Promising new therapies regenerate cartilage to repair damaged joints.
by Linda Rath
Elite athletes, including Tiger Woods, Kobe Bryant, Alex Rodriguez and Dara Torres, are using unconventional treatments with high-tech names to heal their worn-out joints. The goal of most of these therapies is to harness the body’s own healing power to repair damaged cartilage. For some, the results have reportedly been close to miraculous.
But how well do the procedures really work? And can they help non-celebrity joints, too?
Cartilage restoration bridges the gap between symptom relief and joint replacement surgery. Orthopaedic surgeon Jason M. Scopp, MD, director of the Joint Preservation Center at Peninsula Orthopaedic Associates in Salisbury, Md., and a member of the International Cartilage Repair Society’s publications committee, likens it to road repair.
“When cartilage damage occurs, you no longer have a smooth relationship between the bones in the joint. It’s like driving over a pothole in your car,” he says. “In cartilage repair, we’re filling in the pothole so it doesn’t get larger.”
Dr. Scopp is optimistic about the future of the field. “We’re entering an exciting era in joint restoration and preservation, where the older cartilage-repair procedures are being replaced by the newer, biological type. There are many different avenues that are being investigated, and we don’t necessarily know which is the right one, but we know we’re on the right path,” he says.
Others agree that cartilage restoration has great potential, especially for younger, active patients with a small cartilage tear or defect, but the new procedures aren’t for everyone. Orthopaedic surgeon Brian J. Cole, MD, head of the Cartilage Restoration Center at Rush University Medical Center in Chicago, stresses they’re not intended for patients with bone-on-bone osteoarthritis (OA). But, he adds, “At the very least, they may prevent or forestall arthritis in the future.”
Some of these techniques have been around for decades. Others are not yet approved for use in the United States. A few are controversial, especially for treating OA. We asked experts to help separate the science from the hype.
I Microfracture surgery
This is the benchmark by which other techniques are judged, because it was developed nearly 25 years ago. Since then, it has widely been used as a first-line surgical treatment for joint pain, swelling and stiffness. More than 25,000 procedures were performed in 2007 in the United States.
HOW IT WORKS – After cleaning and smoothing the edge of the tear, surgeons pierce holes in the underlying bone. A blood clot rich in stem cells and growth factors forms in the treated area, and over time, the clot remodels into fibrocartilage, which is less supple and durable than the original, hyaline cartilage. A newer procedure called autologous matrix-induced chondrogenesis stabilizes the clot with a protective collagen membrane.
WHO MIGHT BENEFIT – Normal-weight people ages 15 to 50. Results are best in patients younger than 40 with healthy bone and defects smaller than 4 centimeters (about 1.5 inches) square. Microfracture can help repair cartilage in most joints, including ankles and elbows.
WHAT THE EXPERTS SAY – “It’s not very durable after five years,” says orthopaedic surgeon Riley J. Williams III, MD, director of the Institute for Cartilage Repair at the Hospital for Special Surgery in New York. “It’s not the most effective treatment, but it’s easy to do, inexpensive and doesn’t require a lot of applied technology.”
II Osteochondral autograft or allograft transfer system (OATS)
The only procedure that restores true hyaline cartilage to the joint, OATS is considered a second-line treatment, but recent studies show it provides better and longer-lasting results than microfracture.
HOW IT WORKS – In an osteochondral autograft, a small plug of cartilage and bone is transplanted from a healthy area of the patient’s knee to a damaged area. (Transplanting several smaller plugs is called mosaicplasty.) For larger areas, doctors may use allografts – donated tissue from a tissue bank.
WHO MIGHT BENEFIT – Autografts are best for active people ages 15 to 50 with a small “pothole” in the knee, elbow, shoulder or ankle. Some people with OA or other degenerative joint disease also may benefit from allografts.
WHAT THE EXPERTS SAY – “You don’t want to create another defect at the donor site, so this is mainly for small lesions,” says Dr. Scopp. “It’s also costly, but it’s better long-term than microfracture.”
Dr. Williams uses these transplants to ease OA pain and delay disease progression. “For people with early arthritis who aren’t ready for an artificial knee, we can do multiple large grafts. The grafts contain live cells, and over time the patient’s bone grows into and replaces the allograft bone,” he explains. Although most patients do “remarkably well,” he adds, allograft supply and a slight potential for disease transmission are concerns.
III Synthetic scaffold resurfacing
Originally developed to fill holes from which graft tissue was harvested, synthetic plugs are now also used as graft alternatives. Knee surgeons often recommend them for certain patients because they’re long-lasting and protect the joint from further wear and tear.
HOW IT WORKS – Synthetic grafts are engineered to resemble natural ones, with a top layer that mimics cartilage and a bottom layer that mimics bone. The plugs are soaked in a solution of stem cells before being placed in the damaged joint, and the stem cells stimulate the growth of tissue that functions much like normal cartilage and bone.
WHO MIGHT BENEFIT – Normal-weight people younger than 60. Young, active patients tend to have better results.
WHAT THE EXPERTS SAY – “With these, you can do synthetic OATS and mosaicplasty without damaging another area of the knee,” Dr. Williams says. “[They] allow us to extend the size of the treated area to about 8 millimeters [1/3-inch] square. I’m floored with the clinical results. In younger patients, the return-to-sport rate is about 90 percent.”
IV Autologous chondrocyte implantation (ACI)
Although used in the U.S. for 15 years, Dr. Williams cautions that only a few surgeons have performed this difficult, two-stage procedure successfully.
HOW IT WORKS – In an initial arthroscopic procedure, surgeons remove a small piece of healthy cartilage from the knee. It is cultured in a lab, producing millions of new cartilage cells (chondrocytes) within weeks. In a second, open surgery, a patch made of collagen or shin tissue is fitted over the damaged cartilage and sealed. The cultured chondrocytes are injected under the patch, and as they mature, they fill in lost tissue with hyaline-like cartilage.
WHO MIGHT BENEFIT – Peoples ages 15 to 50 with a single cartilage defect no larger than 10 centimeters (nearly 4 inches) square in the knee or ankle. ACI may be used off-label to treat other joints and OA.
WHAT THE EXPERTS SAY – “Initially we thought [ACI] could grow cartilage effectively, but now we’re not so ebullient,” Dr. Williams says. “It can form hyaline-like cartilage with some clinical efficacy, but it’s very expensive, requires to surgeries, has a high re-operation rate and an extended recovery of one year.”
V Autologous cartilage tissue implants
Using a combination of cell therapy and tissue engineering techniques, autologous cartilage tissue implants are the next logical step in tissue regeneration. Already in clinical use in Europe, a growing number of these second-generation methods are awaiting Food and Drug Administration (FDA) approval in the United States.
HOW THEY WORK – Bio-engineered implants are grown outside the body using a patient’s own chondrocytes. Although methods vary, a common approach is to culture cartilage cells, then seed them on a biodegradable scaffold made of synthetic collagen, hyaluronic acid or other materials. Growth factors, stem cells and bioreactors encourage the cells to grow and produce some cartilage before the implant is placed in the joint. Ideally, the implant integrates with existing tissue within a few months with a greater likelihood of producing good-quality cartilage.
WHO MIGHT BENEFIT – In clinical trials, patients ages 18 to 55 who have a large cartilage defect in the knee.
WHAT THE EXPERTS SAY – Dr. Williams likes an experimental implant made of collagen and autologous cartilage cells called NeoCart, which he is investigating in clinical trials. “The cells are seeded onto a three-dimensional collagen scaffold and subjected to high pressure [in a tissue-engineering processor or bioreactor], so they’re primed to produce new cartilage,” he says. In a recently published study, the implant significantly outperformed microfracture at two years.
VI Stem cells
Because mesenchymal stem cells (MSCs) from bone marrow can become chondrocytes, they are ideal for generating replacement cartilage tissue.
HOW IT WORKS – A number of methods for implanting MSCs are under investigation, but finding an appropriate scaffold to hold them has proved challenging. One solution is to inject bone marrow concentrate – a rich source of stem cells and growth factors – directly into a defect or implant it under a patch. Stem cells are also used to boost established techniques, such as scaffold resurfacing.
WHO MIGHT BENEFIT – Some researchers think stem cells have the best long-term potential for repairing OA-related cartilage damage.
WHAT THE EXPERTS SAY – Bone marrow concentrate impresses Dr. Scopp, who notes, “It has the advantage of being significantly less expensive [than other methods] and shows promising results in both animal and human models.”
Stem cells and bone marrow trick the body relatively easily into healing more completely and efficiently, says Dr. Cole. He is currently involved in a trial using stem cells and hyaluronic acid to augment microfracture. “If we can make [microfracture] better, it would be a home run,” he says.
VII Platelet-rich plasma (PRP)
PRP is almost as famous as the sports celebrities using it to repair injured elbows, shoulders, knees and ankles. Although some orthopaedic surgeons remain cautious, several recent studies found PRP safe and effective for cartilage tears. In other studies, it proved superior to hyaluronic acid for relief of knee pain in patients with mild to moderate OA. PRP is widely available in the United States, though experts note that some formulations of PRP work better for certain indications than others.
HOW IT WORKS – The procedure separates platelets from red and white blood cells in a small amount of a patient’s blood. The concentrated platelets are then injected into the damaged area where they produce high concentrations of growth factors, which reduce inflammation and promote tissue repair. Patients ideally improve within a few weeks.
WHO MIGHT BENEFIT – Younger people with acute and chronic sports injuries in almost any joint as well as those with localized areas of OA.
WHAT THE EXPERTS SAY – Dr. Scopp points out that PRP isn’t covered by insurance, so patients have to shoulder the entire cost, which ranges from $500 to $5,000 per treatment.
Dr. Cole is currently conducting a randomized prospective study comparing PRP with hyaluronic acid injections for knee OA. “Our hope is that we’ll be able to show that the use of platelets is superior in improving the biochemistry of the joint,” he says. PRP might postpone the need for joint replacement surgery, he adds.