Two- and Three-Dimensional Ultrasonographic Characterization of the Modiolus and Adjacent Facial Muscles in Healthy Adults

Two- and Three-Dimensional Ultrasonographic Characterization of the Modiolus and Adjacent Facial Muscles in Healthy Adults | 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 Two- and Three-Dimensional Ultrasonographic Characterization of the Modiolus and Adjacent Facial Muscles in Healthy Adults Puchen Peng, Min Pan, Hongwei Gao, Lingeng Chen, Ruodan Lan, Haifen Liao, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7379927/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Objectives: This study aimed to investigate the modiolus in healthy adults using high-frequency ultrasound, establish standardized scanning protocols, and clearly delineate the two- and three-dimensional sonographic features of the modiolus and its associated facial muscles. Methods: Healthy adult volunteers were examined using a Philips ultrasound system equipped with high-frequency linear and broadband linear transducers. Bilateral scans of the modiolus and adjacent facial muscles were performed to determine optimal scanning approaches and characterize the sonographic appearances in both two- and three-dimensional modalities. Results: High-frequency ultrasound, with its superior soft tissue resolution, enabled clear visualization of the modiolus and related facial expression muscles. The scanning protocol for this anatomical region was successfully established, and its typical sonographic features were described. The findings indicate that high-frequency ultrasound is a reliable imaging tool for defining the ultrasonographic anatomy of the oral commissure modiolus region. Conclusions: High-frequency ultrasound provides detailed anatomical visualization of the modiolus and associated facial muscles and may serve as an important reference for clinical and research applications involving the lower facial region. high-frequency ultrasound modiolus three-dimensional ultrasound imaging facial expression muscles tomographic ultrasound images Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 Figure 21 Figure 22 Figure 23 Introduction The modiolus is a key bilateral anatomical structure located at the oral commissures. It is essentially a fibromuscular mass formed by the interlacing and blending of perioral facial expression muscle fibers in the lateral commissural region( 1 ). This compact, three-dimensional structure is primarily composed of contributions from the orbicularis oris, levator anguli oris, depressor anguli oris, zygomaticus major, risorius, buccinator, and the modiolus portion of the platysma( 2 ). Clinically, palpation near the oral commissure often reveals a firm nodular mass in this area( 3 ). The exact position of the modiolus varies markedly among individuals; its center may be located superolateral, inferolateral, or immediately adjacent to the oral commissure. Based on available anatomical data, it is most commonly situated approximately 10–20 mm lateral and 0–10 mm inferior to the commissural center. Its size and morphology are influenced by ethnicity, sex, and age, and in gross anatomy it typically appears as an inverted blunt cone. As a biomechanical hub of the lower facial expression muscles, the modiolus plays a crucial role in generating and coordinating facial expressions( 4 ). It serves not only as a common attachment point for multiple perioral muscles but also as an integrative structure transmitting muscular forces during expressions such as smiling and pouting. The dynamic balance of muscle contraction and relaxation determines both the resting position of the modiolus and its displacement during perioral movements. Given its functional significance, the modiolus has considerable potential clinical relevance, particularly in facial rejuvenation procedures, evaluation and treatment planning for facial paralysis, and reconstructive surgeries involving commissural repair. Despite its importance, imaging studies focusing on the modiolus and its constituent muscles remain limited. In this study, we performed systematic two- and three-dimensional high-frequency ultrasonographic analysis of the modiolus region in healthy adults. Our aim was to establish a standardized imaging description framework and provide reliable sonographic reference data to support relevant clinical interventions. Materials and Methods Ultrasound Equipment and Methods Ultrasound examinations were performed using a Philips EPIQ 7 color Doppler ultrasound system equipped with three types of transducers: a high-frequency hockey-stick probe (L15–7io), a high-frequency linear probe (L12–5), and a broadband linear probe (VL13–5). The musculoskeletal preset mode was selected for image acquisition. Image Acquisition Protocol Participants were positioned in the standard supine position with the head supported on a comfortable cushion, ensuring complete relaxation of the facial muscles and natural gentle closure of the lips. An adequate amount of ultrasound coupling gel was evenly applied to the skin surface over the target region. Systematic multi-plane and multi-angle scanning of the modiolus and related facial expression muscles was performed. When necessary, participants were instructed to perform a standardized smiling maneuver to dynamically assess muscle contraction and morphological changes of the modiolus. Image Analysis and Quality Control To ensure objectivity and accuracy in image interpretation, the acquired ultrasound images were independently reviewed by two physicians trained in facial muscle ultrasonography. In cases of disagreement, the images were submitted to a senior physician with greater experience for re-evaluation. Consensus was reached through group discussion, and the agreed results were recorded as the final study data. Ultrasonographic Scanning Method for the Modiolus 1.1 Short-Axis Orientation and Visualization For short-axis imaging of the modiolus, a high-frequency linear-array transducer is positioned approximately 0.8–1.2 cm lateral to the oral commissure. The transducer is held steadily, and its orientation is adjusted to align with the desired scanning plane. Dynamic assessment is achieved by applying slight translational movements and gentle rotations to optimize the insonation angle. Under these conditions, the modiolus can be visualized in its characteristic short-axis appearance, presenting as an inverted triangular hypoechoic structure with relatively well-defined margins, located deep to the skin and subcutaneous adipose tissue(Fig. 1). This hypoechoic area corresponds to the transverse section of densely interlaced muscle fiber bundles within the modiolus. 1.2 Three-Dimensional Imaging of the Modiolus A broadband linear-array transducer was positioned lateral to the oral commissure, with the transducer center located approximately 0.5–0.8 cm from the lateral border of the commissure. Following fine positional adjustments to optimize image quality, three-dimensional (3D) imaging mode was initiated to acquire volumetric datasets of the modiolus (Figs. 2 and 3). The advanced measurement tool utilizing the “stacked contour” algorithm was employed to quantify both the modiolus volume and its maximal cross-sectional perimeter. Upon completion, the Philips ultrasound system automatically generated a 3D reconstruction of the modiolus (Fig. 4). Multiplanar reconstruction (MPR) mode enabled independent visualization of the modiolus’ three-dimensional architecture (Fig. 5), whereas wireframe rendering provided an intuitive spatial depiction of its morphology (Fig. 6). In ISLICE mode, sectional imaging of the modiolus was conducted in transverse (Fig. 7), sagittal (Fig. 8), and coronal planes (Fig. 9), facilitating detailed evaluation of its cross-sectional anatomy from multiple perspectives and depths. 2. Tracking and Visualization of the Origin and Insertion of Modiolus-Associated Facial Expression Muscles Following clear delineation of the modiolus on the short-axis view, the transducer tilt angle was systematically adjusted to acquire multi-angular oblique scans, facilitating the tracking and identification of muscle bundles converging into the modiolus. The muscles examined included the orbicularis oris, levator anguli oris, zygomaticus major, risorius, buccinator, depressor anguli oris, and the modiolus segment of the platysma. These muscle fibers demonstrated a radiating pattern as they progressively merged into the hypoechoic margins of the modiolus. Insertions at the modiolus were distinctly visualized, and origins were traced retrogradely where feasible. Dynamic assessment was performed by instructing subjects to execute mild perioral contractions, enabling real-time observation of morphological changes of the modiolus and its connection with adjacent muscle bundles, thereby further confirming the underlying anatomical relationships. The insertion points of facial expression muscles exhibit various anatomical variations. This article only clarifies the cases where the perioral expression muscles insert into the modiolus. 2.1 Orbicularis Oris Muscle Anatomy The orbicularis oris muscle is divided into the pars marginalis (lip margin part) and pars peripheralis (lip peripheral part). The majority of fibers of the lateral bundle in the pars peripheralis originate from the modiolus at the oral commissure. Each side’s pars marginalis typically consists of a single thin fiber bundle (occasionally two), whose lateral fibers converge along the horizontal line of the oral commissure and attach to the deepest portion at the base of the modiolus( 5 , 6 ). Ultrasonographic Examination The transducer is positioned transversely along the lip margin between the philtrum and the oral commissure. This placement allows visualization of the hypoechoic orbicularis oris muscle and its attachment at the modiolus(Figs. 10and11). 2.2 Levator Anguli Oris Muscle Anatomy The levator anguli oris originates from the canine fossa of the maxilla, just below the infraorbital foramen, and inserts at the oral commissure. Its fibers interlace with those of the orbicularis oris, zygomaticus major, and depressor anguli oris, forming a complex muscle network at the commissure( 2 , 7 ). Ultrasonographic Examination For ultrasound examination, the transducer is first placed horizontally over the infraorbital foramen to visualize the deep levator labii superioris beneath the orbicularis oculi. Then, the probe is rotated to about a 45°oblique longitudinal angle relative to a vertical line through the pupil midpoint, clearly displaying the levator labii superioris and levator anguli oris along the maxilla, including their origin and course (Fig. 12)( 8 , 9 ). Slow scanning along the levator anguli oris’s long axis toward the oral commissure allows visualization of its insertion at the modiolus (Fig. 13). 2.3 Depressor Anguli Oris Muscle Anatomy The depressor anguli oris originates from the mental tubercle and adjacent mandibular oblique line, located inferior and lateral to the depressor labii inferioris origin. Its fibers converge into a narrow bundle that interweaves with the orbicularis oris and risorius muscles at the oral commissure, with some fibers extending into the levator anguli oris( 2 , 10 ). Ultrasonographic Examination For ultrasound scanning, the transducer is positioned at the intersection of the mandibular oblique line and a vertical line through the pupil midpoint, oriented perpendicular to the oblique line. This setup provides clear visualization of the muscle’s origin and course (Fig. 14). The probe is then advanced slowly along the muscle’s long axis toward the oral commissure, revealing its insertion at the superficial layer of the modiolus(Fig. 15). 2.4 Zygomaticus Major Muscle Anatomy The zygomaticus major originates from the zygomatic bone near the zygomaticotemporal suture and extends toward the oral commissure. It interlaces with the levator anguli oris, orbicularis oris, and deeper muscle bundles( 2 , 11 ). Ultrasonographic Examination The transducer is positioned just below the intersection of the infraorbital rim horizontal line and the vertical line at the lateral orbital margin, oriented obliquely toward the oral commissure in a longitudinal plane. This allows clear visualization of the hypoechoic origin and course of the zygomaticus major(Fig. 16). Slowly advancing the probe toward the oral commissure reveals the muscle’s insertion at the modiolus (Fig. 17). 2.5 Risorius Muscle Anatomy The risorius muscle varies from a single or multiple slender fibers to a broad, thin, fan-shaped muscle. Its surrounding fibers attach partially or entirely to several anatomical structures, including the zygomatic arch, parotid fascia, the masseteric fascia anterior to the parotid gland, the platysma fascia encircling the modiolus at the oral commissure, and the fascia covering the mastoid process. These fibers converge at and around the apex of the modiolus( 2 , 12 ). Ultrasound Scanning The transducer is positioned at the intersection of the mandibular body’s lateral oblique line and a vertical line passing through the lateral canthus, oriented perpendicular to the lateral oblique line of the mandible. This placement allows visualization of the risorius muscle origin as a thin, hypoechoic band(Fig. 18). Scanning along the long axis of the risorius towards the oral commissure with slow probe movement reveals the muscle insertion at the modiolus (Fig. 19). . 2.6 Buccinator Muscle Anatomy The buccinator muscle is a thin, quadrilateral muscle located in the buccal region between the maxilla and mandible. Its fibers converge toward the oral commissure, ultimately inserting into the modiolus( 2 , 13 ). Ultrasonographic Examination For scanning, the transducer is positioned at the intersection of the external oblique line of the mandible and the vertical line through the lateral canthus, with its orientation perpendicular to the external oblique line. This placement allows clear visualization of the buccinator’s course(Fig. 20). Subsequently, the probe is slowly advanced along the longitudinal axis of the muscle fibers toward the oral commissure, enabling observation of the buccinator’s insertion at the modiolus (Fig. 21). 2.7 Platysma Muscle Anatomy The platysma, an integral component of the orbicularis oris complex, comprises distinct regions including the mandibular, labial, and modiolus portions. Within the modiolus region, most platysma fibers converge posterior-laterally to the depressor anguli oris muscle at the posterior lip, ultimately inserting at the apex of the modiolus within its superficial layer. A small subset of fine fibers terminates directly at the cheek skin or mucosa( 2 ). Ultrasonographic Examination During ultrasound examination, the transducer is positioned obliquely at the intersection of the lateral mandibular line and the anterior border of the masseter muscle, allowing clear visualization of the transverse section of the mandibular portion of the platysma(Fig. 22). The probe is then slowly advanced toward the oral commissure along the muscle’s long axis, revealing progressive thinning of the platysma and its termination at the modiolus(Fig. 23). Discussion This study, grounded in comprehensive anatomical knowledge, systematically investigated the ultrasonographic examination methods of the modiolus and its surrounding facial expression muscles. By integrating multi-angle, multi-layered sectional scanning with three-dimensional imaging techniques, we achieved detailed sectional visualization and 3D reconstruction of the modiolus, thereby addressing a notable gap in ultrasonographic research on this structure. These findings provide robust imaging support for its clinical application. Furthermore, this technique offers reliable imaging guidance for ultrasound-assisted facial rejuvenation procedures( 9 , 10 , 14 , 15 ), assessment of facial muscle function recovery in patients with facial paralysis( 16 – 18 ), and preoperative and postoperative evaluation in reconstructive surgeries involving the modiolus( 19 – 21 ). Moving forward, we aim to strengthen interdisciplinary collaboration with clinical departments to promote and further develop the clinical utility of high-frequency ultrasonography for modiolus assessment. Conclusion High-frequency ultrasound provides a reliable and noninvasive method for detailed assessment of the modiolus and adjacent mimetic muscles, offering potential applications in both anatomical research and clinical practice. Declarations Author Contribution Min Pan, Zhansen E: Jointly conceived the study and approved the manuscriptHancai Luo: Oversaw the overall management of the study and approved the manuscriptPuchen Peng: Collected data and drafted the manuscriptHongwei Gao, Lingeng Chen, Ruodan Lan, Haifen Liao: Recruited volunteers and coordinated the work References --- KH-Y, SE -Y I-OJ-W, H -C, S -G et al - Discovery of the Ligament of Modiolus: Anatomical Insights and Clinical. D – 7701756. (– 1432–5241 (Electronic)):– 2552–2555 S S. Gray’s Anatomy: The Anatomical Basis of Clinical Practice. 42 ed. London: Elsevier; (2020) Liu S, Cong L, Pongprutthipan M, Lee W, Luo X, Han X et al (2023) Use of LetibotulinumtoxinA for Aesthetic Treatment of Asians: A Consensus. Aesthet Surg J 43(11):Np962–np74 WT -W KV-C, --- I-O, O -N, HC -C V-R et al - Lip Sonoanatomy and Relevance to Aesthetic Filler Injections: A Pictorial Review. D – 101130964. (– 1473–2165 (Electronic)):– e70164. 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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-7379927","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":505242376,"identity":"440ff93c-25bb-4bf1-9f98-ed2c1f4d54b1","order_by":0,"name":"Puchen Peng","email":"","orcid":"","institution":"Guangzhou University of Chinese Medicine Shenzhen Hospital（Futian)","correspondingAuthor":false,"prefix":"","firstName":"Puchen","middleName":"","lastName":"Peng","suffix":""},{"id":505242377,"identity":"ba1590db-98c5-445c-9606-341d60e191a9","order_by":1,"name":"Min Pan","email":"","orcid":"","institution":"Guangzhou University of Chinese 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legend\u003c/p\u003e","description":"","filename":"Figure10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7379927/v1/9b8ff7abf09c7729ff206fda.jpg"},{"id":90504088,"identity":"5183f63e-476b-43f8-ab67-058b2f730701","added_by":"auto","created_at":"2025-09-03 12:15:47","extension":"jpg","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":92207,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Figure11.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7379927/v1/c62173b40092844af33b7889.jpg"},{"id":90503248,"identity":"d3272f24-8e6e-4f0a-a88d-bd04ccbbff6a","added_by":"auto","created_at":"2025-09-03 12:07:47","extension":"jpg","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":100505,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Figure12.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7379927/v1/127a44ba201655c579f4c53d.jpg"},{"id":90505406,"identity":"ec257fdc-7713-4fcd-a800-caaf5f71d266","added_by":"auto","created_at":"2025-09-03 12:31:47","extension":"jpg","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":84084,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Figure13.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7379927/v1/bbbf946616ead3d6023e949d.jpg"},{"id":90504090,"identity":"ab3dec6f-1e0c-4c0e-9ccf-250ad288a706","added_by":"auto","created_at":"2025-09-03 12:15:48","extension":"jpg","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":76109,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Figure14.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7379927/v1/9b9765b13fde8c960f3da6b3.jpg"},{"id":90503272,"identity":"d2deec80-2659-4220-acfb-ee10a0975f10","added_by":"auto","created_at":"2025-09-03 12:07:48","extension":"jpg","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":81143,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Figure15.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7379927/v1/5ebe7043880c41d31d1c2016.jpg"},{"id":90503265,"identity":"e55e111c-c63f-47d7-ae87-527236027a36","added_by":"auto","created_at":"2025-09-03 12:07:48","extension":"jpg","order_by":16,"title":"Figure 16","display":"","copyAsset":false,"role":"figure","size":94029,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Figure16.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7379927/v1/7bd32795d5fbd2f8154359d0.jpg"},{"id":90503292,"identity":"59c90007-c239-40cf-b8d6-105e70e21efd","added_by":"auto","created_at":"2025-09-03 12:07:48","extension":"jpg","order_by":17,"title":"Figure 17","display":"","copyAsset":false,"role":"figure","size":95620,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Figure17.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7379927/v1/648edec61b821fd62b44a1ff.jpg"},{"id":90504087,"identity":"39753357-8671-45e5-9c2a-d2e715854215","added_by":"auto","created_at":"2025-09-03 12:15:47","extension":"jpg","order_by":18,"title":"Figure 18","display":"","copyAsset":false,"role":"figure","size":92413,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Figure18.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7379927/v1/d867da91bc28f5261848b2b3.jpg"},{"id":90503264,"identity":"81c16261-1643-4418-821b-c4e5f27671c2","added_by":"auto","created_at":"2025-09-03 12:07:48","extension":"jpg","order_by":19,"title":"Figure 19","display":"","copyAsset":false,"role":"figure","size":92568,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Figure19.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7379927/v1/7e508872e6f7de4e863f05ae.jpg"},{"id":90504098,"identity":"42d9d2b0-0556-4ab1-bf1f-a5f151271f28","added_by":"auto","created_at":"2025-09-03 12:15:48","extension":"jpg","order_by":20,"title":"Figure 20","display":"","copyAsset":false,"role":"figure","size":108006,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Figure20.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7379927/v1/a4914d316cd4899798ef7115.jpg"},{"id":90504714,"identity":"580f7dd1-6f9f-4f82-b6a9-c71997582b21","added_by":"auto","created_at":"2025-09-03 12:23:49","extension":"jpg","order_by":21,"title":"Figure 21","display":"","copyAsset":false,"role":"figure","size":105762,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Figure21.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7379927/v1/4cb0c400f68771ccc56b9ab9.jpg"},{"id":90504700,"identity":"1c16e491-2665-4750-981a-d03f3f21f69c","added_by":"auto","created_at":"2025-09-03 12:23:48","extension":"jpg","order_by":22,"title":"Figure 22","display":"","copyAsset":false,"role":"figure","size":103151,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Figure22.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7379927/v1/b76829e364bab8bf0246d542.jpg"},{"id":90505411,"identity":"40da81b9-5520-4665-9ea6-d0a6b21a662d","added_by":"auto","created_at":"2025-09-03 12:31:48","extension":"jpg","order_by":23,"title":"Figure 23","display":"","copyAsset":false,"role":"figure","size":95764,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Figure23.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7379927/v1/c0d35a4f7faab5db28e6a461.jpg"},{"id":91149256,"identity":"ea47e7fa-9dcf-4176-9414-bd30949f6cfe","added_by":"auto","created_at":"2025-09-12 06:47:59","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3271588,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7379927/v1/96f9b3e5-d257-4e84-97fe-a66519535223.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Two- and Three-Dimensional Ultrasonographic Characterization of the Modiolus and Adjacent Facial Muscles in Healthy Adults","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe modiolus is a key bilateral anatomical structure located at the oral commissures. It is essentially a fibromuscular mass formed by the interlacing and blending of perioral facial expression muscle fibers in the lateral commissural region(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). This compact, three-dimensional structure is primarily composed of contributions from the orbicularis oris, levator anguli oris, depressor anguli oris, zygomaticus major, risorius, buccinator, and the modiolus portion of the platysma(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). Clinically, palpation near the oral commissure often reveals a firm nodular mass in this area(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe exact position of the modiolus varies markedly among individuals; its center may be located superolateral, inferolateral, or immediately adjacent to the oral commissure. Based on available anatomical data, it is most commonly situated approximately 10\u0026ndash;20 mm lateral and 0\u0026ndash;10 mm inferior to the commissural center. Its size and morphology are influenced by ethnicity, sex, and age, and in gross anatomy it typically appears as an inverted blunt cone.\u003c/p\u003e\u003cp\u003eAs a biomechanical hub of the lower facial expression muscles, the modiolus plays a crucial role in generating and coordinating facial expressions(\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). It serves not only as a common attachment point for multiple perioral muscles but also as an integrative structure transmitting muscular forces during expressions such as smiling and pouting. The dynamic balance of muscle contraction and relaxation determines both the resting position of the modiolus and its displacement during perioral movements.\u003c/p\u003e\u003cp\u003eGiven its functional significance, the modiolus has considerable potential clinical relevance, particularly in facial rejuvenation procedures, evaluation and treatment planning for facial paralysis, and reconstructive surgeries involving commissural repair.\u003c/p\u003e\u003cp\u003eDespite its importance, imaging studies focusing on the modiolus and its constituent muscles remain limited. In this study, we performed systematic two- and three-dimensional high-frequency ultrasonographic analysis of the modiolus region in healthy adults. Our aim was to establish a standardized imaging description framework and provide reliable sonographic reference data to support relevant clinical interventions.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cp\u003e\u003cb\u003eUltrasound Equipment and Methods\u003c/b\u003e\u003c/p\u003e\u003cp\u003eUltrasound examinations were performed using a Philips EPIQ 7 color Doppler ultrasound system equipped with three types of transducers: a high-frequency hockey-stick probe (L15–7io), a high-frequency linear probe (L12–5), and a broadband linear probe (VL13–5). The musculoskeletal preset mode was selected for image acquisition.\u003c/p\u003e\n\u003ch3\u003eImage Acquisition Protocol\u003c/h3\u003e\n\u003cp\u003e Participants were positioned in the standard supine position with the head supported on a comfortable cushion, ensuring complete relaxation of the facial muscles and natural gentle closure of the lips. An adequate amount of ultrasound coupling gel was evenly applied to the skin surface over the target region. Systematic multi-plane and multi-angle scanning of the modiolus and related facial expression muscles was performed. When necessary, participants were instructed to perform a standardized smiling maneuver to dynamically assess muscle contraction and morphological changes of the modiolus.\u003c/p\u003e\n\u003ch3\u003eImage Analysis and Quality Control\u003c/h3\u003e\n\u003cp\u003eTo ensure objectivity and accuracy in image interpretation, the acquired ultrasound images were independently reviewed by two physicians trained in facial muscle ultrasonography. In cases of disagreement, the images were submitted to a senior physician with greater experience for re-evaluation. Consensus was reached through group discussion, and the agreed results were recorded as the final study data.\u003c/p\u003e\n\u003ch3\u003eUltrasonographic Scanning Method for the Modiolus\u003c/h3\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e1.1 Short-Axis Orientation and Visualization\u003c/h2\u003e\u003cp\u003eFor short-axis imaging of the modiolus, a high-frequency linear-array transducer is positioned approximately 0.8–1.2 cm lateral to the oral commissure. The transducer is held steadily, and its orientation is adjusted to align with the desired scanning plane. Dynamic assessment is achieved by applying slight translational movements and gentle rotations to optimize the insonation angle. Under these conditions, the modiolus can be visualized in its characteristic short-axis appearance, presenting as an inverted triangular hypoechoic structure with relatively well-defined margins, located deep to the skin and subcutaneous adipose tissue(Fig.\u0026nbsp;1). This hypoechoic area corresponds to the transverse section of densely interlaced muscle fiber bundles within the modiolus.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e1.2 Three-Dimensional Imaging of the Modiolus\u003c/h2\u003e\u003cp\u003eA broadband linear-array transducer was positioned lateral to the oral commissure, with the transducer center located approximately 0.5–0.8 cm from the lateral border of the commissure. Following fine positional adjustments to optimize image quality, three-dimensional (3D) imaging mode was initiated to acquire volumetric datasets of the modiolus (Figs.\u0026nbsp;2 and 3). The advanced measurement tool utilizing the “stacked contour” algorithm was employed to quantify both the modiolus volume and its maximal cross-sectional perimeter. Upon completion, the Philips ultrasound system automatically generated a 3D reconstruction of the modiolus (Fig.\u0026nbsp;4). Multiplanar reconstruction (MPR) mode enabled independent visualization of the modiolus’ three-dimensional architecture (Fig.\u0026nbsp;5), whereas wireframe rendering provided an intuitive spatial depiction of its morphology (Fig.\u0026nbsp;6). In ISLICE mode, sectional imaging of the modiolus was conducted in transverse (Fig.\u0026nbsp;7), sagittal (Fig.\u0026nbsp;8), and coronal planes (Fig.\u0026nbsp;9), facilitating detailed evaluation of its cross-sectional anatomy from multiple perspectives and depths.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003e2. Tracking and Visualization of the Origin and Insertion of Modiolus-Associated Facial Expression Muscles\u003c/h3\u003e\n\u003cp\u003eFollowing clear delineation of the modiolus on the short-axis view, the transducer tilt angle was systematically adjusted to acquire multi-angular oblique scans, facilitating the tracking and identification of muscle bundles converging into the modiolus. The muscles examined included the orbicularis oris, levator anguli oris, zygomaticus major, risorius, buccinator, depressor anguli oris, and the modiolus segment of the platysma. These muscle fibers demonstrated a radiating pattern as they progressively merged into the hypoechoic margins of the modiolus. Insertions at the modiolus were distinctly visualized, and origins were traced retrogradely where feasible. Dynamic assessment was performed by instructing subjects to execute mild perioral contractions, enabling real-time observation of morphological changes of the modiolus and its connection with adjacent muscle bundles, thereby further confirming the underlying anatomical relationships.\u003c/p\u003e\u003cp\u003eThe insertion points of facial expression muscles exhibit various anatomical variations. This article only clarifies the cases where the perioral expression muscles insert into the modiolus.\u003c/p\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Orbicularis Oris Muscle\u003c/h2\u003e\u003cp\u003e\u003cstrong\u003eAnatomy\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eThe orbicularis oris muscle is divided into the pars marginalis (lip margin part) and pars peripheralis (lip peripheral part). The majority of fibers of the lateral bundle in the pars peripheralis originate from the modiolus at the oral commissure. Each side’s pars marginalis typically consists of a single thin fiber bundle (occasionally two), whose lateral fibers converge along the horizontal line of the oral commissure and attach to the deepest portion at the base of the modiolus(\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eUltrasonographic Examination\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eThe transducer is positioned transversely along the lip margin between the philtrum and the oral commissure. This placement allows visualization of the hypoechoic orbicularis oris muscle and its attachment at the modiolus(Figs.\u0026nbsp;10and11).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e2.2 \u003cb\u003eLevator Anguli Oris Muscle\u003c/b\u003e\u003c/h2\u003e\u003cp\u003e\u003cstrong\u003eAnatomy\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eThe levator anguli oris originates from the canine fossa of the maxilla, just below the infraorbital foramen, and inserts at the oral commissure. Its fibers interlace with those of the orbicularis oris, zygomaticus major, and depressor anguli oris, forming a complex muscle network at the commissure(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eUltrasonographic Examination\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eFor ultrasound examination, the transducer is first placed horizontally over the infraorbital foramen to visualize the deep levator labii superioris beneath the orbicularis oculi. Then, the probe is rotated to about a 45°oblique longitudinal angle relative to a vertical line through the pupil midpoint, clearly displaying the levator labii superioris and levator anguli oris along the maxilla, including their origin and course (Fig.\u0026nbsp;12)(\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). Slow scanning along the levator anguli oris’s long axis toward the oral commissure allows visualization of its insertion at the modiolus (Fig.\u0026nbsp;13).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Depressor Anguli Oris Muscle\u003c/h2\u003e\u003cp\u003e\u003cstrong\u003eAnatomy\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eThe depressor anguli oris originates from the mental tubercle and adjacent mandibular oblique line, located inferior and lateral to the depressor labii inferioris origin. Its fibers converge into a narrow bundle that interweaves with the orbicularis oris and risorius muscles at the oral commissure, with some fibers extending into the levator anguli oris(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eUltrasonographic Examination\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eFor ultrasound scanning, the transducer is positioned at the intersection of the mandibular oblique line and a vertical line through the pupil midpoint, oriented perpendicular to the oblique line. This setup provides clear visualization of the muscle’s origin and course (Fig.\u0026nbsp;14). The probe is then advanced slowly along the muscle’s long axis toward the oral commissure, revealing its insertion at the superficial layer of the modiolus(Fig.\u0026nbsp;15).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e2.4 Zygomaticus Major Muscle\u003c/h2\u003e\u003cp\u003e\u003cstrong\u003eAnatomy\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eThe zygomaticus major originates from the zygomatic bone near the zygomaticotemporal suture and extends toward the oral commissure. It interlaces with the levator anguli oris, orbicularis oris, and deeper muscle bundles(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eUltrasonographic Examination\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eThe transducer is positioned just below the intersection of the infraorbital rim horizontal line and the vertical line at the lateral orbital margin, oriented obliquely toward the oral commissure in a longitudinal plane. This allows clear visualization of the hypoechoic origin and course of the zygomaticus major(Fig.\u0026nbsp;16). Slowly advancing the probe toward the oral commissure reveals the muscle’s insertion at the modiolus (Fig.\u0026nbsp;17).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e2.5 Risorius Muscle\u003c/h2\u003e\u003cp\u003e\u003cstrong\u003eAnatomy\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eThe risorius muscle varies from a single or multiple slender fibers to a broad, thin, fan-shaped muscle. Its surrounding fibers attach partially or entirely to several anatomical structures, including the zygomatic arch, parotid fascia, the masseteric fascia anterior to the parotid gland, the platysma fascia encircling the modiolus at the oral commissure, and the fascia covering the mastoid process. These fibers converge at and around the apex of the modiolus(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eUltrasound Scanning\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eThe transducer is positioned at the intersection of the mandibular body’s lateral oblique line and a vertical line passing through the lateral canthus, oriented perpendicular to the lateral oblique line of the mandible. This placement allows visualization of the risorius muscle origin as a thin, hypoechoic band(Fig.\u0026nbsp;18). Scanning along the long axis of the risorius towards the oral commissure with slow probe movement reveals the muscle insertion at the modiolus (Fig.\u0026nbsp;19).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e.\u003cb\u003e2.6 Buccinator Muscle\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eAnatomy\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eThe buccinator muscle is a thin, quadrilateral muscle located in the buccal region between the maxilla and mandible. Its fibers converge toward the oral commissure, ultimately inserting into the modiolus(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eUltrasonographic Examination\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eFor scanning, the transducer is positioned at the intersection of the external oblique line of the mandible and the vertical line through the lateral canthus, with its orientation perpendicular to the external oblique line. This placement allows clear visualization of the buccinator’s course(Fig.\u0026nbsp;20). Subsequently, the probe is slowly advanced along the longitudinal axis of the muscle fibers toward the oral commissure, enabling observation of the buccinator’s insertion at the modiolus (Fig.\u0026nbsp;21).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e2.7 Platysma Muscle\u003c/h2\u003e\u003cp\u003e\u003cstrong\u003eAnatomy\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eThe platysma, an integral component of the orbicularis oris complex, comprises distinct regions including the mandibular, labial, and modiolus portions. Within the modiolus region, most platysma fibers converge posterior-laterally to the depressor anguli oris muscle at the posterior lip, ultimately inserting at the apex of the modiolus within its superficial layer. A small subset of fine fibers terminates directly at the cheek skin or mucosa(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eUltrasonographic Examination\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eDuring ultrasound examination, the transducer is positioned obliquely at the intersection of the lateral mandibular line and the anterior border of the masseter muscle, allowing clear visualization of the transverse section of the mandibular portion of the platysma(Fig.\u0026nbsp;22). The probe is then slowly advanced toward the oral commissure along the muscle’s long axis, revealing progressive thinning of the platysma and its termination at the modiolus(Fig.\u0026nbsp;23).\u003c/p\u003e\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study, grounded in comprehensive anatomical knowledge, systematically investigated the ultrasonographic examination methods of the modiolus and its surrounding facial expression muscles. By integrating multi-angle, multi-layered sectional scanning with three-dimensional imaging techniques, we achieved detailed sectional visualization and 3D reconstruction of the modiolus, thereby addressing a notable gap in ultrasonographic research on this structure. These findings provide robust imaging support for its clinical application. Furthermore, this technique offers reliable imaging guidance for ultrasound-assisted facial rejuvenation procedures(\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e), assessment of facial muscle function recovery in patients with facial paralysis(\u003cspan additionalcitationids=\"CR17\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e–\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e), and preoperative and postoperative evaluation in reconstructive surgeries involving the modiolus(\u003cspan additionalcitationids=\"CR20\" citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e–\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e). Moving forward, we aim to strengthen interdisciplinary collaboration with clinical departments to promote and further develop the clinical utility of high-frequency ultrasonography for modiolus assessment.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eHigh-frequency ultrasound provides a reliable and noninvasive method for detailed assessment of the modiolus and adjacent mimetic muscles, offering potential applications in both anatomical research and clinical practice.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eMin Pan, Zhansen E: Jointly conceived the study and approved the manuscriptHancai Luo: Oversaw the overall management of the study and approved the manuscriptPuchen Peng: Collected data and drafted the manuscriptHongwei Gao, Lingeng Chen, Ruodan Lan, Haifen Liao: Recruited volunteers and coordinated the work\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003e--- KH-Y, SE -Y I-OJ-W, H -C, S -G et al - Discovery of the Ligament of Modiolus: Anatomical Insights and Clinical. D \u0026ndash;\u0026thinsp;7701756. (\u0026ndash;\u0026thinsp;1432\u0026ndash;5241 (Electronic)):\u0026ndash; 2552\u0026ndash;2555\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eS S. Gray\u0026rsquo;s Anatomy: The Anatomical Basis of Clinical Practice. 42 ed. London: Elsevier; (2020)\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLiu S, Cong L, Pongprutthipan M, Lee W, Luo X, Han X et al (2023) Use of LetibotulinumtoxinA for Aesthetic Treatment of Asians: A Consensus. Aesthet Surg J 43(11):Np962\u0026ndash;np74\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWT -W KV-C, --- I-O, O -N, HC -C V-R et al - Lip Sonoanatomy and Relevance to Aesthetic Filler Injections: A Pictorial Review. D \u0026ndash;\u0026thinsp;101130964. (\u0026ndash;\u0026thinsp;1473\u0026ndash;2165 (Electronic)):\u0026ndash; e70164.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eStandring S (ed) (2020) Gray's Anatomy: The Anatomical Basis of Clinical Practice, 42 edn. Elsevier, London\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eJain P, Rathee M, Anatomy (2025) Head and Neck, Orbicularis Oris Muscle. StatPearls. Treasure Island (FL): StatPearls Publishing Copyright \u0026copy; 2025. StatPearls Publishing LLC.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDPD -D, AO -F PH-L - Anatomy, Head and Neck: Levator Anguli Oris Muscle\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eA -H-P, KW -L, HJ -L, YJ -C, KS -H, --- I-O et al - Clinical anatomy considerations on the muscular and vascular components of the. D \u0026ndash;\u0026thinsp;8809128. (\u0026ndash;\u0026thinsp;1098\u0026ndash;2353 (Electronic)):\u0026ndash; 1142\u0026ndash;9\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWT -W KV-C, --- I-O, HC -C, LR -C, CH -K, - Ultrasound Imaging of the Facial Muscles and Relevance with Botulinum Toxin. D \u0026ndash;\u0026thinsp;101530765. (\u0026ndash;\u0026thinsp;2072\u0026ndash;6651 (Electronic)):T \u0026ndash; epublish.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003e--- YJ-C, YJ -W I-O, HJ -L, KW -L, YC -G et al - Three-Dimensional Evaluation of the Depressor Anguli Oris and Depressor Labii. D \u0026ndash;\u0026thinsp;9707469. (\u0026ndash;\u0026thinsp;1527-330X (Electronic)):\u0026ndash; NP456\u0026ndash;NP61\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003e\u0026Ouml; -E, A -B\u0026Ouml; MS-T (2020) - Anatomical Evaluation of Zygomaticus Major Muscle With Relation to Orbicularis. - J Craniofac Surg ;31(6):1844\u0026ndash;1847 doi: 101097/SCS0000000000006396. (\u0026ndash;\u0026thinsp;1536\u0026ndash;3732 (Electronic)):\u0026ndash; 1844\u0026ndash;7\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAM -G, Y -AK, - Anatomy, Head and Neck, Risorius Muscle\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003e- M-RP-J, Anatomy Head and Neck: Buccinator Muscle\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003e--- R-V-B, --- I-O I-OS-D, A -N P-B et al (2025) - Best Practices for the Use of High-Frequency Ultrasound to Guide Esthetic Filler. - Diagnostics (Basel). ;15(7):921 doi: 103390/diagnostics15070921. (\u0026ndash;\u0026thinsp;2075\u0026ndash;4418 (Print)):T \u0026ndash; epublish\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eUS -U, M -P, F -S, M -G, --- I-O, inventors- Use of Minimal Amounts of Hyaluronidase in the Ultrasound-Guided Treatment of\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGF -V, M -P, M -F, HJ -C, O -G -L \u0026ndash;\u0026thinsp;3D-Ultrasonography for evaluation of facial muscles in patients with chronic. D \u0026ndash;\u0026thinsp;101088673. (\u0026ndash;\u0026thinsp;1472\u0026ndash;6815 (Print)):\u0026ndash; 4\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eO -G-L M-S GF -V. - Ultrasound echomyography of facial muscles in diagnosis and follow-up of facial. D \u0026ndash;\u0026thinsp;9715169. (\u0026ndash;\u0026thinsp;1532\u0026ndash;2130 (Electronic)):\u0026ndash; 666\u0026ndash;670\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHJ -G NV-A, JP -K, S -P, JP -VD (2013) - Quantitative facial muscle ultrasound: feasibility and reproducibility. - Muscle Nerve,. ;48(3):375\u0026thinsp;\u0026ndash;\u0026thinsp;80 doi: 101002/mus23769 Epub 2013 Jul 27. (\u0026ndash;\u0026thinsp;1097\u0026ndash;4598 (Electronic)):\u0026ndash; 375\u0026ndash;80\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003e--- I-O Y-L, H -M M-S, B -L, Y -W et al - Reconstruction of Muscles in Patients with Macrostomia. D \u0026ndash;\u0026thinsp;101757922. (\u0026ndash;\u0026thinsp;2689\u0026ndash;3622 (Electronic)):\u0026ndash; 289\u0026ndash;94\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eH -Z L-Z, D -S, D -R, Y -C, J -Z et al - Transverse facial cleft (macrostomia) repair: Modification of a traditional. D \u0026ndash;\u0026thinsp;101264239. (\u0026ndash;\u0026thinsp;1878\u0026thinsp;\u0026ndash;\u0026thinsp;0539 (Electronic)):\u0026ndash; 2041\u0026ndash;8\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003e--- I-O K-S, J -O M-S, Y -A, A -N et al - Free-flap reconstruction for full-thickness oral defects involving the oral. D \u0026ndash;\u0026thinsp;8309230. (\u0026ndash;\u0026thinsp;1098\u0026ndash;2752 (Electronic)):\u0026ndash; 553\u0026ndash;560\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"high-frequency ultrasound, modiolus, three-dimensional ultrasound imaging, facial expression muscles, tomographic ultrasound images","lastPublishedDoi":"10.21203/rs.3.rs-7379927/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7379927/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eObjectives: \u003c/strong\u003eThis study aimed to investigate the modiolus in healthy adults using high-frequency ultrasound, establish standardized scanning protocols, and clearly delineate the two- and three-dimensional sonographic features of the modiolus and its associated facial muscles.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods: \u003c/strong\u003eHealthy adult volunteers were examined using a Philips ultrasound system equipped with high-frequency linear and broadband linear transducers. Bilateral scans of the modiolus and adjacent facial muscles were performed to determine optimal scanning approaches and characterize the sonographic appearances in both two- and three-dimensional modalities.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults: \u003c/strong\u003eHigh-frequency ultrasound, with its superior soft tissue resolution, enabled clear visualization of the modiolus and related facial expression muscles. The scanning protocol for this anatomical region was successfully established, and its typical sonographic features were described. The findings indicate that high-frequency ultrasound is a reliable imaging tool for defining the ultrasonographic anatomy of the oral commissure modiolus region.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions: \u003c/strong\u003eHigh-frequency ultrasound provides detailed anatomical visualization of the modiolus and associated facial muscles and may serve as an important reference for clinical and research applications involving the lower facial region.\u003c/p\u003e","manuscriptTitle":"Two- and Three-Dimensional Ultrasonographic Characterization of the Modiolus and Adjacent Facial Muscles in Healthy Adults","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-09-03 12:07:42","doi":"10.21203/rs.3.rs-7379927/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"aab4fae4-8232-4165-809a-4596e83214e6","owner":[],"postedDate":"September 3rd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-09-07T14:08:24+00:00","versionOfRecord":[],"versionCreatedAt":"2025-09-03 12:07:42","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7379927","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7379927","identity":"rs-7379927","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}