Knee Surgery Technique To Regrow Damaged Cartilage
From everyday persons who suffer daily doing the simplest movements to athletes, knee pain due to cartilage damage could soon be relieved by a relatively new procedure.
MACI, an acronym for Membrane-Induced Autologous Chondrocyte implantation, uses an individual's own cartilage to grow more cartilage and repair a damaged defect. Orthopedic surgeons have been doing ACI (Autologous Chondrocyte Implantation) surgeries for more than 20 years now. But MACI includes a new product, the MACI membrane, which consists of autologous cultured chondrocytes on porcine collagen membrane. The MACI membrane is manufactured by Vericel of Cambridge, Massachusetts, a leader in advanced cell therapies.
Dr. C. Benjamin Ma, an orthopedic surgeon, professor in residence, and chief of sports medicine and shoulder surgery at the University of California San Francisco, said MACI is a second-generation product of ACI. “MACI is a two-stage process,” Ma says. “First, they biopsy the cells and send them to the lab to grow for four to six weeks and form more cartilage. The membrane with the new cartilage is then put back into the knee.”
“The first-generation cartilage resurfacing procedure was microfracture,” Ma said. “It’s a different process. Surgeons drill tiny holes into the bone to let blood bleed into the defect and form scar tissue. It’s been used for 30 to 40 years. The results are OK, but people are always looking to possibly improve on it. ACI has been proven to provide long-lasting pain relief and to help patients regain knee function.”
Gerard Michel, Vericel’s chief financial officer and Vice President for corporate development, said, “MACI is an improvement upon earlier generations of ACI such as Carticel, which had been on the market for two decades. We acquired both Carticel and MACI in 2014 from Sanofi Genzyme and another product called Epicel, which is used with severe burn patients. MACI was not yet available in the U.S. We received FDA approval for it in December 2016 and launched it in early 2017.”
Chondrocytes are the cells responsible for the production, maintenance, and repair of cartilage. But they don’t do much repair, Michel said. Once cartilage is formed, chondrocytes don’t produce much more cartilage, even when someone has an injury. “Once you have a cartilage defect, you probably will have it for the rest of your life,” he said. “Cartilage gets damaged from repetitive injuries — if you run a lot and your knees are not perfectly aligned you may develop a defect,” Michel explained. “Or you can have an acute injury, for example, playing soccer and having your knee pushed sideways. Once you have those injuries, the cartilage is not going to repair itself.”
The only option to regrow your own cartilage is ACI. That’s where Vericel’s product, MACI, comes in. This third-generation product uses the patient’s own chondrocytes, seeded onto a collagen membrane (similar to what is used in dentistry and other applications).
“One side of the membrane is fairly smooth and the other fairly porous, allowing significant area for the chondrocytes to seed and adhere to,” Michel said. “Prior to seeding the membrane, we expand the chondrocytes to ensure an adequate number of cells. After expansion, we take the patient’s cells, put them on the membrane, and ship them back to the doctor.
“The physician makes a small incision in the knee and cuts a template to fit the size of the defect. Once the doctor is satisfied with the fit, the MACI membrane is glued into place. The cells migrate onto the bone, adhere to it, start to replicate, and initiate cartilage production to fill in the defect.”
One California team physician who uses MACI has achieved gratifying results with some of his patients, who include college and professional athletes. Dr. Kristofer Jones, an orthopedic surgeon and sports medicine specialist at University of California Los Angeles (UCLA), is team physician for the UCLA Bruins and assistant team physician for the Los Angeles Lakers.
“I’ve used MACI for athletes at all levels of participation from high school to professional,” he added. “I’ve also used it with patients that simply have pain with routine activities of daily living — climbing stairs, squatting, or walking for extended periods of time. The expected timeline for unrestricted return to high-level athletic activities is approximately 12 months. Patients can expect to return to pain-free simple activities of daily living within four to six months.”
Jones began performing the MACI procedure when it first received FDA approval two years ago. “Given this documented success, I felt confident providing this surgical option to my patients,” he said. “Thus far, I have had a similar type of experience as my European colleagues and have found reliable pain relief with improved physical function at a minimum of 12 months follow-up in my patients.”
“I have been extremely encouraged by my own personal observations for my patients that have undergone this procedure,” Jones said. “And I continue to follow the long-term results of my European colleagues that have been performing this procedure for a longer period of time. It is my hope that the early clinical improvements that we are observing at two and five years after surgery are maintained at 10 and 15 years.”