Cranial (anterior) cruciate ligament rupture (in the knee/stifle joint) is the most common orthopedic problem in the dog and is being seen with increasing frequency in the cat. It is also seen commonly in human sport injuries e.g. skiing or football. In pets, the majority of cases (at least 75%) are due to a degenerative condition within the stifle (knee) joint. Some cases of ACL ruptures can be secondary to trauma though. Factors that may contribute include genetics, obesity and aging. Dogs commonly affected include Labradors, Golden Retrievers, Rottweilers, St Bernards, Newfoundlands and Bichon Frise. Up to 40% of dogs will end up tearing the ligament in the other knee also.
Often palpating/feeling the joint (normally under sedation as sore for dog and muscles less tense) can reveal instability, pain, swelling and/or joint thickening. A "click" may also be discovered when bending the knee, which may indicate a concurrent meniscal tear (little cartilage cushions acting as shock absorbers in the joint) which is common in up to 50% of stifles with an ACL rupture.
X-rays may also be useful to help assess the knee. They may reveal osteoarthritic changes (new bony changes), swelling of the joint and the calcification of the broken ends of the ligament.
Pain and lameness may result from the degenerative condition of the ligament itself even before it has ruptured. There may be chronic inflammation long before any instability can be detected in the joint. In the early stages, tears of the ligament may be only partial. Without surgical treatment, it is thought that virtually all of these partial tears will progress to a complete rupture of the ligament. Once the ligament has completely ruptured, the inflammation is more acute and painful and the joint will be unstable. Pain and lameness may also be exacerbated by a meniscal tear.
Surgery will help to both stabilise the knee and allow for surgical exploration of the joint (to remove any damaged menisci).
For reference, there are many different surgical techniques. This suggests in itself that no surgery has convincingly proven superior to others. The most commonly used procedures today include:
Extracapsular technique - where a strong implant (like fishing wire) is used to stabilise the joint (mimicking the position of the torn ligament). Eventually, with time, the implant will fail but by the time this usually happens, enough fibrous tissue has formed and/or sufficient muscle rehabilitation developed to support the joint.
Tibial plateau levelling osteotomy (TPLO), tibial tuberosity advancement (TTA) and equivalent techniques- Complex surgeries whereby the slope of tibial plateau (top of shin bone) is altered to avoid the need of a cruciate ligament anymore. These surgeries are associated with better results and less degenerative joint disease in larger dogs. However, they are more expensive and have higher rates of significant complications.
Animals are often treated according to their size. Any dog or cat is a candidate for surgery but the following guidelines may be used:
Smaller than 7 kg: Conservative treatment (cage rest, pain killers and weight control) commonly return to normal by 4-6 weeks If not, surgery should be considered.
7-20kg: Surgery advisable by any of the techniques mentioned
20kg+: Surgery advisable. Extracapsular technique may produce good result but is prone to failure (and progression of arthritis). TPLO and TTA probably better options.
Painkillers may include non-steroidal anti inflammatory drugs (NSAIDs like aspirin, meloxicam, carprofen) or opiates (like tramadol). Weight control is very important. Other medication may include pentosan polysulphate injections (weekly for 4 weeks) preventing cartilage breakdown and also supplements (like glucosamine and chondroitan sulphate) which help to improve joint fluid and cartilage healing.
Posts
No comments:
Post a Comment