CRANIAL CRUCIATE LIGAMENTS
What exactly is a cranial cruciate ligament?
In dogs, the cranial cruciate ligament (CrCL) is equivalent to the “anterior” cruciate ligament (ACL) in humans. It is a tough fibrous tissue band that connects the femur (thigh bone) to the tibia (shin bone), preventing the tibia from moving forward relative to the femur. It also helps to keep the stifle (knee) joint from rotating or overextending.
In humans, trauma to the equivalent ligament is common, and damage most commonly occurs during some form of sporting activity (including football, rugby and golf).
In dogs, cranial cruciate ligament disease is very different. Rather than breaking suddenly as a result of excessive trauma, the ligament usually degenerates slowly over time, much like a fraying rope. This significant difference is the primary reason why the treatment options for cruciate ligament injury in dogs differ so greatly from those recommended for humans.
What causes cruciate ligament injury in dogs?
The cranial cruciate ligament (CrCL) ruptures in the vast majority of dogs as a result of long-term degeneration, in which the ligament’s fibers weaken over time. We don’t know why this is happening, but genetic factors are most likely to blame, with certain breeds predisposed (including Labradors, Rottweilers, Boxers, West Highland White Terriers and Newfoundlands).
The assessment of family lines, combined with the knowledge that many animals will rupture the CrCL in both knees, often relatively early in life, provided the primary evidence for a genetic cause. Other factors such as obesity, individual conformation, hormonal imbalance, and certain joint inflammatory conditions may also play a role.
What causes cruciate ligament injury in dogs?
The cranial cruciate ligament (CrCL) ruptures in the vast majority of dogs as a result of long-term degeneration, in which the ligament’s fibers weaken over time. We don’t know why this is happening, but genetic factors are most likely to blame, with certain breeds predisposed (including Labradors, Rottweilers, Boxers, West Highland White Terriers and Newfoundlands).
The assessment of family lines, combined with the knowledge that many animals will rupture the CrCL in both knees, often relatively early in life, provided the primary evidence for a genetic cause. Other factors such as obesity, individual conformation, hormonal imbalance, and certain joint inflammatory conditions may also play a role.
What are the symptoms of cruciate ligament disease in dogs?
Limping is the most common symptom of CrCL injury. In some dogs, this may appear suddenly during or after exercise, while in others, it may be gradual and intermittent. Some dogs are affected in both knees at the same time, and these dogs frequently have difficulty rising from a prone position and have a very “pottery” gait. In severe cases, dogs are unable to stand and are mistakenly suspected of having a neurological problem.
What is going on inside a swollen joint?
The tearing of the ligament sets off a chain of events that results in knee pain and lameness. Osteoarthritis is already present in the early stages. It’s critical to accept this because many people wonder, “When will my dog get osteoarthritis?” when the dog already has it. The CrCL loses its normal mechanical function at a critical point of fraying, and painful lameness is accompanied by mechanical lameness. One of the factors influencing mechanical lameness at this point is the shape of the top of the tibia (shin bone), which has a pronounced backwards slope in dogs. In dogs with an incompetent CrCL, this slope causes the femur to roll down the slope every time weight is applied to the leg. This slope will only become a problem in dogs without CrCL impairment if it is extremely steep and can predispose to CrCL problems.
The mechanical deficiency in some dogs can result in trauma to other structures within the joint, specifically a pair of buffer cartilages known as menisci. The femur can crush and tear these cartilages as it slides down the slope of the top of the tibia, particularly the one on the inside (medial aspect) of the joint.
What are the symptoms of cranial cruciate ligament injury?
In dogs with complete CrCL rupture, the diagnosis is usually based on an examination by an experienced orthopedic surgeon, with specific knee manipulations demonstrating joint laxity. Other tests, such as radiography (x-rays) or MRI scans, may be required in dogs with partial tears or early degeneration of the ligament. Radiographs must be of the highest quality to be of maximum benefit. In most cases, exploratory surgery or arthroscopy (keyhole surgery) is used to confirm the diagnosis and look for cartilage tears or other problems.
Non-surgical treatment and Surgical treatment
Non-surgical treatment
Non-surgical management is rarely advised, unless the risks of a general anesthetic or surgery are deemed excessive (e.g. patients with severe heart disease, uncontrolled hormonal disorders or immune conditions, etc.). Bodyweight management, physiotherapy, exercise modification, and medication are the foundations of non-surgical treatment (anti-inflammatory painkillers). These same techniques are also useful in the short-term management of surgically treated dogs, even though the primary surgical goal is to reduce the need for long-term exercise restriction and medication. Non-surgical treatment has a very low chance of restoring clinical normalcy in dogs weighing more than 15kg. Dogs and cats weighing less than 15kg have a better chance, though recovery usually takes several months and is rarely complete.
Fitzpatrick Referrals can provide you and your dog with a cruciate ligament disease rehabilitation plan. This is coordinated by our rehabilitation service, which includes a team of chartered physiotherapists and hydro therapists who are all well-versed in the treatment of cruciate ligament disease. Your orthopedic clinician will schedule an appointment with one of our chartered physiotherapists, who will perform a thorough clinical examination and create a rehabilitation plan specifically for your dog, including a home exercise plan for you to follow at home. Most appointments are out-patient, and your chartered physiotherapist will regularly evaluate your dog’s progress and, if necessary, modify your home exercise plan.
Surgical treatment
Surgical treatments are classified as either replacing the deficient ligament or rendering the ligament redundant by cutting the tibia and realigning the forces acting on the stifle joint.
Techniques for replacing ligaments
For more than five centuries, various surgical techniques that mimic the procedures used for ligament replacement in humans have been used. Techniques that use transfer of local tissues have the lowest chance of returning limb function to near normal or normal in dogs. This is most likely due to the replacement tissues being less robust than the original ligament and being placed in the same unfavorable biomechanical environment that caused the original ligament to fail in the first place.
For many years, prosthetic ligament replacement techniques have also been used. These are simple techniques that can restore many animals to near-normal function. The main drawbacks of these techniques are their unpredictability in the early stages of recovery and mechanical limitations in large and athletic dogs. Some dogs become temporarily lamer before improving. Others will take several weeks to recover, and some will have ongoing knee instability and pain. Variations of this technique are most commonly recommended for dogs with traumatic cruciate ligament injuries and in animals with multiple knee stabilizers damaged (so-called “multiligamenous injuries”).
Sutures made of nylon with various knotting and crimping systems have been used for decades to connect a bone at the back of the femur (the flabella) and a tunnel in the top of the tibia. The reported success rates for these so-called flabella tibia tuberosity sutures have varied depending on material and technique. The most important aspect of this technique is that the ligament origin on the femur and insertion on the tibia are as isometric as possible, staying as close to the same length in flexion and extension as possible. In reality, this is impossible and so the principle has been referred to as “quasi-isometri “TightRopeTM” technique, which uses a synthetic material called FibretapeTM or Fib rewire TM on metallic anchors placed through bone tunnels in the femur and tibia, has a high success rate. This is the most commonly used technique in patients who require ligamentous replacement.
Treatments that eliminate the need for the cranial cruciate ligament
These procedures change the geometry of the affected knee joint so that the CrCL is no longer required to maintain stability. There are several techniques, all of which involve reshaping the top of the shin (tibia) by cutting the bone and repositioning it. The tibia plateau levelling osteotomy (TPLO) technique is available at Fitzpatrick Referrals.
Leveling of the tibia plateau osteotomy (TPLO)
This surgery entails making a radial cut in the top of the tibia and rotating the plateau segment until the previous bone slope is no longer present. A bone plate and screws are then used to secure the bone in its new position.
Tibia tuberosity progression (TTA)
The procedure is similar to TPLO in that a cut is made in the tibia to allow for a change in geometry that renders the CrCL redundant. The mathematical principles underlying TTA are more complex than those underlying TPLO; however, the basic principle is that an altered direction of traction from the quadriceps muscle group produces a force across the knee joint that counteracts the femur’s tendency to roll down the slope of the tibia plateau. TTA and TPLO both aim to make the tibia plateau perpendicular to the straight patellar tendon, thereby neutralizing the tendency for the femur to slip down the tibia slope.
What are the TPLO and TTA success rates?
Over 90% of dogs return to normal activity following TPLO or TTA. This usually means that the dogs are so normal that their owners are unable to detect lameness in their dogs at home. We anticipate that dogs will be able to resume unrestricted exercise without the need for ongoing medications. After these surgeries, performance dogs such as sniffer dogs and military patrol dogs are expected to return to work. The success rates of TPLO and TTA are nearly identical. At Fitzpatrick Referrals, we routinely use kinetic gait analysis, which involves walking the dog on a force plate, to provide objective parameters on how a dog walks both before and after surgery.
Risks or complications of cruciate ligament repair surgery?
Fortunately, when experienced surgeons perform cruciate ligament repair surgery, complication rates are low. Infection and mechanical complications are the two most common complications. Antibiotics are used to treat infections. In some cases, surgical irrigation is required, and in the worst-case scenario, where bacteria adhere to the implants, the implants must be removed once the bones have healed. The implants are permanent in the vast majority of animals and cause no problems. Mechanical complications are common in dogs who exercise excessively before their bones have healed (which takes about 6 weeks). Many mechanical complications can be treated with rest alone, but some require surgical revision. A rare complication of late meniscal (buffer cartilage) injury within the operated knee joint may necessitate keyhole surgery. Other uncommon complications, such as sprains and strains around the knee joint, can usually be treated with physiotherapy alone. Fitzpatrick Referrals has published a large case series of TPLO surgeries with very low complication rates and very few requiring follow-up care.
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