Review of Management Options for Articular Defects of the KneeArticular cartilage is flexible body tissue that connects the joints. Although it is quite strong, it doesn't heal easily once damaged. Because it doesn't heal easily, torn cartilage of the knee, after trauma or degeneration, is a challenge to treat and can cause significant pain and disability if left untreated or not treated effectively. The authors of this article reviewed the basics of various available treatments, when they may be used, their advantages and disadvantages, and outcomes.
Bone marrow is used for many treatments these days, including repair of injured articular cartilage of the knee, a microfracture. It is the most commonly used treatment for small lesions that cause pain and disability. The pros for the treatment include that is it straight forward to perform and not terribly expensive. A surgeon stimulates bone marrow by making a small hole in the bone to allow mesenchymal cells to flow into the lesion (injured area), where they help form blood clots. These then begin to help the lesion heal. For this method of treatment to have a chance of being successful, the patient must have a contained lesion that can hold the blood clot. It will not be effective if the blood can leak out.
Two cons for this procedure exist. One is mesenchymal cells decrease as patients age. If there are not enough to help form clots to fill the lesion, the healing won't be complete and will likely result in an unstable repair. The second is although the post-operative rehabilitation period is demanding, it is critical for proper healing. The patients who have had the repair on a femoral (thigh bone) end of the knee may not bear weight for six weeks and must perform passive motion exercises from zero to 60 degrees for six weeks after surgery. This improves the circulation, giving the cartilage the nutrition it needs to heal effectively. Patients who had the procedure on the patella (kneecap) or the trochlea inside the joint), weight-bearing is allowed after surgery, but they are not allowed to bend their knee more than 40 degrees, so it must be kept braced. As with the other group, passive motion exercises begin immediately, for six to eight hours per day.
The outcome of the procedure is generally successful if the blood clot filled the lesion and the patient participated in the required post-surgery rehabilitation program. According to one study, by Steadman and colleagues, their study that involved patients under the age of 45 years, achieved significant improvement following repair of the microfracture. Another group of researchers, led by Mithoefer, found overall good to excellent long-term results in most of their patients (67 percent), fair in 25 percent, and pour in 8 percent. In this study, better outcomes were found in patients with lower body mass index. As well, the researchers had found, using MRI after the procedure, that 54 percent of the patients had good filling of the lesion, 29 percent had moderate filling, and 17 percent had poor filling. Recent studies that have looked at high-level athletes. In one, 25 National Football League players were treated with this method and 19 returned to their previous level of play the following season.
The authors point out that "Proper patient selection and meticulous attention to technical detail are critical to achieving a successful outcome following microfracture." That being said, this method of healing microfractures is not permanent and the results do deteriorate over time.
Other researchers have looked at adjuncts, add-ons, to marrow stimulation. One researcher, Hoemann, and his team, investigated adding chitosan, a thrombogenic and adhesive polymer (compound) to the marrow procedure. The addition of chitosan was to improve the fill and add strength. Another researcher, Strauss, and colleagues, tried using hyaluronic acid viscosupplementation, which he found to provide even better fill and stronger tissue resulting. However, these have not been tested yet in clinical trials.
Platelet-rich plasma is a blood product that is rich in platelets, which help blood clot. The theory behind using this product is this is product of the body with growth factor and other cells and factors that can help promote healing. Very early studies have been promising, but there have not yet been any clinical trials for this plasma either.
Whole tissue transplantation, called autologous osteochondral transplanation or autologous osteochondral mosaicplasty could be used to resurface the defects in the knee. The tissue is harvested from the the patient's femur (thigh bone) and transferred to the defective area. One of the main advantages to this procedure is its relatively short rehabilitation time after. The disadvantages include possible problems with the patient's donor site, limited availability for grafting, and not filling the lesion entirely.
Unlike the previous two procedures, this has been studied in clinical trials. One study of 53 athletes (26 professional and 27 recreational), done by Gobbi and colleagues, found that six years after the procedure, nearly 70 percent of the patients were close to normal. The patients who responded best were younger, had the problem for fewer than 12 months, had a lesion less than 2 centimeters in diameter, and had had not had previous surgery or procedures. In another study by Namdari and colleagues, 24 professional basketball players underwent this procedure. Unlike Gobbi's study, in this one, eight athletes were unable to return to play and of those who did return, most were unable to regain their previous level of ability. Another issue with the grafts and plugs is the stability after surgery. How stable they are depends on several technical factors.
Reviewing overall outcomes of autologous mosaicplasty shows that it is fairly successful. In one study, the largest series of 831 procedures, was evaluated by Hangody and Fulles. They found good-to-excellent results for 92 percent of femoral (thigh bone) lesions, 87 percent of tibial (shin bone) lesions, and 79 percent of patellofemoral (between the kneecap and femur) lesions.
A similar procedure, osteochondral allograft transplanation, uses cartilage from a cadaver. The advantages include being able to craft the exact size needed for the lesion and there being no donor site complications for the patient. However, there are limitations and they include limited resources for the donor tissue, high cost, possible rejection by the recipient's body, the graft not "taking," possible disease transmission, and the difficulty of the procedure itself.
Allografts can be fresh, cryopreserved, or fresh frozen. All have their advantages and disadvantages:
Fresh: Advantages include better viability of the tissue. Disadvantages are the short period of storage time and higher rate of disease transmission.
Cryopreserved: Advantages include being able to preserve the tissue for longer periods and the reduction of disease transmission. Disadvantage is the only intermediate viability and success.
Fresh frozen: Advantages also include longer preservation time and decreased disease transmission. Disadvantages include even further reduction of viability and success.
A study of 55 knees, done by Chu and colleagues, using osteochondral allograft (fresh) found good-to-excellent results. In reviewing the use of preserved tissue, a study by Williams and colleagues found no correlation between functional outcome and the graft storage time of up to 42 days. A similar study, by McCulloch and colleagues, had similar findings after comparing stored grafts with fresh grafts.
Autologous chondrocyte implantation is yet another procedure that was first performed in 1994. In this procedure, the surgeon implants a transparent (
Of 23 patients who have undergone this new procedure, 14 of 16 patients who had femoral lesions had good-to-excellent results. Another study, this one of 126 patients, showed that 76 percent of the patients reported good outcomes of quality of life, knee pain and overall health. This was found whether the patients had undergone previous treatments and procedures or not.
Finally, synthetic scaffold treatments involve delivering chondrocytes (cartilage cells) to the lesion, using an absorbable scaffold that support the cells until healing takes places. There are several advantages to this treatment, including the ability to evenly distribute the cells over the lesion, there is no need to harvest cells from a donor site, and it is a technically easier procedure than some others.
The authors concluded that given the lack of well-designed studies comparing the various treatments, it is not possible to say if one is better than another. They did find, however, that bone marrow stimulation is effective if the lesion is filled completely and the patient is compliant with rehabilitation. Mosaicplasty, while effective, has limited graft availability and may cause problems at the donor site. Allografts are effective for large lesions and hyaline-like implants could result in better long-term outcomes. Using synthetic scaffolds to deliver the chondrocytes is a promising treatment, but has yet to be proven in clinical trials.
Asheesh Bedi, MD, Brian T. Feeley, MD, and Riley J. Williams III, MD. Managements of Articular Cartilage Defects of the Knee. In The Journal of Bone & Joint Surgery. Feb. 2010. Vol. 92. No. 4. Pp. 994-1009.
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