DOS BULLETIN - Dansk Ortopædisk Selskab

2010-378_DOS nr. 3 2010 29/09/10 10:08 Side 125
Bioreactor activated graft material for early implant
fixation in bone
Susan Snoek Henriksen, Ming Ding, Søren Overgaard
Orthopaedic Research Unit, Dept. of Orthopaedic Surgery and
Traumatology, Odense University Hospital
Background: Combined incubation of a composite scaffold with bone
marrow stromal cells in a perfusion bioreactor, could make up a novel
hybrid graft material with optimal properties for early fixation of bone
to implant.
Purpose: The aim of this study was to create a bioreactor activated graft
(BAG) material, which can induce early fixation of bone to implant, similar
to that of allograft.
Methods: Mononuclear cells were isolated from the bone marrow of 8
female sheep, and injected into a perfusion bioreactor with poly-lactic
acid (PLA 12%) coated scaffold granules (HA/â-TCP). Hybrid material
was incubated in the bioreactor for 2 weeks. Porous titanium alloy
implants (diameter=length=10mm) were inserted bilaterally in each of
the distal femurs of the sheep; thus 4 implants in each sheep. The concentric
gap (2 mm) surrounding the implant was filled with 1) BAG
(autogenous), 2) granules, 3) granules+bone marrow aspirate (BMA,
autologous) or 4) allograft. The sheep were euthanized after 6 weeks.
Push-out tests were performed to assess implant fixation.
Findings: Results were assessed by One-way ANOVA. P-values less
than 0.05 were considered significant. No significant differences regarding
failure energy (kJ/m2, p=0.070) could be seen between the groups.
Shear stiffness (MPa) was significantly higher for the allograft group,
p=0.002. The BAG showed up to 1.5 and 2.4 folds better properties
regarding shear stiffness than the granules alone or the granules+BMA
respectively. The BAG also had up to 1.8 and 5.3 fold higher failure energy
than the granules alone or the granules+BMA respectively.
Conclusion: The present study is the first to show an effect of bioreactor
activated bone substitute on mechanical fixation. However the
mechanical fixation did not reach that of allograft. Probably, an extended
observation time could increase the mechanical fixation of implants
treated with the bioreactor activated graft.
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