Spinous Process Inclination in Degenerative Lumbar Spinal Stenosis Individuals

Abstract

The aim of this study is to determine the sagittal inclination of lumbar spinous processes (SPs) in individuals with degenerative lumbar spinal stenosis (DLSS). It is a retrospective computerized tomography (CT) study including 345 individuals divided into two groups: control (90 males, 90 females) and stenosis (80 males and 85 females. The SP inclination was measured in the midsagittal plane from L1 to L5 levels. Stenosis males (L3-L5) and females (L1, L4) manifested significantly greater SP inclination compared to their counterparts in the control group. Males had significantly horizontal SP orientation compared to females (L1, L2). We also found that SP inclination became steeper as we descend caudally. This study indicates that SP inclinations are significantly associated with DLSS.

Full text

Research Article
Spinous Process Inclination in Degenerative Lumbar Spinal
Stenosis Individuals
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 28 September 2020; Revised 22 November 2020; Accepted 30 November 2020; Published 15 December 2020
Academic Editor: Parisa Azimi
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 is to determine the sagittal inclination of lumbar spinous processes (SPs) in individuals with degenerative
lumbar spinal stenosis (DLSS). It is a retrospective computerized tomography (CT) study including 345 individuals divided into
two groups: control (90 males, 90 females) and stenosis (80 males and 85 females. The SP inclination was measured in the
midsagittal plane from L1 to L5 levels. Stenosis males (L3-L5) and females (L1, L4) manifested significantly greater SP
inclination compared to their counterparts in the control group. Males had significantly horizontal SP orientation compared to
females (L1, L2). We also found that SP inclination became steeper as we descend caudally. This study indicates that SP
inclinations are significantly associated with DLSS.
1. Introduction
Lumbar spinous process (SP) morphometry has become an
interesting issue for application in spine surgery. Surgical
procedures associated with the SPs are supposed to be easy
and quick, with minimal blood loss and soft-tissue distur-
bance. Previous studies regarding SP morphometry have
focused essentially on age-related bony changes [1, 2], gender
discrepancy, and the differences between lumbar levels [3–5].
Others have investigated SP biomechanical properties [6, 7]
and their morphology regarding the spine devices and surgi-
cal techniques [8–10].
Degenerative lumbar spinal stenosis (DLSS) is a common
disorder in the elderly population related to degeneration of
the spine segment. Additionally, it may narrow the spinal
canal and the neural foramen leading to compression of the
neural elements [11, 12]. One of the surgical treatments pro-
posed to those with mild clinical presentation of DLSS is the
minimally invasive interspinous devices [13, 14]. Although
the insertion of these devices depends on the orientation
and size of lumbar SPs, few studies have addressed this issue.
We also believe that information regarding SP inclination
may improve the efficacy of interspinous process devices
and shed light on degenerative changes of the posterior
elements of the spine.
The aims of this study were (1) to determine the sagittal
inclination of lumbar SPs in individuals with DLSS compared
to the general population and (2) to establish whether SP
inclination is associated with age, gender, and lumbar levels.
2. Materials and Methods
2.1. Participants. This was a retrospective study including 165
individuals with DLSS-related symptoms who were enrolled
between 2008 and 2012. The age range was 40-88 years (sex
ratio: 80 M/85 F) with one or more levels with stenosis (cross
section area of dural sac <100 mm
2
) [15]. The diagnostic cri-
teria for DLSS were based on the combination of clinical
symptoms and signs together with the computerized tomog-
raphy (CT) findings [16]. The exclusion criteria were individ-
Hindawi
BioMed Research International
Volume 2020, Article ID 8875217, 5 pages
https://doi.org/10.1155/2020/8875217

uals under 40 years of age as well as those with congenital ste-
nosis (anterior posteriordiameter of the bony canal < 12 mm)
[17], fractures, spondylolysis, tumors, Paget’s disease, steroid
treatment, severe lumbar scoliosis (>20 degrees), and iatro-
genic conditions.
A control group (n= 180) without spinal stenosis-related
symptoms were referred at the same period to the Depart-
ment of Radiology, Carmel Medical Center, Haifa, Israel,
for abdominal CT scans due to abdominal problems. The
age range was 40-99 years (sex ratio: 90 M/90 F).
2.2. Computed Tomography (CT) Scans. A high-resolution
CT image (Brilliance 64, Philips Medical Systems; voltage:
120 kV; slice thickness: 0.9–3 mm; current: 150–570 mA)
was utilized which enabled scan processing in all planes. All
the CT images for both groups were taken in supine position
with extended knee. This research was approved by the ethi-
cal committee of the Carmel Medical Center (0083-07-
CMC).
2.3. Spinous Process Inclination (SPI). Spinous process incli-
nation was measured in the midsagittal plane and defined
as the angle between the longitudinal axis of the spinous pro-
cess and the posterior border of the same vertebral body
(Figure 1).
The cross-sectional area of the dural sac [18], lumbar lor-
dosis, and intervertebral disc height [19] were also evaluated
in the current study.
2.4. Statistical Analysis. The statistical analyses were calcu-
lated via SPSS version 20. Independent t-test analysis was
used for each gender separately to compare between the
study groups (stenosis and control) for age, BMI, and SP
inclination. One-way ANOVA and Pearson’s correlation
tests were performed to determine the association between
SP inclination and lumbar levels, lumbar lordosis, and disc
height, respectively. A logistic regression analysis via the
“Forward LR”method (separately for gender) was also used
to determine the association between SP inclination and
DLSS (dependent variable: DLSS; independent variable: SP
inclination, age, and BMI).
The intraclass correlation (ICC) coefficients were calcu-
lated to determine the intratester and intertester reliability
of the measurements taken (repeated measurements of 20
individuals). Intratester reliability of the measurements was
assessed by one of the authors (JA) who took the measure-
ments twice within intervals of 3-5 days. Intertester reliability
involved two testers (JA and KH), who took the measure-
ments within an hour of each other. Both testers were blinded
to the results of the measurements. Significant difference was
set at P<0:05.
3. Results
The intratester and intertester reliability results for all the
measurements were high: 0.984 to 0.933 and 0.942 to 0.890,
respectively.
3.1. SP Inclination in the Study Groups (Control vs. Stenosis).
The mean values of age and BMI in the study groups for each
gender separately are presented in Table 1.
In all participants, we found that SP inclination angles
were significantly greater in the stenosis males (L3-L5) and
females (L1-L5) compared to their counterparts in the con-
trol group (Table 1). It is noteworthy that this trend was
maintained when we did the comparison only for older sub-
jects (>60 year); however, significant differences in females
were observed only on the L1 level (Table 1). The outcomes
of the logistic regression analysis (adjusted for age and
BMI) revealed that more horizontal SP inclinations in males
(L3, L5) and females (L1, L4) are significantly associated with
DLSS (Table 2).
3.2. SP Inclination and Age, Gender, Lumbar Levels, Disc
Height, and Lumbar Lordosis. Analysis in the control group
(n= 180) revealed that males had significantly greater SP
inclination (more horizontal) than females at the L1
(82:1±5vs. 79:9±6,P=0:013) and L2 (81:9±6vs. 80 ± 5,
P=0:039) levels.
In general, SP inclinations for males (L1, L2) and females
(L3, L5) became more horizontal with increasing age
(Table 3). At nearly all lumbar levels, the inclination of SPs
was found to be more vertical/steep as we descend caudally;
however, the difference achieved significance only for the
male group: L2 and L3, L4 and L5 levels (P<0:05). In addi-
tion, SP inclination was neither correlated with lumbar lor-
dosis nor with adjacent disc height.
4. Discussion
Our results indicate that lumbar SP inclinations (adjusted for
BMI and age) for both males (L3, L5) and females (L1, L4) are
significantly associated with DLSS. We found that SP inclina-
tions in DLSS individuals were remarkably horizontally ori-
ented relative to the posterior vertebral border compared to
the control. Our results also showed that the differences in
SP inclination for each gender seem to be age-related varia-
tions. For example, the greater differences in SP inclination
for males were seen in subjects above 60 years, whereas those
for females were supposed to be in subjects between 40 and
60 years old. We believe that this result could support the
notion that gender dimorphism affects the prevalence and
severity of lumbar spine degeneration [20, 21].
Even though lumbar SP morphology information (e.g.,
height and width) has been used previously for interspinous
(a) (b)
Figure 1: (a) Measurement of spinous process inclination is shown.
(b) The location of the midsagittal section of the relevant vertebral
body is shown.
2 BioMed Research International

process devices, we have found no study in the literature that
has addressed the SP inclination in lumbar spinal stenosis
individuals. Therefore, others could not confirm our results.
DLSS is correlated with degenerative changes in the
three-joint complex and ligamentum flavum thickness [11,
22]. Moreover, the prevalence of this phenomenon increases
with age [12, 23]. Intermittent claudication is the main symp-
tom of DLSS that usually worsens in extension and walking
and improves in flexion or sitting [24, 25].
The lumbar spinous process is one of the posterior ele-
ments of the spine that protects the neural structures in the
dural canal and stabilizes the spine unit segment [26]. The
interspinous process decompression devices (e.g., XSTOP)
provide a minimally invasive technique for DLSS patients
with mild symptoms [27]. These devices reduce extension
at the symptomatic level(s), intrathecal pressure, and facet
load; stretch the ligamentum flavum; and enlarge the neural
foramens, thus improving spinal stenosis symptoms [10, 28,
29]. In 2012, Kim et al. have previously reported a strong
association between degenerative spondylolisthesis and SP
fractures in patients who underwent X-stop devices [9].
The authors believe that the placement of these devices
causes destabilization of lumbar segments affected by degen-
erative spondylolisthesis. One study has recently reported
that disc degeneration and fusion intervention correlate with
district kinematic alterations of interspinous processes at the
involved level [26]. Moreover, spinous process slope has a
direct bearing on the efficacy of interspinous process devices
to achieve indirect decompression of the canal and neurofor-
amina [5]. Accordingly, we assume that variations in SP
Table 1: Age, BMI, and SP inclination of the study groups (control vs. stenosis) for each gender separately by lumbar level.
Variables Males Pvalue Females Pvalue
Control (mean ± SD) Stenosis (mean ± SD) Control (mean ± SD) Stenosis (mean ± SD)
All subjects
Age (years) 62:8 ± 12 66:2±11 0.066 62 ± 12 62 ± 8 0.800
BMI (kg/m
2
)27:3±4 28:9±4 0.021 27:6±5 31:4±5 <0.001
SP L1 (degree) 82:1±5 81:9±5 0.811 79:9±6 83±4 <0.001
SP L2 (degree) 81:9±6 82:7±5 0.368 80 ± 5 82:4±5 0.006
SP L3 (degree) 78 ± 7 81:6±5 <0.001 77:4±6 80:7±6 0.001
SP L4 (degree) 76:2±7 80:1±6 0.001 76:4±7 80:9±6 <0.001
SP L5 (degree) 72:7±9 76:6±7 0.003 73:3±9 76:5±7 0.017
Subjects > 60 years
Age (years) 72:9±7 71:6±6 0.284 72:5±8 68:2±6 0.004
BMI (kg/m
2
)27 ± 4 29:4±5 0.003 26:1±4 31:6±5 <0.001
SP L1 (degree) 82:8±5 82:5±6 0.771 80:3±5 82:7±5 0.034
SP L2 (degree) 82:8±5 83:1±5 0.737 81:1±5 82:1±5 0.429
SP L3 (degree) 79:3±7 82:1±5 0.027 77:9±6 80:5±6 0.052
SP L4 (degree) 76:6±7 81±6 0.003 77:2±7 79:7±6 0.072
SP L5 (degree) 72:18 ± 8 76:5±7 0.009 75:9±8 75:8±8 0.957
SP: spinous process; SD: standard deviation.
Table 2: Variables significantly associated with degenerative
lumbar spinal stenosis (males and females listed separately).
OR CI 95% Pvalue
Males
BMI 1.097 1.018-1.183 0.015
Spinous process L3 1.087 1.030-1.146 0.002
Spinous process L5 1.061 1.018-1.106 0.005
Females
BMI 1.159 1.082-1.242 <0.001
Spinous process L1 1.078 1.011-1.150 0.022
Spinous process L4 1.107 1.048-1.168 <0.001
OR: odds ratios; CI: confidence intervals: BMI: body mass index.
Table 3: Pearson correlation values between SP inclination and age
for each gender separately, by lumbar level.
Variable Pearson’s correlation Pvalue
Males
Spinous process L1 (degree) 0.211 0.046
Spinous process L2 (degree) 0.187 0.078
Spinous process L3 (degree) 0.213 0.044
Spinous process L4 (degree) 0.123 0.247
Spinous process L5 (degree) 0.015 0.885
Females
Spinous process L1 (degree) 0.157 0.140
Spinous process L2 (degree) 0.226 0.032
Spinous process L3 (degree) 0.123 0.247
Spinous process L4 (degree) 0.171 0.106
Spinous process L5 (degree) 0.291 0.005
3BioMed Research International

inclination such as horizontal orientation could harm the
spine stability due to alterations on the axial loading between
the anterior and posterior column.
Our finding in the control group showed that the lumbar
SP inclination angle became smaller from L1 to L5. This
result is supported by a previous study in which measure-
ments were based on dry skeletal cadavers (2955 human lum-
bar vertebrae) and found that SP slope became steeper as we
descend caudally [5]. We also believe that this result partially
supports the notion that the maximal slope of the L5 SP in
the general population makes the surgery at the L4 and L5
levels less effective compared to horizontal SPs (L1 through
L4) [5].
Similar to the latter study, we also demonstrate signifi-
cant correlations (on some levels) between SP inclination
and age. Although the correlation values are weak (range:
0.221-0.291, P<0:05), it seems that SP inclination became
more horizontal in advanced age. We believe that this associ-
ation could in part be from age-related changes in SP mor-
phology the same as for height and width [1, 2, 30]. With
regard to gender, females manifest smaller SP inclination
angle at the L1 and L2 levels. Indeed, this trend was noted
previously, when Shaw et al. reported that female specimens
had generally steeper SP slope than males [5].
It is noteworthy that our SP measurements have some
superiority, as the posterior vertebral border (axis reference)
is not prone to any age-related changes such as osteoporotic
changes of the vertebral body or degenerative changes of the
upper end plates that could influence the orientation of the
SP, relative to the upper end plate.
Finally, although it is unclear whether the variation of SP
inclination in subjects with DLSS is a primary manifestation
or secondary process due to aging, we assume that this
unique characteristic has a role in the pathogenesis of DLSS.
However, the mechanism of SP orientation resulting in DLSS
has not been elucidated in detail.
4.1. Clinical Implication. As males (L3, L5) and females (L1,
L5) with DLSS are candidates for horizontally oriented lum-
bar SPs, this implies that the efficacy of interspinous devices
could be greater at these levels; in addition, spinal/epidural
injections could be easier to perform compared with other
levels. We also believe that surgeons should take into consid-
eration the fact that SP orientation could be different in sub-
jects with herniated nucleus pulposis, disc disease, lumbar
instability, and spinal stenosis when using different interspi-
nous devices [27, 31, 32].
4.2. Limitation of the Study. This is a retrospective study, and
the outcomes should be supported by well-established pro-
spective studies with large numbers of participants with DLSS.
In addition, SP measurements for height, thickness, and width
are needed to shed light on the development of DLSS.
5. Conclusion
Our results indicate that SP inclinations for both males (L3,
L5) and females (L1, L4) are significantly associated with
DLSS. Additionally, SP inclinations (on some levels) are
dependent for age, gender, and lumbar level.
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 Mrs. Margie Serling Cohn and Mr. Chaim Cohen
for their editorial assistance.
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