Biomedical Engineering Reference
In-Depth Information
allowing assessment of full and partial thickness cartilage defects
averaging the sizes of those that are of greatest clinical interest for
humans. Further, second look arthroscopic evaluation of the knee joint
is also possible in this species [CHU 10].
Healing and remodeling characteristics
Tissue healing and remodeling characteristics in laboratory animal
depend on many variables such as blood supply, mechanical loading
and most importantly, species or age dependent variables.
Species-dependant healing modalities are especially true for bone
healing. Genetic variation in bone-regenerative capacity has been
observed among inbred strains of mice [LI 01]. Moreover, order along
the phylogenetic scale inversely correlates with the rate of bone repair:
bone healing capacity is thus higher in rodents and rabbits than in
other species [SCH 85]. The type and rate of bone remodeling also
differ amongst species. Whereas large animals (rabbits, cats, dogs,
pigs and non-human primates show Haversian-type remodeling in
cortical bone, rodents do not [BEL 00]. Cortical bone remodeling in
rabbits is also twice as fast as in dogs and three times as fast as in
humans [SAL 97]. These features must be taken into account as they
may affect material resorption: natural coral resorption is for example
slower in sheep than in pigs [GUI 89].
Immature animals have higher bone healing capacity and
regeneration compared to adults. Mice and rats remain exceptions to
that rule as bone growth is constant throughout life in these species
[BEL 00]. The magnitude of a bone CSD is inversely related to the
age of the animal and bone substitutes must be evaluated in adult
animals in which closed epiphyseal plates are documented with
radiographs [TOO 85]. Age-dependant variables must also be taken
into account for cartilage healing. Germinal cells from the physis may
indeed supply regenerating cartilage and alter the study results. If the
affected joint is surrounded by open growth plates, these can interfere
with the applied treatment [CHU 10]. The presence of open growth
plates through advancing age thus likely increase the intrinsic healing
potential of osteo-chondral defects in rodents that confound repair and
regeneration studies in these models. For all these reasons, while
