Abstract
Introduction
Cementless devices can be designed with varying surface treatments with the hope of achieving osseointegration. The surface finish dictates the interaction, adhesion and growth of bone therefore it is an important parameter that be measured and compared. The surface topography of a material can be viewed both microscopically and macroscopically. Surface microtopography focuses on the peaks and valleys where deviations in the characteristics of the size and spacing of these features determine the variability between surface topography. The most common parameter used worldwide to describe surface roughness is the arithmetic average height (Ra). The definition of Ra is the absolute deviation of the surface irregularities from a mean line across the sampling length given by the equation shown in figure 1.
Many techniques can be used to relate to surface characteristics of materials, with the common two options revolving around contact and non-contact methods. These techniques are expensive and are limited in detecting the interaction of implantable devices at a macroscopic level. This study sought to develop a method to determine the surface roughness and characterise implants based on cross sectional images and scanning electron microscopy.
Method
The profile of 6 trunnions from a total hip replacement was obtained in x and y coordinates along a set length using a profilometer. A custom program to calculate the Ra of the material was created using a mathematical program (MATLAB). Each material profile was inputted into a mathematical program to provide the surface roughness of the material. The surface parameters were initially obtained from a surface analyser to determine the accuracy of the program.
Results
The mean difference in the Ra measurements was 0.2μm ± 0.01μm
Conclusion
This study has shown that the roughness parameters of a material obtained using the custom program was within acceptable variation to the results from the profilometer. This is indicative of the program functioning as required. The surface characteristics of implantable devices are important factors which can influence cellular behaviour hence adhesion which directly correlate to the interaction with bone. Therefore having a method to determine the surface roughness is a vital tool, which can provide insight on the inherent topography.
