Cartilage restoration for articular cartilage injuries
Osteochondral defects are injuries to the articular cartilage of a joint. While any joint can be affected, the most common are the knee and the ankle (the talus bone).
Techniques used
- OATS procedure
- Osteochondral allograft transplant
Symptoms
The most common symptoms are pain and swelling in the affected joint. The pain is usually dull, though it can be sharp at times. There is usually noticeable joint swelling, which can itself be uncomfortable, and range of motion can be reduced because of it. You may also notice a painful clicking or catching sensation.
Why it happens
Osteochondral defects arise by three different mechanisms affecting three different age groups.
In the 10 to 28 age group, osteochondritis dissecans. Its mechanism is poorly understood, but it produces a discrete cartilage defect, usually in the knee, which may or may not be associated with trauma.
In the 18 to 50-plus group, usually traumatic and secondary to sports injury, often alongside other injuries such as meniscal and ACL tears in the knee, or ligament sprains in the ankle.
In the 60-plus group, spontaneous osteonecrosis or avascular necrosis leading to a defect. This follows a sudden loss of blood supply to a discrete area of the knee or hip for unclear reasons, and results in loss of cartilage, frequently leading to diffuse osteoarthritis of the joint quite rapidly.
How it is diagnosed
Diagnosis begins with a detailed history and a thorough physical examination. X-rays are the most important initial study; for the knee and ankle specialised weight-bearing views are obtained, meaning you will be standing. In certain situations a bone scan may help make the diagnosis.
Treatment
Treatment depends on which of the three variants you have.
Osteochondritis dissecans is usually treated operatively as soon as the diagnosis is made, to make use of the healing response in the early phase. Surgery is usually arthroscopic and aims to reinsert the loose fragment where it broke off, using bio-absorbable pins. Sometimes the loose fragment grows and no longer fits the defect, in which case it is removed and the defect resurfaced another way.
Traumatic defects are usually treated operatively as soon as diagnosed. Surgery is usually arthroscopic, with the choice between microfracture, mosaicplasty, or autologous chondrocyte implantation depending on the size and depth of the lesion. An osteotomy may be needed to realign the knee in certain patients.
Spontaneous osteonecrosis is usually treated non-operatively at first: crutches to unload the knee for six weeks, medication for pain and to help regenerate bone, and physical therapy for range of motion and swelling control. If that fails, surgery follows. Arthroscopy is usually not very successful here unless there is other pathology such as a meniscus tear, and can make symptoms worse and accelerate cartilage degeneration. Microfracture may be attempted but results are variable; mosaicplasty and chondrocyte implantation are not indicated. The definitive procedure is a partial or total knee replacement.
Recovery
Specific instructions depend on the procedure. Briefly, after arthroscopic microfracture or mosaicplasty, weight bearing is protected for six weeks with crutches, and a continuous passive motion machine is used at home for six hours a day across that period. Both measures are essential to the success of the surgery. A similar regimen applies to autologous chondrocyte implantation. Physical therapy may be needed for up to six months.
For joint replacement, you will typically be in hospital one to four days and able to bear full weight, usually with a cane or crutches. For the first six weeks you will be given medication to prevent blood clots in the legs, usually aspirin, though other medication may be used. Physical therapy may be needed for up to six months.
Common questions
What is articular cartilage?
It is the lining on the ends of the bones that articulate against one another. Articular cartilage is hyaline cartilage, a very smooth tissue roughly a hundred times slicker than wet ice on wet ice, providing a nearly friction-free surface for the joint. Fibrocartilage is a different type, typically seen in repair tissue after procedures such as microfracture.
What is the microfracture technique?
An arthroscopic technique where small holes are made within the defect with a sharp awl-like instrument, allowing marrow cells to enter and regenerate cartilage. The cartilage generated is fibrocartilage rather than the hyaline cartilage that normally forms articular surfaces.
What is mosaicplasty?
A technique where plugs of articular cartilage, or cartilage substitutes, are placed into the defect to restore the surface to near normal. The plugs can come from a low-contact area of your own knee, or from donor tissue.
What is OATS?
The osteoarticular transfer system is a mosaicplasty technique that harvests osteoarticular plugs from an area of the knee not under high contact and transfers them into the defect. It restores hyaline cartilage to the defect, at the cost of harvesting it from another site in the knee.
What is osteoarticular allograft transplantation?
A technique where donor osteoarticular tissue is transplanted into the defect. The tissue comes from a tissue bank and must be cryopreserved, and is typically implanted within 14 to 21 days of harvest to keep the chondrocytes viable. There is a small risk of disease transmission and immune rejection. It is reserved for young patients with very large defects.
What is autologous chondrocyte implantation?
A two-stage procedure. In stage one, an arthroscopic procedure diagnoses the problem and harvests a small amount of articular cartilage, which is cultured to multiply the chondrocytes. In stage two, usually 4 to 6 weeks later, the multiplied cells are placed into the defect. This is an open procedure: a thin layer of tissue called periosteum is harvested from the tibia and used to cover the defect, and the chondrocytes are injected underneath. The aim is to regenerate hyaline cartilage, though histological studies show fibrocartilage is the predominant tissue that forms.
What is an osteotomy?
A procedure where alignment is restored by cutting the bone involved and moving it to a slightly different orientation, altering weight distribution through the joint. The bone is re-fixed with plates and screws. Types include high tibial osteotomy, femoral osteotomy and tibial tubercle osteotomy.
How are kneecap defects treated?
Patellar defects are an uncommon and more difficult subset. Microfracture is typically used. Weight bearing is not usually protected, but a continuous passive motion machine is used for six weeks.
Knee video
Back to work in six weeks after robotic assisted total knee replacement
Robotic knee replacement offers the advantage of minimising surgical trauma. The implant is positioned to a precision of less than 1mm on a computer screen before a single incision is made. Once Dr. Seneviratne is satisfied with the implant position, the robot makes precise cuts in the bone, allowing implantation with less surgical trauma, a faster recovery and an earlier return to daily activity and work. Note that this is anecdotal; research studies are ongoing to define the merits of robotic assisted knee surgery.
Left partial knee replacement for single compartment osteoarthritis
Robotic assisted partial knee replacement offers a rapid recovery with an early return to function.