Articular Cartilage Restoration
Articular Cartilage
There are two types of cartilage in the knee. The first is
fibrocartilage, which is seen in the meniscus. The second is the
articular cartilage, which covers all bone surfaces in the knee joint.
The function of articular cartilage is to provide a smooth,
low-friction, weight-bearing surface that also acts to protect the
underlying bone.
Articular cartilage is composed of very specialized cells
called chondrocytes. Chondrocytes comprise less than 10% or articular
cartilage dry weight. These cells reside in an extracellular matrix
consisting of collagen, proteoglycan molecules, and water. There are
many types of collagen, but the majority of collagen in articular
cartilage is Type II. The proteoglycans are very large molecules that
bind water. This accounts for the pressure, which makes cellular
cartilage highly resistant to compressive loads. The chondrocytes
provide the metabolic activity to maintain both the cartilage and the
proteoglycans.
This complex structure of articular cartilage results in
essentially no ability to repair itself. The poor healing response is
due to a lack of blood supply in articular cartilage plus the inability
of mature chondrocytes to migrate and reproduce into an area of
damaged articular cartilage.
Articular cartilage damage can result from an acute injury or can be
due to prolonged wear and tear. Acute injury usually results in lesions
that are amenable to cartilage restoration. Routine wear and tear
result in large areas of cartilage wear that are usually not amenable
to articular cartilage restortation procedures.
An important part in the evaluation of patients with articular
cartilage defects is determining which injuries are amenable to
articular cartilage repair and which are not. Approximately 900,000
Americans suffer from articular cartilage injuries per year.
Techniques of Articular Cartilage Repair
- Arthroscopic Debridement and Lavage: This technique simply debrides
unstable articular cartilage from injured surfaces and usually provides
only short-term relief. In small areas of injury, this may produce good
results.
- Marrow Stimulating Procedures (Microfracture): This is an
arthroscopically performed surgical procedure in which drill holes are
placed in the subchondral bone in the articular cartilage defects. This produces a
fibrocartilage repair tissue. The tissue does cover the end of the bone
but because it is not true articular cartilage, it wears less
predictably.
- Autologous Chondrocyte Implantation (ACI): this is a two stage surgical procedure. The first stage consists of obtaining samples
of articular cartilage from the patient's knee. These are grown in a
laboratory. These articular cartilage cells are subsequently implanted
into the patient's knee via an open surgical procedure. This method
produces a covering more like the articular cartilage, but it still has
some of the elements of fibrocartilage.
- Osteochondral Autograft: This is an arthroscopic or open
surgical procedure in which plugs of the patient's own articular
cartilage and underlying "donor" bone are removed from areas in the patient's
knee and reinserted into the articular cartilage defect. This results
in normal hyaline cartilage in the defect at the cost of creating an
articular cartilage defect in another area of the knee.
- Osteochondral Allograft: This is an open surgical procedure in
which articular cartilage and underlying bone are taken from a cadaver.
This graft is used to fill the defect in the patient's articular
cartilage. This results in articular cartilage in the defect, but there
may be incomplete survival of the chondryocytes in the graft.
Many factors such as size of the injured area, patient's
age, patient's level, and leg alignment, etc. are used to decide which
procedure is utilized.
Dr. DeLee has experience in all types of cartilage restoration
and provides state-of-the-art patient education, research, and surgical
treatment.
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