TITLE:
Biomimetic Hydroxyapatite Coated Titanium Screws Demonstrate Rapid Implant Stabilization and Safe Removal In-Vivo
AUTHORS:
Jan Henrik Sörensen, Lutz Dürselen, Ken Welch, Torben Christian Sörensen, Philip Procter, Håkan Engqvist, Maria Strømme, Anita Ignatius, Hartwig Steckel
KEYWORDS:
Biomimetic Hydroxyapatite, In-Vivo, Screw, Implant Removal, Pull-Out Force, Removal Torque
JOURNAL NAME:
Journal of Biomaterials and Nanobiotechnology,
Vol.6 No.1,
January
6,
2015
ABSTRACT: The early fixation of bone screws after surgical implantation still remains a challenge in the field
of traumatology. Whilst hydroxyapatite (HA) coatings are known to enhance the fixation of implants;
their removal at a later time-point may be problematic. An HA coating has been developed
to demonstrate that both implant fixation and safe removal are feasible in the same design. Accordingly
the aim of this study was to compare the In-Vivo performance of thin biomimetic HA coated
titanium screws to uncoated counterparts used as control after bilateral implantation in the femoral
condyle of 36 New Zealand White Rabbits. The screws were analysed macroscopically, by
histology, micro-CT and biomechanically at both two and six weeks post-implantation. The HA
coated screws demonstrated excellent biocompatibility. At two weeks the HA coated screws demonstrated
a significant increase in removal torque values as well as a strong trend towards higher
pull-out forces. In addition histology confirmed a higher degree of osseointegration and direct
bone to implant contact. At six weeks no difference in pull-out force and removal torque could be
detected. SEM images confirmed the absence of any residual HA coating indicating a fast coating
degradation In-Vivo. The low level of removal torque after full osseointegration at 6 weeks supports
the feasibility of safe and easy removal of the implant. The HA coating under study appears to offer a unique characteristic of enhanced fixation with a minimal increase in removal torque
after full osseointegration. This may be of value in clinical applications where it is necessary to
assure both screw fixation and later removal.