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. 2020 Jan 21;236(5):916–922. doi: 10.1111/joa.13151

The relationship between facet tropism and cervical disc herniation

Xuecheng Huang 1,2, Linqiang Ye 3, Xiang Liu 4, Rui Weng 5, Jinchuan Tan 1, Pusheng Xie 1, Yang Yang 1,2, Lichang Liang 6, Wenhua Huang 1,7,✉, Xiaobing Jiang 5,✉
PMCID: PMC7163726  PMID: 31961950

Abstract

Many studies have demonstrated the association between facet tropism and disc herniation in the lumbar spine. Some of them found that lumbar disc herniation was on the side of the more sagittal facet joint interface. However, little is understood about the association of facet tropism with disc herniation in the cervical spine. As the relationship between the facet orientation and the side of cervical disc herniation (CDH) is unclear, the purpose of this study is to investigate that relationship. Ninety‐six patients with single‐level CDH (C4‐C5, C5‐C6 or C6‐C7) were included in the CDH group of this study. Another 50 age‐matched and gender‐matched healthy participants who accepted physical examinations were enrolled as the control group. The cervical facet angles of two sides were measured using axial computed tomography (CT). The intersection angle of the midsagittal line of the vertebra to the facet line represents the facet angle. Facet tropism was defined as the angular difference of 7º between the left and the right sides. Facet tropism angle was recorded as the absolute value of the difference of facet angles between two sides. There were 20 herniations at C4–C5 level, 50 herniations at C5–C6 level and 26 herniations at C6‐C7 level. The present study showed that more cases in the CDH group had facet tropism than did those in the control group at C4‐C5, C5‐C6 and C6‐C7 level (p = .021, p = .001, p = .015, respectively). The facet tropism angles in the CDH group were significantly bigger than those in the control group at C4‐C5, C5‐C6 and C6‐C7 level (p = .001, p = .002, p = .028, respectively). In the CDH group, the facet angles on the herniated side were found to be significantly bigger than those on the healthy side at C4‐C5, C5‐C6 and C6‐C7 level (p = .000, p = .000, p = .037, respectively). The findings of this present study suggest that facet tropism is associated with the disc herniation in the cervical spine. We also found that cervical disc herniates towards the side of the bigger facet angle with respect to the sagittal plane. There is a need for future studies to verify the biomechanical impact of facet tropism on CDH.

Keywords: cervical spine, computed tomography, disc herniation, facet tropism, sagittal orientation

The findings of this present study suggest that facet tropism is associated with the disc herniation in the cervical spine. We also found that cervical disc herniates towards the side of the bigger facet angle with respect to the sagittal plane. There is a need for future studies to verify the biomechanical impact of facet tropism on CDH.

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1. INTRODUCTION

Facet tropism is defined as the asymmetry between the left and the right facet joints with respect to the sagittal plane. Many studies have demonstrated the association between facet tropism and disc herniation in the lumbar spine (Farfan & Sullivan, 1967; Karacan et al. 2004; Do et al. 2011; Chadha et al. 2013; Wang et al. 2016; Li et al. 2018). Some studies have found that the lumbar disc herniated on the side of the more sagittal facet joint interface (Chadha et al. 2013; Karacan et al. 2004; Farfan & Sullivan, 1967). However, little is known about the association of facet tropism with disc herniation in the cervical spine. The relationship between the facet orientation and the side of cervical disc herniation (CDH) is also obscure. Understanding the risk factors that promote CDH is of important clinical significance in preventing or delaying degenerative changes of the cervical spine. To better understand the effects of facet tropism on CDH, this study analyzed cervical facet angles on the axial plane of computed tomography (CT).

2. MATERIALS AND METHODS

2.1. Participants

This was a retrospective analysis of patients who required CT of the cervical spine at the First Affiliated Hospital of Guangzhou University of Chinese Medicine from March 2014 to July 2018. CT images of the patients were reviewed by two experienced spinal surgeons from picture archives and communication systems. In all, 96 patients (52 males and 44 females, average age 49 years) were included in this study. The mean age of the male patients was 49 ± 10 years (range 33–68 years) and the mean age of the female patients was 50 ± 10 years (range 32–67 years).

Patients with single‐level posterolateral CDH (herniated on the left or the right side) at the C4‐C5, C5‐C6 or C6‐C7 level were included in this study as the CDH group. These patients underwent either conservative or operative treatment for their radiculopathy. They had neck pain with associated arm pain in a dermatomal pattern, and sensory, motor or reflex changes corresponding to the involved nerve root. In addition, at least one of the following positive orthopaedic tests for cervical radiculopathy was required: (1) positive Spurling test, (2) positive upper limb tension test, (3) positive cervical distraction test. Magnetic resonance imaging (MRI), which was used to prove CDH at the corresponding level, was also required.

The exclusion criteria for the CDH group were patients with other single‐level CDH (either not herniated at the C4‐C5, C5‐C6 or C6‐C7 level or herniated in the middle), multiple CDH (two levels or more), cervical spondylotic myelopathy, ossification of posterior longitudinal ligaments, cervical spinal stenosis and spondylolisthesis. Also excluded were patients with severe osteoporosis, cervical deformity, spinal infection, spinal tumours, previous cervical trauma or fractures, previous spine surgery, unclear images and incomplete information.

A control group of 50 participants (24 males and 26 females, average age 45 years) was gender‐matched and age‐matched to the CDH group. The mean age of the male participants was 45 ± 10 years (range 32–67 years) and the mean age of the female participants was 45 ± 11 years (range 27–66 years). The participants were healthy people who had accepted cervical CT for physical examinations. They were randomly selected from the same database. The previous measurements were also applied to the control group.

2.2. CT image

CT imaging was performed using a 64‐detector CT scanner (Discovery CT750 HD, GE Healthcare, USA). Detailed CT parameters were as follows: tube voltage, 120–140 kV; tube current, 140–280 mA; rotation time, 0.75 s; field of view (FOV): 350 mm; matrix, 512 × 512; slice thickness, 1.25 mm: interval, 0.625 mm; and bone window reconstruction, conventional soft tissue window.

2.3. Measurements

The cervical facet angles were measured on axial CT scans using the method described in the previous study by Xu et al. (2016). The axial images were obtained parallel to the endplate at the level of the inferior margin of the disc space (Park et al. 2001; Wang & Zhou, 2016). First, a midsagittal line was drawn passing through the centre of the cervical disc and the centre of the base of the spinous process (Chadha et al. 2013; Li et al. 2018). The facet line (Xu et al. 2016) was then drawn between the anteromedial and posterolateral margins of each facet joint. The angle between midsagittal line and facet line represents the facet angle of each side (Fig. 1α,β). Finally, the facet angles were measured automatically using a goniometer in the system. Following the standard (Rong et al. 2017b), facet tropism was defined as the angular difference of more than 7º between the left and the right sides. Facet tropism angle was recorded as the absolute value of the difference of facet angles between two sides. Two spinal surgeons, who were blinded to the presence/absence of CDH and the MRI findings, measured the facet angles. To minimize observer bias, the mean was taken as the true facet angle.

Figure 1.

Figure 1

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Illustration of the method used to measure the facet joint angles. The midsagittal line is drawn through the centre of the cervical disc (O, AO = OB) and the middle point of the base of the spinous process (M). The facet line was drawn between the anteromedial and posterolateral margins of each facet joint (C & D, E & F). The angle between midsagittal line and facet line represents the facet angle of each side (α = right facet angle, β = left facet angle)

2.4. Statistical analyses

Statistical analysis was performed using SPSS 13.0 Software (SPSS, Munich, Germany) and results were expressed as mean ± SD. Pearson correlation analysis was used to determine the intraclass correlation coefficient that could identify the reliability of two groups of facet angles measured by two observers. To determine whether the data were normally distributed, Kolmogorov–Smirnov and Shapiro–Wilk tests were conducted. The Pearson Chi‐square test was used to determine the statistical significance of categorical variables. If the data followed the normal distribution and homogeneity of variance, the independent samples t‐test was used to compare the facet tropism angles in the CDH group with those in the control group; otherwise, the Mann–Whitney U‐test was used. To compare the difference in facet angles between the herniated and the healthy sides, the paired t‐test was applied when the normal distribution was satisfied; in other cases, the Wilcoxon signed rank test was used. A value of p < .05 was considered statistically significant.

3. RESULTS

A total of 96 patients (96 herniations) were included in the CDH group. There were 20 herniations at the C4–C5 level, 50 herniations at the C5–C6 level and 26 herniations at the C6‐C7 level. All cases of disc herniation were posterolateral, including 48 discs herniated towards the left and 48 herniated towards the right side. In the control group, 50 healthy persons were measured at three levels (C4–C5, C5–C6 and C6‐C7). The intraclass correlation coefficient was 0.936, showing good consistency between the two observers for facet angle measurement.

The data were analyzed at each individual level. We found that 11/20 cases in the CDH group had facet tropism compared with 13/50 cases in the control group at the C4‐C5 level [p = .021, odds ratio (OR) 3.479, 95% confidence interval (CI) 1.176–10.286]. At the C5‐C6 level, 28/50 cases in the CDH group had facet tropism compared with the 12/50 cases in the control group (p = .001, OR 4.030, 95% CI 1.712–9.488). Moreover, at the C6‐C7 level, 10/26 cases in the CDH group had facet tropism compared with 7/50 cases in the control group (p = .015, OR 3.839, CI 1.248–11.809). The association of facet tropism with cervical disc herniation at the C4‐C5, C5‐C6 and C6‐C7 levels was found to be significant (Table 1).

Table 1.

Association of facet tropism in CDH and control group at individual level

Segment CDH   Tropism
Present Absent p‐Value
C4/5 YES 20 11 9 .021
NO 50 13 37
C5/6 YES 50 28 22 .001
NO 50 12 38
C6/7 YES 26 10 16 .015
NO 50 7 43
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The means ± SD of the facet tropism angles are listed in Table 2. The facet tropism angles in the CDH group were significantly bigger than those in the control group at the C4‐C5, C5‐C6 and C6‐C7 level, respectively.

Table 2.

Comparison of the facet tropism angles in CDH and control group

Segment CDH group (°) Control group (°) p‐Value
C4/5 9.91 ± 5.71 5.46 ± 5.13 .001
C5/6 8.51 ± 6.17 5.61 ± 4.72 .002
C6/7 6.30 ± 4.93 3.95 ± 3.24 .028
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Data are expressed as mean ± standard deviation.

The means ± SD of the facet angles in the CDH group are listed in Table 3. The facet angles on the herniated side were significantly bigger than those on the healthy side at the C4‐C5, C5‐C6 and C6‐C7 level, respectively.

Table 3.

Comparison of the facet angles between herniated side and healthy side

Segment Herniated side (°) Healthy side (°) p‐Value
C4/5 (n = 20) 100.56 ± 10.45 90.96 ± 9.75 .000
C5/6 (n = 50) 96.64 ± 10.08 91.24 ± 8.60 .000
C6/7 (n = 26) 91.24 ± 7.04 88.03 ± 9.08 .037
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Data are expressed as mean ± standard deviation.

4. DISCUSSION

The intervertebral disc and the bilateral articular processes form a three‐joint complex which ensures the stability and the mobility of the spine in all spatial planes. Alteration of any component of this complex affects the other components (Kénési & Lesur, 1985; Liu et al. 2018). The researchers (Rong et al. 2017b) suggested that facet tropism might be a risk factor for the development of cervical disc degeneration or facet degeneration. A previous study (Xu et al. 2016) has indicated a correlation between facet tropism and cervical degenerative spondylolisthesis. In contrast to that study, which found no relationship between facet tropism and CDH, in the present study we discovered that there was such a relationship.

Facet tropism was defined as the angular difference of 7º between two sides (Rong et al. 2017b). The present study showed that more cases in the CDH group had facet tropism than those in the control group at the C4‐C5, C5‐C6 and C6‐C7 levels. The relationship between facet tropism and CDH was found to be significant. The previous studies (Kim et al. 2013; Rong et al. 2017b) showed that facet tropism caused the imbalanced stress distribution at the disc. It could be hypothesized that facet tropism might affect the development of disc degeneration or even herniation by the abnormal loading. Moreover, the study by Li et al. (2018) revealed that facet tropism was one of the risk factors for lumbar disc herniation. In addition, discarding the standard of facet tropism (more than 7º) while analyzing the association of facet tropism with CDH, the facet tropism angles in the CDH group were significantly bigger than those in the control group. Therefore, facet tropism was shown to have an important influence on CDH. This reinforces the finding that facet tropism was an anatomic risk factor of CDH.

The present study also showed that the facet angles on the herniated side were significantly bigger than those on the healthy side at the C4‐C5, C5‐C6 and C6‐C7 levels. Therefore, cervical disc herniates towards the side of the bigger facet angle with respect to the sagittal plane. The facet joints play important roles in sharing load and restricting axial rotation (Pal et al. 2001; Rong et al. 2017a). If the upper vertebra rotates to the right side, the left facet could restrict the intervertebral rotational movement. The bigger the facet angle with respect to the sagittal plane, the poorer the restriction of axial rotation to the other side will be. In the facet tropism segment, the side of the bigger facet angle has poorer restriction of axial rotation compared with the other side. As for the intervertebral rotational movement, the side of the bigger facet angle sustains less facet stress, whereas the disc of the ipsilateral side bears more annulus fiber stress (Huang et al. 2018). The side of the smaller facet angle undergoes the opposite effect (more facet stress on the facet joint and less annulus fiber stress on the disc). In other words, the side of the bigger facet angle tends to be more unstable in the facet tropism segment, and the disc of the ipsilateral side is more susceptible to damage. It is possible that axial rotation produces injury to the disc on the side of the bigger facet angle by more torsional stress on the annulus fibrosus. Studies have reported that axial rotation could damage the annulus fibrosus, making the intervertebral disc more susceptible to herniation (Drake et al. 2005; Harvey‐Burgess & Gregory, 2019).

Figures 2, 3, 4 illustrate cases which had facet tropism with CDH. These figures also demonstrate that the disc herniated towards the side of the bigger facet angle at the C4‐C5, C5‐C6 and C6‐C7 levels.

Figure 2.

Figure 2

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CT and MRI of a male patient who had a left‐sided CDH at C4–C5. (A, C) Sagittal view of the cervical spine on CT & MRI. The dotted line indicates the location of the cross‐section. (B) Cross section of C4–C5 on CT. Facet angle on the herniated side was 112.86°, facet angle on the healthy side was 102.32°; facet tropism was present at the C4–C5 level. (D) Cross‐section of C4–C5 on MRI. The arrow indicated that the disc herniated towards the side of the bigger facet angle

Figure 3.

Figure 3

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CT and MRI of a male patient who had a left‐sided CDH at C5–C6. (A, C) Sagittal view of the cervical spine on CT and MRI. The dotted line indicates the location of the cross‐section. (B) Cross‐section of C5–C6 on CT. Facet angle on the herniated side was 100.65°, facet angle on the healthy side was 80.96°; facet tropism was present at the C5–C6 level. (D) Cross‐section of C5–C6 on MRI. The arrow indicated that the disc herniated towards the side of the bigger facet angle

Figure 4.

Figure 4

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CT and MRI of a female patient who had a right‐sided CDH at C6–C7. (A, C) Sagittal view of the cervical spine on CT and MRI. The dotted line indicates the location of the cross‐section. (B) Cross‐section of C6–C7 on CT. Facet angle on the herniated side was 93.42°, facet angle on the healthy side was 82.89°; facet tropism was present at the C6–C7 level. (D) Cross‐section of C6–C7 on MRI. The arrow indicates that the disc herniated towards the side of the bigger facet angle

Facet tropism may be a predisposing factor for the development of facet degeneration (Rong et al. 2017b). Facet tropism was reported to cause accelerated facet degeneration by increasing the facet contact force after lumbar total disc replacement (TDR) (Shin et al. 2013). Therefore, spinal surgeons should pay attention to patients with facet tropism after the TDR surgery. These patients may suffer unsatisfactory pain relief with the progression of facet arthrosis even after a successful implantation. However, further investigation of facet tropism as a contraindication of TDR surgery is needed. Furthermore, when deciding on the surgical method, the facet geographies should be considered carefully to minimize stress concentration after spine surgery.

There are several limitations to this study. First, though we observed that there was no CDH in the control group by cervical CT, not all of the healthy participants accepted a cervical MRI to prove that they had no CDH. Secondly, we did not obtain three‐dimensional information of the cervical facet joint such as the angles of inclination of the superior articular facets (Rong et al. 2017a). The purpose of this study is to investigate the relationship between facet tropism and CDH and therefore the facet angles were only measured on the axial plane. Thirdly, body mass index (BMI) was not included in the study. However, the previous study (Okada et al. 2009) reported that BMI had no significant correlation with cervical disc degeneration. Future studies are needed to verify the biomechanical impact of facet tropism on CDH.

5. CONCLUSION

The findings of this present study suggest that facet tropism is associated with the disc herniation in the cervical spine. We also found that cervical disc herniates towards the side of the bigger facet angle with respect to the sagittal plane. Future studies are needed to verify the biomechanical impact of facet tropism on CDH.

AUTHOR CONTRIBUTIONS

Xuecheng Huang, Linqiang Ye, Wenhua Huang and Xiaobing Jiang participated in the conception and design of the study. Xuecheng Huang, Xiang Liu, Rui Weng, Jinchuan Tan and Lichang Liang contributed to the measurement, data collection and management. Pusheng Xie and Yang Yang contributed to the statistical analysis. Xuecheng Huang, Linqiang Ye, Xiaobing Jiang and Wenhua Huang participated in the drafting of the manuscript. All authors revised and approved the final version of the manuscript.

CONFLICT OF INTEREST

The authors declare that there are no conflicts of interest.

ACKNOWLEDGEMENTS

This research was supported by the National Key R&D Program of China (2017YFC1103400), the Science and Technology Project of Guangdong Province (2016B090917001, 2017B090912006), Sanming Project of Medicine in Shenzhen (SZSM201612019) and Science Research Program of Foshan City (2017AG100243) grant funds. We greatly appreciate the help of Jingmin Huang in editing the English text.

Huang X, Ye L, Liu X, et al. The relationship between facet tropism and cervical disc herniation. J. Anat. 2020;236:916–922. 10.1111/taja.13151

Huang and Ye contributed equally to this study and share the first authorship.

The submitted manuscript does not contain information about medical device(s)/drug(s).

Contributor Information

Wenhua Huang, Email: huangwenhua2009@sina.com.

Xiaobing Jiang, Email: spinedrjxb@sina.com.

DATA AVAILABILITY STATEMENT

The data used to support the findings of this study are available from the corresponding author upon request. We are not going to share the data.

REFERENCES

  1. Chadha, M. , Sharma, G. , Arora, S.S., Kochar, V. (2013) Association of facet tropism with lumbar disc herniation. European Spine Journal 22, 1045–1052. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Do, D.H. , Taghavi, C.E. , Fong, W. , Kong, M.H. , Morishita, Y. , Wang, J.C. (2011) The relationship between degree of facet tropism and amount of dynamic disc bulge in lumbar spine of patients symptomatic for low back pain. European Spine Journal 20, 71–78. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Drake, J.D. , Aultman, C.D. , McGill, S.M. , Callaghan, J.P. (2005) The influence of static axial torque in combined loading on intervertebral joint failure mechanics using a porcine model. Clin Biomech (Bristol, Avon) 20, 1038–1045. [DOI] [PubMed] [Google Scholar]
  4. Farfan, H.F. , Sullivan, J.D. (1967) The relation of facet orientation to intervertebral disc failure. Canadian Journal of Surgery 10, 179–185. [PubMed] [Google Scholar]
  5. Harvey‐Burgess, M. , Gregory, D.E. (2019) The Effect of Axial Torsion on the Mechanical Properties of the Annulus Fibrosus. Spine (Phila Pa 1976) 44, E195–E201. [DOI] [PubMed] [Google Scholar]
  6. Huang, X. , Ye, L. , Wu, Z. , et al. (2018) Biomechanical effects of lateral bending position on performing cervical spinal manipulation for cervical disc herniation: a three‐dimensional finite element analysis. Evidence‐Based Complementary and Alternative Medicine: eCAM 2018, 2798396. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Karacan, I. , Aydin, T. , Sahin, Z. , Cidem, M. , Koyuncu, H. , Aktas, I. , Uludag, M. (2004) Facet angles in lumbar disc herniation: their relation to anthropometric features. Spine (Phila Pa 1976) 29, 1132–1136. [DOI] [PubMed] [Google Scholar]
  8. Kénési, C. , Lesur, E. (1985) Orientation of the articular processes at L4, L5, and S1. Possible role in pathology of the intervertebral disc. Anat Clin 7, 43–47. [DOI] [PubMed] [Google Scholar]
  9. Kim, H.J. , Chun, H.J. , Lee, H.M. , et al. (2013) The biomechanical influence of the facet joint orientation and the facet tropism in the lumbar spine. Spine Journal 13, 1301–1308. [DOI] [PubMed] [Google Scholar]
  10. Li, Z. , Yang, H. , Liu, M. , Lu, M. , Chu, J. , Hou, S. , Hou, T. (2018) Clinical characteristics and risk factors of recurrent lumbar disk herniation: a retrospective analysis of three hundred twenty‐one cases. Spine (Phila Pa 1976) 43, 1463–1469. [DOI] [PubMed] [Google Scholar]
  11. Liu, X. , Zhao, X. , Long, Y. , et al. (2018) Facet sagittal orientation: possible role in the pathology of degenerative lumbar spinal stenosis. Spine (Phila Pa 1976) 43, 955–958. [DOI] [PubMed] [Google Scholar]
  12. Okada, E. , Matsumoto, M. , Ichihara, D. , et al. (2009) Aging of the cervical spine in healthy volunteers: a 10‐year longitudinal magnetic resonance imaging study. Spine (Phila Pa 1976) 34, 706–712. [DOI] [PubMed] [Google Scholar]
  13. Pal, G.P. , Routal, R.V., Saggu, S.K. (2001) The orientation of the articular facets of the zygapophyseal joints at the cervical and upper thoracic region. Journal of Anatomy 198, 431–441. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Park, J.B. , Chang, H. , Kim, K.W., Park, S.J. (2001). Facet tropism: a comparison between far lateral and posterolateral lumbar disc herniations. Spine (Phila Pa 1976) 26, 677–699. [DOI] [PubMed] [Google Scholar]
  15. Rong, X. , Liu, Z. , Wang, B. , Chen, H. , Liu, H. (2017a) The facet orientation of the subaxial cervical spine and the implications for cervical movements and clinical conditions. Spine (Phila Pa 1976) 42, E320–E325. [DOI] [PubMed] [Google Scholar]
  16. Rong, X. , Wang, B. , Ding, C. , et al. (2017b) The biomechanical impact of facet tropism on the intervertebral disc and facet joints in the cervical spine. Spine Journal 17, 1926–1931. [DOI] [PubMed] [Google Scholar]
  17. Shin, M.H. , Ryu, K.S. , Hur, J.W. , Kim, J.S. , Park, C.K. (2013) Association of facet tropism and progressive facet arthrosis after lumbar total disc replacement using ProDisc‐L. European Spine Journal 22, 1717–1722. [DOI] [PMC free article] [PubMed] [Google Scholar]
  18. Wang, H. , Zhou, Y. (2016) Facet tropism: possible role in the pathology of lumbar disc herniation in adolescents. Journal of Neurosurgery Pediatrics 18, 111–115. [DOI] [PubMed] [Google Scholar]
  19. Wang, H. , Zhang, Z. , Zhou, Y. (2016) Irregular alteration of facet orientation in lumbar segments: possible role in pathology of lumbar disc herniation in adolescents. World Neurosurgery 86, 321–327. [DOI] [PubMed] [Google Scholar]
  20. Xu, C. , Lin, B. , Ding, Z. , Xu, Y. (2016) Cervical degenerative spondylolisthesis: analysis of facet orientation and the severity of cervical spondylolisthesis. Spine Journal 16, 10–15. [DOI] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

The data used to support the findings of this study are available from the corresponding author upon request. We are not going to share the data.

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