Prospective Clinical Advantages of Trabecular MetalTM Technology Highlighted in Comparative Study
(WARSAW, IN) July 20, 2009—Zimmer Holdings, Inc. (NYSE and SWX: ZMH) today announced that data from a comparative clinical study conducted by researchers at the Mayo Clinic and the Joint Replacement Surgeons of the Indiana Research Foundation describes the low stiffness and osteoconductive properties of Zimmer's Trabecular Metal Technology. The study, published in The Journal of Arthroplasty, found significant reductions in acetabular bone loss adjacent to the Trabecular Metal device compared to the titanium component, and a significant relative increase in bone mineral density (BMD) after total hip arthroplasty (THA) using implants made with Zimmer's proprietary Trabecular Metal Technology.
Researchers followed 17 THA patients over the course of 6 to 9 years and compared bone loss around highly porous Trabecular Metal cups versus titanium cups with a similar geometry. This is the first study to quantify bone-remodeling around hip implants at an intermediate term (mean of 7.7 years) follow-up. Bone mineral density adjacent to acetabular implants was evaluated using quantitative computed tomography (QCT). The data demonstrated that stress-shielding around standard titanium cementless acetabular components continues well beyond the short-term. The study revealed that patients with Trabecular Metal monoblock cups experienced up to a 41% increase in mean BMD around certain areas of their implants, compared to a loss of up to 45% in BMD in certain areas of the control hips with titanium cups.
It is well established that a decrease in bone density may compromise the long term success of the primary surgery and may increase the difficulty and expense of revision reconstruction. Acetabular stress-shielding can also exacerbate patients’ osteolytic response to bearing surface particles, potentially further reducing the bony support for the implant. The authors of the study suggest that the elasticity (low stiffness) of Trabecular Metal material may induce a transfer of stresses to the periacetabular bone that more closely replicates the normal physiologic load transfer, thereby decreasing the detrimental effects of stress-shielding by allowing the bone to respond to normal loading patterns. In this study, clinically significant bone preservation and in-growth were observed radiographically around Trabecular Metal implants. These results indicate the potential for improved long term biologic fixation with Trabecular Metal implants and could result in fewer and less complex revision procedures.
"Few studies draw firm conclusions about the performance of cementless components in implants used in total hip arthroplasty, and for the most part, data about bone remodeling after surgery has been limited to short-term follow-up," said David Lewallen, MD, orthopaedic surgeon at the Mayo Clinic and one of the study's authors. "Our findings confirmed initial assumptions that the low stiffness properties of this porous metal —similar to cancellous bone—were better able to transfer physiological stresses, theoretically decreasing the detrimental effects of stress-shielding commonly seen around traditional acetabular implants."
Trabecular Metal material is a structural biomaterial whose cellular architecture resembles bone and approximates its physical and structural properties more closely than other prosthetic materials. The unique, highly porous trabecular configuration is conducive to more normal bone formation and bone in-growth, decreased stress-shielding, and the potential for improved long term implant fixation. Trabecular Metal implants are fabricated using elemental tantalum metal and a patented vapor deposition process that creates a metallic strut configuration resembling cancellous bone with a nano-textured surface. Trabecular Metal Technology is exclusive to Zimmer.
"This clinical study is the first to directly compare bone-remodeling effects of a low stiffness porous metal construct to more rigid traditional titanium hip implants at a mid-term follow-up, and highlights potential advantages attributed to Trabecular Metal technology," said Cheryl R. Blanchard, PhD, Zimmer's Senior Vice President and Chief Scientific Officer. "It demonstrates that Zimmer's unique Trabecular Metal products may significantly reduce bone loss after surgery and may improve long term biologic fixation."
About the Company
Founded in 1927 and headquartered in Warsaw, Indiana, Zimmer designs, develops, manufactures and markets orthopaedic reconstructive, spinal and trauma devices, dental implants, and related surgical products. Zimmer has operations in more than 25 countries around the world and sells products in more than 100 countries. Zimmer's 2008 sales were approximately $4.1 billion. The Company is supported by the efforts of more than 8,000 employees worldwide.
For more information about Zimmer, visit www.zimmer.com
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James T. Crines