Medical implants are devices or tissues designed to replace, support, or enhance structures in the body. Many implants are coated with drugs, disperse medications, or have a characteristic surface for tissue adhesion. Some implants are made from skin, bone or other body tissues, while others are made from metal, plastic, ceramic or other materials.
When medical devices are made from metal or other synthetic material, surface contaminants can be introduced during the manufacturing processes such as milling, turning, polishing, lapping, and de-burring. Intermediate cleaning stages or laser treatment may be employed. Additionally, any device implanted in the body must be completely sterile; an implant with a contaminated surface can cause infection or be rejected by the body. Surface analysis is extremely important to know if the cleaning regime following implant manufacturing is successful, and identify any remaining contaminants.
Bulk analytical techniques can miss low levels of surface contamination, but X-ray Photoelectron Spectroscopy (XPS), also known as Electron Spectroscopy for Chemical Analysis (ESCA), is ideally suited to investigate component cleanliness after manufacturing because it has a high degree of surface sensitivity.
XPS is a technique that identifies and quantifies the elements present on a surface and their chemical state. XPS works by irradiating the surface of a material with x-rays and detecting the electrons that are ejected from the surface. This is known as the photoelectric effect, discovered by Hertz in the 19th century, and explained by Einstein in a 1905 paper. The photoelectrons have a unique kinetic energy, which is related to the characteristic binding energy of the element, as well as the orbital and chemical environment of the atom. Because of the strong interaction of electrons with solid materials, only electrons generated near the surface can escape without losing too much energy. By measuring the kinetic energy using XPS, we can learn a great deal about a material’s surface.
A recent webinar demonstrated how XPS can be used to determine if the cleaning regime at the end of an implant manufacturing process was successful. A fixing for a medical implant was evaluated. The fixing had numerous surfaces, so measurements of the surface were taken and contamination levels were checked at representative positions. The thread root appeared to be clear of contamination, but metal chloride, chloro-carbon compounds, and other hydrocarbon contamination were detected at the thread crest and molybdenum disulfide residue was found away from the thread areas at the tip and on the head of the fixing. This information was used to improve cleaning processes and handling procedures.
To see complete test data, including the correlation curves, repeatability data, methodology, and comments, view XPS Simplified: Understanding Metal Surfaces and Oxides with X-ray Photoelectron Spectroscopy (XPS).