47.
Accelerated bone growth, but weaker implant fixation in allograft
mixed with nano-hydroxyapatite.
Lau Lind Petersen, Jeppe Barckman, Jørgen Baas, Mette Sørensen, Joan E.
Bechtold, Kjeld Søballe
Orthopaedic Research Laboratory Aarhus University Hospital; Department of
Orthopaedic Surgery, Aarhus University Hospital; Department of Orthopaedic
Surgery, Aarhus University Hospital; Department of Orthopaedic Surgery,
Aarhus University Hospital; Minneapolis Medical Research Foundation,
University of Minnesota; Department of Orthopaedic Surgery, Aarhus
University Hospital
Background:
Impaction grafting is a well-established method for optimizing
inadequate bone- stock seen in hip revision surgery. However, joint
replacement surgeons are still challenged in achieving early implant fixation,
which is crucial to prosthesis longevity. Nano-Hydroxyapatite (nHA) has been
shown to be a highly osteoconductive mineral and is widely used in many
kinds of bone replacement surgery.
Purpose / Aim of Study:
We hypothesized that augmenting allograft bone by
adding nHA would improve osteoconductivity of the allograft bone and
thereby improve implant fixation.
Materials and Methods:
We conducted a double, paired study including 12
dogs. Each animal received 4 implants surrounded by a 2.5mm gap in the
distal femur. The gaps were impacted with allograft with or without Ostim®
(
nHA paste) from one of the 4 groups: Control 1 vs. nHA Low (5% Ostim®)
in the lateral side and Control 2 vs. nHA High (20% Ostim®) in the medial
side. Observation time was 4 weeks. Upon euthanasia, mechanical and
histomorphometric analyses were made.
Findings / Results:
There were no statistical differences in any of the
mechanical parameters except for 9% less stiffness (p=0.012) in High-dose
nHA group compared to the control. In the nHA High group there was 8%
more new bone in the gap (p=0.0008) and on the surface of the implant (p =
0.011).
Conclusions:
Within the limits of this model, we show that nHA mixed with
allograft has inferior mechanical stability, but has a higher proportion of new,
woven bone.
