DOS BULLETIN - Dansk Ortopædisk Selskab

2010-378_DOS nr. 3 2010 29/09/10 10:08 Side 101
Effect on Implant Fixation of Simvastatin Applied
Locally in a PDLLA Coatning
Mette Sorensen, Jørgen Baas, Marianne T. Vestermark,
Joan E. Bechtold, Kjeld Søballe
Orthopardic Research Lab. and Department of Orthopaedics, Aarhus
University Hospital; Orthopaedic Biomechanics Lab, Excelen Center
for Bone and Joint Research and Education, Minneapolis MN USA
Background: About 2% of the population >60 years has a total hip
replacement. A solid initial fixation of the implant improves the longevity
and it is desirable with a stable primary fixation of the implant in
order to avoid revision. Statins acts by inhibiting the HMG coenzyme A
reductase and by increasing the expression of BMP2, a potent growth
factor inducing bone formation in vivo. Local application of statin has
showed to be beneficial in fracture healing and may also improve
implant fixation.
Purpose: We hypothesized that locally applied simvastatin would
improve implant fixation.
Methods: Twelve dogs each received four experimental implants, two in
the proximal part of each humerus. Ti implants measuring 6x10mm were
used. The four groups were: Ti implant, Ti implant+coating, Ti
implant+PDLLA+simvastatin (0.1 mg) and Ti implant+PDLLA+simvastatin
(1.0 mg). All implants were surrounded by a 1.0mm gap. After
four weeks the specimens were prepared for biomechanical push- out
testing yielding max sheer strength, max sheer stiffness and energy
absorption. Statistical analysis by oneway Anova and paired t-test.
Findings: After four weeks the implants coated with PDLLA +/- simvastatin
showed a significant decrease in all biomechanical parameters
compared to the uncoated Ti implants. The implants coated with PDL-
LA+simvastatin showed improved implant fixation compared to the
implant coated with PDLLA alone, most pronounced in the high dose
group, however not significant.
Conclusion: This study indicates that there may be a beneficial effect of
locally applied simvastatin in regards to implant fixation compared to
only PDLLA coated implants but not when comparing to bare Ti
implants. The study also suggests that the biodegradable PDLLA coating
is not appropriate for delivering biological active agents to the
implant-bone interface
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