Cartilage Repair and Restoration
The cartilage can get damaged from normal wear and tear of the body’s joints as we age as well as from injury or other disease conditions. Because of its avascular nature (absence of blood supply), the cartilage cannot repair itself, necessitating surgical treatment to restore cartilage function and prevent progression of the damage into arthritis. Damaged cartilage can be treated by two different techniques – repair and regeneration. Repair technique involves replacing damaged cartilage with new cells and extracellular matrix that stimulates healing of the injured cartilage. Regeneration involves replacing the injured cartilage with a new articulating surface that functionally simulates the growth of original cartilage.
Articular cartilage is the smooth, shiny, white tissue covering the ends of bones those form a joint. Articular cartilage reduces friction when bones glide over each other, making the movements smooth and painless. It also acts as a shock-absorber to help prevent traumatic injuries to the bones.
Articular cartilage may be damaged by accidental falls, sports injuries or progressive degeneration (wear and tear). It is possible for cartilage cells to heal, but it depends on the extent of the damage and location of injury. However, the healing capacity is minimal owing to the lack of blood supply.
When cartilage gets damaged, it can cause painful movements, limit joint mobility and eventually progress to osteoarthritis.
Your surgeon will perform a physical examination to look for altered range of motion, swelling and bone alignment. Often, an evaluation with magnetic resonance imaging (MRI) or arthroscopy will be needed as cartilage is uncalcified and does not show up in X-rays.
Young adults with cartilage injuries are ideal candidates for cartilage restoration surgery because these methods help prevent the progression of damage into osteoarthritis.
Young patients with a single lesion and healthy bone are suitable candidates for microfracture procedure. Osteochondral allograft transplantation is performed when the cartilage defect is large enough for an allograft to be used. Osteochondral autograft transplantation is done for smaller defects and can be performed with arthroscopic technique.
Surgery is often not recommended in smaller cartilage defects. Defects smaller than 2 cm can be treated arthroscopically and have a good prognosis. Larger defects may require cartilage transplantation.
The surgical procedures for cartilage restoration include:
- Abrasion arthroplasty
- Autologous Chondrocyte Implantation
- Osteochondral Autograft Transplantation
- Osteochondral Allograft Transplantation
Most cartilage restoration procedures can be performed arthroscopically, a minimally invasive surgery using an arthroscope, a small flexible tube with a light and video camera at the end that enables your surgeon to view the joints and perform the surgery. During arthroscopy, a few small puncture incisions are made around the joint. In certain cases, open surgery may be required to access the affected area, requiring longer incisions. Your surgeon will discuss the best surgical options for your particular condition. The different techniques are briefed below.
The microfracture technique involves poking multiple holes into the subchondral bone below the cartilage with a sharp tool called an awl that is passed through the arthroscope. This creates blood supply to the damaged cartilage and stimulates the formation of new cartilage.
Drilling is an arthroscopic procedure similar to microfracture in which multiple holes are made in the subchondral bone with the help of a surgical drill or wire, to create a healing response. The limiting factor of this procedure is the heat produced by the drilling can injure the surrounding tissues; therefore, some surgeons do not recommend this procedure.
Autologous chondrocyte implantation
Autologous chondrocyte implantation (ACI) is accomplished in two steps. The first step involves growing new cartilage cells followed by the implantation of these new cells into the defect.
The first step is performed arthroscopically, during which healthy cartilage cells are removed from a non-weight bearing area of the bone. These cells are then cultured in a laboratory for 3-5 weeks to increase their number.
Implantation of the new cartilage cells is performed through an open surgical procedure called arthrotomy. Arthrotomy involves preparation of the defect, following which a layer of the bone lining (periosteum) is stitched over the defect and sealed with fibrin glue. The cultured cells are then injected into the defect just below the cover.
Autologous chondrocyte implantation is indicated in younger patients who have a single, larger lesion over 2 cm diameter. As the patient’s own cells are used, there is no risk of tissue rejection.
Osteochondral autograft transplantation
Osteochondral autograft transplantation is a procedure in which healthy cartilage tissue is taken from a non-weight bearing part of the body and placed into the defect area to creat a smoother surface on the cartilage of the joint.
Osteochondral allograft transplantation
An allograft, a block of cartilage or bone obtained from a deceased donor, is used. The allograft is sterilized and prepared so as to fit exactly into the defect area. This procedure does require a larger, open incision.
After the completion of surgery, you will be advised to practice certain post-operative care measures to ensure better outcomes. They include:
- Suture care: A dressing will be placed over the sutures and you will be instructed on when it can be removed (usually after 3 days). You may apply ice over the dressing for 20 minutes every hour to decrease swelling and pain.
- Exercises: Physical therapy is usually started within 1-2 weeks of surgery to help restore motion to the affected joint.
- Activity restrictions: Your surgeon will give you activity restrictions to follow during the healing process depending on which joint is involved.
Risks and complications
As with any surgery, cartilage repair and restoration may be associated with certain risks and complications such as
- Graft delamination: Detachment of the grafts from the subchondral bone and the surrounding cartilage
- Allergic response: Transfer of disease and infection, and graft rejection in allograft transplants
- Injury to healthy cartilage
- Post-operative bleeding
- Deep vein thrombosis
- Stiffness of the joint
- Numbness around the incisions
- Injury to vessels or nerves