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Recently, many different types of artificial discs have been introduced to persevere the biomechanical behavior of the cervical spine. This study compares the biomechanical behavior of single- and double-level cervical disc arthroplasty, that is “Prestige LP and Mobi-C” on the index and adjacent segment. A three-dimension finite element model of C2-C7 was developed and validated. In single-level prostheses, the Prestige LP or Mobi-C was implanted in the segment C5-C6, while the double-level arthroplasty was integrated at both segments C4-C5 and C5-C6 in the FE model. The intact FE and prosthesis-modified models were constrained from the inferior endplate of the vertebra C7 and applied a compressive load of 73.6 N with a moment load of 1 Nm on the odontoid process of the vertebra C2 to produce flexion/extension, lateral bending, and axial rotation. The prosthesis-modified model’s range of motion and intradiscal pressure were determined and compared to the intact model. Also examined the impact of the prostheses on the stress at the bone-implant interface. The range of motion of the implanted segments in both single- and double-levels arthroplasty was increased while that of the adjacent segment of implanted segments decreased. The intradiscal pressure in both levels of arthroplasty was greater than in the intact model. In conclusion, Mobi-C’s cervical prostheses could better preserve the normal range of motion and maintain intradiscal pressure than the Prestige LP.

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With the high quality natural forest resources dwindling , since some species of wood with natural colors, such as pumping wood , ebony, rosewood , etc., not only material of high value , but also very expensive wood color . However, these are expensive and precious wood in short supply and will therefore valuable timber and wood stain to meet the market demand is similar . Low-quality hardwood stained only bright color, texture clear , three-dimensional sense of strong, but without losing the characteristics of natural wood , and organize production according to market demand the formation of industrialized products in order to improve the utilization of low-quality wood , decorative building materials to increase the existing varieties purposes. Therefore, the use of poplar simulate the market needed precious wood has important practical significance . In addition, light color white poplar wood , in the natural growth process still exists heartwood and sapwood and sooner or later material defects such as chromatic aberration , especially wood treatment is not promptly will result in discoloration, the direct use of the logs are often unable to meet the requirements of decoration . Therefore . The thicker sheet dyed precious poplar wood color , and then prepared to meet the customer poplar wood timber strength and decorative requirements, improve the added value of the use of wood , particularly after dyeing material available performance has been greatly improved.

BACKGROUND: The finite element method (FEM) is an efficient and powerful tool for studying human spine biomechanics. OBJECTIVE: In this study, a detailed asymmetric three-dimensional (3D) finite element (FE) model of the upper cervical spine was developed from the computed tomography (CT) scan data to analyze the effect of ligaments and facet joints on the stability of the upper cervical spine. METHODS: A 3D FE model was validated against data obtained from previously published works, which were performed in vitro and FE analysis of vertebrae under three types of loads, i.e. flexion/extension, axial rotation, and lateral bending. RESULTS: The results show that the range of motion of segment C1–C2 is more flexible than that of segment C2–C3. Moreover, the results from the FE model were used to compute stresses on the ligaments and facet joints of the upper cervical spine during physiological moments. CONCLUSION: The anterior longitudinal ligaments (ALL) and interspinous ligaments (ISL) are found to be the most active ligaments, and the maximum stress distribution is appear on the vertebra C3 superior facet surface under both extension and flexion moments.