Biomechanics of Total Disc Replacement for the Cervical Spine

描述(由申请人提供)： 摘要目的：日常生活活动要求亚轴位颈椎(C2-C7)在屈伸、侧弯和轴向旋转时有足够的活动度。这些节段还表现出横向弯曲和轴向旋转之间的特征运动耦合。颈椎全椎间盘置换术(TDR)已在临床上用于治疗神经根病和脊髓病。TDR复制生理运动的能力对于保护相邻的水平免受退化至关重要。假说：(H1)颈椎TDR在重建节段恢复生理性的初级和耦合运动以及负荷分配的能力取决于假体的设计特点。(2)颈椎TDR在重建节段恢复生理运动量和质量及负荷分布的能力取决于外科技术，例如：(1)用于种植的环形窗的宽度，(2)PLL是保留还是切除，以及(3)假体在椎间隙中的位置。(H3)相邻节段的第二个TDR不会对指数节段TDR的生物力学产生不利影响。具体目标：(1)测量在ADL过程中所经历的载荷下颈椎椎间的三维(3-D)运动轮廓和关节盘和小关节之间的载荷分配：(A)完好无损；(B)由于假体设计和手术技术的变化，C5-C6 TDR后；以及(C)C6-C7第二次TDR后。(2)开发一种新的技术来生成特定于标本的、基于CT的三维计算机模型，以评估完整节段和TDR术后小关节和钩椎关节处的运动、间隙和接触，作为假体设计和外科植入技术的可变性的函数。研究计划：该项目将使用实验研究和基于CT的特定标本建模相结合的方法。实验研究：实验将使用60名60岁的成年男性和女性供者的新鲜人类颈椎标本进行。标本将被分成六组假体(每组10个)，分为四个设计类别：(I)单关节轴承设计；(Ii)鞍形轴承设计；(Iii)双轴承活动芯设计；以及(Iv)六自由度可压缩设计。手术技术变量将包括：(I)关节盘间隙内的植入位置(前与后)；(Ii)软组织包膜在植入水平的完整性，包括(A)用于假体植入的前环窗口的宽度(窄与宽)，以及(B)后纵韧带的保留或切除(完整与切除)。基于CT的特定标本模型：将通过CT扫描创建单个标本(总共60个)的3-D计算机模型。在实验期间，将探测植入每个椎骨的四个铝制标记物，这些标记物在CT上可见，并包含在计算机模型中，以建立标本与其模型之间的“数字链接”。实验脊椎运动数据将被用来‘驱动’计算机模型，在整个标本的运动范围内产生经过验证的测量结果。这些模型将被用来评估小关节和钩突关节的间隙距离、相对局部运动和接触面积。统计分析：实验数据和模型结果将使用单因素重复测量方差分析(假体设计)和后多重比较进行分析。我们估计每个假体10个样本可以给出80%的统计学力量来检测结果测量中至少25%的差异。意义：我们建议生成关于不同设计的颈椎假体恢复生理颈椎力学能力的客观数据。此外，我们将开发一种创新的技术，使用基于标本的CT三维计算机模型来评估完整节段和植入椎间盘假体后的小关节和钩椎关节运动。这些发现可以立即转化为临床实践，以改善颈椎疼痛退行性疾病的手术治疗结果。

DESCRIPTION (provided by applicant): Abstract Purpose: Activities of daily living require the sub-axial cervical spine (C2-C7) to have substantial mobility in flexion-extension, lateral bending and axial rotation. These segments also demonstrate a characteristic motion coupling between lateral bending and axial rotation. Cervical total disc replacement (TDR) has been clinically used to treat radiculopathy and myelopathy. The ability of the TDR to replicate physiologic motion is critical to protect adjacent levels from degeneration. Hypotheses: (H1) The ability of cervical TDR to restore physiologic primary and coupled motions and load distribution at the reconstructed segment would depend on the prosthesis design features. (H2) The ability of cervical TDR to restore physiologic quantity and quality of motions and load distribution at the reconstructed segment would depend on surgical techniques such as: (1) the width of the annular window made for implant insertion, (2) whether the PLL is preserved or resected, and (3) prosthesis position in the disc space. (H3) A second TDR at an adjacent level will not adversely affect the biomechanics of the index level TDR. Specific objectives: (1) Measure three-dimensional (3-D) intervertebral motion profiles and load sharing among the disc and facet joints in cervical spines under loads experienced during ADL for the following: (a) intact; (b) after C5-C6 TDR as a function of prosthesis design and surgical technique variability; and (c) after a second TDR at C6-C7. (2) Develop a new technique to generate specimen-specific, CT-based 3-D computer models to assess motions, gapping, and contact at the facet joints and uncovertebral joints in the intact segment and after TDR as a function of prosthesis design and variability in surgical implantation technique. Research Plan: This project will use a combination of experimental studies and CT-based specimen-specific modeling. Experimental Studies: The experiments will be performed using 60 fresh human cervical spine specimens of adult male and female donors <60 years of age. The specimens will be assigned to six prostheses groups (n=10 each) that fall into four design categories: (I) single spherical bearing design; (II) saddle-shaped bearing design; (III) mobile core design with two bearings; and (IV) six degrees-of-freedom compressible design. The surgical technique variables will include: (I) Implant position within the disc space (anterior vs. posterior); and (II) Integrity of the soft-tissue envelope at the implanted level including (a) the width of the window (narrow vs. wide) made in the anterior annulus for prosthesis insertion, and (b) the preservation or resection of posterior longitudinal ligament (intact vs. resected). CT-Based, Specimen-Specific Models: 3-D computer models of individual specimens (60 total) will be created from CT scans. Four aluminum markers implanted in each vertebra, visible on CT and included in the computer model, will be probed during the experiments to establish a 'digital link' between the specimen and its model. Experimental vertebral motion data will be used to 'drive' the computer model, producing validated measurements throughout the specimen's range of motion. The models will be used to assess facet joint and uncinate process articulations in terms of gap distances, relative localized motions, and contact areas. Statistical Analysis: Experimental data and model results will be analyzed using repeated-measures ANOVA with one factor (prosthesis design), and post hoc multiple comparisons. We estimate 10 specimens per prosthesis to give 80% statistical power in detecting a difference of at least 25% in the outcome measures. Significance: We propose to generate objective data on the abilities of cervical disc prostheses of different designs to restore physiologic cervical spine mechanics. In addition, we will develop an innovative technique to assess facet and uncovertebral joint motion in the intact segment and after implantation of disc prostheses using specimen-specific CT-based 3-D computer models. These findings can be immediately translated to clinical practice to improve the surgical treatment outcomes for painful degenerative disease of the cervical spine.