Pedicle Morphometry Variations in Individuals with Degenerative Lumbar Spinal Stenosis

Abstract

The aim of this study was to compare pedicle dimensions in degenerative lumbar spinal stenosis (DLSS) with those in the general population. A retrospective computerized tomography (CT) study for lumbar vertebrae (L1 to L5) from two sample populations was used. The first included 165 participants with symptomatic DLSS (age range: 40-88 years, sex ratio: 80 M/85 F), and the second had 180 individuals from the general population (age range: 40-99 years, sex ratio: 90 M/90 F). Both males and females in the stenosis group manifested significantly greater pedicle width than the control group at all lumbar levels (P < 0:05). In addition, pedicle heights for stenosis females were remarkably smaller on L4 and L5 levels compared to their counterparts in the control group (P < 0:001). Males have larger pedicles than females for all lumbar levels (P < 0:001). Age and BMI did not demonstrate significant association with pedicle dimensions. Our outcomes indicate that individuals with DLSS have larger pedicle widths than the control group. More so, pedicle dimensions are gender-dependent but independent of age and BMI.

Full text

Research Article
Pedicle Morphometry Variations in Individuals with Degenerative
Lumbar Spinal Stenosis
Janan Abbas ,
1,2
Natan Peled,
3
Israel Hershkovitz,
1
and Kamal Hamoud
2,4,5
1
Department of Anatomy and Anthropology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel
2
Department of Physical Therapy, Zefat Academic College, Zefat 13206, Israel
3
Department of Radiology, Carmel Medical Center, Haifa 3436212, Israel
4
Azrieli Faculty of Medicine, Bar-Ilan University, Safed 1311502, Israel
5
Department of Orthopaedic Surgery, The Baruch Padeh Poriya Medical Center, Tiberias 1520800, Israel
Correspondence should be addressed to Janan Abbas; janan1705@gmail.com
Received 17 November 2019; Accepted 20 January 2020; Published 24 February 2020
Academic Editor: Alberto Grassi
Copyright © 2020 Janan Abbas et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
The aim of this study was to compare pedicle dimensions in degenerative lumbar spinal stenosis (DLSS) with those in the general
population. A retrospective computerized tomography (CT) study for lumbar vertebrae (L1 to L5) from two sample populations
was used. The first included 165 participants with symptomatic DLSS (age range: 40-88 years, sex ratio: 80 M/85 F), and the
second had 180 individuals from the general population (age range: 40-99 years, sex ratio: 90 M/90 F). Both males and females
in the stenosis group manifested significantly greater pedicle width than the control group at all lumbar levels (P<0:05). In
addition, pedicle heights for stenosis females were remarkably smaller on L4 and L5 levels compared to their counterparts in the
control group (P<0:001). Males have larger pedicles than females for all lumbar levels (P<0:001). Age and BMI did not
demonstrate significant association with pedicle dimensions. Our outcomes indicate that individuals with DLSS have larger
pedicle widths than the control group. More so, pedicle dimensions are gender-dependent but independent of age and BMI.
1. Introduction
Degenerative lumbar spinal stenosis (DLSS) is a common
condition in the elderly population that is related to degen-
eration of the three-joint complex and ligaments [1, 2].
Symptomatic DLSS requires the combination of clinical pre-
sentation with radiological findings such as computerized
tomography (CT) scan and magnetic resonance imaging
(MRI) modalities [3, 4]. Typically, neurogenic claudication
and radicular pain are the best described clinical pictures [3].
The surgical treatment of symptomatic DLSS often
requires the use of instrumentation systems. The transpedi-
cular screw fixation is stable and worthwhile as it provides
three-dimensional fixation and is increasingly used world-
wide [5, 6]. It has been found that the pedicle bone is the
strongest part of the vertebra, even in an osteoporotic one
[7, 8]. Information regarding pedicle morphometry is essen-
tial for using the pedicle screws.
Many previous studies concerning pedicle morphometry
have been conducted in subjects of various ethnic origins
and populations (e.g., Western and Asian) in order to estab-
lish normal range parameters [5, 9–19]. All of these studies
based their measurements on various approaches such as
direct cadavers [5, 9, 11, 12, 16, 19], radiologic techniques
[10, 15, 17, 18], and combined cadavers and radiologic
methods [13, 14]. It has been stated that CT measurement
is the best means of evaluating pedicle radiographic mor-
phology [18, 20, 21]. Likewise, others have shown that data
obtained from a CT scan for pedicle parameters are almost
identical to those obtained from direct cadaveric measure-
ments [7, 13, 22].
Because a previous study has found that lumbar vertebral
bodies for DLSS individuals are significantly greater com-
pared to those found in the general population [23], we
hypothesized that the pedicle morphology for the DLSS pop-
ulation will be varied.
Hindawi
BioMed Research International
Volume 2020, Article ID 7125914, 6 pages
https://doi.org/10.1155/2020/7125914

The aim of this study was to assess the pedicle parameters
for the DLSS population and to compare these parameters
with those for the general population.
2. Materials and Methods
2.1. Study Design. This is a cross-sectional retrospective
study with two groups of individuals [24]. The first group
(control) included 180 individuals without spinal stenosis-
related symptoms (age range: 40-99 years, sex ratio: 90
M/90 F) who were referred to the Department of Radiology,
Carmel Medical Center, Haifa, Israel, for abdominal CT
scans due to abdominal problems. The second group
included 165 patients with symptomatic DLSS (age range:
40-88 years, sex ratio: 80 M/85 F), who had intermittent
claudication accompanied by other symptoms related to spi-
nal stenosis [25]. Their CT scan images showed a reduced
cross-sectional area (CSA) of the dural sac (<100 mm
2
)
[26] of at least one lumbar level. The diagnostic criteria for
DLSS were based on the combination of symptoms and signs
together with the imaging findings [3]. Individuals under 40
years of age as well as those with congenital stenosis
(AP diameter of the bony canal < 12 mm) [27], fractures,
spondylolysis, tumors, Paget’s disease, steroid treatment,
severe lumbar scoliosis (>20 degrees), and iatrogenic con-
ditions (postlaminectomy, postfusion) were excluded from
the study.
A high-resolution CT image (Brilliance 64, Philips Med-
ical Systems; voltage 120 kV, current 150–570 mA) was uti-
lized which enabled scan processing in all planes. All CT
images for both groups were taken in the same position.
This research was approved by the ethical committee of
the Carmel Medical Center (0083-07-CMC).
2.2. Pedicle Dimensions
2.2.1. Pedicle Width (PW)/Transverse Pedicle Parameter. This
parameter was measured in the axial plane at the middle of
the pedicular height and defined as the distance between its
medial and lateral cortices (Figure 1). The measurements
were done on both sides (left and right), and the mean values
were then calculated.
2.2.2. Pedicle Height (PH). This parameter was measured in
the sagittal plane at the middle of the pedicle width and
was defined as the distance between its superior and inferior
cortices (Figure 2). The measurements were taken on both
sides (left and right), and the averages were then calculated.
In order to identify the association between pedicle diam-
eters and age, we classified the control group into two age
groups: (a) the middle group included individuals between
40 and 60 years and (b) the older group included individuals
who were 60 years and older.
2.3. Statistical Analysis. The sample size of this study was
based on power analysis (α=0:05,β=0:8), and all the para-
metric variables (e.g., pedicle width and height) were checked
for normal distribution. Statistical analysis was done via SPSS
version 20. The Student t-test was used for each gender sep-
arately to compare the studied groups (control vs. stenosis)
for all the parametric variables and to examine the associa-
tion between pedicle diameters and age. Pearson correlation
and one-way ANOVA were also used to determine the asso-
ciation between pedicle parameters and BMI and lumbar
levels. A logistic regression analysis via the “Forward LR”
method was used (separated by gender) to define the associ-
ation between DLSS and pedicle parameters (dependent var-
iable: DLSS; independent variables: pedicle width, pedicle
height, age, and BMI). The intraclass correlation (ICC) coef-
ficients were calculated to determine the intratester and
intertester reliability of the measurement taken (repeated
measurements of 20 individuals). Intratester reliability of
the measurements was assessed by one of the authors (JA)
who took the measurements twice within intervals of 3-5
days. Intertester reliability involved two testers (JA and
KH) who took the measurements within an hour of each
other. Both testers were blinded to the results of the measure-
ments. Significant difference was set at P<0:05.
3. Results
The intra- and interclass correlations for pedicle parameters
ranged from 0.867 to 0.976 and from 0.751 to 0.943,
respectively.
No significant differences were found in the mean age of
the control males and females compared to their counter-
parts in the stenosis group (Table 1). However, BMI values
were significantly greater in the stenosis groups compared
to their counterparts in the control group.
3.1. Pedicle Parameters in the Study Groups. The mean PWs
in both males and females in the stenosis group were signifi-
cantly greater compared to those in their counterparts in the
control group (Table 1). Furthermore, mean PHs for stenosis
females were considerably smaller on L4 and L5 levels com-
pared to those for their counterparts in the control group.
Our results indicate that L5 PW in both genders and L1
PW, L4 PH, and L5 PH for females are significantly associ-
ated with DLSS (Table 2).
Of the 180 individuals in the control group, 41 subjects
(22.7%) had PW less than 5 mm on the upper lumbar spine
(L1 and L2), compared to only 12 subjects (11.8%) in the
stenosis group (Table 3). In addition, 50% to 94% of the
control group had PW less than 6 and 7 mm, respectively,
on the upper lumbar region, compared to 27.3% to 60.7%
in the stenosis group.
Figure 1: Measurement of pedicle width as conducted on an axial
CT scan (a) at the middle height of the pedicle (b).
2 BioMed Research International

3.2. The Association between Pedicle Parameters and Gender,
Age, BMI, and Lumbar Levels. Analysis of the control
group (n= 180) revealed that males have larger values of
PW and PH than females along all the lumbar levels
(P<0:001). Generally, PWs and PHs were not associated
with age and BMI (P>0:05).
A significant increase in PWs was noted as we descend
caudally (P<0:001), except between L1 and L2 (P=0:810):
L1 = 7 mm ± 1:7,L2 = 7:3mm±1:6,L3 = 8:8mm±1:8,L4
=10:7mm±1:9, and L5 = 15:2mm±2:2. In contrast, lum-
bar PH values significantly decrease caudally (P<0:001) with
the exception of L2 and L3 (P=0:743): L1 = 14:9mm±1:4,
L2 = 14:1mm±1:3,L3 = 14 mm ± 1:2,L4 = 13 mm ± 1:2,
and L5 = 11:7mm±1:2.
4. Discussion
The most important finding of the present study is that indi-
viduals with DLSS manifest larger pedicle width compared
Figure 2: Measurement of pedicle height as conducted on a sagittal CT scan (a) at the middle of pedicle width (b).
Table 1: Age, BMI, PW, and PH values of the study groups (control vs. stenosis) for each gender separately.
Variables Males Females
Control (mean ± SD) Stenosis (mean ± SD)Pvalue Control (mean ± SD) Stenosis (mean ± SD)Pvalue
Age (years) 62:9±12:38 66:2±10:82 0.066 62 ± 12:97 62:5±8:63 0.795
BMI (kg/m
2
)27:4±4:21 28:9±4:55 0.021 27:61 ± 5:13 31:48 ± 5:83 <0.001
L1 PW (mm) 7:7±1:28:5±2 0.005 6:3±1:77±1:30.007
L2 PW (mm) 8:1±1:38:9±1:70.001 6:4±1:57:3±1:3<0.001
L3 PW (mm) 9:7±1:610:7±1:8<0.001 8±1:59:1±1:5<0.001
L4 PW (mm) 11:5±1:712:6±1:6<0.001 9:8±1:710:8±1:4<0.001
L5 PW (mm) 16 ± 2 17:6±2:3<0.001 14:5±2 16±1:9<0.001
L1 PH (mm) 15:6±1:215:7±1:80.938 14:2±1:213:9±1:20.088
L2 PH (mm) 14:8±1:115:1±1:80.238 13:6±1:113:4±1:10.378
L3 PH (mm) 14:5±1:214:7±1:60.338 13:5±1 13:2±1:20.108
L4 PH (mm) 13:5±1:113:4±1:70.645 12:5±1:111:8±1:2<0.001
L5 PH (mm) 12:2±1:312±1:70.564 11:3±1 10:5±1:1<0.001
SD: standard deviation; BMI: body mass index; PW: pedicle width; PH: pedicle height.
Table 2: A logistic regression analysis demonstrating the variables
that are significantly associated with degenerative lumbar stenosis
(males and females listed separately).
OR 95% CI Pvalue
Males
Age 1.032 1.003-1.063 0.029
BMI 1.079 1.000-1.165 0.050
L5 PW 1.361 1.171-1.581 <0.001
Females
BMI 1.1 1.026-1.180 0.007
L1 PW 1.444 1.108-1.883 0.007
L5 PW 1.457 1.171-1.814 0.001
L4 PH 0.593 0.391-0.899 0.014
L5 PH 0.663 0.441-0.998 0.049
OR: odds ratios: CI: confidence intervals; BMI: body mass index; PW: pedicle
width; PH: pedicle height.
Table 3: Percentage of pedicle width less than 5, 6, and 7 mm in the
studied groups at the lumbar level.
Levels Control group (n= 180) Stenosis group (n= 165)
<5mm <6mm <7mm <5mm <6mm <7mm
L1 13.3 28.3 49.4 4.8 16.4 35.2
L2 9.4 22.2 43.9 2.4 10.9 25.5
L3 1.7 3.9 15.6 0 1.2 3.6
L4 0 0 2.2 0 0 0
L5 000000
3BioMed Research International

to the general population. This result is not surprising, as we
initially assumed, because lumbar vertebral body size was
greater in individuals with DLSS relative to the general
population. Similarly, others have reported a significant
correlation between vertebral body size and pedicle dimen-
sions [28, 29].
It is noteworthy that pedicle parameters in the stenosis
and control groups were consistently similar to the trend
observed in previous studies [5, 15, 17, 30]: PW values
increase caudally whereas PHs decrease from L1 to L5.
Pedicle morphometry is essential for developing and
designing pedicle instrumentations since it has become a
common tool for the spine surgeons. Likewise, the use of a
transpedicular screw is also widespread for the DLSS popula-
tion when segmental instability exists [31]. There is a consen-
sus that PW is the most important parameter in relation to
screw size fixation due to its smaller size compared with PH
[7, 20, 22]. One of the main factors regarding the rigidity of
the fixation system is the pullout strength of the transpedicular
screw [32]. It has also been reported that an increase of 1 mm
of the screw diameter improves the pullout strength [14, 33];
thus, a wider screw results in better fixation. The outer screw
diameter should match precisely the internal transverse diam-
eter of the pedicle without exceeding its external borders [19].
The outer diameters of the most commonly used pedicle
screws range from 5 to 7mm [20, 34]. The result regarding
PWs in the control group showed that 22.7% of this group
had PW of less than 5 in the upper lumbar spine (L1 and
L2) which was quite similar to results obtained from the stud-
ies of Scoles et al. [16] and Ofiram et al. [35]. In comparison,
only 0 to 2.2% of the subjects have PW less than 6 and 7mm
on the lower lumbar region (L4, L5), respectively. These find-
ings imply that (1) utilizing a screw diameter of 6 mm in the
upper lumbar spine for the general population should be
avoided and (2) a screw diameter of 7mm could be acceptable
in the lower lumbar region. We believe that these findings are
not surprising as they are in accordance with other studies [12,
15–17]. Weinstein and colleagues have also indirectly sup-
ported this idea when they reported a 40% failure rate when
attempting insertion of a screw diameter of 7 mm in the upper
lumbar spine [36]. Our result also showed that the percentage
of PW less than 5 and 6mm on the upper lumbar spine for the
control group is almost 3 times greater than that for the steno-
sis group (22.7% vs. 7.2% and 50.5% vs. 27.3%, respectively).
This indicates that for DLSS individuals, compared to the gen-
eral population, screws with a larger diameter could be utilized
for the entire lumbar spine.
We also postulate that subjects with spine disorder might
display variant pedicle morphometry. This proposal can be
partially supported by Cheung and colleagues as they reported
that individuals with low back pain might manifest different
pedicle morphometry than the general population [10].
Comparing our outcomes of pedicle parameters (control
group) with previous radiologic studies (Table 4) revealed
that PWs were, in general, similar to those obtained from
the Asian population [5, 15, 17, 37] but smaller than those
of Western studies [13, 20, 22, 38]. This result could empha-
size the effect of differing populations on the wide disparity in
the reported results [12, 15, 17]. In addition, PHs were
greater than PWs and decreased caudally. The lowest value
Table 4: Pedicle diameters in the current study compared with only radiologic studies.
Study Mean diameters (mm) L1 L2 L3 L4 L5
Current study (n= 180)PW 7 7.3 8.8 10.7 15.2
PH 14.9 14.1 14 13 11.7
Mohanty et al., 2018 (n= 102-124) PW 7.2 7.6 8.4 10.1 13
Acharya et al., 2010 (n=50) PW 7.20 7.62 8.97 11.12 13.91
Chadha et al., 2003 (n=14-20) PW 6.69 7.26 8.43 10.81 13.47
Kadioglu et al., 2003 (n=29)PW 8.8 9.7 10.3 10.8 14.6
PH 14.7 14.5 13.6 13.6 13.4
Mitra et al., 2002 (n=20)PW 7.34 7.45 8.51 9.71 14.49
PH 16.42 15.65 15.24 15.29 15.17
Cheung et al., 1994 (n=35-134) PW 5.3 6.7 9.5 11.5 14.7
Bernard and Seibert, 1992 (n= 154) PW ND 8.13 8.7 10.88 14.54
Olsewski et al., 1990 (n=37-42) PW 8.2 8.3 10 12.6 16.6
PH 18.2 17.2 16.9 15.6 13.8
Marchesi et al., 1988 (n=28-46) PW 7.1 7.8 9.7 13 18
PH 15.4 14.8 14.2 13.9 13.7
Zindrick et al., 1987 (n=26-56) PW 8.7 8.9 10.3 12.9 18
PH 15.4 15 14.9 14.8 14
Krag et al., 1986 (n=14-24) PW 7.01 8.67 9.30 11.03 15.15
ND: no data; PW: pedicle width; PH: pedicle height.
4 BioMed Research International

measured for PH was 8.35 mm, and the greatest value was
19.3 mm. This outcome is mostly consistent with the studie s
of Marchesi et al. [13] and Kadioglu et al. [39], with the
exception of L5.
The current study also found that males had signifi-
cantly larger pedicle diameters than females along all the
lumbar levels. This result confirms what is commonly
reported [5, 9, 19, 35, 38, 40] but contradicts others [10,
11]. Similar to the studies of Yu et al. [9] and Cheung
et al. [10], the current study did not demonstrate any sig-
nificant relationship between age and pedicle diameters.
With respect to BMI, we also failed to confirm significant
correlations with pedicle parameters. This result is in
agreement with Ofiran et al. [35], but not with Yu et al.
[9]. We assume that our finding contrasts the results of
Yu and colleagues due to the differing studied populations
and methods of measurements: CT images for the living
population vs. direct measurement for dry specimens. It
is well known that the CT scan is the gold standard for
pedicle measurements [35]. Likewise, some authors found
similar results for pedicle parameter values when they
based their methods on both the direct measurement and
CT technique [20, 22]. We believe that studies conducted
on living populations are preferable to those based on
cadaver specimens, because preoperative CT scans are usu-
ally used to determine the precise screw dimensions.
4.1. Limitation of the Study. Although this study has the larg-
est series that was conducted on CT scans, a large-scale pop-
ulation with DLSS is needed to confirm the association
between this phenomenon and pedicle diameters. Pedicle
length and transverse pedicle angle are required to better
define the screw dimensions and to avoid nerve root injury
and inadvertent penetration of the screw in the spinal canal.
More so, some studies have reported that the transverse ped-
icle angle could be smaller in subjects with degenerative spi-
nal diseases that may be attributable to developmental
changes [41, 42].
5. Conclusions
The current study revealed that symptomatic subjects with
DLSS manifest different pedicle diameters than the general
population. When planning instrumentation for DLSS indi-
viduals, the pedicles will be able to accept larger screws than
those of the general population. Furthermore, pedicle diame-
ters are gender-dependent and independent of age and BMI.
Data Availability
The data used to support the findings of this study are avail-
able from the corresponding author upon request.
Conflicts of Interest
The authors declare that they have no conflicts of interest.
Acknowledgments
The authors would like to thank the Dan David Foundation,
the Israel Science Foundation (Grant number 1397/08), and
the Tassia and Dr. Joseph Meychan Chair for the History
and Philosophy of Medicine for funding this research. We
also thank Margie Serling Cohn and Chaim Cohen for their
editorial assistance.
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