Status of surface modification techniques for artificial hip implants

Abstract

Surface modification techniques have been developed significantly in the last couple of decades for enhanced tribological performance of artificial hip implants. Surface modification techniques improve biological, chemical and mechanical properties of implant surfaces. Some of the most effective techniques, namely surface texturing, surface coating, and surface grafting, are applied to reduce the friction and wear of artificial implants. This article reviews the status of the developments of surface modification techniques and their effects on commonly used artificial joint implants. This study focused only on artificial hip joint prostheses research of the last 10 years. A total of 27 articles were critically reviewed and categorized according to surface modification technique. The literature reveals that modified surfaces exhibit reduced friction and enhanced wear resistance of the contact surfaces. However, the wear rates are still noticeable in case of surface texturing and surface coating. The associated vortex flow aids to release entrapped wear debris and thus increase the wear particles generation in case of textured surfaces. The earlier delamination of coating materials due to poor adhesion and graphitization transformation has limited the use of coating techniques. Moreover, the produced wear debris has adverse effects on biological fluid. Conversely, the surface grafting technique provides phospholipid like layer that exhibited lower friction and almost zero wear rates even after a longer period of friction and wear test. The findings suggest that further investigations are required to identify the role of surface grafting on film formation and heat resistance ability under physiological hip joint conditions for improved performance and longevity of hip implants.

Keywords: 212 Surface and interfaces; 30 Bio-inspired and biomedical materials; 306 Thin film / Coatings; Surface modification; coating; grafting; hip joint; texturing.

Graphical abstract

Figure 1.

(a) Surface texturing on femoral head [33] and (b) SEM images of different types of fabricated surface texturing.[9]

Figure 2.

Cross section images of deposited (a) a-C:H and (b) Ta-C on stainless steel.[11]

Figure 3.

Friction coefficient results for different prosthesis heads.[11]

Figure 4.

SEM images showing (a) as-deposited DLC-coated surface, (b) formation of film transfer due to load, (c) full delamination of coated materials at higher loads, and (d) wear track on dimpled area.[10]

Figure 5.

Schema of a THA with the PMPC-grafted CLPE liner. A transmission electron microscopy image of the surface is shown on the right. Orange and blue lines indicate the PMPC layer and the liner surface, respectively.[68]

Figure 6.

Graft conformation at various densities of polymer chains.[12]

Figure 7.

Coefficient of dynamic friction of polyelectrolyte-grafted CLPE samples under various lubrication conditions. Data are presented as means ± standard deviations. *Indicates p < 0.05, **indicates p < 0.01, and N.S. indicates no statistical difference.[12]

Figure 8.

Wear mechanism for (a) without dimpled surfaces, (b) smaller depth dimpled surfaces and (c) suitable depth dimpled surfaces.[80]

Figure 9.

Cross-sectional schematic view of the wear mechanism model for (a) DLC-smooth, (b) DLC with higher density (c) DLC with suitable density (d) DLC with lower density.[43]