Cartilage Restoration and Preservation
Articular or hyaline cartilage is the tissue lining the surface of the two bones in the knee joint. Cartilage helps the bones move smoothly against each other and can withstand the weight of the body during activities such as running and jumping. Articular cartilage does not have a direct blood supply to it so has less capacity to repair itself. Once the cartilage is torn it will not heal easily and can lead to degeneration of the articular surface, leading to development of osteoarthritis.
The damage in articular cartilage can affect people of all ages. It can be damaged by trauma such as accidents, mechanical injury such as a fall, or from degenerative joint disease (osteoarthritis) occurring in older people.
Patients with articular cartilage damage experience symptoms such as joint pain, swelling, stiffness, and a decrease in range of motion of the knee. Damaged cartilage may to be replaced with healthy cartilage and the procedure is known as cartilage replacement. It is a surgical procedure performed to replace the worn out cartilage and is usually performed to treat patients with small areas of cartilage damage usually caused by sports or traumatic injuries. It is not indicated for those patients who have advanced arthritis of knee.
Cartilage replacement helps relieve pain, restore normal function, and can delay or prevent the onset of arthritis. The goal of cartilage replacement procedures is to stimulate growth of new hyaline cartilage. Various arthroscopic procedures involved in cartilage replacement include:
Microfracture
Drilling
Abrasion Arthroplasty
Autologous chondrocyte implantation (ACI)
Osteochondral Autograft Transplantation (OATS)
What is Articular Cartilage?
Microfracture
A microfracture procedure creates small holes in the bone. The surface layer of bone, called the subchondral bone, is hard and lacks good blood flow. By penetrating this hard layer, a microfracture allows the deeper, more vascular bone to access the surface of the joint. This deeper bone has a rich blood supply, and the cells can get to the surface layer to stimulate cartilage growth.
How Does it Work?
This procedure allows blood and stem cells to form a clot in the area of the cartilage defect. These cells have the ability to form a cartilage layer within the defect. In this way, the body is able to repair the damaged area of cartilage by stimulating blood flow to the defect.
Procedure
A microfracture can be performed as part of arthroscopic knee surgery. Other joints can be treated similarly, also by arthroscopic surgery.
During the procedure:
First, the area undergoing microfracture is prepared by removing any loose or damaged cartilage.
The area undergoing microfracture should be less than about 2 centimeters in diameter and have good, healthy surrounding cartilage.
A small, sharp pick (awl) is used to create the small microfracture holes in the bone.
The number of microfractures created depends on the size of the joint being treated. Most people with a 1- to 2-centimeter area of damage require five to 15 small microfracture holes in the bone.
Autologous chondrocyte implantation (ACI)
Autologous chondrocyte implantation, or ACI, is a procedure that treats isolated areas of cartilage damage in the knee. Surgeons remove cartilage cells, grow them in a lab, and then implant them in the area where cartilage is needed.
This procedure requires two surgeries several weeks apart. It generally shows good long-term results in repairing cartilage and allowing patients to return to their usual activities.1
Step 1: Harvesting
The first step of ACI is an arthroscopic surgery. This helps identify the area of cartilage damage and determine if it's appropriate for an ACI procedure.
During this surgery, a surgeon removes a small piece of cartilage—"typically the size of one or two Tic-Tacs," explains one orthopedics practice.2
This cartilage is then treated to isolate the chondrocytes, which are cartilage-producing cells. These are used to culture (grow more) cartilage cells, which takes about six to eight weeks. Then the second surgery is scheduled.
Step 2: Implantation
Unlike step one, the step-two surgery is not arthroscopic. The surgeon uses a larger incision to directly view the area of cartilage damage.
The surgeon also makes a second incision over the shinbone to harvest a section of the periosteum roughly the size of the area of cartilage damage. The periosteum is the thick tissue that covers the shinbone, and it becomes a patch for the knee.
The surgeon sews the periosteal patch over the area of damaged cartilage, creating a tight seal between the patch and the surrounding cartilage. Then they inject the cultured cartilage cells underneath the patch. The patch holds the new cartilage cells in the area of cartilage damage
An Osteochondral Autologous Transplantation or OATS procedure is when you are able to take bone and cartilage from a healthy part of the knee and implant it into a damaged area. The procedure is performed in a single stage. Cartilage is removed from a healthy non-weight bearing portion of the femur, usually the notch or trochlear area, and implanted onto the damaged weight-bearing portion of the femur.
Most of the time, the OATS procedure can be performed on lesions less than or equal to 4 cm2. However, ultimately the damaged cartilage area size, location, and specific patient factors will determine if you are a candidate for this procedure.
In general, OATS procedure demonstrates superior outcomes to microfracture techniques. One long-term clinical study looking at 831 patients undergoing this procedure showed good to excellent results for 92% of patients of femoral condylar transplantations, 87% of tibial resurfacing, and 79% of patellar and/or trochlear transplantations.
