The Evolution of Knee Replacement

Orthopaedic & Spine Center
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by Robert J. Snyder, MD

The era of modern knee replacement began in the 1970’s with condylar knees.  Fixed and mobile bearing knees evolved and since then, knee replacement manufacturers have added their own proprietary changes. However, basically all mass-produced knee replacements are very similar in that they try to accommodate all patients, male and female from 100 to over 300 pounds.

To accomplish this task, all manufacturers make the knee components in different sizes and shapes.  The end result is that when a patient goes to the operation room for a knee replacement, there are multiple trays of trial components.  Often up to six or more trays may be required.  The surgeon must first replace the knee, using the trial components, until a final result is obtained.  At this point, the sales representative who is also responsible for making sure all the trial sets are complete and present for every case, goes to a storage area outside the operating room and brings back all the actual components that are in sterilized packages.  Each package is opened and placed on the sterile field.  The surgeon then removes the trial components and replaces them with the actual components.  After closing the knee, the patient leaves the operation room.

Currently the ability to manufacture custom, individual knee replacements has evolved as manufacturers have utilized newer techniques, such as 3D printers, to manufacture a customized knee along with all the customized cutting blocks and pieces required to replace a knee. They have done this while still being able to keep the cost of a customized knee comparable to a mass-produced knee, since inventory of every possible size does not need to be stored in every hospital. Trays of trial components that do not need to be made and don’t have to be available at every case.

ConforMIS has accomplished making individualized, custom knees by utilizing a CT scan of the patient’s knee, that includes part of the hip and ankle, in order to restore normal alignment.  ConforMIS can customize separate parts of the knee or an entire knee, since many patients only have severe arthritis in one or two areas of the knee.  The end result is that ConforMIS has a replacement that will fit like a glove, no matter what shape your knee.  All knees have a different curvature on the inside of the knee which is larger than the curvature on the outside of the knee.  This allows your knee to roll back during normal use and allows you to ambulate in a smooth fluid motion.  Only the ConforMIS knee builds your exact curves into the replacement knee.  The end result is that in clinical trials comparing “off-the-shelf” knees to ConforMIS knees, the ConforMIS knee moves most like a normal knee.  Also, new trials comparing the ConforMIS knee to other knees showed less blood loss, shorter operating room times and shorter hospital stays.  Long term trials are ongoing.

As an orthopedic surgeon who has had a ConforMIS partial knee, I can emphatically state my new replaced knee now works as well as my original knee did, before injuries and arthritis forced me to undergo the replacement.  This was six years ago and the knee is still going strong.  Over those six years, I have continued to be very active, even playing competitive handball three times a week.

If you have problems with your knee that might require replacing a part or all of your knee and want the latest technology available to fix the problem, visit me for a complete evaluation.  Call 757-596-1900 to schedule an appointment.