|
Bone Allograft
- a bone graft donated by one human being for transplantation
into another. |
| Lyophilisation
- process of rapid freezing of bone grafts to below
-75°C by direct sublimation of ice under vacuum.
Freeze-drying destroys DNA that can initiate an
immune response in recipients. Moisture is simultaneously
extracted from the grafts. This whole process takes
place over a period of 4 days. Lyophilised grafts
can be stored at room temperature. |
| Demineralisation
- Process whereby the mineral components of bone
are dissolved in order to expose bone morphogenetic
proteins. It is only effective for small, non-weightbearing
allografts. |
| Bone
Morphogenetic Proteins (BMP's) - Natural
inducers of osteogenisis (bone growth). These proteins,
especially BMP-3 or osteogenin, can induce undifferentiated
progenitor cells around them to differentiate into
chondrocytes. Bone is formed subsequently through
the natural process of endorchondral ossification.
BMP is thus the name given to the biologically active
components of normal bone that innitiate this process
and induce bone formation. |
| Osteogenesis
- Process of bone growth and regeneration. Includes
osteoconduction and osteo-induction. |
| Osteoinduction
- Recruitment of mesenchymal stem cells from the
surrounding bed, and their differentiation into
osteoblasts. The recruitment and differentiation
of cells are modulated by bone morphogenetic proteins.
The activity of BMP does not require viable graft
cells. It is present not only in autografts, but
also in modified allografts. |
| Osteoconduction
- 3-Dimensional structural scaffold to allow for
the ingrowth of capilliaries, perivascular tissue
and osteoprogenitor cells of the host into the graft.
The scaffold itself is not osteoinductive and therefore
cannot initiate bone formation. |
| Osteoblasts
- Bone cells that develop in the embryonic mesenchyme
during early skeletal development. It differentiates
from a fibroblast to function in bone tissue formation.
Osteoblasts synthesise collagen and glycoproteins
to form the bone matrix. Later they can become osteocytes. |
| Osteoclasts
(also known as Osteophages)
- Multinucleated bone cells associated with the
breakdown and reabsorption of osseous tissue through
enzymatic action. They are active in periods of
development and growth and in the presence of parathyroid
hormone.They are also known as osteophages. |
| Human
Allograft Bone - Bone procured from a
donor patient for grafting onto another patient
in need of bone grafting. The use of Allograft or
"banked" bone obviates the need for harvesting of
autologous bone. Fresh frozen or gamma-irradiated
bone still contains BMP's and is therefore both
osteoinductive and osteoconductive. |
|
Autologous Bone - patient's own bone
normally harvested by creating a second wound on
the patient's illiac crest. This is often the source
of more discomfort to the patient than the primary
operation site. This is, however, the ideal bone
graft since it contains BMP's as well as live osteoblasts. |
| Heterogenous
bone grafts - Xenografts or heterografts
are supplied by a non-human subject, usually animals
eg. Bovine surgibone. It may also come from another
source eg. Coral grafts. These grafts undergo tretment
to reduce any inherent antigenic properties. There
are no BMP's present in these grafts. They are not
osteo-inductive, only osteoconductive. |
