There is a movement under foot that runs counter current to the time tested principles used to position the implants in Total Knee Replacement. This principle is called Shape Matched Technology (this phrase is a trademark of Otis Med). It allows for what Otis Med terms a custom fit Total Knee Replacement.
Here is an excerpt from the Otis Med site (http://www.otismed.com) :
Shape-Match™ Technology
OtisKnee™ is based on OtisMed’s patent pending, proprietary Shape-Match™ technology. Using sophisticated 3-D software, the Shape-Match™ technique optimizes the size and placement of the Custom Fit Knee™ before surgery, based on the patient’s own normal (non-arthritic) knee anatomy. From this very precise 3-D image, custom cutting guides are created to assist the surgeon in making very accurate bone cuts that are specific to the individual patient. This allows for a “customized” implant fit and placement. Prior to the availability of Shape-Match™ technology, surgeons have relied on experience and intra-operative judgment to correctly size and place the implant in the patient. END of OTIS MED excerpt.In essence Otis Med uses MRI images of the diseased arthritic knee. The proprietary software then calculates how much of the joint surface has been lost in the arthritic knee, calculates how much to "put back" to restore the knee to it's normal, naturally given position and then provides the surgeon with custom made tools to restore the knee "back to normal". A key principle in the Otis Med technique is to restore the axis of rotation to the knee, and this can only be done by identifying the normal axis of rotation on the reconstructed MRI scans. This information is then provided to the surgeon by fabricating custom cutting blocks that are used to re sect the bone when performing an OtisKnee. This can not be accomplished with traditional Total Knee Replacement in the same manner as OtisMed, even if the surgeon uses Surgical Computer Navigation. Otis Med technique can only be used with Stryker and Biomet implants (because of the shape specific to these two brands of implants).
The debate, which is just heating up and should be spirited, will compare the merits of the totally new concept of precisely how to position the knee implants using the Otis concept, to the traditional technique of making every replaced knee straight (mechanically aligned to match a straight line running from the hip to the center of the ankle) and balancing the knee ligaments by releasing contracted ligaments and tightening stretched knee ligaments.
As I begin to analyze this radically new way to position knee implants I must say I am somewhat intrigued by the OtisMed rhetoric. Their concept places critical importance on the balance and range of motion of the knee, with axial alignment secondary (almost an after thought). Traditional technique stresses axial alignment above all else, with balance by ligament release important as well. Traditional technique, which here to for has been the dogma for positioning implants, boasts long term results with 90 % success rates 10-20 years after implantation. There are only a few peer review published articles supporting the Otis Med concept.
As they say, the jury is still out on the Otis Med principle. As a surgeon living in an ever changing, high technology world I believe I owe it to my patients, myself and my profession to study the facts for and against the Otis Med technique. Ultimately I will make an informed decision based on the best information available as whether or not to incorporate this technique into my practice of Knee Surgery.
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