Intervertebral Disk Replacement - Keivan Anbarani's Electronic ...

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The Prodisc-‐C prosthesis uses a cobalt-‐chromium-‐molybdenum alloy combination for end plates and UHMWPE as the central material. The endplates are coated with titanium plasmapore for tissue compatibility and bone ingrowth with the locking core of UHMWPE to provide the ball-‐and-‐socket articulation. The porous coated motion, or PCM device, approved for clinical trains in the U.S. in 2004 uses a large-‐radius UHMWPE core with cobalt-‐chrome endplates to promote bone ingrowth (Figure 13a). The endplates have serrated surfaces with a titanium-‐calcium phosphate bony ingrowth coating to enhance postoperative stability with an additional two layers of pure titanium plasma sprayed onto the back of the endplates, followed by an electrochemically applied calcium phosphate hydroxyapatite layer. Two modified types of this design exist: a low-‐profile PCM disc for patients in whom the posterior longitudinal ligament (PLL) is preserved, and a fixed PCM disc with screws when the PLL is removed. A rectangular shaped design is used to maximize support in the lateral areas. The Bryan Disc (Figure 13b) is another metal-‐on-‐ polymer disc that consists of a low friction elastic polymer nucleus and two anatomically shaped titanium alloy shells equipped with anterior rigid wings to prevent posterior migration. A flexible membrane encompasses the disc that contains saline to diminish any friction and wear. A porous titanium coating is also used on bone-‐contacting surfaces of the shells that contribute to long-‐term stability. Other discs include the Mobi-‐C Disc (Figure 13c) and the Secure-‐C Disc in which has entered a clinical phase study expecting to involve almost 400 participants, including 100 nonrandomized training cases (A.T. Villavicencio, MD, et al, 2007). Ceramic-on-Polymer Figure 13. a) PCM and b) Bryan and c) Mobi-C Disc Source: Spine-Health, 2010 In TDR, bioactive ceramics are used on surfaces to coat UHMWPE polymers to enhance viscoelasticity. An example is the 3-‐DF, a three-‐dimensional fabric woven by polymer 12
fibers coated with ceramics, such as the Kanada one-‐rod SR system. This type of disc implant has undergone years of experimental observation work in which excellent bone ingrowth was observed and thus, a potential hope for clinical breakthrough with further necessary refinements in terms of design and surgical strategy (Y.Kotani, et al). Ceramic-on-Ceramic Ceramics have become a recent alternative for use in artificial disc design. These materials can provide excellent wear resistance, but require proper manufacturing techniques that may otherwise result in fractures if defective (A.T. Villavicencio, MD, et al, 2007). The Cerpass, is an original ceramic-‐on-‐ceramic disc, currently waiting for FDA approval for investigation. Its potential for TDR is the material and design’s ability to provide better durability and eliminate potential problems of wear debris. Another ceramic-‐on-‐ceramic prosthesis is the Catalina, not currently available in the United States, and the Cervidisc. Table 5 below summarizes the above mentioned designs and many others that incorporate many other material composites currently undergoing research or pending clinical phase trials. Table 5. Artificial Discs Statistics Exhibit Company Product Description Regulatory Status Abott Spine ISD Elastomer core in woven cover; replaces anterior Aesculap Active L longitudinal ligament CoCr on poly, semi mobile bearing IDE began 2007 Amedica Altia Silicon nitride ceramic IDE began 2009 AxioMed Freedom Elastomer/Ti endplates IDE began 2008 Biomet Min T Ceramic on endplate, Ti keel fixed to vertebra Trials in Australia Cervitech PCM-‐V, PCM-‐TI, PCM-‐EF CoCr or Ti on poly, broad U.S. pivotal clinical trial radius enrolment complete DePuy Charite CoCr socket on poly, ball and FDA cleared DePuy Discover Ti on poly IDE began 2006 Disc Motion TrueDisc-‐C, TrueDisc-‐L Ball and socket Globus i) Secure-‐C; ii) Alliance i) Metal on poly/semi LDR Spine i) Mobi-‐C; ii) Mobidisc mobile bearing; ii) CoCr on poly Ti-‐HA coated CoCr on poly, mobile core Medtronic i) Prestige ST; ii) Prestige i) Stainless steel metal-‐on-‐ FDA cleared 13 i) IDE enrolment complete; ii) in development i) FDA cleared; ii) IDE enrolment complete
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Page 24 and 25: References 1. Bartels, R. H.M.A., R

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