In silico evaluation of a new composite disc substitute with a L3-L5 lumbar spine finite element model

摘要

When the intervertebral disc is removed to\udrelieve chronic pain, subsequent segment stabilization\udshould restore the functional mechanics of the native disc.\udBecause of partially constrained motions and the lack of\udintrinsic rotational stiffness ball-on-socket implants present\udmany disadvantages. Composite disc substitutes mimicking\udhealthy disc structures should be able to assume the role\udexpected for a disc substitute with fewer restrictions than\udball-on-socket implants. A biomimetic composite disc\udprototype including artificial nucleus fibre-reinforced\udannulus and endplates was modelled as an L4–L5 disc\udsubstitute within a L3–L5 lumbar spine finite element\udmodel. Different device updates, i.e. changes of material\udproperties fibre distributions and volume fractions and\udnucleus placements were proposed. Load- and displace-\udment-controlled rotations were simulated with and without\udbody weight applied. The original prototype reduced\udgreatly the flexibility of the treated segment with signifi-\udcant adjacent level effects under displacement-controlled\udor hybrid rotations. Device updates allowed restoring large\udpart of the global axial and sagittal rotational flexibility\udpredicted with the intact model. Material properties played\uda major role, but some other updates were identified to\udpotentially tune the device behaviour against specific\udmotions. All device versions altered the coupled interseg-\udmental shear deformations affecting facet joint contact\udthrough contact area displacements. Loads in the bony\udendplates adjacent to the implants increased as the implant\udstiffness decreased but did not appear to be a strong limi-\udtation for the implant biomechanical and mechanobiolog-\udical functionality. In conclusion, numerical results given by\udbiomimetic composite disc substitutes were encouraging\udwith greater potential than that offered by ball-on-socket\udimplants