Intervertebral total disc replacement (TDR) implants potentially herald a paradigm shift in the management of degenerative disc disease. Preservation of motion may avoid adjacent-segment degeneration, a well- recognized complication of fusion. Based on encouraging experience in Europe and subsequent FDA approvals in 2004 and 2005, the Charity III and ProDisc TDR devices have come into clinical use by many spine surgeons in the US. As an alternative to fusion (~300,000/year in the U.S.), there is substantial interest in increasingly wide usage of this class of devices. However, the potential for late wear-related complications is disconcerting. Both Chariti and ProDisc involve metal-on-conventional-polyethylene bearings, and the TDR patient population is a decade younger than for THR/TKR. Moreover, owing to close proximity of the spinal cord, the potential consequences of implant failure are substantially more dire than for THR/TKR. It is crucial that the scientific community expeditiously confront the issue of TDR wear. A Bioengineering Research Partnership supported by the parent grant is working to provide a firm scientific basis for identifying and dealing with wear-related problems in TDR. This parent grant research (Notice Number NOT-OD-09-058 titled NIH Announces the Availability of Recovery Act Funds for Competitive Revision Applications) involves developing techniques for TDR wear assessment in the pre-clinical phase (Aim 1), implementing a novel technique for in vivo TDR radiographic wear measurement (Aim 2), and assessing the functional biologic activity of TDR wear debris (Aim 3). A revision to the parent grant is proposed to expand and improve upon the computational wear simulation aspects under study in parent Specific Aim 1. The goal of the proposed revision research is to identify methodology by means of which the experimentally-sourced tribologic wear factors used in TDR computational wear simulations can be realistically determined from independently conducted pin-on- plate wear tests, to avoid the need for calibration/linkage to already-performed TDR physical wear simulations. This will open the way to expedited computational simulations of substantively different TDR designs, and to testing of novel hypotheses related to TDR wear, that otherwise would not be possible.
Project Narrative Relevance: Computer simulation of the wear of total disc replacement implants has great usefulness both for engineering design purposes and for surgical assessments. Revision research is proposed for ways to make these computer simulations more accurate and more versatile, by means of better accuracy of one of the key pieces of experimental information (known as the wear factor) needed as input information for these simulations.
