Author(s)

Jan Henrik Sörensen¹, Lutz Dürselen², Ken Welch³, Torben Christian Sörensen⁴, Philip Procter⁵, Håkan Engqvist⁶, Maria Strømme³, Anita Ignatius², Hartwig Steckel^1*

¹Department of Pharmaceutics and Biopharmaceutics, Christian-Albrechts University, Kiel, Germany.
²Institute of Orthopaedic Research and Biomechanics, Centre of Musculoskeletal Research, Ulm, Germany.
³Division for Nanotechnology and Functional Materials, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
⁴Stryker Trauma GmbH, Schönkirchen, Germany.
⁵Stryker Trauma AG, Selzach, Switzerland.
⁶Division for Applied Materials Sciences, The Ångström Laboratory, Uppsala University, Uppsala, Sweden.

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.

Biomimetic Hydroxyapatite, In-Vivo, Screw, Implant Removal, Pull-Out Force, Removal Torque

Sörensen, J. , Dürselen, L. , Welch, K. , Sörensen, T. , Procter, P. , Engqvist, H. , Strømme, M. , Ignatius, A. and Steckel, H. (2015) Biomimetic Hydroxyapatite Coated Titanium Screws Demonstrate Rapid Implant Stabilization and Safe Removal In-Vivo. Journal of Biomaterials and Nanobiotechnology, 6, 20-35. doi: 10.4236/jbnb.2015.61003.