treatment plan is as smooth, safe and stress free as possible.
• Dedicated surgical team – it’s not just about the surgeon. As a specialist surgical service our full time surgical nurses and veterinary surgical assistants are integral to ensure that optimal patient care and the best possible surgical results are achieved.
• Specialist Surgery Theatres – we have advanced surgical and anaesthesia equipment to ensure patient safety. Our surgical and anaesthesia specialists train all the team in very strict theatre protocols to reduce complications.
• Onsite specialist led emergency and critical care service. Ensuring our patients have as comfortable and as pain free an early recovery from surgery as possible is vital for good results. Many patients are hospitalised overnight with our staff being highly trained in how to help these complex surgical cases. We don’t want our patients or their fur parents to have any unnecessary distress.
• All this for a cost that is very similar to what can be charged in a non-specialist clinic.

There will always be reasons why surgery may be preferred in a local clinic, but TPLO is a major procedure that often benefits from a specialist hospital environment. Be assured that when procedures are performed at Peninsula Vet Emergency & Referral Hospital, we ensure that the referring GP is fully updated and remains an integral part of the ongoing care.