First U.S. Study on Cartilage Repair of the Ankle

Scientists have found ways to get a healing response in joint cartilage, but nothing really restores the cartilage back to normal. It's now possible to take cartilage cells from one area of the joint and transfer them to the damaged section. This has been done successfully in the knee. In this article, results from the first attempt to do the same thing in the ankle are reported.

The procedure is called an osteochondral autograft transplantation or autologous chondrocyte implantation (ACI). Patients selected for the treatment have defects in the joint cartilage that go clear down to the bone.

The body tries to heal itself but only ends up with a cyst at the hole. The cartilage just doesn't have a self-healing mechanism. There isn't enough blood flow to the area. And chondrocytes (cartilage cells) don't move or reproduce themselves. Surgery is almost always needed to help the process along.

In this study, 11 patients with osteochondral lesions of the talus from trauma were treated with autologous chondrocyte implantation (ACI). The talus is a bone in the ankle that connects the calcaneus (heel bone) to the tibia (lower leg bone). In layman's terms, the talus is the anklebone that connects the foot to the leg.

Everyone in the study gave the nonoperative approach a good, solid try. But after months of bracing, casting, and antiinflammatory medications, they were still left with stiffness, and painful clicking or popping of the ankle. Surgery to manage the problem was also tried and failed.

In some cases, debridement was done (cleaning out the area of any loose tissue, frayed edges, or fragments of cartilage). In other patients, the surgeon tried pinning the pieces together or shaving down the cartilage to the bone to stimulate a healing response at the bone level. But none of these efforts worked either.

MRIs were done to show the location, size, and depth of the lesions. Most were on the medial (inside edge) of the talus. Two patients had lateral defects (along the outside of the talus). Patients with large enough defects were included in the study. The procedure involved removing the cyst and filling in the defect with graft material taken from the knee. In half the group, a sandwich procedure was used for the implantation.

The sandwich procedure is what the surgeons call the modified ACI procedure that they invented. In order to get to the damaged area on the talus, they first had to do an osteotomy. This involves cutting away a wedge-shaped piece of the lower leg bone (tibia or fibula, depending on which side the lesion was located). A special drawing was provided to show the reader where and how to make the correct cut. Incorrect placement for the bone cut for osteotomies on both sides (medial and lateral) were also shown.

Step-by-step, detailed, colored drawings of the sandwich procedure were also provided. Once the cyst was removed and the graft was in place, then the surgeon sewed a covering over the healing site. The covering is called a periosteal flap. This is the first piece of bread in the sandwich procedure. A special fibrin glue was injected between the flap and the bone graft. This was done to seal off the bone marrow cavity from the joint.

The surgeon put the second piece of bread in the sandwich right on top of the first. This was done by placing one more layer of bone on top of the first periosteal flap. This layer consisted of another periosteal flap, this time turned so the outer bone layer was facing the first periosteal flap. The second flap was also sewn in place, but the surgeon left a tiny opening at one end.

Once the second flap was sutured in place, then fibrin glue was used to form a tight seal around the sutures. They did a water test to make sure there were no areas of leakage. At this point, the filling was placed between the two pieces of bread. In other words, the harvested chondrocytes were injected between the two layers of bone graft (i.e., between the two periosteal flaps). The surgeon injected the transplanted chondrocytes into the tiny hole left open when the second periosteal flap was sutured.

The final surgical steps involved closing the tiny hole, sealing everything one more time with the fibrin glue, and reattaching the osteotomy. After surgery, the patients participated in a rehab program. They were allowed to put partial weight on the foot and started ankle range-of-motion exercises. They gradually moved to full weight-bearing when X-rays showed healing of the osteotomy.

A physical therapy program was started six weeks after the surgery. The program was carefully designed to match each stage of healing as the patient transitioned from remodeling to maturation of the graft site. Sport-specific training was included at the very end. The surgeons requested that only one therapist (who was familiar with the protocol) treated the patient for the entire rehab program.

Measures of success were taken throughout the postoperative period. Patient symptoms, satisfaction, and the Tegner activity score (test of function) were used to assess overall improvement. The Finsen score (a modified Weber score) and the American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot score were used to look more closely at joint function.

One other very important test was done. And that was a follow-up arthroscopic exam. This took place much later (9 months up to two years later). The surgeon used the scope to examine the repair tissue color, quantity of fill, and firmness compared to normal, healthy cartilage. And last, but not least, an MRI was also done some time later (months to years) in the follow-up process.

Patients went from rating their ankles poor to fair before surgery to a good to excellent result after surgery. All test scores showed major improvement in all areas. And the surgeons reported 100% success when the graft site was viewed by arthroscopic exam. This means there was complete coverage of the defect and no sign of inflammation or cartilage fraying.

The repair tissue was overgrown in two patients. In general, the new tissue was softer than healthy cartilage next to it. It did seem like the repair tissue was getting firmer over time. Other studies using MRIs to assess changes in defect repairs of this type have shown that cartilage remodeling continues for many months. None of the sandwich surfaces were completely smooth. Mild-to-moderate irregularity was observed with one case of severe surface irregularity.

Long-term results of these 11 patients will be needed to show what happens to the integrity of the repair tissue. Will the repair tissue hold up? How durable is it? Structural and biomechanical properties will be evaluated over time. And the results of this surgical approach will have to be compared to other methods of managing osteochondral lesions of the talus.

They have already noticed that the cystic lesions came back after being removed and repaired. They aren't sure if this affects the results or even what causes it. The authors were a little surprised that even with the sandwich procedure, the subchondral plate (bone tissue just below the cartilage) was depressed (sunk down).

When the surgery was finished, everything was smooth, even, and flat. They suggest that maybe the downward shift of the subchondral plate is somehow related to the cyst formation. More study will be needed to see if there is a link between cyst formation and structural integrity of the repair tissue. It's possible the cysts are a totally separate problem that has nothing to do with the cartilage defects.

The authors conclude that this method of repairing joint cartilage defects can be used with good results in the ankle. There may be a slight advantage to doing the sandwich procedure and ACI (instead of just the ACI). The sandwich group got better faster, although their final results were the same as the ACI group.

Because the sandwich procedure is so new, more studies will be needed before it becomes a standard treatment technique. On the other hand, this procedure may be just a step toward better, faster treatment methods. Some surgeons in other parts of the world have already found a way to avoid the time-consuming and difficult sandwich procedure.

They used a collagen membrane over the repair. Another group has found a way to make a super chondrocyte for better transplantation results. Thus, the race is on to find the magic answer to a quick and successful repair of severely damaged joint cartilage. Someday there may be a way to completely restore (not just repair) joint cartilage.

Reference: 

Ellis Kevin Nam, MD, et al. Autologous Chondrocyte Implantation of the Ankle. A 2- to 5-Year Follow-Up. In The American Journal of Sports Medicine. February 2009. Vol. 37. No. 2. Pp. 274-284.

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