Effect of Pigmentation on the Mechanical and Polymerization Characteristics of Bone Cement Peter C. Liacouras, MS, John R. Owen, PE, William A. Jiranek, MD, and Jennifer S. Wayne, PhD Abstract: The impact on performance of additives to bone cement must be assessed before clinical use of the modified product. This study performed several standard acrylic bone cement tests on 3 commercially available products: Endurance, Surgical Simplex P, and Pigmented Endurance. The polymerization characteristics, consisting of doughing time, setting time, and maximum exothermic temperature, were found to be acceptable by the standards of the American Society for Testing and Materials/International Organization for Standards. For the mechanical characterization, analysis revealed statistical equivalence among all cement types, with the exception of compressive strength where Pigmented Endurance was stronger than Surgical Simplex P ( P b .02). In mechanical fatigue, there were no significant differences in the log cycles to failure among the cements; however, Weibull analysis predicted Surgical Simplex P to have a higher characteristic life than the other cements. In conclusion, differences do exist among cement types, but the addition of pigment to Endurance did not alter its performance. Key words: polymethylmethacrylate, curing properties, acrylic bone cement, implant material, mechanical properties. n 2006 Elsevier Inc. All rights reserved. Since its inception in the orthopedic industry, bone cement has revolutionized the field of total joint arthroplasty. Although the major components have remained virtually unchanged, additives have been incorporated into bone cement for various purpo- ses. Radiopacifiers such as barium sulfate and zirconium dioxide enable the cement to be visible on x-ray for follow-up and diagnostic purposes. The addition of antibiotics can prevent bacterial infec- tions. Incorporating a pigment produces cement with coloration, allowing the cement to be distin- guished from surrounding bone. Although clinically beneficial, additives might alter the polymerization characteristics and/or mechanical behavior of bone cement. Any alter- ation may impact the cement’s performance in vivo. Thus, any bone cement modified by an additive must be reevaluated to determine whether physical or mechanical differences result and whether the differences, if negative, outweigh the clinical benefit. Color additives have been in use for over 30 years. Palacos, introduced in 1967, and Osteopal (Heraeus Kulzer, GmbH, distributed in the United States by Biomet Inc, Warsaw, Ind) have incorporated chlorophyll to achieve a light green pigmentation [1]. Studies have shown that the addition of sterile 1-mL vials of methylene blue to the powder portion in the preparation of Surgical Simplex P (Howmedica International S de RL, The Journal of Arthroplasty Vol. 21 No. 4 2006 606 From the Orthopaedic Research Laboratory, Departments of Bio- medical Engineering and Orthopaedic Surgery, Virginia Common- wealth University, Richmond, Virginia. Submitted October 26, 2004; accepted July 7, 2005. Benefits or funds were received in partial or total support of the research material described in this article from DePuy Inc., a Johnson and Johnson Company, Warsaw, IN. Reprint requests: Jennifer S. Wayne, PhD, PO Box 980694, Virginia Commonwealth University, Richmond, VA 23298-0694. n 2006 Elsevier Inc. All rights reserved. 0883-5403/06/1906-0004$32.00/0 doi:10.1016/j.arth.2005.07.006