52.
Incorporation of Raloxifene-impregnated Allograft around
Orthopaedic Titanium Implants
Lars Lykke Hermansen, Mette Sørensen, Jørgen Baas, Jeppe Barckman, Joan
E. Bechtold, Kjeld Søballe
Ortopædkirurgisk Forskningslaboratrium Aarhus Universitetshospital,
Nørrebrogade 44, Bygn. 1A, 8000 Aarhus C; Ortopædkirurgisk
Forskningslaboratrium, Aarhus Universitetshospital, Nørrebrogade 44, Bygn.
1
A, 8000 Aarhus C; Ortopædkirurgisk Forskningslaboratrium, Aarhus
Universitetshospital, Nørrebrogade 44, Bygn. 1A, 8000 Aarhus C;
Ortopædkirurgisk Forskningslaboratrium, Aarhus Universitetshospital,
Nørrebrogade 44, Bygn. 1A, 8000 Aarhus C; Orthopaedic Biomechanics
Laboratory, Minneapolis Medical Research Foundation, University of
Minnesota and Excelen Center for Bone & Joint Research and Education,
Minneapolis, Mi; Ortopædkirurgisk Forskningslaboratrium, Aarhus
Universitetshospital, Nørrebrogade 44, Bygn. 1A, 8000 Aarhus C
Background:
Due to peri-implant osteolysis, hip revisions are a more
complex procedure compared to primary hip arthroplasties. Early fixation of
revision prosthesis is crucial to its long- term survival. The anti-osteoporotic
drug Raloxifene decreases the risk of vertebral fractures by maintaining bone
mass density. The mechanism of action by Raloxifene is purportedly by
inhibition of the recruitment and activation of osteoclasts.
Purpose / Aim of Study:
We investigated whether Raloxifene offers any
benefits in augmenting early fixation of orthopaedic implants in the setting of
impaction bone grafting. Our hypothesis was that Raloxifene-impregnated
morselized cancellous allograft bone would increase early implant fixation
compared to normal, untreated morselized cancellous allograft.
Materials and Methods:
We used a non-weight-bearing gap model in 12
dogs. The 2.5-mm peri-implant gap was filled with either Raloxifene-
impregnated or untreated bone allograft. The implants were harvested after an
observation period of 28 days. Implant fixation was assessed by mechanical
testing and histomorphometrical evaluation.
Findings / Results:
Raloxifene-treated allograft significantly decreased early
implant fixation compared to untreated allograft illustrated by inferior
maximum shear strength (p<0,01) and apparent shear stiffness (p<0,01). This
result was explained by a significantly higher amount of new bone formation
(
p<0,02) accompanied with accelerated allograft resorption (p<0,03) in the
Raloxifene-treated group.
Conclusions:
A similar trend has earlier been demonstrated when treating
bone grafts with BMPs in spite of an apparently dissimilar mechanism of
action. Our finding entails a need of redefining the theory of how Raloxifene
exert its actions on bone tissue by extending its repertoire from solely anti-
catabolic to including anabolic properties dose-dependently.
