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A morphological adaptation? The prevalence of enlarged external occipital protuberance in young adults

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Enthesophytes are bony projections that arise from the sites of ligament, tendon or joint capsule attachment to a bone. They are seen rarely in radiographic findings in young adults, as these bony adaptations are assumed to develop slowly over time. However, in recent years, the presence of an enlarged external occipital protuberance (EEOP) has been observed frequently in radiographs of relatively young patients at the clinic of the lead author. Accordingly, the aim of this project was to assess the prevalence of an EEOP in a young adult population. Analysis involved a retrospective analysis of 218 lateral cervical radiographic studies of 18–30-year-old participants. Group A (n = 108; males = 45, females = 63) consisted of asymptomatic university students, while Group B (n = 110; males = 50, females = 60) were an age-matched mildly symptomatic, non-student population. The external occipital protuberance (EOP) size was defined as the distance from the most superior point of the EOP (origin) to a point on the EOP that is most distal from the skull. To avoid ambiguity, the threshold for recording the size of an EOP was set at 5 mm, and an EOP was classified as enlarged if it exceeded 10 mm. Reliability testing was also undertaken. Results indicated that an EEOP was present in 41% of the total population, with 10% of all participants presenting with an EOP ≥ 20 mm. An EEOP was significantly more common in males (67.4%) than in females (20.3%), with the mean EEOP size for the combined male population (15 ± 7 mm) being significantly larger (P < 0.001) than for females (10 ± 4 mm). The longest EEOP in the male population was 35.7 mm, while in the female population it was 25.5 mm. Additionally, the mean EEOP size for Group A (14 ± 7 mm) was also significantly greater (P = 0.006) than that recorded for Group B (12 ± 6 mm). This study identified that an EEOP is a condition that is prevalent in the populations tested. The age of the populations, and the prevalence of EEOP, suggest that biomechanical drivers for this phenomenon may be the main reason for this condition in these populations.
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A morphological adaptation? The prevalence of
enlarged external occipital protuberance in young
adults
David Shahar and Mark G. L. Sayers
School of Health and Sport Sciences, University of the Sunshine Coast, Sunshine Coast, QLD, Australia
Abstract
Enthesophytes are bony projections that arise from the sites of ligament, tendon or joint capsule attachment to
a bone. They are seen rarely in radiographic findings in young adults, as these bony adaptations are assumed
to develop slowly over time. However, in recent years, the presence of an enlarged external occipital
protuberance (EEOP) has been observed frequently in radiographs of relatively young patients at the clinic of
the lead author. Accordingly, the aim of this project was to assess the prevalence of an EEOP in a young adult
population. Analysis involved a retrospective analysis of 218 lateral cervical radiographic studies of 1830-year-
old participants. Group A (n=108; males =45, females =63) consisted of asymptomatic university students,
while Group B (n=110; males =50, females =60) were an age-matched mildly symptomatic, non-student
population. The external occipital protuberance (EOP) size was defined as the distance from the most superior
point of the EOP (origin) to a point on the EOP that is most distal from the skull. To avoid ambiguity, the
threshold for recording the size of an EOP was set at 5 mm, and an EOP was classified as enlarged if it
exceeded 10 mm. Reliability testing was also undertaken. Results indicated that an EEOP was present in 41% of
the total population, with 10% of all participants presenting with an EOP 20 mm. An EEOP was significantly
more common in males (67.4%) than in females (20.3%), with the mean EEOP size for the combined male
population (15 7 mm) being significantly larger (P<0.001) than for females (10 4 mm). The longest EEOP
in the male population was 35.7 mm, while in the female population it was 25.5 mm. Additionally, the mean
EEOP size for Group A (14 7 mm) was also significantly greater (P=0.006) than that recorded for Group B
(12 6 mm). This study identified that an EEOP is a condition that is prevalent in the populations tested. The
age of the populations, and the prevalence of EEOP, suggest that biomechanical drivers for this phenomenon
may be the main reason for this condition in these populations.
Key words: enthesis; external occipital protuberance; spondyloarthropathy.
Introduction
Entheses are the sites of ligament, tendon or joint capsule
attachment to a bone (Claudepierre & Voisin, 2005; D’Agos-
tino & Olivieri, 2006; Jacques et al. 2014). A key role of the
enthesis is to distribute force over a large area of the bone
surface (Benjamin et al. 2000; McGonagle et al. 2001;
Claudepierre & Voisin, 2005). Therefore, a substantial
amount of mechanical stress can be absorbed by the inter-
weaving fibres at the insertion (Benjamin & Ralphs, 1998).
The formation of enthesophytes, bony projections that arise
from the enthesis, is multifactorial, and can be attributed to
biomechanical, immunological and/or genetic factors (Shai-
bani et al. 1993; McGonagle et al. 1998, 2001; Benjamin
et al. 2000; Claudepierre & Voisin, 2005; Slobodin et al.
2007; Hardcastle et al. 2014; Jacques et al. 2014). While the
hallmarks of spondyloarthritis (SpA), enthesitis and entheso-
phyte formation (Benjamin & McGonagle, 2001; Jacques
et al. 2014) may be ascribed to functional adaptation aris-
ing from tensile or compressive mechanical stresses on the
enthesis (Benjamin et al. 2000; D’Agostino & Olivieri, 2006;
Jacques et al. 2014; McGonagle et al. 2014), a large propor-
tion of research focuses on non-mechanical aetiologies.
Recently, leading researchers on the subject have acknowl-
edged that for better understanding and treatment of SpA,
it is vital that future research on the subject focuses on
mechanical stress on the enthesis (Jacques et al. 2014;
McGonagle et al. 2014).
Correspondence
David Shahar, School of Health and Sport Sciences, University of the
Sunshine Coast, Maroochydore DC, Sunshine Coast 4558 QL,
Australia; E: david.shahar@research.usc.edu.au
Accepted for publication 16 February 2016
Article published online 22 March 2016
©2016 Anatomical Society
J. Anat. (2016) 229, pp286--291 doi: 10.1111/joa.12466
Journal of Anatomy
Enthesophytes are seen rarely in radiographic findings in
young adults as they are assumed to develop slowly over
time (Boden et al. 1990a; Matsumoto et al. 2010). In con-
trast, enthesophytes are observed commonly on radio-
graphic studies of the aging asymptomatic population
(Boden et al. 1990a,b; Shaibani et al. 1993; Malcolm, 2002;
Claudepierre & Voisin, 2005; Matsumoto et al. 2010, 2013).
Enthesophytes can present on both the axial and appendic-
ular skeleton (McGonagle et al. 2001; Jacques et al. 2014).
Symptoms at the entheses are more frequent at the lower
extremities, and enthesitis is found most frequently at the
heel (Paolaggi et al. 1984; Lehtinen et al. 1994; Olivieri
et al. 1998; D’Agostino & Olivieri, 2006). This reason alone
may account for the extensive research dedicated to the
enthesis of the lower extremities, leaving enthesopathy in
sites such as the external occipital protuberance (EOP) lar-
gely unexplored. Although not always painful, in some
cases enthesitis can be both debilitating and enduring, tak-
ing several years to diminish (D’Agostino & Olivieri, 2006).
While the relationship between anatomical findings and
symptoms may be coincidental (Jensen, 1994), symptoms
associated with the area of muscular insertion to the EOP
have been documented (D’Agostino & Olivieri, 2006; Mar-
shall et al. 2015). For example, pain at the occipital region is
a common complaint by headache sufferers, and differen-
tial diagnosis to this condition may include cervicogenic
headache, migraine or other primary headache disorders
(Dougherty, 2014).
In recent years, the presence of an enlarged external
occipital protuberance (EEOP) has been observed frequently
in radiographs of relatively young patients at the clinic of
the lead author (Fig. 1). To the best of the authors’ knowl-
edge, reports concerning enthesophytes projecting out of
the EOP are rare in the medical literature (Singh, 2012; Mar-
shall et al. 2015), although a few reports do exist in the
anthropological and forensic science literature (G
ulekon &
Turgut, 2003; Marshall et al. 2015). Accordingly, the aim of
this study was to: (i) quantify the prevalence of EEOP within
apparently healthy, asymptomatic, young adult partici-
pants; and (ii) compare these data with a cohort of mildly
symptomatic age-matched individuals.
Materials and methods
This project was provided full ethics approval from the institutional
Human Research Ethics Committee. A retrospective radiographic
analysis of 218 lateral cervical radiographic studies of 1830-year-
old participants was carried out by an experienced observer to iden-
tify the prevalence of an EEOP in young adult participants. Group A
consisted of 108 asymptomatic university students (males =45,
females =63) who had volunteered to participate in an unrelated
research project, and were radiographed by a researcher not
involved with this study. The other sample of 110 lateral cervical
radiographs (Group B; males =50, females =60) was collected over
the same 18-month period at a single chiropractic clinic by trained
radiographers. The population in Group B was mildly symptomatic
and reported no specific complaints concerning the EOP. The speci-
fic symptoms recorded for Group B were extracted directly from the
initial-patient-intake-form that was completed by each patient
upon commencing care. Patients that recorded symptomatic com-
plaints greater than mild were excluded from this analysis. The data
from Group A (university students) were compared with Group B
(an age-matched non-university student, clinical population) to
determine whether findings were exclusive to this group or com-
mon acros s both pop ulatio ns teste d. All rad iograp hs, for both
groups, were obtained at the same facility and by the same digital-
capturing equipment. The same capturing techniques were used to
collect the radiographs for both groups, with participants instructed
to stand in their normal posture looking straight ahead, with their
right shoulder in contact with the wall mounted ‘Bucky’. The tube-
to-‘Bucky’ distance was kept constant at 1.5 m.
An experienced clinician conducted all radiographic analyses
using standard software (Genesis OmniVue
â
Genesis Digital Imag-
ing, Los Angeles, CA, USA). During analysis, the clinician was free to
magnify the images to increase accuracy (Fig. 2B,D are magnified
sections of Fig. 2A,C, respectively). When observed, the size of the
EOP was defined and measured in this 2D analysis as the distance in
millimetres from the most superior point of the EOP (origin) to a
point on the EOP that is most distal from the skull (Fig. 2B,D). To
avoid any ambiguity, the threshold for recording the size of an EOP
in this study was set at 5 mm, and an EOP was classified as enlarged
if it exceeded 10 mm. A simple size-dependent classification system
was also used to classify EOP into four categories: Class I (EOP <10
mm); Class II (10 mm EEOP <20 mm); Class III (20 mm EEOP <30
mm); and Class IV (EEOP 30 mm). Comparative studies have
demonstrated strong association between plain radiographic and
anatomical presentations (Gore et al. 1986). Importantly, it is
acknowledged that the anatomical level of degeneration is fre-
quently worse than the level of degeneration observed in radio-
graphs (Edeiken & Pitt, 1971; Gore et al. 1986). Accordingly, any
spur identified using this method is likely to be larger than it
appears on the plain radiographs.
To quantify the accuracy of these measurements, a disc-shaped
metallic object (8 mm in diameter) was attached to the skin adja-
cent to the C7 spinous processes of all Group A participants
(Fig. 2A). The diameter of this object on the radiographs was
assessed in 20 participants with the same methodologies used to
assess EOP size. The typical error of these measurements (TEM) was
Fig. 1 Illustration of an enlarged enthesophyte emanating from the
EOP.
©2016 Anatomical Society
Enlarged external occipital protuberance, D. Shahar and M.G.L. Sayers 287
less than 1 mm (0.2 mm). Similarly, to account for any perspective-
based (projection) errors resulting from differences in the distance
of each participant’s EOP fr om the ‘Bucky’ (as a function of d iffer-
ent torso widths), repeated measurements were taken from 11 male
and nine female participants. These data differed by less than the
typical error (i.e. <1 mm). As a result, raw data were left unad-
justed. Intra-observer reliability was assessed by having the same
assessor repeat the measurements of 20 participants with a mini-
mum of 4 months between analyses. Inter-observer reliability was
assessed by comparing these data with the results recorded by a
clinician external to this project who used the same methodologies.
Reliability testing involved the development of TEM and intra-class
correlation coefficients (ICC). Intra-observer reliability data showed
that EOP size could be reliably recorded (TEM =0.5 mm, ICC =0.99).
These data were similar for inter-observer reliability, although the
TEM values were slightly larger (TEM =1.4 mm, ICC =0.97).
The differences in EEOP size between the groups and genders
were determined using two-way analysis of variance (ANOVA). Differ-
ences between non-parametric variables were determined using
Chi-squared analyses. Standard residual (R) testing was used to rep-
resent the magnitude by which the observed frequency of an event
happening was above or below the expected value. An R-value of
2.0 or 2.0 represented a value either substantially more or less
(respectively) than the expected value (Grimm, 1993). All statistical
analyses were performed using the statistics package SPSS for Win-
dows (version 20), with an alpha level of P<0.05. Data are pre-
sented as means [1 standard deviation (SD)] unless stated
otherwise.
Results
Results from ANOVA testing indicated that 41% of the total
population presented with EEOP equal or greater than 10
mm. The prevalence of an EEOP was significantly higher in
the male (67.4%) than in the female population (20.3%),
with the mean EEOP size for the combined male population
(15 7 mm) being significantly larger (P<0.001) than for
the combined female population (10 4 mm). Although
the mean EEOP size for Group A (14 7mm)wassigni-
cantly greater (P=0.006) than that recorded for Group B
(12 6 mm), these data differed by less than 2 mm. There
was no interaction effect between gender and group (P=
0.760). The mean value for EEOP in Group A males was 16
7 mm, while the mean value for EEOP size in the male
population of Group B was 14 6 mm. The mean value for
EEOP in Group A females was 11 5mm,whilethemean
value for EEOP in the female population of Group B was 9
3 mm. The total mean across both groups and genders
was recorded as 13 6 mm. The longest EEOP in the male
population measured 35.7 mm, while in the female popula-
tion it measured 25.5 mm.
Chi-squared analyses indicated that there were no differ-
ences in prevalence (P=0.571) or size classification of EEOP
between groups. Similarly, there were also no differences
within genders between groups (females, P=0.307; males,
P=0.409). However, females were more likely to record
Class I EOP than males (P<0.001), while males were more
likely to record Class II and III EEOP than females (P<0.001;
Fig. 3). Approximately half of Group B presented with
symptoms associated with the cervical (51.2%), thoracic
(50.4%) and/or lumbar (57.6%) regions, with 15.2% report-
ing mild headaches. There were no significant relationships
between the presence of an EEOP and any of the reported
symptoms, and none of this group reported specific pain at
the EOP.
Discussion
This study is the first to report and quantify the prevalence
of EEOP within apparently healthy, asymptomatic and
mildly symptomatic young adults. Forty-one percent of the
total population in this study presented with EEOP. Further-
more, 10% of the participants in this study displayed an
EEOP greater than 20 mm in length.
The current data indicate that a higher percentage
(67.4%) of the males presented with EEOP than the females
(20.3%), with the mean size of EEOP also being larger in
males than females. These gender-based differences sup-
port those reported previously in forensic and anthropolog-
ical studies (G
ulekon & Turgut, 2003). In contrast to the
current findings, Singh (2012) reported just one skull out of
the 40 analysed displayed an enlarged spur emanating out
AB CD
Fig. 2 (A,B) Images of a participant from Group A; (C,D) a participant from Group B. (B,D) An enlarged representation of the area surrounding
and including the EEOP in (A,C), respectively. (B,D) These images include a measurement line indicating the origin, tip and length of the EEOP.
©2016 Anatomical Society
Enlarged external occipital protuberance, D. Shahar and M.G.L. Sayers288
of the EOP (8 mm long). Conversely, the conclusion from a
recent report that was based on surgical intervention of
painful exostosis projecting from the EOP (n=3) suggested
that this condition is a normal variant in predisposed indi-
viduals (Marshall et al. 2015). However, due to the small
samples and absence of disease-, trauma-, postural-, recre-
ational- and occupational-related data, conclusions cannot
be drawn as to the prevalence and/or cause of EEOP.
The onset of entheseal disorders may be due to abun-
dance of pathophysiological processes as well as aging due
to mechanical factors (Benjamin et al. 2000; McGonagle
et al. 2001; Claudepierre & Voisin, 2005). Therefore, the cur-
rent findings in the young adult population in this study
raise two important considerations. Firstly, if the presence
of EEOP in young adults is due to pathophysiological pro-
cesses, the number of affected individuals should be consid-
erably less than the high percentage found in the current
study, particularly given that the prevalence of SpA in the
young adult Caucasian-European population is estimated at
0.52% (Braun et al. 1998; Sieper et al. 2006; Jacques et al.
2014). Secondly, if the presence of EEOP is due to aging and
mechanical factors, the EEOP should appear at a more
advanced age than that of the sample population. Accord-
ingly, it would appear that additional factors must be con-
sidered as the predominant drivers for this phenomenon.
Numerous studies associated with spur formation focus
on SpA (McGonagle et al. 2014). Fewer studies implicate
mechanical stress as a cause for this degenerative process
(McGonagle et al. 2014). Most of the literature involving
enthesopathy has been focused on spur formation at the
distal joints of the lower extremities (D’Agostino & Olivieri,
2006). Occipital horn syndrome (OHS) is an X-chromosome-
linked connective tissue disorder and is expressed mostly in
male carriers (Bazzocchi et al. 2011). Patients suffering from
OHS may present with a slightly subnormal intelligence and
autonomic dysfunction conditions (Bazzocchi et al. 2011).
In view of the high prevalence of EEOP in the test popula-
tion and due to their young age, it is unlikely that members
of the population involved in this study suffer from SpA or
degeneration due to advanced age. Moreover, none of the
symptoms associated with OHS was reported by any of the
participants.
The high percentage (41%) of EEOP presentation in
the test population was surprising. The prevalence of an
EEOP in the young age group may suggest that excessive
forces are acting on the EOP at a younger age. Recent
animal studies have demonstrated the significant role
mechanical loads play in osteophyte formation (Jacques
et al. 2014). Similarly, current magnetic resonance imag-
ing studies have proposed that new bone deposition is
more probable at sites of repetitive stress where
advanced spinal degeneration and sclerosis was demon-
strated unlike sites displaying acute injury that resolves
completely (Maksymowych et al. 2013; Jacques &
McGonagle, 2014). Although not the primary focus of
this research, EEOP in the test populations may be attrib-
uted to, and explained by, the extensive use of screen-
based activities by children and adolescents (Straker et al.
2008; Torsheim et al. 2010; Gustafsson et al. 2011; Brink
et al. 2015), and the associated poor posture (Brink et al.
2015). These data may also explain the significantly larger
EOP size presented by Group A (university students) com-
pared with Group B (mildly symptomatic clinical popula-
tion). However, the EOP size differed by less than 2 mm
between these groups, a measure close to the inter-
observer TEM, and so this difference is probably not clini-
cally meaningful. Accordingly, in the absence of reduction
in the mechanical stressors, it is likely that these entheso-
phytes will increase in size as part of the normal ageing
processes.
The original findings of this study have a number of
implications for future research. The most profound value
ofdetectingEEOPatanearlyageisthatitmayserveas
an indicator, alerting clinicians and individuals to the
Fig. 3 Distribution of the external occipital
protuberance (EOP) within the various size
classifications between genders.
©2016 Anatomical Society
Enlarged external occipital protuberance, D. Shahar and M.G.L. Sayers 289
potential risk of early development of preventable muscu-
loskeletal disorders related to poor posture and biome-
chanical stress. Although the presence and size of EEOP in
this young adult population appears to be asymptomatic,
it is probable that increased growth of these entheso-
phytes may instigate or exacerbate symptoms associated
with ageing. The authors acknowledge that the results
may be specific to the test populations and may not be
generalised to other age groups. Further research into this
phenomenon across all age groups is required. Similarly,
the absence of postural and ergonomic data restricts
definitive conclusions on the causes of EEOP in the test
population. However, the age of the population and high
incidence of EEOP suggests that it is unlikely that the cur-
rent observations are a result of aging-, genetic- or dis-
ease-related processes.
Conclusion
This detailed analysis is the first of its kind to be used in the
assessment of the prevalence of EEOP in the young adult
population. The measurement techniques are shown to be
both valid and reliable. The comparatively young age of
the population examined and the high prevalence of EEOP
recorded in this study suggest that biomechanical drivers
should be considered as a primary cause of this condition in
this population. The findings were more significant than
anticipated with regard to the prevalence of this condition
and the size of the enthesophytes with the populations
tested. The current findings represent an important
research advance for two reasons: (i) they identify, quantify
and report the EEOP phenomenon in young adults; and (ii)
the prevalence of EEOP in the young adult population
serves as an early warning to the development of further
preventable poor posture-related conditions in the future.
This later observation may be related to the growing con-
cerns amongst researchers and societies pertaining to the
increased use of hand-held technologies from early child-
hood, and may suggest that early prevention and interven-
tion should be considered.
Acknowledgement
The authors thank L ee Daffin for his contribution during both data
collection and reliability testing, and Professor Richard G. Burns for
his valuable editorial advice.
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Nordic countries. BMC Public Health 10, 324.
©2016 Anatomical Society
Enlarged external occipital protuberance, D. Shahar and M.G.L. Sayers 291
... Shahar and Sayers have recently published several research studies investigating the prevalence of an enlarged external occipital protuberance (EOP), as defined by the authors, across a young and diverse age population [5][6][7]. Due to the unexpected finding of a high prevalence of the enlarged EOP in a young population, devoid of a genetic or inflammatory explanation, the authors concluded that poor posture, influenced by modern, extensive use of handheld devices may reflect a cause of this phenomenon. Because the enthesophyte is potentially symptomatic at this site, and in general enthesopathy may require some form of medical or surgical management, the authors drew attention to this possible association. ...
... In a consensus fashion all images from this group were reviewed by two radiologists, one with fellowship training in musculoskeletal radiology and a total of 9 years of experience following fellowship (JP), and the other a third-year radiology resident (PS), to determine the presence or absence of an exophytic EOP, in a similar fashion to that described by Shahar et al. [5][6][7]. We documented the presence or absence of an exophytic EOP and the length of this protuberance when present on the lateral view. ...
... We documented the presence or absence of an exophytic EOP and the length of this protuberance when present on the lateral view. Notably, all exophytic EOPs were measured and recorded in our study, in contrast to the prior studies by Shahar et al. [5][6][7], in which those EOPs less than 5 mm were omitted. ...
Article
Introduction: In controversial fashion, the presence of an enlarged external occipital protuberance has been recently linked to excessive use of handheld electronic devices. We sought to determine the prevalence of this protuberance in a diverse age group of adults from two separate time periods, before and approximately 10 years after the release of the iPhone, to further characterize this theory, as if indeed valid, such a relationship could direct preventative behavior. Materials and Methods: Eighty-two cervical spine radiographs between March 7, 2007 through June 29, 2007 and 147 cervical spine radiographs between October 25, 2017 through January 1, 2018 were reviewed for the presence or absence of an exophytic external occipital protuberance. Influence of sex and age were also assessed. Results: There were 41/82 (50%) patients within the 2007 pre-iPhone group with an exophytic external occipital protuberance, ranging from 2.7-33.8 mm in length. Twenty-seven out of 82 (32.9%) had an external occipital protuberance at or above 10 mm. There were 49/147 (33.3%) patients within the 2017 post-iPhone group with an exophytic external occipital protuberance, ranging from 4.4-53.8 mm in length. Thirty-three out of 147 (22.4%) had an external occipital protuberance at or above 10 mm. When considering accessibility to the iPhone, sex, and age to the presence of an exophytic external occipital protuberance, only sex has a statistically significant association, p=0.000000033. Conclusion: We found no significant association with iPhone accessibility and an exophytic external occipital protuberance. Due to inherent limitations in the retrospective nature of the study, future research is needed to better examine the association of handheld electronic devices with exophytic external occipital protuberances.
... Another important significance is the role of enlarged EOP in the development of occipital neuralgia (Bogduk, 1981;Satyarthee, 2019). Recently, there has been increasing interest in the study of EOP, and several resultant studies have shown a variation in size with age and sex (Shahar & Sayers, 2016;Varghese et al., 2017;Jacques et al., 2020). ...
... An EOP was classified as enlarged (EEOP) if it exceeded 10 mm. The size-dependent classification system was used to classify EOP into three categories: class 1:< 10mm; class 2: 10 mm ≤ EOP < 20 mm; class 3: ≥ 20 mm (Shahar & Sayers, 2016). ...
... In a previous study performed using lateral cervical X-rays to measure the EOP, they found a frequency of enlarged EOP (i.e. EOP>10mm) of 41 %, thus showing a higher frequency than we found in our present study (Shahar & Sayers, 2016). Most studies showed a higher frequency of enlarged EOP in male populations compared to female populations, a finding confirmed by our study. ...
Article
AL-RYALAT, N.; SAMARA, O.; HADIDY, A.; AL-NAJJAR, M.; MUBARAK, N.; ABDULMUNEM, H.; ALHADIDI, F. & ALRYALAT, S. A. Frequency of enlarged external occipital protuberance and its association with age and sex: A cross-sectional CT scan study. SUMMARY: External occipital protuberance (EOP) is a midline bony protrusion in the occipital bone, the significance of which has gained recent attention in the medical community. Our present study aims to assess the average size of EOP in a Jordanian cohort and its relation to age and sex, while determining the frequency of enlarged EOP in this cohort. The present study was a cross-sectional study that was carried out in a referral hospital in Jordan. We reviewed thousands of CT scans taken with dedicated bone window imaging during the last two years, beginning January 2018. Measurements were taken by trained radiology residents and were then further reviewed by radiology specialists. An EOP was classified as enlarged (EEOP) if it exceeded 10 mm.A total of 4409 patients, 2265 (51.4 %) females and 2144 (48.6 %) males, met our inclusion criteria. Their mean age was 54.1 ± 22.2 years. The mean size of the EOP in these patients was 8.4 ± 4.2 mm (range: 0-56 mm). Out of the 4409-study population, 1210 (27.4 %) presented with EEOP. The prevalence of an EEOP was significantly higher in the male population (33.6 %) when compared with the female population (21.6 %) (P < 0.001). The size of the EOP was also significantly related to the age of the patient, with EEOP increasing with increasing age. The mean size of EOP in our Jordanian cohort was 8.4 ± 4.2 mm. The frequency of enlarged EOP was found to be 27.4 % in our cohort, and was significantly more common in males and in older patients.
... Another important significance is the role of enlarged EOP in the development of occipital neuralgia (Bogduk, 1981;Satyarthee, 2019). Recently, there has been increasing interest in the study of EOP, and several resultant studies have shown a variation in size with age and sex (Shahar & Sayers, 2016;Varghese et al., 2017;Jacques et al., 2020). ...
... An EOP was classified as enlarged (EEOP) if it exceeded 10 mm. The size-dependent classification system was used to classify EOP into three categories: class 1:< 10mm; class 2: 10 mm ≤ EOP < 20 mm; class 3: ≥ 20 mm (Shahar & Sayers, 2016). ...
... In a previous study performed using lateral cervical X-rays to measure the EOP, they found a frequency of enlarged EOP (i.e. EOP>10mm) of 41 %, thus showing a higher frequency than we found in our present study (Shahar & Sayers, 2016). Most studies showed a higher frequency of enlarged EOP in male populations compared to female populations, a finding confirmed by our study. ...
Article
Full-text available
External occipital protuberance (EOP) is a midline bony protrusion in the occipital bone, the significance of which has gained recent attention in the medical community. Our present study aims to assess the average size of EOP in a Jordanian cohort and its relation to age and sex, while determining the frequency of enlarged EOP in this cohort. The present study was a cross-sectional study that was carried out in a referral hospital in Jordan. We reviewed thousands of CT scans taken with dedicated bone window imaging during the last two years, beginning January 2018. Measurements were taken by trained radiology residents and were then further reviewed by radiology specialists. An EOP was classified as enlarged (EEOP) if it exceeded 10 mm.A total of 4409 patients, 2265 (51.4 %) females and 2144 (48.6 %) males, met our inclusion criteria. Their mean age was 54.1 ± 22.2 years. The mean size of the EOP in these patients was 8.4 ± 4.2 mm (range: 0-56 mm). Out of the 4409-study population, 1210 (27.4 %) presented with EEOP. The prevalence of an EEOP was significantly higher in the male population (33.6 %) when compared with the female population (21.6 %) (P < 0.001). The size of the EOP was also significantly related to the age of the patient, with EEOP increasing with increasing age. The mean size of EOP in our Jordanian cohort was 8.4 ± 4.2 mm. The frequency of enlarged EOP was found to be 27.4 % in our cohort, and was significantly more common in males and in older patients.
... The EOP has been explored as a craniometric point of the occipital bone, an indicator of gender discrimination, and a site of occipitocervical fixation and its relationship with dural venous sinuses lying below [2-4, 6, 8, 10, 13, 14, 20]. In clinical settings, unusually enlarged EOPs and painful exostosis of the EOP have received attention [9,11,12,15,17,18]. ...
... Therefore, a well-controlled, prospective study is necessary in a large population to validate the outcomes of our study. Unproven etiology of unusually enlarged EOPs that have been documented to be prevalent in young adult populations is also a subject to be resolved [9,17]. Despite these limitations, we believe that the results of this study can be a help for better understanding of the EOP, in addition to safe surgical maneuvers around it. ...
Article
Full-text available
Purpose To date, no study has explored the external occipital protuberance (EOP) using neuroimaging modalities. This study aims to characterize them using magnetic resonance imaging (MRI). Methods A total of 96 patients underwent thin-sliced, post-contrast MRI. The sagittal images were analyzed. Results In 97%, the EOPs were delineated as a focal external protrusion of the midline region of the occiput with varying morphologies. In 89% of 93 patients with identifiable EOPs, parts of the intracranial dural sinuses were found to lie just below the inion, the most prominent point of the EOP. The most frequently targeted dural sinus was the confluence of sinuses that was found in 57%, followed by the superior sagittal sinus. In 16%, a bony foramen and transmitting vessel were detected in the EOP, connecting between the diploic channels and the subcutaneous veins. Furthermore, in 33%, bony foramina and transmitting venous structures were identified in the region just below the EOPs, connecting between the diploic channels and the subcutaneous veins. Conclusions The intracranial dural venous sinus is located just below the EOP with a high probability. Most bony foramina in the EOP and midline suboccipital region may transmit venous structures connecting to the diploic channel.
... Though reported rarely, three types have been described by Varghese etal (3) -flat (type-1), crest (type-2), spine (type-3). A study by Shahar etal (4) reports the frequent finding of occipital spurs in males which is often used in forensic investigations to determine the gender. Though seen occasionally, occipital spur may show growth spurts during late adolescence. ...
Article
Full-text available
Prominent external occipital protuberance is called occipital knob or spur or occipital bun. Though it was a persistent feature of early modern Europeans, it is extremely rare in the present modern era. Occipital spur was found to be one of the characteristic features of the ancestral Neanderthal trait. Variant anatomy of occipital region forms differential diagnosis in conditions associated with unexplained occipital pain. The present study has been done to evaluate the different morphological forms of occipital knobs. 56 skulls including partial and complete skulls were examined in the department of Anatomy. Broken and incomplete skulls were excluded from the study. 5 (8.92%) skulls were found to exhibit different forms of occipital knobs. 3 skulls had type 1(flat) occipital knob. Type 2 (crest) and type 3 (spine) variants have been observed in one skull each. An inca bone was found coincidentally in a skull with flat type of occipital knob which also had three accessory emissary foramina located near foramen magnum. The skull with crest type of occipital knob had two accessory emissary foramina-at the external occipital crest and near foramen magnum. Knowledge of variant occipital knobs is an example of application of basic sciences in clinical correlation, one of the goals of the new competency based medical education. Though asymptomatic, discomfort in the occipital region due to occipital spur has to be notified in the differential diagnosis. When symptomatic it could be one of the etiology of occipital headache, mandating surgical excision. To conclude, our study presents occipital knob which is a rare variant of occipital bone near external occipital protuberance that exhibited three forms-flat, crest and spine. Coincidentally inca bone and accessory emissary foramina near foramen magnum also have been observed.
... Though reported rarely, three types have been described by Varghese etal (3) -flat (type-1), crest (type-2), spine (type-3). A study by Shahar etal (4) reports the frequent finding of occipital spurs in males which is often used in forensic investigations to determine the gender. Though seen occasionally, occipital spur may show growth spurts during late adolescence. ...
Article
Full-text available
Prominent external occipital protuberance is called occipital knob or spur or occipital bun. Though it was a persistent feature of early modern Europeans, it is extremely rare in the present modern era. Occipital spur was found to be one of the characteristic features of the ancestral Neanderthal trait. Variant anatomy of occipital region forms differential diagnosis in conditions associated with unexplained occipital pain. The present study has been done to evaluate the different morphological forms of occipital knobs. 56 skulls including partial and complete skulls were examined in the department of Anatomy. Broken and incomplete skulls were excluded from the study. 5 (8.92%) skulls were found to exhibit different forms of occipital knobs. 3 skulls had type 1(flat) occipital knob. Type 2 (crest) and type 3 (spine) variants have been observed in one skull each. An inca bone was found coincidentally in a skull with flat type of occipital knob which also had three accessory emissary foramina located near foramen magnum. The skull with crest type of occipital knob had two accessory emissary foramina-at the external occipital crest and near foramen magnum. Knowledge of variant occipital knobs is an example of application of basic sciences in clinical correlation, one of the goals of the new competency based medical education. Though asymptomatic, discomfort in the occipital region due to occipital spur has to be notified in the differential diagnosis. When symptomatic it could be one of the etiology of occipital headache, mandating surgical excision. To conclude, our study presents occipital knob which is a rare variant of occipital bone near external occipital protuberance that exhibited three forms-flat, crest and spine. Coincidentally inca bone and accessory emissary foramina near foramen magnum also have been observed.
... Occipital morphological variation of modern human with consideration of sex, ancestry and size the neck muscles, thus contributing to a high prevalence of enlarged external occipital protuberance (EEOP) in young adults [85,89]. ...
Article
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Objectives To investigate three-dimensional morphological variation of the occipital bone between sexes and among populations, to determine how ancestry, sex and size account for occipital shape variation and to describe the exact forms by which the differences are expressed. Methods CT data for 214 modern crania of Asian, African and European ancestry were compared using 3D geometric morphometrics and multivariate statistics, including principal component analysis, Hotelling’s T ² test, multivariate regression, ANOVA, and MANCOVA. Results Sex differences in average occipital morphology are only observed in Europeans, with males exhibiting a pronounced inion. Significant ancestral differences are observed among all samples and are shared by males and females. Asian and African crania have smaller biasterionic breadths and flatter clivus angles compared to Europeans. Asian and European crania are similar in their nuchal and occipital plane proportions, nuchal and occipital angles, and lower inion positions compared to Africans. Centroid size significantly differs between sexes and among populations. The overall allometry, while significant, explains little of the shape variation. Larger occipital bones were associated with a more curved occipital plane, a pronounced inion, a narrower biasterionic breadth, a more flexed clivus, and a lower and relatively smaller foramen magnum. Conclusions Although significant shape differences were observed among populations, it is not recommended to use occipital morphology in sex or population estimation as both factors explained little of the observed variance. Other factors, relating to function and the environment, are suggested to be greater contributors to occipital variation. For the same reason, it is also not recommended to use the occiput in phylogenetic studies.
Article
Objective To evaluate the presence of occipital spurs, morphologic/morphometric features, and the presence of ossification of ligamentum nuchae (ONL) on lateral cephalometric radiographs of individuals aged under and over 18 years.Methods Lateral cephalometric radiographs of 1430 individuals aged between 14–50 years were scanned. The presence of ONL and occipital spurs was evaluated in 1312 patients who met the inclusion criteria, and existing occipital spurs were measured and their types (flat/crest/spine) were recorded.ResultsOccipital spurs were detected in 63 patients aged over 18 years (63/120; 52.5%) and 57 patients aged under 18 years (57/120; 47.5%). When the spur length by age category and sex was evaluated, no statistically significant difference was observed. The spur types seen were flat (40.8%; 49/120), crest (30%; 36/120) and spine (29.2%; 35/120), respectively. Although there was no statistically significant difference between the spur types seen in terms of age, a significant difference was observed between the sexes in the total group (p < 0.001). Spine-type spurs (66.7%; 18/27) were the most common in females, and flat-type spurs (45.2%; 42/39) were the most common in males. ONL was detected in only three individuals.Conclusion No relationship was found between the presence of occipital spurs and ONL. Although spur length was not affected by age and sex, spur types were found to vary according to sex. Occipital spurs are mostly asymptomatic and detected incidentally on lateral cephalometric radiographs. They are one of the important anatomic formations that should be diagnosed by physicians.
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OBJECTIVE: Previous studies of skeletal remains have suggested that both enthesophytes and osteophytes are manifestations of an underlying bone-forming tendency. A greater prevalence of osteophytes has been observed among individuals with high bone mass (HBM) compared with controls. This study was undertaken to examine the possible interrelationships between bone mass, enthesophytes, and osteophytes in a population of individuals with extreme HBM. METHODS: Cases of HBM (defined according to bone mineral density [BMD] Z scores on dual x-ray absorptiometry) from the UK-based HBM study were compared with a control group comprising unaffected family members and general population controls from the Chingford and Hertfordshire cohort studies. Pelvic radiographs from cases and controls were pooled and evaluated, in a blinded manner, by a single observer, who performed semiquantitative grading of the radiographs for the presence and severity of osteophytes and enthesophytes (score range 0-3 for each). Logistic regression analysis was used to identify significant associations, with a priori adjustment for age, sex, and body mass index. RESULTS: In this study, 226 radiographs from HBM cases and 437 radiographs from control subjects were included. Enthesophytes (grade ≥1) and moderate enthesophytes (grade ≥2) were more prevalent in HBM cases compared with controls (adjusted odds ratio [OR] 3.00 [95% confidence interval (95% CI) 1.96-4.58], P < 0.001 for any enthesophyte; adjusted OR 4.33 [95% CI 2.67-7.02], P < 0.001 for moderate enthesophytes). In the combined population of cases and controls, the enthesophyte grade was positively associated with BMD at both the total hip and lumbar spine (adjusted P for trend 2-fold (P < 0.001). CONCLUSION: Strong interrelationships were observed between osteophytes, enthesophytes, and HBM, which may be helpful in defining a distinct subset of patients with osteoarthritis characterized by excess bone formation.
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Spondyloarthritides (SpA) are characterised by both peripheral and axial arthritis. The hallmarks of peripheral SpA are the development of enthesitis, most typically of the Achilles tendon and plantar fascia, and new bone formation. This study was undertaken to unravel the mechanisms leading towards enthesitis and new bone formation in preclinical models of SpA. First, we demonstrated that TNF(ΔARE) mice show typical inflammatory features highly reminiscent of SpA. The first signs of inflammation were found at the entheses. Importantly, enthesitis occurred equally in the presence or absence of mature T and B cells, underscoring the importance of stromal cells. Hind limb unloading in TNF(ΔARE) mice significantly suppressed inflammation of the Achilles tendon compared with weight bearing controls. Erk1/2 signalling plays a crucial role in mechanotransduction-associated inflammation. Furthermore, new bone formation is strongly promoted at entheseal sites by biomechanical stress and correlates with the degree of inflammation. These findings provide a formal proof of the concept that mechanical strain drives both entheseal inflammation and new bone formation in SpA.
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There is evidence that consistent sitting for prolonged periods is associated with upper quadrant musculoskeletal pain (UQMP). It is unclear whether postural alignment is a significant risk factor. The aim of the prospective study (2010-2011) was to ascertain if three-dimensional sitting postural angles, measured in a real-life school computer classroom setting, predict seated-related UQMP. Asymptomatic Grade 10 high-school students, aged 15-17 years, undertaking Computer Application Technology, were eligible to participate. Using the 3D Posture Analysis Tool, sitting posture was measured while students used desk-top computers. Posture was reported as five upper quadrant angles (Head flexion, Neck flexion; Craniocervical angle, Trunk flexion and Head lateral bending). The Computer Usage Questionnaire measured seated-related UQMP and hours of computer use. The Beck Depression Inventory and the Multidimensional Anxiety Scale for Children assessed psychosocial factors. Sitting posture, computer use and psychosocial factors were measured at baseline. UQMP was measured at six months and one-year follow-up. 211, 190 and 153 students participated at baseline, six months and one-year follow-up respectively. 34.2% students complained of seated-related UQMP during the follow-up period. Increased head flexion (HF) predicted seated-related UQMP developing over time for a small group of students with pain scores greater than the 90th pain percentile, adjusted for age, gender, BMI, computer use and psychosocial factors (p = 0.003). The pain score increased 0.22 points per 1° increase in HF. Classroom ergonomics and postural hygiene should therefore focus on reducing large HF angles among computing adolescents. Copyright © 2015 Elsevier Ltd. All rights reserved.
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Occipital pain is a common complaint amongst patients with headache, and the differential can include many primary headache disorders such as cervicogenic headache or migraine. Occipital neuralgia is an uncommon cause of occipital pain characterized by paroxysmal lancinating pain in the distribution of the greater, lesser or third occipital nerves. Greater occipital nerve blockade with anesthetics and/or corticosteroids can aid in confirming the diagnosis and providing pain relief. However, nerve blocks are also effective in migraine headache and misdiagnosis can result in a false positive. Physical therapy and preventive medication with antiepileptics and tricyclic antidepressants are often effective treatments for occipital neuralgia. Refractory cases may require intervention with pulsed radiofrequency or occipital nerve stimulation.
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Jacques et al 1 provide proof of concept that experimental spondyloarthritis (SpA) may be a biomechanically triggered process. The implication is that an aberrant mesenchymal tissue response to physiological mechanical forces that occur during joint movement may trigger inflammation associated with SpA. Given the long-known genetic association of human SpA with human leukocyte antigen (HLA)-B27,2 which governs initiation of adaptive immune responses, the concept that SpA resembles a biomechanically driven rather than autoimmune disease may come as a great surprise. The en face argument that mechanically driven animal models bear no resemblance to human SpA, however, has to be taken with caution, given that the role of mechanics in human SpA has several supporting strands of evidence that date back over 50 years. Jacques and colleagues show that the earliest lesions in their model are localised at the Achilles tendon. As far back as 1959, La Cava, in his prophetic commentary on enthesitis, but not specifically in relationship to SpA, recognised that “the continually recurring concentration of muscle stress at these points provokes a reaction of inflammation with a strong tendency to the formation of fibrosis and calcification”.3 He also stated that insertions appeared to show ‘a peculiar reaction to irritative stimuli’ and that such stimuli were most frequently ‘microtraumatic in origin’. Since that time evidence has accumulated that supports all aspects of these suppositions. In the 1970s, Moll and Wright deduced the clinical concept of SpA.4–6 Although they did not pinpoint the ‘invisible unifying concept’, which appears to be mechanical stress, they recognised that physical trauma to joints appeared to trigger psoriatic arthritis and speculated that psoriatic arthritis (PsA) represented a ‘Deep Koebner response’. However, they did not specifically recognise the importance of the entheseal organ as the link between biomechanics and inflammation. Likewise, nail …