Metal-on-metal bearings have been established in total hip replacements but, more recently, have been developed with modifications for artificial discs. The significance of these modifications is not known. In this study, analytical tools were used to predict the effects of cup depth, clearance, motion, and load on wear of metal-on-metal artificial lumbar discs. Then, laboratory wear simulators were developed. The first series of wear simulations determined the effects of the differences between artificial hips and discs on wear by comparing the effects of motion, load, and cup design; the second compared the effects of metallurgy and cup design; and the third compared the effects of different motion and load profiles on wear of two designs of discs. From the analytical tools, the larger maximum contact pressure, lower lubrication, and smaller cross-path angles predicted more wear for metal-on-metal discs compared to hips; however, the smaller sliding distance predicted less wear. The majority of analyses predicted more wear of artificial discs than hips, emphasizing the importance of considering the effects of dimensional and biomechanical differences on wear. From the first series of wear simulations, decreasing the magnitudes of motion and load from hip to lumbar spine increased the wear; changing the phasing of motion from hip to lumbar spine reduced the wear; and decreasing the cup depth from artificial hip to disc increased the wear. The overall increase in wear supported the predictions from the analytical tools that artificial discs wear more than hips. From the second series of wear simulations, changing the carbon content of the ball from low to high, eliminating the anteroposterior keels, and decreasing the initial clearance reduced the wear; removing the surgical notch further reduced the wear. These reductions in wear emphasized the importance of considering the effects of individual design variables on wear. In the third series of wear simulations, changing the motion and load profile from gait to high-motion activities increased the wear for both artificial discs; however, the effect on the ball-to-cup wear ratios was different for each design, emphasizing the importance of considering the effects of the testing profile in wear simulations.... operated by different individuals: ac Mitutoyo CMM with a 2-mm ruby stylus and QUALSTAR software ac Mitutoyo CMM with an 0.5-mm stylus and M Cosmos software ac Zeiss Contourecord ac Mitutoyo FormTracer CS-3000 with a 4I¼m 60Ad conicalanbsp;...
|Title||:||Wear of Metal-on-metal Artificial Discs for the Lumbar Spine|
|Author||:||Jessica Lynn Lee|
|Publisher||:||ProQuest - 2007|