Keywords
musculoskeletal ultrasound - external occipital protuberance exostosis - invasive
physiotherapy
Introduction
The main purpose of an enthesis is the homogeneous distribution of loads, via the
interwoven fibers that form the same, at the exact site where capsules, ligaments
or tendons are attached to the bone. Therefore, the enthesis absorbs a great amount
of mechanical stress at the insertion. The formation of osteophytes at the enthesis
or attachment of the tendon to the bone is multifactorial, as it can be the result
of genetic, biomechanical and/or immunological factors.[1]
[2] The appearance of the same is not exclusive to the extremities, however, it is also
possible to find entheses in the axial skeleton, these commonly respond to aging processes,
and therefore are present in older patients.[3]
Typically, the diagnosis and visualization is performed based on radiographic studies
([Fig. 1]) and because of their slow development over time, they are rarely observed in young
adults.[3] In the scientific literature, many studies have analyzed the incidence and symptomatological
relationship of osteophyte growth in limb entheses related to defective load distribution.[4]
[5]
[6] In contrast, the evidence corresponding to the presence of osteophytes in the enthesis
in the axial skeleton is not only attributed to defective traction or compression
forces, but also to non-mechanical causes.[7] The current scientific literature concerning possible osteophytes present in the
skull is very scarce. Shahar et cols[8] describe the differences and/or implications that the growth of osteophytes may
have at the level of the external occipital protuberance (EOP) among young adults.
Although it appears to be asymptomatic, it is likely that an increase in the size
of these osteophytes may exacerbate symptoms with aging.
Fig. 1 Radiological study of exostosis on the external occipital protuberance.
Currently, the use of ultrasound is undergoing constant progress and development in
the field of physiotherapy, considered as a very important tool at a clinical level
both for physiotherapy assessment and diagnosis, as well as for treatment and subsequent
monitoring, as it provides the physiotherapist with a dynamic, objective, fast, effective
and real time study of the neuromusculoskeletal system.[9]
Therefore, the main aim of this study was to describe the ideal exam protocol for
the ultrasound identification and evaluation of osteophytes on the enthesis of the
upper trapezius muscle on the SOP, and to analyze the possible clinical implications.
Scan Description
Patient Position
The patient is placed in prone lying with a comfortable position of the neck, using
the face hole of the treatment table, avoiding cranio-cervical hyperextension, which
hinders access to the EOP, enabling optimal contact of the probe ([Fig. 2]).
Fig. 2 Ideal position for patient examination and ultrasound probe. Cross sectional scan
used as a reference.
Image Optimization
A linear probe is recommended with a low frequency range (8–10Mhz), which is variable
depending on the patient's subcutaneous cell tissue and muscle volume. The reference
section will be transversal to the axial axis, identifying a bony prominence, the
EOP, which generates a posterior acoustic shadow ([Fig. 3]). The location is confirmed with a section that is longitudinal to the axial axis
of the body, to visualize the proximal EOP and the entheses and the fibers of the
upper trapezius muscle arranged in a caudal direction. This is the section of choice
for assessment and measurement. With the proximal end of the probe, the EOP is located
and, distally, the proximal tendon insertion of the upper trapezius is visualized
in a longitudinal projection ([Fig. 4]). It is possible to assess and quantify the distance by measuring from the inion
to the most distal end of the possible exostosis. Based on the existing evidence,[8] 5mm is established as the minimum threshold for the measurement of the exostosis,
whereas 10mm is the threshold for its classification as an extended exostosis.
Fig. 3 Position of the probe in the longitudinal section of reference for evaluation and
measurement.
Fig. 4 Longitudinal ultrasound section, the reference used for assessment and measurement.
Discussion
As shown in the study by Shahar et al,[8] the finding of osteophytes in the EOP by means of X-rays is increasingly frequent
in daily clinical practice, with an incidence of 41%, affecting over 67% of men and
20% of women. Studies concerning cervical exostosis of the EOP are scarce and can
be classified into radiological or anatomical studies.[10] Assessment using musculoskeletal ultrasound allows greater immediacy and precision
in the observation of possible osteophytes at the level of the EOP. The scientific
literature describes different points of view regarding the cause behind the appearance
of these exostoses, however, both the reduced number of samples used and the absence
of relevant data on trauma, causative diseases, postural and occupational relationships,
do not allow us to draw valid conclusions regarding the prevalence and cause of exostosis
at the level of the EOP. Marshall et al[10] consider this as being an anatomical variant in late adolescence due to growth in
puberty, generating exostoses due to increased insertion load and sensitivity to palpation
in the area.[10] Moreover, authors such as Benjamin et al[1] and McGonagle et al[7] consider that these disorders may be due to mechanical factors that cause a physiopathological
process in the structure.[1]
[2]
Scientific Reports Nature Research published an article by Shahar et al[8] establishing the main etiology of repetitive traction on this enthesis by prolonged
positions of cranio-cervical flexion. A direct relationship is established with the
habitual and prolonged usage of mobiles and tablets.[8] Due to the extensive media coverage, the authors subsequently published a rectification
pointing out the observational nature of the study and therefore, objectively, no
direct relationships could be established.
Although major conclusions cannot be drawn with the current evidence available, the
young age of the patients in the aforementioned studies means that degenerative factors
are most likely ruled out, with excess stress or mechanical load on the enthesis being
the possible main cause, as reflected in recent animal studies.[11] Thus, it is important to consider that without a decrease in mechanical stress in
the area of the enthesis, it is also likely that the size of the osteophytes will
increase as a natural process of aging. No definitive results or conclusions can be
obtained due to the lack of postural and/or ergonomic data.
Considering these findings, in these cases, it would be interesting to observe and
determine possible direct relationships with the appearance of these entheses during
growth periods in puberty with similar exostoses such as the so-called Osgood-Schlatter
disease. In the latter case, these exostoses are located in the anterior tuberosity
of the tibia, in which high tension loads in the enthesis are described as the main
cause, not necessarily having a direct association with painful symptoms.[12]
The ultrasound finding described in this article may have several implications for
clinical practice and for future research. The use of ultrasound will allow a real-time,
radiation-free assessment, and can enable measurements and assessments of the bone
cortex and possible osteophytes found in the EOP. The clinical experience with ultrasound
assessment in other insertional tendon structures, allows us also to infer, in this
case, that with musculoskeletal ultrasound it is possible to evaluate the tendon tissue
surrounding this exostosis. This tissue which is directly anchored in the enthesis
is a source of possible pathologies and associated symptoms.
Likewise, the authors have frequently observed that this finding in the EOP is present
in asymptomatic subjects, in line with existing evidence.[8]
The ultrasound finding of this exostosis may indicate that this insertion area of
the upper trapezius muscle is a subjective area of high or repetitive mechanical traction.
Thus, the ultrasound assessment, always associated to the patient's clinical situation,
allows us to evaluate and plan our physiotherapy treatment to include preventive postural
measures that could aggravate this finding.
In the field of invasive physiotherapy, ultrasound allows us to objectify the exostosis,
enabling professionals to perform, when necessary, invasive interventions in the area
(for example with percutaneous needle electrolysis), while exercising caution to avoid
direct interventions upon the exostosis, and therefore avoiding irritation of the
periosteum.
