COMPLIANT POLYMER LUMBAR ARTIFICIAL DISC (PILOT STUDY)

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Spine ailments are amongst the most common and costly illnesses of today's societies. In the US alone, 30 billion dollars are spent annually for the surgical treatment of low back pain. About 400,000 such surgeries are performed every year. Until recently the 'gold standard' has been to perform a spine fusion. In 2005 FDA cleared for the first time a mechanical disc replacement device to be freely sold in the US (several more devices are expected in 2006). Mechanical disc replacement devices, however, are feared by experts not to have the hoped (and praised) long term advantages when compared to traditional spinal fusion. Adjacent level degeneration, known to exist as a result of fusion, may still persist as an adverse outcome of disc replacement surgery. In addition, new complications such as poorly guided movements between vertebral bodies causing pain or small wear particles originating from the implant surfaces causing inflammation and ultimately implant loosening may plague the patient. A new artificial disc concept, a so-called "compliant disc", that would potentially not have the above shortcomings, shall be tested in a baboon experiment for its clinical suitability. The CAdisc implant is comprised of three polycarbonate polyurethane formulations of different hardness for annulus, nucleus and end plate. The end plates have a thin coating of calcium phosphate. The range of formulations and the coating have been subjected to cytotoxicity testing and have also been used in implants for a 12 week ovine femur study without ill effect. Moreover, polycarbonate polyurethanes are a well understood class of materials, with considerable history in medical devices. They were one of the first classes of polyurethane materials promoted for their biostability. They are thermoplastic elastomers with carbonate linkages adjacent to hydrocarbon groups which give this class of materials oxidative stability, making these polymers attractive for medical device applications where oxidation is a potential mode ofdegradation. In addition, polycarbonate polyurethanes have been shown to minimize surface degradation such as stress induced microfissures. Three commercial grades of polycarbonate urethanes are in use as part of approved medical applications, including Bionate' (the Polymer Technology Group), CarbothaneB (Noveon) and ChronoFlexB C (CardioTech International). Should the CAdisc implant prove to be a valid option to presently used artificial disc implants featuring sliding metal-on-metal or metal-on-polyethylene surfaces, complications or adverse outcomes associated with these types of implant (induced adjacent level degeneration, sudden and painful giveaway episodes for spinal movements known as "clinical instability," lack of axial cushioning, small wear particles causing inflammation, etc.) could be avoided.