The effects of novel bone substitutes on posterior lateral
lumbar spine fusion in normal and osteoporotic sheep
Phd project by Martin Axelsen
Spine fusion, spondylodesis, is defined as bone intervertebral fusion achieved after
surgical manipulation. Spinal fusion is indicated for a wide range of diseases as
degenerative spinal diseases, pain, tumor, deformities and trauma. Most often spinal
fusion is done in the lumbar spine region and is based on degenerative disease or pain
problems.
To achieve solid bone formation between vertebral bones, graft materials are used.
Traditionally fusion has been done using autograft or allograft bone materials in an
uninstumented or instrumented posterior lateral fusion model.
Graft material is needed to obtain vertebral fusion. Autograft from iliac crest is
considered to be gold standard. This possesses osteoinductive, conductive and
osteogenitic properties. Because of graft harvesting limitations and patient donor site
morbidity as pain, bleeding and infection alternatives is of highest interest.
In this Phd project we will evaluate a new bone graft material and compare it to allograft
in a sheep model. The graft material will bee evaluated with and without additional Bone
marrow aspirate to induce better osteogenetic material properties. Further it will be
evaluated in a sheep osteoporotic model to simulate the clinical situation where spine
fusion often is done in the elder population with reduced bone healing
.
Several composite materials have previously been investigated. P-15-BGS is a recently
investigated composite material consisting of an organic bovine derived hydroxyapatite
matrix and P-15 a synthetic derived 15-aminoacid peptide with an identical sequence as
found in the cell binding domain in collagen Type-1 (α-chain). This combination of
materials is suggested to be osteoconductive with release of necessary minerals and
providing three-dimensional matrix and osteoinductive (P-15) by providing biding site
for α2-β1 integrin on the surface of bone forming cells. The binding of α2β1-integrins to
P-15, initiates natural intra- and extracellular signalling pathways, inducing the
production of growth factors, bone morphogenic proteins and cytokines . This composite
material has proven to stimulate bone formation, but it has not yet been compared to
todays clinical practice - allograft. Further P-15-BGS has not been investigated in an
osteoporotic model simulating clinical setups.
The use of graft materials in orthopaedic surgery is increasing. The demand for new
materials that reassemble today’s gold standard but without the patient morbidity and risk
from autograft is highly wanted. This study evaluates such a material prior to clinical use.