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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 11  |  Issue : 4  |  Page : 227-231

Morphological cross-sectional study of anatomical landmarks for foramen transversarium in dry human cervical vertebrae and its surgical importance


1 Associate Professor, Department of Anatomy, Himalayan Institute of Medical Sciences, Swami Rama Himalayan University, Dehradun, Uttarakhand, India
2 Professor, Department of Anatomy, Himalayan Institute of Medical Sciences, Swami Rama Himalayan University, Dehradun, Uttarakhand, India

Date of Submission09-Sep-2022
Date of Decision01-Oct-2022
Date of Acceptance06-Oct-2022
Date of Web Publication29-Oct-2022

Correspondence Address:
Kishore Chandra Thakur
Flat Number 33, Ground Floor, Lane-2, Madhu Vihar, Haripur, Kanwali, GMS Road, Near Jewel Residency, Dehradun - 248 001, Uttarakhand
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/NJCA.NJCA_149_22

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  Abstract 


Background: Surgeries such as discectomy, intervertebral fusion, anterior microforaminotomy, and anterior screw fixation can damage neurovascular content of foramen transversarium of cervical vertebrae. The aim of this study was to measure outer limit and strength of foramen transversarium with help of uncinate process, anterior tubercle, and anterior root thickness. Methodology: A total of 54 dried human cervical vertebrae collected from anatomy department. Only third to seventh cervical vertebrae were included. Digital vernier caliper was used to measure transverse length (TL) of body, bilateral distance of uncinate process, and anterior tubercle from mid of cervical vertebral body and thickness of mid of anterior root. Results: Mean TL of body of cervical vertebrae was 23.87 mm, mean distance of uncinate process from vertebral body was 9.14 mm on right and 8.49 mm on left (P < 0.0001), mean distance of anterior tubercle from vertebral body was 20.81 mm on right and 20.36 mm on left (P < 0.014), mean thickness of anterior root was 1.48 mm on right and 1.36 mm on left (P < 0.1003) whereas mean distance between uncinate process was 18.4 mm. Conclusion: Mean TL of cervical vertebrae was 23.8 mm, distance of uncinate process was 8.81 mm from the center, distance of anterior tubercle to uncinate process was 20.72 mm and thickness of anterior root was 1.43 mm. Uncinate process and anterior tubercle distance from mid of cervical vertebrae body can help surgeons to identify zone and avoid injury to contents.

Keywords: Cervical vertebrae, foramen transversarium, morphometry, uncinate process


How to cite this article:
Thakur KC, Jethani SL. Morphological cross-sectional study of anatomical landmarks for foramen transversarium in dry human cervical vertebrae and its surgical importance. Natl J Clin Anat 2022;11:227-31

How to cite this URL:
Thakur KC, Jethani SL. Morphological cross-sectional study of anatomical landmarks for foramen transversarium in dry human cervical vertebrae and its surgical importance. Natl J Clin Anat [serial online] 2022 [cited 2023 Feb 6];11:227-31. Available from: http://www.njca.info/text.asp?2022/11/4/227/359876




  Introduction Top


Cervical nerve radiculopathy, spinal curvature instability, traumatic fracture, or many other conditions leading to compression of neurovascular structure need surgical intervention.[1] Common surgery needed in such conditions is cervical foraminotomy, discectomy, and fixation by screw and plate. Cervical vertebrae have foramen transversarium in transverse process and usually only one foramen seen on each side. The size and shape of foramen on each side are same in comparison, but in some studies, variations have been reported.[2],[3] Vertebral artery, vertebral vein, and vertebral nerves pass through this foramen. Damage of vertebral artery and nerve root is common in such surgical procedures.[4],[5],[6] Around 0.19% nerve root damage was reported by Flynn while performing anterior cervical surgery.[7] Ischemic consequences are seen in case of vertebral artery damage during cervical spine surgery and that too with the anterior approach.[8],[9],[10]

Various studies report the measurement of vertebral artery and nerve from different parts of the uncinate process. Anterior tubercle and longi colli were also taken into account to measure the distance of neurovascular structure. In surgery like discectomy mostly the Luschka joint is exposed with an anterior approach. In decompression surgery, the uncinate process is approached lateral to medial, and in surgeries for radiculopathy and myelopathy foramen is widened by dissecting bone around the uncinate process. Considering the importance of the uncinate process and its relation with neurovascular structures, the importance of anterior tubercle as a landmark, mid of vertebral body which is easily visible during the anterior approach and allows surgeons to outline the area of the foramen and passing structures. In addition, too much-reduced distance between uncinate processes will hint about crumbling of the vertebral body.

Knowing of anatomical landmarks around foramen transversarium from anterior aspect of body of cervical vertebrae can help surgeon to work cautiously near those areas. Anterior tubercle and uncinate process are important bony projections near foramen transversarium. The thickness of anterior root forming anterior boundary of foramen also plays role in maintaining the morphology of foramen. The purpose of this study is to measure the distance of those bony landmarks, i.e., anterior tubercle and uncinate process from mid of cervical vertebral body.


  Materials and Methods Top


Cross-sectional study was done by collecting a total of 54 dry human cervical vertebrae from the bone bank of the department of anatomy at the Himalayan Institute of Medical Sciences. Considering the study applicable over 50% of population with confidence level 85% and margin of error to 10.18%, minimum sample size required was 50. The study protocol was approved by Research Committee and Ethical Committee of the Institute (Letter no. SRHU/HIMS/ETHICS/2019/26). Only cervical vertebrae from third to seventh were included. Atlas and axis cervical vertebra, damaged, malformed vertebrae were excluded. Out of 54 bones, four were of C7 identified by the absence of anterior tubercle and absence of bifid spine.

Age, sex, and race of bone were not considered due to nonavailability of data but all bones were procured from adult cadaver as per record. Different studies suggest that the transverse length (TL) of C3 to C7 vertebral body ranges from 22.80 mm to 26.12 with increasing diameter from above down, the distance of the base of uncinate process from the midpoint of anterosuperior margin of vertebral body increases as the distance from the tip of uncinate process to the nearest vertebral body reduces from above down. As the data of individual vertebrae will be more cumbersome and less practical, pooled averages were considered for all parameters of the study from C3 to C7.

Parameters noted in the study

Transverse length measured from mid of body (TL) and mid of transverse diameter marked and extended over upper margin of anterior part of body of vertebrae. From extended marked mid-point on upper margin of anterior part of body of vertebra, distance of right and left anterior tubercle measured (DRAT/DLAT) and distance of anterior end of base of right and left uncinate process measured (DRUP/DLUP) [Figure 1] and [Figure 2]. In addition to that other parameter measured were thickness of anterior root and distance between two uncinate process.[11],[12]
Figure 1: (a) Schematic depiction of transverse length, distance of right and anterior tubercle from mid of each cervical vertebral body (DRAT/DLAT); (b) Transverse length measurement and (c) Distance of anterior tubercle

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Figure 2: (a) Schematic depiction of distance of right and left uncinate process from mid of cervical vertebral body (DRUP), maximum distance between two uncinate processes (DUP) (b) Measurement of distance between two uncinate processes and (c) Measurement of maximum thickness of right anterior root

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All measurements were taken using digital vernier calipers. The measurements were taken two times and average values were considered to reduce inter-observer error. All measurements were taken in millimeter.

Statistical analysis

Microsoft® Excel® 2019 MSO (Version 2209 Build 16.0.15629.20200) 64-bit (Microsoft Office Home and Student 2019), (Washington, USA) was used to calculate mean, standard deviation with standard error, and t-test applied to calculate mean difference in distance of uncinate process of the right and left side from mid-point, in distance of anterior tubercle of right and left side from mid-point and thickness of right and left anterior root. A P-value of 0.05 or lower is considered statistically significant.


  Results Top


The mean TL of cervical vertebrae was 23.8 mm, the distance of uncinate process was 8.81 mm from the center, distance of anterior tubercle to uncinate process was 20.72 mm, and the thickness of anterior root was 1.43 mm [Table 1]. The significant difference was seen (P = 0.0001) when the distance of uncinate process of right and left side was compared. The distance of anterior tubercle of right and left was found to be significant (P = 0.010). The mean thickness of anterior root of right was 1.48 mm and 1.36 mm and no significant difference was seen (P > 0.05). There was no way to counter or adjust confounder and therefore confidence interval was 85%.
Table 1: Result of parameters measured in millimetres

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  Discussion Top


Dimension of vertebral body such as anteroposterior length, TL, and body height has been studied by many researchers to provide anatomical knowledge necessary during surgical procedures on cervical vertebrae like reconstruction or any plate fixation.[13] In the present study, TL of cervical body has been measured and considered for sake of finding mid-point of body and taking measurements of other landmarks from mid-point. The mean TL of cervical body in the present study was compared with other studies [Table 2].
Table 2: Comparative study of mean transverse length of cervical vertebral body

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The outcomes of present study were inline with previous studies except the findings of Tan et al., [Graph 1].[18] This may be due to ethnic or racial variations of the specimen considered.



Surgeons use uncinate process as a landmark to prevent damage to vertebral artery and nerve during procedure around it. The uncinate process is hook-shaped raised structure present on lateral part of body of cervical vertebrae. Pait et al. and Oh et al. studied the vertebral artery relation to uncinate process.[18] Kim et al. did cadaveric study to find relation of uncinate process and vertebral artery and found the shortest distance from upper tip of process to artery was 4.32 ± 0.84 mm.[19] They further notified that there was a significant difference between right and left side relation of uncinate process and vertebral artery and height of uncinate process. Ebraheim et al. measured distances between longus coli muscle and vertebral artery in their cadaveric study and found anatomical relationship between them which was very useful for surgeons, but this relationship become useless once longus coli muscles removed during surgery.[20],[21] In that case, bony landmark like uncinate process and anterior tubercle has additional advantage.

In the present study, these bony landmarks have been chosen for the same reason. Distance of anterior aspect of uncinate process and anterior tubercle from mid of vertebral body can be beneficial in cases where longus coli has been removed. The thickness of anterior root of both sides further add anatomical fact about strength of anterior boundary of foramen transversarium which can be kept in mind while performing surgery nearby foramen.[22] In the present study, the mean distance of anterior part of base of uncinate process from mid of superior border of vertebral body was 9.14 mm on right side and 8.49 mm on left side and there was a significant difference between them. Whereas the distance of right and left anterior tubercle from mid of vertebral body was 20.95 mm and 20.49 mm, respectively, and significant difference was seen between them.

During surgery anterior tubercle can be located to identify boundary and extent of foramen transversarium or data can be utilized to find mean distance of it. While doing surgery to decompress nerve or vessel by cutting bone around uncinate process, this study data can give fair idea about its anterior boundary location that further helps surgeon to prevent damaging content of foramen. The thickness of anterior root can make a surgeon cautious when working over that area as thickness directly defines the strength of anterior boundary foramen transversarium and its damage can further complicate surgical complication.[22] The mean distance between two uncinate process was 18.4 mm and it has crucial role in identifying normal contour of vertebral body from abnormal due to collapse of vertebral body either because of bone removal or any other pathology. This parameter needs more emphasis and evaluation in future to be more relevant in relation to population, age, and gender.

This study finds its application difficult in case of variations present in foramen transversarium in form of accessory foramen,[23] course of vertebral artery,[24] and gender variation of dimension of foramen and foramen uncus ridge distance.[25],[26]

Considering the common surgeries related to cervical vertebrae from anterior aspect, there are more chances of damage to neurovascular structures lying within foramen transversarium. Many studies although gave distance relation of vascular structure with uncinate process and longus coli but these remain inefficient when longus coli get removed or uncinate process not well defined. In that case, landmarks such as anterior tubercle and uncinate process come into play to give additional support to surgeon to outline limit of foramen and data about thickness of anterior root give caution alert to surgeons while performing over that area. Not much data available about thickness of anterior root depicting strength of anterior wall of foramen and therefore present study adds more to it for more evaluation in future.

Limitations of the study

Although bones were procured from adult cadavers of males and females but no uniform data or record available, hence based on which it cannot be claimed that all bones of sample belong to any specific sex, age, ethnicity, or population. Hence, there can be probability of bias if they belong to any one group such as gender, age, and population.


  Conclusions Top


Mean TL of cervical vertebrae was 23.8 mm, distance of uncinate process was 8.81 mm from the center, distance of anterior tubercle to uncinate process was 20.72 mm and thickness of anterior root was 1.43 mm.

Acknowledgment

I deeply pay my regards and gratitude to all those who donated their body to enlighten medical students and faculty who further can utilized their knowledge for the welfare of society.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Horwitz NH, Rizzoli HV. Herniated intervertebral discs and spinal stenosis. In: Horwitz NH, Rizzoli HV, editors. Postoperative Complications of Extracranial Neurosurgery. Baltimore: Williams & Wilkins; 1987. p. 30-98.  Back to cited text no. 4
    
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Smith MD, Emery SE, Dudley A, Murray KJ, Leventhal M. Vertebral artery injury during anterior decompression of the cervical spine. A retrospective review of ten patients. J Bone Joint Surg Br 1993;75:410-5.  Back to cited text no. 6
    
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Flynn TB. Neurologic complications of anterior cervical interbody fusion. Spine (Phila Pa 1976) 1982;7:536-9.  Back to cited text no. 7
    
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Hardy RW. Complication of anterior cervical surgery. In: Tarlov EC, editor. Complications of Spinal Surgery. Park Ridge: American Association of Neurological Surgeons; 1991. p. 85-94.  Back to cited text no. 8
    
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Schneider RC. Treatment of cervical spine disease. In: Schneider RC, Kahn EA, Crossby EC, Taren JA, editors. Correlative Neurosurgery. 3rd ed. Springfield: Charles C Thomas; 1982. p. 1094-174.  Back to cited text no. 9
    
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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2]



 

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