Li Yang, Fogel Guy R, Liao Zhenhua, Liu Weiqiang
State Key Laboratory of Tribology, Tsinghua University, Beijing, 100084, China.
Department of Mechanical Engineering, Tsinghua University, Beijing, 100084, China.
Int J Comput Assist Radiol Surg. 2017 Aug;12(8):1399-1409. doi: 10.1007/s11548-017-1616-3. Epub 2017 Jun 8.
Few finite element studies have investigated changes in cervical biomechanics with various prosthesis design parameters using hybrid surgery (HS), and none have investigated those combined different HS strategies. The aim of our study was to investigate the effect of ball-and-socket prosthesis geometry on the biomechanical performance of the cervical spine combined with two HS constructs.
Two HS strategies were conducted: (1) ACDF at C4-C5 and anterior cervical disc replacement (ACDR) at C5-C6 (ACDF/ACDR), and (2) ACDR/ACDF. Three different prostheses were used for each HS strategy: prosthesis with the core located at the center of the inferior endplate with a radius of 5 mm (BS-5) or 6 mm (BS-6), or with a 5 mm radius core located 1 mm posterior to the center of the inferior endplate (PBS-5). Flexion and extension motions were simulated under displacement control.
The flexion motions in supra- and infra-adjacent levels increased in all cases. The corresponding extension motions increased with all prostheses in ACDR/ACDF group. The stiffness in flexion and extension increased with all HS models, except for the extension stiffness with ACDF/ACDR. The facet stresses between the index and infra-adjacent level in ACDR/ACDF were significantly greater than those in the intact model . The stresses on the BS-5 UHMWPE core were greater than the yield stress.
The core radii and position did not significantly affect the moments, ROM, and facet stress in extension. However, the moments and ROM in flexion were easily affected by the position. The results implied that the large core radii and posterior core position in ACDR designs may reduce the risk of subsidence and wear in the long term as they showed relative low stress . The ACDF/ACDR surgery at C4-C6 level may be an optimal treatment for avoiding accelerating the degeneration of adjacent segments.
很少有有限元研究使用混合手术（HS）来研究不同假体设计参数对颈椎生物力学的影响，且尚无研究探讨联合不同HS策略的情况。本研究的目的是研究球窝假体几何形状对结合两种HS结构的颈椎生物力学性能的影响。
实施两种HS策略：（1）C4-C5节段进行前路颈椎间盘切除融合术（ACDF），C5-C6节段进行颈椎前路椎间盘置换术（ACDR）（ACDF/ACDR），以及（2）ACDR/ACDF。每种HS策略使用三种不同的假体：核心位于下终板中心、半径为5 mm（BS-5）或6 mm（BS-6）的假体，或核心半径为5 mm且位于下终板中心后方1 mm的假体（PBS-5）。在位移控制下模拟屈伸运动。
所有情况下，上位和下位相邻节段的屈曲运动均增加。ACDR/ACDF组中，所有假体对应的伸展运动均增加。除ACDF/ACDR的伸展刚度外，所有HS模型的屈伸刚度均增加。ACDR/ACDF组中，责任节段与下位相邻节段之间的小关节应力明显大于完整模型。BS-5超高分子量聚乙烯核心上的应力大于屈服应力。
核心半径和位置对伸展时的力矩、活动度和小关节应力无显著影响。然而，屈曲时的力矩和活动度很容易受到位置的影响。结果表明，ACDR设计中较大的核心半径和核心后置位置可能会降低长期下沉和磨损的风险，因为它们显示出相对较低的应力。C4-C6节段的ACDF/ACDR手术可能是避免加速相邻节段退变的最佳治疗方法。
