Biomedical Engineering Reference
In-Depth Information
autologous bone, as well as allogenic and xenogenic grafts, present some
well-known limitations. Thus, non-union of fractures remains a challenging
and important problem in orthopaedic surgery and new approaches to improve
bone bridging when oligotrophic or atrophic non-union problems at present
are required (Pacheco
et all
., 2004; Wraighte and Scammell, 2007).
new materials for the elaboration of structures for tissue engineering and
cell/drug delivery systems able to guide bone repair, to release an adequate
dose of osteoinductive signals and to supply or attract cells capable of
responding to these signals and differentiating into osteogenic cells are
currently under development (Cole
et all
., 2007; Corsi
et all
., 2007).
In the case of fractures related to osteoporosis, one of the major challenges
is the inadequate strength of the bone that must be used to anchor the fixation
device. osteporosis affects metaphyseal bone and, therefore, most osteoporotic
fractures are in the metaphyseal site. This type of fracture is usually treated
by internal fixation; however, owing to the low bone density, the use of
screws to provide a stable fixation is not always possible. In response to
this problem, research and technological development have focused on three
approaches to improve surgery results. These include improved anchoring
techniques, improved load distribution between the bone and the implants
and the augmentation of the strength of the host bone to improve anchorage.
Prosthetic replacement is a fourth approach that is also applicable to many
osteoporotic fractures (Cornell, 2005).
Hence, once more a material able to induce bone formation to reinforce
the host bone and improve anchorage is required. The development of
new low modulus metallic alloys and polymeric devices with mechanical
properties similar to those of osteoporotic bone are also required in order to
get a uniform distribution of loads between the bone and the implants and
avoid further resorption of the bone.
even more challenging than non-unions are problems related to lack
of bone strength and other bone loss defects, found with diseases such as
osteoporosis, osteonecrosis and osteogenesis imperfecta where increased
bone mass, increased bone density, or bone regeneration may be required at
multiple sites. In these cases, biomaterials carriers for genes, cells or drugs
may be very helpful, including biomaterial-mediated gene delivery systems
where a gene carrier is applied directly to cells in culture (
ex vivo
therapy)
or applied to the damaged tissue (
in vivo
therapy), or biomaterial-mediated
drug delivery (Gersbach
et all
., 2007).
Another problem of paramount importance when talking about
musculoskeletal conditions is infection. Musculoskeletal infections are
common, they can affect all parts of the musculoskeletal system, and can be
dangerous and even life threatening. A significant number of bone fractures
are affected by infection problems. In fact, a very common focus of infections
is non-unions. An infected fracture non-union is a disastrous complication.
