Evaluation of regional characteristics and structural, functional stability of C2-C7 articular process based on Micro-CT observation

doi:10.12307/2021.327

Abstract

Abstract: BACKGROUND: Cervical spine joints are important structures involved in cervical spine movements, and are also one of the important causes of cervical spondylosis and cervical-derived disease. Quantifying the spatial distribution of the trabecular structure of the cervical articular bone is very important for the early diagnosis of skeletal diseases and potential fracture risks.
OBJECTIVE: To explore the difference of biomechanics between bone cement augmented and common proximal femoral nail antirotation in the treatment of type AO31-A3.3 intertrochanteric fracture.
METHODS: A total of 144 specimens of cervical articular process. Each joint was divided into four regions of interest: superior anterior, superior posterior, inferior anterior, and posterior inferior. A sample with a volume of 5 mm×5 mm×5 mm was scanned by Micro-CT. The microstructure of each sample was calculated, and the characteristics of the microstructure changes in the articular process regions were summarized to reveal the structure and strength predominant areas and weak areas of the articular processes, and the safety and stability of the cervical spine were evaluated.
RESULTS AND CONCLUSION: (1) There were significant differences in bone volume fraction (BV/TV), bone surface/bone volume (BS/BV), and trabecular separation (Tb.Sp) between different areas of the articular process. Partial Eta was 5.5%, 4.8% and 4.3%, respectively (Eta% is the percentage of variables influencing each other; the larger the value, the greater the influence). Among them, the BV/TV value had the largest difference between articular processes. (2) Significant differences were detected in C2-C7 vertebral sequence in BV/TV, trabecular number (Tb.N), BS/BV, trabecular thickness (Tb.Th), Tb.Sp, and trabecular bone pattern factor (Tb.Pf) values. Among them, the Eta of Tb.N was the largest, which indicated that the difference of Tb.N between different vertebral sequences was the largest. (3) There was a significant difference in Tb.Th between the left and right sides. The partial Eta was 2.0%. The left side of C2-C7 had a larger BV/TV value than the right articular process. The largest area was the superior anterior area, and the smallest area was concentrated in C7. (4) The maximum value of TB.N was mainly concentrated in the superior anterior and superior posterior areas, and the minimum value was concentrated in the posterior inferior area. C2-C5 declined; C5-C6 rose; and then C6-C7 dropped significantly. (5) The overall change trend of BS/BV was opposite to BV/TV. The maximum value was mainly concentrated in the superior posterior area, and the minimum value was mainly concentrated in the superior anterior area. (6) The left side C2 of Tb.Th was larger than the right side. The change of superior posterior > superior anterior > inferior anterior > posterior inferior was similar to that of BV/TV. The largest area was concentrated in the superior anterior area and the value of the C5 articular process peaked; and the changes on the left and right sides were similar. (7) The maximum and minimum values of Tb.Sp were mainly concentrated in the superior posterior and superior anterior regions (indicating that the bone structure was suitable for function and had obvious anisotropy). (8) The maximum and minimum values of Tb.Pf were mostly concentrated at the C7 and C5 levels. (9) The microstructure and mechanical properties of C2-C7 cervical vertebrae had different contributions to cervical vertebra motion. The larger the microstructure parameters BV/TV, Tb.N, and Tb.Th, which were positively related to bone mass, which meant the better the bone mass in this area, the better the stress load capacity; and it was less likely to be damaged because it belonged to the structural performance advantage area. Otherwise, the microstructure parameters BS/BV, Tb.Sp, and Tb.Pf, which were inversely related to bone mass, had larger values and the worse the load stress capacity, the higher the risk of damage in this area.

Key words: C2-C7, articular process, trabecular bone, Micro-CT, microstructure, cervical spine

CLC Number:

Hu Zhe, Zhao Haiyan, Zhang Shaojie, Cai Yongqiang, Wang Xing, Qu Xingyue, Ma Yuan, Li Zhijun. Evaluation of regional characteristics and structural, functional stability of C2-C7 articular process based on Micro-CT observation[J]. Chinese Journal of Tissue Engineering Research, 2021, 25(33): 5356-5361.

Figures/Tables 2

2.2 颈椎关节突微观结构指标的变化趋势从C2-C7左右4个区域中6个微观结构指标的变化趋势和规律性分析，C2的骨小梁体积分数较小，C3-C6渐增，C7的骨小梁体积分数最小，见图2A，表明其骨质相对疏松，特别是上后区域骨折的风险最高。整体而言，C2-C7 骨小梁体积分数值左侧大于右侧(表2)，左、右侧的最大区域均为上前区。C2-C4左侧下后区域最小、而右侧上后区域最小，可看出从C2-C7关节突后区的骨小梁体积分数较小(颈椎活动主要处于正常的生理曲度或突出状态，而在关节前部的积聚负荷大于后部区域)。骨小梁数目最大值主要集中在C4的上后区域，最小值集中在C7的下后区域，其变化趋势C2-C4基本相等，C5-C6呈上升趋势，而C6-C7明显下降，见图2B。骨小梁表面积体积比的上前、上后、下前区域也存在类似趋势，即C2-C3下降而C3-C4上升，C4-C7再下降；但下后区的C3-C5下降而C5-C7上升。此次研究发现总体变化趋势与骨小梁体积分数相反，最大值主要集中在上后区，最小值主要在上前区；因当骨小梁表面积恒定时，骨小梁体积越大骨小梁表面积/体积比就越小，这符合该实验的微结构参数间的变化规律，见图2C。骨小梁厚度值左侧大于右侧，上后> 上前> 下前>下后的变化与骨小梁体积分数相似，见图2D。最大值集中在上前和下前区域，C5关节突值达到峰值，且两侧的变化趋势相似。骨小梁分离度最大值主要集中在上后和下后区域，最小值主要集中在上前区域，这表明关节突结构适应功能且具有明显的各向异性，见图2E。骨小梁模块因子在上前、上后区域中C2-C4上升、C4-C6下降；在下前和下后区域，从C2-C5呈下降、C5-C7呈上升趋势，最大和最小值大多集中在C7和C5水平，见图2F。"

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