Biomedical Engineering Reference
In-Depth Information
designing an animal experiment in large animals for bone and
cartilage studies, skeletal maturity of the animal should be carefully
considered; results in rodents and rabbits should be considered with
caution and validated in other species higher on the phylogenetic scale
before attempting extrapolation to humans.
Biomechanical features
Animal models used in preclinical studies for osteo-articular tissue
engineering purposes cannot truly replicate the biomechanical
conditions in humans. Commonly used laboratory animals are
quadrupeds and subject their bone, joints, tendons and ligaments to
different directions and magnitudes of load than their human
counterparts, making it difficult to replicate the situation observed
clinically. Differences of mechanical loading between species are also
observed and must be taken into consideration when choosing an
animal model and subsequently translating results to human.
Variations observed in the mechanical properties of tissues may
also be observed. Variations observed in the mechanical properties of
bone arise from differences in cross-sectional geometry, relative
proportions of trabecular and cortical bone, amount of mineralization,
degree of porosity and Haversian remodeling [VAN 01]. Interestingly,
specific biomechanical behavior thus correlates more with the
particular shape and function of the bone, the size of the animal and its
lifestyle than with its taxonomic position.
Bone and joint loading affect the biomechanical context of the
healing process. Skeletal unloading in weight bearing bones decreases
the osteoblast number, bone formation rate, bone mineral density, bone
maturation and mechanical strength [KOS 97]. Because joint loading
also varies amongst species, some animal species will be preferred over
others for preclinical studies on cartilage or ligament replacement. For
example, the location of a cartilage defect should be carefully
considered to avoid early overloading. In that respect, the lateral
trochlea of the femur is preferred for cartilage repair and regeneration
studies in the equine model. Sheep and goats, in which the stifle is
carried in a more extended posture (more similar to people), will be
preferred over rabbits and dogs (in which stifle flexion in standing
