CRUCIATE LIGAMENT TEAR
Cranial cruciate ligament tears are the most common orthopaedic injury in people (ACL) and in dogs (CCL). The cranial cruciate ligament sits inside the knee joint and stops the shin bone (tibia) sliding forward in relation to the thigh bone (femur). When the ligament tears there is a cranial drawer (forwards and backwards sliding) between these bones. It is this movement which causes dogs pain and persistent limping. The degree of movement is related to the amount of tearing of the ligament and the angle of the articulating surface of the shin bone, called the tibial plateau angle. The steeper the angle the more forces are acting on the knee.
Unfortunately, approximately 50% of patients that tear one cranial cruciate ligament are at risk of tearing the other ligament at some point in the future and the goal is to return patients to normal weight bearing as soon as possible to reduce the strain on the remaining knee and ligament.
Approximately 30% of patients that present for tears of the cranial cruciate ligament will injure the meniscus, which are the knees shock-absorbers. If the meniscus are injured at the time of surgery then the damaged portion is removed, whilst in patients that do not have a tears the meniscus is left intact as it is important to joint function. There is however an approximately 10% risk of an injury to the meniscus at a later date. This generally appears as a patient that has recovered well from surgery and then starts to limp on the leg, generally 1-6 months later. Should this occur then re-examination would be advised, and this may be treated by either arthroscopic or open surgical removal of the damaged meniscus, with quick recoveries and outcomes.
Without stabilisation of the cranial drawer movement, pain and discomfort will persist, it may slightly improve with rest but will again become painful with activity. Osteoarthritis will progress without intervention and surgery.
There are many different techniques which have been used to stabilise the dogs knee following tearing of the cranial cruciate ligament over the years, although broadly speaking there are 2 main groups. Group 1 changes the weight bearing forces through the knee, by cutting and rotating the shin bone, so that the patient is able to bear weight without the need for a cranial cruciate ligament (TPLO, TTO, CWO, TTA). Group 2 attempts to mimic what the cruciate ligament does using sutures (DeAngelis Suture, Isometric Sutures).
Ideally, the larger the patient or those with a steep angle inside the knee benefit from the surgeries in Group 1, whilst smaller dogs may cope with the surgeries from Group 2.
Advanced Veterinary Surgery uses a Tibial Plateau Levelling Osteotomy (TLPO) in larger dogs or Cranial Wedge Osteotomy (CWO) in smaller dogs to alter the angle of the articulating surface of the shin bone to be more perperdicular to the downward force through the leg. The benefit of these procedures is that it allows earlier return to function, and also less osteoarthritic changes as determined by xrays later in life, compared to the 'suture techniques'. This group of techniques is the current gold-standard for cranial cruciate ligament injury in dogs. Following surgery it is expected that over 90% of patients will have a good to excellent outcome.
Advanced Veterinary Surgery uses Synthes Locking TPLO plates which minimise complications compared to standard plates.
The suture techniques may be used in patients who have a smaller body weight and relatively shallow angles within the knee joint, or where finances do not allow stabilisation using the bone cut techniques. Advanced Veterinary Surgery uses surgical nylon to perform either DeAngelis Suture or Isometric Suture placement.
Complications rates fortunately are very low, with the most common complications being infection (2-4%), usually only requiring antibiotics additional to the ones dispensed at the time of surgery. A smaller number of cases where the joint or plates are infected, require flushing of the joint or removal of the plates via a short simple procedure. Generally the implants never need to be removed and cause no problems.
The choice of technique chosen to stabilise the cranial cruciate ligament tear in your best friend can be discussed with your regular veterinarian and in consultation with the surgeons at Advanced Veterinary Surgery, and based on the best possible outcome for you and the patient in mind.