Well, athletes (we are all athletes if we are exercising towards a goal) this is the 3rd and final “aching knees” blog. Over the last 2 weeks we have covered what you can do for yourself and what your doctor can do for you in the office. When conservative (non-operative) measures do not relieve the pain and swelling of damaged knee cartilage, there are several techniques for cartilage repair. It is time to have a discussion with your Orthopedic Surgeon.
One method for filling in lost cartilage, or what feels like a pothole in your knee, is called microfracture. When this technique is successful, the hole in your cartilage is replaced with scar cartilage. This replacement cartilage, called Fibrocartilage, fills in the gap in your native knee surface.
The microfracture technique essentially uses your body's own blood stem cells (cells that can become any cell) to grow the scar cartilage. The stem cells get to the hole in your cartilage through small holes your surgeon makes (microfractures) in the bone underlying the bad spot in your cartilage.
Microfracture is normally performed by first examining your knee with an arthroscope (camera). The area of cartilage loss is prepared and small holes are poked in the bone to allow the bone marrow containing stem cells to fill the “pothole” and form scar.
This procedure is appropriate for cartilage holes smaller than 2 centimeters and works best for younger people. If the procedure works, 80% of patients report good to excellent results even 11 years out. If the procedure does not work, it does not burn any bridges for future cartilage procedures.
The next cartilage "fix" is called OATS. No, we are not talking about multi-grains here. OATS stands for Osteoarticular Transplant System. Essentially, we take plugs of cartilage and bone from a non-weight bearing part of the knee and transfer it to the area of cartilage that does bear weight. The beauty of this procedure is that we transfer healthy "hyaline" cartilage instead of the fibro-cartilage that grows after microfracture.
We have instruments that literally take a plug of cartilage and bone out and then transfer the whole block to the new site and tap the plug in. This technique works best in small cartilage holes in the femur (thigh bone) and less well in the tibia (shin bone). It is not a great solution for the knee cap.
Multiple plugs can be used in the same cartilage hole. When this is done it is called Mosaicplasty. The outcomes of the OATS procedure seem to work best in knees that are less than 50 years old.
Again, as with microfracture, the rehab from this procedure is long, with 6 weeks on limited weight bearing and 3 to 6 months of rehabilitation prior to returning to all out sports. The purpose of this procedure is to provide pain relief and improve function when a knee replacement is not warranted.
Cartilage care is getting more and more high-tech, and armies of scientists and clinicians are working to solve the dilemma of worn out knees. A sophisticated way to get the body to work for itself is called ACI, or Autogenous Cartilage Implantation. This procedure does not use whole plugs of tissue like OATS, but instead uses your own cells to grow new cartilage.
ACI is used for cartilage holes measuring 2 to 10 square centimeters and for people aged 15 to 55. ACI requires 2 surgeries. In the first surgery, the doctor arthroscopically harvests small amounts of your healthy cartilage and evaluates whether the hole in your cartilage is a good candidate for ACI. The harvested cartilage is sent to a commercial lab where the cartilage cells, chondrocytes, are isolated and grown in flasks. When the cells have multiplied enough, they are preserved for you until the time of your second surgery.
During your second surgery, the doctor will open your knee up with a small incision and prepare the cartilage hole to be filled with your own cartilage cells. They then use a piece of tissue from your body to cover the hole like a lid. They sew the "lid" in place with tiny sutures. The edges of the lid are sealed and your own cartilage cells are slowly injected under the lid into the canyon prepared in your cartilage.
These cells will then set up housekeeping and recreate healthy cartilage over time. The outcomes of ACI are variable and some people get excellent results while others don't. There seems to be a decrease in the outcome of this procedure with time, meaning that in the first few years it does well and then the function declines.
When none of the conservative treatments or procedures keep knee pain at bay, it is time to talk knee replacement, or as I like to it: healing with steel. In future blogs we will address this highly successful intervention for giving you your active life back.