Titanium for Orthopedic Applications: An Overview of Surface Modification to Improve Biocompatibility and Prevent Bacterial Biofilm Formation

Abstract

Titanium and its alloys have emerged as excellent candidates for use as orthopedic biomaterials. Nevertheless, there are often complications arising after implantation of orthopedic devices, most notably prosthetic joint infection and aseptic loosening. To ensure that implanted devices remain functional in situ, innovation in surface modification has attracted much attention in the effort to develop orthopedic materials with optimal characteristics at the biomaterial-tissue interface. This review will draw together metallurgy, surface engineering, biofilm microbiology, and biomaterial science. It will serve to appreciate why titanium and its alloys are frequently used orthopedic biomaterials and address some of the challenges facing these biomaterials currently, including the significant problem of device-associated infection. Finally, the authors shall consolidate and evaluate surface modification techniques employed to overcome some of these issues by offering a unique perspective as to the direction in which research is headed from a broad, interdisciplinary point of view.

Keywords: Biomaterials; Microbiofilms; Orthopedics; Surface Science.

Figure 1

Common Causes of Orthopedic Failure

Figure 2

Components of a Total Hip Arthroplasty

Figure 3

Factors Affecting the Biocompatibility of Titanium

Figure 4

Safety Issues Concerning Elements Commonly Found in Orthopedic Materials

Figure 5

A Comparison between the Elastic Moduli of Various Orthopedic Materials and Cortical Bone ∗Approximate value for CP-Ti

Figure 6

Common Forces of Attraction Experienced between Bacteria and a Solid Surface Namely van der Waals forces (VDW), Electrostatic, Hydrophobic, and Site-Specific Interactions

Figure 7

Schematic Demonstrating the Biofilm EPS and the Heterogenic Nature of Bacteria within a Biofilm

Figure 8

Schematic Showing the Principles Behind Sputtering Physical Vapor Deposition

Figure 9

Basic Principles of a CVD Reactor with a Titanium Substrate Showing the Formation of a Protective Layer (in this case TiO₂)