Biomedical Engineering Reference
In-Depth Information
of lesions of clinically-relevant volumes enhancing model relevance in
a preclinical setting.
The most commonly used designs in the field of bone tissue
engineering are surgically induced bone defects that are known to
progress to non-healing if not replaced. The notion of a critical size
defect (CSD) was first described for bone by Schmitz as “the smallest
intra-osseous wound that does not heal by bone formation during the
lifetime of the animal” [SCH 85]. The bone CSD must be created
under conditions of optimal mechanical stability in order to guarantee
that non-union results exclusively from bone loss. Because its size is
species and age dependant, it must be determined each time an
unpublished, new CSD is used to evaluate a TEC [VIA 04, VIA 99,
TOO 85]. Preclinical studies for cartilage tissue engineering also rely
on the creation of cartilage defects, most of which are performed on
the femoral condyles. These defects are usually performed on mini-
pigs, goats, sheep and horses in which cartilage is thicker and in which
larger lesions can be performed thus enhancing clinical relevance
[CHU 10]. Currently used models in the field of ligament or tendon
engineering have been described in goats, sheep and mini-pigs. They
are based on intra-articular replacement of the Anterior Cruciate
Ligament (ACL) [VIA 13a], repair procedures of patellar, Achilles or
rotator cuff tendon lesions [HAS 14]. The larger animal species allow
the use of operative techniques similar to the ones used in humans,
enhancing model relevance in a preclinical setting.
Experimental design and associated effects must not only be
correlated in the laboratory animal but also in human surgical
applications. Animal anatomy, bone healing and remodeling
specifications, as well as immunological and genetic status, condition
model relevance.
Anatomical features
The choice of the anatomical region in which the TEC will be
tested will be different depending on its future clinical applications.
Calvarias (i.e. membranous bone) will be preferred if the material is to
be used in cranioplasties or iliac reconstructions while metaphyseal
extremities (i.e. trabecular bone) or diaphysis (i.e. cortical bone) will
