Cartilage Repair & Transplants
What is Cartilage Replacement?
Cartilage replacement is a surgical procedure performed to replace the worn-out cartilage with new cartilage. It 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 the knee. Articular or hyaline cartilage is the tissue that covers bone surface of the knee which helps in smooth interaction between the two bones in the knee joint. It has less capacity to repair by itself because there is no direct blood supply to cartilage.
Cartilage Replacement Procedure
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:
- Drilling: This procedure is like microfracture where multiple holes are created in the injured joint area using a surgical drill or wires.
- Microfracture: Microfracture involves creating numerous tiny holes in injured joint surface using a special tool, called ‘awl’. The holes are made in the bone under the cartilage, called as subchondral bone. This creates a new blood supply to the cartilage which stimulates the growth of new cartilage.
- Abrasion Arthroplasty: This procedure is like drilling but involves use of high speed burs to remove the damaged cartilage.
- Autologous chondrocyte implantation (ACI): This is a two-step procedure, where healthy cartilage cells are removed from the non-weight-bearing joint, grown in the laboratory and then implanted in the cartilage defect during the second procedure. During this procedure, a patch is harvested from the periosteum, a layer of thick tissue that covers the bone and is sewn over the defective area using fibrin glue. The new cartilage cells are then injected under the periosteum into the cartilage defect to allow the growth of new cartilage cells.
- Osteochondral Autograft Transplantation: In this procedure, plugs of cartilage are taken from the non-weight-bearing areas of knee, from the same individual and transferred to the damaged areas of the joint. This method is used to treat smaller cartilage defects since the graft which is taken from the same individual will be limited. Following cartilage replacement, your doctor may recommend physical therapy to help restore mobility to the affected joint.
- Osteochondral Allograft Transplantation: In this procedure, healthy cartilage tissue or a graft is taken from a donor from the bone bank and transplanted to the area of cartilage defect.
What is Cartilage Transplantation?
The articular surfaces of the body’s joints are lined by hyaline cartilage, a smooth tissue that serves as a shock absorber and allows easy movement of the bones within the joint. Normal wear-and-tear or injury can damage and cause defects in the cartilage, resulting in irregular articular surfaces that interfere with movement, causing pain, swelling and disability. Cartilage cell transplantation is a technique of transplanting healthy cartilage cells to replace damaged cartilage cells. These procedures are recommended for young individuals with a single articular defect. It is usually performed on the knee joint but may also be used to treat the shoulder and ankle joints.
Autologous chondrocyte implantation (ACI) involves the removal of cartilage cells from your own body. The procedure is accomplished in 2 stages. The initial stage is an arthroscopic procedure where healthy cartilage is harvested from a non-weight bearing joint of your own body and sent to the laboratory, where the cartilage cells are extracted and cultured (multiplied) for a period of 3 to 5 weeks. In the next stage, an open surgery (arthrotomy) is performed where the dead joint tissue is removed and the defect prepared appropriately. A piece of membrane called periosteum that lines bone surfaces is obtained, usually from the tibia, and sewn over the defect and sealed with glue. Your doctor then injects the cartilage cells under the membrane into the defect where they grow and mature to form new cartilage.
Other variants of cartilage cell transplantation include the DeNovo graft and BioCartilage, which use pre-prepared human cartilage graft material. These procedures can be performed in one stage as they do not require harvesting of healthy cartilage tissue.
The DeNovo graft consists of pieces of viable cartilage in a storage media. Similar to ACI, the damaged cartilage area is prepared and sized. The graft is then prepared with a fibrin sealant and placed on the defect. The sealant precludes the need of a periosteal membrane.
BioCartilage consists of dehydrated cartilage, which is introduced along with platelet-rich plasma (concentrated blood component, which enhances healing) on the defects after a technique called microfracture is performed. Microfracture involves the creation of multiple holes at the damaged site to introduce blood supply and stimulate new cartilage to grow. The BioCartilage and platelet-rich plasma further promote cell growth and healing.
What is OATS?
OATS is “osteochondral autograft transfer system”. It is one of the two types of cartilage transfer procedures and the other procedure is “Mosaicplasty”. Cartilage transfer procedures involve moving healthy cartilage from a non-weight-bearing area of the knee to a damaged area of the cartilage in the knee. In mosaicplasty, plugs of cartilage and bone are taken from a healthy cartilage area and moved to replace the damaged cartilage of the knee. Multiple tiny plugs are used and once embedded, resemble a mosaic pattern, hence the name. With the OATS procedure, the plugs are larger. Therefore, the surgeon only needs to move one or two plugs of healthy cartilage and bone to the damaged area of the knee.
Indications of OATS
OATS is not recommended in everyone. OATS is typically used for patients aged<50 and with minimal cartilage damage, usually because of trauma, and available healthy cartilage for transfer.
In the OATS procedure, the surgery usually begins with an arthroscopic examination. Arthroscopy is performed in a hospital operating room under general anesthesia. Your surgeon makes a tiny incision over the knee and inserts an arthroscope. The arthroscope is a small fiber-optic viewing instrument made up of a tiny lens, light source and video camera to enable the surgeon to visually examine the knee.
If the surgeon decides the procedure can be performed, the scope is removed and an incision is made over the knee. The surgeon prepares the damaged area of cartilage. Using a special coring tool, surgeon makes a hole in the cartilage sized to fit the plug exactly. Your surgeon then harvests the plug of healthy cartilage and bone from the non-weight-bearing part of the knee. This plug is transferred to the cored hole and implanted into the prepared hole of the damaged area of the knee. Over time, a successful OATS surgery will enable the bone and cartilage to grow into the damaged area of the knee successfully resolving the patient’s knee pain.
Postoperative Recovery following OATS
Below are the steps to your post-operative recovery:
- You will wake up in the recovery room and then be transferred back to the ward.
- A bandage will be wound around the operated knee. You will usually be able to remove this the next day but leave the steri-strips in place. These will fall off.
- Once you are recovered, your IV will be removed and you will be shown several exercises to do.
- Your surgeon will see you prior to discharge and explain the findings of the operation and what was done during surgery.
- Pain medication will be provided and should be taken as directed
- It is normal for the knee to swell after the surgery. You will be sent home with a cryocuff cold therapy unit. Elevating the leg when you are seated and placing ice-packs or the cryocuff on the knee will help to reduce swelling. (20 min 3-4 times a day until swelling has reduced)
- You will be sent home with a CPM machine (continuous passive motion) and given instructions on proper usage.
- You may shower once the bandage is removed. Leave the steri strips intact.
- Please make an appointment 10-14 days after surgery to monitor your progress and remove your sutures.
- It is important to be compliant with your rehabilitation exercises to ensure a good outcome.
Risks and Complications of OATS
General anesthesia risks are extremely rare. Occasionally, patients have some discomfort in the throat because of the tube that supplies oxygen and other gasses. Please discuss with the anesthetist if you have any specific concerns.
Risks specifically related to the OATS surgery may include:
- Postoperative bleeding
- Deep Vein Thrombosis (DVT)
- Numbness of part of the skin near the incisions
- Injury to vessels, nerves and a chronic pain syndrome