European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society
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When the intervertebral disc is removed to relieve chronic pain, subsequent segment stabilization should restore the functional mechanics of the native disc. Because of partially constrained motions and the lack of intrinsic rotational stiffness ball-on-socket implants present many disadvantages. Composite disc substitutes mimicking healthy disc structures should be able to assume the role expected for a disc substitute with fewer restrictions than ball-on-socket implants. ⋯ All device versions altered the coupled intersegmental shear deformations affecting facet joint contact through contact area displacements. Loads in the bony endplates adjacent to the implants increased as the implant stiffness decreased but did not appear to be a strong limitation for the implant biomechanical and mechanobiological functionality. In conclusion, numerical results given by biomimetic composite disc substitutes were encouraging with greater potential than that offered by ball-on-socket implants.
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Comparative Study
An in vitro biomechanical comparison of Cadisc™-L with natural lumbar discs in axial compression and sagittal flexion.
The elastomeric, monobloc disc prosthesis (Cadisc™-L, Ranier Technology, Cambridge, UK) aims to preserve biomechanics of an implanted spinal motion segment. ⋯ Implantation of Cadisc™-L caused a reduction in axial stiffness, but maintained disc height and flexion stiffness. IAR loci remained mobile without large displacement of the centroid from the intact spine position.
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The hypothesis for this study was that the simulated wear behavior of a hydroxyapatite coated, self-mating PEEK cervical disc arthroplasty device would be dependent on the simulated testing environment. ⋯ This study showed that at a time when data from retrieval analyses is deficient, it is important to test the wear resistance of cervical disc arthroplasty devices under various conditions. Long-term clinical results and ongoing implant retrievals are required for validation between clinical performance and simulator inputs.
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The aim of this study was to investigate whether or not post-op curve behaviour differs due to different choices of lowest instrumented vertebra (LIV) with reference to lumbar apical vertebra (LAV) in Lenke 3C and 6C scoliosis. ⋯ In conclusion, in Lenke 3C and 6C scoliosis, post-op lumbar curve behaviour differs due to different choices of LIV with reference to LAV, that is, the deviation of lumbar curve improves when the LIV is either at or below the LAV but deteriorates when the LIV is above the LAV. Although the greatest correction occurs when the LIV is below the LAV, choosing LAV as LIV can still be the optimal option in certain cases, since it can yield similar correction while preserving more lumbar mobility and growth potential.
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Case Reports
Chronic pure radiculopathy in patient with organizing epidural hematoma around C8 nerve root.
Spontaneously occurring spinal epidural hematomas are uncommon clinical findings, and the chronic form is the rarest and its most frequent location is the lumbar spine. Pure radicular involvement is far less frequent than myelopathy. We report a case of progressive radiculopathy in a 52-year-old man with spontaneously occurring cervical epidural hematoma (SCEH). ⋯ MRI scan showed small space-occupying lesion around left 8th cervical nerve root. After surgery we confirmed chronic organizing epidural hematoma. To the best of our knowledge, this is the second reported case in the worldwide literature of pure radiculopathy in a patient with chronic SCEH.