Professor Dept of Neurosurgery, PGIMER, Chandigarh Chandigarh, India
Introduction: The atlantoaxial complex contributes to more than 50 % of the neck rotation. However, to provide this kind of mobility, the C1-2 joints are also the least stable as compared to other vertebrae. The current management options emphasize on fusing the C1-2. Such fusion considerably hampers the neck movements and adversely affects the quality of life. C1-C2 arthroplasty could preserve the motion while stabilizing them. The author has developed artificial joints that functionally mimics the naturally occurring lateral atlantoaxial joints. The arthroplasty was tested for range of motion(ROM) in the past. Based on this data, in-vitro wear and tear testing was performed.
Methods: The previous cadaveric ROM testing for C1-C2 arthroplasty through a posterior approach 50% of axial rotation. However, these prototypes were metal on metal and the material was changed to metal on ultra high molecular ethylene part for wear and tear testing. In-vitro simulated wear testing was conducted using an in-house developed C1-C2 wear simulator (torsion robot). The system operates at 1 Hz frequency with one degree of freedom (DoF) rotation of +/- 20° and an axial load of 125 Newton required to simulate anatomical conditions of the Atlantoaxial joint. The wear test was performed on four samples for five million cycles each.
Results: The results showed minimal weight loss and no implant failure. Wear debris was analysed for size and morphology, while bearing profiles were evaluated using a coordinate measuring machine (CMM) to assess wear-induced changes and were found to be minimal
Conclusion : The C1-C2 arthroplasty appears to be stable and provides about half of the range of atlantoaxial rotation and appears to have minimal wear and tear. It has the potential for joint motion preservation in the treatment of atlantoaxial instability resulting from lateral C1-C2 joint pathologies and needs further clinical testing
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