1. Wear Performance of Ultra-High Molecular Weight Polyethylene on Oxidized Zirconium Total Knee Femoral Components by Myron Spector, Michael D. Ries, Robert B. Bourne, Willard S. Sauer, Marc Long, and Gordon Hunter J Bone Joint Surg Am Volume 83(2 suppl 2):S80-86 November 1, 2001 ©2001 by The Journal of Bone and Joint Surgery, Inc.

2. In a previous study, condyle surface roughness was found to be greater for retrieved cobalt- chromium femoral components than for components that had not been implanted4,5. Myron Spector et al. J Bone Joint Surg Am 2001;83:S80-86 ©2001 by The Journal of Bone and Joint Surgery, Inc.

3. Under clinical conditions, cobalt-chromium femoral components develop scratches, some of which are oriented at an angle to the direction of motion, as seen on this interferometer image of a retrieved clinical specimen4,5. Myron Spector et al. J Bone Joint Surg Am 2001;83:S80-86 ©2001 by The Journal of Bone and Joint Surgery, Inc.

4. Hard particles scratch cobalt-chromium surfaces, plowing up adjacent peaks that can increase abrasive wear of ultra-high molecular weight polyethylene, as seen on this interferometer image of a retrieved clinical specimen4,5. Myron Spector et al. J Bone Joint Surg Am 2001;83:S80-86 ©2001 by The Journal of Bone and Joint Surgery, Inc.

5. Oxygen naturally diffuses into the zirconium alloy when it is heated in air, causing the original metal surface to transform to zirconium oxide (zirconia) ceramic. Myron Spector et al. J Bone Joint Surg Am 2001;83:S80-86 ©2001 by The Journal of Bone and Joint Surgery, Inc.

6. Testing was conducted on a six-station, four-axis, physiological knee simulator. Myron Spector et al. J Bone Joint Surg Am 2001;83:S80-86 ©2001 by The Journal of Bone and Joint Surgery, Inc.

7. A 90% normal gait and 10% stair-climbing activity pattern was simulated in this study. Myron Spector et al. J Bone Joint Surg Am 2001;83:S80-86 ©2001 by The Journal of Bone and Joint Surgery, Inc.

8. Cobalt-chromium produced an aggregate wear rate of 4.68 ± 2.30 mm3/Mcycle after the wear-in period. Myron Spector et al. J Bone Joint Surg Am 2001;83:S80-86 ©2001 by The Journal of Bone and Joint Surgery, Inc.

9. Oxidized zirconium produced an aggregate wear rate of 0.69 ± 0.52 mm3/Mcycle after the wear-in period. Myron Spector et al. J Bone Joint Surg Am 2001;83:S80-86 ©2001 by The Journal of Bone and Joint Surgery, Inc.

10. Compared with cobalt-chromium, oxidized zirconium was associated with less ultra-high molecular weight polyethylene wear. Myron Spector et al. J Bone Joint Surg Am 2001;83:S80-86 ©2001 by The Journal of Bone and Joint Surgery, Inc.

11. The ultra-high molecular weight polyethylene wear rate was 85% less for oxidized zirconium than for cobalt-chromium (regression and standard error). Myron Spector et al. J Bone Joint Surg Am 2001;83:S80-86 ©2001 by The Journal of Bone and Joint Surgery, Inc.

12. Oxidized zirconium tended to produce somewhat fewer submicrometer-sized polyethylene wear particles than did cobalt-chromium. Myron Spector et al. J Bone Joint Surg Am 2001;83:S80-86 ©2001 by The Journal of Bone and Joint Surgery, Inc.

13. The mean wear particle volume produced by oxidized zirconium tended to be less than that produced by cobalt-chromium (mean and standard deviation). Myron Spector et al. J Bone Joint Surg Am 2001;83:S80-86 ©2001 by The Journal of Bone and Joint Surgery, Inc.

14. All six tibial inserts exhibited burnishing consistent with adhesive and mild abrasive wear, as seen on this insert from the cobalt-chromium group. Myron Spector et al. J Bone Joint Surg Am 2001;83:S80-86 ©2001 by The Journal of Bone and Joint Surgery, Inc.

15. Scratches were observed on the cobalt-chromium femoral components (Fig. 14-A) but not on the oxidized zirconium femoral components (Fig. 14-B). Myron Spector et al. J Bone Joint Surg Am 2001;83:S80-86 ©2001 by The Journal of Bone and Joint Surgery, Inc.

16. Scratches were observed on the cobalt-chromium femoral components (Fig. 14-A) but not on the oxidized zirconium femoral components (Fig. 14-B). Myron Spector et al. J Bone Joint Surg Am 2001;83:S80-86 ©2001 by The Journal of Bone and Joint Surgery, Inc.

17. Figs. 15-A, 15-B, and 15-C The roughness of the cobalt-chromium condyles increased about five to ten times, whereas the oxidized zirconium condyles remained smooth. Myron Spector et al. J Bone Joint Surg Am 2001;83:S80-86 ©2001 by The Journal of Bone and Joint Surgery, Inc.

18. Figs. 15-A, 15-B, and 15-C The roughness of the cobalt-chromium condyles increased about five to ten times, whereas the oxidized zirconium condyles remained smooth. Myron Spector et al. J Bone Joint Surg Am 2001;83:S80-86 ©2001 by The Journal of Bone and Joint Surgery, Inc.

19. Figs. 15-A, 15-B, and 15-C The roughness of the cobalt-chromium condyles increased about five to ten times, whereas the oxidized zirconium condyles remained smooth. Myron Spector et al. J Bone Joint Surg Am 2001;83:S80-86 ©2001 by The Journal of Bone and Joint Surgery, Inc.