Cartilage Repair

While training at the prestigious Brigham and Woman's Hospital in Boston, MA, Dr. Matthys learned various techniques to restore the young patient's knee without a knee replacement. This procedure is commonly referred to as Biological Resurfacing.

Traumatic articular cartilage injuries in the knee are common and are a frequent cause of pain and loss of function leading to poor performance in athletes and active young patients. When these hyaline cartilage injuries are full thickness, the potential long term problems include early osteoarthritis and its associated disability.

Although full-thickness articular cartilage defects constitute only a small portion of all cartilage injuries, their poor capacity for repair makes their treatment a great challenge. This has recently aroused media interest with regard to the use of a relatively new procedure - autologous chondrocyte implantation (ACI)

Sports injuries account for 28% of all knee injuries. Chondral damage, including both partial and full thickness defects, has been documented in up to 61.5% of knee arthroscopies for knee symptoms. In the United States 650,000 reparative knee procedures are carried out each year, of which 20,000 to 40,000 could qualify for autologous chondrocyte transplantation.

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Biological Resurfacing Procedures:

(frequently more than one procedure may be used in the same patient)

  • Knee Arthroscopy with Chondroplasty or Microfracture
  • Meniscal Transplant
  • Mosaicplasty or OATS procedure
  • Allograft Reconstruction of structural defects
  • Osteotomy
  • Cartilage Transplant

Definitions:

Arthritis: a condition that simply means damage to the joints. Most people after the age of 30 have some degree of arthritis in their body. Arthritis is a progressive disease. It is more common in the older age population and currently there is no treatment for it. It has many causes which include:

  • osteoarthritis
  • Rheumatoid
  • gout
  • infection
  • trauma or fractures of the joint
  • isolated cartilage lesions in young active patients (osteochondral defects)
  • psoriasis
  • Lupus (Reactive Arthritis)

Cartilage: this is a generic term doctors use to describe the slippery surface that covers the ends of bones. However, cartilage has many functions and there are 3 types. These include Elastic cartilage, Fibrocartilage and Hyaline cartilage.

Cartilage has several functions. It covers the surface of joints, allowing bones to slide over one another, thus reducing friction and preventing damage; it also acts as a shock absorber (meniscal cartilage of the knee). It forms part of the structure of the skeleton in the ribs, where it joins them to the breastbone (sternum). Cartilage is found in the tip of the nose, in the external ear, in the walls of the windpipe (trachea) and the voice box (larynx) where it provides support and shape.

Cartilage does not have a nerve or blood supply, so it does not heal well.

Hyaline Cartilage: is a rather hard, translucent material rich in collagen and proteoglycan. It covers the end of bone to form the smooth articular surface of joints (knee, hip , shoulder, hand and many more). Without this type of cartilage the joints may not ride smoothy on one another.

Fibrocartilage: is a white, very tough material that provides high tensile strength and support. This is not as durable as hyaline cartilage.It contains more collagen and less proteoglycan than hyaline cartilage. Commonly injured hyaline cartilage will repair itself with fibrocartilage.

Microfracture:

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The surgery is performed by arthroscopy. After cleaning the calcified cartilage, the surgeon creates tiny fractures in the adjacent bones (through the use of an awl). Blood and bone marrow(which contains stem cells) seep out of the fractures, creating a blood clot that releases cartilage-building cells. The microfractures are treated as an injury by the body, which is why the surgery results in new, replacement cartilage. The procedure is less effective in treating older patients, overweight patients, or a cartilage lesion larger than 2.5 cm. Further on, chances are high that after only 1 or 2 years of the surgery symptoms start to return as the fibrocartilage wears away, forcing the patient to reengage in articular cartilage repair. This is not always the case and microfracture surgery is therefore considered to be an intermediate step.

The effectiveness of cartilage growth after microfracture surgery is dependent on the patient's bone marrow stem cell population. Increasing the number of stem cells increases the chances of success. Current focus of therapy along these lines is to implant autologous mesenchymal stem cells directly into the cartilage defect, without having to penetrate the subchondral bone.

Mosaicplasty:

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Osteochondral autograft transplantation surgery (OATS), also called mosaicplasty, is a technique to remove healthy plugs of bone and articular cartilage from one area of the knee (where it is required less) and to put them into the damaged area.

Cartilage Transplant:

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This requires two surgeries. The first surgery is an arthroscopy to evaluate the lesion and obtain a biopsy of cartilage. The biopsy allows your specific cartilage cells to be grown and re-implanted at the second operation, usually 6 weeks to 3 years after the original surgery.

Currently, the implantation technique requires an open rather than an arthroscopy. The first part of the surgery is to trim the defect to a stable rim and clear the bony base. A copy of the defect is made from sterile paper and used to trace out the desired cut for harvesting a periosteal patch from the proximal tibia. The periosteum is the living tissue on the outside of bone. This is then sutured onto the defect and the cells are placed within this "pouch".

The rehabilitation is long and demanding. Individual regimes vary with some centers recommending early motion while others immobilize the knee in plaster for three weeks. Patients are typically allowed to put weight on their operated leg after eight weeks. Physical therapy is continued for up to 12 months, and sporting activities are curtailed during this time.

Results

Autologous chondrocyte transplants were introduced in Sweden in 1987 with the first results published in 1994. The original results were encouraging with an excellent outcome in 88% of patients (with isolated femoral defects) at 32 months.

At present the two main groups publishing results are the Swedish group led by one of the pioneers, M. Britberg, and the U.S.A.-based Genzyme group.

The Swedish published their two to nine year follow up of over 100 patients last year. They evaluated outcome on based patient and physician clinical outcome scales, appearance at arthroscopy and microscopic analysis. The clinical results were good to excellent in a different proportion depending on the indications:

Isolated femoral condyle defects 92%
Ostoechondritis dissecans 89%
Patella 65%
Femoral condyle defects with A.C.L. repair 75%