The anterior cruciate ligament is one of the stabilizing ligaments of the stifle (knee). You may have heard of the anterior cruciate ligament before – probably when an AFL footballer has torn his and requires surgery!

Dogs and occasionally cats can tear their cruciate ligaments as well. This can occur as a sudden acute injury or as a consequence of long term weakening of the ligaments in the joint. Sometimes weight can play a role – being overweight can increase the risk of this injury.

The first graphic shows the structure of the canine stifle with the original ligament indicated and a superimposed blue "prosthetic ligament" sutured in place. This represents the De Angelis technique for stifle stabilisation following anterior cruciate ligament rupture. This technique is well suited to small dogs and cats and a modified version of the technique can even be used with good success in larger breeds as well.

In this case our patient was a very overweight cat. In the photograph you can see the cat being prepared for surgery (See image). The leg is shaved, surgically scrubbed and draped to prevent contamination of the surgery site.

Repairing the original ligament is not practical because of its position deep within the joint and the fact that it is only a very short ligament (less than a centimetre long). The De Angelis technique is used whereby an artificial ligament (in this case a nylon-like suture material similar to fishing line) is anchored above and behind the stifle and pulled tightly across the lateral aspect of the joint to attach in front and below the joint, just below the patella (knee cap).

In the next photo you can see the suture material being tied behind one of the anchorage points. Sometimes a special crimp or clip is used to ensure a secure union in the artificial ligament is achieved.

This technique is relatively simple and effective in stabilising the joint with the artificial ligament mimicking the action of the original ligament. However, full strength in the joint occurs gradually over a long period of time as the body produces its own fibrous reaction around the artificial ligament. For this reason good confinement for a period after surgery is necessary to minimise the risk of tearing the new ligament or damaging the cruciate ligament on the other leg.

Pain relief is given at the time of surgery and for a week or so post-operatively. The leg is generally left unbandaged. Sutures are removed after 10-14 days and we normally see return of function in the leg over several weeks.

Unfortunately, the underlying ligament weakness which has led to a tearing injury in one anterior cruciate ligament generally means there will be some weakness in the other anterior cruciate ligament as well and so it is fairly common for the injury to occur in the other leg at some point down the track. To help prevent this, weight reduction is generally recommended if the patient was overweight to start with. An exercise program that involves regular moderate exercise but less jumping and turning (ie no more vigorous retrieving and ball-catching) is also recommend to help reduce the risk of the injury occurring in the other leg (or re-occurring in the same leg!)