Department of Orthopedics, Orthopedic Research Institute, West China Hospital, Sichuan University, Chengdu, China.
BMC Musculoskelet Disord. 2024 Oct 23;25(1):839. doi: 10.1186/s12891-024-07895-z.
Artificial Cervical Disc Replacement (ACDR) is an effective treatment for cervical degenerative disc diseases. However, clinical information regarding the facet joint alterations after ACDR was limited. Facet tropism is common in the sub-axial cervical spine. Our previous research indicated that facet tropism could lead to increased pressure on the cervical facet joints. This study aimed to assess the impact of facet tropism on the facet contact force and facet capsule stress after ACDR.
A C2-T1 cervical finite element model was constructed from computed tomography (CT) scans of a 28-year-old male volunteer. Symmetrical, moderate asymmetrical (7 degrees tropism), and severe asymmetrical (14 degrees tropism) models were created at the C5/C6 level by altering the facet orientation at the C5-C6 level. The C5/C6 ACDR was simulated in the intact, moderate asymmetrical and severe asymmetrical models. A 75-N follower load with 1.0-Nm moments was applied to the top of C2 vertebra in the models to simulate flexion, extension, lateral bending, and axial rotation with the T1 vertebra fixed. The range of motions (ROMs) under all moments, facet contact forces (FCFs) and facet capsule strains were tested.
In the asymmetrical model, the right FCFs considerably increased under flexion, extension, right bending, left rotation, especially under right bending the right sided FCF of the severe asymmetrical model was about 5.44 times of the neutral position, and 3.14 times of the symmetrical model. and concentrated on the cephalad part of the facets. The facet capsule stresses on both sides remarkably increased under extension, lateral bending and right rotation. In the moderate and severe asymmetrical models, the capsule strain was greater on both sides of each position than in the symmetric model.
The face tropism increased facet contact force and facet capsule strain after ACDR, especially under extension, lateral bending, and rotation, and also could result in abnormal stress distribution on the facet joint surface and facet joint capsule. The results suggest that face tropism might be a risk factor for post-operative facet joint degeneration progression after ACDR. Facet tropism may be noteworthy when ACDR is considered as a surgical option.
人工颈椎间盘置换术（ACDR）是治疗颈椎退行性疾病的有效方法。然而，关于 ACDR 后关节突关节改变的临床信息有限。关节突倾斜在颈椎下段很常见。我们之前的研究表明，关节突倾斜可导致颈椎关节突关节压力增加。本研究旨在评估关节突倾斜对 ACDR 后关节突接触力和关节突囊应力的影响。
从一名 28 岁男性志愿者的计算机断层扫描（CT）图像构建 C2-T1 颈椎有限元模型。通过改变 C5-C6 水平的关节突方向，在 C5/C6 水平创建对称、中度不对称（7 度倾斜）和重度不对称（14 度倾斜）模型。在完整、中度不对称和重度不对称模型中模拟 C5/C6 ACDR。在 C2 椎体顶部施加 75-N 跟随力和 1.0-Nm 力矩，以模拟 T1 椎体固定时的屈伸、侧屈和轴向旋转。在所有力矩下测试运动范围（ROM）、关节突接触力（FCF）和关节突囊应变。
在不对称模型中，屈伸、伸展、右侧弯曲、左侧旋转时，右侧 FCF 明显增加，尤其是在右侧弯曲时，重度不对称模型右侧 FCF 约为中立位的 5.44 倍，是对称模型的 3.14 倍。并集中在关节突的头侧部分。伸展、侧屈和右侧旋转时，双侧关节突囊应力明显增加。在中度和重度不对称模型中，每个位置两侧的囊应变均大于对称模型。
ACDR 后关节突倾斜增加了关节突接触力和关节突囊应变，尤其是在伸展、侧屈和旋转时，也可能导致关节突表面和关节突关节囊的异常应力分布。结果表明，关节突倾斜可能是 ACDR 后关节突关节退变进展的危险因素。在考虑 ACDR 作为手术选择时，关节突倾斜可能值得关注。
