Association Between Deltoid Muscle Attenuation and Sedation Requirement in Anterior Shoulder Dislocation

Association Between Deltoid Muscle Attenuation and Sedation Requirement in Anterior Shoulder Dislocation | 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 Association Between Deltoid Muscle Attenuation and Sedation Requirement in Anterior Shoulder Dislocation Mehmet Önüt, Aziz Furkan Günay, Mete Özer, Yiğit Önaloğlu, Mehmet Ali Talmaç This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9293355/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 11 You are reading this latest preprint version Abstract Background: Objective radiological predictors of sedation requirement during closed reduction of anterior shoulder dislocation have not been clearly established. This study aimed to evaluate the association between humeral head displacement parameters and computed tomography (CT)-based deltoid muscle morphology and attenuation with sedation requirement. Methods: A total of 467 patients presenting with anterior shoulder dislocation between May 2020 and February 2026 were retrospectively screened, and 213 patients were included after applying exclusion criteria. Closed reduction was performed without sedation in 182 patients and under procedural sedation in 31 patients. Humeral head displacement length, humeral head area, and the displacement length-to-head area index (HNADI) were measured on anteroposterior radiographs. CT measurements included anterior, lateral, and posterior deltoid muscle thicknesses, total cross-sectional area, and deltoid muscle attenuation (Hounsfield Units, HU). Independent predictors of sedation requirement were analyzed using multivariate logistic regression. Results: Patients requiring sedation were significantly older (p=0.022), and age remained an independent predictor in multivariate analysis (OR=1.052, p=0.003). Deltoid HU was significantly higher in the sedation group (p<0.001) and independently associated with sedation requirement (OR=1.133, p<0.001). Humeral head displacement length, humeral head area, HNADI, and deltoid muscle morphometric parameters were not independently associated with sedation requirement. Conclusion: Sedation requirement during closed reduction of anterior shoulder dislocation is associated with advanced age and increased deltoid HU rather than bony displacement parameters. CT-based assessment of deltoid HU may serve as an objective tool for pre-procedural sedation planning. Shoulder dislocation Procedural sedation Deltoid muscle Hounsfield units Closed reduction Figures Figure 1 Figure 2 Introduction Anterior shoulder dislocation is one of the most common large joint dislocations encountered in emergency departments and typically requires closed reduction to relieve pain, restore function, and prevent complications. A key determinant of successful reduction is the ability to overcome periarticular muscle spasm. For this purpose, procedural sedation and analgesia (PSA) is frequently used. However, PSA is associated with potential drawbacks, including cardiopulmonary complications such as hypoxia and hypotension, the need for close monitoring, and prolonged emergency department stay [ 1 ]. Therefore, identifying patients who truly require sedation and optimizing patient selection remain clinically important [ 2 ]. In recent years, alternative approaches such as non-sedated reduction techniques, intra-articular local anesthetics, and regional nerve blocks have been shown to achieve comparable success rates in selected patients [ 3 ]. Nevertheless, objective criteria that can reliably predict which patients can tolerate reduction without sedation and which will require it have not been clearly established. In current clinical practice, the decision to use sedation is largely based on subjective factors, including pain tolerance, anxiety level, and clinician experience. Previous studies investigating predictors of reduction difficulty are limited and have primarily focused on clinical parameters [ 4 ]. However, the mechanical resistance encountered during reduction may not depend solely on pain perception but also on structural factors, including the degree of bony displacement [ 5 ]. In addition, periarticular soft tissue characteristics have been relatively underexplored. While radiographic assessment of humeral head displacement may reflect the mechanical difficulty of reduction, computed tomography (CT)-based evaluation of deltoid muscle morphology and quality may provide additional insight into muscle resistance and relaxation capacity. The deltoid muscle, consisting of anterior, lateral, and posterior segments, plays a crucial role in shoulder stability and dynamic control. CT-derived parameters such as muscle thickness, cross-sectional area, and attenuation (Hounsfield Units, HU) allow quantitative assessment of muscle composition, including fatty infiltration. Recent studies have demonstrated that muscle HU is associated with muscle quality and functional outcomes in various orthopedic conditions [ 6 ][ 7 ]. However, the relationship between these parameters and sedation requirement during shoulder dislocation reduction has not yet been investigated. The aim of this study was to evaluate the association between radiographic humeral head displacement parameters and CT-based deltoid muscle morphology and attenuation with the need for sedation during closed reduction in patients with anterior shoulder dislocation without associated fractures. We hypothesized that greater humeral head displacement and higher deltoid HU would be associated with an increased likelihood of requiring sedation. Materials and Methods Study design and ethical approval: This retrospective study was approved by the Institutional Review Board of Basaksehir Cam and Sakura City Hospital (Approval No: 2026-90; March 16, 2026) and conducted in accordance with the Declaration of Helsinki. Patient selection: A total of 467 patients who presented to the emergency department with anterior shoulder dislocation between May 2020 and February 2026 were retrospectively reviewed. Patients were excluded if they had: (1) associated surgical neck or humeral head fractures (n = 112), (2) absence of shoulder computed tomography (CT) imaging (n = 96), (3) posterior or inferior shoulder dislocation (n = 18), (4) prior surgery on the affected shoulder (n = 12), (5) multiple trauma or hemodynamic instability (n = 9), or (6) incomplete or inadequate imaging data (n = 7). After applying the exclusion criteria, 213 patients were included in the final analysis. Sample size calculation: A priori sample size calculation was performed using G*Power software (version 3.1.9.7). Assuming a medium effect size (0.66), α = 0.05, power (1 − β) = 0.90, and an allocation ratio of 6.33, a minimum of 210 patients (at least 30 in the sedation group and 180 in the non-sedation group) was required. The final sample size (n = 213) met this requirement. Inclusion criteria and clinical management: Inclusion criteria were acute (< 24 hours) anterior glenohumeral dislocation without associated proximal humeral fracture. Closed reduction was performed without sedation in 182 patients and under procedural sedation in 31 patients. The decision to administer sedation was made based on clinical assessment, patient pain tolerance, and physician preference. Radiographic measurements: Standard anteroposterior shoulder radiographs obtained prior to reduction were evaluated. Humeral head displacement length was defined as the linear distance between the anterior glenoid rim and the most medial point of the humeral head (mm) [ 5 ]. Humeral head area was measured by manually outlining the cortical margins of the humeral head (mm²). The displacement length-to-head area index (HNADI) was calculated by dividing displacement length by humeral head area (Fig. 1 ). All measurements were performed using a digital PACS system. CT measurements and standardization: CT measurements were performed on post-reduction shoulder CT images. All measurements were obtained from a standardized axial slice at the level of the glenoid fossa where the mediolateral diameter was maximal and the humeral head center was visible. Anterior, lateral, and posterior deltoid muscle thicknesses were measured at the point of maximal thickness of each respective segment, defined as the maximum anteroposterior thickness anterior and posterior to the humeral head and the maximum mediolateral thickness lateral to the humeral head. Measurements were based on the widest cross-sectional dimension of each muscle segment rather than bony landmarks. The entire deltoid muscle was manually segmented on the same slice to calculate total cross-sectional area (mm²), and mean deltoid muscle attenuation (Hounsfield Units, HU) was obtained from the segmented region [ 6 ][ 8 ] (Fig. 2 ). Reduction techniques: Closed reduction procedures were performed in the emergency department by experienced physicians using one of the following techniques based on clinical preference: traction–countertraction, Stimson, or Milch method. Statistical analysis: Statistical analyses were performed using IBM SPSS Statistics for Windows, version 27.0 (IBM Corp., Armonk, NY, USA). A p-value < 0.05 was considered statistically significant. Categorical variables were expressed as frequencies and percentages, while continuous variables were presented as mean ± standard deviation or median (minimum–maximum), depending on distribution. Normality was assessed using the Kolmogorov–Smirnov test. For comparisons between sedation and non-sedation groups, independent samples t-test was used for normally distributed variables and Mann–Whitney U test for non-normally distributed variables. The chi-square test was used for categorical variables. Multivariate logistic regression analysis was performed to identify independent predictors of sedation requirement. Variables considered clinically and radiologically relevant were included in the model. Results were reported as odds ratios (OR) with 95% confidence intervals. Results A total of 467 patients presenting with anterior shoulder dislocation were retrospectively evaluated. Due to the exclusion criteria, 254 patients were excluded, and 213 patients were deemed eligible for analysis. Among the included patients, 141 of 182 patients (77.5%) in the non-sedation group were male and 41 (22.5%) were female, whereas in the sedation group, 24 of 31 patients (77.4%) were male and 7 (22.6%) were female. There was no statistically significant difference between the groups in terms of sex distribution (p = 0.995). Logistic regression (LR) analysis also confirmed that sex had no independent effect on sedation (p = 0.640; OR = 1.480). Sex did not play a determining or confounding role in the decision for sedation, and the sex profile of the patients was not considered a factor influencing sedation requirement (Table 1). When age was evaluated, the median age of patients in the non-sedation group was 29.5 years (range: 18–93), whereas the median age in the sedation group was 43 years (range: 18–79). This difference between the groups was statistically significant (p = 0.022). In the multivariate LR model, age remained strongly significant (p = 0.003; OR = 1.052). Age was identified as a persistent independent risk factor, increasing the likelihood of requiring sedation by 5.2% per year, independent of other clinical and radiological variables (Table 1). Table 1. Comparison of demographic and clinical characteristics of patients according to sedation status Sedation status No (n = 182) Yes (n = 31) P Gender 0,995* Male 141 (77,5) 24 (77,4) Female 41 (22,5) 7 (22,6) Total 182 (100,0) 31 (100,0) Side 0,436* Right 116 (63,7) 22 (71) Left 66 (36,3) 9 (29) Total 182 (100,0) 31 (100,0) Age 29,5 (18–93) 43 (18–79) 0,022† *Chi-square test; n(%); †Mann-Whitney U test; median (minimum-maximum); n=Number of patients No statistically significant difference was observed between the groups in terms of anterior and posterior deltoid thickness. The median anterior deltoid thickness was 18 mm (5–36) in the non-sedation group and 20 mm (10–30) in the sedation group (p = 0.280). The median posterior deltoid thickness was 23 mm (12–42) in the non-sedation group and 24 mm (12–38) in the sedation group, with no significant difference (p = 0.650) (Table 2). Lateral deltoid thickness was higher in the sedation group; the median value was 15 mm (5–34) in the non-sedation group and 17 mm (10–40) in the sedation group, and this difference was statistically significant in univariate analysis (p = 0.022). However, when included in the multivariate logistic regression model, lateral deltoid thickness lost its significance as an independent predictor (p = 0.722; OR = 1.019) (Table 2). Deltoid HU values were measured as a median of 45 (15–70) in the non-sedation group and 50 (35–86) in the sedation group. This difference was highly statistically significant (p < 0.001). This significance remained strong in the multivariate LR model (p < 0.001; OR = 1.133). Deltoid HU was identified as the most important independent risk factor, increasing the probability of requiring sedation by approximately 13.3% for each unit increase (Table 2). Mean humeral head displacement values (mm) were 38.58 ± 8.64 in the non-sedation group and 39.38 ± 9.03 in the sedation group. There was no statistically significant difference between the groups (p = 0.738). The degree of humeral head displacement was not a discriminative factor for sedation preference (Table 2). For humeral head area (mm²), the median value was 2300 in both groups (ranges: 1400–3700 and 1584–2824, respectively), with no statistically significant difference (p = 0.488). The size of the humeral head did not influence sedation requirement (Table 2). When HNADI values were evaluated, the median was 0.017 (0.007–0.032) in the non-sedation group and 0.017 (0.008–0.029) in the sedation group. No statistically significant difference was observed between the groups (p = 0.650). This parameter was not useful in predicting sedation requirement (Table 2). Table 2. Comparison of radiological measurements of patients according to sedation status Radiological measurements Sedation status No (n = 182) Yes (n = 31) P* Anterior deltoid length (mm) 18 (5–36) 20 (10–30) 0,280* Lateral deltoid length (mm) 15 (5–34) 17 (10–40) 0,022* Posterior deltoid length (mm) 23 (12–42) 24 (12–38) 0,650* Deltoid area (mm2) 4000 (1800–7300) 4500 (2200–7500) 0,109* Deltoid attenuation (HU) 45 (15–70) 50 (35–86) < 0,001* Humeral head displacement (mm) 38,58 ± 8,64 39,38 ± 9,03 0,738† Humeral head area (mm2) 2300 (1400–3700) 2300 (1584–2824) 0,488* HNADI 0,017 (0,007 − 0,032) 0,017 (0,008 − 0,029) 0,650* *Mann-Whitney U test; median (minimum-maximum); †Independent samples t-test; (mean ± standard deviation); n=Number of patients According to the results of the multivariate logistic regression analysis, when all variables were evaluated together, deltoid HU remained a statistically significant risk factor (p < 0.001; Exp(B) = 1.133). Each unit increase in deltoid HU increased the likelihood of requiring sedation by approximately 13.3%. Age was another variable that remained statistically significant in the multivariate model (p = 0.003; Exp(B) = 1.052). Each one-year increase in age was associated with a 5.2% increase in the probability of requiring sedation. All other radiological measurements and sex were not independently associated with sedation when other factors were controlled for. Discussion The most important finding of this study is the identification of an independent association between advanced age, increased deltoid HU, and the requirement for sedation during the reduction of anterior shoulder dislocation. Although reduction techniques and analgesia methods have been extensively investigated in the literature, radiological parameters predicting sedation requirement have been evaluated in a limited number of studies. Furuhata et al. demonstrated a statistically significant positive correlation between increasing age and the need for sedation in a retrospective series of 156 patients with anterior shoulder dislocation [ 9 ]. In our study, age was also found to be independently significant in the multivariate model, and each one-year increase was shown to increase the likelihood of requiring sedation. This finding may be related to differences in pain perception in older patients, increased joint stiffness, and clinicians’ preference for more controlled procedures. Additionally, age-related changes in periarticular soft tissue characteristics may necessitate greater analgesic support during reduction. In a recent study investigating the relationship between the position of the humeral head relative to the glenoid and complications that may occur during reduction, Gunsoy et al. reported that the position of the humeral head relative to the glenoid is a significant risk factor for the development of iatrogenic fractures during reduction [ 5 ]. This finding suggests that bony displacement characteristics may be mechanically important during the reduction process. However, in our study, humeral head displacement length, humeral head area, and their ratio (HNADI) were not found to be associated with sedation requirement. This result suggests that while bone position may be a determinant of complications during reduction, the need for sedation may not be explained to the same extent by bony displacement parameters. In imaging studies evaluating shoulder function, thickness and cross-sectional measurements of the anterior, lateral, and posterior segments of the deltoid muscle have been assessed. Meyer et al. analyzed the shape and thickness of deltoid muscle segments using magnetic resonance imaging in patients with chronic rotator cuff tears; however, these measurements were not found to be significantly associated with functional shoulder parameters [ 10 ]. This finding suggests that the relationship between deltoid muscle morphology and clinical outcomes may not always be direct. Indeed, recent studies focusing on muscle composition have demonstrated that muscle quality cannot be fully reflected by morphological measurements alone. In a recent study published in 2025, intermuscular adipose tissue was shown to be more determinant than intramuscular fat content in defining muscle attenuation, and it was emphasized that muscle attenuation may be a more sensitive parameter for evaluating muscle function [ 11 ]. However, no study in the literature has evaluated the relationship between these parameters and sedation requirement. In our study, anterior, lateral, and posterior deltoid segment lengths and total muscle area were objectively measured using CT; however, these morphometric parameters were not found to be independently associated with sedation requirement. In recent years, CT-based muscle analyses have emerged as reliable and quantitative methods for evaluating muscle quality. Hounsfield Unit (HU) values are indirect indicators of muscle attenuation and fatty infiltration and provide important information regarding the biomechanical properties of muscle [ 12 ]. In our study, the independent association between deltoid muscle attenuation and sedation requirement suggests that muscle quality may play a determining role in the mechanical resistance encountered during reduction. Increased HU values reflect reduced fatty infiltration but may also be associated with increased passive muscle stiffness, which may limit spontaneous muscle relaxation during reduction. Higher HU values, reflecting a more compact muscle structure, may increase resistance to relaxation and thereby increase the need for sedation. In the literature, muscle attenuation has also been shown to be associated with clinical outcomes. Liang et al. reported a significant relationship between proximal humerus fractures and lower deltoid muscle attenuation [ 6 ]. These findings support the notion that muscle attenuation, rather than muscle area, may better reflect functional capacity and biomechanical resistance. These findings indicate that, in patients presenting with anterior shoulder dislocation in the emergency department, radiographic bony displacement parameters alone are insufficient for sedation planning and that periarticular muscle quality should also be taken into consideration. In particular, sedation requirement may be more likely in patients with advanced age and increased deltoid HU. This study has several limitations. First, due to its retrospective design, not all clinical variables that may influence the decision for sedation could be controlled. The decision to administer sedation was not based on a standardized protocol, and considering that sedation may have been more frequently preferred in patients anticipated to have difficult reductions, this may have introduced potential selection bias. In addition, the use of different reduction techniques (traction–countertraction, Stimson, and Milch methods) may have resulted in variability affecting the difficulty of reduction and consequently influenced the results. Future studies should be designed as prospective and multicenter investigations evaluating clinical and radiological parameters affecting sedation requirement within a standardized protocol. In particular, studies in which sedation decisions are based on predefined objective criteria, reduction techniques are standardized, and clinical variables such as pain scores, time to presentation, and first-time versus recurrent dislocation are included in the analysis would contribute to the validation of these findings. Furthermore, studies evaluating the integration of HU-based muscle quality measurements into clinical decision-making algorithms may better clarify the potential role of this parameter in sedation planning. Conclusion Sedation requirement during closed reduction of anterior shoulder dislocation is associated with advanced age and increased deltoid muscle HU, independent of bony displacement parameters. While increasing age was found to increase the likelihood of sedation, deltoid HU measured on CT was also identified as an independent predictor. In contrast, humeral head displacement length, humeral head area, and HNADI were not found to be significant in predicting sedation requirement. These findings indicate that, in reduction planning, not only bony position but also periarticular muscle quality should be taken into consideration. Declarations Ethics approval and consent to participate: This study was approved by the Institutional Review Board of Basaksehir Cam and Sakura City Hospital (Approval number: 2026-90, Date: March 16, 2026). Written informed consent was obtained from all participants prior to enrollment. Consent for publication: Not applicable. Availability of data and materials: The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. Competing interests: The authors declare that they have no competing interests. Funding: The authors received no financial support for this study. Authors' contributions: Mehmet Önüt: Conceptualization, study design, data collection, data analysis, manuscript writing Aziz Furkan Günay: Methodology, data analysis, software Mete Özer: Data collection, investigation, visualization Mehmet Ali Talmaç: Methodology, validation Yiğit Önaloğlu: Data collection, investigation, validation All authors read and approved the final manuscript. Clinical trial number: not applicable. References Bellolio MF, Gilani WI, Barrionuevo P, Murad MH, Erwin PJ, Anderson JR, Miner JRHE. Incidence of Adverse Events in Adults Undergoing Procedural Sedation in the Emergency Department: A Systematic Review and Meta-analysis. Acad Emerg Med. Feb( 2016;23(2):119–34. Burcu Özen Karabulut MA. Procedural sedation and analgesia in the emergency department: a review of current practices and clinical implications. Anesthesiol Perioper Sci [Internet]. 2026;4(1):1–14. Available from: https://doi.org/10.1007/s44254-025-00129-y Baden DN, Visser MFL, Roetman MH, Smeeing DPJ, Houwert RM, Groenwold RHH et al. Effects of reduction technique for acute anterior shoulder dislocation without sedation or intra – articular pain management: a systematic review and meta – analysis. Eur J Trauma Emerg Surg [Internet]. 2023;49(3):1383–92. Available from: https://doi.org/10.1007/s00068-023-02242-8 PA L. Reduction of shoulder dislocation. Can Fam Physician. 2012;Nov(58(11)):1189–90. Zeki Gunsoy S, Oguzkaya G, Sayer F, Golgelioglu M, Dinc AM. The Impact of the Position of the Humeral Head Relative to the Glenoid on Iatrogenic Fractures During Shoulder Dislocation Reduction. Med. 2024;11(560):1816. Liang Y, Yang L, Zhang J et al. Association between Deltoid Muscle Density and Proximal Humeral Fracture in Elderly Patients. Orthop Rev (Pavia). 2024;16. Vedder IR, Levolger S, El Moumni M, Greuter MJW, Bokkers RPHVA. Influence of CT parameters upon the quantification of sarcopenia and myosteatosis: a study with human bodies. Sci Rep. 2026;Jan(8;16(1)):3954. Dillon C, O’Neill M, Christensen GV, Bradley Hillyard BS, Jun Kawakami B, PhD MD, Robert Z, Tashjian MD, Peter N, Chalmers M. Glenoid retroversion associates with deltoid muscle asymmetry in Walch B-type glenohumeral osteoarthritis. JSES Int. 2021;5:282–7. Ryogo Furuhata YK, Matsumura N, Kono A. Risk factors for failure of reduction of anterior glenohumeral dislocation without sedation. J Shoulder Elb Surg. 2021;30(2):306–11. Dominik C, Meyer SR, Farshad M. Deltoid muscle shape analysis with magneticresonance imaging in patients with chronicrotator cuff tears. BMC Musculoskelet Disord. 2013;14(247):1471–2474. Guo X, Cao N, Deng X, et al. Intermuscular adipose tissue affected muscle density more than intramuscular adipose tissue content with opportunistic screening at abdominal CT. Sci Rep. 2025;March(15):8172. Engelke K, Museyko O, Wang LLJ. Quantitative analysis of skeletal muscle by computed tomography imaging-State of the art. J Orthop Transl. 2018;Oct(2815):91–103. Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9293355","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":625584078,"identity":"f2b6b4a9-b34c-48ec-b6dc-6e3a671a4b15","order_by":0,"name":"Mehmet Önüt","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA7UlEQVRIiWNgGAWjYFACHhiD+YDBByDFxk6UlgSQUraEwhkgmpl4LTwGn8E2EtKi2957dMPHHzZ5Bvd7DDfb/Nomz8fMwPjhYw5uLWZnzqXdnJGQVmxwjK3YOLfvtmEbMwOz5MxteLTcyDG7zZNwOHHDMeZtxrk9txmBWtiYefFpuf/G7PYfsBYG89+WPbftCWu5wWN2mwGshcXAmOHH7UTCWs7kmN3sSUtLnHksLcGwt+F2chszYzN+vxw/Y3bjh41NYt/hwwcMfvy5bTu/vfngh494tKACxjYw2UCsehD4Q4riUTAKRsEoGCkAAFTAV3mcKaDyAAAAAElFTkSuQmCC","orcid":"","institution":"Istanbul Basaksehir Cam and Sakura City Hospital","correspondingAuthor":true,"prefix":"","firstName":"Mehmet","middleName":"","lastName":"Önüt","suffix":""},{"id":625584082,"identity":"c5f1a24d-da8b-4812-8df0-98d95dd34dd5","order_by":1,"name":"Aziz Furkan Günay","email":"","orcid":"","institution":"Istanbul Basaksehir Cam and Sakura City Hospital","correspondingAuthor":false,"prefix":"","firstName":"Aziz","middleName":"Furkan","lastName":"Günay","suffix":""},{"id":625584084,"identity":"7b69ad9f-b80a-4652-a502-31a4846e24ee","order_by":2,"name":"Mete Özer","email":"","orcid":"","institution":"Istanbul Basaksehir Cam and Sakura City Hospital","correspondingAuthor":false,"prefix":"","firstName":"Mete","middleName":"","lastName":"Özer","suffix":""},{"id":625584087,"identity":"d85969a9-9131-4e00-98c1-cc12b0b31078","order_by":3,"name":"Yiğit Önaloğlu","email":"","orcid":"","institution":"Istanbul Basaksehir Cam and Sakura City Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yiğit","middleName":"","lastName":"Önaloğlu","suffix":""},{"id":625584088,"identity":"2fffe373-c148-4c4a-929c-7dd8ae48ef17","order_by":4,"name":"Mehmet Ali Talmaç","email":"","orcid":"","institution":"Istanbul Basaksehir Cam and Sakura City Hospital","correspondingAuthor":false,"prefix":"","firstName":"Mehmet","middleName":"Ali","lastName":"Talmaç","suffix":""}],"badges":[],"createdAt":"2026-04-01 14:40:15","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9293355/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9293355/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":107617160,"identity":"50c8931d-1620-4e77-ac0e-0b54fdbe461c","added_by":"auto","created_at":"2026-04-23 09:17:33","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":209370,"visible":true,"origin":"","legend":"\u003cp\u003eMeasurement of humeral head displacement length and humeral head area on anteroposterior shoulder radiograph.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9293355/v1/ac74fff2015203b41e6b5f9b.png"},{"id":107617161,"identity":"3869477e-9f1c-486a-b4a8-f94438e6bb00","added_by":"auto","created_at":"2026-04-23 09:17:33","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":205599,"visible":true,"origin":"","legend":"\u003cp\u003eDeltoid muscle thickness, cross-sectional area, and muscle attenuation (HU) measurements on axial CT.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9293355/v1/f033fec6d395baf4ab0e69a5.png"},{"id":107706229,"identity":"8929ff9c-5494-45b1-a50b-63a49e5a848d","added_by":"auto","created_at":"2026-04-24 09:17:43","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":655974,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9293355/v1/bd14f2ea-3a2d-4685-8030-b970e4db063f.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Association Between Deltoid Muscle Attenuation and Sedation Requirement in Anterior Shoulder Dislocation","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAnterior shoulder dislocation is one of the most common large joint dislocations encountered in emergency departments and typically requires closed reduction to relieve pain, restore function, and prevent complications. A key determinant of successful reduction is the ability to overcome periarticular muscle spasm. For this purpose, procedural sedation and analgesia (PSA) is frequently used. However, PSA is associated with potential drawbacks, including cardiopulmonary complications such as hypoxia and hypotension, the need for close monitoring, and prolonged emergency department stay [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Therefore, identifying patients who truly require sedation and optimizing patient selection remain clinically important [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn recent years, alternative approaches such as non-sedated reduction techniques, intra-articular local anesthetics, and regional nerve blocks have been shown to achieve comparable success rates in selected patients [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Nevertheless, objective criteria that can reliably predict which patients can tolerate reduction without sedation and which will require it have not been clearly established. In current clinical practice, the decision to use sedation is largely based on subjective factors, including pain tolerance, anxiety level, and clinician experience.\u003c/p\u003e \u003cp\u003ePrevious studies investigating predictors of reduction difficulty are limited and have primarily focused on clinical parameters [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. However, the mechanical resistance encountered during reduction may not depend solely on pain perception but also on structural factors, including the degree of bony displacement [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. In addition, periarticular soft tissue characteristics have been relatively underexplored. While radiographic assessment of humeral head displacement may reflect the mechanical difficulty of reduction, computed tomography (CT)-based evaluation of deltoid muscle morphology and quality may provide additional insight into muscle resistance and relaxation capacity.\u003c/p\u003e \u003cp\u003eThe deltoid muscle, consisting of anterior, lateral, and posterior segments, plays a crucial role in shoulder stability and dynamic control. CT-derived parameters such as muscle thickness, cross-sectional area, and attenuation (Hounsfield Units, HU) allow quantitative assessment of muscle composition, including fatty infiltration. Recent studies have demonstrated that muscle HU is associated with muscle quality and functional outcomes in various orthopedic conditions [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e][\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. However, the relationship between these parameters and sedation requirement during shoulder dislocation reduction has not yet been investigated.\u003c/p\u003e \u003cp\u003eThe aim of this study was to evaluate the association between radiographic humeral head displacement parameters and CT-based deltoid muscle morphology and attenuation with the need for sedation during closed reduction in patients with anterior shoulder dislocation without associated fractures. We hypothesized that greater humeral head displacement and higher deltoid HU would be associated with an increased likelihood of requiring sedation.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cp\u003eStudy design and ethical approval:\u003c/p\u003e \u003cp\u003e This retrospective study was approved by the Institutional Review Board of Basaksehir Cam and Sakura City Hospital (Approval No: 2026-90; March 16, 2026) and conducted in accordance with the Declaration of Helsinki.\u003c/p\u003e \u003cp\u003ePatient selection:\u003c/p\u003e \u003cp\u003eA total of 467 patients who presented to the emergency department with anterior shoulder dislocation between May 2020 and February 2026 were retrospectively reviewed.\u003c/p\u003e \u003cp\u003ePatients were excluded if they had: (1) associated surgical neck or humeral head fractures (n\u0026thinsp;=\u0026thinsp;112), (2) absence of shoulder computed tomography (CT) imaging (n\u0026thinsp;=\u0026thinsp;96), (3) posterior or inferior shoulder dislocation (n\u0026thinsp;=\u0026thinsp;18), (4) prior surgery on the affected shoulder (n\u0026thinsp;=\u0026thinsp;12), (5) multiple trauma or hemodynamic instability (n\u0026thinsp;=\u0026thinsp;9), or (6) incomplete or inadequate imaging data (n\u0026thinsp;=\u0026thinsp;7).\u003c/p\u003e \u003cp\u003eAfter applying the exclusion criteria, 213 patients were included in the final analysis.\u003c/p\u003e \u003cp\u003eSample size calculation:\u003c/p\u003e \u003cp\u003eA priori sample size calculation was performed using G*Power software (version 3.1.9.7). Assuming a medium effect size (0.66), α\u0026thinsp;=\u0026thinsp;0.05, power (1\u0026thinsp;\u0026minus;\u0026thinsp;β)\u0026thinsp;=\u0026thinsp;0.90, and an allocation ratio of 6.33, a minimum of 210 patients (at least 30 in the sedation group and 180 in the non-sedation group) was required. The final sample size (n\u0026thinsp;=\u0026thinsp;213) met this requirement.\u003c/p\u003e \u003cp\u003eInclusion criteria and clinical management:\u003c/p\u003e \u003cp\u003eInclusion criteria were acute (\u0026lt;\u0026thinsp;24 hours) anterior glenohumeral dislocation without associated proximal humeral fracture. Closed reduction was performed without sedation in 182 patients and under procedural sedation in 31 patients. The decision to administer sedation was made based on clinical assessment, patient pain tolerance, and physician preference.\u003c/p\u003e \u003cp\u003eRadiographic measurements:\u003c/p\u003e \u003cp\u003eStandard anteroposterior shoulder radiographs obtained prior to reduction were evaluated. Humeral head displacement length was defined as the linear distance between the anterior glenoid rim and the most medial point of the humeral head (mm) [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Humeral head area was measured by manually outlining the cortical margins of the humeral head (mm\u0026sup2;). The displacement length-to-head area index (HNADI) was calculated by dividing displacement length by humeral head area (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). All measurements were performed using a digital PACS system.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eCT measurements and standardization:\u003c/p\u003e \u003cp\u003eCT measurements were performed on post-reduction shoulder CT images. All measurements were obtained from a standardized axial slice at the level of the glenoid fossa where the mediolateral diameter was maximal and the humeral head center was visible. Anterior, lateral, and posterior deltoid muscle thicknesses were measured at the point of maximal thickness of each respective segment, defined as the maximum anteroposterior thickness anterior and posterior to the humeral head and the maximum mediolateral thickness lateral to the humeral head. Measurements were based on the widest cross-sectional dimension of each muscle segment rather than bony landmarks. The entire deltoid muscle was manually segmented on the same slice to calculate total cross-sectional area (mm\u0026sup2;), and mean deltoid muscle attenuation (Hounsfield Units, HU) was obtained from the segmented region [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e][\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eReduction techniques:\u003c/p\u003e \u003cp\u003eClosed reduction procedures were performed in the emergency department by experienced physicians using one of the following techniques based on clinical preference: traction\u0026ndash;countertraction, Stimson, or Milch method.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis:\u003c/h2\u003e \u003cp\u003eStatistical analyses were performed using IBM SPSS Statistics for Windows, version 27.0 (IBM Corp., Armonk, NY, USA). A p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant. Categorical variables were expressed as frequencies and percentages, while continuous variables were presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation or median (minimum\u0026ndash;maximum), depending on distribution. Normality was assessed using the Kolmogorov\u0026ndash;Smirnov test. For comparisons between sedation and non-sedation groups, independent samples t-test was used for normally distributed variables and Mann\u0026ndash;Whitney U test for non-normally distributed variables. The chi-square test was used for categorical variables. Multivariate logistic regression analysis was performed to identify independent predictors of sedation requirement. Variables considered clinically and radiologically relevant were included in the model. Results were reported as odds ratios (OR) with 95% confidence intervals.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eA total of 467 patients presenting with anterior shoulder dislocation were retrospectively evaluated. Due to the exclusion criteria, 254 patients were excluded, and 213 patients were deemed eligible for analysis.\u003c/p\u003e\n\u003cp\u003eAmong the included patients, 141 of 182 patients (77.5%) in the non-sedation group were male and 41 (22.5%) were female, whereas in the sedation group, 24 of 31 patients (77.4%) were male and 7 (22.6%) were female. There was no statistically significant difference between the groups in terms of sex distribution (p\u0026thinsp;=\u0026thinsp;0.995). Logistic regression (LR) analysis also confirmed that sex had no independent effect on sedation (p\u0026thinsp;=\u0026thinsp;0.640; OR\u0026thinsp;=\u0026thinsp;1.480). Sex did not play a determining or confounding role in the decision for sedation, and the sex profile of the patients was not considered a factor influencing sedation requirement (Table\u0026nbsp;1).\u003c/p\u003e\n\u003cp\u003eWhen age was evaluated, the median age of patients in the non-sedation group was 29.5 years (range: 18\u0026ndash;93), whereas the median age in the sedation group was 43 years (range: 18\u0026ndash;79). This difference between the groups was statistically significant (p\u0026thinsp;=\u0026thinsp;0.022). In the multivariate LR model, age remained strongly significant (p\u0026thinsp;=\u0026thinsp;0.003; OR\u0026thinsp;=\u0026thinsp;1.052). Age was identified as a persistent independent risk factor, increasing the likelihood of requiring sedation by 5.2% per year, independent of other clinical and radiological variables (Table 1).\u003c/p\u003e\n\u003cdiv\u003e\n \u003cdiv align=\"left\" colname=\"c3\" colnum=\"3\"\u003eTable 1. Comparison of demographic and clinical characteristics of patients according to sedation status\u003c/div\u003e\n \u003ctable float=\"No\" id=\"Taba\" border=\"1\" class=\"fr-table-selection-hover\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\n \u003cp\u003eSedation status\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eNo (n\u0026thinsp;=\u0026thinsp;182)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eYes (n\u0026thinsp;=\u0026thinsp;31)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eP\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eGender\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e0,995*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eMale\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e141 (77,5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e24 (77,4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eFemale\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e41 (22,5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e7 (22,6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eTotal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e182 (100,0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e31 (100,0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eSide\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e0,436*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eRight\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e116 (63,7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e22 (71)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eLeft\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e66 (36,3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e9 (29)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eTotal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e182 (100,0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e31 (100,0)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eAge\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e29,5 (18\u0026ndash;93)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e43 (18\u0026ndash;79)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e\u003cstrong\u003e0,022\u0026dagger;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\"\u003e*Chi-square test; n(%); \u0026dagger;Mann-Whitney U test; median (minimum-maximum); n=Number of patients\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eNo statistically significant difference was observed between the groups in terms of anterior and posterior deltoid thickness. The median anterior deltoid thickness was 18 mm (5\u0026ndash;36) in the non-sedation group and 20 mm (10\u0026ndash;30) in the sedation group (p\u0026thinsp;=\u0026thinsp;0.280). The median posterior deltoid thickness was 23 mm (12\u0026ndash;42) in the non-sedation group and 24 mm (12\u0026ndash;38) in the sedation group, with no significant difference (p\u0026thinsp;=\u0026thinsp;0.650) (Table\u0026nbsp;2).\u003c/p\u003e\n\u003cp\u003eLateral deltoid thickness was higher in the sedation group; the median value was 15 mm (5\u0026ndash;34) in the non-sedation group and 17 mm (10\u0026ndash;40) in the sedation group, and this difference was statistically significant in univariate analysis (p\u0026thinsp;=\u0026thinsp;0.022). However, when included in the multivariate logistic regression model, lateral deltoid thickness lost its significance as an independent predictor (p\u0026thinsp;=\u0026thinsp;0.722; OR\u0026thinsp;=\u0026thinsp;1.019) (Table\u0026nbsp;2).\u003c/p\u003e\n\u003cp\u003eDeltoid HU values were measured as a median of 45 (15\u0026ndash;70) in the non-sedation group and 50 (35\u0026ndash;86) in the sedation group. This difference was highly statistically significant (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). This significance remained strong in the multivariate LR model (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001; OR\u0026thinsp;=\u0026thinsp;1.133). Deltoid HU was identified as the most important independent risk factor, increasing the probability of requiring sedation by approximately 13.3% for each unit increase (Table\u0026nbsp;2).\u003c/p\u003e\n\u003cp\u003eMean humeral head displacement values (mm) were 38.58\u0026thinsp;\u0026plusmn;\u0026thinsp;8.64 in the non-sedation group and 39.38\u0026thinsp;\u0026plusmn;\u0026thinsp;9.03 in the sedation group. There was no statistically significant difference between the groups (p\u0026thinsp;=\u0026thinsp;0.738). The degree of humeral head displacement was not a discriminative factor for sedation preference (Table\u0026nbsp;2).\u003c/p\u003e\n\u003cp\u003eFor humeral head area (mm\u0026sup2;), the median value was 2300 in both groups (ranges: 1400\u0026ndash;3700 and 1584\u0026ndash;2824, respectively), with no statistically significant difference (p\u0026thinsp;=\u0026thinsp;0.488). The size of the humeral head did not influence sedation requirement (Table\u0026nbsp;2).\u003c/p\u003e\n\u003cp\u003eWhen HNADI values were evaluated, the median was 0.017 (0.007\u0026ndash;0.032) in the non-sedation group and 0.017 (0.008\u0026ndash;0.029) in the sedation group. No statistically significant difference was observed between the groups (p\u0026thinsp;=\u0026thinsp;0.650). This parameter was not useful in predicting sedation requirement (Table\u0026nbsp;2).\u003c/p\u003e\n\u003cdiv\u003e\n \u003cdiv align=\"left\" colname=\"c4\" colnum=\"4\"\u003eTable 2. Comparison of radiological measurements of patients according to sedation status\u003c/div\u003e\u0026nbsp;\u003ctable float=\"No\" id=\"Tabb\" border=\"1\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\n \u003cp\u003eRadiological measurements\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\n \u003cp\u003eSedation status\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003eNo (n\u0026thinsp;=\u0026thinsp;182)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003eYes (n\u0026thinsp;=\u0026thinsp;31)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003eP*\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eAnterior deltoid length (mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e18 (5\u0026ndash;36)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e20 (10\u0026ndash;30)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e0,280*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eLateral deltoid length (mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e15 (5\u0026ndash;34)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e17 (10\u0026ndash;40)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e\u003cstrong\u003e0,022*\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003ePosterior deltoid length (mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e23 (12\u0026ndash;42)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e24 (12\u0026ndash;38)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e0,650*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eDeltoid area (mm2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e4000 (1800\u0026ndash;7300)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e4500 (2200\u0026ndash;7500)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e0,109*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eDeltoid attenuation (HU)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e45 (15\u0026ndash;70)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e50 (35\u0026ndash;86)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026lt;\u0026thinsp;0,001*\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eHumeral head displacement (mm)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e38,58\u0026thinsp;\u0026plusmn;\u0026thinsp;8,64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e39,38\u0026thinsp;\u0026plusmn;\u0026thinsp;9,03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e0,738\u0026dagger;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eHumeral head area (mm2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e2300 (1400\u0026ndash;3700)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e2300 (1584\u0026ndash;2824)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e0,488*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colname=\"c1\"\u003e\n \u003cp\u003eHNADI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c2\"\u003e\n \u003cp\u003e0,017 (0,007\u0026thinsp;\u0026minus;\u0026thinsp;0,032)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c3\"\u003e\n \u003cp\u003e0,017 (0,008\u0026thinsp;\u0026minus;\u0026thinsp;0,029)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colname=\"c4\"\u003e\n \u003cp\u003e0,650*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\"\u003e*Mann-Whitney U test; median (minimum-maximum); \u0026dagger;Independent samples t-test; (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation); n=Number of patients\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eAccording to the results of the multivariate logistic regression analysis, when all variables were evaluated together, deltoid HU remained a statistically significant risk factor (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Exp(B)\u0026thinsp;=\u0026thinsp;1.133). Each unit increase in deltoid HU increased the likelihood of requiring sedation by approximately 13.3%.\u003c/p\u003e\n\u003cp\u003eAge was another variable that remained statistically significant in the multivariate model (p\u0026thinsp;=\u0026thinsp;0.003; Exp(B)\u0026thinsp;=\u0026thinsp;1.052). Each one-year increase in age was associated with a 5.2% increase in the probability of requiring sedation. All other radiological measurements and sex were not independently associated with sedation when other factors were controlled for.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe most important finding of this study is the identification of an independent association between advanced age, increased deltoid HU, and the requirement for sedation during the reduction of anterior shoulder dislocation. Although reduction techniques and analgesia methods have been extensively investigated in the literature, radiological parameters predicting sedation requirement have been evaluated in a limited number of studies.\u003c/p\u003e \u003cp\u003eFuruhata et al. demonstrated a statistically significant positive correlation between increasing age and the need for sedation in a retrospective series of 156 patients with anterior shoulder dislocation [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. In our study, age was also found to be independently significant in the multivariate model, and each one-year increase was shown to increase the likelihood of requiring sedation. This finding may be related to differences in pain perception in older patients, increased joint stiffness, and clinicians\u0026rsquo; preference for more controlled procedures. Additionally, age-related changes in periarticular soft tissue characteristics may necessitate greater analgesic support during reduction.\u003c/p\u003e \u003cp\u003eIn a recent study investigating the relationship between the position of the humeral head relative to the glenoid and complications that may occur during reduction, Gunsoy et al. reported that the position of the humeral head relative to the glenoid is a significant risk factor for the development of iatrogenic fractures during reduction [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. This finding suggests that bony displacement characteristics may be mechanically important during the reduction process. However, in our study, humeral head displacement length, humeral head area, and their ratio (HNADI) were not found to be associated with sedation requirement. This result suggests that while bone position may be a determinant of complications during reduction, the need for sedation may not be explained to the same extent by bony displacement parameters.\u003c/p\u003e \u003cp\u003eIn imaging studies evaluating shoulder function, thickness and cross-sectional measurements of the anterior, lateral, and posterior segments of the deltoid muscle have been assessed. Meyer et al. analyzed the shape and thickness of deltoid muscle segments using magnetic resonance imaging in patients with chronic rotator cuff tears; however, these measurements were not found to be significantly associated with functional shoulder parameters [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. This finding suggests that the relationship between deltoid muscle morphology and clinical outcomes may not always be direct. Indeed, recent studies focusing on muscle composition have demonstrated that muscle quality cannot be fully reflected by morphological measurements alone. In a recent study published in 2025, intermuscular adipose tissue was shown to be more determinant than intramuscular fat content in defining muscle attenuation, and it was emphasized that muscle attenuation may be a more sensitive parameter for evaluating muscle function [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. However, no study in the literature has evaluated the relationship between these parameters and sedation requirement. In our study, anterior, lateral, and posterior deltoid segment lengths and total muscle area were objectively measured using CT; however, these morphometric parameters were not found to be independently associated with sedation requirement.\u003c/p\u003e \u003cp\u003eIn recent years, CT-based muscle analyses have emerged as reliable and quantitative methods for evaluating muscle quality. Hounsfield Unit (HU) values are indirect indicators of muscle attenuation and fatty infiltration and provide important information regarding the biomechanical properties of muscle [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. In our study, the independent association between deltoid muscle attenuation and sedation requirement suggests that muscle quality may play a determining role in the mechanical resistance encountered during reduction. Increased HU values reflect reduced fatty infiltration but may also be associated with increased passive muscle stiffness, which may limit spontaneous muscle relaxation during reduction. Higher HU values, reflecting a more compact muscle structure, may increase resistance to relaxation and thereby increase the need for sedation. In the literature, muscle attenuation has also been shown to be associated with clinical outcomes. Liang et al. reported a significant relationship between proximal humerus fractures and lower deltoid muscle attenuation [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. These findings support the notion that muscle attenuation, rather than muscle area, may better reflect functional capacity and biomechanical resistance.\u003c/p\u003e \u003cp\u003eThese findings indicate that, in patients presenting with anterior shoulder dislocation in the emergency department, radiographic bony displacement parameters alone are insufficient for sedation planning and that periarticular muscle quality should also be taken into consideration. In particular, sedation requirement may be more likely in patients with advanced age and increased deltoid HU.\u003c/p\u003e \u003cp\u003eThis study has several limitations. First, due to its retrospective design, not all clinical variables that may influence the decision for sedation could be controlled. The decision to administer sedation was not based on a standardized protocol, and considering that sedation may have been more frequently preferred in patients anticipated to have difficult reductions, this may have introduced potential selection bias. In addition, the use of different reduction techniques (traction\u0026ndash;countertraction, Stimson, and Milch methods) may have resulted in variability affecting the difficulty of reduction and consequently influenced the results. Future studies should be designed as prospective and multicenter investigations evaluating clinical and radiological parameters affecting sedation requirement within a standardized protocol. In particular, studies in which sedation decisions are based on predefined objective criteria, reduction techniques are standardized, and clinical variables such as pain scores, time to presentation, and first-time versus recurrent dislocation are included in the analysis would contribute to the validation of these findings. Furthermore, studies evaluating the integration of HU-based muscle quality measurements into clinical decision-making algorithms may better clarify the potential role of this parameter in sedation planning.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eSedation requirement during closed reduction of anterior shoulder dislocation is associated with advanced age and increased deltoid muscle HU, independent of bony displacement parameters. While increasing age was found to increase the likelihood of sedation, deltoid HU measured on CT was also identified as an independent predictor. In contrast, humeral head displacement length, humeral head area, and HNADI were not found to be significant in predicting sedation requirement. These findings indicate that, in reduction planning, not only bony position but also periarticular muscle quality should be taken into consideration.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Institutional Review Board of Basaksehir Cam and Sakura City Hospital (Approval number: 2026-90, Date: March 16, 2026). Written informed consent was obtained from all participants prior to enrollment.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors received no financial support for this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMehmet \u0026Ouml;n\u0026uuml;t: Conceptualization, study design, data collection, data analysis, manuscript writing\u003cbr\u003e\u0026nbsp;Aziz Furkan G\u0026uuml;nay: Methodology, data analysis, software\u003cbr\u003e\u0026nbsp;Mete \u0026Ouml;zer: Data collection, investigation, visualization\u003cbr\u003e\u0026nbsp;Mehmet Ali Talma\u0026ccedil;: Methodology, validation\u003cbr\u003e\u0026nbsp;Yiğit \u0026Ouml;naloğlu: Data collection, investigation, validation\u003cbr\u003e\u0026nbsp;All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003eClinical trial number: not applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBellolio MF, Gilani WI, Barrionuevo P, Murad MH, Erwin PJ, Anderson JR, Miner JRHE. Incidence of Adverse Events in Adults Undergoing Procedural Sedation in the Emergency Department: A Systematic Review and Meta-analysis. Acad Emerg Med. Feb( 2016;23(2):119\u0026ndash;34.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBurcu \u0026Ouml;zen Karabulut MA. Procedural sedation and analgesia in the emergency department: a review of current practices and clinical implications. Anesthesiol Perioper Sci [Internet]. 2026;4(1):1\u0026ndash;14. Available from: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s44254-025-00129-y\u003c/span\u003e\u003cspan address=\"10.1007/s44254-025-00129-y\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBaden DN, Visser MFL, Roetman MH, Smeeing DPJ, Houwert RM, Groenwold RHH et al. Effects of reduction technique for acute anterior shoulder dislocation without sedation or intra \u0026ndash; articular pain management: a systematic review and meta \u0026ndash; analysis. Eur J Trauma Emerg Surg [Internet]. 2023;49(3):1383\u0026ndash;92. Available from: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s00068-023-02242-8\u003c/span\u003e\u003cspan address=\"10.1007/s00068-023-02242-8\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePA L. Reduction of shoulder dislocation. Can Fam Physician. 2012;Nov(58(11)):1189\u0026ndash;90.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZeki Gunsoy S, Oguzkaya G, Sayer F, Golgelioglu M, Dinc AM. The Impact of the Position of the Humeral Head Relative to the Glenoid on Iatrogenic Fractures During Shoulder Dislocation Reduction. Med. 2024;11(560):1816.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiang Y, Yang L, Zhang J et al. Association between Deltoid Muscle Density and Proximal Humeral Fracture in Elderly Patients. Orthop Rev (Pavia). 2024;16.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVedder IR, Levolger S, El Moumni M, Greuter MJW, Bokkers RPHVA. Influence of CT parameters upon the quantification of sarcopenia and myosteatosis: a study with human bodies. Sci Rep. 2026;Jan(8;16(1)):3954.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDillon C, O\u0026rsquo;Neill M, Christensen GV, Bradley Hillyard BS, Jun Kawakami B, PhD MD, Robert Z, Tashjian MD, Peter N, Chalmers M. Glenoid retroversion associates with deltoid muscle asymmetry in Walch B-type glenohumeral osteoarthritis. JSES Int. 2021;5:282\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRyogo Furuhata YK, Matsumura N, Kono A. Risk factors for failure of reduction of anterior glenohumeral dislocation without sedation. J Shoulder Elb Surg. 2021;30(2):306\u0026ndash;11.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDominik C, Meyer SR, Farshad M. Deltoid muscle shape analysis with magneticresonance imaging in patients with chronicrotator cuff tears. BMC Musculoskelet Disord. 2013;14(247):1471\u0026ndash;2474.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGuo X, Cao N, Deng X, et al. Intermuscular adipose tissue affected muscle density more than intramuscular adipose tissue content with opportunistic screening at abdominal CT. Sci Rep. 2025;March(15):8172.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEngelke K, Museyko O, Wang LLJ. Quantitative analysis of skeletal muscle by computed tomography imaging-State of the art. J Orthop Transl. 2018;Oct(2815):91\u0026ndash;103.\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":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Shoulder dislocation, Procedural sedation, Deltoid muscle, Hounsfield units, Closed reduction","lastPublishedDoi":"10.21203/rs.3.rs-9293355/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9293355/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground:\u003c/strong\u003e\u003cbr\u003e\nObjective radiological predictors of sedation requirement during closed reduction of anterior shoulder dislocation have not been clearly established. This study aimed to evaluate the association between humeral head displacement parameters and computed tomography (CT)-based deltoid muscle morphology and \u003cstrong\u003eattenuation\u003c/strong\u003ewith sedation requirement.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e\u003cbr\u003e\nA total of 467 patients presenting with anterior shoulder dislocation between May 2020 and February 2026 were retrospectively screened, and 213 patients were included after applying exclusion criteria. Closed reduction was performed without sedation in 182 patients and under procedural sedation in 31 patients. Humeral head displacement length, humeral head area, and the displacement length-to-head area index (HNADI) were measured on anteroposterior radiographs. CT measurements included anterior, lateral, and posterior deltoid muscle thicknesses, total cross-sectional area, and \u003cstrong\u003edeltoid muscle attenuation (Hounsfield Units, HU).\u003c/strong\u003e Independent predictors of sedation requirement were analyzed using multivariate logistic regression.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e\u003cbr\u003e\nPatients requiring sedation were significantly older (p=0.022), and age remained an independent predictor in multivariate analysis (OR=1.052, p=0.003). \u003cstrong\u003eDeltoid HU \u003c/strong\u003ewas significantly higher in the sedation group (p\u0026lt;0.001) and independently associated with sedation requirement (OR=1.133, p\u0026lt;0.001). Humeral head displacement length, humeral head area, HNADI, and deltoid muscle morphometric parameters were not independently associated with sedation requirement.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion:\u003c/strong\u003e\u003cbr\u003e\nSedation requirement during closed reduction of anterior shoulder dislocation is associated with advanced age and increased \u003cstrong\u003edeltoid HU \u003c/strong\u003erather than bony displacement parameters. CT-based assessment of deltoid HU may serve as an objective tool for pre-procedural sedation planning.\u003c/p\u003e","manuscriptTitle":"Association Between Deltoid Muscle Attenuation and Sedation Requirement in Anterior Shoulder Dislocation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-23 09:17:19","doi":"10.21203/rs.3.rs-9293355/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-04-29T15:40:20+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-25T13:34:08+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-24T02:27:26+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"49751621989370985546337525519667639473","date":"2026-04-19T02:28:28+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"275737985329746295119951143598581632464","date":"2026-04-18T15:14:45+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"237869790448248756199932144464091854166","date":"2026-04-18T14:41:34+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-15T02:19:21+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-04-06T15:10:35+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-04T10:48:31+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-04-04T10:48:25+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Musculoskeletal Disorders","date":"2026-04-01T14:31:15+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-musculoskeletal-disorders","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmsd","sideBox":"Learn more about [BMC Musculoskeletal Disorders](http://bmcmusculoskeletdisord.biomedcentral.com/)","snPcode":"","submissionUrl":"https://author-welcome.nature.com/12891","title":"BMC Musculoskeletal Disorders","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"8485bacf-6b3b-41ce-aa40-0f33890b1b3c","owner":[],"postedDate":"April 23rd, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Revision requested","date":"2026-04-29T15:40:20+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-05T05:55:43+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-23 09:17:19","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9293355","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9293355","identity":"rs-9293355","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}