Pet Illnesses

Anterior cruciate ligament damage

The cruciate ligaments get their name from "Cross (Crus)".

They are composed of two ligaments that form a cross inside the knee (stifle) joint. They are called the cranial and caudal cruciate ligaments. By forming a cross in line with the front and back of the stifle, they prevent excessive forward and backward movement in the joint.

Active dogs, like active human sportspeople, can sometime rupture one of these ligaments, usually the cranial cruciate ligament. As a result, there is excessive forward to backward movement in the stifle. This leads to the cartilage damage as the bones crunch into each other. Before long, there is arthritis and continual pain.

Some dogs have been born with bad hind leg conformation. The plateau of bone on top of the tibia (the bone between the stifle and ankle) is sloped too far in a forward and downward direction. The average tibial plateau slope in dogs with ruptured cruciates is 24 degrees.

The tibial plateau should be roughly parallel with the ground. This places excessive strain on the anterior cruciate ligament ,and it's not long before it ruptures. These dogs need to have a special operation to repair it (see TWO below)

Ortho tpo 1After surgery, the tibial plateau is approx. 7 degrees

 





 

Normal appearance of a stifle joint viewed from the frontAppearance of a ruptured cruciate ligament

 






Treatment

Surgery is usually required before arthritis develops. The sooner it is performed , the better the outcome. There are several types of operations used.

De-Angelo's de-rotation technic

This involves placing thick nylon (something similar to fishing line used to catch marlin with) inside the joint in roughly the same position as the ruptured anterior cruciate ligament. That way, it performs similar stabilising effects in the stifle as a normal anterior cruciate ligament. This technic is used quite widely in veterinary surgery.

Four-in-one over the top technic

This is very similar to the technic used in humans. It involves taking a long strip of tough tissue from the side of the stifle, and threading it through the joint in the same direction as the ruptured ligament.

Tibial wedge osteotomy (TPO) levelling technique

This is the best approach for medium to large dogs and for dogs with malformed legs that caused the ligament to rupture in the first place.

By taking x-rays of the hind leg, a specialist surgeon can determine the size of a wedge of bone to remove from the mid shaft of the tibia (the bone between the stifle and ankle). Once the wedge is taken out, the tibia is "stuck back together" using a metal plate and screws. The effect is to make the plateau of bone on top of the tibia roughly parallel to the floor. This stabilises the joint and prevents foreword movement of the joint.

Tibial crest advancement

A new approach being used by some specialists is to loosen the tibial crest (the piece of bone which the patella/kneecap tendon attaches to) and move it forward towards the nose. A special device/spacer is placed between the tibial crest and where it used to be attached. Overall, the joint is more stable and the procedure is less invasive than other techniques.

See also...
ACL Surgery case