Sonographic Visualization of the Suprascapular Canal with Focus on the Suprascapular Notch: Anatomical Description and Ultrasound-Probe Techniques

Sonographic Visualization of the Suprascapular Canal with Focus on the Suprascapular Notch: Anatomical Description and Ultrasound-Probe Techniques | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Sonographic Visualization of the Suprascapular Canal with Focus on the Suprascapular Notch: Anatomical Description and Ultrasound-Probe Techniques Azzat Al-Redouan, Aimilia Theodorakioglou, Seyed Mehdi Sadat, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7808265/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 27 Feb, 2026 Read the published version in Surgical and Radiologic Anatomy → Version 1 posted 10 You are reading this latest preprint version Abstract Purpose Visualizing the suprascapular notch on radiographic images is challenging. Sonography of the suprascapular notch in the clinical practice had been performed only from a superior shoulder approach projecting a posterior view. Sonographic anterior view of the suprascapular notch has not been presented in the clinical practice. We provide anatomically based ultrasound-probe techniques to capture optimal sonograms exposing the suprascapular canal topography and its key structures. Methods Sonography of the superior shoulder region was bilaterally experimented on ten young healthy (five females and five males) volunteers of age ±21. We experimented scanning the superior and anterior area of the shoulder at differing angles with ultrasound probe explorative manipulations. Different shoulder maneuvers were attempted in seated and lying positions. Age, sex, BMI, and shoulder thickness were recorded. The visibility of the sonograms was compared based on the obtained parameters. In addition, ultrasound-guided tunnel insertion was performed on a fresh cadaver beside formalin fixed cadaveric dissection for confirmation and illustration of the suprascapular canal anatomy. Results A comprehensive protocol was constructed and tested yielding satisfactory sonographic visualization of the suprascapular canal and notch. The sonographic visibility and its quality seemed to be not affected by the BMI directly but by the shoulder thickness with better visibility in females compared to males. Conclusion We provide a four stepwise shoulder and ultrasound-probe maneuvers protocol yielding an anterior sonographic visibility of the suprascapular notch. This approach enhances the ultrasound-guided clinical practice in suprascapular nerve blocks with more precise targeting especially distal to the suprascapular notch. suprascapular canal ultrasound suprascapular notch ultrasound sonographic anatomy suprascapular nerve ultrasound sonography ultrasound Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Background Ultrasound-guided suprascapular nerve (SN) block is a common clinical procedure to relieve shoulder pain caused by SN entrapment syndromes [13–17, 19]. The ultrasound-guided approach is also applied in radiofrequency treatments [27]. Needle aspiration of ganglionic cystic in the SN is also performed with ultrasound guidance [19, 28]. In addition, it was proposed to utilize ultrasound-aided arthroscopic insertion during SN surgical decompression procedures [19]. In regard to diagnostic imaging modalities of SN entrapments, MRI does not yield optimal real-time images of the suprascapular notch (SSN) anatomy [4]. Ultrasonography became an emerging modality in the diagnostics of SN entrapments. However, sonography of the SSN is rather challenging [12, 14, 28] and requires skills and modification to its approach [14]. Obstacles in Sonographic Visualization of the Suprascapular Notch Even though sonographic examination gives advantage of ultrasound-probe (probe) manual handling that aligns the ultrasound transducer beam through the SSN vicinity, it still carries its own obstacles. Observer skills and experience with a learning curve are required to reach adequate sonograms [9]. The variability of the SSN morphology adds more challenge and uncertainties to its visualization [2, 12, 30]. Furthermore, doubts of the ultrasonic evaluation accuracy of the SSN has been addressed in the literature [14]. The Current State of the Art A sagittal-oblique sonographic cross-section through the long-axis of the suprascapular canal (SSC) is known and practiced in some clinical settings but still not documented in the literature. The SSC as a topographical space with comprehensive anatomical description is relatively recent in the literature and was published in a previous study [2]. Therefore, we believe to our best knowledge that this article provides a new insight into the sonographic anatomy of the whole extent of the SSC in the aforementioned cross-sectional orientation. Sonography of the SSN in the clinical practice have been performed only from a superior shoulder approach projecting a posterior coronal long-axis view of the SSN and is a routine clinical practice [12–17, 19, 21, 27, 30]. A four-step protocol to enhance the sonographic visibility of the SSN different morphological types was presented in the literature by Jezierski et al. in 2018 [12] projecting a posterior sonographic view of the SSN long-axis with focus on the suprascapular vessels ultrasound Doppler detection. In their protocol, the probe was aligned along the SSN short-axis in a sagittal plane and then rotated toward the SSN long-axis in a coronal plane, followed by sliding the probe forward and tilting until reaching a perpendicular plane view of the superior margin of the scapula. Their final step was dedicated to ultrasonic Doppler detection of the suprascapular vessels [12]. However, some images encountered in the literature designated the short-axis passage site of the SSC [2] as the SSN [4]. Ultrasonographic anterior approach to the SSN has not yet presented in the clinical practice and has been believed not to be possible. What is referred to throughout the literature as an anterior ultrasound approach [26, 29] is in fact a distal targeting of the SN above the clavicle at the site where the brachial plexus passes through the scalene fissure. The anterior approach below the clavicle visualizing the SSN anterior vicinity was not presented before, to our current best knowledge of the available literature. On the contrary, the spinoglenoid notch (SGN) can be visualized with ease by ultrasonography [28]. Therefore, it was not focused on in this article and was addressed as a part of the SSC only. The SGN is not situated as deep as the SSN [2] and is not masked by other surrounding sonographic structures [28]. It is captured on the ultrasound screen by placing the probe under the spine of the scapula (SPN) while sliding laterally with less required probe manipulation. Aims and Goals of the Proposed Sonographic Approach Hereby, we provide anatomic based probe manipulation techniques to capture optimal angle of insonations exposing the SSC topography and its key sonographic structures. Surface anatomy of palpable landmark structures is emphasized for more practical probe placement and manipulation. As a main focus, we provide a four stepwise shoulder and probe maneuver yielding a novel anterior sonographic view of the SSN. The Experimental Design Experimental Approach, We experimented scanning the superior and anterior area of the shoulder at differing angles with probe explorative manipulations. Different shoulder maneuvers were attempted in seated and lying positions. The selected experimented maneuvers were in attempts to move away the sonographic masking structures (clavicle mainly, and subscapularis muscle) that were preventing the projection of the ultrasound transducer to our target of interest, the SSN. The below described protocol was constructed after reaching optimal sonograms. The protocol was tested and verified experimentally on a fresh frozen cadaver as described below. Afterward, the sonographic examination was performed on all the ten volunteers by the main observer followed by the other five observers under the main observer guidance. Study Subjects Sonography of the superior shoulder region was bilaterally experimented on ten young healthy (five females and five males) volunteers of age ±23, with prior written consent. The BMI, shoulder thickness in addition to age and sex was recorded (Table 1). BMIs were obtained by BMI scales accessed via local fitness center facilities. The shoulder thickness was measured by a digital Vernier thickness caliper in two planes: 1) Vertical plane – by placing one end over the acromion and the other end under the axilla (arm in an abducted position), 2) Horizontal plane – by placing one on the base of the coracoid process (CP) and the second end under the SPN (arm in the natural anatomical position). The used ultrasound device was CANON APLIO i800 with Aplio's i-series 24 MHz Ultra-High Frequency iDMS Linear (i24LX8) and i-series 11 MHz Vascular Linear iDMS (i11LX3) transducers. Cadaveric Specimens for Experiment Testing and Illustration The SSC anatomy focused on illustrating the SSN topography was dissected on a 60+ years old female formalin-fixed cadaver. In addition, the gross anatomy as well as the sonographic anatomy was verified and illustrated on a 60+ years old male fresh frozen cadaveric specimen. Both cadavers belong to the body donor program for research and education purposes administered by the Department of Anatomy, Second Faculty of Medicine, Charles University where the research was conducted. Ethical Approval of Cadaveric Access and Volunteers Consent The study was performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. The study and volunteers consent procedure was approved for research and education purposes by the Institutional Review Board (IRB) – The Ethics Committee of the University Hospital Motol and Second Faculty of Medicine, Charles University, Prague, Czech Republic [Reference ID no. EK-353/19] and [Reference ID no. EK-1175.1.23/22]. Access to cadavers are under the local corps donor program in adherence to the Czech Anatomical Society and European Union ethical, legal regulation and provision in accordance with Act Code No. 89/2012 Sb. of the Civil Code and Act Code No. 372/2011 Sb. on Article 7 of the Health Services amended provision. Suprascapular Canal Cadaveric Dissection Illustration and Sonographic Approach The SSN is impended deep in the corner of the clavipectoral triangle (also known as the deltopectoral triangle) bordered by the clavicle superiorly, by the pectoralis major muscle inferiorly, and by the deltoid muscle laterally (Figure 1). This triangle forms a sonographic window for the probe placement as described below. Through this window the anterior vicinity of the SSN can be visualized. The SSN is bordered by the suprascapular ligament (SSL) in 93% of the cases [3] in approximately 7% is an enclosed by bone foramen variant of SSN [3]. Above the SSL is a musculofibrous opening bordered by the supraspinatus muscle (SUP) where pass the suprascapular vessels (SV) in majority of the cases [2]. The subscapularis muscle (SUB) run anteriorly below the SSN vicinity. The base of the CP forms the lateral border of the SSN, where it can be utilized as anatomical landmark in localizing the SSN (Figure 1C). The medial border of the SSN is formed by the medial peak of the SSN where the omohyoid muscle (OM) inserts (Figure 1D) with variability of its attachment onto the SSL medial portion [1]. Suprascapular Canal Cadaveric Anatomy Illustration A “Tunnel-Insertion” approach was performed by inserting a needle rod through the SGN by palpating its corner under the SPN as a blind non-imaging guidance (Figure 2A). The needle rod was navigated against the supraspinous fossa bone surface to exit through the SSN and proceeding it out of the cadaveric body under the clavicle (Figure 2B). A block incision resection through the SUP was made to expose the full length and orientation of the SSC (Figure 2C). The SSC run in an oblique direction connecting its two openings between the SGN and the SSN [2] (Figure 2D). The suprascapular space bounded by the SPN, acromion and clavicle serves landmarks to the imaging window of the SSC. Suprascapular Canal Cadaveric Sonographic Approach A second “Tunnel-Insertion” approach was performed on a fresh-frozen cadaveric body donor (Figure 3). The needle rod insertion was done under ultrasound guidance. The SGN was localized sonographically prior to the needle rod insertion (Figure 3D) and navigated through the SSC under ultrasound guidance (Figure 3F). The SSN long-axis view in an anterior projection was verified by visualizing the passing through needle rod on the sonogram (Figure 3E). This confirms the anatomic accuracy of obtained SSC sonogram (Figure 3G). The anechoic CP and the anechoic medial peak of the SSN with hyperechoic margin forms the sonographic landmarks of the SSN long-axis view in the anterior projection. The CP is localized under the clavicle in the SSC long-axis sagittal-oblique view indicating the location of the SSN, where the SPN indicates the location of the SGN (Figure 3). Further sonographic anatomy is described below in details in its corresponding subsections. Suprascapular Canal Sonography technique and Anatomy I. Sonography of the Suprascapular Canal Long-Axis View – Sagittal-Oblique Projection The sonographic anatomy of the SSC long-axis view and its probe placement and manipulation are illustrated in Figure 4 and in Video 1. The Sonographic Anatomy The long-axis of the SSC was captured in a sagittal-oblique cross-sectional plane extending throughout its full length from the SSN to the SGN (Figure 4). The SSC resides underneath the SUP (hypoechoic with striations of a typical sonographic muscle appearance [11] with a hyperechoic central tendon running between its hypoechoic anterior and posterior portions [22] as shown in Figure 4A) in the spinoglenoid fossa [2] with an entrance site through the SSN (hyperechoic on the right side of the ultrasound screen) which is seen adjacent to the base of the CP (anechoic with a hyperechoic bright rim demarcating its surface of a typical sonographic bone appearance) [11] (Figure 4A, 4D). However, the medial border of the SSN does not fall into view and lies medially to the ultrasound beam and do not align within the angle of insonation [5]. The SSL does not align with the angle of insonation and therefore is not visible. At the receding end, the SGN is visible on the left side of the ultrasound screen with a hypoechoic sonographic feature (Figure 4A, 4D). The orientation of the SGN gives it a better dimensional visibility advantage than the SSN. The angle of insonation falls perpendicular to the SGN vicinity with a better ultrasound reflection. The spinoglenoid ligament appears less echoic than the SSL due to its morphological nature of a thin membrane extending from the SUP fascia [2]. The bony margins of the SGN at its floor are formed by the infraspinous fossa margin and its medial border by the acromiospinal arch [2] and both are well visible with anechoic lined with hyperechoic bright rim sonographic appearance (Figure 4A, 4D). The neurovascular bundle is visible as a hyperechoic band running through the full length of the SSC between the SSN and the SGN (Figure 4A, 4D). Its visibility was enhanced by the below described shoulder maneuver (Video 1). This maneuver allows examining the muscle contraction dynamic effect on the underlying SSC space and its neurovascular bundle content. Figure 4E shows the passing SV through the SSN into the SSC by ultrasound Doppler detection. Patient Positioning The examination should be performed in a seated position with a low supporting backrest. The Ultrasound-Probe Manipulation and Surface Anatomical Landmarks The probe was placed above the spinoglenoid fossa [2] which is localized by the palpable acromion and SPN as its surface anatomical boundary landmarks (Figure 4B, 4C). The probe is oriented in a sagittal-oblique plane where the probe receding edge is compressed [5] against the palpable medial angle between the SPN and the acromion (Figure 4C). Meanwhile, the probe leading edge placement is maintained as far as possible from the clavicle. This allows for free probe sliding and rotation [5] above the SUP. The probe is then tilted laterally in approximately 10° degrees where the probe beam projects medially, this will adjust the angle of insonation (Figure 4C). Final adjustment is obtained by slightly sliding and sweeping [5] the probe with counterclockwise and clockwise probe rotation until the SSN on one end and the SGN on the other end are aligned on the ultrasound screen (Video 1). The Maneuver An arm abduction up to 45° degrees, controlled by the observer, lifts the SUP cranially stretching the SSC passage site [2] for better visibility of the underneath passing neurovascular bundle (Video 1). The sonogram is considered optimal when both openings of the SSC (SSN and SGN) are simultaneously visible on the ultrasound screen and the suprascapular neurovascular bundle is visibly coursing between the SSN and the SGN (Figure 4). II. Sonography of the Suprascapular Notch Long-Axis View – Posterior Projection The sonographic anatomy of this SSN long-axis view and its probe placement and manipulation are illustrated in Figure 5 and in Video 2. The Sonographic Anatomy The SSN is located anterior to the SSC and its long-axis anatomically oriented with a medial-inferior tilt in relation to the body plane [2]. The base of the CP appears anechoic with a hyperechoic bright line surface [11], and it forms the lateral border of the SSN [2] (Figure 5). The inferior margin of the SSN should appear as a hypoechoic curved margin (Figure 5A, 5D) and will appear slightly echoic if the SUP gets captured in the angle of insonation. In case the inferior margin is not captured, a slight probe pressure with tilt manipulation [5] is necessary to project a well-defined inferior margin of the SSN into the angle of insonation. The superior border of the scapula will appear as a demarcated anechoic margin below the largely visible hypoechoic trapezius muscle. Partial muscle fibers of the SUP may appear as hypoechoic bands on the medial side of the ultrasound screen (Figure 5A, 5D). The SSL long-axis appears as a hyperechoic shinning-white band extending between the base of the CP and the medial peak of the SSN. The SSN has a heterogeneous hyperechoic with anechoic dots sonographic appearance as it is occupied by adipose and loose connective tissue [11]. A cross-section of the SN short-axis is visible resembling a honeycomb shape-like structure (a typical sonographic feature of distally located nerves) [11], where its fascicles appear hypoechoic on a hyperechoic background (Figure 5A, 5D). The passing SV at the SSN can be detected by ultrasound Doppler with low sensitivity by the 11 MHz Linear transducers (Figure 5E). Patient Positioning The examination should be performed in a seated position with a low supporting backrest. The Ultrasound-Probe Manipulation and Surface Anatomical Landmarks The probe is placed parallel to the palpable SPN in a coronal-oblique plane to the body above the supraspinous fossa. The probe leading edge (or the receding edge according to personal preference) is placed with pressure and rocking manipulation [5] by the medial landmark surface of the acromioclavicular joint, where the articulating ends of the acromion and the clavicle are palpable (Figure 5C). The probe is then swept [5] in an anterior direction with a slight rotation (clockwise when scanning the right shoulder; counterclockwise when scanning the left shoulder) until the SSC short-axis view is projected corresponding to its anatomical oblique-transverse cross-section. After this point, the probe is manipulated by sliding and tilting maneuvers over the SSC short-axis towards the SSN until the base of the CP is visible and the attachment of the SSL at this site projects on the monitor (Figure 5C). The SSN is now located (Video 2). To adjust the angle of insonation, the probe receding edge is manipulated in explorative tilt, rocking, and pressure maneuvers [5] (while keeping the lateral side of the SSN visible on the monitor to not lose this anatomical landmark of its lateral boundary) until the full length of the SSL long-axis is visible (if possible, limitations described below) and its medial attachment onto the medial peak of the SSN appears on the screen (Figure 5A), (Video 2). Consequently, the ultrasonic probe beam will be perpendicular to the SSN long-axis where the probe beam projects in an antero-infero-medial direction to the body plane. The Maneuver No shoulder maneuver was necessary for this ultrasonographic projection. The sonogram is considered optimal when the SSL full extent is visible and the bony margins of the SSN are detectable (Figure 5A). A point of caution is when the SSL is not projected on the screen, it most probably indicates that the captured image is a transverse cross-section through the SSC (sonographic short-axis) and probably not the SSN [4]. In this case, further adjustment is needed by probe fan and sweep [5] manipulation (further limitations is described below). III. Sonography of the Suprascapular Notch Long-Axis View – Anterior Projection The sonographic anatomy of this SSN long-axis view and its probe placement and manipulation are illustrated in Figure 6 and in Video 3. The Sonographic Anatomy The topography of the SSN in this angle of insonation appears in much more detail [2] than in the aforementioned insonation angles. In addition to the SUP, the OM and the SUB are also visible (Figure 6). Unlike in the other angles of insonations, the CP appears as a whole and not just its base. The CP did not appear homogenous in its echogenicity as in the other sonographic views. The base of the CP forms the lateral border of the SSN long-axis and appears anechoic [11] with not well defined hyperechoic margin. The apex and body of the CP appear isoechoic due to the attaching muscles and ligaments (Figure 6A, 6D). The SUB appears more visible at first and its superior margin moves caudally as the maneuver (described below) is performed. It will then have a less hypoechoic appearance as it gets stretched and shifts downward (Video 3). This will unmask the SSN making it appear on the monitor with a relatively hyperechoic vicinity surrounded medially, laterally and inferiorly by a demarcated slightly hypoechoic margins (Figure 6A, 6D). The medial peak of the SSN is confirmed by a slow head and neck rotation to the opposite side causing the OM to be visibly stretching on the ultrasound monitor (Video 3). This enhances its visibility as its short-axis aligns into the angle of insonation [5] and appears hypoechoic with striations, a typical sonographic feature of a muscle [11] (Figure 6A, 6D). The superior boundary of the SSN is formed by the SSL and its long-axis (when visible, further limitations described below) appears hyperechoic as a shining white band running underneath and in a parallel direction to the inferior margin of the hypoechoic SUP. The full extent of the SSL is visible coursing between its two attachment sites, laterally the base of the CP (anechoic) and medially the medial peak of the SSN (hypoechoic due to the inserting OM fibers). The musculofibrous space between the SSL and the SUP may be visible as well with a heterogeneous hyperechoic sonographic appearance due to its occupying adipose and loose connective tissue (Figure 6A). The SN appeared (with poor visibility) hypoechoic, a typical sonographic feature of a proximally located nerve [11]. Nevertheless, the SN exhibited anisotropic feature as its short-axis lies oblique to the angle of insonation [5, 11]. The SN courses in a curved direction at this anatomical site as it passes from the omoclavicular triangle entering into the SSN [2]. Therefore, its short-axis do not align with the long-axis of the SSN vicinity. In addition, the echogenicity of the SN was of a relatively similar intensity to the SSN vicinity echogenicity in this specific angle of insonation targeting the long-axis of the SSN (Figure 6A, 6D). However, a slight arm maneuver in any possible direction (addiction, abduction, extension, flexion, internal and external rotation) had stretched the SN making it visible to detect as it wiggled on the ultrasound screen (Video 3). Regardless its less defined sonographic appearance [5, 11], this angle of insonation gave the advantage of examining the structural dynamic relationship between the SN and the surrounding sonographic structures at the anterior vicinity of the SSN. In addition, Figure 6E shows the passing SV at the SSN (above the SSL) by ultrasound Doppler detection. Patient Positioning The examination should be performed in a lying supine position on a bed with no arm support to assure suitable degrees of freedom to perform the below described arm maneuver. The Ultrasound-Probe Manipulation and Surface Anatomical Landmarks The probe receding edge (or the leading edge if different screen projection is preferred) is placed under the clavicle over the palpable CP with an approximately 10° degrees’ cranial tilt (also designated as fan) [5] in which the probe beam projects caudally in approximately 10° degrees from the body transverse plane (Figure 6C) while performing the below stepwise maneuver (Video3). While performing the maneuver, the surrounding structures (SUP, SUB and OM) can be seen stretching on the screen enhancing the sonographic visibility of the SSN boundaries (Video3). The angle of insonation is adjusted by rocking, fanning, and slight rotations [5] the probe. The Maneuver Four stepwise maneuvers while placing and manipulating the probe over the described anatomical landmarks (Figure 6), (Video 3): 1) The arm is abducted to approximately 45° degrees. This movement will contract and move the SUP lifting it cranially simultaneously with the clavicle. 2) The arm is rotated externally while the forearm is in a flexed position. This movement will cause the superior margin of the SUB to move caudally, further away from the SSN anterior vicinity. 3) The receding edge (or leading edge according to personal preference) of the probe is then placed under the clavicle on the palpable CP followed by sliding the probe medially to place its receding edge over the base of the CP. The lateral border of the SSN in its long-axis view will be detectable on the ultrasound monitor. 4) A slow contralateral head and neck rotation to the opposite side will stretch the OM and will be seen in motion on the ultrasound screen medial to the site of the base of the CP. Also, an ipsilateral head and neck rotation will cause the OM to contract and be seen in motion on the screen. However, stretching the OM gave it better defined short-axis hypoechoic visibility than contracting it. The sonogram is considered optimal when the full extent of the SSL, i.e. from the base of the CP to the medial peak of the SSN, becomes visible and the inferior border of the SSN is simultaneously noticeable in addition to the visible OM and partial fibers of the superior margin of the SUB (Figure 6A). Factors Affecting Sonographic Anatomical Visibility The visibility and its quality seemed to be not affected by the BMI directly but by the shoulder thickness. The closer the SSN to the cutaneous surface, the higher the resolution of the image. The penetration of the 24 MHz transducer ultrasound rays gives a good visibility of up to approximately 3.5 cm of sonographic depth. On the other hand, the 11 MHz ultrasound rays penetrates deeper into the body bringing the SSN in individuals with larger shoulder thickness into view but with less sonographic resolution compared to the 24 MHz transducer giving poor anatomical details. Ultrasound Doppler detection was not viable by the 24 MHz transducer and was only detected by the 11 MHz ultrasound. Apart from sonographic factors, the anatomical orientation of the shoulder girdle bones plays critical role in the visibility of the SSN. The clavicle can mask the vicinity of the SSN and require further explorative probe orientation with arm maneuvers. The SSN varies in size and exhibit five distinctive types. One type has a wider width than its depth, other has shorter width than its depth, and sometimes has equal width to depth [3, 12]. Two challenging SSN types may be encountered. Those are the discrete type where the SSN is not prominent in appearance; and the SSN foramen variant where it lacks a SSL with an ossified superior border [3, 12] that can hinder the ultrasound beam projection. Figures 7, 8, and 9 illustrate a spectrum of sonographic visibility governed by three critical parameters as detailed below. It appears to yield higher visibility in females than in males. Lower BMI gave better visibility to some extend in terms of structural details. Shoulder thickness was the prominent parameter in the sonographic visibility yielding more visibility when the structures lay within a depth of less than 3.5 cm from the body surface. Sonographic Visibility by Sex Anatomical Differences The shoulder joint stability and muscle dynamics power differs between the two sexes [6, 7, 24]. Females seems to have less muscle activation power at younger age according to some studies [6] while males tend to have more pectoralis major muscle stiffness [24]. The differences between the two sexes muscularity is observable and was reported in the literature [7]. Nevertheless, it is evidenced through cadaveric dissections as well as surface anatomy that the clavipectoral triangle (Figure 1) is wider in females than in males. This gives wider ultrasound access window into the SSN in the anterior view (Figure 6). On the other hand, males have a higher running superior margin of the pectoralis major muscle [23]. In addition, the trapezius muscle in males extends into larger insertion surface on the clavicle, acromion, and the SPN [25]. Similarly, the deltoid muscle in males occupies more surface at its origin (clavicle, acromion and SPN) [8, 20]. Consequently, the SUP in females tended to come into the sonographic view in the SSN anterior projection view with more ease (Figure 6A), while the pectoralis major and deltoid muscles tend to mask the SUP in males (Figure 6D). In addition, the BMI and shoulder thickness range in our study subjects were smaller in females (Table 1) yielding higher rate of sonographic visibility (Figure 7, 8, 9). The BMI range in females was 17.1 kg/m2 to 26.4 kg/m2 (mean: 18.6 kg/m2); and 20.4 kg/m2 to 27.4 kg/m2 (mean: 23.8 kg/m2) in males. The shoulder thickness in females was as low as 5.1 cm (mean: horizontal – 7.45 cm; vertical – 7.85 cm) while not less than 8.0 cm (mean: horizontal – 8.85 cm; vertical – 9.15 cm) in males. These two factors added favorable anatomical reach to the targeted structures in terms of less mass and less depth for the penetrating ultrasound beam in females compared to males. Sonographic Visibility by BMI Differences Obesity and muscle mass lower the sonographic visibility of the underlying in depth structures [18]. The sonographic visibility in our sample had diminished in individuals with BMIs > 24.0 kg/m2 prominently in the SSC long-axis view – sagittal-oblique projection (Figure 7) and in the SSN Long-axis view – posterior projection (Figure 8). However, the sonographic visibility was not diminished in the SSN long-axis view – anterior projection with relatively poor visibility in the individual with the highest BMI of > 27.0 kg/m2 (Figure 9). Sonographic Visibility by Shoulder Thickness Differences The ultrasound waves have limited capacity in penetrating through the body tissues, and the high frequency transducers used in ultrasound examinations of the musculoskeletal regions have limited reach [10]. The anatomical depth of the SSN is greater when approaching the SSN via the posterior projection compared to the anterior projection (Figure 10), in which only one case showed poor visibility in the anterior projection (Figure 9) while two cases of no visibility in the posterior projection (Figure 8). The SGN is located deeper than the SSN in the sagittal-oblique projection (Figure 10), in which the SGN was not visible in three cases while the SSN was not visible only in two cases (Figure 7). The female shoulder vertical thickness in our sample ranged from 6.0 cm to 9.8 cm, and the horizontal thickness ranged from 5.1 cm to 8.7 cm. On the other hand, the male shoulder vertical thickness ranged from 8.0 cm to 9.4 cm, and the horizontal thickness ranged from 8.3 cm to 9.7 cm. In addition, the trapezius muscle is relatively thicker in mass in males which adds more ultrasound reach distance than the actual measured vertical thickness [25]. Consequently, the depth of the structures from the surface was less in female subjects yielding more ultrasound reach with higher sonographic visibility. It was evidenced that the structures located in a depth of up to 3.5 cm from the body surface yielded more sonographic visibility than the structures located at more than 3.5 cm in depth, with slight variability (Figure 7, 8, 9). The vertical shoulder thickness was an indicator of the sonographic visibility in the sagittal-oblique projection (Figure 7) and in the posterior projection (Figure 8); while the horizontal shoulder thickness was an indicator of the sonographic visibility in the anterior projection (Figure 9). According to the shoulder thickness measurements and the sonograms, the SSC is situated approximately in the center of the two thickness axes (Figure 10). The SSN is situated in the anterior 1/4th distance, which is closer in the anterior projection to the probe but farther form it in the posterior projection. The SGN is situated beyond the center point of the two thickness axes, which is farther from the probe in the posterior projection – sagittal-oblique view of the SSC (Figure 10). Technical Gains and Clinical Implication The combination of these three sonographic views gives comprehensive assessment of the SSC enhancing a non-invasive diagnostic approach to SN entrapment syndrome. The novel anterior SSN view along with the SSC sagittal-oblique view sonographic examinations allow evaluating the muscles dynamics and assessing their pathological involvement in a suspected SN entrapment syndrome. Furthermore, these multiple imaging-guided sites provide wider range of SN block accesses. The SN can be reached more proximally than the commonly accessed distal to the SSN approach [13–17, 19, 27] in peripheral nerve pain management. A practical point of view, the sonographic visibility of the SSC can be predicted by the two proposed shoulder thickness axes (Figure 10) adding into account the sex and body composition in terms of the patients BMI. This can be estimated by approximating the structures localization in centimeters. In the posterior approach: shoulder vertical thickness divided by 2 to approximate the depth of the SSC in the sagittal-oblique view, and the depth of the SSN in the posterior view. In the anterior approach: shoulder horizontal thickness divided by 4 to approximate the depth of the SSN in the anterior view. Limitations The sonographic visibility is rather subjective and can be influenced by the skills of the sonographic examiner [9, 14]. The quality of the used devise also play role. The commonly used 11-17 MHz ultrasound transducers in shoulder examinations do not yield detailed resolution of the small SSN structure in size of approximately 10.0 x 6.0 mm [2, 3]. Even though the 24 MHz ultrasound transducers yield higher sonographic resolution, its beam penetration is limited to relatively shorter distance of approximately 3.5 cm. The SN is anisotropic and may not project with high visibility on sonograms (Figure 4, 5, 6). However, it is traceable while examining in vivo by the above described maneuvers (Video 1,2, 3). The SV varies in quantity and course at the SSN with relatively small diameters of approximately 0.5 mm to 5.0 mm [2]. The course of the SV curve in direction as they pass through the SSC [2]. Accordingly, the Doppler detection is not reliable in mapping the SV topography. Distinguishing between suprascapular artery and vein may not be accurately achieved (Figure 4E, 5E, 6E), (Video 1,2, 3). The demography of the volunteer individuals was young in age and in overall good health and physical condition (Table 1). The obtained imaging results do not reflect the population as a whole. This was an observational study aimed to provide a descriptive manual. Therefore, the sample size was small limiting its statistical analysis. The provided images reflect a long term experimentation and training. This method requires some amount of practice prior to deliver patient care. Statements and Declarations Acknowledgments The authors would like to acknowledge and thank David Kachlik (Department of Anatomy & Center for Endoscopic, Surgical and Clinical Anatomy (CESKA), Second Faculty of Medicine, Charles University, Prague, Czech Republic) for access to the cadaveric specimens and the ultrasound device; Nikola Jilkova and David Vala for their laboratory technical assistance. We also would like to acknowledge and thank the pregraduate students (Second Faculty of Medicine, Charles University, Prague, Czech Republic) Shihab Hajhamoud and Emma Sole Moreno for their assistance with the cadaveric specimen’s dissection, Omer Glazer for his assistance with the sonography practice, and Harshith Krishna Omprakash for his assistance with the video recordings. The authors sincerely thank those who donated their bodies to science so that anatomical research could be performed. Results from such research can potentially increase mankind's overall knowledge that can then improve patient care. Therefore, these donors and their families deserve our highest gratitude. Nonetheless, the authors would like to thank all the anonymous volunteers for their willingness and consent to volunteer. Their contribution was crucial and highly valuable. Conflict of Interest All authors declare no conflict of interest. Funding No funds, grants, or other support was received. Compliance with Ethical Standards The study was performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. Ethics Approval The study and volunteers consent procedure was approved for research and education purposes by the Institutional Review Board (IRB) – The Ethics Committee of the University Hospital Motol and Second Faculty of Medicine, Charles University, Prague, Czech Republic [Reference ID no. EK-353/19] and [Reference ID no. EK-1175.1.23/22]. Access to cadavers are under the local corps donor program in adherence to the Czech Anatomical Society and European Union ethical, legal regulation and provision in accordance with Act Code No. 89/2012 Sb. of the Civil Code and Act Code No. 372/2011 Sb. on Article 7 of the Health Services amended provision. Informed Consent Informed consent was obtained from all participants prior to their participation. Participants were informed about the nature and purpose of the research as well as the procedures involved. Participants consented to publish the obtained photos, sonograms, video demonstrations, and the recorded data was anonymized. Participant confidentiality was maintained throughout the study, and all data were anonymized in accordance with applicable data protection regulations. Note This work was conducted while the principal author was affiliated at [Department of Anatomy & Center for Endoscopic, Surgical and Clinical Anatomy (CESKA), Second Faculty of Medicine, Charles University, Prague, Czech Republic]. All necessary ethical approvals and facility use agreements were obtained during that time. CRediT Author Statement Azzat Al-Redouan : Conceptualization, Methodology, Investigation, Visualization, Formal analysis, Data curation, Validation, Supervision, Project administration, Writing - Original Draft. Aimilia Theodorakioglou : Methodology, Investigation, Visualization. Seyed Mehdi Sadat : Methodology, Investigation. Petra Kriskova : Investigation, Visualization. Pilar Dominguez R Fonte : Investigation. Deeksha Shailesh : Investigation. Shayan Ghezel Bash : Formal analysis. References Al-Redouan A, Benes M, Theodorakioglou A, Sadat SM, Modrak M, Kunc V, Kachlik D (2025) Muscles variations with topographical relationship to the suprascapular notch and its potential arthroscopic feasibility. Surg Radiol Anat 47(1):84. https://doi.org/10.1007/s00276-025-03595-y Al-Redouan A, Holding K, Kachlik D (2021) "Suprascapular canal": Anatomical and topographical description and its clinical implication in entrapment syndrome. Ann Anat 233:151593. https://doi.org/10.1016/j.aanat.2020.151593 Al-Redouan A, Hudak R, Nanka O, Kachlik D (2021) The morphological stenosis pattern of the suprascapular notch is revealed yielding higher incidence in the discrete type and elucidating the inevitability of osteoplasty in horizontally oriented stenosis. 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Surg Radiol Anat 31(6):409–414. https://doi.org/10.1007/s00276-008-0458-7 Table Table 1 is available in the Supplementary Files section Additional Declarations No competing interests reported. Supplementary Files Table1.docx Video1.mov Video 1. Sonography of the suprascapular canal long-axis view (left shoulder, in sagittal-oblique plane transducer manipulation). Legend: SSC – suprascapular canal, SSN – suprascapular notch, SGN – spinoglenoid notch, SUP – supraspinatus muscle (CT – supraspinatus central tendon, SUPf, supraspinatus fascia, at – anterior portion of the supraspinatus muscle, pt – posterior portion of the supraspinatus muscle), CL – clavicle, CP – coracoid process, SPN – spine of scapula, TRP – trapezius muscle. LD – transducer leading edge. Video2.mov Video 2. Sonography posterior projection of the suprascapular notch long-axis view (right shoulder superio-posterior transducer placement with coronal plane transducer manipulation). Legend: SSN – suprascapular notch, SSL – suprascapular ligament, SSC – suprascapular canal, SUP – supraspinatus muscle, CP – coracoid process, TRP – trapezius muscle. LD – transducer leading edge. Video3.mov Video 3. Sonography anterior projection of the suprascapular notch long-axis view (right shoulder, anterior transducer placement with transverse plane transducer manipulation). Legend: SSN – suprascapular notch, SSL – suprascapular ligament, SN – suprascapular nerve, SUP – supraspinatus muscle, SUB – subscapularis muscle, OM – omohyoid muscle, CP – coracoid process, Sv – suprascapular vessels. LD – transducer leading edge. Cite Share Download PDF Status: Published Journal Publication published 27 Feb, 2026 Read the published version in Surgical and Radiologic Anatomy → Version 1 posted Editorial decision: Revision requested 26 Jan, 2026 Reviews received at journal 26 Jan, 2026 Reviewers agreed at journal 26 Jan, 2026 Reviews received at journal 19 Dec, 2025 Reviewers agreed at journal 16 Dec, 2025 Reviewers agreed at journal 25 Oct, 2025 Reviewers invited by journal 09 Oct, 2025 Editor assigned by journal 09 Oct, 2025 Submission checks completed at journal 09 Oct, 2025 First submitted to journal 08 Oct, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7808265","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":533490969,"identity":"18b80294-e148-446a-a39f-394955e862f7","order_by":0,"name":"Azzat Al-Redouan","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABFklEQVRIiWNgGAWjYBADGRAhASL4QURCAQH1BxgYeOBaJBtAWgxI0WJwAEziVs3ff/zh5w8MdjwM0ocP3vjYZpdnfH514ocHBgzy/GIHsGqROHAgWeIAQzIPA19asuXMtuRisxtvN0sAHWY4c3YCdmsONhwAamHmYeDhMZPmbWNO3Hbj7AaQlgSD29i1yB9mbP5xgKEeqIX/G1BLfeLmGWc3/8CnxeAYMxvQlsMgW9iAWg4nbuDv3YbXFsMzbGwWZwyO87DxsBlbzjh3PHHGDd5tFgkGEjj9Inf++OMbFRXVcvw8zA9vfCirTuzvP7v55o8KG3l+aRzehziPgYENzpEAq5TAoxwD8B8gRfUoGAWjYBSMAAAAB2NZSQe94mUAAAAASUVORK5CYII=","orcid":"","institution":"Independent Researcher","correspondingAuthor":true,"prefix":"","firstName":"Azzat","middleName":"","lastName":"Al-Redouan","suffix":""},{"id":533490970,"identity":"d1bc0a46-9dd9-43c0-a478-4c39b4cbfec5","order_by":1,"name":"Aimilia Theodorakioglou","email":"","orcid":"","institution":"Independent Researcher","correspondingAuthor":false,"prefix":"","firstName":"Aimilia","middleName":"","lastName":"Theodorakioglou","suffix":""},{"id":533490971,"identity":"1a369e38-e12d-4ace-b9cc-ecac96bfc69b","order_by":2,"name":"Seyed Mehdi Sadat","email":"","orcid":"","institution":"Charles University","correspondingAuthor":false,"prefix":"","firstName":"Seyed","middleName":"Mehdi","lastName":"Sadat","suffix":""},{"id":533490972,"identity":"65aa521d-e09f-47b8-b4f5-b4b8059dee8c","order_by":3,"name":"Petra Kriskova","email":"","orcid":"","institution":"Charles University","correspondingAuthor":false,"prefix":"","firstName":"Petra","middleName":"","lastName":"Kriskova","suffix":""},{"id":533490973,"identity":"343d0f0a-0701-4b0a-aa95-4954bf597f33","order_by":4,"name":"Pilar Dominguez R Fonte","email":"","orcid":"","institution":"Independent Researcher","correspondingAuthor":false,"prefix":"","firstName":"Pilar","middleName":"Dominguez R","lastName":"Fonte","suffix":""},{"id":533490974,"identity":"c3a104ff-0700-4fda-82f1-4b831d4b2f89","order_by":5,"name":"Deeksha Shailesh","email":"","orcid":"","institution":"Independent Researcher","correspondingAuthor":false,"prefix":"","firstName":"Deeksha","middleName":"","lastName":"Shailesh","suffix":""},{"id":533490975,"identity":"eaac50f8-5583-4cc9-b09b-623e3cf216a3","order_by":6,"name":"Shayan Ghezel Bash","email":"","orcid":"","institution":"Independent Researcher","correspondingAuthor":false,"prefix":"","firstName":"Shayan","middleName":"Ghezel","lastName":"Bash","suffix":""}],"badges":[],"createdAt":"2025-10-08 13:08:43","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7808265/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7808265/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00276-026-03840-y","type":"published","date":"2026-02-27T15:59:52+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":94207792,"identity":"1245d077-aad6-4071-a4f5-1815b9f41942","added_by":"auto","created_at":"2025-10-23 15:01:40","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":27296949,"visible":true,"origin":"","legend":"\u003cp\u003eCadaveric dissection of the suprascapular notch topography (left shoulder, female formalin-fixed cadaver).\u003c/p\u003e\n\u003cp\u003eA) Clavipectoral triangle containing the suprascapular notch. B) Suprascapular notch. C) Coracoid process. D) Suprascapular notch boundaries and contents.\u003c/p\u003e\n\u003cp\u003eLegend: SSN – suprascapular notch, SSL – suprascapular ligament, SN – suprascapular nerve, SA - suprascapular artery, SV – suprascapular vein, SUP – supraspinatus muscle, SUB – subscapularis muscle, OM – omohyoid muscle, CP – coracoid process.\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-7808265/v1/d533e76462a3dd397cf367ba.png"},{"id":94207798,"identity":"75e1d260-5d13-4c78-bc67-961dff131be0","added_by":"auto","created_at":"2025-10-23 15:01:41","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":27321752,"visible":true,"origin":"","legend":"\u003cp\u003eCadaveric dissection of the suprascapular canal topography illustrating the “Tunnel-Insertion” surgical approach (right shoulder, female formalin-fixed cadaver).\u003c/p\u003e\n\u003cp\u003eA) Needle rod “Tunnel-Insertion” through the spinoglenoid notch – dorsal body view. B) Needle rod “Tunnel-Insertion” through the spinoglenoid and suprascapular notches – superior body view. C) Suprascapular canal topography within the supraspinous fossa. D) Suprascapular canal boundaries and contents.\u003c/p\u003e\n\u003cp\u003eLegend: SSN – suprascapular notch, SSL – suprascapular ligament, SGN – spinoglenoid notch, SN – suprascapular nerve, SV – suprascapular vessel, SPN – spine of scapula, CP – coracoid process.\u003c/p\u003e\n\u003cp\u003eS – superior, I – inferior, A – anterior, P – posterior, L – lateral, M – medial.\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-7808265/v1/24222235d52f75c061928a67.png"},{"id":94207791,"identity":"6387bb74-5812-406e-8aec-e4b9b527cb7e","added_by":"auto","created_at":"2025-10-23 15:01:40","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":14363700,"visible":true,"origin":"","legend":"\u003cp\u003e“Tunnel-Insertion” guided cadaveric sonography of the suprascapular canal (right shoulder, male fresh-frozen cadaver, 24 MHz Ultra-High Frequency iDMS Linear transducer (i24LX8)).\u003c/p\u003e\n\u003cp\u003eA) Needle rod “Tunnel-Insertion” through the spinoglenoid notch. B) “Tunnel-Insertion” through the suprascapular notch – dorsal body view. C) Ultrasound probe placement – under the clavicle with the receding edge over the coracoid process. D) Sonogram of the spinoglenoid notch short-axis view prior to the “Tunnel-Insertion”. E) Sonogram of an anterior projection of the suprascapular notch long-axis view showing the inserted needle rod. F) Needle rod ultrasound-guided visualization of the suprascapular canal. G) Sonographic confirmation of the suprascapular canal openings (spinoglenoid and suprascapular notches).\u003c/p\u003e\n\u003cp\u003eLegend: SSN – suprascapular notch, SGN – spinoglenoid notch, SSC – suprascapular canal, SUP – supraspinatus muscle, SPN – spine of scapula, CP – coracoid process, CL – clavicle, GL - glenoid.\u003c/p\u003e\n\u003cp\u003eA – anterior, P – posterior, L – lateral, M – medial.\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-7808265/v1/3be370ffe63c0c0e4beb7a39.png"},{"id":94208997,"identity":"4ab1a5e4-5f85-4347-b192-dda71580d42f","added_by":"auto","created_at":"2025-10-23 15:09:40","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":12768446,"visible":true,"origin":"","legend":"\u003cp\u003eSonogram of the suprascapular canal long-axis view (left shoulder, sagittal-oblique transducer placement).\u003c/p\u003e\n\u003cp\u003eA) Suprascapular canal sonogram – Subject 1 Female (24 MHz Ultra-High Frequency iDMS Linear transducer (i24LX8)). B) Dry bone scapula for orientation. C) Surface anatomy with ultrasound-probe orientation. D) Suprascapular canal sonogram – Subject 1 Male (11 MHz Vascular Linear iDMS transducer (i11LX3)). E) Suprascapular canal Doppler sonogram – Subject 1 Female (11 MHz Vascular Linear iDMS transducer (i11LX3)).\u003c/p\u003e\n\u003cp\u003eLegend: SSC – suprascapular canal, SSN – suprascapular notch, SGN – spinoglenoid notch, SUP – supraspinatus muscle (CT – supraspinatus central tendon, SUPf, supraspinatus fascia, at – anterior portion of the supraspinatus muscle, pt – posterior portion of the supraspinatus muscle), CP – coracoid process, SPN – spine of scapula, TRP – trapezius muscle, SF – spinoglenoid fossa, CL – clavicle, ACR – acromion, GL - glenoid.\u003c/p\u003e\n\u003cp\u003eLD – transducer leading edge, A – anterior, P – posterior, L – lateral, M – medial.\u003c/p\u003e","description":"","filename":"Figure4.png","url":"https://assets-eu.researchsquare.com/files/rs-7808265/v1/e5469322c09a9af833aa1a26.png"},{"id":94207796,"identity":"cef8c8ce-4f16-46d0-a900-91f226f4e74c","added_by":"auto","created_at":"2025-10-23 15:01:40","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":12131187,"visible":true,"origin":"","legend":"\u003cp\u003eSonogram of a posterior projection of the suprascapular notch long-axis view (right shoulder, superio-posterior transducer placement).\u003c/p\u003e\n\u003cp\u003eA) Suprascapular notch sonogram – Subject 1 Female (24 MHz Ultra-High Frequency iDMS Linear transducer (i24LX8)). B) Dry bone scapula for orientation. C) Surface anatomy with ultrasound-probe orientation. D) Suprascapular notch sonogram – Subject 1 Male (11 MHz Vascular Linear iDMS transducer (i11LX3)). E) Suprascapular canal Doppler sonogram – Subject 1 Female (11 MHz Vascular Linear iDMS transducer (i11LX3)).\u003c/p\u003e\n\u003cp\u003eLegend: SSN – suprascapular notch, SSL – suprascapular ligament, SN – suprascapular nerve, SUP – supraspinatus muscle, CP – coracoid process, TRP – trapezius muscle, CL – clavicle, ACR – acromion.\u003c/p\u003e\n\u003cp\u003eLD – transducer leading edge, L – lateral, M – medial.\u003c/p\u003e","description":"","filename":"Figure5.png","url":"https://assets-eu.researchsquare.com/files/rs-7808265/v1/57675b5a181b18829d366e71.png"},{"id":94207797,"identity":"f9c502b4-fb57-4d45-a8f2-174cafe4ddb2","added_by":"auto","created_at":"2025-10-23 15:01:40","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":11131609,"visible":true,"origin":"","legend":"\u003cp\u003eSonogram of an anterior projection of the suprascapular notch long-axis view (right shoulder, anterior transducer placement).\u003c/p\u003e\n\u003cp\u003eA) Suprascapular notch sonogram – Subject 1 Female (24 MHz Ultra-High Frequency iDMS Linear (i24LX8)). B) Dry bone scapula for orientation. C) Surface anatomy with ultrasound-probe orientation. D) Suprascapular notch sonogram – Subject 1 Male (11 MHz Vascular Linear iDMS transducer (i11LX3)). E) Suprascapular canal Doppler sonogram – Subject 1 Female (11 MHz Vascular Linear iDMS transducer (i11LX3)).\u003c/p\u003e\n\u003cp\u003eLegend: SSN – suprascapular notch, SSL – suprascapular ligament, SN – suprascapular nerve, SUP – supraspinatus muscle, SUB – subscapularis muscle (CT – supraspinatus central tendon), OM – omohyoid muscle, CP – coracoid process, CL – clavicle, ACR – acromion, SCV – subclavian vein.\u003c/p\u003e\n\u003cp\u003eLD – transducer leading edge, L – lateral, M – medial.\u003c/p\u003e","description":"","filename":"Figure6.png","url":"https://assets-eu.researchsquare.com/files/rs-7808265/v1/d53d095823e66f608a2014d0.png"},{"id":94207799,"identity":"d836fbdc-cd7a-4681-8ebe-33e7571752d2","added_by":"auto","created_at":"2025-10-23 15:01:41","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":25546431,"visible":true,"origin":"","legend":"\u003cp\u003eSonogram series of the suprascapular canal long-axis view illustrating its sonographic visibility by sex, BMI, and shoulder thickness (24 MHz Ultra-High Frequency iDMS Linear (i24LX8), sagittal-oblique transducer placement).\u003c/p\u003e\n\u003cp\u003eA) Subject 2 Female. B) Subject 3 Female. C) Subject 4 Female. D) Subject 5 Female with poor sonographic visibility. E) Subject 2 Male. F) Subject 3 Male. G) Subject 4 Male with poor sonographic visibility. H) Subject 5 Male with poor sonographic visibility.\u003c/p\u003e\n\u003cp\u003eLegend: SSC – suprascapular canal, SSN – suprascapular notch, SGN – spinoglenoid notch, SUP – supraspinatus muscle.\u003c/p\u003e","description":"","filename":"Figure7.png","url":"https://assets-eu.researchsquare.com/files/rs-7808265/v1/0e0cb4c43ece062198f4d3fe.png"},{"id":94207804,"identity":"316c62c0-fc9c-4722-b2c6-273321f1513d","added_by":"auto","created_at":"2025-10-23 15:01:41","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":23064173,"visible":true,"origin":"","legend":"\u003cp\u003eSonogram series of the posterior projection of the suprascapular notch long-axis view illustrating its sonographic visibility by sex, BMI, and shoulder thickness (24 MHz Ultra-High Frequency iDMS Linear (i24LX8), superio-posterior transducer placement).\u003c/p\u003e\n\u003cp\u003eA) Subject 2 Female. B) Subject 3 Female. C) Subject 4 Female. D) Subject 5 Female. E) Subject 2 Male. F) Subject 3 Male. G) Subject 4 Male with poor sonographic visibility. H) Subject 5 Male with poor sonographic visibility.\u003c/p\u003e\n\u003cp\u003eLegend: SSN – suprascapular notch, CP – coracoid process.\u003c/p\u003e","description":"","filename":"Figure8.png","url":"https://assets-eu.researchsquare.com/files/rs-7808265/v1/1a18fe769ea6ca3684b536e5.png"},{"id":94207803,"identity":"d0d0e938-8233-43aa-b1e4-248132831778","added_by":"auto","created_at":"2025-10-23 15:01:41","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":30322325,"visible":true,"origin":"","legend":"\u003cp\u003eSonogram series of the anterior projection of the suprascapular notch long-axis view illustrating its sonographic visibility by sex, BMI, and shoulder thickness (24 MHz Ultra-High Frequency iDMS Linear (i24LX8), anterior transducer placement).\u003c/p\u003e\n\u003cp\u003eA) Subject 2 Female. B) Subject 3 Female. C) Subject 4 Female with less sonographic visibility. D) Subject 5 Female. E) Subject 2 Male. F) Subject 3 Male. G) Subject 4 Male. H) Subject 5 Male with less sonographic visibility.\u003c/p\u003e\n\u003cp\u003eLegend: SSN – suprascapular notch, CP – coracoid process.\u003c/p\u003e","description":"","filename":"Figure9.png","url":"https://assets-eu.researchsquare.com/files/rs-7808265/v1/cc46922678bfbe1eaf4e1829.png"},{"id":94207802,"identity":"23025b09-be50-43c8-907c-76957e9887f7","added_by":"auto","created_at":"2025-10-23 15:01:41","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":1662026,"visible":true,"origin":"","legend":"\u003cp\u003eShoulder thickness depicting the depth of the examined structures from the body surface.\u003c/p\u003e\n\u003cp\u003eLegend: SSC – suprascapular canal, SSN – suprascapular notch, SGN – spinoglenoid notch, SUP – supraspinatus muscle CP – coracoid process, SPN – spine of scapula.\u003c/p\u003e","description":"","filename":"Figure10.png","url":"https://assets-eu.researchsquare.com/files/rs-7808265/v1/1f435ebf0cfb26779edd102b.png"},{"id":103765725,"identity":"6b225e83-8cb5-459a-a154-3fa04b8d2860","added_by":"auto","created_at":"2026-03-02 16:08:18","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":155279277,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7808265/v1/192fa5ea-f717-4f42-9577-725a851ca42a.pdf"},{"id":94207790,"identity":"9c48343f-360b-4559-a221-52cd44013dad","added_by":"auto","created_at":"2025-10-23 15:01:40","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":17661,"visible":true,"origin":"","legend":"","description":"","filename":"Table1.docx","url":"https://assets-eu.researchsquare.com/files/rs-7808265/v1/5e1c3e5f688b0b5492a1a119.docx"},{"id":94207801,"identity":"4b06bf5b-ab07-4cab-af16-4b55784d4ec9","added_by":"auto","created_at":"2025-10-23 15:01:41","extension":"mov","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":12512382,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eVideo 1\u003c/strong\u003e. Sonography of the suprascapular canal long-axis view (left shoulder, in sagittal-oblique plane transducer manipulation).\u003c/p\u003e\n\u003cp\u003eLegend: SSC – suprascapular canal, SSN – suprascapular notch, SGN – spinoglenoid notch, SUP – supraspinatus muscle (CT – supraspinatus central tendon, SUPf, supraspinatus fascia, at – anterior portion of the supraspinatus muscle, pt – posterior portion of the supraspinatus muscle), CL – clavicle, CP – coracoid process, SPN – spine of scapula, TRP – trapezius muscle.\u003c/p\u003e\n\u003cp\u003eLD – transducer leading edge.\u003c/p\u003e","description":"","filename":"Video1.mov","url":"https://assets-eu.researchsquare.com/files/rs-7808265/v1/f68c246d4043e90829666333.mov"},{"id":94208998,"identity":"6fa1cbc1-c1bc-4436-931c-58aac41d3bb4","added_by":"auto","created_at":"2025-10-23 15:09:40","extension":"mov","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":6850130,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eVideo 2\u003c/strong\u003e. Sonography posterior projection of the suprascapular notch long-axis view (right shoulder superio-posterior transducer placement with coronal plane transducer manipulation).\u003c/p\u003e\n\u003cp\u003eLegend: SSN – suprascapular notch, SSL – suprascapular ligament, SSC – suprascapular canal, SUP – supraspinatus muscle, CP – coracoid process, TRP – trapezius muscle.\u003c/p\u003e\n\u003cp\u003eLD – transducer leading edge.\u003c/p\u003e","description":"","filename":"Video2.mov","url":"https://assets-eu.researchsquare.com/files/rs-7808265/v1/d194f90f4fde79e2fe47f7a9.mov"},{"id":94207794,"identity":"989065c1-2eb6-4250-bfbb-c77ed2bcc3e9","added_by":"auto","created_at":"2025-10-23 15:01:40","extension":"mov","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":8177404,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eVideo 3\u003c/strong\u003e. Sonography anterior projection of the suprascapular notch long-axis view (right shoulder, anterior transducer placement with transverse plane transducer manipulation).\u003c/p\u003e\n\u003cp\u003eLegend: SSN – suprascapular notch, SSL – suprascapular ligament, SN – suprascapular nerve, SUP – supraspinatus muscle, SUB – subscapularis muscle, OM – omohyoid muscle, CP – coracoid process, Sv – suprascapular vessels.\u003c/p\u003e\n\u003cp\u003eLD – transducer leading edge.\u003c/p\u003e","description":"","filename":"Video3.mov","url":"https://assets-eu.researchsquare.com/files/rs-7808265/v1/8a734e5b2e34f85ae51baf46.mov"}],"financialInterests":"No competing interests reported.","formattedTitle":"Sonographic Visualization of the Suprascapular Canal with Focus on the Suprascapular Notch: Anatomical Description and Ultrasound-Probe Techniques","fulltext":[{"header":"Background ","content":"\u003cp\u003eUltrasound-guided suprascapular nerve (SN) block is a common clinical procedure to relieve shoulder pain caused by SN entrapment syndromes [13–17, 19]. The ultrasound-guided approach is also applied in radiofrequency treatments [27]. Needle aspiration of ganglionic cystic in the SN is also performed with ultrasound guidance [19, 28]. In addition, it was proposed to utilize ultrasound-aided arthroscopic insertion during SN surgical decompression procedures [19]. In regard to diagnostic imaging modalities of SN entrapments, MRI does not yield optimal real-time images of the suprascapular notch (SSN) anatomy [4]. Ultrasonography became an emerging modality in the diagnostics of SN entrapments. However, sonography of the SSN is rather challenging [12, 14, 28] and requires skills and modification to its approach [14].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eObstacles in Sonographic Visualization of the Suprascapular Notch\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eEven though sonographic examination gives advantage of ultrasound-probe (probe) manual handling that aligns the ultrasound transducer beam through the SSN vicinity, it still carries its own obstacles. Observer skills and experience with a learning curve are required to reach adequate sonograms [9]. The variability of the SSN morphology adds more challenge and uncertainties to its visualization [2, 12, 30]. Furthermore, doubts of the ultrasonic evaluation accuracy of the SSN has been addressed in the literature [14].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eThe Current State of the Art\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA sagittal-oblique sonographic cross-section through the long-axis of the suprascapular canal (SSC) is known and practiced in some clinical settings but still not documented in the literature. The SSC as a topographical space with comprehensive anatomical description is relatively recent in the literature and was published in a previous study [2]. Therefore, we believe to our best knowledge that this article provides a new insight into the sonographic anatomy of the whole extent of the SSC in the aforementioned cross-sectional orientation. \u0026nbsp; \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSonography of the SSN in the clinical practice have been performed only from a superior shoulder approach projecting a posterior coronal long-axis view of the SSN and is a routine clinical practice [12–17, 19, 21, 27, 30]. A four-step protocol to enhance the sonographic visibility of the SSN different morphological types was presented in the literature by Jezierski et al. in 2018 [12] projecting a posterior sonographic view of the SSN long-axis with focus on the suprascapular vessels ultrasound Doppler detection. In their protocol, the probe was aligned along the SSN short-axis in a sagittal plane and then rotated toward the SSN long-axis in a coronal plane, followed by sliding the probe forward and tilting until reaching a perpendicular plane view of the superior margin of the scapula. Their final step was dedicated to ultrasonic Doppler detection of the suprascapular vessels [12]. However, some images encountered in the literature designated the short-axis passage site of the SSC [2] as the SSN [4].\u003c/p\u003e\n\u003cp\u003eUltrasonographic anterior approach to the SSN has not yet presented in the clinical practice and has been believed not to be possible. What is referred to throughout the literature as an anterior ultrasound approach [26, 29] is in fact a distal targeting of the SN above the clavicle at the site where the brachial plexus passes through the scalene fissure. The anterior approach below the clavicle visualizing the SSN anterior vicinity was not presented before, to our current best knowledge of the available literature.\u003c/p\u003e\n\u003cp\u003eOn the contrary, the spinoglenoid notch (SGN) can be visualized with ease by ultrasonography [28]. Therefore, it was not focused on in this article and was addressed as a part of the SSC only. The SGN is not situated as deep as the SSN [2] and is not masked by other surrounding sonographic structures [28]. It is captured on the ultrasound screen by placing the probe under the spine of the scapula (SPN) while sliding laterally with less required probe manipulation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAims and Goals of the Proposed Sonographic Approach\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eHereby, we provide anatomic based probe manipulation techniques to capture optimal angle of insonations exposing the SSC topography and its key sonographic structures. Surface anatomy of palpable landmark structures is emphasized for more practical probe placement and manipulation. As a main focus, we provide a four stepwise shoulder and probe maneuver yielding a novel anterior sonographic view of the SSN.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eThe Experimental Design\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eExperimental Approach,\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe experimented scanning the superior and anterior area of the shoulder at differing angles with probe explorative manipulations. Different shoulder maneuvers were attempted in seated and lying positions. The selected experimented maneuvers were in attempts to move away the sonographic masking structures (clavicle mainly, and subscapularis muscle) that were preventing the projection of the ultrasound transducer to our target of interest, the SSN. The below described protocol was constructed after reaching optimal sonograms. The protocol was tested and verified experimentally on a fresh frozen cadaver as described below. Afterward, the sonographic examination was performed on all the ten volunteers by the main observer followed by the other five observers under the main observer guidance.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eStudy Subjects\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSonography of the superior shoulder region was bilaterally experimented on ten young healthy (five females and five males) volunteers of age ±23, with prior written consent. The BMI, shoulder thickness in addition to age and sex was recorded (Table 1). BMIs were obtained by BMI scales accessed via local fitness center facilities. The shoulder thickness was measured by a digital \u003cem\u003eVernier\u003c/em\u003e thickness caliper in two planes: 1) Vertical plane – by placing one end over the acromion and the other end under the axilla (arm in an abducted position), 2) Horizontal plane – by placing one on the base of the coracoid process (CP) and the second end under the SPN (arm in the natural anatomical position). The used ultrasound device was CANON APLIO i800 with Aplio's i-series 24 MHz Ultra-High Frequency iDMS Linear (i24LX8) and i-series 11 MHz Vascular Linear iDMS (i11LX3) transducers.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eCadaveric Specimens for Experiment Testing and Illustration\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe SSC anatomy focused on illustrating the SSN topography was dissected on a 60+ years old female formalin-fixed cadaver. In addition, the gross anatomy as well as the sonographic anatomy was verified and illustrated on a 60+ years old male fresh frozen cadaveric specimen. Both cadavers belong to the body donor program for research and education purposes administered by the Department of Anatomy, Second Faculty of Medicine, Charles University where the research was conducted.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eEthical Approval of Cadaveric Access and Volunteers Consent\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. The study and volunteers consent procedure was approved for research and education purposes by the Institutional Review Board (IRB) – The Ethics Committee of the University Hospital Motol and Second Faculty of Medicine, Charles University, Prague, Czech Republic [Reference ID no. EK-353/19] and [Reference ID no. EK-1175.1.23/22]. Access to cadavers are under the local corps donor program in adherence to the Czech Anatomical Society and European Union ethical, legal regulation and provision in accordance with Act Code No. 89/2012 Sb. of the Civil Code and Act Code No. 372/2011 Sb. on Article 7 of the Health Services amended provision. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSuprascapular Canal Cadaveric Dissection Illustration and\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eSonographic Approach\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe SSN is impended deep in the corner of the clavipectoral triangle (also known as the deltopectoral triangle) bordered by the clavicle superiorly, by the pectoralis major muscle inferiorly, and by the deltoid muscle laterally (Figure 1). This triangle forms a sonographic window for the probe placement as described below. Through this window the anterior vicinity of the SSN can be visualized. The SSN is bordered by the suprascapular ligament (SSL) in 93% of the cases [3] in approximately 7% is an enclosed by bone foramen variant of SSN [3]. Above the SSL is a musculofibrous opening bordered by the supraspinatus muscle (SUP) where pass the suprascapular vessels (SV) in majority of the cases [2]. The subscapularis muscle (SUB) run anteriorly below the SSN vicinity. The base of the CP forms the lateral border of the SSN, where it can be utilized as anatomical landmark in localizing the SSN (Figure 1C). The medial border of the SSN is formed by the medial peak of the SSN where the omohyoid muscle (OM) inserts (Figure 1D) with variability of its attachment onto the SSL medial portion [1].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eSuprascapular Canal Cadaveric Anatomy Illustration\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA “Tunnel-Insertion” approach was performed by inserting a needle rod through the SGN by palpating its corner under the SPN as a blind non-imaging guidance (Figure 2A). The needle rod was navigated against the supraspinous fossa bone surface to exit through the SSN and proceeding it out of the cadaveric body under the clavicle (Figure 2B). A block incision resection through the SUP was made to expose the full length and orientation of the SSC (Figure 2C). The SSC run in an oblique direction connecting its two openings between the SGN and the SSN [2] (Figure 2D). The suprascapular space bounded by the SPN, acromion and clavicle serves landmarks to the imaging window of the SSC. \u0026nbsp; \u0026nbsp; \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eSuprascapular Canal Cadaveric Sonographic Approach\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA second “Tunnel-Insertion” approach was performed on a fresh-frozen cadaveric body donor (Figure 3). The needle rod insertion was done under ultrasound guidance. The SGN was localized sonographically prior to the needle rod insertion (Figure 3D) and navigated through the SSC under ultrasound guidance (Figure 3F). The SSN long-axis view in an anterior projection was verified by visualizing the passing through needle rod on the sonogram (Figure 3E). This confirms the anatomic accuracy of obtained SSC sonogram (Figure 3G). The anechoic CP and the anechoic medial peak of the SSN with hyperechoic margin forms the sonographic landmarks of the SSN long-axis view in the anterior projection. The CP is localized under the clavicle in the SSC long-axis sagittal-oblique view indicating the location of the SSN, where the SPN indicates the location of the SGN (Figure 3). Further sonographic anatomy is described below in details in its corresponding subsections. \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSuprascapular Canal\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eSonography technique and Anatomy\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eI.\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eSonography of the Suprascapular Canal Long-Axis View – Sagittal-Oblique Projection\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe sonographic anatomy of the SSC long-axis view and its probe placement and manipulation are illustrated in Figure 4 and in Video 1.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eThe Sonographic Anatomy\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe long-axis of the SSC was captured in a sagittal-oblique cross-sectional plane extending throughout its full length from the SSN to the SGN (Figure 4). The SSC resides underneath the SUP (hypoechoic with striations of a typical\u0026nbsp;sonographic muscle appearance [11] with a hyperechoic central tendon running between its hypoechoic anterior and posterior portions [22] as shown in Figure 4A) in the spinoglenoid fossa [2] with an entrance site through the SSN (hyperechoic on the right side of the ultrasound screen) which is seen adjacent to the base of the CP (anechoic with a hyperechoic bright rim demarcating its surface of a typical sonographic bone appearance) [11] (Figure 4A, 4D). However, the medial border of the SSN does not fall into view and lies medially to the ultrasound beam and do not align within the angle of insonation [5]. The SSL does not align with the angle of insonation and therefore is not visible. At the receding end, the SGN is visible on the left side of the ultrasound screen with a hypoechoic sonographic feature (Figure 4A, 4D). The orientation of the SGN gives it a better dimensional visibility advantage than the SSN. The angle of insonation falls perpendicular to the SGN vicinity with a better ultrasound reflection. The spinoglenoid ligament appears less echoic than the SSL due to its morphological nature of a thin membrane extending from the SUP fascia [2]. The bony margins of the SGN at its floor are formed by the infraspinous fossa margin and its medial border by the acromiospinal arch [2] and both are well visible with anechoic lined with hyperechoic bright rim sonographic appearance (Figure 4A, 4D). The neurovascular bundle is visible as a hyperechoic band running through the full length of the SSC between the SSN and the SGN (Figure 4A, 4D). Its visibility was enhanced by the below described shoulder maneuver (Video 1). This maneuver allows examining the muscle contraction dynamic effect on the underlying SSC space and its neurovascular bundle content. Figure 4E shows the passing SV through the SSN into the SSC by ultrasound Doppler detection.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003ePatient Positioning\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe examination should be performed in a seated position with a low supporting backrest.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eThe Ultrasound-Probe Manipulation and Surface Anatomical Landmarks\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe probe was placed above the spinoglenoid fossa [2] which is localized by the palpable acromion and SPN as its surface anatomical boundary landmarks (Figure 4B, 4C). The probe is oriented in a sagittal-oblique plane where the probe receding edge is compressed [5] against the palpable medial angle between the SPN and the acromion (Figure 4C). Meanwhile, the probe leading edge placement is maintained as far as possible from the clavicle. This allows for free probe sliding and rotation [5] above the SUP. The probe is then tilted laterally in approximately 10° degrees where the probe beam projects medially, this will adjust the angle of insonation (Figure 4C). Final adjustment is obtained by slightly sliding and sweeping [5] the probe with counterclockwise and clockwise probe rotation until the SSN on one end and the SGN on the other end are aligned on the ultrasound screen (Video 1).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eThe Maneuver\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAn arm abduction up to 45° degrees, controlled by the observer, lifts the SUP cranially stretching the SSC passage site [2] for better visibility of the underneath passing neurovascular bundle (Video 1).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe sonogram is considered optimal when both openings of the SSC (SSN and SGN) are simultaneously visible on the ultrasound screen and the suprascapular neurovascular bundle is visibly coursing between the SSN and the SGN (Figure 4). \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eII. Sonography of the Suprascapular Notch Long-Axis View – Posterior Projection\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe sonographic anatomy of this SSN long-axis view and its probe placement and manipulation are illustrated in Figure 5 and in Video 2.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eThe Sonographic Anatomy\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe SSN is located anterior to the SSC and its long-axis anatomically oriented with a medial-inferior tilt in relation to the body plane [2]. The base of the CP appears anechoic with a hyperechoic bright line surface [11], and it forms the lateral border of the SSN [2] (Figure 5). The inferior margin of the SSN should appear as a hypoechoic curved margin (Figure 5A, 5D) and will appear slightly echoic if the SUP gets captured in the angle of insonation. In case the inferior margin is not captured, a slight probe pressure with tilt manipulation [5] is necessary to project a well-defined inferior margin of the SSN into the angle of insonation. The superior border of the scapula will appear as a demarcated anechoic margin below the largely visible hypoechoic trapezius muscle. Partial muscle fibers of the SUP may appear as hypoechoic bands on the medial side of the ultrasound screen (Figure 5A, 5D). The SSL long-axis appears as a hyperechoic shinning-white band extending between the base of the CP and the medial peak of the SSN. The SSN has a heterogeneous hyperechoic with anechoic dots sonographic appearance as it is occupied by adipose and loose connective tissue\u0026nbsp;[11]. A cross-section of the SN short-axis is visible resembling a honeycomb shape-like structure (a typical sonographic feature of distally located nerves) [11], where its fascicles appear hypoechoic on a hyperechoic background (Figure 5A, 5D). The passing SV at the SSN can be detected by ultrasound Doppler with low sensitivity by the 11 MHz Linear transducers (Figure 5E).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003ePatient Positioning\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe examination should be performed in a seated position with a low supporting backrest.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eThe Ultrasound-Probe Manipulation and Surface Anatomical Landmarks\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe probe is placed parallel to the palpable SPN in a coronal-oblique plane to the body above the supraspinous fossa. The probe leading edge (or the receding edge according to personal preference) is placed with pressure and rocking manipulation [5] by the medial landmark surface of the acromioclavicular joint, where the articulating ends of the acromion and the clavicle are palpable (Figure 5C). The probe is then swept [5] in an anterior direction with a slight rotation (clockwise when scanning the right shoulder; counterclockwise when scanning the left shoulder) until the SSC short-axis view is projected corresponding to its anatomical oblique-transverse cross-section. After this point, the probe is manipulated by sliding and tilting maneuvers over the SSC short-axis towards the SSN until the base of the CP is visible and the attachment of the SSL at this site projects on the monitor (Figure 5C). The SSN is now located (Video 2). To adjust the angle of insonation, the probe receding edge is manipulated in explorative tilt, rocking, and pressure maneuvers [5] (while keeping the lateral side of the SSN visible on the monitor to not lose this anatomical landmark of its lateral boundary) until the full length of the SSL long-axis is visible (if possible, limitations described below) and its medial attachment onto the medial peak of the SSN appears on the screen (Figure 5A), (Video 2). Consequently, the ultrasonic probe beam will be perpendicular to the SSN long-axis where the probe beam projects in an antero-infero-medial direction to the body plane.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eThe Maneuver\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo shoulder maneuver was necessary for this ultrasonographic projection.\u003c/p\u003e\n\u003cp\u003eThe sonogram is considered optimal when the SSL full extent is visible and the bony margins of the SSN are detectable (Figure 5A). A point of caution is when the SSL is not projected on the screen, it most probably indicates that the captured image is a transverse cross-section through the SSC (sonographic short-axis) and probably not the SSN [4]. In this case, further adjustment is needed by probe fan and sweep [5] manipulation (further limitations is described below).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eIII.\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eSonography of the Suprascapular Notch Long-Axis View – Anterior Projection\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe sonographic anatomy of this SSN long-axis view and its probe placement and manipulation are illustrated in Figure 6 and in Video 3.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eThe Sonographic Anatomy\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe topography of the SSN in this angle of insonation appears in much more detail [2] than in the aforementioned insonation angles. In addition to the SUP, the OM and the SUB are also visible (Figure 6). Unlike in the other angles of insonations, the CP appears as a whole and not just its base. The CP did not appear homogenous in its echogenicity as in the other sonographic views. The base of the CP forms the lateral border of the SSN long-axis and appears anechoic [11] with not well defined hyperechoic margin. The apex and body of the CP appear isoechoic due to the attaching muscles and ligaments (Figure 6A, 6D). The SUB appears more visible at first and its superior margin moves caudally as the maneuver (described below) is performed. It will then have a less hypoechoic appearance as it gets stretched and shifts downward (Video 3). This will unmask the SSN making it appear on the monitor with a relatively hyperechoic vicinity surrounded medially, laterally and inferiorly by a demarcated slightly hypoechoic margins (Figure 6A, 6D). The medial peak of the SSN is confirmed by a slow head and neck rotation to the opposite side causing the OM to be visibly stretching on the ultrasound monitor (Video 3). This enhances its visibility as its short-axis aligns into the angle of insonation [5] and appears hypoechoic with striations, a typical sonographic feature of a muscle [11] (Figure 6A, 6D). The superior boundary of the SSN is formed by the SSL and its long-axis (when visible, further limitations described below) appears hyperechoic as a shining white band running underneath and in a parallel direction to the inferior margin of the hypoechoic SUP. The full extent of the SSL is visible coursing between its two attachment sites, laterally the base of the CP (anechoic) and medially the medial peak of the SSN (hypoechoic due to the inserting OM fibers). The musculofibrous space between the SSL and the SUP may be visible as well with a heterogeneous hyperechoic sonographic appearance due to its occupying adipose and loose connective tissue (Figure 6A). The SN appeared (with poor visibility) hypoechoic, a typical sonographic feature of a proximally located nerve [11]. Nevertheless, the SN exhibited anisotropic feature as its short-axis lies oblique to the angle of insonation [5, 11]. The SN courses in a curved direction at this anatomical site as it passes from the omoclavicular triangle entering into the SSN [2]. Therefore, its short-axis do not align with the long-axis of the SSN vicinity. In addition, the echogenicity of the SN was of a relatively similar intensity to the SSN vicinity echogenicity in this specific angle of insonation targeting the long-axis of the SSN (Figure 6A, 6D). However, a slight arm maneuver in any possible direction (addiction, abduction, extension, flexion, internal and external rotation) had stretched the SN making it visible to detect as it wiggled on the ultrasound screen (Video 3). Regardless its less defined sonographic appearance [5, 11], this angle of insonation gave the advantage of examining the structural dynamic relationship between the SN and the surrounding sonographic structures at the anterior vicinity of the SSN. In addition, Figure 6E shows the passing SV at the SSN (above the SSL) by ultrasound Doppler detection.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003ePatient Positioning\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe examination should be performed in a lying supine position on a bed with no arm support to assure suitable degrees of freedom to perform the below described arm maneuver.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eThe Ultrasound-Probe Manipulation and Surface Anatomical Landmarks\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe probe receding edge (or the leading edge if different screen projection is preferred) is placed under the clavicle over the palpable CP with an approximately 10° degrees’ cranial tilt (also designated as fan) [5] in which the probe beam projects caudally in approximately 10° degrees from the body transverse plane (Figure 6C) while performing the below stepwise maneuver (Video3). While performing the maneuver, the surrounding structures (SUP, SUB and OM) can be seen stretching on the screen enhancing the sonographic visibility of the SSN boundaries (Video3). The angle of insonation is adjusted by rocking, fanning, and slight rotations [5] the probe.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eThe Maneuver\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFour stepwise maneuvers while placing and manipulating the probe over the described anatomical landmarks (Figure 6), (Video 3):\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e1) The arm is abducted to approximately 45° degrees. This movement will contract and move the SUP lifting it cranially simultaneously with the clavicle.\u003c/p\u003e\n\u003cp\u003e2) The arm is rotated externally while the forearm is in a flexed position. This movement will cause the superior margin of the SUB to move caudally, further away from the SSN anterior vicinity.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e3) The receding edge (or leading edge according to personal preference) of the probe is then placed under the clavicle on the palpable CP followed by sliding the probe medially to place its receding edge over the base of the CP. The lateral border of the SSN in its long-axis view will be detectable on the ultrasound monitor.\u003c/p\u003e\n\u003cp\u003e4) A slow contralateral head and neck rotation to the opposite side will stretch the OM and will be seen in motion on the ultrasound screen medial to the site of the base of the CP. Also, an ipsilateral head and neck rotation will cause the OM to contract and be seen in motion on the screen. However, stretching the OM gave it better defined short-axis hypoechoic visibility than contracting it.\u003c/p\u003e\n\u003cp\u003eThe sonogram is considered optimal when the full extent of the SSL, i.e. from the base of the CP to the medial peak of the SSN, becomes visible and the inferior border of the SSN is simultaneously noticeable in addition to the visible OM and partial fibers of the superior margin of the SUB (Figure 6A).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFactors Affecting Sonographic Anatomical Visibility\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe visibility and its quality seemed to be not affected by the BMI directly but by the shoulder thickness. The closer the SSN to the cutaneous surface, the higher the resolution of the image. The penetration of the 24 MHz transducer ultrasound rays gives a good visibility of up to approximately 3.5 cm of sonographic depth. On the other hand, the 11 MHz ultrasound rays penetrates deeper into the body bringing the SSN in individuals with larger shoulder thickness into view but with less sonographic resolution compared to the 24 MHz transducer giving poor anatomical details. Ultrasound Doppler detection was not viable by the 24 MHz transducer and was only detected by the 11 MHz ultrasound.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eApart from sonographic factors, the anatomical orientation of the shoulder girdle bones plays critical role in the visibility of the SSN. The clavicle can mask the vicinity of the SSN and require further explorative probe orientation with arm maneuvers. The SSN varies in size and exhibit five distinctive types. One type has a wider width than its depth, other has shorter width than its depth, and sometimes has equal width to depth [3, 12]. Two challenging SSN types may be encountered. Those are the discrete type where the SSN is not prominent in appearance; and the SSN foramen variant where it lacks a SSL with an ossified superior border [3, 12] that can hinder the ultrasound beam projection.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp; \u0026nbsp; Figures 7, 8, and 9 illustrate a spectrum of sonographic visibility governed by three critical parameters as detailed below. It appears to yield higher visibility in females than in males. Lower BMI gave better visibility to some extend in terms of structural details. Shoulder thickness was the prominent parameter in the sonographic visibility yielding more visibility when the structures lay within a depth of less than 3.5 cm from the body surface.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eSonographic Visibility by Sex Anatomical Differences\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe shoulder joint stability and muscle dynamics power differs between the two sexes [6, 7, 24]. Females seems to have less muscle activation power at younger age according to some studies [6] while males tend to have more pectoralis major muscle stiffness [24]. The differences between the two sexes muscularity is observable and was reported in the literature [7]. Nevertheless, it is evidenced through cadaveric dissections as well as surface anatomy that the clavipectoral triangle (Figure 1) is wider in females than in males. This gives wider ultrasound access window into the SSN in the anterior view (Figure 6). On the other hand, males have a higher running superior margin of the pectoralis major muscle [23]. In addition, the trapezius muscle in males extends into larger insertion surface on the clavicle, acromion, and the SPN [25]. Similarly, the deltoid muscle in males occupies more surface at its origin (clavicle, acromion and SPN) [8, 20]. Consequently, the SUP in females tended to come into the sonographic view in the SSN anterior projection view with more ease (Figure 6A), while the pectoralis major and deltoid muscles tend to mask the SUP in males (Figure 6D).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn addition, the BMI and shoulder thickness range in our study subjects were smaller in females (Table 1) yielding higher rate of sonographic visibility (Figure 7, 8, 9). The BMI range in females was 17.1 kg/m2 to 26.4 kg/m2 (mean: 18.6 kg/m2); and 20.4 kg/m2 to 27.4 kg/m2 (mean: 23.8 kg/m2) in males. The shoulder thickness in females was as low as 5.1 cm (mean: horizontal – 7.45 cm; vertical – 7.85 cm) while not less than 8.0 cm (mean: horizontal – 8.85 cm; vertical – 9.15 cm) in males. These two factors added favorable anatomical reach to the targeted structures in terms of less mass and less depth for the penetrating ultrasound beam in females compared to males. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eSonographic Visibility by BMI Differences\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eObesity and muscle mass lower the sonographic visibility of the underlying in depth structures [18]. The sonographic visibility in our sample had diminished in individuals with BMIs \u0026gt; 24.0 kg/m2 prominently in the SSC long-axis view – sagittal-oblique projection (Figure 7) and in the SSN Long-axis view – posterior projection (Figure 8). However, the sonographic visibility was not diminished in the SSN long-axis view – anterior projection with relatively poor visibility in the individual with the highest BMI of \u0026gt; 27.0 kg/m2 (Figure 9).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eSonographic Visibility by Shoulder Thickness Differences\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe ultrasound waves have limited capacity in penetrating through the body tissues, and the high frequency transducers used in ultrasound examinations of the musculoskeletal regions have limited reach [10]. The anatomical depth of the SSN is greater when approaching the SSN via the posterior projection compared to the anterior projection (Figure 10), in which only one case showed poor visibility in the anterior projection (Figure 9) while two cases of no visibility in the posterior projection (Figure 8). The SGN is located deeper than the SSN in the sagittal-oblique projection (Figure 10), in which the SGN was not visible in three cases while the SSN was not visible only in two cases (Figure 7). The female shoulder vertical thickness in our sample ranged from 6.0 cm to 9.8 cm, and the horizontal thickness ranged from 5.1 cm to 8.7 cm. On the other hand, the male shoulder vertical thickness ranged from 8.0 cm to 9.4 cm, and the horizontal thickness ranged from 8.3 cm to 9.7 cm. In addition, the trapezius muscle is relatively thicker in mass in males which adds more ultrasound reach distance than the actual measured vertical thickness [25]. Consequently, the depth of the structures from the surface was less in female subjects yielding more ultrasound reach with higher sonographic visibility. \u0026nbsp; \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIt was evidenced that the structures located in a depth of up to 3.5 cm from the body surface yielded more sonographic visibility than the structures located at more than 3.5 cm in depth, with slight variability (Figure 7, 8, 9). The vertical shoulder thickness was an indicator of the sonographic visibility in the sagittal-oblique projection (Figure 7) and in the posterior projection (Figure 8); while the horizontal shoulder thickness was an indicator of the sonographic visibility in the anterior projection (Figure 9). According to the shoulder thickness measurements and the sonograms, the SSC is situated approximately in the center of the two thickness axes (Figure 10). The SSN is situated in the anterior 1/4th distance, which is closer in the anterior projection to the probe but farther form it in the posterior projection. The SGN is situated beyond the center point of the two thickness axes, which is farther from the probe in the posterior projection – sagittal-oblique view of the SSC (Figure 10).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTechnical Gains and Clinical Implication\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe combination of these three sonographic views gives comprehensive assessment of the SSC enhancing a non-invasive diagnostic approach to SN entrapment syndrome. The novel anterior SSN view along with the SSC sagittal-oblique view sonographic examinations allow evaluating the muscles dynamics and assessing their pathological involvement in a suspected SN entrapment syndrome. Furthermore, these multiple imaging-guided sites provide wider range of SN block accesses. The SN can be reached more proximally than the commonly accessed distal to the SSN approach [13–17, 19,\u0026nbsp;27]\u0026nbsp;in peripheral nerve pain management.\u003c/p\u003e\n\u003cp\u003eA practical point of view, the sonographic visibility of the SSC can be predicted by the two proposed shoulder thickness axes (Figure 10) adding into account the sex and body composition in terms of the patients BMI. This can be estimated by approximating the structures localization in centimeters. In the posterior approach: shoulder vertical thickness divided by 2 to approximate the depth of the SSC in the sagittal-oblique view, and the depth of the SSN in the posterior view. In the anterior approach: shoulder horizontal thickness divided by 4 to approximate the depth of the SSN in the anterior view.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLimitations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe sonographic visibility is rather subjective and can be influenced by the skills of the sonographic examiner [9, 14]. The quality of the used devise also play role. The commonly used 11-17 MHz ultrasound transducers in shoulder examinations do not yield detailed resolution of the small SSN structure in size of approximately 10.0 x 6.0 mm [2, 3]. Even though the 24 MHz ultrasound transducers yield higher sonographic resolution, its beam penetration is limited to relatively shorter distance of approximately 3.5 cm. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe SN is anisotropic and may not project with high visibility on sonograms (Figure 4, 5, 6). However, it is traceable while examining \u003cem\u003ein vivo\u003c/em\u003e by the above described maneuvers (Video 1,2, 3). The SV varies in quantity and course at the SSN with relatively small diameters of approximately 0.5 mm to 5.0 mm [2]. The course of the SV curve in direction as they pass through the SSC [2]. Accordingly, the Doppler detection is not reliable in mapping the SV topography. Distinguishing between suprascapular artery and vein may not be accurately achieved (Figure 4E, 5E, 6E), (Video 1,2, 3). \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe demography of the volunteer individuals was young in age and in overall good health and physical condition (Table 1). The obtained imaging results do not reflect the population as a whole. This was an observational study aimed to provide a descriptive manual. Therefore, the sample size was small limiting its statistical analysis. The provided images reflect a long term experimentation and training. This method requires some amount of practice prior to deliver patient care. \u0026nbsp;\u0026nbsp;\u003c/p\u003e"},{"header":"Statements and Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to acknowledge and thank David Kachlik (Department of Anatomy \u0026amp; Center for Endoscopic, Surgical and Clinical Anatomy (CESKA), Second Faculty of Medicine, Charles University, Prague, Czech Republic) for access to the cadaveric specimens and the ultrasound device; Nikola Jilkova and David Vala for their laboratory technical assistance. We also would like to acknowledge and thank the pregraduate students (Second Faculty of Medicine, Charles University, Prague, Czech Republic) Shihab Hajhamoud and Emma Sole Moreno for their assistance with the cadaveric specimen\u0026rsquo;s dissection, Omer Glazer for his assistance with the sonography practice, and Harshith Krishna Omprakash for his assistance with the video recordings.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe authors sincerely thank those who donated their bodies to science so that anatomical research could be performed. Results from such research can potentially increase mankind\u0026apos;s overall knowledge that can then improve patient care. Therefore, these donors and their families deserve our highest gratitude.\u003c/p\u003e\n\u003cp\u003eNonetheless, the authors would like to thank all the anonymous volunteers for their willingness and consent to volunteer. Their contribution was crucial and highly valuable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors declare no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo funds, grants, or other support was received.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompliance with Ethical Standards\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics Approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study and volunteers consent procedure was approved for research and education purposes by the Institutional Review Board (IRB) \u0026ndash; The Ethics Committee of the University Hospital Motol and Second Faculty of Medicine, Charles University, Prague, Czech Republic [Reference ID no. EK-353/19] and [Reference ID no. EK-1175.1.23/22].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAccess to cadavers are under the local corps donor program in adherence to the Czech Anatomical Society and European Union ethical, legal regulation and provision in accordance with Act Code No. 89/2012 Sb. of the Civil Code and Act Code No. 372/2011 Sb. on Article 7 of the Health Services amended provision. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInformed Consent\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eInformed consent was obtained from all participants prior to their participation. Participants were informed about the nature and purpose of the research as well as the procedures involved. Participants consented to publish the obtained photos, sonograms, video demonstrations, and the recorded data was anonymized. Participant confidentiality was maintained throughout the study, and all data were anonymized in accordance with applicable data protection regulations.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNote\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was conducted while the principal author was affiliated at [Department of Anatomy \u0026amp; Center for Endoscopic, Surgical and Clinical Anatomy (CESKA), Second Faculty of Medicine, Charles University, Prague, Czech Republic]. All necessary ethical approvals and facility use agreements were obtained during that time.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCRediT Author Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAzzat Al-Redouan\u003c/strong\u003e: Conceptualization, Methodology, Investigation, Visualization, Formal analysis, Data curation, Validation, Supervision, Project administration, Writing - Original Draft. \u003cstrong\u003eAimilia Theodorakioglou\u003c/strong\u003e: Methodology, Investigation, Visualization. \u003cstrong\u003eSeyed Mehdi Sadat\u003c/strong\u003e: Methodology, Investigation. \u003cstrong\u003ePetra Kriskova\u003c/strong\u003e:\u0026nbsp;Investigation, Visualization.\u0026nbsp;\u003cstrong\u003ePilar Dominguez R Fonte\u003c/strong\u003e: Investigation. \u003cstrong\u003eDeeksha Shailesh\u003c/strong\u003e: Investigation.\u0026nbsp;\u003cstrong\u003eShayan Ghezel Bash\u003c/strong\u003e:\u0026nbsp;Formal analysis.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAl-Redouan A, Benes M, Theodorakioglou A, Sadat SM, Modrak M, Kunc V, Kachlik D (2025) Muscles variations with topographical relationship to the suprascapular notch and its potential arthroscopic feasibility. Surg Radiol Anat 47(1):84. https://doi.org/10.1007/s00276-025-03595-y\u003c/li\u003e\n \u003cli\u003eAl-Redouan A, Holding K, Kachlik D (2021) \u0026quot;Suprascapular canal\u0026quot;: Anatomical and topographical description and its clinical implication in entrapment syndrome. Ann Anat 233:151593. https://doi.org/10.1016/j.aanat.2020.151593\u003c/li\u003e\n \u003cli\u003eAl-Redouan A, Hudak R, Nanka O, Kachlik D (2021) The morphological stenosis pattern of the suprascapular notch is revealed yielding higher incidence in the discrete type and elucidating the inevitability of osteoplasty in horizontally oriented stenosis. Knee Surg Sports Traumatol Arthrosc 29(7):2272\u0026ndash;2280. https://doi.org/10.1007/s00167-020-06168-1\u003c/li\u003e\n \u003cli\u003eAl-Redouan A, Kachlik D (2022) Suprascapular notch cross-sectional area on MRI is not highly accurate in the diagnosis of suprascapular nerve entrapment \u0026ndash; counter point of view. Korean J Anesthesiol 75(6):536\u0026ndash;538. https://doi.org/10.4097/kja.22413\u003c/li\u003e\n \u003cli\u003eBahner DP, Blickendorf JM, Bockbrader M, Adkins E, Vira A, Boulger C, Panchal AR (2016) Language of Transducer Manipulation: Codifying Terms for Effective Teaching. J Ultrasound Med 35(1):183\u0026ndash;188. https://doi.org/10.7863/ultra.15.02036\u003c/li\u003e\n \u003cli\u003eBouffard J, Martinez R, Plamondon A, C\u0026ocirc;t\u0026eacute; JN, Begon M (2019) Sex differences in glenohumeral muscle activation and coactivation during a box lifting task. Ergonomics 62(10):1327\u0026ndash;1338. https://doi.org/10.1080/00140139.2019.1640396\u003c/li\u003e\n \u003cli\u003eCid MM, Oliveira AB, Januario LB, C\u0026ocirc;t\u0026eacute; JN, de F\u0026aacute;tima Carreira Moreira R, Madeleine P (2019) Are there sex differences in muscle coordination of the upper girdle during a sustained motor task?. J Electromyogr Kinesiol 45:1\u0026ndash;10. https://doi.org/10.1016/j.jelekin.2019.01.003\u003c/li\u003e\n \u003cli\u003eEvangelista T, Kandji M, Lacene E, Chanut A, Bui MT, Marty R, Buffat L, Knoblauch K, Rudkin BB, Romero NB (2022) Comprehensive morphometric assessment of deltoid muscle development in children: A cross-sectional study. EBioMedicine 86:104367. https://doi.org/10.1016/j.ebiom.2022.104367\u003c/li\u003e\n \u003cli\u003eFernandes VT, De Santis RJ, Enepekides DJ, Higgins KM (2015) Surgeon-performed ultrasound guided fine-needle aspirate biopsy with report of learning curve; a consecutive case-series study. J Otolaryngol Head Neck Surg 44:42. https://doi.org/10.1186/s40463-015-0099-x\u003c/li\u003e\n \u003cli\u003eFischetti AJ, Scott RC (2007) Basic ultrasound beam formation and instrumentation. Clin Tech Small Anim Pract 22(3):90\u0026ndash;92. https://doi.org/10.1053/j.ctsap.2007.05.002\u003c/li\u003e\n \u003cli\u003eIhnatsenka B, Boezaart AP (2010) Ultrasound: Basic understanding and learning the language. Int J Shoulder Surg 4(3):55\u0026ndash;62. https://doi.org/10.4103/0973-6042.76960\u003c/li\u003e\n \u003cli\u003eJezierski H, Podg\u0026oacute;rski M, Wysiadecki G, Olewnik Ł, De Caro R, Macchi V, Polguj M (2018) Morphological Aspects in Ultrasound Visualisation of the Suprascapular Notch Region: A Study Based on a New Four-Step Protocol. J Clin Med 7(12):491. https://doi.org/10.3390/jcm7120491\u003c/li\u003e\n \u003cli\u003eKamal K, Dahiya N, Singh R, Saini S, Taxak S, Kapoor S (2018) Comparative study of anatomical landmark-guided versus ultrasound-guided suprascapular nerve block in chronic shoulder pain. Saudi J Anaesth 12(1):22\u0026ndash;27. https://doi.org/10.4103/sja.SJA_123_17\u003c/li\u003e\n \u003cli\u003eKeles A, Ozkan FU, Giray E, Keles P, Karip B, Kahraman AN, Aktas İ (2023) Ultrasound-Guided Suprascapular Nerve Block at Suprascapular Notch-Do We Really Target Suprascapular Notch or Not? Where Is Our Real Target?. J Ultrasound Med 42(9):2167\u0026ndash;2170. https://doi.org/10.1002/jum.16237\u003c/li\u003e\n \u003cli\u003eLaumonerie P, Blasco L, Tibbo ME, Panagiotis K, Fernandes O, Lauwers F, Bonnevialle N, Mansat P, Ohl X (2019) Ultrasound-guided versus landmark-based approach to the distal suprascapular nerve block: a comparative cadaveric study. Arthroscopy 35(8):2274\u0026ndash;2281. https://doi.org/10.1016/j.arthro.2019.02.050\u003c/li\u003e\n \u003cli\u003eLaumonerie P, Ferr\u0026eacute; F, Cances J, Tibbo ME, Roumigui\u0026eacute; M, Mansat P, Minville V (2018) Ultrasound-guided proximal suprascapular nerve block: A cadaveric study. Clin Anat 31(6):824\u0026ndash;829. https://doi.org/10.1002/ca.23199\u003c/li\u003e\n \u003cli\u003eLaumonerie P, Lap\u0026egrave;gue F, Chantalat E, Sans N, Mansat P, Faruch M (2017) Description and ultrasound targeting of the origin of the suprascapular nerve. Clin Anat 30(6):747\u0026ndash;752. https://doi.org/10.1002/ca.22936\u003c/li\u003e\n \u003cli\u003eMaar M, Lee J, Tardi A, Zheng YY, Wong C, Gao J (2022) Inter-transducer variability of ultrasound image quality in obese adults: Qualitative and quantitative comparisons. Clin Imaging 92:63\u0026ndash;71. https://doi.org/10.1016/j.clinimag.2022.09.010\u003c/li\u003e\n \u003cli\u003ePeng PW, Wiley MJ, Liang J, Bellingham GA (2010) Ultrasound-guided suprascapular nerve block: a correlation with fluoroscopic and cadaveric findings. Can J Anaesth 57(2):143\u0026ndash;148. https://doi.org/10.1007/s12630-009-9234-3\u003c/li\u003e\n \u003cli\u003ePoland GA, Borrud A, Jacobson RM, McDermott K, Wollan PC, Brakke D, Charboneau JW (1997) Determination of deltoid fat pad thickness. Implications for needle length in adult immunization. JAMA 277(21):1709\u0026ndash;1711.\u003c/li\u003e\n \u003cli\u003ePrenaud C, Loubeyre J, Soubeyrand M (2021) Decompression of the suprascapular nerve at the suprascapular notch under combined arthroscopic and ultrasound guidance. Sci Rep 11(1):18906. https://doi.org/10.1038/s41598-021-98463-1\u003c/li\u003e\n \u003cli\u003eRoh MS, Wang VM, April EW, Pollock RG, Bigliani LU, Flatow EL (2000) Anterior and posterior musculotendinous anatomy of the supraspinatus. J Shoulder Elbow Surg 9(5):436\u0026ndash;440. https://doi.org/10.1067/mse.2000.108387\u003c/li\u003e\n \u003cli\u003eSanchez ER, Sanchez R, Moliver C (2014) Anatomic relationship of the pectoralis major and minor muscles: a cadaveric study. Aesthet Surg J 34(2):258\u0026ndash;263. https://doi.org/10.1177/1090820X13519643\u003c/li\u003e\n \u003cli\u003eSetlock CA, Lulic-Kuryllo T, Leonardis JM, Kulik M, Lipps DB (2021) Age and sex influence the activation-dependent stiffness of the pectoralis major. J Anat 239(2):479\u0026ndash;488. https://doi.org/10.1111/joa.13455\u003c/li\u003e\n \u003cli\u003eUthaikhup S, Wannaprom N, Kummaung P (2015) Effects of gender and hand dominance on size of the lower trapezius muscle. Muscle Nerve 52(4):576\u0026ndash;579. https://doi.org/10.1002/mus.24570\u003c/li\u003e\n \u003cli\u003eWu WT, Mezian K, Ricci V, Lin CS, Chang KV, \u0026Ouml;z\u0026ccedil;akar L (2023) Dynamic ultrasound examination painting the picture of omohyoid muscle strain and associated suprascapular nerve entrapment. Pain Med 24(10):1197\u0026ndash;1199. https://doi.org/10.1093/pm/pnad085\u003c/li\u003e\n \u003cli\u003eWu YT, Ho CW, Chen YL, Li TY, Lee KC, Chen LC (2014) Ultrasound-guided pulsed radiofrequency stimulation of the suprascapular nerve for adhesive capsulitis: a prospective, randomized, controlled trial. Anesth Analg 119(3):686\u0026ndash;692. https://doi.org/10.1213/ANE.0000000000000354\u003c/li\u003e\n \u003cli\u003eYildizhan R, Cuce I, Veziroglu E, Calis M (2024) Comparison of Spinoglenoid Versus Suprascapular Notch Approaches for Ultrasound-Guided Distal Suprascapular Nerve Blocks for Shoulder Pain: A Prospective Randomized Trial. Pain Physician 27(1):11\u0026ndash;19.\u003c/li\u003e\n \u003cli\u003eY\u0026ouml;r\u0026uuml;koğlu HU, G\u0026uuml;rkan Y, Aksu C (2023) Anterior approach to suprascapular nerve block combined with axillary nerve block for shoulder arthroplasty. Agri 35(3):175\u0026ndash;176. https://doi.org/10.14744/agri.2021.77527\u003c/li\u003e\n \u003cli\u003eY\u0026uuml;cesoy C, Akkaya T, Ozel O, C\u0026ouml;mert A, T\u0026uuml;ccar E, Bedirli N, Unl\u0026uuml; E, Hekimoğlu B, G\u0026uuml;m\u0026uuml;ş H (2009) Ultrasonographic evaluation and morphometric measurements of the suprascapular notch. Surg Radiol Anat 31(6):409\u0026ndash;414. https://doi.org/10.1007/s00276-008-0458-7\u003cstrong\u003e\u003c/strong\u003e\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Table","content":"\u003cp\u003eTable 1 is available in the Supplementary Files section\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"surgical-and-radiologic-anatomy","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"sara","sideBox":"Learn more about [Surgical and Radiologic Anatomy](http://link.springer.com/journal/276)","snPcode":"276","submissionUrl":"https://submission.nature.com/new-submission/276/3","title":"Surgical and Radiologic Anatomy","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"suprascapular canal ultrasound, suprascapular notch ultrasound, sonographic anatomy, suprascapular nerve ultrasound, sonography, ultrasound","lastPublishedDoi":"10.21203/rs.3.rs-7808265/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7808265/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003ePurpose\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eVisualizing the suprascapular notch on radiographic images is challenging. Sonography of the suprascapular notch in the clinical practice had been performed only from a superior shoulder approach projecting a posterior view. Sonographic anterior view of the suprascapular notch has not been presented in the clinical practice. We provide anatomically based ultrasound-probe techniques to capture optimal sonograms exposing the suprascapular canal topography and its key structures.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSonography of the superior shoulder region was bilaterally experimented on ten young healthy (five females and five males) volunteers of age ±21. We experimented scanning the superior and anterior area of the shoulder at differing angles with ultrasound probe explorative manipulations. Different shoulder maneuvers were attempted in seated and lying positions. Age, sex, BMI, and shoulder thickness were recorded. The visibility of the sonograms was compared based on the obtained parameters. In addition, ultrasound-guided tunnel insertion was performed on a fresh cadaver beside formalin fixed cadaveric dissection for confirmation and illustration of the suprascapular canal anatomy.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA comprehensive protocol was constructed and tested yielding satisfactory sonographic visualization of the suprascapular canal and notch. The sonographic visibility and its quality seemed to be not affected by the BMI directly but by the shoulder thickness with better visibility in females compared to males.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe provide a four stepwise shoulder and ultrasound-probe maneuvers protocol yielding an anterior sonographic visibility of the suprascapular notch. This approach enhances the ultrasound-guided clinical practice in suprascapular nerve blocks with more precise targeting especially distal to the suprascapular notch.\u003c/p\u003e","manuscriptTitle":"Sonographic Visualization of the Suprascapular Canal with Focus on the Suprascapular Notch: Anatomical Description and Ultrasound-Probe Techniques","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-23 15:01:35","doi":"10.21203/rs.3.rs-7808265/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-01-26T11:14:01+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-26T11:11:53+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"192264300988477935753545915326499547649","date":"2026-01-26T11:10:12+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-19T16:35:57+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"271127871574078068323220434493808553917","date":"2025-12-16T10:34:28+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"190721575618610306498736142862316822685","date":"2025-10-25T13:35:48+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-10-09T15:53:08+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-10-09T15:49:12+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-10-09T06:51:01+00:00","index":"","fulltext":""},{"type":"submitted","content":"Surgical and Radiologic Anatomy","date":"2025-10-08T13:03:38+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"surgical-and-radiologic-anatomy","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"sara","sideBox":"Learn more about [Surgical and Radiologic Anatomy](http://link.springer.com/journal/276)","snPcode":"276","submissionUrl":"https://submission.nature.com/new-submission/276/3","title":"Surgical and Radiologic Anatomy","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"41ecb4fe-1961-4dde-9f65-15a3078ddce6","owner":[],"postedDate":"October 23rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-03-02T16:03:45+00:00","versionOfRecord":{"articleIdentity":"rs-7808265","link":"https://doi.org/10.1007/s00276-026-03840-y","journal":{"identity":"surgical-and-radiologic-anatomy","isVorOnly":false,"title":"Surgical and Radiologic Anatomy"},"publishedOn":"2026-02-27 15:59:52","publishedOnDateReadable":"February 27th, 2026"},"versionCreatedAt":"2025-10-23 15:01:35","video":"","vorDoi":"10.1007/s00276-026-03840-y","vorDoiUrl":"https://doi.org/10.1007/s00276-026-03840-y","workflowStages":[]},"version":"v1","identity":"rs-7808265","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7808265","identity":"rs-7808265","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}