Abstract
Background
Medical applications of nanotechnology are promising because it allows the surface of biomaterial to be tailored to optimise the interfacial interaction between the biomaterial and its biological environment. Such interfaces are of interest in the domain of orthopaedic surgery as they could have anti-bacterial functions or could be used as drug delivery systems. The development of orthopaedics is moving towards better integration of biology in implants and surgical techniques, but the mechanical properties of implanted materials are still important for orthopaedic applications. During clinical implantation, implants are subjected to large mechanical stresses. In order to obtain the best performance during clinical use, mechanical properties of implants need to be investigated and understood.
Method
We modified the topography of commercial titanium orthopaedic screws using electrochemical anodization in a 0.4 wt% hydrofluoric acid solution to produce titanium dioxide nanotube layers. The morphology of the nanotube layers were characterised using scanning electron microscopy. The mechanical properties of the nanotube layers were investigated by screwing and unscrewing an anodized screw into several different types of human bone while the torsional force applied to the screwdriver was measured using a torque screwdriver. The range of torsional force applied to the screwdriver was between 5 and 80 cN·m. Independent assessment of the mechanical properties of the same surfaces was performed on simple anodized titanium foils using a triboindenter.
Results
The fabricated nanotube layers can resist mechanical stresses close to those found in clinical situations.
Conclusion
The mechanical characteristics of this surface treatment appear to be sufficiently robust to withstand realistic clinical operating conditions that our in vitro experiments were designed to simulate. These results show that the nanotube layers remain intact after the implantation process. This may allow for the exciting possibility of nanotubes being loaded with molecules.
Level of Evidence
II
