Objective: To investigate the impact of implant height on the morphology of cervical facet joints in artificial cervical disc replacement (ACDR). Methods: A finite element model of the cervical spine from C(2) to C(7) was constructed. The surgical processes of ACDR were simulated by insertion of 5 mm, 6 mm or 7 mm Prestige-LP artificial cervical discs. The morphological changes of cervical facet joints were recorded in terms of facet overlap distance, facet overlap area and facet angle. Results: The normal height Prestige-LP cervical disc could restore the natural status of the cervical spine. Compared with the intact condition, the model with ≥2 mm height implant would reduce the overall range of motion (ROM) by 19.2% in flexion, 19.4% in extension, 18.4% in lateral bending and 19.0% in axial rotation. Besides, the ROM at the surgical level reduced by 15.8% in flexion, 15.4% in extension and lateral bending and 19.0% in rotation. The upper and lower adjacent levels (C(4/5) and C(5/6)) showed more obvious changes in ROM, which reduced by 26.8% and 26.5% in flexion, 26.6% in extension, 26.5% and 26.4% in lateral bending, and 26.4% and 26.3% in rotation, respectively. The reduction of facet overlap distance, facet angle and facet overlap area with the ≥2 mm height artifact was 9.6%, 30.7%, and 17.9% respectively at the upper adjacent level, and 22.3%, 35.3% and 28.2% respectively at the surgical level, compared with the intact model.The morphology of facet joints at the lower adjacent level were slightly changed. Conclusion: The implant height selection in ACDR should be in accordance with the physiological intervertebral disc height. Artifact with ≥2 mm in height would obviously change the morphology of facet joints, thus should not be used in clinical practice.
目的： 探究不同高度的人工颈椎间盘假体对小关节形态学的影响。 方法： 建立C(2-7)有限元模型，模拟5、6、7 mm的Prestige-LP间盘置入，观测术后小关节重合距离、小关节夹角、小关节重合面积等形态学指标的变化。 结果： 合适高度的Prestige-LP假体能较好地模拟颈椎生理特性。与完整情况相比，高2 mm假体置入后颈椎整体活动度在前屈时减少19.2%，后伸时减少19.4%，侧偏时减少18.4%，旋转时减少19.0%；手术节段活动度在前屈时减少15.8%，后伸时减少15.4%，侧偏时减少15.4%，旋转时减少15.3%。相比C(5/6)节段，C(4/5)及C(6/7)节段活动度受假体高度影响更大，前屈时分别下降26.8%、26.5%，后伸时均下降26.6%，侧偏时分别下降26.5%、26.4%，旋转时分别下降26.4%、26.3%；上位邻近节段小关节重合距离降低9.6%，小关节夹角增大30.7%，小关节重合面积降低17.9%；手术节段小关节重合距离减少22.3%，小关节夹角增大35.3%，重合面积减少28.2%；下位邻近节段小关节形态学受假体高度影响较小。 结论： 人工颈椎间盘置换术术中选择假体高度应尽可能地与术前生理状况下高度一致，高2 mm假体将显著改变小关节形态，临床中应避免使用。.
Keywords: Artificial cervical disc; Cervical spine; Facet joint; Finite element analysis.