Spine
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Cross-section analysis. ⋯ 4.
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Spinal cord injury (SCI) has occurred in 2.5 million people worldwide, and 130,000 new cases are reported each year. SCI most commonly consists of a compression injury with hemorrhage into gray matter and loss of neurons, oligodendroglia, and astrocytes, followed by invasion of lymphocytes and macrophages; cavitation of the cord follows, then Wallerian degeneration of ascending and descending tracts and loss of neuronal circuitry, culminating in glial scar perpendicular to the direction of the axon. Onset of necrosis occurs within 24 hours. Spontaneous repair is incomplete and involves limited sprouting of axons and new spinal circuits that bypass the lesion and move into descending tracts, resulting in indirect connections with lumbar motor neurons.
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When spinal cord injury (SCI) occurs, injured cells must survive and regenerate to close gaps caused by the injury and to create functional motor units. After peripheral nerve injury, Wallerian degeneration in the distal nerve stump creates a neurotrophic and growth-supportive environment for injured neurons and axons via Schwann cells and secreted cytokines/neurotrophins. In both SCI and peripheral nerve injury, injured motor and sensory neurons must regenerate axons, eventually reaching and reinnervating target tissue (SDC Figure 1, http://links.lww.com/BRS/B116). This process is often unsuccessful after SCI, and the highly complex anatomy of branching axons and nerves in the peripheral nervous system leads to slow recovery of function, even with careful and appropriate techniques.
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Computational modeling with finite element analysis (FEA) is an integral component of medical device design and development. Researchers assess dimensions and stability of the experimental device; test load sharing, stresses, and strains; and analyze failures and modifications. ⋯ Prerequisites of quality FEA include a solid understanding of morphology and material properties of the model, a firm grasp of the effects of loads on body structures, and the work of a skilled bioengineer who can translate the ideas of surgeons into an appropriate FEM. With today's modern techniques-computed tomography/magnetic resonance imaging, etc.-the bioengineer moves from scan to FEM in just weeks.
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Taking a product from concept to commercialization requires careful navigation of the regulatory pathway through a series of steps: (A) moving the idea through proof of concept and beyond; (B) evaluating new technologies that may provide added value to the idea; (C) designing appropriate test strategies and protocols; and (D) evaluating and mitigating risks. Moving an idea from the napkin stage of development to the final product requires a team effort. When finished, the product rarely resembles the original design, but careful steps throughout the product life cycle ensure that the product meets the vision.