What Are Partial Knee Replacements?
Usually, osteoarthritis of the Knee involves the entire joint, and a Total Knee Replacement is the treatment of choice. Perhaps one in ten people with knee osteoarthritis with severe enough involvement of the joint to consider surgery are fortunate enough to have the arthritis limited to only one compartment of the knee. In this case Makoplasty partial knee replacement is the best surgical choice. The knee has 3 compartments (think of the knee as a 3 room home). When just one compartment has all the articular cartilage or joint surface damaged (one bad room, two good room) partial knee replacement is done. This is also known as unicompartmental knee replacement (uni) if the medial or lateral compartment between the femur and tibia (thigh and shin bone) is replaced or patellofemoral replacement if the joint between the femur and patella (thigh and knee cap bone) is replaced.
Unicompartmental knee replacements function better than total knee replacements because less of the normal anatomy is disturbed ( no knee ligaments removed, less bone removed) and the uni knee bends, straightens and rotates more naturally. Recover after unicompartmental knee replacement is quicker and the postoperative pain is less compared to total knee replacement.
Longevity of a unicompartmental knee is very good, with nine in ten uni’s working well at 10 years after surgery and many functioning well 20 years after surgery. The most common cause of failure after uni knee replacement is advancing arthritis in one or both of the previously uninvolved compartments of the knee.
Here is an excerpt of an article in the Arizona Republic about one of my patients in whom I performed partial knee replacement in one knee, then 3 months later the other knee. This is an example of how well partial knee replacements function. Outcomes like this is why I wanted to practice medicine.
“After suffering for years with knee damage that limited her mobility, Sarah Panepinto does not take dancing with her husband or playing tag with her kids for granted.
Last year, the 41-year-old Gilbert mother of five children had partial knee-replacement surgery on both of her knees. Since then, Panepinto said her recovery has been a miracle.
I can dance. I’m speed-walking. And I can even play Dance, Dance, Revolution with my kids,” Panepinto said.
The more active lifestyle is a blessing for Panepinto who needs the energy to keep up with the home-schooling of her two teens and two elementary school-age kids.
I’m off anti-depressants . . . I feel like I have my life back,” said Panepinto who has suffered from knee problems since she was 12.”
Patient Selection Crucial
20 year survival rates of unicompartmental knee replacement approach 75 % or better. Implant design and Makoplasty surgical technique (robot technology) are important contributing factors.
Berlin surgeons performed a medical study evaluating 5 year survival of German patients from 2006 to 2012. This was published in the JBJS in October of 2016.
Risk factors associated with failure of the implant in the first 5 years after implantation are:
1. age younger than 55
2. Obesity (BMI > 30)
3. Diabetes, complicated
5. Low volume facility (less than 10 cases per year)
Leo McNellis says
Please tell me whether complete our severe joint space narrowing is a prerequisite for the partial knee replacement procedure. I have severe osteoarthritis on the medial femoral and tibial head of my left knee, but I have only a very slight joint space narrowing of that compartment. I have had two arthroscopic surgeries for this condition in the last six months because of pain in that area. My lateral compartment is healthy. Have any orthopedic surgeons that you know ever done a PKR for a patient with minimal joint space narrowing?
Stefan D. Tarlow MD says
It would be important to understand if the xrays were weight bearing films, including both Standing AP and Standing 40 PA views. Severe xray narrowing is one of the surgical indications for joint replacement surgery. Outcomes following surgery are less successful when indications are ignored.
Stefan D. Tarlow MD says
Leo, severe joint space narrowing on xray is a prerequisite for joint replacement surgery.
Millie Hue says
Thanks for helping me understand that the possibility of having issues with your knees again after the surgery will only happen if arthritis progressed. That just means that the procedure will be effective once my mom undergoes this. She just needs it because she might not be able to walk properly again if she does not get it replaced. Now, she is already having mobility issues because of it, and I had t help her stand up all the time.