Acromion-axillary Nerve Distance and Its Relation to the Humeral Length in the Prediction of the Axillary Nerve Position During the Anterolateral Deltoid-splitting Approach in the Treatment of Proximal Humerus Fractures: a Clinical Study

Acromion-axillary Nerve Distance and Its Relation to the Humeral Length in the Prediction of the Axillary Nerve Position During the Anterolateral Deltoid-splitting Approach in the Treatment of Proximal Humerus Fractures: a Clinical Study | 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 Acromion-axillary Nerve Distance and Its Relation to the Humeral Length in the Prediction of the Axillary Nerve Position During the Anterolateral Deltoid-splitting Approach in the Treatment of Proximal Humerus Fractures: a Clinical Study mehmet demirel, Cem Yıldırım, Erhan Bayram, Mehmet Ekinci, Murat Yılmaz This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-1223482/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract Background Because of the broad anatomical variation in the course of the axillary nerve, several cadaveric studies have investigated the acromion-axillary nerve distance and its association with the humeral length to predict the axillary nerve location. This study aimed to analyze the acromion-axillary nerve distance (AAND) and its relation to the arm length (AL) in patients who underwent internal plate fixation for proximal humerus fractures. Methods The present prospective study involved 37 patients (15 female, 22 male; the mean age = 51 years, age range = 19 to 76) with displaced proximal humerus fractures who were treated by open reduction and internal fixation. After anatomic reduction and fixation was achieved, the following parameters were measured in each patient before wound closure without making an extra incision or dissection: (1) the distance from the anterolateral edge of the acromion to the course of axillary nerve was recorded as the acromion-axillary nerve distance and (2) the distance from the anterolateral edge of the acromion to the lateral epicondyle of the humerus was recorded as arm length. The ratio of AAND to AL was then calculated and recorded as the axillary nerve index. Results The mean AAND was 6 ± 0.36 cm (range = 5.5–6.6), and the mean arm length was 32.91 ± 2.9 cm (range = 24–38). The mean axillary nerve ratio was 0.18 ± 0.02 (range = 0.16 to 0.23). There was a significant moderate positive correlation between AL and AAND (p = 0.006; r = 0.447). The axillary nerve location was predictable in only 18% of the patients. Conclusion During the anterolateral deltoid-splitting approach to the shoulder joint, 5.5 cm from the anterolateral edge of the acromion could be considered as a safe zone for the prevention of possible axillary nerve injury. Axillary nerve trans-deltoid approach deltoid-splitting approach iatrogenic nerve injury safe zone Figures Figure 1 Figure 2 Background In the operative treatment of proximal humerus fractures, the deltopectoral approach is still the most widely used approach for internal plate fixation. However, this traditional approach offers limited access to the posterolateral aspect of the proximal humerus that may render reduction of a retracted greater tuberosity fragment and plate placement difficult [ 1 ] Alternatively, the anterolateral deltoid-splitting approach can provide direct access and excellent visualization of the greater tuberosity and the plating area, with minimal soft-tissue dissection [ 2 , 3 ], but there is an increased risk for axillary nerve injury, accounting for 6 to 10% of all iatrogenic nerve injuries to the brachial plexus [ 4 – 8 ]. Although it is generally accepted that the axillary nerve crosses the humerus horizontally nearly 50 mm distal to the acromion in clinical practice, various anatomical studies have defined a broad range of safe zones for deltoid-splitting approaches, varying from 30 to 70 mm distally to the acromion [ 6 , 9 – 11 ]. Furthermore, it has been shown that a safe zone for a nerve may change in size as per the extremity length [ 12 ]. Because of the large anatomical variation in the course of the axillary nerve from one individual to another, several cadaveric studies have explored the acromion-axillary nerve distance and its association with the humeral length to predict the axillary nerve location [ 13 – 16 ]. Nonetheless, to the best of our knowledge, the relationship between the axillary nerve location and humeral length has not been investigated in a clinical setting to date. This study aimed to analyze the acromion-axillary nerve distance (AAND) and its relation to the arm length (AL) in patients who underwent internal plate fixation for proximal humerus fractures. The authors hypothesized that acromion-axillary nerve distance has a significant correlation with the humeral length and can be used to predict the axillary nerve location during anterolateral deltoid-splitting approach. Methods The present prospective study involved 37 patients (15 female, 22 male; the mean age = 51 years, age range = 19 to 76) with displaced proximal humerus fractures who were treated by open reduction and internal fixation at a single tertiary trauma referral center from January 2017 to May 2019. According to the Neer classification system (17), there were 15 two-part (41%), 20 three-part (54%), and two four-part (5%) humerus fractures. Inclusion criteria were patients aged > 18 years, with proximal humerus fractures without a previous history of shoulder surgery. Exclusion criteria were patients with polytrauma, pathological fracture, concomitant fracture of the same upper extremity, limb discrepancy, or congenital deformity. An informed consent was obtained from all the patients preoperatively; ethical approval was obtained from the institutional ethical committee (88-2021, 06.10.2021). Operative technique All surgical procedures were performed by a single experienced orthopedic trauma surgeon within a week of the injury, using the anterolateral deltoid-splitting approach. All the operations were performed under general anesthesia. The patients were placed in a beach-chair position, and bony landmarks were marked before making the incision. A longitudinal incision was made from the anterolateral edge of the acromion, which extended distally along the long axis of the humerus, and dissection was performed between the anterior and middle thirds of the deltoid muscle fibers. The axillary nerve was then palpated and visualized carefully. After ensuring adequate protection of the axillary nerve, the dissection was extended distally. The exposed region of the shoulder was divided into two parts by the axillary nerve. While the superior part was used for reduction of the fracture, the distal part was used for fixing the plate to the humeral shaft. Later, the fracture was reduced, and Kirschner wires were inserted for temporary fixation. The anatomic proximal humerus plate was then placed under the axillary nerve, and the rotator cuff was repaired if required. The final position was checked using fluoroscopy. The wound was closed in layers, and a drain inserted inside the subcutaneous tissue. Postoperatively, the arm was placed in a sling for controlled physical therapy. Outcome measures Within the routine steps of the planned operation, after anatomic reduction and fixation was achieved, the following parameters were measured in each patient before wound closure without making an extra incision or dissection: (1) the distance from the anterolateral edge of the acromion to the course of axillary nerve was recorded as the acromion-axillary nerve distance (Fig. 1 ), and (2) the distance from the anterolateral edge of the acromion to the lateral epicondyle of the humerus was recorded as AL [ 13 ]. The ratio of AAND to AL was then calculated and recorded as the axillary nerve index for each patient as described by Çetik et al.[ 13 ]. The correlation between AAND and AL was also investigated. Statistical Analysis All statistical analyses were performed using SPSS 25.0 software (SPSS Inc., Chicago, IL, USA). A p value of 0.05 was considered as statistically significant. Descriptive statistics were given as mean, standard deviation, percent, lowest (min) and highest (max) values. The Kolmogorov–Smirnov test was used to verify the normal distribution of the variables. The correlation between AAND and AL was evaluated using the Spearman correlation analysis in a linear regression model. The level of correlation was interpreted according to Guilford’s interpretation [ 17 ]. Results The mean AAND was 6 ± 0.36 cm (range = 5.5 to 6.6 cm), and the mean AL was 32.9 ± 2.9 cm (range = 24 to 38 cm). The mean axillary nerve index was 0.18 ± 0.02 (range = 0.16 to 0.23) (Table 1 ). A significant moderate positive correlation was identified between AL and ANND (p = 0.006; r = 0.447) (Fig. 2 ). We were able to predict the location of the axillary nerve in 18% of the patients using the regression analysis. Table 1 Demographic data of the study participants Number of the patients 37 Age (years), mean 51 (range = 17–76) Gender (Male/Female) 22/15 AAND (cm) , mean ± SD 6±0.36 cm (range = 5.5–6.6) AL (cm) , mean ± SD 32.91±2.9 cm (range = 24–38) Axillary nerve index (AAND/AL) , mean ± SD 0.18±0.02(0.16–0.23) AAND = Acromion-axillary nerve distance; AL = Arm Length; SD = Standard Deviation Discussion Although the anterolateral deltoid-splitting approach can ensure direct access and excellent visualization of the plating area in the management of proximal humerus fractures [ 2 , 3 ], there is an increased risk for axillary nerve injury, which is the most common neurological complication associated with surgery of proximal humerus fractures [ 6 , 18 , 19 ]. Accordingly, defining the safe zone for the axillary nerve is important to avoid iatrogenic injury. However, various anatomical studies have defined a broad range of safe zones for deltoid-splitting approaches, varying from 30 to 70 mm distally to the acromion [ 6 , 9 – 11 ]. Because of the broad anatomical variation in the course of the axillary nerve, the acromion-axillary nerve distance and its association with the humeral length were investigated to predict the axillary nerve location [ 13 – 16 ] in some cadaveric studies. Nonetheless, according to our review of the literature, the relationship between the axillary nerve location and humeral length has not been investigated in a clinical setting to date. The present study aimed to describe a safe area for executing the anterolateral deltoid split approach during open reduction–plate fixation for managing patients with proximal humerus fractures. We found that ANND was 6.0 ± 0.36 cm, which was moderately correlated with AL. However, ANND could be predicted according to AL in only 18% of the patients. Numerous studies have attempted to measure ANND and found significant variations with a range of 4.5 to 7.5 cm [ 10 , 13 – 15 , 20 , 21 ]. Kongcharoensombat et al. [ 14 ] calculated the mean distance of the axillary nerve from the anterolateral acromion as 6.39 cm (ranging from 4.6 to 8.2 cm), and Cetik et al. [ 13 ] found the distance of the axillary nerve from the anterolateral acromion to be 6.08 cm (ranging from 5.20 to 6.90 cm). Both previous studies observed significant correlation between the distance of the axillary nerve from the anterolateral acromion and humeral length. In contrast to the cadaveric studies of Kongcharoensombat [ 14 ] and Cetik et al. [ 13 ], the present study was conducted in a clinical setting, and all measurements were performed intraoperatively after the anatomic reduction and fixation were completed. In this regard, our study is advantageous over the existing previous cadaveric studies in the literature. While using the anterolateral approach for proximal humeral fractures, the plate should be inserted under the axillary nerve so that the nerve could be dissected carefully, and potential injury could be prevented. Also, the shortest distance should be taken into consideration during dissection to minimize the risk of probable axillary nerve injury. We measured the minimum distance of the axillary nerve to be 5.5 cm from the acromion. Hence, this distance could be considered as a safe zone according to the findings of the present study. In the study by Cetik et al. [ 13 ], this distance was measured as 5.2 cm. However, this data contradicts the findings of Kongcharoensombat et al. [ 14 ] because the axillary nerve was found located at <5 cm in 13% of the cadaver shoulders. In our study, the calculated mean axillary nerve index was lower than that given by Cetik et al. [ 13 ] and Kongcharoensombat et al. [ 21 ]. The exact prediction ratio of the location of the axillary nerve according to the humeral length of the patients was 18%, which was less than the expected value. Therefore, we believe that it would be safer to use the distance instead of the ratio. Our study has several limitations. First, the number of patients who participated in the study was less. Second, the measurements were made using a manual caliper, thereby giving room for human errors. Third, all the measurements were performed after the anatomic reduction was completed. However, in case of deformity due to proximal humerus fracture before reduction was performed during the exposure, this distance is likely to be shortened. Conclusions Evidence from this study has demonstrated that during the anterolateral deltoid-splitting approach to the shoulder joint, 5.5 cm from the anterolateral edge of the acromion could be considered as a safe zone for the prevention of possible axillary nerve injury. Predicting the location of the axillary nerve using the AL was possible in only 18% of the patients; thus, it would be safer to use the distance of 5.5 cm instead of relying on the axillary nerve index. Abbreviations AAND: Acromion-axillary nerve distance AL : Arm length Declarations Ethical approval and consent to participate This study was approved by the institutional review board of our institution and was carried out in accordance with the Declaration of Helsinki. Informed consent was obtained from all individual participants included in the study. Consent for publication Patients signed informed consent regarding publishing their data and photographs. Competing interests All authors promise that there is no competing interest to disclose. Funding Not applicable. Authors' contributions CY: Conceptualization; Data curation; Methodology; Investigation MD: Validation; Writing - original draft EB: Methodology; Formal analysis; Writing - original draft, ME: Formal analysis; Supervision; Validation; Writing - review & editing MY: Supervision; Validation Availability of data and materials The data used and/or analysed during the current study are available from the corresponding author or the first author on reasonable request. References Xie L, Zhang Y, Chen C, Zheng W, Chen H, Cai L. Deltoid-split approach versus deltopectoral approach for proximal humerus fractures: A systematic review and meta-analysis. Orthop Traumatol Surg Res. 2019;105(2):307–16. Traver JL, Guzman MA, Cannada LK, Kaar SG. Is the axillary nerve at risk during a deltoid-splitting approach for proximal humerus fractures? J Orthop Trauma. 2016;30(5):240–4. Zhang J, Moore AE, Stringer MD. Iatrogenic upper limb nerve injuries: a systematic review. ANZ J Surg. 2011;81(4):227–36. Eakin CL, Dvirnak P, Miller CM, Hawkins RJ. The relationship of the axillary nerve to arthroscopically placed capsulolabral sutures. Am J Sports Med. 1998;26(4):505–9. Lynch NM, Cofield RH, Silbert PL, Hermann RC. Neurologic complications after total shoulder arthroplasty. J Shoulder Elbow Surg. 1996;5(1):53–61. Perlmutter GS. Axillary nerve injury . Clin Orthop Relat Res. 1999(368):28–36. Smith J, Berry G, Laflamme Y, Blain-Pare E, Reindl R, Harvey E. Percutaneous insertion of a proximal humeral locking plate: an anatomic study. Injury. 2007;38(2):206–11. Tubbs RS, Tyler-Kabara EC, Aikens AC, Martin JP, Weed LL, Salter EG, Oakes WJ. Surgical anatomy of the axillary nerve within the quadrangular space. J Neurosurg. 2005;102(5):912–4. Bryan WJ, Schauder K, Tullos HS. The axillary nerve and its relationship to common sports medicine shoulder procedures. Am J Sports Med. 1986;14(2):113–6. Burkhead W Jr, Scheinberg R, Box G. Surgical anatomy of the axillary nerve. J Shoulder Elbow Surg. 1992;1(1):31–6. Duparc F, Bocquet G, Simonet J, Freger P. Anatomical basis of the variable aspects of injuries of the axillary nerve (excluding the terminal branches in the deltoid muscle). Surg Radiol Anat. 1997;19(3):127–32. Eksioglu F, Uslu M, Gudemez E, Atik OS, Tekdemir I. Reliability of the safe area for the superior gluteal nerve. Clin Orthop Relat Res. 2003;412:111–6. Cetik O, Uslu M, Acar HI, Comert A, Tekdemir I, Cift H. Is there a safe area for the axillary nerve in the deltoid muscle?: a cadaveric study. J Bone Joint Surg Am. 2006;88(11):2395–9. Kongcharoensombat W, Wattananon P. Risk of axillary nerve injury in standard anterolateral approach of shoulder: cadaveric study. Malays Orthop J. 2018;12(3):1. Rotari V, Moussallem CD, David E, Mertl P, Havet E. Position of the anterior branch of the axillary nerve in relation to the humeral bone length. Am J Orthop. 2012;41(10):452–4. Sung C-M, Roh GS, Sohn H-J, Park HB. Prediction of the location of the anterior branch of the axillary nerve, using correlations with physical factors: a cadaveric study. J Shoulder Elbow Surg. 2013;22(11):e9–16. Tredoux C, Durrheim K: Number , hypotheses & conclusions : A course in statistics for the social sciences . Cape Town . University of Cape Town Press Triguero, A, Córcoles, D, & Cuerva, MC (2014) Persistence of innovation and firm’s growth: evidence from a panel of SME and large Spanish manufacturing firms Small Business Economics 2002, 43 (4):787-804. Shaw A, Milne A, Christie J, Jenkins AM, Murie J, Ruckley C. Vascular trauma of the upper limb and associated nerve injuries. Injury. 1995;26(8):515–8. Visser CP, Coene LNJ, Brand R, Tavy DL. Nerve lesions in proximal humeral fractures. J Shoulder Elbow Surg. 2001;10(5):421–7. Kamineni S, Ankem H, Sanghavi S. Anatomical considerations for percutaneous proximal humeral fracture fixation. Injury. 2004;35(11):1133–6. Kontakis GM, Steriopoulos K, Damilakis J, Michalodimitrakis E. The position of the axillary nerve in the deltoid muscle: A cadaveric study. Acta Orthop Scand. 1999;70(1):9–11. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Major revision 24 Jan, 2022 Reviews received at journal 20 Jan, 2022 Reviewers invited by journal 11 Jan, 2022 Editor assigned by journal 11 Jan, 2022 First submitted to journal 02 Jan, 2022 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-1223482","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":75734246,"identity":"2bd1409a-a6a9-4c10-a297-5a1e3b313cd2","order_by":0,"name":"mehmet demirel","email":"data:image/png;base64,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","orcid":"","institution":"Istanbul University: Istanbul Universitesi","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"mehmet","middleName":"","lastName":"demirel","suffix":""},{"id":75734245,"identity":"091848ee-4e6c-45f4-89bd-ce612adb1143","order_by":1,"name":"Cem Yıldırım","email":"","orcid":"","institution":"Başakşehir çam ve sakura City Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Cem","middleName":"","lastName":"Yıldırım","suffix":""},{"id":75734247,"identity":"8d2e23cc-2b64-4e8b-ba83-54ee9e9f2329","order_by":2,"name":"Erhan Bayram","email":"","orcid":"","institution":"Gaziosmanpaşa medical park Hospital","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Erhan","middleName":"","lastName":"Bayram","suffix":""},{"id":75734248,"identity":"7f398c37-634d-453b-9cc7-96df5da58e5c","order_by":3,"name":"Mehmet Ekinci","email":"","orcid":"","institution":"Haseki Training and Research Hospital: Istanbul Haseki Egitim Ve Arastirma Hastanesi","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Mehmet","middleName":"","lastName":"Ekinci","suffix":""},{"id":75734249,"identity":"bb35e25e-7381-4845-9f25-bfbac8ec5b31","order_by":4,"name":"Murat Yılmaz","email":"","orcid":"","institution":"Haseki Training and Research Hospital: Istanbul Haseki Egitim Ve Arastirma Hastanesi","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Murat","middleName":"","lastName":"Yılmaz","suffix":""}],"badges":[],"createdAt":"2022-01-02 19:03:50","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-1223482/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-1223482/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":17261466,"identity":"26a7426c-8902-4ffd-9eae-3cfc4c90c0f9","added_by":"auto","created_at":"2022-01-12 19:03:51","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1000159,"visible":true,"origin":"","legend":"\u003cp\u003eRepresentative figure showing the intraoperative measurement method of the distance between the anterolateral edge of the acromion and the axillary nerve (blue arrow) using a caliper.\u0026nbsp;\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"Figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1223482/v1/195f4f473a8ae82f6b3d229f.jpg"},{"id":17261465,"identity":"94550312-02c3-43fc-82e3-e8fb812671c6","added_by":"auto","created_at":"2022-01-12 19:03:51","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":32622,"visible":true,"origin":"","legend":"\u003cp\u003eGraph illustrating the correlation between arm length and axillary nerve distance from the anterolateral edge of the acromion.\u0026nbsp;\u003c/p\u003e","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-1223482/v1/ff3a6fe011bafa0f37c0f103.jpg"},{"id":17261467,"identity":"a4a90b1d-013d-4dc4-8531-b5c90abb2043","added_by":"auto","created_at":"2022-01-12 19:03:53","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":386896,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-1223482/v1/0af4070b-5b40-43d5-a797-144700a0518f.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003eAcromion-axillary Nerve Distance and Its Relation to the Humeral Length in the Prediction of the Axillary Nerve Position During the Anterolateral Deltoid-splitting Approach in the Treatment of Proximal Humerus Fractures: a Clinical Study\u003c/p\u003e","fulltext":[{"header":"Background","content":"\u003cp\u003eIn the operative treatment of proximal humerus fractures, the deltopectoral approach is still the most widely used approach for internal plate fixation. However, this traditional approach offers limited access to the posterolateral aspect of the proximal humerus that may render reduction of a retracted greater tuberosity fragment and plate placement difficult [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] Alternatively, the anterolateral deltoid-splitting approach can provide direct access and excellent visualization of the greater tuberosity and the plating area, with minimal soft-tissue dissection [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], but there is an increased risk for axillary nerve injury, accounting for 6 to 10% of all iatrogenic nerve injuries to the brachial plexus [\u003cspan additionalcitationids=\"CR5 CR6 CR7\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAlthough it is generally accepted that the axillary nerve crosses the humerus horizontally nearly 50 mm distal to the acromion in clinical practice, various anatomical studies have defined a broad range of safe zones for deltoid-splitting approaches, varying from 30 to 70 mm distally to the acromion [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan additionalcitationids=\"CR10\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Furthermore, it has been shown that a safe zone for a nerve may change in size as per the extremity length [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Because of the large anatomical variation in the course of the axillary nerve from one individual to another, several cadaveric studies have explored the acromion-axillary nerve distance and its association with the humeral length to predict the axillary nerve location [\u003cspan additionalcitationids=\"CR14 CR15\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Nonetheless, to the best of our knowledge, the relationship between the axillary nerve location and humeral length has not been investigated in a clinical setting to date.\u003c/p\u003e \u003cp\u003eThis study aimed to analyze the acromion-axillary nerve distance (AAND) and its relation to the arm length (AL) in patients who underwent internal plate fixation for proximal humerus fractures. The authors hypothesized that acromion-axillary nerve distance has a significant correlation with the humeral length and can be used to predict the axillary nerve location during anterolateral deltoid-splitting approach.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eThe present prospective study involved 37 patients (15 female, 22 male; the mean age = 51 years, age range = 19 to 76) with displaced proximal humerus fractures who were treated by open reduction and internal fixation at a single tertiary trauma referral center from January 2017 to May 2019. According to the Neer classification system (17), there were 15 two-part (41%), 20 three-part (54%), and two four-part (5%) humerus fractures. Inclusion criteria were patients aged \u0026gt; 18 years, with proximal humerus fractures without a previous history of shoulder surgery. Exclusion criteria were patients with polytrauma, pathological fracture, concomitant fracture of the same upper extremity, limb discrepancy, or congenital deformity. An informed consent was obtained from all the patients preoperatively; ethical approval was obtained from the institutional ethical committee (88-2021, 06.10.2021).\u003c/p\u003e\n\u003cdiv class=\"Section2\" id=\"Sec3\"\u003e\n \u003ch2\u003eOperative technique\u003c/h2\u003e\n \u003cp\u003eAll surgical procedures were performed by a single experienced orthopedic trauma surgeon within a week of the injury, using the anterolateral deltoid-splitting approach. All the operations were performed under general anesthesia. The patients were placed in a beach-chair position, and bony landmarks were marked before making the incision. A longitudinal incision was made from the anterolateral edge of the acromion, which extended distally along the long axis of the humerus, and dissection was performed between the anterior and middle thirds of the deltoid muscle fibers. The axillary nerve was then palpated and visualized carefully. After ensuring adequate protection of the axillary nerve, the dissection was extended distally. The exposed region of the shoulder was divided into two parts by the axillary nerve. While the superior part was used for reduction of the fracture, the distal part was used for fixing the plate to the humeral shaft. Later, the fracture was reduced, and Kirschner wires were inserted for temporary fixation. The anatomic proximal humerus plate was then placed under the axillary nerve, and the rotator cuff was repaired if required. The final position was checked using fluoroscopy. The wound was closed in layers, and a drain inserted inside the subcutaneous tissue. Postoperatively, the arm was placed in a sling for controlled physical therapy.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv class=\"Section2\" id=\"Sec4\"\u003e\n \u003ch2\u003eOutcome measures\u003c/h2\u003e\n \u003cp\u003eWithin the routine steps of the planned operation, after anatomic reduction and fixation was achieved, the following parameters were measured in each patient before wound closure without making an extra incision or dissection: (1) the distance from the anterolateral edge of the acromion to the course of axillary nerve was recorded as the acromion-axillary nerve distance (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e), and (2) the distance from the anterolateral edge of the acromion to the lateral epicondyle of the humerus was recorded as AL [\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e]. The ratio of AAND to AL was then calculated and recorded as the axillary nerve index for each patient as described by \u0026Ccedil;etik et al.[\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e]. The correlation between AAND and AL was also investigated.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv class=\"Section2\" id=\"Sec5\"\u003e\n \u003ch2\u003eStatistical Analysis\u003c/h2\u003e\n \u003cp\u003eAll statistical analyses were performed using SPSS 25.0 software (SPSS Inc., Chicago, IL, USA). A p value of 0.05 was considered as statistically significant. Descriptive statistics were given as mean, standard deviation, percent, lowest (min) and highest (max) values. The Kolmogorov\u0026ndash;Smirnov test was used to verify the normal distribution of the variables. The correlation between AAND and AL was evaluated using the Spearman correlation analysis in a linear regression model. The level of correlation was interpreted according to Guilford\u0026rsquo;s interpretation [\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eThe mean AAND was 6 \u0026plusmn; 0.36 cm (range = 5.5 to 6.6 cm), and the mean AL was 32.9 \u0026plusmn; 2.9 cm (range = 24 to 38 cm). The mean axillary nerve index was 0.18 \u0026plusmn; 0.02 (range = 0.16 to 0.23) (Table \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). A significant moderate positive correlation was identified between AL and ANND (p = 0.006; r = 0.447) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). We were able to predict the location of the axillary nerve in 18% of the patients using the regression analysis.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDemographic data of the study participants\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNumber of the patients\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e37\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAge\u003c/b\u003e (years), mean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e51 (range = 17\u0026ndash;76)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eGender\u003c/b\u003e (Male/Female)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e22/15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAAND\u003c/b\u003e \u003cem\u003e(cm)\u003c/em\u003e, mean \u0026plusmn; SD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6\u0026plusmn;0.36 cm (range = 5.5\u0026ndash;6.6)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAL\u003c/b\u003e \u003cem\u003e(cm)\u003c/em\u003e, mean \u0026plusmn; SD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e32.91\u0026plusmn;2.9 cm (range = 24\u0026ndash;38)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAxillary nerve index\u003c/b\u003e \u003cem\u003e(AAND/AL)\u003c/em\u003e, mean \u0026plusmn; SD\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.18\u0026plusmn;0.02(0.16\u0026ndash;0.23)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eAAND = Acromion-axillary nerve distance; AL = Arm Length; SD = Standard Deviation\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eAlthough the anterolateral deltoid-splitting approach can ensure direct access and excellent visualization of the plating area in the management of proximal humerus fractures [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], there is an increased risk for axillary nerve injury, which is the most common neurological complication associated with surgery of proximal humerus fractures [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Accordingly, defining the safe zone for the axillary nerve is important to avoid iatrogenic injury. However, various anatomical studies have defined a broad range of safe zones for deltoid-splitting approaches, varying from 30 to 70 mm distally to the acromion [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan additionalcitationids=\"CR10\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Because of the broad anatomical variation in the course of the axillary nerve, the acromion-axillary nerve distance and its association with the humeral length were investigated to predict the axillary nerve location [\u003cspan additionalcitationids=\"CR14 CR15\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] in some cadaveric studies. Nonetheless, according to our review of the literature, the relationship between the axillary nerve location and humeral length has not been investigated in a clinical setting to date.\u003c/p\u003e \u003cp\u003eThe present study aimed to describe a safe area for executing the anterolateral deltoid split approach during open reduction\u0026ndash;plate fixation for managing patients with proximal humerus fractures. We found that ANND was 6.0 \u0026plusmn; 0.36 cm, which was moderately correlated with AL. However, ANND could be predicted according to AL in only 18% of the patients.\u003c/p\u003e \u003cp\u003eNumerous studies have attempted to measure ANND and found significant variations with a range of 4.5 to 7.5 cm [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Kongcharoensombat et al. [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] calculated the mean distance of the axillary nerve from the anterolateral acromion as 6.39 cm (ranging from 4.6 to 8.2 cm), and Cetik et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] found the distance of the axillary nerve from the anterolateral acromion to be 6.08 cm (ranging from 5.20 to 6.90 cm). Both previous studies observed significant correlation between the distance of the axillary nerve from the anterolateral acromion and humeral length. In contrast to the cadaveric studies of Kongcharoensombat [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] and Cetik et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], the present study was conducted in a clinical setting, and all measurements were performed intraoperatively after the anatomic reduction and fixation were completed. In this regard, our study is advantageous over the existing previous cadaveric studies in the literature.\u003c/p\u003e \u003cp\u003eWhile using the anterolateral approach for proximal humeral fractures, the plate should be inserted under the axillary nerve so that the nerve could be dissected carefully, and potential injury could be prevented. Also, the shortest distance should be taken into consideration during dissection to minimize the risk of probable axillary nerve injury. We measured the minimum distance of the axillary nerve to be 5.5 cm from the acromion. Hence, this distance could be considered as a safe zone according to the findings of the present study. In the study by Cetik et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], this distance was measured as 5.2 cm. However, this data contradicts the findings of Kongcharoensombat et al. [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] because the axillary nerve was found located at \u0026lt;5 cm in 13% of the cadaver shoulders.\u003c/p\u003e \u003cp\u003eIn our study, the calculated mean axillary nerve index was lower than that given by Cetik et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] and Kongcharoensombat et al. [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The exact prediction ratio of the location of the axillary nerve according to the humeral length of the patients was 18%, which was less than the expected value. Therefore, we believe that it would be safer to use the distance instead of the ratio.\u003c/p\u003e \u003cp\u003eOur study has several limitations. First, the number of patients who participated in the study was less. Second, the measurements were made using a manual caliper, thereby giving room for human errors. Third, all the measurements were performed after the anatomic reduction was completed. However, in case of deformity due to proximal humerus fracture before reduction was performed during the exposure, this distance is likely to be shortened.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eEvidence from this study has demonstrated that during the anterolateral deltoid-splitting approach to the shoulder joint, 5.5 cm from the anterolateral edge of the acromion could be considered as a safe zone for the prevention of possible axillary nerve injury. Predicting the location of the axillary nerve using the AL was possible in only 18% of the patients; thus, it would be safer to use the distance of 5.5 cm instead of relying on the axillary nerve index.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003e\u003cstrong\u003eAAND:\u0026nbsp;\u003c/strong\u003eAcromion-axillary nerve distance\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAL\u003c/strong\u003e: Arm length\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eEthical approval and consent to participate\u003c/h2\u003e\n\u003cp\u003eThis study was approved by the institutional review board of our institution and was carried out in accordance with the Declaration of Helsinki. Informed consent was obtained from all individual participants included in the study.\u003c/p\u003e\n\u003ch2\u003eConsent for publication\u003c/h2\u003e\n\u003cp\u003ePatients signed informed consent regarding publishing their data and photographs.\u003c/p\u003e\n\u003ch2\u003eCompeting interests\u003c/h2\u003e\n\u003cp\u003eAll authors promise that there is no competing interest to disclose.\u003c/p\u003e\n\u003ch2\u003eFunding\u003c/h2\u003e\n\u003cp\u003eNot applicable.\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003eAuthors\u0026apos; contributions\u003c/h2\u003e\n\u003cp\u003eCY: Conceptualization; Data curation; Methodology; Investigation\u003c/p\u003e\n\u003cp\u003eMD:\u0026nbsp;Validation; Writing - original draft\u003c/p\u003e\n\u003cp\u003eEB:\u0026nbsp;Methodology; Formal analysis; Writing - original draft,\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eME:\u0026nbsp;Formal analysis; Supervision; Validation; Writing - review \u0026amp; editing\u003c/p\u003e\n\u003cp\u003eMY:\u0026nbsp;Supervision; Validation\u0026nbsp;\u003c/p\u003e\n\u003ch2\u003eAvailability of data and materials\u003c/h2\u003e\n\u003cp\u003eThe data used and/or analysed during the current study are available from the corresponding author or the first author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eXie L, Zhang Y, Chen C, Zheng W, Chen H, Cai L. Deltoid-split approach versus deltopectoral approach for proximal humerus fractures: A systematic review and meta-analysis. Orthop Traumatol Surg Res. 2019;105(2):307\u0026ndash;16.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTraver JL, Guzman MA, Cannada LK, Kaar SG. Is the axillary nerve at risk during a deltoid-splitting approach for proximal humerus fractures? J Orthop Trauma. 2016;30(5):240\u0026ndash;4.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang J, Moore AE, Stringer MD. Iatrogenic upper limb nerve injuries: a systematic review. ANZ J Surg. 2011;81(4):227\u0026ndash;36.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEakin CL, Dvirnak P, Miller CM, Hawkins RJ. The relationship of the axillary nerve to arthroscopically placed capsulolabral sutures. Am J Sports Med. 1998;26(4):505\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLynch NM, Cofield RH, Silbert PL, Hermann RC. Neurologic complications after total shoulder arthroplasty. J Shoulder Elbow Surg. 1996;5(1):53\u0026ndash;61.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePerlmutter GS. \u003cb\u003eAxillary nerve injury\u003c/b\u003e. Clin Orthop Relat Res. 1999(368):28\u0026ndash;36.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSmith J, Berry G, Laflamme Y, Blain-Pare E, Reindl R, Harvey E. Percutaneous insertion of a proximal humeral locking plate: an anatomic study. Injury. 2007;38(2):206\u0026ndash;11.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTubbs RS, Tyler-Kabara EC, Aikens AC, Martin JP, Weed LL, Salter EG, Oakes WJ. Surgical anatomy of the axillary nerve within the quadrangular space. J Neurosurg. 2005;102(5):912\u0026ndash;4.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBryan WJ, Schauder K, Tullos HS. The axillary nerve and its relationship to common sports medicine shoulder procedures. Am J Sports Med. 1986;14(2):113\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBurkhead W Jr, Scheinberg R, Box G. Surgical anatomy of the axillary nerve. J Shoulder Elbow Surg. 1992;1(1):31\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDuparc F, Bocquet G, Simonet J, Freger P. Anatomical basis of the variable aspects of injuries of the axillary nerve (excluding the terminal branches in the deltoid muscle). Surg Radiol Anat. 1997;19(3):127\u0026ndash;32.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEksioglu F, Uslu M, Gudemez E, Atik OS, Tekdemir I. Reliability of the safe area for the superior gluteal nerve. Clin Orthop Relat Res. 2003;412:111\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCetik O, Uslu M, Acar HI, Comert A, Tekdemir I, Cift H. Is there a safe area for the axillary nerve in the deltoid muscle?: a cadaveric study. J Bone Joint Surg Am. 2006;88(11):2395\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKongcharoensombat W, Wattananon P. Risk of axillary nerve injury in standard anterolateral approach of shoulder: cadaveric study. Malays Orthop J. 2018;12(3):1.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRotari V, Moussallem CD, David E, Mertl P, Havet E. Position of the anterior branch of the axillary nerve in relation to the humeral bone length. Am J Orthop. 2012;41(10):452\u0026ndash;4.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSung C-M, Roh GS, Sohn H-J, Park HB. Prediction of the location of the anterior branch of the axillary nerve, using correlations with physical factors: a cadaveric study. J Shoulder Elbow Surg. 2013;22(11):e9\u0026ndash;16.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTredoux C, Durrheim K: \u003cb\u003eNumber\u003c/b\u003e, \u003cb\u003ehypotheses\u003c/b\u003e \u0026amp; \u003cb\u003econclusions\u003c/b\u003e: \u003cb\u003eA course in statistics for the social sciences\u003c/b\u003e. \u003cb\u003eCape Town\u003c/b\u003e. \u003cem\u003eUniversity of Cape Town Press Triguero, A, C\u0026oacute;rcoles, D, \u0026amp; Cuerva, MC (2014) Persistence of innovation and firm\u0026rsquo;s growth: evidence from a panel of SME and large Spanish manufacturing firms Small Business Economics\u003c/em\u003e 2002, \u003cb\u003e43\u003c/b\u003e(4):787-804.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShaw A, Milne A, Christie J, Jenkins AM, Murie J, Ruckley C. Vascular trauma of the upper limb and associated nerve injuries. Injury. 1995;26(8):515\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVisser CP, Coene LNJ, Brand R, Tavy DL. Nerve lesions in proximal humeral fractures. J Shoulder Elbow Surg. 2001;10(5):421\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKamineni S, Ankem H, Sanghavi S. Anatomical considerations for percutaneous proximal humeral fracture fixation. Injury. 2004;35(11):1133\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKontakis GM, Steriopoulos K, Damilakis J, Michalodimitrakis E. The position of the axillary nerve in the deltoid muscle: A cadaveric study. Acta Orthop Scand. 1999;70(1):9\u0026ndash;11.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-orthopaedic-surgery-and-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"josr","sideBox":"Learn more about [Journal of Orthopaedic Surgery and Research](http://josr-online.biomedcentral.com)","snPcode":"13018","submissionUrl":"https://submission.nature.com/new-submission/13018/3","title":"Journal of Orthopaedic Surgery and Research","twitterHandle":"@MSKmedBMC","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Axillary nerve, trans-deltoid approach, deltoid-splitting approach, iatrogenic nerve injury, safe zone","lastPublishedDoi":"10.21203/rs.3.rs-1223482/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-1223482/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground \u003c/strong\u003e\u003c/p\u003e\u003cp\u003eBecause of the broad anatomical variation in the course of the axillary nerve, several cadaveric studies have investigated the acromion-axillary nerve distance and its association with the humeral length to predict the axillary nerve location. This study aimed to analyze the acromion-axillary nerve distance (AAND) and its relation to the arm length (AL) in patients who underwent internal plate fixation for proximal humerus fractures.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e \u003c/p\u003e\u003cp\u003eThe present prospective study involved 37 patients (15 female, 22 male; the mean age = 51 years, age range = 19 to 76) with displaced proximal humerus fractures who were treated by open reduction and internal fixation. After anatomic reduction and fixation was achieved, the following parameters were measured in each patient before wound closure without making an extra incision or dissection: (1) the distance from the anterolateral edge of the acromion to the course of axillary nerve was recorded as the acromion-axillary nerve distance and (2) the distance from the anterolateral edge of the acromion to the lateral epicondyle of the humerus was recorded as arm length. The ratio of AAND to AL was then calculated and recorded as the axillary nerve index.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e \u003c/p\u003e\u003cp\u003eThe mean AAND was 6 ± 0.36 cm (range = 5.5–6.6), and the mean arm length was 32.91 ± 2.9 cm (range = 24–38). The mean axillary nerve ratio was 0.18 ± 0.02 (range = 0.16 to 0.23). There was a significant moderate positive correlation between AL and AAND (p = 0.006; r = 0.447). The axillary nerve location was predictable in only 18% of the patients.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e \u003c/p\u003e\u003cp\u003eDuring the anterolateral deltoid-splitting approach to the shoulder joint, 5.5 cm from the anterolateral edge of the acromion could be considered as a safe zone for the prevention of possible axillary nerve injury.\u0026nbsp;\u003c/p\u003e","manuscriptTitle":"Acromion-axillary Nerve Distance and Its Relation to the Humeral Length in the Prediction of the Axillary Nerve Position During the Anterolateral Deltoid-splitting Approach in the Treatment of Proximal Humerus Fractures: a Clinical Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2022-01-12 19:03:49","doi":"10.21203/rs.3.rs-1223482/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revision","date":"2022-01-24T06:59:59+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2022-01-20T11:08:58+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2022-01-11T09:30:53+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2022-01-11T06:10:01+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Orthopaedic Surgery and Research","date":"2022-01-02T14:03:18+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-orthopaedic-surgery-and-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"josr","sideBox":"Learn more about [Journal of Orthopaedic Surgery and Research](http://josr-online.biomedcentral.com)","snPcode":"13018","submissionUrl":"https://submission.nature.com/new-submission/13018/3","title":"Journal of Orthopaedic Surgery and Research","twitterHandle":"@MSKmedBMC","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"10666d64-5a50-4757-83f7-94ebecc0a2b5","owner":[],"postedDate":"January 12th, 2022","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2022-03-20T12:20:07+00:00","versionOfRecord":[],"versionCreatedAt":"2022-01-12 19:03:49","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-1223482","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-1223482","identity":"rs-1223482","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}