Abstract

Background: Utilizing computed tomography (CT) studies, we correlated cervical spinal canal diameters (SCDs) with pedicle size between the C3 and C7 levels to more safely perform posterior cervical surgery.

Methods: We retrospectively analyzed CT studies for 71 patients with cranial or spinal disorders and correlated the cervical SCD with the pedicle outer width (POW) between the C3 and C7 levels. Patients were divided into normal (SCD ≥12 mm at any level, n = 30) and stenosis groups (SCD n = 41).

Results: C7 exhibited the largest SCD and POW values, while C3 and C4 exhibited the smallest SCD and POW values. Moderate correlations (r = 0.3, P = 0.002) were observed at the C3 and C4 levels but no significant correlations were observed from the C5 to C7 levels. For SCD values, the normal group demonstrated significantly greater values between the C3 and C7 levels versus the stenosis group. For POW values, only the C4 level differed significantly between the two groups (P = 0.014, Mann–Whitney U-test).

Conclusion: Preoperative pedicle size evaluation remains an essential manoeuvre before performing cervical C3–C7 pedicle screw placement. In 71 cervical CT studies, we found no consistent correlation between POW and SCD values, indicating that it is difficult to estimate POW values based on spinal canal size.

Keywords: Cervical spine, Computed tomography, Pedicle size, Spinal canal

INTRODUCTION

Posterior cervical spinal instrumentation has evolved significantly, enabling rigid fixation and spinal malalignment correction.[ 1 , 5 ] For these procedures, pedicle size assessment is essential for accurate screw insertion.[ 2 - 8 ] Most spine surgeons expect that pedicle size correlates with the corresponding spinal canal diameter (SCD)/size. However, despite numerous studies on pedicle size,[ 2 - 4 , 6 ] only a few studies have correlated pedicle size with cervical canal diameters. Here, we correlated CT findings for SCD and pedicle size between the C3 and C7 levels to enhance the safety of cervical pedicle screw instrumentation.

MATERIALS AND METHODS

Our Institution’s Ethics Committee approved this retrospective study. Seventy-one patients with cranial or spinal disorders underwent multislice computed tomography (CT) scans between 2010 and 2022 for various pathologies [ Tables 1 and 2 ]. Using CT images, we correlated cervical SCDs and pedicle outer widths (POWs) from the C3 to C7 levels [ Figure 1a ].[ 9 ] Axial images parallel to the vertebral body endplates were used to evaluate the POW. The largest pedicle diameter was selected, and POW was measured as the mediolateral diameter of the pedicle isthmus perpendicular to the axis [ Figure 1b ].[ 5 , 8 ]Based on these measurements, patients were divided into normal (SCD ≥12 mm at any level, n = 30) and stenosis groups (SCD <12 mm at any level, n = 41).[ 5 ]

Table 1:

Patient demographics and their diagnosis.

Table 2:

Multislice CT scanners used in this study.

Figure 1:

Axial computed tomography scan showing the measured parameters of the cervical spine from C3 to C7. (a) Spinal canal diameter (SCD) (red arrow). (b) Pedicle outer width (POW) (red arrow).

Statistics

Categorical variables were analyzed using the Chi-square and the Mann–Whitney U-tests. Spearman’s rank correlation coefficient (r) was used to assess the correlation between SCD and POW at each vertebral level. All statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS) ver. 24.0 (SPSS Inc, Chicago, IL, USA), and statistical significance was set at P <0.05.

RESULTS

SCD values

The average SCD values from C3 to C7 level were evaluated; C7 showed the largest diameter, and C4 showed the smallest diameter [ Table 3 ]. Males exhibited significantly larger SCD values at the C3 and C6 levels versus females (C3: P = 0.014, C6: P = 0.031, Mann– Whitney U-test).

Table 3:

Measurement of the SCD of the cervical spine.

POW values

The average POW values between C3 and C7 were assessed; we found POW values gradually increased (i.e., trend) from C3 (smallest POW) to C7 (largest) [ Table 4 ]. Further, significant differences in POW vales at all vertebral levels were observed for males versus females (P = 0.00, Mann– Whitney U-test).

Table 4:

Measurement of the POW of the cervical spine.

Correlation SCD and POW

Spearman’s rank correlation between SCD and POW revealed moderate correlations at the C3 and C4 levels but no significant correlations between C5 and C7 (C3: r = 0.361, P = 0.002, C4: r = 0.367, P = 0.002) [ Table 5 ]. Although there were no significant differences in the baseline characteristics between the two groups, the normal group exhibited significantly greater SCD values from C3 to C7 versus the stenosis group, and the POW values at the C4 level were significantly different between the two groups (P = 0.014, Mann–Whitney U-test) [ Table 6 ].

Table 5:

Correlation between the SCD and the POW of the cervical spine.

Table 6:

Comparisons of baseline characteristics and spinal canal parameters between the normal and stenosis groups.

DISCUSSION

Few other studies have evaluated the association between pedicle size and SCD.[ 5 , 7 , 8 ] Miyazaki et al.[ 5 ] examined cervical spine morphology, including POW and SCD, in 52 patients; the developmental spinal canal stenosis group (SCD <12 mm) exhibited smaller mean POW values at two levels (C6 and C7) versus the normal group (SCD ≥12 mm); this was similar to our finding of a significant difference in POW values at C4. Toki et al.[ 7 ] compared CT data between patients with CSM and the normal population, reporting that male patients with CSM had smaller POW values at the C3 and C7 levels, while female patients with CSM had greater POW values at the C4–C6 levels.[ 7 ] Wang et al.[ 8 ] measured the radiological parameters of 120 Chinese patients, divided into two groups based on the Pavlov ratio; they reported that the stenosis group (Pavlov ratio <0.82) exhibited greater POW values at the C3–C7 levels versus the non-stenosis group (Pavlov ratio ≥0.82).[ 8 ]

In this study, we investigated the potential correlation between SCD and POW in the cervical spine. Analyzing the radiographical data of 71 patients, we identified moderate correlations only at the C3 and C4 levels. Interestingly, when participants were grouped according to SCD, no significant differences were observed in POW values except for the C4 level. The present and previous studies underscore the challenge of establishing a consistent trend in the relationship between SCD and POW.

CONCLUSION

This study demonstrated the inconsistent correlation between CT-documented POW and SCD values throughout the C3– C7 cervical spine. Further studies are needed to correlate SCD with pedicle size better to ensure safety for accurate pedicle screw placement better.

Ethical approval

The research/study was approved by the Institutional Review Board at the Department of Neurosurgery, Graduate School of Medical and Dental Sciences, Kagoshima University, number 200033-2, dated March 25, 2024.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.

References

1. Abumi K. Cervical spondylotic myelopathy: Posterior decompression and pedicle screw fixation. Eur Spine J. 2015. 24: 186-96

2. Chazono M, Soshi S, Inoue T, Kida Y, Ushiku C. Anatomical considerations for cervical pedicle screw insertion: The use of multiplanar computerized tomography reconstruction measurements. J Neurosurg Spine. 2006. 4: 472-7

3. Chazono M, Tanaka T, Kumagae Y, Sai T, Marumo K. Ethnic differences in pedicle and bony spinal canal dimensions calculated from computed tomography of the cervical spine: A review of the English-language literature. Eur Spine J. 2012. 21: 1451-8

4. Mahiphot J, Lamsaard S, Sawatpanich T, Sae-Jung S, Khamanarong K. A morphometric study on subaxial cervical pedicles of Thai people. Spine. 2018. 44: E579-84

5. Miyazaki M, Takita C, Yoshiiwa T, Itonaga I, Tsumura H. Morphological analysis of the cervical pedicles, lateral masses, and Laminae in developmental canal stenosis. Spine (Phila Pa 1976). 2010. 35: E1381-5

6. Munusamy T, Thien A, Anthony MG, Bakthavachalam R, Dinesh SK. Computed tomographic morphometric analysis of cervical pedicles in a multi-ethnic Asian population and relevance to subaxial cervical pedicle screw fixation. Eur Spine J. 2015. 24: 120-6

7. Toki S, Higashino K, Manabe H, Morimoto M, Sugiura K, Tezuka F. Morphometric analysis of subaxial cervical spine with myelopathy: A comparison with the normal population. Spine Surg Relat Res. 2021. 5: 34-40

8. Wang S, Yang G, Zhu C, Kang J, Wang Q. Morphological analysis for subaxial cervical pedicle screw insertion in developmental and non-developmental canal stenosis. BMC Musculoskelet Disord. 2019. 20: 205

9. Yukawa Y, Kato F, Suda K, Yamagata M, Ueta T. Age-related changes in osseous anatomy, alignment, and range of motion of the cervical spine. Part I: Radiographic data from over 1200 asymptomatic subjects. Eur Spine J. 2012. 21: 1492-8