Laser marking of implants surfaces is necessary in order to provide traceability during revisions which will help identify product problems more quickly, better execute product recalls and improve patient safety. There are several methods of marking employed within the medical field such as chemical etching, electro pencil marking, mechanical imprinting, casting of markings, marking with vibratory type contact, ink jet, hot foil and screen printing. However, these methods have various drawbacks including marking durability or addition of potentially toxic chemical compounds. As a result laser marking has become the preferred identification process for orthopedic implants. Laser marking is known for its high visual quality, good reproducibility and precision. However there are concerns about the laser marking potential to affect fatigue life of a device. There is a limited number of research papers that studied the effect of laser marking on fatigue life of implants. The objective of the current study is to investigate the effects of laser marking on the fatigue life of titanium alloy material. Two groups of four point bend specimens were used to investigate the effect of laser marking on the fatigue life. The first group comprised of the specimens without laser marking while the second group comprised of specimens with laser marking currently utilized for the implant surfaces. Prior to conducting the fatigue testing, a non-destructive X-ray diffraction (XRD) residual stress analysis was conducted to determine if the laser marking had introduced any residual stresses. Imaging analysis was also conducted to examine any potential surface damage on the test sample's surface. A servo-hydraulic test machine was used for the fatigue four point bend testing regime where the inner and outer spans were 30 mm and 90 mm respectively. All testing was conducted at a frequency of 10 Hz, a stress ratio R=0.1, and sine-wave loading in air. Testing was stopped at 10 Million cycles or at failure of the specimen.Introduction
Material and Methods
Recently there have been case reports of component fractures and elevated metal ion levels potentially resulting from the use of cobalt-chrome modular necks in total hip arthroplasty. One potential cause that has been suggested is fretting corrosion caused by micromotion at the taper junction between the modular neck and the femoral stem. The objective of the current study was to investigate the effects of various impaction and loading methods on micromotion at the modular neck-femoral stem interface in a total hip replacement system. A femoral stem was potted using dental acrylic and displacement transducers were inserted to measure micromotion in the modular neck pocket (Figure 1a). An 8° varus, long, cobalt-chrome, modular neck and 28 mm XXL cobalt-chrome femoral head were inserted in the femoral stem using various assembly techniques (a) hand assembly, (b) impaction loads: 2, 3, 4, 6, 16.4 kN and (c) INTRODUCTION
METHODS
