<p>The MOVE-C Cervical Artificial Disc – Design, Materials, Mechanical Safety</p>

Abstract

Purpose: There are various cervical disc prostheses on the market today. They can be subdivided into implants with a ball-and-socket design and implants with a flexible core, which is captured between the implant endplates and sealed using various sheaths. Implants with an articulating surface are mostly metal-on-metal or metal-on-UHMWPE designs and, thus, do not allow for axial damping. The aim of this study is to provide mechanical safety and performance data of the MOVE-C cervical disc prosthesis which combines both an articulating surface and a flexible core. Materials and Methods: MOVE-C consists of a cranial and caudal metal plate made of TiAl6V4. The cranial plate is TiNbN coated on its articulating surface. The caudal plate has a fixed polycarbonate-urethane (PCU) core. The TiNbN coating is meant to optimize the wear behavior of the titanium endplate, whereas the PCU core is meant to allow for a reversible axial deformation, a pre-defined neutral zone and a progressive load-deformation curve in all planes. Results: Various standard testing procedures (for example, ISO 18192-1 and ASTM F2364) and non-standard mechanical tests were carried out to prove the implant's mechanical safety. Due to the new implant design, wear and creep testing was deemed most important. The wear rate for the PCU was in maximum 1.54 mg per million cycles. This value was within the range of the UHMWPE wear rates reported for other cervical disc prostheses (0.53 to 2.59 mg/million cycles). Also in the creep-relaxation test, a qualitatively physiological behavior was shown with a certain amount of remaining deformation but no failure. Conclusion: The mechanical safety of the MOVE-C cervical disc prosthesis was shown to be comparable to other cervical disc prostheses. Since PCU wear particles were elsewhere shown to be less bioactive than cross-linked UHMWPE particles, wear-related failure in vivo may be less frequent compared to other prostheses. This, however, will have to be shown in further studies.

An additively manufactured model for preclinical testing of cervical devices

“…11 While numerous studies have evaluated the kinematics of the cervical spine following CDRs, to our knowledge, no biomechanical studies have evaluated the fixation of CDRs within the vertebra in a composite or cadaveric model. [19][20][21][22][23][24] Fixation testing of total hip and knee replacements using composite model bones have been conducted for more than three decades by investigators world-wide. [25][26][27][28][29][30][31] These biomimetic models utilize reinforced epoxy resin to simulate cortical bone and rigid polyurethane foam to replicate cancellous bone, resulting in a highly reproducible model that can withstand extensive cyclic loading without decay, as well as higher loads than typical cadaver specimens.…”

“…Furthermore, the Food and Drug Administration website for Manufacturer and User Facility Device Experience (MAUDE) indicates that 25% of devices failing at 5‐years are due to mechanical complications such as migration, loosening, and subsidence 11 . While numerous studies have evaluated the kinematics of the cervical spine following CDRs, to our knowledge, no biomechanical studies have evaluated the fixation of CDRs within the vertebra in a composite or cadaveric model 19–24 …”

“… 11 While numerous studies have evaluated the kinematics of the cervical spine following CDRs, to our knowledge, no biomechanical studies have evaluated the fixation of CDRs within the vertebra in a composite or cadaveric model. 19 , 20 , 21 , 22 , 23 , 24 …”

The Impact of Bias and Nitrogen Pressure on TiNbN Coatings in Arc-PVD Processes—A Multifactorial Study

“…TiN coatings have been state of the art for the surface treatment of orthopaedic and dental implants for many decades. However, comparatively new hard PVD coatings, such as TiAlN, ZrN and TiNbN, are advancing in the medical industry [9][10][11][12]. The application of TiNbN coatings instead of TiN coatings is described in the literature, and for the same reasons: the reduction in metallic ion diffusion and abrasive wear of articulating implant surfaces [9,10,13].…”

“…However, despite some clinical data on the outcome of TiNbN-coated implants of Herbster et al [8] and Bergschmidt et al [13], and the biocompatibility [26,27] and wear performance of TiNbN in vitro [10,12] and ex vivo [4,8], there are no published studies on the basic mechanical properties and structure of TiNbN coated by cathodic arc processes.…”