Biomedical Engineering Reference
In-Depth Information
Fig. 1
Phases of bone healing [ 50 ]
•The hard callus stage lasts approximately 4 weeks [ 19 ] and ends with the bone
fragments union by immature bone. Initially, the callus is formed by cartilage
tissue predominately, with some areas of intramembranous ossification. In this
phase, mineralization occurs although with a rhythm much slower than the
preceding phases. The type of mineralization depends on the existing tissue
within the soft callus, either intramembranous or endochondral ossification.
•The remodeling phase lasts approximately 1-4 years [ 19 , 22 ] and consists of
two phases. During the former, internal remodeling occurs and the immature
bone is replaced by lamellar bone. During the latter, which is slower, external
remodeling occurs, the size of the callus diminishes and the bone recovers its
original shape.
3.2
Distraction Osteogenesis
Distraction osteogenesis is a unique biologic process of new bone formation
between the surfaces of bone segments that are gradually separated. Under the
influence of the tensional stress, the soft callus is maintained at the center of
the distraction gap while routine fracture healing occurs at the periphery of the
regenerate [ 63 ]. Many tissues besides bone have been observed to form under
tension stress, including mucosa, skin, muscle, tendon, cartilage, blood vessels, and
peripheral nerves [ 17 , 34 , 35 ]. Therefore, distraction osteogenesis as well as bone
healing involve a process of continuum tissue formation.
In the distraction process, there are five fundamental sequential phases in which
different biologic phenomena are produced (Fig. 2 ):
Osteotomy . In this phase the bone is surgically divided into two segments,
resulting in a loss of continuity and mechanical integrity. Bone fragments are
then fixed by means of a distractor/external fixator to stabilize the new created
gap [ 37 ].
Search WWH ::




Custom Search