Knee Arthritis: Total Knee Replacement Animation

Knee Arthritis: Total Knee Replacement Animation

A total knee arthroplasty, or total knee replacement, starts with creating a tunnel through the shaft of the thighbone, or femur. This is so the first cutting guide can be placed in line with the bone. The first cut takes the damaged cartilage off the very end of the bone.

This next guide helps the surgeon choose the correct size cutting block to remove the rest of the damaged cartilage. The final metal implants do not attach to any cartilage, so the surgeon must remove a little bone as well to make sure there is a clean surface. This cutting block is secured with pins and several cuts are made to remove all the cartilage. The skinny slots in the cutting block help the saw blade stay straight. One final hole is drilled, and the end of the thighbone is prepared.

Next, the surgeon will prepare the top of the shin bone or tibia. A long guide is placed on the front of the shin, and the surgeon will line up the cutting block surface along the top of the shin. They will measure how much bone they are removing along with the damaged cartilage. Using the saw, the damaged cartilage from the top of the shin is removed, and the surgeon will check how much room is between the thigh bone and shin bone when the knee is straight and when it is bent.

Next, trial components are used to double-check the size of the final implants. A metal component goes on the end of the femur, a metal tray on top of the tibia, and a plastic insert between them. When the surgeon decides on the correct size, a hole is drilled into each condyle of the bone. The top of the tibia is then prepared by creating a large hole with a slot on either side. This is the same shape as the large keel and fins on the bottom of the final implant, which will be seen momentarily.

The kneecap is the last bone to prepare. The entire cartilage surface is removed with one cut. Three small holes are drilled, and a trial kneecap is placed to make sure the fit is right. Once the surgeon is confident all the sizes are correct, all of the trials are removed, and the final implants are prepared.

A special bone cement is placed on the bone and the back of the metal component for the shin bone. See the large keel that will be placed into the bone. It is lined up and tapped into place. The steps are repeated for the component for the thigh bone. Notice the pegs that fit into the holes that were drilled. The kneecap is replaced with plastic; that way there is not metal rubbing on metal in the knee.

Last but not least, the final plastic insert is placed between the metal piece on the thigh and the metal piece on top of the shin, and the total knee replacement is done.