Biomedical Engineering Reference
In-Depth Information
cartilage.Itismoreandmoreacceptedthatthealteredconditionsin
theboneshouldberestoredatthetimeacartilagerepairprocedure
is performed.
38.3 Current and Recent Approaches to the Field of
Osteochondral Tissue Engineering
Presently there are several clinical approaches to treat cartilage
damage depending on severity, starting with pain medication, anti-
inflammatory treatment, and physical therapy, eventually leading to
surgery over time due to eventual worsening of the condition. The
first surgical approach of choice involves microfracture or subchon-
dral drilling. During these procedures holes are made through the
subchondral bone to evoke bleeding and invasion of stem cells from
the underlying bone marrow. This stimulates repair with fibrous
cartilage. These techniques obviously affect processes in the sub-
chondral bone
15
that may affect cartilage repair. Alternatively, for
cartilage lesions, autologous chondrocyte transplantation is a clin-
ically viable option. In this procedure, first described in patients in
1994 by Brittberg
et al
.,
16
chondrocytes are isolated from cartilage
harvested from a less-weight-bearing site in the joint. After expan-
sion of the number of chondrocytes in culture, the cells are trans-
plantedinthecartilagedefectasasuspension,undereitheraflapof
periosteum or a collagen membrane attached to the cartilage defect
edges. Newer-generation products use seeding of the cells on or
in a scaffold material. This system has been coined matrix-induced
autologous chondrocyte implantation (MACI). In these chondrocyte
transplantation procedures the underlying bone is left untreated.
However, the properties of this bone will have been changed due
to the cartilage defect, as well as will change after the procedure
because cartilage and bone are one entity and changes in one will
evoke adaptational reactions in the other. Although the underly-
ing bone initially did not receive attention, this is changing mainly
due to the fast improvements in magnetic resonance imaging (MRI)
techniques.
17
In the case of larger osteochondral defects, osteochondral grafts
can be used. These grafts can be either allografts (fresh or frozen)
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