Rupture of the cranial cruciate ligament in the knee joint is a very common injury which causes significant joint instability, lameness and if left untreated leads to crippling arthritis. There are several options for surgical repair and at The Vet Centre we keep ourselves up to date with the most recent repair techniques. We are the only veterinary practice in Marlborough to offer the very successful techniques of Triple Tibial Osteotomy (TTO) and the Modified Maquet Procedures (MMP).
There are two cruciate ligaments within the knee joint, a cranial ligament and a caudal ligament. Together these ligaments stabilise the knee joint, preventing backwards and forwards motion of the two leg bones (femur and tibia) relative to each other at the knee joint. If one of these ligaments ruptures the knee joint becomes unstable and the bones rub backwards and forwards against each other causing pain, lameness and erosion of the cartilage and other structures within the knee joint. The cranial cruciate ligament (CCL) is the more important of the two ligaments as it bears the most load during normal activity. It is the CCL that ruptures most commonly.
There are several reasons why the CCL might rupture. Young athletic dogs can suddenly rupture the ligament if they take a bad step or make a bad turn during play. This causes a sudden lameness. We often see this injury in active working dogs.
Another situation is in older large breed dogs, especially those that are overweight. These dogs may have chronically weakened ligaments and the ligaments may progressively stretch over time. In this situation the ligament may partially tear causing a chronic waxing and waning lameness. This partially torn ligament may then suddenly rupture at any time even if the dog is not doing anything particularly active. As the ligaments in both knees are likely to be chronically weakened it is common in this situation for both knees to have a cruciate injury during the animal’s life.
There is a genetic component in that certain breeds are more likely to develop chronically weakened cruciate ligaments. Those breeds at higher risk include: Neopolitan mastiff, Newfoundland, Akita, St. Bernard, Rottweiler, Chesapeake Bay Retriever and Staffordshire Bull Terrier.
Diagnosis of CCL Rupture
If the ligament has completely ruptured it is possible to feel the backwards and forwards motion of the tibia relative to the femur at the knee joint. If there is a partial tear then diagnosis can be more difficult. Usually sedation is needed to accurately assess the knee joint. Often with chronic cruciate injuries or partial tears there will be thickening of the knee joint and pain when manipulating the knee. X-rays of the knee may show an increase in the volume of joint fluid and arthritic changes within and around the joint. A combination of palpation of the joint and taking X-rays usually allows accurate diagnosis of cruciate injury although sometimes exploratory surgery of the knee joint is needed to confirm the diagnosis.
There have been many different techniques used over the years for CCL repair. Some are now no longer used and others have been extensively modified in the search for the ideal repair method. The aim of cruciate repair is to regain mobility with little or no ongoing lameness and to offset the time of development of arthritis. The best repair method will depend on the situation of each individual animal. Traditional methods involve replacement of the ligament with surgical implants such as pieces of nylon or strips of connective tissue. Newer techniques involve surgically altering the whole biomechanics of the knee joint so that the cruciate ligament is no longer needed.
This is our newest procedure and is suitable for any size of dog. This technique alters the biomechanics of the knee joint so that a CCL is no longer needed. This is achieved by cutting the bone on the front of the tibia and advancing the tibial tuberosity forwards by insertion of a titanium foam wedge. A metal staple and pin are used to hold the wedge and bone in position. Advancement of the tibial tuberosity results in a backwards force on the tibia which stabilises the knee joint without the need for an intact CCL. MMP surgery is quicker and less technically challenging than TTO surgery yet has an equally successful outcome. As MMP is less invasive, involving less surgical trauma to the bone and soft tissues of the knee compared to TTO surgery, there is less post-operative pain and the speed of recovery is quicker following MMP. As surgical time is quicker the cost of MMP surgery is less than that of TTO. MMP has become our surgical technique of choice for cruciate ligament injury.
With the foam wedge in place, a stainless steel Kirshner wire is advanced through a hole in the Orthofoam wedge until fimly seated in the tibia bone on the opposite side
Pointed bone reduction forceps are used to compress the wedge while a staple is tapped in to pre-drilled holes to help provide stability of the surgical repair from day 1
This technique is a relatively new approach to CCL injury and is generally only used in larger breed dogs. Like MMP, it does not repair the ligament as such but alters the whole biomechanics of the knee joint so that a CCL is no longer needed. The knee joint is stabilised by the action of actively contracting muscles. The purpose of developing this technique was to improve the success rate in treating cruciate rupture in large breed dogs where failure of nylon implants is more likely than in smaller animals.
There are a variety of techniques available to alter knee joint mechanics and the TTO combines two of the most successful techniques, the TPLO (tibial plateau levelling osteotomy) and TTA (tibial tuberosity advancement). In the normal knee joint the slope on the top surface of the tibia results in a lot of load bearing force being exerted onto the CCL. If the ligament is ruptured this force causes the tibia to move forwards. If the top surface of the tibia is made level then there is no force to move the tibia forwards and so the knee joint remains stable despite having no CCL.
To achieve a level tibial plateau three cuts are made in the tibia and a wedge of bone is removed. The cut ends of bone are compressed together which alters the angle of the top of the tibia and at the same time moves the front edge of the tibia further forwards. The bone is then held in its new position with a special ‘T’ shaped bone plate. This technique is technically difficult and requires investment in special instruments to make accurate cuts in the bone. The Vet Centre has invested in the necessary equipment and expertise and has been successfully performing this surgery since 2006.
Excellent results have been achieved with this technique, with more rapid recovery times, less progression of arthritis and return to athletic function in large breed dogs.