Talar Cartilage Defects -What's new?
In each issue of the Journal of the American Academy of Orthopaedic Surgeons, there is a special section called Perspectives on Modern Orthopaedics. In that section, new or controversial techniques are discussed. The authors review the literature and summarize current understanding about the topic at hand. And they offer their own opinions from personal experience.
In this issue, cartilage transplantation techniques for talar cartilage lesions are presented. The talus is a bone in the ankle just above the calcaneus (heel) and just below the tibia (lower leg bone). The bottom of the tibia and the top of the talus form a curved dome-shape that allows the foot and ankle to move up and down smoothly.
Cartilage tears or defects in this area are like cartilage lesions in other joints. There is no direct blood supply, so healing without surgery is unlikely. Methods of repairing the cartilage are under investigation. The first place to start is by trying techniques used for other areas of the body such as the hip or knee.
But researchers are proceeding cautiously because the cartilage protecting the talus isn't exactly the same as articular cartilage in other joints. For one thing, talar cartilage is thinner and it seems to hold up better with age. A good stiff cartilage is what helps stabilize the joint. Loss of tensile stiffness is a common change in the mechanical properties of the hip and knee that isn't seen so much with the ankle.
Surgeons know a lot more about cartilage, its properties, and its injuries now that there are MRIs and arthroscopic examinations available. These diagnostic techniques make it possible to see the exact size, shape, and location of cartilage lesions. All of these tools are used to plan the most appropriate treatment.
Nonoperative (conservative) care might work okay for sedentary (inactive) adults with a small lesion. But active individuals and especially athletes eager to get back into action will need surgery to repair or restore the cartilage. Repair debridement is the first line of treatment for small lesions (less than 1 cm2 in size). The surgeon carefully removes any loose pieces and smoothes any frayed edges.
If that doesn't work, then the debridement may be repeated. If further treatment is needed, restoration rather than repair is advised. Restoration means that normal hyaline cartilage is harvested from a donor site and transplanted to the defect or hole in the cartilage. Sometimes the donor material comes from the patient. That's called an autograft. When the harvested healthy cartilage comes from another person, it's referred to as an allograft.
In either case, essentially what happens is the surgeon takes a plug of cartilage and the bone underneath it from a healthy site (usually the nonweight-bearing portion of the knee) and transplants it into the defect or hole in the damaged cartilage. This is called an osteochondral autograft transplantation (OAT).
The patient stays off that leg for several weeks after surgery to avoid disrupting the healing process. Reports so far of short- to mid-term results are very favorable with this technique. The studies are small but the majority of patients report good-to-excellent results. They say they would have the same procedure done again if they had it to do all over.
That was the first method used to try and restore the cartilage. Now, the technique has advanced forward. A new method called autologous chondrocyte implantation (ACI) is available. Healthy cartilage cells are taken from the patient and grown in a lab until 200 to 300 cells becomes 12 million cells. It takes about six to eight weeks to accomplish the multiplication process.
Then the new cartilage cells are transferred back into the defect (hole). The advantage of this approach is that the new cells can be saved in a cold place for more than a year. The disadvantage is that the procedure requires two separate operations.
In the second operation, the lesion is smoothed and prepped for the new cells. A special patch of bone is layer over the top to protect the healing area. The new cartilage cells are injected under the patch. Then the patch is sealed with a special fibrin cement or glue. Again, small studies are reporting good-to-excellent results that last beyond 48 months (four years).
In a few patients, the surgeons are able to do a repeat arthroscopy exam and sample some of the healed tissue to see what's really going on. They have been able to see that the defect doesn't always fill in with good hyaline cartilage. Sometimes it's just a fibrous filler, so there's some concern about that.
One final restorative technique under investigation is the matrix-induced autologous chondrocyte implantation (MACI). This is similar to the autologous chondrocyte implantation. But instead of growing the harvested cells in a culture and then injecting them into the defect, they are placed on a special membrane where they grow and multiply. The membrane is then used to fill and cover the defect. No extra bone patch or flap is needed. Cells can also be harvested right next to the damaged area, rather than finding another spot to gather them (e.g., from the knee).
The authors were quite enthusiastic about the MACI treatment approach for talar dome lesions. They pointed out five possible advantages of this procedure over the others:
It can be done without cutting into the ankle bone, a procedure called malleolar osteotomy
Since cells are harvested from right next to the defect, there's no donor site and no donor site problems
Fibrin glue can be used without additional stitches required
Cells can be harvested and stored for use later when the initial debridement is done (the just-in-case approach); that way, if the debridement is not successful, the stored cells can be pulled out of the freezer without doing yet another surgical procedure.
With the MACI technique, there are more live cells transplanted compared with the ACI approach; that may translate into better results later on.
Even with these more advanced restorative techniques, it's still advised to have debridement first to repair the initial damage before advancing to the more invasive restorative process. And not just once, but debridement may be done up to three times before considering a restorative procedure. If there are loose fragments of cartilage, these should be restitched to the joint surface whenever possible.
But when all efforts fail to produce a satisfactory result, then the osteochondral autograft transplantation (OAT), autologous chondrocyte implantation (ACI), or matrix-induced autologous chondrocyte implantation (MACI) procedure can be used. These approaches are still considered a potential second-line treatment procedure. They are not the first effort made to repair or restore the problem.
More studies are needed to compare and contrast the results of these three treatment approaches for large lesions in active adults who have failed to heal adequately with debridement or other similar repair techniques. Surgeons will continue to look for ways to tell which procedure might suit each patient best. Optimal results that hold over the long term are destired.
Matthew E. Mitchell, MD, et al. Cartilage Transplantation Techniques for Talar Cartilage Lesions. In Journal of the American Academy of Orthopaedic Surgeons. July 2009. Vol. 17. No. 7. Pp. 407-414.