August 15, 2007
NEW SPINE FINITE ELEMENT STUDY SHOWS IMPORTANT DIFFERENCES BETWEEN MOBILE-CORE AND FIXED-CORE ARTIFICIAL DISCS
Raynyam, MA (August 15, 2007) -- A new 3-D finite element study published in the August 1 edition of Spine shows that the mobile-core design of the CHARITÉ® Artificial Disc, which consists of two metallic endplates and a polyethylene sliding core, reduces facet loading by more than 50% when placed at or near the center of the disc space, while a fixed-core artificial disc increases facet loading when compared with an intact disc in axial rotation even when placed in an ideal position.
The study, “Comparison of Biomechanical Function at Ideal and Varied Surgical Placement for Two Lumbar Artificial Disc Implant Designs,” used a 3-D finite element model of an intact ligamentous L4-L5 motion segment to analyze facet loading of a mobile-core artificial disc (CHARITÉ Artificial Disc) and a fixed-core artificial disc (ProDisc™-L) in the L4-L5 motion segment.
Co-authors Missoum Moumene, PhD, of DePuy Spine, manufacturer of the CHARITÉ Artificial Disc, and Fred H. Geisler, MD, PhD, of the Illinois Neuro-Spine Center in Aurora, also found that placement of a fixed-core disc anteriorly from a central location increases the contact stress of the core by 40%, while the stresses on the mobile-core remain unchanged.
“This finite element study suggests that there is a difference between mobile- and fixed-cores when it comes to facet loads,” said Dr. Geisler. “Additionally our study predicted much less stress on a mobile core, which may increase its longevity, compared to a fixed core.”
When the mobile-core disc was placed centrally, anteriorly, posteriorly, or laterally, it reduced facet load by 60%, 50%, 85% and 60%, respectively, in axial rotation. The fixed-core disc increased facet load when placed centrally, anteriorly, and laterally by 4%, 12% and 10%, respectively, and lessened the facet load in axial rotation only when placed posteriorly.
“This finite element study suggests that the mobile-core disc design appears to be less sensitive to placement because of its ability to shift side-to-side posteriorly and anteriorly as loads are applied, effectively providing a better load-sharing environment between the major restraints, the facets, and the artificial disc itself,” said Dr. Moumene.
The CHARITÉ Artificial Disc, the first artificial disc approved by the U.S. Food and Drug Administration (FDA) in 2004, has been implanted in several thousand patients in the U.S. and more than 15,000 throughout the world.
Artificial disc replacement is an alternative to spinal fusion surgery, the most common surgical treatment for lower back pain, performed on more than 200,000 people each year. The goals of artificial disc replacement include maintaining segmental spinal motion, reducing pain, increasing patient activity, restoring disc height and lordosis, and eliminating post-operative fusion problems, such as donor site pain and pseudoarthrosis.
The CHARITÉ Artificial Disc is indicated for spinal arthroplasty in skeletally mature patients with degenerative disc disease at one level from L4 to S1. Degenerative disc disease is defined as discogenic back pain with degeneration of the disc confirmed by patient history and radiographic studies. These patients should have no more than 3mm of spondylolisthesis at the involved level. Patients receiving the CHARITÉ Artificial Disc should have failed at least six months of conservative treatment prior to implantation.
As with any surgical procedure, disc replacement surgery has risks. Individual patient results may vary and are not indicative of all outcomes. Patients should consult a trained spine surgeon to determine whether this procedure is right for them.
About DePuy Spine
DePuy Spine, a Johnson & Johnson company, has worked and partnered with leading clinicians, researchers, and thought leaders to develop products to treat spine disorders for over 20 years. The company is committed to advancing the knowledge of all health care professionals and their patients in addressing spinal pathologies.
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Corporate/industry funds were received in support of the study. Although one or more of the author(s) has/have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of the manuscript published in Spine, benefits will be directed solely to a research fund, foundation, educational institution, or other nonprofit organization with which the author(s) has/have been associated.
Source: DePuy Spine, Inc.