Pedicle Morphometry of Sub Axial Cervical Spine using Computed Tomography Scans among Adult Ugandan Population

TL;DR: The morphometric dimensions of pedicles in the sub axial cervical spine among the adult Ugandan population, including females and males with a normal cervical CT scan, were determined to be significantly smaller than in males.

Abstract: Background: Accurate placement of pedicle screws in the sub axial cervical spine requires precise understanding of vertebrae anatomy. Little is known about the morphometric characteristics of the sub axial cervical pedicle in the Ugandan population. The objective of the study was to determine the morphometric dimensions of pedicles in the sub axial cervical spine among the adult Ugandan population. Methods: We conducted a cross sectional study from March to November 2019 among adult Ugandans with a normal cervical CT scan at Nsambya hospital in Kampala. Eligible participants were consecutively recruited into the study. Data on baseline characteristics and pedicle dimensions from the CT scan findings were collected using a structured questionnaire and analysed using Stata 13.0. Pedicle dimensions for the different levels of sub axial cervical vertebrae were summarised as means and standard deviations, the Mann Whitney test was used to compare pedicle dimensions for the different vertebrae level among females and males on both right and left side and the level of significance was set at 0.05. Results: A total of 700 sub axial cervical pedicles (C3-C7) from 49 males and 21 female participants were studied. Pedicle width diameter showed cephalo-caudal gradual increment from C3 [1.65(0.63) mm] to [3.46(0.75) mm] at C7. Pedicle height also showed an increase caudally with smallest diameter at C3 [1.98(0.76) mm] and largest at C5 in females [3.67(6.42) mm] and at C7in males [3.83(0.76) mm]. The pedicle height was wider than the pedicle width at all levels. The pedicle chord length gradually increased caudally in both sexes ranging from [29.08(1.35) mm] at C3 to [32.53(3.19) mm] at C7. The axial angles were oriented medially and showed no consistent trend ranging between 500 and 530. The sagittal angles decreased as one moved from C3 to C7. The dimensions of females were significantly smaller than in males.Conclusion: Pedicle endosteal width was smaller than pedicle height dimensions at all levels. Pedicle cord length increased caudally. The pedicle dimensions except angulations, were smaller in females than in males.

Summary

Introduction

• Accurate placement of pedicle screws in the sub axial cervical spine requires precise understanding of vertebrae anatomy, also known as Background.
• The objective of the study was to determine the morphometric dimensions of pedicles in the sub axial cervical spine among the adult Ugandan population.
• Eligible participants were consecutively recruited into the study.
• The sagittal angles decreased as one moved from C3 to C7.

Background

• There are a number of well researched and documented sub-axial cervical spine fixation methods for different pathologies.
• Therefore, the objective of this study was to describe the morphometric dimensions of the sub axial cervical spine pedicles among adult Ugandans using computed tomography (CT) scans.
• This machine was a 2013 model, installed in January 2014 and was calibrated regularly.
• The demographic characteristics of patients, whose images were included, were noted.
• The following pedicle morphometric measurements were taken;.
• Inner medio-lateral diameter of the isthmus of the pedicle or width of cancellous core, also known as Inner pedicle width.

Description of study participants

• A total of 70 participants were enrolled into the study, 49 (%) were males.
• The age of the participants ranged from 19 to 76 years with a median age of 33.5years and the interquartile range was 20.
• A total of 700 sub axial cervical spine pedicles (C3-C7) were studied.

Pedicle width (PW)

• The mean PW was smaller in females than in males at all levels (P<0.05).
• The results are summarized in table 1 below.

Pedicle chord length

• The mean chord length was smaller in females than in males at all levels (P<0.05).
• There was weak correlation between chord length and BMI.
• The results are summarised in table 2 below.

Pedicle axial angle

• There was no statistically significant difference between genders at any level (p>0.05).
• The results are summarized in table 3 below.

Pedicle Height (PH)

• The mean PH was smaller in females than in males at all levels (P<0.05).
• There was a gradual increase in mean PH advancing caudally in the sub axial cervical spine.
• There was no correlation between PH and BMI at all levels.
• The results are summarised in table 4 below.

Pedicle sagittal angle (PSA)

• There were no statistical differences among genders at all levels (P>0.05).
• The results are summarised in table 5 below.

Discussion

• 11, 12) and this can be explained by the fact that most patients who required cervical CT scans were those involved in trauma of which most are males.
• This was in keeping with the findings of the studies done locally for thoracic and lumbar spines as well as studies done in other populations such as Thailand and in the caucasians (3, 13).
• This could be due the fact that genetically females have a relatively smaller and shorter stature compared to male counter parts.(14, 15) Pedicle endosteal /inner width Pedicle endosteal width in this study was the smallest parameter of all parameters and it continuously increased from C3 to C7 and this was in keeping with previous studies (3, 16, 17).
• The pedicle width of the Ugandan population studied is smaller than that reported in studies elsewhere among Europeans and Americans as reported a systematic review study (18).
• Hence it is only at C7 that a 3.5mm pedicle screws can be inserted bilaterally in both males and females because they have endosteal minimum diameter of more than 2.5mm.

Chord length

• The chord length was longer in men than in female counterparts and the differences was statistically significant (p<0.05) at all levels which was in agreement in other studies(21).
• The overall pedicle endosteal width is less than 4mm at all levels in both genders and it increases from C3 to C7 Pedicle endosteal width is smaller than pedicle height dimensions at all levels hence it is the primary dimension used to determine the screw diameter and it increases caudally.
• The pedicles of the upper sub axial cervical spine are oriented cranially then become horizontal in the lower sub axial cervical pedicles and they are oriented medially to the midline Pedicle cord length increases caudally and it’s the determinant for the screw length.
• There is no correlation between pedicle dimensions and BMI in the study population.

Recommendations.

• A 4.5mm and 4mm pedicle screw diameter is not safe to be used in the sub axial cervical spine transpedicular fixation among Ugandan populations due the smaller pedicle width.
• Hence advise the different spine implant designers and manufacturers to customize cervical spine pedicle screws to Uganda’s population due to the smaller sizes of their dimensions as compared to other populations.
• The pedicle screw length ranging from 29mm to 32mm and axial angulation of 500 from the midline is appropriate in their population.
• Transpedicular screw insertion should be avoided in higher sub axial cervical pedicles because such attempt can be detrimental in Uganda’s population because of the smaller pedicle dimensions.

Ethics, approval and consent:

• Approval for this study was obtained from the School of medicine Research and Ethics Committee of Makerere University and Nsambya Hospital Research and Ethics Committee.
• Written informed consent was obtained from all participants.
• The data for this study is available on request and interested researchers may submit queries related to data access to SOMREC (rresearch9@gmail.com) or corresponding author (jssebuggwawo@gmail.com).

Figures

Table 3. Table Showing axial cervical pedicle angles of 70 participants

Table 2. Table Showing cord length (cl) of 70 participants

Table 1 Showing pedicle width of 70 participants

Table 5. Table showing pedicle sagittal cervical angles of pedicles of 70 participants

Full text

Pedicle Morphometry of Sub Axial Cervical Spine
using Computed Tomography Scans among Adult
Ugandan Population
Ssebuggwawo Jonathan (  jssebuggwawo@gmail.com )
Makerere University
Wani Muzeyi
Makerere University
Erem Geoffrey
Makerere University
Waiswa Gonzaga
Makerere University
SSekitooleko badru
Makerere University
Kajja Isaac
Makerere University
Research Article
Keywords: Cervical pedicle, Cervical pedicle screw, Pedicle Morphometric, Pedicle dimensions, Cervical
spine xation, Computed Tomography
Posted Date: July 7th, 2021
DOI: https://doi.org/10.21203/rs.3.rs-673306/v1
License:   This work is licensed under a Creative Commons Attribution 4.0 International License. 
Read Full License

1
Pedicle morphometry of sub axial cervical spine using Computed Tomography scans
among adult Ugandan population.
Ssebuggwawo Jonathan
1§
Wani Muzeyi
4
Erem Geoffrey
2
Waiswa Gonzaga
1
SSekitooleko
badru
3
Kajja Isaac
1
1. Department of Orthopaedic surgery, school of medicine, college of health sciences,
Makerere University.
2. Department of Radiology, school of medicine, college of health sciences, Makerere
University.
3. Department of general surgery, school of medicine, college of health sciences,
Makerere University.
4. Clinical epidemiology unit, school of medicine, college of health sciences, Makerere
University.
§corresponding author: Ssebuggwawo Jonathan (SJ)
Email: jssebuggwawo@gmail.com
Tel: +256789980821
Email addresses of co-author;
KI: kajja133@gmail.com
EG: dreremgeoffrey@gmail.com
WG: drgwaiswa2000@gmail.com
WM: wanixxl@gmailcom
SB: sbadru2050@gmail.com
Abstract
Background: Accurate placement of pedicle screws in the sub axial cervical spine requires
precise understanding of vertebrae anatomy. Little is known about the morphometric
characteristics of the sub axial cervical pedicle in the Ugandan population. The objective of
the study was to determine the morphometric dimensions of pedicles in the sub axial cervical
spine among the adult Ugandan population.
Methods: We conducted a cross sectional study from March to November 2019 among adult
Ugandans with a normal cervical CT scan at Nsambya hospital in Kampala. Eligible
participants were consecutively recruited into the study. Data on baseline characteristics and
pedicle dimensions from the CT scan findings were collected using a structured questionnaire
and analysed using Stata 13.0. Pedicle dimensions for the different levels of sub axial cervical
vertebrae were summarised as means and standard deviations, the Mann Whitney test was used
to compare pedicle dimensions for the different vertebrae level among females and males on
both right and left side and the level of significance was set at 0.05.
Results: A total of 700 sub axial cervical pedicles (C3-C7) from 49 males and 21 female
participants were studied. Pedicle width diameter showed cephalo-caudal gradual increment

2
from C3 [1.65(0.63) mm] to [3.46(0.75) mm] at C7. Pedicle height also showed an increase
caudally with smallest diameter at C3 [1.98(0.76) mm] and largest at C5 in females [3.67(6.42)
mm] and at C7in males [3.83(0.76) mm]. The pedicle height was wider than the pedicle width
at all levels. The pedicle chord length gradually increased caudally in both sexes ranging from
[29.08(1.35) mm] at C3 to [32.53(3.19) mm] at C7. The axial angles were oriented medially
and showed no consistent trend ranging between 50
0
and 53
0.
The sagittal angles decreased as
one moved from C3 to C7. The dimensions of females were significantly smaller than in males.
Conclusion: Pedicle endosteal width was smaller than pedicle height dimensions at all levels.
Pedicle cord length increased caudally. The pedicle dimensions except angulations, were
smaller in females than in males.
Key words: Cervical pedicle, Cervical pedicle screw, Pedicle Morphometric, Pedicle
dimensions, Cervical spine fixation, Computed Tomography.
Background
There are a number of well researched and documented sub-axial cervical spine fixation
methods for different pathologies. These include but not limited to pedicle screws, lateral mass
screws, inter-spinous wiring, laminar hooks and plating. Among these, pedicle screw fixation
has demonstrated the best biomechanical attribute like a high pull-out strength. Among the five
different human vertebrae types, (cervical, thoracic, lumbar, sacral and coccygeal), the cervical
spine is the smallest and exhibits the widest population variability in morphometry. This
predisposes visceral structures contained in the cervical spine namely the spinal cord, the nerve
roots and vertebral arteries to damages during any form of instrumentation surgery (1-5).
Therefore, a thorough understanding of the osteology of the sub-axial cervical spine is a
prerequisite for safe surgery in this region. Studies of cervical morphometric dimensions have
been done in different ethnic populations including Brazilians, Indians, Thais, Europeans,
Chinese-Singaporeans and Malaysians. Many indicated that there are inter racial differences in
the pedicle morphometric (6-10). To date no study has been conducted in Uganda to describe
the osteological characteristics of their cervical spine pedicle.
A clear definition of the morphometric characteristic of the sub-axial cervical spine improves
choice of implants for spine surgery for any procedure but also aids the spine surgeons in the
selection of appropriate pedicle screw sizes for the different demographic patient
characteristics. Therefore, the objective of this study was to describe the morphometric
dimensions of the sub axial cervical spine pedicles among adult Ugandans using computed
tomography (CT) scans.
Methods
We conducted a cross sectional study conducted at the Radiology department of Nsambya
Hospital from 1
st
March to 30
th
November 2019. Nsambya hospital is a 361 bed, Private Not
for Profit (PNFP) hospital located in Kampala city, Uganda. Its radiology department conducts
up to 3 cervical spine CT scans weekly.
The study was conducted among Ugandans aged 18 years and above with normal CT scans of
the cervical spine. These included images from patients who had presented to the radiology
department either for cervical spine solely or entire vertebral spine CT scan depending on the
indication. Cervical spine CT scans with evidence of fractures, dislocations, degenerative
changes, infection or Neoplasia were excluded from this study. Informed consent for
participation in the study was sought from participants whose images satisfied the selection
criteria. CT scans images were done using a SOMATOM Perspective 128 slice CT scan

3
machine (Siemens Healthineers, Germany). The CT scan machine had both helical and axial
scanning modes with volumetric capabilities reformatted images in sagittal and coronal planes
for the entire cervical spine. This machine was a 2013 model, installed in January 2014 and
was calibrated regularly.
Two consultant radiologists examined all included images. The demographic characteristics of
patients, whose images were included, were noted.
Using a pretested data extraction tool, the left and right Pedicle morphometric dimensions for
the sub axial spine for each participant were extracted from the reformatted images on the CT
workstation. Axial and sagittal cuts made along the optimal pedicle axis to get the sagittal
isthmus section using a software application on the CT scan workstation called Digital Imaging
and Communications in Medicine (DICOM) viewer software with a precision of 0.1 mm. The
pedicle dimensions data were measured and recorded on a data extraction form and then
entered into Microsoft excel database. Data was then exported to Stata version 13.0 for
analysing. The Pedicle dimensions for the different levels of cervical vertebrae were
summarised as means and standard deviations, the Mann Whitney test was used to compare
pedicle dimensions for the different vertebrae level among females and males on both the right
and left side and the level of significance was set at 0.05. We also did correlations (corr)
between BMI and the pedicle dimensions.
The following pedicle morphometric measurements were taken; Inner pedicle width: inner
medio-lateral diameter of the isthmus of the pedicle or width of cancellous core.
Inner pedicle height: inner super inferior diameter of the pedicle or the height of the cancellous
core of the isthmus of the pedicle.
Pedicle transverse angle: angle between the sagittal plane and the longitudinal pedicle axis
(LPA). Pedicle sagittal angle: angle between the inferior vertebral endplate and LPA. Chord
length (CL): Distance from the pedicle entry point to the anterior aspect of the vertebral body.
Measurements were carried twice for each dimension and the average recorded. .
Results
Description of study participants
A total of 70 participants were enrolled into the study, 49 (%) were males. The age of the
participants ranged from 19 to 76 years with a median age of 33.5years and the interquartile
range was 20. The median BMI of participants was 25.6. A total of 700 sub axial cervical
spine pedicles (C3-C7) were studied.
Axial pedicle dimensions
Pedicle width (PW)
The mean PW gradually increased from C3 to C7 as shown in Table 1. The overall PW ranged
from 1.65mm to 3.46mm (table1). The smallest mean PW was found at C3 in both females
(1.35mm) and males (1.77mm), while the largest mean PW was at C7in both females (3.10mm)
and males (3.66mm). The mean PW was smaller in females than in males at all levels (P<0.05).
Generally, there was no correction between PW and BMI, however there was a weak correction
of 0.18 at C3 and 0.15 at C7. The results are summarized in table 1 below.
Table 1 Showing pedicle width of 70 participants
PW(SD)
p value
Corr
p value
Corr
Right
Left
C3
Overall
1.65(0.63)
0.008
0.18
1.75(0.63)
0.005
-0.04
Male
1.77(0.60)
1.88(0.57)

4
Female
1.35(0.60)
1.44(0.66)
C4
Overall
1.82(0.77)
0.003
0.07
1.75(0.64)
0.042
0.14
Male
2.01(0.73)
1.84(0.62)
Female
1.37(0.70)
1.52(0.62)
C5
Overall
2.13(0.73)
0.013
0.06
2.06(0.66)
0.027
0.14
Male
2.27(0.73)
2.18(0.66)
Female
1.81(0.64)
1.78(0.59)
C6
Overall
2.47(0.82)
0.006
0.009
2.46(0.77)
0.11
0.04
Male
2.65(0.84)
2.56(0.78)
Female
2.05(0.59)
2.22(0.67)
C7
Overall
3.41(0.76)
0.021
0.15
3.46(0.75)
0.002
-0.08
Male
3.53(0.57)
3.66(0.62)
Female
3.10(1.05)
2.99(0.83)
PW=Pedicle width (SD), corr=correlation coefficient of pedicle parameter with BM
Pedicle chord length
The overall mean chord length ranged from 29.75mm to 31.99mm (Table 2). The smallest
mean chord length was found at C3 in both females(29.08mm) and males(30.03mm), while
the largest mean valve was found at C7 in both females(30.73mm) and males (32.53mm).
The mean chord length was smaller in females than in males at all levels (P<0.05). The chord
length increased as from C3 to C7. There was weak correlation between chord length and
BMI. The results are summarised in table 2 below.
Table 2. Table Showing cord length (cl) of 70 participants
CL
p value
Corr
p value
corr
Right
Left
C3
Overall
30.01(1.75)
0.003
0.28
29.75(1.64)
0.02
0.09
Male
30.41(1.74)
30.03(1.68)
Female
29.09(1.40)
29.08(1.35)
C4
Overall
30.15(1.48)
0.001
0.26
30.31(1.74)
0.002
0.08
Male
30.49(1.32)
30.74(1.55)
Female
29.35(1.58)
29.30(1.75)
C5
Overall
30.84(1.91)
0.002
0.2
30.79(1.92)
0.003
0.07
Male
31.39(1.74)
31.19(1.75)
Female
29.55(1.70)
29.86(2.02)
C6
Overall
31.85(1.89)
<0.001
0.08
31.89(1.95)
0.0002
0.07
Male
32.44(1.65)
32.40(1.86)
Female
30.46(1.70)
30.67(1.60)
C7

Frequently asked questions

Q1. What have the authors contributed in "Pedicle morphometry of sub axial cervical spine using computed tomography scans among adult ugandan population" ?

The objective of the study was to determine the morphometric dimensions of pedicles in the sub axial cervical spine among the adult Ugandan population. The authors conducted a cross sectional study from March to November 2019 among adult Ugandans with a normal cervical CT scan at Nsambya hospital in Kampala. Eligible participants were consecutively recruited into the study. Results: A total of 700 sub axial cervical pedicles ( C3-C7 ) from 49 males and 21 female participants were studied.