Topographic Anatomy of the Recurrent Motor Branch of the Median Nerve

Topographic Anatomy of the Recurrent Motor Branch of the Median Nerve | 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 Topographic Anatomy of the Recurrent Motor Branch of the Median Nerve Serdar DUZGUN, Mehmet Orcun AKKURT, Nihat YIGIT This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6188396/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 İntroduction: The recurrent motor branch (RMD) of the median nerve is a critical anatomical structure that is susceptible to injury during surgery. This study aims to provide surgical guidance to prevent RMD damage in carpal tunnel syndrome (CTS) surgery by detailing the topographic anatomy of the median nerve. Materials and Methods This study included 58 patients (59 hands) who underwent surgery for carpal tunnel syndrome between 2020 and 2022. All procedures were performed using an open incision technique, and the topographic anatomy of the RMD was mapped by measuring its distances from the first and third metacarpal heads and the radial styloid process. Additionally, the relationship between the motor branch and the transverse carpal ligament was evaluated according to the Lanz classification. Surgical success was assessed using the Boston Carpal Tunnel Questionnaire (BCTQ). Results The mean distance of the RMD from the first metacarpal head was 39.7 mm, from the third metacarpal head was 50.2 mm, and from the radial styloid process was 59.4 mm. According to the Lanz classification, 67% of patients had an extraligamentous course, 25% had a subligamentous course, and 8% had a transligamentous course. No cases of wound dehiscence, hematoma, or infection were observed postoperatively. BCTQ results demonstrated significant improvements in symptom severity and functional status following surgery. Conclusion Our study highlights the importance of using bony reference points to preserve the recurrent motor branch of the median nerve during surgery. Mapping the RMD can help surgeons minimize surgical complications. Median nerve recurrent motor branch carpal tunnel syndrome surgical anatomy Lanz classification Figures Figure 1 İntroduction Compression neuropathies are disorders characterized by pain, numbness, or functional loss due to the compression of peripheral nerves by surrounding anatomical structures[ 1 ]. The most common compression neuropathy is carpal tunnel syndrome (CTS), which occurs as a result of median nerve compression[ 2 ]. The prevalence of CTS in the general population ranges between 0.6% and 3.4%[ 3 ]. It has been reported that carpal tunnel syndrome predominantly affects women, with an average diagnosis age of approximately 50 years. However, these data inherently contain a certain degree of bias, as they are based on patients who self-report their symptoms or are referred to neurophysiological laboratories or clinics[ 4 ]. In Southern Sweden, a survey study conducted on 3,000 randomly selected individuals from the general population found that the prevalence of carpal tunnel syndrome in women was approximately four times higher than in men (5.1% vs. 1.3%). Moreover, the highest prevalence was observed in elderly women aged 65–74 years.[ 5 ] Various surgical approaches are currently used for carpal tunnel decompression, including open surgery, limited incision techniques, and endoscopic methods. All three methods are applied in clinical practice[ 6 ]. It has been reported that the recurrent motor branch exhibits various anatomical variations. Hurwitz described that the thenar motor branch may follow an abnormal course and that it is associated with hypertrophic muscle tissue over the distal transverse carpal ligament[ 7 ]. Green and Morgan reported that in 93% of cases where muscle tissue was found covering the transverse carpal ligament, an abnormal motor branch was identified[ 8 ]. The aim of our study is to reveal the topographic anatomy of the median nerve and provide guidance to prevent recurrent motor branch injury during surgery. Materials and Methods This study was designed in accordance with the Helsinki Declaration. It was approved by the Ethics Committee of Anadolu Health Center (ASM-EK-23/235), and informed consent was obtained from all patients. A total of 58 patients (59 hands) who underwent surgery for carpal tunnel syndrome (CTS) at Anadolu Health Center Hospital between January 2020 and September 2022 were included in the study. All surgical procedures were performed by an experienced plastic surgeon using an open incision technique. Preoperatively, anatomical markers were placed on the operated hand. A 4 cm curved incision was made starting from the palmar region and extending towards the wrist. After releasing the transverse carpal ligament, the recurrent motor branch in the thenar region was dissected and identified (Figure 1). To analyze its topography and mapping, the distances of the recurrent motor branch to three anatomical landmarks—the first metacarpal head, the third metacarpal head, and the radial styloid process—were measured in all patients using the same type of ruler in millimeters. Additionally, its position relative to the transverse carpal ligament was classified according to the Lanz classification. The Boston Carpal Tunnel Syndrome Questionnaire (BCTQ) is a well-established tool in the literature that provides insight into surgical success[9]. The questionnaire was administered preoperatively during surgical preparation and postoperatively at the third month to assess surgical outcomes. During the postoperative period, wound dressing was recommended every other day for 15 days. Apart from avoiding water contact during the healing process, no additional restrictions were imposed. All patients had their sutures removed on postoperative day 15 after outpatient clinic evaluations. Results A total of 22 patients underwent surgery under sedoanalgesia, while 36 patients were operated on under local anesthesia. The distribution of the surgical side was as follows: 41 surgeries on the right hand, 18 on the left hand, and 1 patient underwent bilateral surgery. No cases of wound dehiscence, hematoma, or infection were observed in the postoperative period. The distances of the recurrent motor branch to the first metacarpal head, third metacarpal head, and radial styloid process were measured and recorded for each patient. The mean distances were found to be: First metacarpal head: 39.7 mm Third metacarpal head: 50.2 mm Radial styloid process: 59.4 mm (Table 1) According to the Lanz classification, the relationship of the recurrent motor branch with the transverse carpal ligament was evaluated, and it was found that in 40 patients (67%), the motor branch was extraligamentous, in 15 patients (25%), it was subligamentous, and in 4 patients (8%), it was transligamentous (Table 2). In patients who completed the Boston Carpal Tunnel Syndrome Questionnaire, the mean preoperative symptom severity score was 40±3, the mean preoperative functional status score was 37±3, the mean postoperative symptom severity score was 16±2, and the mean postoperative functional status score was 14±2 (Table 3). Statistical Analysis: The distribution data of the median nerve were analyzed using the Student's t-test. The t-score was calculated as 1.6314, and the two-tailed p-value was 0.2056. Discussion Carpal tunnel syndrome is the most common compression neuropathy of the upper extremity. Increased pressure within the carpal tunnel (≥ 32 mm Hg) leads to arterial ischemia of the median nerve, resulting in nerve damage. Nocturnal pain, paresthesia, and progressive deterioration of motor skills are common symptoms. The carpal tunnel is a fibro-osseous canal located on the palmar side of the wrist. It is covered by the transverse carpal ligament, through which the median nerve and flexor tendons pass. The motor branch of the median nerve emerges just distal to and beneath the flexor retinaculum. To date, many studies have attempted to explain the anatomical positioning of the motor branch of the median nerve in relation to the transverse carpal ligament. The first classification of the recurrent motor branch based on its relationship with the transverse carpal ligament was introduced into the literature by Poisel et al. in a 1974 study. In this study, 46% of cases were found to have an extraligamentous course, 31% were subligamentous, and 23% were transligamentous.[ 10 ]. Later, in 1977, Lanz et al. conducted a study on 246 hands, examining the positioning of the recurrent motor branch in relation to the transverse carpal ligament. The results showed that 46% of cases were extraligamentous, 31% were subligamentous, and 23% were transligamentous. In the same study, Lanz also introduced the classification system that would later be known as the Lanz classification .[ 11 ]. Similarly, in a study conducted by Akkurt et al. in 2020, the most common positioning of the recurrent motor branch was found to be extraligamentous in 57% of cases. [ 12 ]. In our study, the most common positioning of the recurrent motor branch was also found to be extraligamentous at 67%, followed by subligamentous at 25% and transligamentous at 8%. In addition to these studies, research has also been conducted on the relationship between the recurrent motor branch and surrounding muscle groups. Jegal et al., in 2018, examined the relationship between the muscles covering the distal transverse carpal ligament and the thenar branch of the median nerve.[ 13 ]. Sacks et al. (2007) investigated the relationship between the recurrent motor branch and the superficial palmar arch [ 14 ]. Elsaftawy et al. (2013) examined the variations of the recurrent motor branch of the median nerve in 20 cadaveric dissections and investigated potential injuries during decompression.[ 15 ]. The primary objective of these studies is to minimize injuries to the recurrent motor branch that may occur during the treatment of patients with carpal tunnel syndrome. The Boston Carpal Tunnel Questionnaire (BCTQ) is a crucial non-invasive tool for evaluating symptom severity and functional status in patients with carpal tunnel syndrome. It is administered both preoperatively and postoperatively, providing valuable insight into surgical outcomes. In a study conducted by Alimohammadi et al. (2020) on 152 patients, a significant improvement in functional status scores was observed following BCTQ assessments conducted preoperatively, at the second postoperative week, and at the sixth month.[ 16 ]. Similarly, in another study conducted by Lusa et al. (2024), a significant improvement was demonstrated in both symptom severity and functional recovery in patients evaluated postoperatively. [ 17 ]. Unlike these studies, Frank Chen et al. (2023) investigated whether the BCTQ alone is sufficient for determining the necessity of surgery. Their findings suggest that the BCTQ should not be used as the sole criterion for surgical decision-making.[ 18 ]. In our study, the analysis of preoperative and postoperative survey results indicates a positive improvement in patients following surgery. The primary distinction of our study from previous research lies in the reference to bony structures. A review of the literature reveals that the classification and variation of the recurrent motor branch have predominantly been based on soft tissue structures (muscles, tendons) and the transverse carpal ligament. However, it should be noted that these structures exhibit anatomical variations among individuals. In contrast, bony structures show minimal interindividual variability, making them a more reliable reference point. Therefore, mapping the recurrent motor branch based on bony landmarks provides a more consistent anatomical framework. One of the limitations of our study is that this mapping was conducted exclusively in open surgery. It was not assessed in other surgical approaches, such as endoscopic or mini-open techniques. Conclusion Detailed topographic studies of specific surgical regions help surgeons identify critical technical points, facilitating smoother procedures and reducing the risk of complications. This study highlights the variations of the recurrent motor branch of the median nerve in open carpal tunnel surgeries and provides insights into its topographic anatomy. By doing so, it serves as a guide to prevent recurrent motor branch injury during surgery. Declarations Author Contribution Serdar DUZGUN: conceptualized the study and designed the methodology. Serdar DUZGUN: contributed to the interpretation of the results. Mehmet Orcun AKKURT: collected the data and performed the initial analysis. Nihat YIGIT: drafted the manuscript. All authors reviewed, edited, and approved the final manuscript References S. H. Kozin, “The anatomy of the recurrent branch of the median nerve,” J. Hand Surg. Am. , vol. 23, no. 5, pp. 852–858, 1998, doi: 10.1016/S0363-5023(98)80162-7. B. M. Henry et al. , “The prevalence of anatomical variations of the median nerve in the carpal tunnel: A systematic review and meta-analysis,” PLoS One , vol. 10, no. 8, pp. 1–18, 2015, doi: 10.1371/journal.pone.0136477. R. S. Wilkins RH, “Entrapment neuropathies,” Princ. Neurosurgery. Int. ed , 1996. A. P. Panchal and M. A. Trzeciak, “The clinical application of Kaplan’s cardinal line as a surface marker for the superficial palmar arch,” Hand , vol. 5, no. 2, pp. 155–159, 2010, doi: 10.1007/s11552-009-9229-0. L. Padua et al. , “Carpal tunnel syndrome: clinical features, diagnosis, and management,” Lancet Neurol. , vol. 15, no. 12, pp. 1273–1284, 2016, doi: 10.1016/S1474-4422(16)30231-9. P. T. Kim, H. J. Lee, T. G. Kim, and I. H. Jeon, “Current approaches for carpal tunnel syndrome,” CiOS Clin. Orthop. Surg. , vol. 6, no. 3, pp. 253–257, 2014, doi: 10.4055/cios.2014.6.3.253. P. J. Hurwitz, “Variations in the Course of the Thenar Motor Branch of the Median Nerve,” J. Hand Surg. (British Eur. Vol. , vol. 21, no. 3, pp. 344–346, 1996, doi: 10.1016/S0266-7681(05)80198-6. D. P. Green and J. P. Morgan, “Correlation Between Muscle Morphology of the Transverse Carpal Ligament and Branching Pattern of the Motor Branch of Median Nerve,” J. Hand Surg. Am. , vol. 33, no. 9, pp. 1505–1511, 2008, doi: 10.1016/j.jhsa.2008.05.025. C. M. Forcelini et al. , “Boston Carpal Tunnel Questionnaire and Severity of Carpal Tunnel Syndrome,” J. Clin. Neuromuscul. Dis. , vol. 23, no. 4, pp. 183–188, 2022, doi: 10.1097/CND.0000000000000409. S. Poisel, “Ursprung Und Verlauf Des Ramus Muscularis Des Nervus Digitalis Palmaris Communis I (N. Medianus),” Chir. Prax. , vol. 18, no. 3, pp. 471–474, 1974. U. Lanz, “Anatomical variations of the median nerve in the carpal tunnel,” J. Hand Surg. Am. , vol. 2, no. 1, pp. 44–53, 1977, doi: 10.1016/S0363-5023(77)80009-9. M. O. Akkurt, S. Düzgün, A. Ateş, and Y. U. Yaradilmiş, “Comparison of two approaches for carpal tunnel release: Extended versus mini-open technique,” Jt. Dis. Relat. Surg. , vol. 31, no. 1, pp. 50–55, 2020, doi: 10.5606/ehc.2020.71250. M. Jegal, S. J. Woo, H. Il Lee, J. W. Shim, W. J. Shin, and M. J. Park, “Anatomical relationships between muscles overlying distal transverse carpal ligament and Thenar motor branch of the median nerve,” CiOS Clin. Orthop. Surg. , vol. 10, no. 1, pp. 89–93, 2018, doi: 10.4055/cios.2018.10.1.89. J. M. Sacks, Y. R. Kuo, K. Mclean, R. Wollstein, and W. P. A. Lee, “Anatomical relationships among the median nerve thenar branch, superficial palmar arch, and transverse carpal ligament,” Plast. Reconstr. Surg. , vol. 120, no. 3, pp. 713–718, 2007, doi: 10.1097/01.prs.0000270305.37677.e7. A. Elsaftawy, B. Gworys, J. Jablecki, and T. Szajerka, “Dangerous anatomic varieties of recurrent motor branch of median nerve,” Pol. Prz. Chir. Polish J. Surg. , vol. 85, no. 8, pp. 419–423, 2013, doi: 10.2478/pjs-2013-0064. E. Alimohammadi, S. R. Bagheri, H. Hadidi, P. Rizevandi, and A. Abdi, “Carpal tunnel surgery: Predictors of clinical outcomes and patients’ satisfaction,” BMC Musculoskelet. Disord. , vol. 21, no. 1, pp. 1–8, 2020, doi: 10.1186/s12891-020-3082-2. V. Lusa, T. V. Karjalainen, M. Pääkkönen, T. J. Rajamäki, and K. Jaatinen, “Surgical versus non-surgical treatment for carpal tunnel syndrome,” Cochrane Database Syst. Rev. , vol. 2024, no. 1, 2024, doi: 10.1002/14651858.CD001552.pub3. F. R. Chen et al. , “Boston Carpal Tunnel Questionnaire Scores Alone Do Not Predict Surgical Intervention for Patients With Carpal Tunnel Syndrome,” Hand , vol. 18, no. 1_suppl, pp. 71S-76S, 2023, doi: 10.1177/15589447211072226. Tables Tables 1 to 3 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Table123.docx Cite Share Download PDF Status: Posted Version 1 posted 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. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-6188396","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":433028802,"identity":"bf31dff1-085a-4da5-bf51-dc7c5ae26f10","order_by":0,"name":"Serdar DUZGUN","email":"","orcid":"","institution":"İstanbul Anadolu Health Center","correspondingAuthor":false,"prefix":"","firstName":"Serdar","middleName":"","lastName":"DUZGUN","suffix":""},{"id":433028803,"identity":"16fe415b-fef8-4fcd-b42c-2e3f8697f3a9","order_by":1,"name":"Mehmet Orcun AKKURT","email":"","orcid":"","institution":"Ankara Sincan Training and Research Hospital","correspondingAuthor":false,"prefix":"","firstName":"Mehmet","middleName":"Orcun","lastName":"AKKURT","suffix":""},{"id":433028804,"identity":"cff44e56-7489-44e7-8349-4b6a6caf8507","order_by":2,"name":"Nihat YIGIT","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA50lEQVRIiWNgGAWjYDACZh4QKcHAxsB+8AGQxcNHlJYDIC1sPMkGIC1shK0BawECNgYzCQhNAJiz8x78/LHNwq5PviGt8muOnQwbA/PDRzfwaLFs5kuWONgmkdzGxnjstuy2ZKDD2IyNc/BoMTjMYwDWwsbGkHZbchszUAsPmzQBLcY/oFrMiiW31ROlxQxkix1IC+PHbYeJ02Jx5pxEAhtbTrI047bjPGzMhPxy/ozxjYqyOnv55uMHP/7cVm3Pz9788DE+LWDAyMaQ2MAASwnMhJSDwR8Ge7DWH0SpHgWjYBSMgpEGAF8EP/GKXjA9AAAAAElFTkSuQmCC","orcid":"","institution":"Ankara Sincan Training and Research Hospital","correspondingAuthor":true,"prefix":"","firstName":"Nihat","middleName":"","lastName":"YIGIT","suffix":""}],"badges":[],"createdAt":"2025-03-09 11:38:08","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6188396/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6188396/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":79327336,"identity":"3a929e78-b70d-4b6c-95b7-72492f77be24","added_by":"auto","created_at":"2025-03-27 05:47:20","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":507510,"visible":true,"origin":"","legend":"\u003cp\u003eOpen Incision for Carpal Tunnel Syndrome and Dissection of the Recurrent Motor Branch\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003eFig.1a–Fig. 1c\u003c/strong\u003e: Preoperative marking of \u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;anatomical landmarks (HOH: \u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;Hook of Hamate, RMN: \u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;Recurrent Motor Nerve, MDN: \u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;Median Digital Nerve, UDN: \u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;Ulnar Digital Nerve, TCL: \u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;Transverse Carpal Ligament) and skin incision.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eFig. 1b–Fig. 1d\u003c/strong\u003e: Dissection of the recurrent \u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;motor branch.\u003c/li\u003e\n\u003c/ul\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6188396/v1/222a1c22025de5f8040cf9f0.png"},{"id":81236859,"identity":"351e147f-e5f3-48a8-aeeb-e979d8f56f7e","added_by":"auto","created_at":"2025-04-23 20:09:13","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":801718,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6188396/v1/ede497f7-db8f-4c0d-9d92-1014ed91efa8.pdf"},{"id":79326830,"identity":"c897a0c9-4a78-4ae2-841a-ab63bb30b8e5","added_by":"auto","created_at":"2025-03-27 05:39:22","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":27551,"visible":true,"origin":"","legend":"","description":"","filename":"Table123.docx","url":"https://assets-eu.researchsquare.com/files/rs-6188396/v1/b00a50ad16c7e5b7736db727.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Topographic Anatomy of the Recurrent Motor Branch of the Median Nerve","fulltext":[{"header":"İntroduction","content":"\u003cp\u003eCompression neuropathies are disorders characterized by pain, numbness, or functional loss due to the compression of peripheral nerves by surrounding anatomical structures[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The most common compression neuropathy is carpal tunnel syndrome (CTS), which occurs as a result of median nerve compression[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. The prevalence of CTS in the general population ranges between 0.6% and 3.4%[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. It has been reported that carpal tunnel syndrome predominantly affects women, with an average diagnosis age of approximately 50 years. However, these data inherently contain a certain degree of bias, as they are based on patients who self-report their symptoms or are referred to neurophysiological laboratories or clinics[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. In Southern Sweden, a survey study conducted on 3,000 randomly selected individuals from the general population found that the prevalence of carpal tunnel syndrome in women was approximately four times higher than in men (5.1% vs. 1.3%). Moreover, the highest prevalence was observed in elderly women aged 65\u0026ndash;74 years.[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e] Various surgical approaches are currently used for carpal tunnel decompression, including open surgery, limited incision techniques, and endoscopic methods. All three methods are applied in clinical practice[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. It has been reported that the recurrent motor branch exhibits various anatomical variations. Hurwitz described that the thenar motor branch may follow an abnormal course and that it is associated with hypertrophic muscle tissue over the distal transverse carpal ligament[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Green and Morgan reported that in 93% of cases where muscle tissue was found covering the transverse carpal ligament, an abnormal motor branch was identified[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The aim of our study is to reveal the topographic anatomy of the median nerve and provide guidance to prevent recurrent motor branch injury during surgery.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cp\u003eThis study was designed in accordance with the Helsinki Declaration. It was approved by the Ethics Committee of Anadolu Health Center (ASM-EK-23/235), and informed consent was obtained from all patients. A total of 58 patients (59 hands) who underwent surgery for carpal tunnel syndrome (CTS) at Anadolu Health Center Hospital between January 2020 and September 2022 were included in the study.\u003c/p\u003e\n\u003cp\u003eAll surgical procedures were performed by an experienced plastic surgeon using an open incision technique. Preoperatively, anatomical markers were placed on the operated hand. A 4 cm curved incision was made starting from the palmar region and extending towards the wrist. After releasing the transverse carpal ligament, the recurrent motor branch in the thenar region was dissected and identified (Figure 1).\u003c/p\u003e\n\u003cp\u003eTo analyze its topography and mapping, the distances of the recurrent motor branch to three anatomical landmarks\u0026mdash;the first metacarpal head, the third metacarpal head, and the radial styloid process\u0026mdash;were measured in all patients using the same type of ruler in millimeters. Additionally, its position relative to the transverse carpal ligament was classified according to the Lanz classification.\u003c/p\u003e\n\u003cp\u003eThe Boston Carpal Tunnel Syndrome Questionnaire (BCTQ) is a well-established tool in the literature that provides insight into surgical success[9]. The questionnaire was administered preoperatively during surgical preparation and postoperatively at the third month to assess surgical outcomes.\u003c/p\u003e\n\u003cp\u003eDuring the postoperative period, wound dressing was recommended every other day for 15 days. Apart from avoiding water contact during the healing process, no additional restrictions were imposed. All patients had their sutures removed on postoperative day 15 after outpatient clinic evaluations.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eA total of 22 patients underwent surgery under sedoanalgesia, while 36 patients were operated on under local anesthesia. The distribution of the surgical side was as follows: 41 surgeries on the right hand, 18 on the left hand, and 1 patient underwent bilateral surgery.\u003c/p\u003e\n\u003cp\u003eNo cases of wound dehiscence, hematoma, or infection were observed in the postoperative period. The distances of the recurrent motor branch to the first metacarpal head, third metacarpal head, and radial styloid process were measured and recorded for each patient.\u003c/p\u003e\n\u003cp\u003eThe mean distances were found to be:\u003c/p\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003eFirst metacarpal head: 39.7 mm\u003c/li\u003e\n \u003cli\u003eThird metacarpal head: 50.2 mm\u003c/li\u003e\n \u003cli\u003eRadial styloid process: 59.4 mm (Table 1)\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eAccording to the Lanz classification, the relationship of the recurrent motor branch with the transverse carpal ligament was evaluated, and it was found that in 40 patients (67%), the motor branch was extraligamentous, in 15 patients (25%), it was subligamentous, and in 4 patients (8%), it was transligamentous (Table 2).\u003c/p\u003e\n\u003cp\u003eIn patients who completed the Boston Carpal Tunnel Syndrome Questionnaire, the mean preoperative symptom severity score was 40\u0026plusmn;3, the mean preoperative functional status score was 37\u0026plusmn;3, the mean postoperative symptom severity score was 16\u0026plusmn;2, and the mean postoperative functional status score was 14\u0026plusmn;2 (Table 3).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical Analysis:\u003c/strong\u003e The distribution data of the median nerve were analyzed using the Student\u0026apos;s t-test. The t-score was calculated as 1.6314, and the two-tailed p-value was 0.2056.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eCarpal tunnel syndrome is the most common compression neuropathy of the upper extremity. Increased pressure within the carpal tunnel (\u0026ge;\u0026thinsp;32 mm Hg) leads to arterial ischemia of the median nerve, resulting in nerve damage. Nocturnal pain, paresthesia, and progressive deterioration of motor skills are common symptoms.\u003c/p\u003e \u003cp\u003eThe carpal tunnel is a fibro-osseous canal located on the palmar side of the wrist. It is covered by the transverse carpal ligament, through which the median nerve and flexor tendons pass. The motor branch of the median nerve emerges just distal to and beneath the flexor retinaculum.\u003c/p\u003e \u003cp\u003eTo date, many studies have attempted to explain the anatomical positioning of the motor branch of the median nerve in relation to the transverse carpal ligament. The first classification of the recurrent motor branch based on its relationship with the transverse carpal ligament was introduced into the literature by Poisel et al. in a 1974 study. In this study, 46% of cases were found to have an extraligamentous course, 31% were subligamentous, and 23% were transligamentous.[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Later, in 1977, Lanz et al. conducted a study on 246 hands, examining the positioning of the recurrent motor branch in relation to the transverse carpal ligament. The results showed that 46% of cases were extraligamentous, 31% were subligamentous, and 23% were transligamentous. In the same study, Lanz also introduced the classification system that would later be known as the \u003cb\u003eLanz classification\u003c/b\u003e.[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Similarly, in a study conducted by Akkurt et al. in 2020, the most common positioning of the recurrent motor branch was found to be extraligamentous in 57% of cases. [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. In our study, the most common positioning of the recurrent motor branch was also found to be extraligamentous at 67%, followed by subligamentous at 25% and transligamentous at 8%.\u003c/p\u003e \u003cp\u003eIn addition to these studies, research has also been conducted on the relationship between the recurrent motor branch and surrounding muscle groups. Jegal et al., in 2018, examined the relationship between the muscles covering the distal transverse carpal ligament and the thenar branch of the median nerve.[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Sacks et al. (2007) investigated the relationship between the recurrent motor branch and the superficial palmar arch [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Elsaftawy et al. (2013) examined the variations of the recurrent motor branch of the median nerve in 20 cadaveric dissections and investigated potential injuries during decompression.[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The primary objective of these studies is to minimize injuries to the recurrent motor branch that may occur during the treatment of patients with carpal tunnel syndrome. The Boston Carpal Tunnel Questionnaire (BCTQ) is a crucial non-invasive tool for evaluating symptom severity and functional status in patients with carpal tunnel syndrome. It is administered both preoperatively and postoperatively, providing valuable insight into surgical outcomes. In a study conducted by Alimohammadi et al. (2020) on 152 patients, a significant improvement in functional status scores was observed following BCTQ assessments conducted preoperatively, at the second postoperative week, and at the sixth month.[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Similarly, in another study conducted by Lusa et al. (2024), a significant improvement was demonstrated in both symptom severity and functional recovery in patients evaluated postoperatively. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Unlike these studies, Frank Chen et al. (2023) investigated whether the BCTQ alone is sufficient for determining the necessity of surgery. Their findings suggest that the BCTQ should not be used as the sole criterion for surgical decision-making.[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. In our study, the analysis of preoperative and postoperative survey results indicates a positive improvement in patients following surgery.\u003c/p\u003e \u003cp\u003eThe primary distinction of our study from previous research lies in the reference to bony structures. A review of the literature reveals that the classification and variation of the recurrent motor branch have predominantly been based on soft tissue structures (muscles, tendons) and the transverse carpal ligament. However, it should be noted that these structures exhibit anatomical variations among individuals. In contrast, bony structures show minimal interindividual variability, making them a more reliable reference point. Therefore, mapping the recurrent motor branch based on bony landmarks provides a more consistent anatomical framework.\u003c/p\u003e \u003cp\u003eOne of the limitations of our study is that this mapping was conducted exclusively in open surgery. It was not assessed in other surgical approaches, such as endoscopic or mini-open techniques.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eDetailed topographic studies of specific surgical regions help surgeons identify critical technical points, facilitating smoother procedures and reducing the risk of complications. This study highlights the variations of the recurrent motor branch of the median nerve in open carpal tunnel surgeries and provides insights into its topographic anatomy. By doing so, it serves as a guide to prevent recurrent motor branch injury during surgery.\u003c/p\u003e "},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eSerdar DUZGUN: conceptualized the study and designed the methodology. Serdar DUZGUN: contributed to the interpretation of the results. Mehmet Orcun AKKURT: collected the data and performed the initial analysis. Nihat YIGIT: drafted the manuscript. All authors reviewed, edited, and approved the final manuscript\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eS. H. Kozin, \u0026ldquo;The anatomy of the recurrent branch of the median nerve,\u0026rdquo; \u003cem\u003eJ. Hand Surg. Am.\u003c/em\u003e, vol. 23, no. 5, pp. 852\u0026ndash;858, 1998, doi: 10.1016/S0363-5023(98)80162-7.\u003c/li\u003e\n\u003cli\u003eB. M. Henry \u003cem\u003eet al.\u003c/em\u003e, \u0026ldquo;The prevalence of anatomical variations of the median nerve in the carpal tunnel: A systematic review and meta-analysis,\u0026rdquo; \u003cem\u003ePLoS One\u003c/em\u003e, vol. 10, no. 8, pp. 1\u0026ndash;18, 2015, doi: 10.1371/journal.pone.0136477.\u003c/li\u003e\n\u003cli\u003eR. S. Wilkins RH, \u0026ldquo;Entrapment neuropathies,\u0026rdquo; \u003cem\u003ePrinc. Neurosurgery. Int. ed\u003c/em\u003e, 1996.\u003c/li\u003e\n\u003cli\u003eA. P. Panchal and M. A. Trzeciak, \u0026ldquo;The clinical application of Kaplan\u0026rsquo;s cardinal line as a surface marker for the superficial palmar arch,\u0026rdquo; \u003cem\u003eHand\u003c/em\u003e, vol. 5, no. 2, pp. 155\u0026ndash;159, 2010, doi: 10.1007/s11552-009-9229-0.\u003c/li\u003e\n\u003cli\u003eL. Padua \u003cem\u003eet al.\u003c/em\u003e, \u0026ldquo;Carpal tunnel syndrome: clinical features, diagnosis, and management,\u0026rdquo; \u003cem\u003eLancet Neurol.\u003c/em\u003e, vol. 15, no. 12, pp. 1273\u0026ndash;1284, 2016, doi: 10.1016/S1474-4422(16)30231-9.\u003c/li\u003e\n\u003cli\u003eP. T. Kim, H. J. Lee, T. G. Kim, and I. H. Jeon, \u0026ldquo;Current approaches for carpal tunnel syndrome,\u0026rdquo; \u003cem\u003eCiOS Clin. Orthop. Surg.\u003c/em\u003e, vol. 6, no. 3, pp. 253\u0026ndash;257, 2014, doi: 10.4055/cios.2014.6.3.253.\u003c/li\u003e\n\u003cli\u003eP. J. Hurwitz, \u0026ldquo;Variations in the Course of the Thenar Motor Branch of the Median Nerve,\u0026rdquo; \u003cem\u003eJ. Hand Surg. (British Eur. Vol.\u003c/em\u003e, vol. 21, no. 3, pp. 344\u0026ndash;346, 1996, doi: 10.1016/S0266-7681(05)80198-6.\u003c/li\u003e\n\u003cli\u003eD. P. Green and J. P. Morgan, \u0026ldquo;Correlation Between Muscle Morphology of the Transverse Carpal Ligament and Branching Pattern of the Motor Branch of Median Nerve,\u0026rdquo; \u003cem\u003eJ. Hand Surg. Am.\u003c/em\u003e, vol. 33, no. 9, pp. 1505\u0026ndash;1511, 2008, doi: 10.1016/j.jhsa.2008.05.025.\u003c/li\u003e\n\u003cli\u003eC. M. Forcelini \u003cem\u003eet al.\u003c/em\u003e, \u0026ldquo;Boston Carpal Tunnel Questionnaire and Severity of Carpal Tunnel Syndrome,\u0026rdquo; \u003cem\u003eJ. Clin. Neuromuscul. Dis.\u003c/em\u003e, vol. 23, no. 4, pp. 183\u0026ndash;188, 2022, doi: 10.1097/CND.0000000000000409.\u003c/li\u003e\n\u003cli\u003eS. Poisel, \u0026ldquo;Ursprung Und Verlauf Des Ramus Muscularis Des Nervus Digitalis Palmaris Communis I (N. Medianus),\u0026rdquo; \u003cem\u003eChir. Prax.\u003c/em\u003e, vol. 18, no. 3, pp. 471\u0026ndash;474, 1974.\u003c/li\u003e\n\u003cli\u003eU. Lanz, \u0026ldquo;Anatomical variations of the median nerve in the carpal tunnel,\u0026rdquo; \u003cem\u003eJ. Hand Surg. Am.\u003c/em\u003e, vol. 2, no. 1, pp. 44\u0026ndash;53, 1977, doi: 10.1016/S0363-5023(77)80009-9.\u003c/li\u003e\n\u003cli\u003eM. O. Akkurt, S. D\u0026uuml;zg\u0026uuml;n, A. Ateş, and Y. U. Yaradilmiş, \u0026ldquo;Comparison of two approaches for carpal tunnel release: Extended versus mini-open technique,\u0026rdquo; \u003cem\u003eJt. Dis. Relat. Surg.\u003c/em\u003e, vol. 31, no. 1, pp. 50\u0026ndash;55, 2020, doi: 10.5606/ehc.2020.71250.\u003c/li\u003e\n\u003cli\u003eM. Jegal, S. J. Woo, H. Il Lee, J. W. Shim, W. J. Shin, and M. J. Park, \u0026ldquo;Anatomical relationships between muscles overlying distal transverse carpal ligament and Thenar motor branch of the median nerve,\u0026rdquo; \u003cem\u003eCiOS Clin. Orthop. Surg.\u003c/em\u003e, vol. 10, no. 1, pp. 89\u0026ndash;93, 2018, doi: 10.4055/cios.2018.10.1.89.\u003c/li\u003e\n\u003cli\u003eJ. M. Sacks, Y. R. Kuo, K. Mclean, R. Wollstein, and W. P. A. Lee, \u0026ldquo;Anatomical relationships among the median nerve thenar branch, superficial palmar arch, and transverse carpal ligament,\u0026rdquo; \u003cem\u003ePlast. Reconstr. Surg.\u003c/em\u003e, vol. 120, no. 3, pp. 713\u0026ndash;718, 2007, doi: 10.1097/01.prs.0000270305.37677.e7.\u003c/li\u003e\n\u003cli\u003eA. Elsaftawy, B. Gworys, J. Jablecki, and T. Szajerka, \u0026ldquo;Dangerous anatomic varieties of recurrent motor branch of median nerve,\u0026rdquo; \u003cem\u003ePol. Prz. Chir. Polish J. Surg.\u003c/em\u003e, vol. 85, no. 8, pp. 419\u0026ndash;423, 2013, doi: 10.2478/pjs-2013-0064.\u003c/li\u003e\n\u003cli\u003eE. Alimohammadi, S. R. Bagheri, H. Hadidi, P. Rizevandi, and A. Abdi, \u0026ldquo;Carpal tunnel surgery: Predictors of clinical outcomes and patients\u0026rsquo; satisfaction,\u0026rdquo; \u003cem\u003eBMC Musculoskelet. Disord.\u003c/em\u003e, vol. 21, no. 1, pp. 1\u0026ndash;8, 2020, doi: 10.1186/s12891-020-3082-2.\u003c/li\u003e\n\u003cli\u003eV. Lusa, T. V. Karjalainen, M. P\u0026auml;\u0026auml;kk\u0026ouml;nen, T. J. Rajam\u0026auml;ki, and K. Jaatinen, \u0026ldquo;Surgical versus non-surgical treatment for carpal tunnel syndrome,\u0026rdquo; \u003cem\u003eCochrane Database Syst. Rev.\u003c/em\u003e, vol. 2024, no. 1, 2024, doi: 10.1002/14651858.CD001552.pub3.\u003c/li\u003e\n\u003cli\u003eF. R. Chen \u003cem\u003eet al.\u003c/em\u003e, \u0026ldquo;Boston Carpal Tunnel Questionnaire Scores Alone Do Not Predict Surgical Intervention for Patients With Carpal Tunnel Syndrome,\u0026rdquo; \u003cem\u003eHand\u003c/em\u003e, vol. 18, no. 1_suppl, pp. 71S-76S, 2023, doi: 10.1177/15589447211072226.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 to 3 are available in the Supplementary Files section.\u003c/p\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":"Median nerve, recurrent motor branch, carpal tunnel syndrome, surgical anatomy, Lanz classification","lastPublishedDoi":"10.21203/rs.3.rs-6188396/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6188396/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cb\u003eİntroduction:\u003c/b\u003e\u003c/p\u003e \u003cp\u003eThe recurrent motor branch (RMD) of the median nerve is a critical anatomical structure that is susceptible to injury during surgery. This study aims to provide surgical guidance to prevent RMD damage in carpal tunnel syndrome (CTS) surgery by detailing the topographic anatomy of the median nerve.\u003c/p\u003e\u003cp\u003e\u003cb\u003eMaterials and Methods\u003c/b\u003e\u003c/p\u003e \u003cp\u003eThis study included 58 patients (59 hands) who underwent surgery for carpal tunnel syndrome between 2020 and 2022. All procedures were performed using an open incision technique, and the topographic anatomy of the RMD was mapped by measuring its distances from the first and third metacarpal heads and the radial styloid process. Additionally, the relationship between the motor branch and the transverse carpal ligament was evaluated according to the Lanz classification. Surgical success was assessed using the Boston Carpal Tunnel Questionnaire (BCTQ).\u003c/p\u003e\u003cp\u003e\u003cb\u003eResults\u003c/b\u003e\u003c/p\u003e \u003cp\u003eThe mean distance of the RMD from the first metacarpal head was 39.7 mm, from the third metacarpal head was 50.2 mm, and from the radial styloid process was 59.4 mm. According to the Lanz classification, 67% of patients had an extraligamentous course, 25% had a subligamentous course, and 8% had a transligamentous course. No cases of wound dehiscence, hematoma, or infection were observed postoperatively. BCTQ results demonstrated significant improvements in symptom severity and functional status following surgery.\u003c/p\u003e\u003cp\u003e\u003cb\u003eConclusion\u003c/b\u003e\u003c/p\u003e \u003cp\u003eOur study highlights the importance of using bony reference points to preserve the recurrent motor branch of the median nerve during surgery. Mapping the RMD can help surgeons minimize surgical complications.\u003c/p\u003e","manuscriptTitle":"Topographic Anatomy of the Recurrent Motor Branch of the Median Nerve","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-03-27 05:39:15","doi":"10.21203/rs.3.rs-6188396/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":"df52ecaf-e7a0-4887-8546-a869d8a855d3","owner":[],"postedDate":"March 27th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-04-23T20:08:56+00:00","versionOfRecord":[],"versionCreatedAt":"2025-03-27 05:39:15","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6188396","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6188396","identity":"rs-6188396","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}