Dr. Bartlett Comments: Knee Replacement

Knee arthroplasty (any partial or total knee replacement surgery) is a major surgery because artificial components are inserted in your knee. Replacement surgery is not to be taken lightly — bridges are burned, you cannot go back to a natural knee once bone is removed and artificial parts are inserted. This is why physicians recommend medical treatments before suggesting knee replacement surgery.

As you are learning, technology is now giving us the opportunity to replace either the entire knee or selected parts. It seems intuitive that the more of your own knee you keep, the more normal your knee function will be. This is particularly true when talking about the anterior and posterior cruciate ligaments, the drivers of normal knee motion and function (kinematics). Partial knee replacements such as the unicompartmental knees (Whiteside Biomechanics Symmetric, Smith & Nephew Accuris, and MAKOplasty Restoris are the ones I use) or the bicompartmental knees (Smith & Nephew Deuce or MAKOplasty Restoris bicompartmental are the ones I use) preserve not only the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) but also the meniscus and joint surface cartilage on the normal side. These knees demonstrate near normal kinematics. Total knee replacement involves removing the anterior cruciate ligament (ACL) and removing or severely compromising the posterior cruciate ligament (PCL) and knee kinematics are very abnormal. This is why I encourage partial knee replacement whenever possible.

Each of the 3 unicompartmental knees I use replaces only one knee compartment. I have performed unicompartmental knee replacements for over 25 years and find they provide the best knee replacement; they are better than total knee replacement especially in terms of motion achieved after surgery. The Whiteside Biomechanics Symmetric and the Smith & Nephew Accuris are performed using traditional open surgery techniques (larger incision and more surgery than with MAKOplasty). The Symmetric knee is a press fit, bone in-growth, non-cemented implant. The Accuris implant requires cement for fixation (read more about these differences in the section called Materials and Techniques). The MAKOplasty Restoris is performed using a very new and innovative interactive robotic arm with computer navigation. With this technique, the incision is smaller requiring less surgery. The computer increases surgical accuracy and the robotic arm, by minimizing the surgery, reduces post operative pain and speeds recovery. The Mako Restoris implant requires cement for fixation.

When arthritis is severe and involves all compartments of the knee, or when there is a severe deformity, total knee replacement (I use Smith & Nephew Profix) is the surgical treatment of choice. Significant reduction in pain (not always complete reduction of pain) can be expected. Function is adequate for every day activities and light sports. Motion is not normal (national average is flexion to only 115 degrees) and you cannot kneel. Kinematics are severely distorted. The knee does not really feel normal. But, if required, it is an excellent option. Rarely do I see patients who regret undergoing total knee replacement. Total knee replacement remains the “gold standard” by which all other knee arthroplasties are judged.

Artificial components can wear out. Today, implants last about 15 years. When they do eventually wear out the polyethylene (plastic) has usually worn or the cement has loosened. Revision surgery is required. Implants can, of course, wear out faster. There are many factors involved in predicting implant failure among which are the following: your personal lower extremity alignment, your activity level, subsequent knee injuries, alignment achieved at surgery, the presence of cement, and the thickness of the polyethylene.

Materials and technique (computer navigation and robotics) improve yearly constantly increasing implant longevity.

I would again emphasize that all forms of non-surgical treatment should be exhausted before proceeding with knee replacement surgery as there is no turning back once artificial components are inserted.