Zimmer Holdings, Inc. presented prospective clinical advantages of its Trabecular Metal Technology in a comparative study. The company's Trabecular metal material was found to improve long term biologic implant fixation and simplify revision procedures. The study was conducted by researchers at the Joint Replacement Surgeons of the Indiana Research Foundation and Mayo Clinic. The study described the low stiffness and osteoconductive properties of Trabecular Metal Technology. The study found significant reductions in acetabular bone loss adjacent to the Trabecular Metal device when compared to the titanium component, and a relative increase in bone mineral density (BMD) after total hip arthroplasty (THA) using implants made with Zimmer's Trabecular Metal Technology.
In this comparative study, researchers studied 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. The study evaluated bone mineral density adjacent to acetabular implants 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.
The authors suggested that the elasticity which is nothing but the low stiffness of Trabecular Metal material may induce a transfer of stresses to the periacetabular bone which more closely replicates the normal physiologic load transfer, hence decreasing the detrimental effects of stress-shielding by allowing the bone to respond to normal loading patterns. Clinically significant bone preservation and in-growth were observed radiographically around Trabecular Metal implants in this study. The study 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. Its cellular architecture resembles bone and approximates its physical and structural properties. The highly porous trabecular configuration is conducive to more normal bone formation and bone in-growth, the potential for improved long term implant fixation and decreased stress-shielding. Trabecular Metal implants are fabricated with elemental tantalum metal and a patented vapor deposition process which creates a metallic strut configuration resembling cancellous bone with a nano-textured surface.
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.