CT-Based Feasibility of Transsacral Osseous Corridors in Older Adults: The Impact of Lumbosacral Transitional Anatomy and Sacral Dysmorphism

CT-Based Feasibility of Transsacral Osseous Corridors in Older Adults: The Impact of Lumbosacral Transitional Anatomy and Sacral Dysmorphism | 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 CT-Based Feasibility of Transsacral Osseous Corridors in Older Adults: The Impact of Lumbosacral Transitional Anatomy and Sacral Dysmorphism Martin Naisan, Simon Harsch, Yazan Noufal, Felix Schmitz, Philipp Drees, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9313329/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 7 You are reading this latest preprint version Abstract Purpose: To quantify S1 and S2 transsacral corridor dimensions in an older adult control population and to evaluate the impact of lumbosacral transitional vertebrae (LSTV) and sacral dysmorphism on corridor feasibility. Secondary observations included the presence of alternative S3 corridors in anatomically atypical cases. Methods: A retrospective CT-based anatomical study was performed in 72 non-fracture controls aged ≥ 65 years. Axial, coronal, and longitudinal dimensions of potential S1–S3 transsacral corridors were measured. LSTV was classified according to Castellvi criteria. Sacral dysmorphism was defined using established CT morphological features independent of corridor feasibility. Corridor feasibility was assessed using axial diameter thresholds (≥ 7.0 mm and ≥ 7.3 mm). Group comparisons were performed using non-parametric statistics. Results: LSTV was present in 26.4% of cases. Absence of a measurable S1 corridor occurred in 23.6% overall and was strongly associated with LSTV (63.2% vs 9.4%, p < 0.001). In patients without LSTV, S1 corridors showed substantial dimensions (median axial diameter 15.3 mm, length 158 mm), whereas LSTV was associated with marked reduction (median axial diameter 0.0 mm, p < 0.001). S2 corridors were consistently present across anatomical subgroups and showed no significant reduction in axial diameter. In a small subset of anatomically atypical cases without LSTV, a potential S3 corridor was identified. Conclusions: In older adults, S1 transsacral corridor feasibility is frequently limited by lumbosacral transitional anatomy, whereas S2 corridors remain reliably preserved. These findings challenge routine reliance on S1 fixation and underscore the importance of CT-based preoperative assessment, with consideration of alternative sacral levels in anatomically complex cases. Level of Evidence III Sacral fragility fractures Safe corridor Dysmorphism Castellvi Figures Figure 1 Figure 2 Figure 3 INTRODUCTION Stabilization of the posterior pelvic ring remains a cornerstone in the surgical management of both high-energy pelvic trauma and low-energy fragility fractures of the sacrum [ 1 ]. Over the past two decades, transsacral fixation techniques have gained widespread acceptance due to their biomechanical advantages, particularly their ability to span both sacroiliac joints and provide enhanced resistance to vertical shear and rotational forces compared with unilateral iliosacral screw fixation [ 2 , 3 ]. These advantages are especially relevant in osteoporotic bone, where implant anchorage is compromised and load sharing across the pelvic ring becomes critical. Among transsacral fixation options, the S1 level has traditionally been considered the preferred target. The upper sacrum occupies a central position within the pelvic ring, and transsacral implants placed at S1 benefit from a longer lever arm and more favorable force transmission characteristics [ 4 ]. Consequently, many surgical algorithms implicitly assume the presence of a safe and sufficiently wide S1 transsacral corridor. However, this assumption is increasingly challenged by clinical experience, particularly in older adults, where intraoperative inability to place an S1 transsacral implant is not uncommon [ 5 , 6 ]. Safe placement of transsacral implants depends fundamentally on the presence of an adequate osseous corridor. Insufficient corridor width, length, or continuity increases the risk of cortical breach, sacral foraminal violation, and injury to adjacent neural and vascular structures [ 5 , 6 ]. Early cadaveric and fluoroscopy-based studies highlighted the narrow margins for error associated with iliosacral and transsacral screw placement, prompting a shift toward CT-based preoperative planning and navigation-assisted techniques [ 7 ]. Subsequent CT-based anatomical studies demonstrated substantial interindividual variability in sacral morphology, with corridor dimensions influenced by sacral ala orientation, foraminal size and shape, and sacral segmentation patterns [ 8 , 9 ]. Lumbosacral transitional vertebrae (LSTV) represent one of the most common congenital variations of the spine, with reported prevalence ranging from approximately 10% to 30% depending on the population studied and the imaging modality used [ 10 , 11 ]. Castellvi et al. proposed a classification system based on the morphology of the lowest lumbar transverse processes and their articulation or fusion with the sacrum, which remains widely used in clinical and radiological practice [ 12 ]. LSTV alters the segmentation and geometry of the lumbosacral junction and has been associated with changes in pedicle morphology, sacral ala orientation, and foraminal anatomy [ 13 ]. From a surgical perspective, these alterations may substantially affect the geometry and continuity of transsacral corridors, particularly at the S1 level. Distinct from LSTV, sacral dysmorphism describes a spectrum of morphological variations of the sacrum that do not necessarily involve transitional segmentation. Features commonly associated with sacral dysmorphism include acute alar slope, mammillary bodies at the sacral ala, residual disc space between S1 and S2, and atypical orientation or shape of the upper sacral foramina [ 8 ]. Sacral dysmorphism has been linked to increased rates of screw malposition and neurovascular complications during iliosacral fixation [ 8 , 14 ]. Importantly, although LSTV and sacral dysmorphism are frequently discussed together in the context of sacral fixation, they represent anatomically and developmentally distinct entities and may have different implications for corridor feasibility. Several CT-based studies have investigated the dimensions and feasibility of transsacral corridors. Many of these investigations, however, have focused on trauma populations or mixed cohorts that include patients with displaced pelvic fractures [ 5 , 9 ]. While these studies provide valuable insights into the challenges of transsacral fixation, fracture displacement, patient selection, and younger age distributions limit their ability to define baseline anatomical constraints. In particular, quantitative data describing transsacral corridor feasibility in older adults without pelvic fractures remain limited. This knowledge gap is clinically relevant. Older adults constitute the majority of patients undergoing minimally invasive transsacral fixation for fragility fractures of the sacrum, yet surgical planning is often informed by anatomical data derived from younger trauma populations. Failure to recognize baseline anatomical limitations may result in unsafe implant placement, intraoperative abandonment of planned fixation strategies, or unnecessary escalation to more invasive constructs. Furthermore, while alternative corridors at the S2 level have been proposed as reliable options when S1 is not feasible, and occasional reports describe use of S3 corridors, the availability and consistency of these alternatives in older adults remain insufficiently characterized. The purpose of the present study was therefore to provide a comprehensive CT-based analysis of transsacral corridor feasibility in an older adult control population without pelvic fractures. Specifically, we aimed to (1) quantitatively characterize the axial, coronal, and longitudinal dimensions of S1 and S2 transsacral corridors; (2) evaluate the influence of lumbosacral transitional anatomy and sacral dysmorphism on corridor feasibility; and (3) descriptively assess the presence of alternative S3 corridors in anatomically atypical cases. By focusing on a non-fracture elderly cohort, this study seeks to delineate baseline anatomical constraints relevant to surgical planning rather than fracture-related alterations. MATERIALS AND METHODS Study Design and Population This retrospective anatomical study included patients aged 65 years or older who underwent pelvic computed tomography (CT) as part of routine clinical care. All CT examinations were clinically indicated due to pelvic or low back pain and were performed with the primary purpose of excluding pelvic or sacral fractures. No CT scans were obtained for study-related screening or research purposes. Patients were eligible if CT imaging demonstrated no evidence of acute pelvic or sacral fracture. Exclusion criteria comprised acute pelvic trauma with confirmed fracture, prior pelvic or sacral instrumentation, pathological fractures, severe congenital deformities other than lumbosacral transitional vertebrae, and insufficient image quality for reliable morphometric analysis. CT Acquisition and Measurement Protocol CT Acquisition and Measurement Protocol All CT scans were acquired using standardized institutional protocols with slice thickness ≤ 1 mm. Multiplanar reconstructions in axial, coronal, and sagittal planes were generated. Measurements were performed on a dedicated PACS workstation by investigators experienced in pelvic CT analysis. Potential transsacral corridors at the S1, S2, and S3 levels were evaluated bilaterally. Axial and coronal diameters were measured at the narrowest point perpendicular to the presumed implant trajectory. Corridor length was measured from lateral cortex to lateral cortex. For each level, the minimum value obtained was used for analysis, reflecting the limiting side and the worst-case scenario for implant placement (see Fig. 1 ). Classification of Lumbosacral Transitional Vertebrae LSTV was classified according to the Castellvi classification based on CT morphology [ 12 ]. Castellvi types I–IV were recorded. For statistical analysis, any Castellvi type was considered indicative of LSTV, as even incomplete transitional anatomy may alter sacral morphology relevant to corridor feasibility. Definition of Sacral Dysmorphism Sacral dysmorphism was defined using established CT-based morphological criteria independent of corridor feasibility. Dysmorphic features included one or more of the following: mammillary bodies at the sacral ala, residual disc space between S1 and S2, acute alar slope, atypical orientation or shape of the upper sacral foramina, or anomalous sacral segmentation not fulfilling Castellvi criteria [ 12 ]. This definition was applied independently of corridor measurements to avoid circular classification. Corridor Feasibility Corridor feasibility was assessed descriptively using axial diameter thresholds of ≥ 7.0 mm and ≥ 7.3 mm, reflecting commonly reported transsacral implant diameters in the literature [ 15 , 16 ]. These thresholds were chosen to reflect practical surgical decision-making rather than to imply absolute safety margins. Statistical Analysis Continuous variables are presented as median and interquartile range (IQR). Group comparisons were performed using Mann–Whitney U tests. Feasibility rates were compared using Fisher’s exact test. Statistical significance was defined as p < 0.05. No multivariable predictive modeling was performed, as the primary aim was descriptive characterization of baseline anatomy. RESULTS Study Cohort Seventy-two control subjects met the inclusion criteria. LSTV was identified in 19 patients (26.4%). Absence of a measurable S1 corridor (axial diameter and corridor length both 0 mm) was observed in 17 patients (23.6%). Table 1 S1 and S2 Transsacral Corridor Dimensions Stratified by LSTV Values are median (IQR), all measurements in mm. Group S1 corridor length S1 axial diameter S1 coronal diameter S2 corridor length S2 axial diameter S2 coronal diameter No LSTV (n = 53) 158.2 (149.9–166.8) 15.3 (13.5–17.4) 17.9 (14.7–20.3) 141.2 (134.2–146.6) 9.7 (8.7–11.8) 10.6 (9.5–11.9) LSTV present (n = 19) 0.0 (0.0–152.1) 0.0 (0.0–13.8) 0.0 (0.0–16.1) 141.1 (135.5–150.6) 10.6 (8.9–12.8) 13.2 (10.5–14.6) p-value 0.0002 0.0005 0.0003 0.50 0.37 0.027 Impact of LSTV on S1 Corridor Feasibility Absence of a measurable S1 corridor was strongly associated with LSTV: 12 of 19 patients with LSTV (63.2%) lacked a measurable S1 corridor compared with 5 of 53 patients without LSTV (9.4%) (p < 0.001) (see Table 1 and Fig. 2 ). Using an axial diameter threshold ≥ 7.0 mm, S1 feasibility was 90.6% in patients without LSTV but only 36.8% in those with LSTV (p < 0.001). Similar results were observed using a ≥ 7.3 mm threshold (see Table 2 ). Table 2 Axial Corridor Feasibility Rates by LSTV Status Level Threshold No LSTV (n = 53) LSTV (n = 19) p-value S1 ≥ 7.0 mm 48/53 (90.6%) 7/19 (36.8%) < 0.001 S1 ≥ 7.3 mm 48/53 (90.6%) 7/19 (36.8%) < 0.001 S2 ≥ 7.0 mm 52/53 (98.1%) 18/19 (94.7%) 0.46 S2 ≥ 7.3 mm 52/53 (98.1%) 17/19 (89.5%) 0.17 S2 Corridor Characteristics S2 corridors were consistently present across anatomical subgroups. Neither axial diameter nor corridor length differed significantly between patients with and without LSTV. Even among patients lacking a measurable S1 corridor, S2 corridors remained identifiable, although modest reductions in coronal diameter were observed (see Table 3 ). Table 3 S2 Corridor Dimensions in Patients With and Without Measurable S1 Corridor Parameter S1 present (n = 55) No S1 corridor (n = 17) p-value S2 corridor length 142.5 (136.0–148.1) 136.2 (127.5–140.8) 0.0018 S2 axial diameter 10.1 (9.0–12.2) 9.0 (8.0–11.0) 0.11 S2 coronal diameter 11.5 (10.1–13.1) 9.0 (8.0–10.6) 0.0011 S3 Corridor Observations Among five patients without LSTV but without a measurable S1 corridor, a potential S3 corridor was identified in one case (see Fig. 3 ). Due to the limited number and heterogeneity, S3 findings were reported descriptively without inferential analysis. DISCUSSION Principal Findings This study demonstrates that in older adults, S1 transsacral corridor feasibility is frequently compromised by lumbosacral transitional anatomy, whereas S2 corridors remain largely preserved. The strong association between LSTV and absence of a measurable S1 corridor highlights the dominant role of segmentation anomalies rather than generalized age-related narrowing. Comparison With Previous Studies Prior CT-based analyses have reported reduced S1 corridor dimensions in dysmorphic sacra, particularly in trauma populations (8,9). Our findings extend these observations by focusing on a non-fracture older adult cohort, thereby delineating baseline anatomical constraints independent of injury. The high prevalence of preserved S2 corridors corroborates earlier reports suggesting S2 as a reliable alternative when S1 is not feasible (6). Clinical Implications Assumptions of universal S1 corridor availability are unsafe in older adults. Routine reliance on S1 transsacral fixation without detailed CT assessment risks cortical breach and neurovascular injury. The consistent presence of S2 corridors supports their consideration as a primary alternative in anatomically atypical cases. Methodological Strengths This study benefits from a well-defined control population, systematic CT measurements, and explicit differentiation between LSTV and sacral dysmorphism. By reporting absolute dimensions and feasibility rates rather than predictive models, the findings are directly applicable to surgical planning. Limitations The retrospective design and single-center setting limit generalizability. Assessment of S3 corridors was exploratory and not performed systematically. Functional or biomechanical validation was beyond the scope of this study. Future Directions Prospective studies integrating anatomical corridor assessment with intraoperative feasibility and clinical outcomes are warranted to refine fixation strategies in older adults. CONCLUSION In older adults, S1 transsacral corridor feasibility is frequently limited by lumbosacral transitional anatomy, whereas S2 corridors remain largely preserved. Preoperative CT-based assessment is essential for safe transsacral fixation planning, and alternative sacral levels should be considered in anatomically atypical cases. Declarations Declaration of Generative AI Use During manuscript preparation, the authors used ChatGPT (OpenAI, 2024 version) to assist with grammar and language editing. All content was subsequently reviewed and approved by the authors. Ethical Approval This study was approved by the local Ethical Committee of the Medical Association. Consent to Participate and Publish Written informed consent was obtained from all participants or their legal representatives, in accordance with institutional guidelines. Funding Statement This research received no external funding. Data Availability The datasets generated and analysed during the current study are available from the corresponding author on reasonable request. References Heiman E, Gencarelli Jr P, Tang A, Yingling JM, Liporace FA, Yoon RS (2022) Fragility fractures of the pelvis and sacrum: current trends in literature. Hip pelvis 34(2):69 Naisan M, Schmitz F, Noufal Y, Afghanyar Y, Fröhlich M, Richter M, Hartung P (2025) Transsacral Bar Fixation for Osteoporotic H-Type Sacral Fractures: A Viable Alternative to Spinopelvic Fixation. J Clin Med 14(18):6503 Ziran N, Collinge CA, Smith W, Matta JM (2022) Trans-sacral screw fixation of posterior pelvic ring injuries: review and expert opinion. Patient Saf Surg 16(1):24 Naisan M, Joumah M, Brenneis M, Richter M, Drees P, Hartung P (2025) Unilateral sacral fragility fractures: a comparative study of unilateral vs. bilateral minimally invasive osteosynthesis. Eur Spine J, 1–5 Gras F, Gottschling H, Schröder M, Marintschev I, Hofmann GO, Burgkart R (2016) Transsacral osseous corridor anatomy is more amenable to screw insertion in males: a biomorphometric analysis of 280 pelves. Clin Orthop Relat Research® 474(10):2304–2311 Jäckle K, Paulisch M, Blüchel T, Meier MP, Seitz MT, Acharya MR, Spering C (2022) Analysis of trans-sacral corridors in stabilization of fractures of the pelvic ring. J Orthop Research® 40(5):1194–1202 Carlson DA, Scheid DK, Maar DC, Baele JR, Kaehr DM (2000) Safe placement of S1 and S2 iliosacral screws: the vestibule concept. J Orthop Trauma 14(4):264–269 Kaiser SP, Gardner MJ, Liu J, Routt Jr MC, Morshed S (2014) Anatomic determinants of sacral dysmorphism and implications for safe iliosacral screw placement. JBJS, 96(14), e120 Wagner D, Kamer L, Sawaguchi T, Richards RG, Noser H, Hofmann A, Rommens PM (2017) Morphometry of the sacrum and its implication on trans-sacral corridors using a computed tomography data-based three-dimensional statistical model. Spine J 17(8):1141–1147 Basel SK, Barakoti RK, Chaudhary RK, Shrestha BK, Kaucha D, Rijal S (2023) Lumbosacral transitional vertebra among patients visiting the department of orthopaedics in a Tertiary Care Centre: a descriptive cross-sectional study. JNMA: J Nepal Med Association 61(258):102 French HD, Somasundaram AJ, Schaefer NR, Laherty RW (2014) Lumbosacral transitional vertebrae and its prevalence in the Australian population. Global spine J 4(4):229–232 Hanhivaara J, Määttä JH, Kinnunen P, Niinimäki J, Nevalainen MT (2024) Castellvi classification of lumbosacral transitional vertebrae: comparison between conventional radiography, CT, and MRI. Acta Radiol 65(12):1515–1520 Matson DM, MacCormick LM, Sembrano JN, Polly DW (2020) Sacral dysmorphism and lumbosacral transitional vertebrae (LSTV) review. Int J Spine Surg 14(s1):S14–S19 OMS ZH III, II OMS III, C. M., Weinstein D Strategies and Safety in Iliosacral Screw Placement Carlson DA, Scheid DK, Maar DC, Baele JR, Kaehr DM (2000) Safe placement of S1 and S2 iliosacral screws: the vestibule concept. J Orthop Trauma 14(4):264–269 Gras F, Gottschling H, Schröder M, Marintschev I, Hofmann GO, Burgkart R (2016) Transsacral osseous corridor anatomy is more amenable to screw insertion in males: a biomorphometric analysis of 280 pelves. Clin Orthop Relat Research® 474(10):2304–2311 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: Revision requested 27 Apr, 2026 Reviews received at journal 23 Apr, 2026 Reviewers agreed at journal 23 Apr, 2026 Reviewers invited by journal 23 Apr, 2026 Editor assigned by journal 06 Apr, 2026 Submission checks completed at journal 06 Apr, 2026 First submitted to journal 03 Apr, 2026 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-9313329","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":630436328,"identity":"282fbe88-6b67-4835-8b11-02a4d3e01d8d","order_by":0,"name":"Martin Naisan","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAtElEQVRIiWNgGAWjYJCCA0Asx9jAA6TYSNBiTJoWEEhsYCBWi+7s5ocHf9TcSW9u7z34gKHMhrAWszvHDA7zHHuW29hzLtmA4VwaEVpuJBgcZmA7nNs4I8dMgrHtMDFa0j8c/PHvcDojRMt/YrTkGBzgbTucANVygCgtBYd5+w4bNvacMTZIOJdMlMM2f/zx7bC8YXuP4YMPZXaEtcCBYQOQSCBBAwODPEmqR8EoGAWjYEQBACPpP7PGeL0MAAAAAElFTkSuQmCC","orcid":"","institution":"St. Josefs-Hospital Wiesbaden","correspondingAuthor":true,"prefix":"","firstName":"Martin","middleName":"","lastName":"Naisan","suffix":""},{"id":630436331,"identity":"e82fc79b-423d-4de3-95eb-f63554cbf2f9","order_by":1,"name":"Simon Harsch","email":"","orcid":"","institution":"St. Josefs-Hospital Wiesbaden","correspondingAuthor":false,"prefix":"","firstName":"Simon","middleName":"","lastName":"Harsch","suffix":""},{"id":630436335,"identity":"554b66b1-ac62-4730-901d-abb3525c842e","order_by":2,"name":"Yazan Noufal","email":"","orcid":"","institution":"St. Josefs-Hospital Wiesbaden","correspondingAuthor":false,"prefix":"","firstName":"Yazan","middleName":"","lastName":"Noufal","suffix":""},{"id":630436338,"identity":"d9271742-5d8b-4baf-b1fc-ecfad28983f4","order_by":3,"name":"Felix Schmitz","email":"","orcid":"","institution":"St. Josefs-Hospital Wiesbaden","correspondingAuthor":false,"prefix":"","firstName":"Felix","middleName":"","lastName":"Schmitz","suffix":""},{"id":630436340,"identity":"c1915e6b-ed2f-474d-9ef1-ec2d7d5931e3","order_by":4,"name":"Philipp Drees","email":"","orcid":"","institution":"Johannes Gutenberg University Mainz","correspondingAuthor":false,"prefix":"","firstName":"Philipp","middleName":"","lastName":"Drees","suffix":""},{"id":630436342,"identity":"54f18659-0a5e-4205-8d8b-69923f65e880","order_by":5,"name":"Philipp Hartung","email":"","orcid":"","institution":"St. Josefs-Hospital Wiesbaden","correspondingAuthor":false,"prefix":"","firstName":"Philipp","middleName":"","lastName":"Hartung","suffix":""},{"id":630436344,"identity":"3b53d6d5-f69a-4e7f-8aa1-57877c2656f7","order_by":6,"name":"Marcus Richter","email":"","orcid":"","institution":"St. Josefs-Hospital Wiesbaden","correspondingAuthor":false,"prefix":"","firstName":"Marcus","middleName":"","lastName":"Richter","suffix":""}],"badges":[],"createdAt":"2026-04-03 13:24:10","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9313329/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9313329/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":108793757,"identity":"9a9126bf-cc16-41f3-975c-f9ca6ac0db03","added_by":"auto","created_at":"2026-05-08 13:00:59","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":101430,"visible":true,"origin":"","legend":"\u003cp\u003eCT-based assessment of transsacral corridor feasibility at the S1 and S2 levels\u003c/p\u003e\n\u003cp\u003eMultiplanar CT reconstructions illustrating transsacral corridor measurements in an older adult without pelvic fracture.\u003c/p\u003e\n\u003cp\u003e(A) Example of a limited S1 transsacral corridor with reduced axial diameter on axial reconstruction and corresponding sagittal plane.\u003c/p\u003e\n\u003cp\u003e(B) Example of a preserved S2 transsacral corridor in the same anatomical context, demonstrating greater axial diameter and continuous osseous pathway.\u003c/p\u003e\n\u003cp\u003eAxial corridor diameters were measured at the narrowest point perpendicular to the presumed implant trajectory, and corridor length was assessed from lateral cortex to lateral cortex. All images were anonymized and obtained from clinically indicated CT examinations.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9313329/v1/fecbb86bfad9e84fedb6540a.jpeg"},{"id":108793758,"identity":"490a937b-fa14-4c2e-bae2-0f90a8a9ece7","added_by":"auto","created_at":"2026-05-08 13:00:59","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":80785,"visible":true,"origin":"","legend":"\u003cp\u003eFeasibility of S1 and S2 transsacral corridors by lumbosacral transitional anatomy.\u003c/p\u003e\n\u003cp\u003eBar charts show feasibility rates of S1 and S2 transsacral corridors stratified by the presence of lumbosacral transitional vertebrae (LSTV), using axial diameter thresholds of (A) ≥7.0 mm and (B) ≥7.3 mm. Values are presented as n/N (%) feasible corridors per subgroup. Corridor feasibility was defined solely by the axial diameter threshold and is intended to reflect commonly used transsacral implant diameters rather than absolute safety margins.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-9313329/v1/d7da140abdcdbb05c41d20b6.png"},{"id":108806814,"identity":"52756661-36c2-4fd3-9fc0-7462055311bf","added_by":"auto","created_at":"2026-05-08 15:29:31","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":84752,"visible":true,"origin":"","legend":"\u003cp\u003eCT illustration of alternative transsacral corridor anatomy in an anatomically atypical case.\u003c/p\u003e\n\u003cp\u003eMultiplanar CT reconstructions of an older adult without lumbosacral transitional vertebrae demonstrating absence of a measurable S1 transsacral corridor on axial and sagittal views, and presence of a potential alternative transsacral corridor at the S3 level. Corridor dimensions were assessed at the narrowest axial point perpendicular to the presumed implant trajectory. All images were anonymized and obtained from clinically indicated CT examinations.\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9313329/v1/9d488eb36f4e526a8a1ccb05.jpeg"},{"id":108809795,"identity":"0f611e30-c76f-4b41-a34f-440fb0f370e4","added_by":"auto","created_at":"2026-05-08 15:55:37","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":486145,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9313329/v1/1c0061eb-a31f-4289-9ef6-af0ebe562181.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"CT-Based Feasibility of Transsacral Osseous Corridors in Older Adults: The Impact of Lumbosacral Transitional Anatomy and Sacral Dysmorphism","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eStabilization of the posterior pelvic ring remains a cornerstone in the surgical management of both high-energy pelvic trauma and low-energy fragility fractures of the sacrum [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Over the past two decades, transsacral fixation techniques have gained widespread acceptance due to their biomechanical advantages, particularly their ability to span both sacroiliac joints and provide enhanced resistance to vertical shear and rotational forces compared with unilateral iliosacral screw fixation [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. These advantages are especially relevant in osteoporotic bone, where implant anchorage is compromised and load sharing across the pelvic ring becomes critical.\u003c/p\u003e \u003cp\u003eAmong transsacral fixation options, the S1 level has traditionally been considered the preferred target. The upper sacrum occupies a central position within the pelvic ring, and transsacral implants placed at S1 benefit from a longer lever arm and more favorable force transmission characteristics [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Consequently, many surgical algorithms implicitly assume the presence of a safe and sufficiently wide S1 transsacral corridor. However, this assumption is increasingly challenged by clinical experience, particularly in older adults, where intraoperative inability to place an S1 transsacral implant is not uncommon [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSafe placement of transsacral implants depends fundamentally on the presence of an adequate osseous corridor. Insufficient corridor width, length, or continuity increases the risk of cortical breach, sacral foraminal violation, and injury to adjacent neural and vascular structures [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Early cadaveric and fluoroscopy-based studies highlighted the narrow margins for error associated with iliosacral and transsacral screw placement, prompting a shift toward CT-based preoperative planning and navigation-assisted techniques [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Subsequent CT-based anatomical studies demonstrated substantial interindividual variability in sacral morphology, with corridor dimensions influenced by sacral ala orientation, foraminal size and shape, and sacral segmentation patterns [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eLumbosacral transitional vertebrae (LSTV) represent one of the most common congenital variations of the spine, with reported prevalence ranging from approximately 10% to 30% depending on the population studied and the imaging modality used [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Castellvi et al. proposed a classification system based on the morphology of the lowest lumbar transverse processes and their articulation or fusion with the sacrum, which remains widely used in clinical and radiological practice [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. LSTV alters the segmentation and geometry of the lumbosacral junction and has been associated with changes in pedicle morphology, sacral ala orientation, and foraminal anatomy [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. From a surgical perspective, these alterations may substantially affect the geometry and continuity of transsacral corridors, particularly at the S1 level.\u003c/p\u003e \u003cp\u003eDistinct from LSTV, sacral dysmorphism describes a spectrum of morphological variations of the sacrum that do not necessarily involve transitional segmentation. Features commonly associated with sacral dysmorphism include acute alar slope, mammillary bodies at the sacral ala, residual disc space between S1 and S2, and atypical orientation or shape of the upper sacral foramina [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Sacral dysmorphism has been linked to increased rates of screw malposition and neurovascular complications during iliosacral fixation [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Importantly, although LSTV and sacral dysmorphism are frequently discussed together in the context of sacral fixation, they represent anatomically and developmentally distinct entities and may have different implications for corridor feasibility.\u003c/p\u003e \u003cp\u003eSeveral CT-based studies have investigated the dimensions and feasibility of transsacral corridors. Many of these investigations, however, have focused on trauma populations or mixed cohorts that include patients with displaced pelvic fractures [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. While these studies provide valuable insights into the challenges of transsacral fixation, fracture displacement, patient selection, and younger age distributions limit their ability to define baseline anatomical constraints. In particular, quantitative data describing transsacral corridor feasibility in older adults without pelvic fractures remain limited.\u003c/p\u003e \u003cp\u003eThis knowledge gap is clinically relevant. Older adults constitute the majority of patients undergoing minimally invasive transsacral fixation for fragility fractures of the sacrum, yet surgical planning is often informed by anatomical data derived from younger trauma populations. Failure to recognize baseline anatomical limitations may result in unsafe implant placement, intraoperative abandonment of planned fixation strategies, or unnecessary escalation to more invasive constructs. Furthermore, while alternative corridors at the S2 level have been proposed as reliable options when S1 is not feasible, and occasional reports describe use of S3 corridors, the availability and consistency of these alternatives in older adults remain insufficiently characterized.\u003c/p\u003e \u003cp\u003eThe purpose of the present study was therefore to provide a comprehensive CT-based analysis of transsacral corridor feasibility in an older adult control population without pelvic fractures. Specifically, we aimed to (1) quantitatively characterize the axial, coronal, and longitudinal dimensions of S1 and S2 transsacral corridors; (2) evaluate the influence of lumbosacral transitional anatomy and sacral dysmorphism on corridor feasibility; and (3) descriptively assess the presence of alternative S3 corridors in anatomically atypical cases. By focusing on a non-fracture elderly cohort, this study seeks to delineate baseline anatomical constraints relevant to surgical planning rather than fracture-related alterations.\u003c/p\u003e"},{"header":"MATERIALS AND METHODS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy Design and Population\u003c/h2\u003e \u003cp\u003eThis retrospective anatomical study included patients aged 65 years or older who underwent pelvic computed tomography (CT) as part of routine clinical care. All CT examinations were clinically indicated due to pelvic or low back pain and were performed with the primary purpose of excluding pelvic or sacral fractures. No CT scans were obtained for study-related screening or research purposes.\u003c/p\u003e \u003cp\u003ePatients were eligible if CT imaging demonstrated no evidence of acute pelvic or sacral fracture. Exclusion criteria comprised acute pelvic trauma with confirmed fracture, prior pelvic or sacral instrumentation, pathological fractures, severe congenital deformities other than lumbosacral transitional vertebrae, and insufficient image quality for reliable morphometric analysis.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eCT Acquisition and Measurement Protocol\u003c/h3\u003e\n\u003cdiv class=\"Heading\"\u003eCT Acquisition and Measurement Protocol\u003c/div\u003e \u003cp\u003eAll CT scans were acquired using standardized institutional protocols with slice thickness\u0026thinsp;\u0026le;\u0026thinsp;1 mm. Multiplanar reconstructions in axial, coronal, and sagittal planes were generated. Measurements were performed on a dedicated PACS workstation by investigators experienced in pelvic CT analysis.\u003c/p\u003e \u003cp\u003ePotential transsacral corridors at the S1, S2, and S3 levels were evaluated bilaterally. Axial and coronal diameters were measured at the narrowest point perpendicular to the presumed implant trajectory. Corridor length was measured from lateral cortex to lateral cortex. For each level, the minimum value obtained was used for analysis, reflecting the limiting side and the worst-case scenario for implant placement (see Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eClassification of Lumbosacral Transitional Vertebrae\u003c/h3\u003e\n\u003cp\u003eLSTV was classified according to the Castellvi classification based on CT morphology [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Castellvi types I\u0026ndash;IV were recorded. For statistical analysis, any Castellvi type was considered indicative of LSTV, as even incomplete transitional anatomy may alter sacral morphology relevant to corridor feasibility.\u003c/p\u003e\n\u003ch3\u003eDefinition of Sacral Dysmorphism\u003c/h3\u003e\n\u003cp\u003eSacral dysmorphism was defined using established CT-based morphological criteria independent of corridor feasibility. Dysmorphic features included one or more of the following: mammillary bodies at the sacral ala, residual disc space between S1 and S2, acute alar slope, atypical orientation or shape of the upper sacral foramina, or anomalous sacral segmentation not fulfilling Castellvi criteria [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. This definition was applied independently of corridor measurements to avoid circular classification.\u003c/p\u003e\n\u003ch3\u003eCorridor Feasibility\u003c/h3\u003e\n\u003cp\u003eCorridor feasibility was assessed descriptively using axial diameter thresholds of \u0026ge;\u0026thinsp;7.0 mm and \u0026ge;\u0026thinsp;7.3 mm, reflecting commonly reported transsacral implant diameters in the literature [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. These thresholds were chosen to reflect practical surgical decision-making rather than to imply absolute safety margins.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eContinuous variables are presented as median and interquartile range (IQR). Group comparisons were performed using Mann\u0026ndash;Whitney U tests. Feasibility rates were compared using Fisher\u0026rsquo;s exact test. Statistical significance was defined as p\u0026thinsp;\u0026lt;\u0026thinsp;0.05. No multivariable predictive modeling was performed, as the primary aim was descriptive characterization of baseline anatomy.\u003c/p\u003e \u003c/div\u003e"},{"header":"RESULTS","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eStudy Cohort\u003c/h2\u003e \u003cp\u003eSeventy-two control subjects met the inclusion criteria. LSTV was identified in 19 patients (26.4%). Absence of a measurable S1 corridor (axial diameter and corridor length both 0 mm) was observed in 17 patients (23.6%).\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\u003e\u003cb\u003eS1 and S2 Transsacral Corridor Dimensions Stratified by LSTV\u003c/b\u003e Values are median (IQR), all measurements in mm.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGroup\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS1 corridor length\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eS1 axial diameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eS1 coronal diameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eS2 corridor length\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eS2 axial diameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eS2 coronal diameter\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNo LSTV (n\u0026thinsp;=\u0026thinsp;53)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e158.2 (149.9\u0026ndash;166.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e15.3 (13.5\u0026ndash;17.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e17.9 (14.7\u0026ndash;20.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e141.2 (134.2\u0026ndash;146.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e9.7 (8.7\u0026ndash;11.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e10.6 (9.5\u0026ndash;11.9)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLSTV present (n\u0026thinsp;=\u0026thinsp;19)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.0 (0.0\u0026ndash;152.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.0 (0.0\u0026ndash;13.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0 (0.0\u0026ndash;16.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e141.1 (135.5\u0026ndash;150.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e10.6 (8.9\u0026ndash;12.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e13.2 (10.5\u0026ndash;14.6)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003ep-value\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e0.0002\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.0005\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.0003\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e0.027\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eImpact of LSTV on S1 Corridor Feasibility\u003c/h2\u003e \u003cp\u003eAbsence of a measurable S1 corridor was strongly associated with LSTV: 12 of 19 patients with LSTV (63.2%) lacked a measurable S1 corridor compared with 5 of 53 patients without LSTV (9.4%) (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) (see Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eUsing an axial diameter threshold\u0026thinsp;\u0026ge;\u0026thinsp;7.0 mm, S1 feasibility was 90.6% in patients without LSTV but only 36.8% in those with LSTV (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Similar results were observed using a\u0026thinsp;\u0026ge;\u0026thinsp;7.3 mm threshold (see Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAxial Corridor Feasibility Rates by LSTV Status\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLevel\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eThreshold\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNo LSTV (n\u0026thinsp;=\u0026thinsp;53)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLSTV (n\u0026thinsp;=\u0026thinsp;19)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;7.0 mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e48/53 (90.6%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7/19 (36.8%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;7.3 mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e48/53 (90.6%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7/19 (36.8%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;7.0 mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e52/53 (98.1%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e18/19 (94.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.46\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;7.3 mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e52/53 (98.1%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e17/19 (89.5%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.17\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eS2 Corridor Characteristics\u003c/h2\u003e \u003cp\u003eS2 corridors were consistently present across anatomical subgroups. Neither axial diameter nor corridor length differed significantly between patients with and without LSTV. Even among patients lacking a measurable S1 corridor, S2 corridors remained identifiable, although modest reductions in coronal diameter were observed (see Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eS2 Corridor Dimensions in Patients With and Without Measurable S1 Corridor\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS1 present (n\u0026thinsp;=\u0026thinsp;55)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNo S1 corridor (n\u0026thinsp;=\u0026thinsp;17)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS2 corridor length\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e142.5 (136.0\u0026ndash;148.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e136.2 (127.5\u0026ndash;140.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0018\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS2 axial diameter\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e10.1 (9.0\u0026ndash;12.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9.0 (8.0\u0026ndash;11.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.11\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS2 coronal diameter\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e11.5 (10.1\u0026ndash;13.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9.0 (8.0\u0026ndash;10.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0011\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eS3 Corridor Observations\u003c/h2\u003e \u003cp\u003eAmong five patients without LSTV but without a measurable S1 corridor, a potential S3 corridor was identified in one case (see Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Due to the limited number and heterogeneity, S3 findings were reported descriptively without inferential analysis.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"DISCUSSION","content":"\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003ePrincipal Findings\u003c/h2\u003e \u003cp\u003eThis study demonstrates that in older adults, S1 transsacral corridor feasibility is frequently compromised by lumbosacral transitional anatomy, whereas S2 corridors remain largely preserved. The strong association between LSTV and absence of a measurable S1 corridor highlights the dominant role of segmentation anomalies rather than generalized age-related narrowing.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eComparison With Previous Studies\u003c/h2\u003e \u003cp\u003ePrior CT-based analyses have reported reduced S1 corridor dimensions in dysmorphic sacra, particularly in trauma populations (8,9). Our findings extend these observations by focusing on a non-fracture older adult cohort, thereby delineating baseline anatomical constraints independent of injury. The high prevalence of preserved S2 corridors corroborates earlier reports suggesting S2 as a reliable alternative when S1 is not feasible (6).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003eClinical Implications\u003c/h2\u003e \u003cp\u003eAssumptions of universal S1 corridor availability are unsafe in older adults. Routine reliance on S1 transsacral fixation without detailed CT assessment risks cortical breach and neurovascular injury. The consistent presence of S2 corridors supports their consideration as a primary alternative in anatomically atypical cases.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003eMethodological Strengths\u003c/h2\u003e \u003cp\u003eThis study benefits from a well-defined control population, systematic CT measurements, and explicit differentiation between LSTV and sacral dysmorphism. By reporting absolute dimensions and feasibility rates rather than predictive models, the findings are directly applicable to surgical planning.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003eLimitations\u003c/h2\u003e \u003cp\u003eThe retrospective design and single-center setting limit generalizability. Assessment of S3 corridors was exploratory and not performed systematically. Functional or biomechanical validation was beyond the scope of this study.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003eFuture Directions\u003c/h2\u003e \u003cp\u003eProspective studies integrating anatomical corridor assessment with intraoperative feasibility and clinical outcomes are warranted to refine fixation strategies in older adults.\u003c/p\u003e \u003c/div\u003e"},{"header":"CONCLUSION","content":"\u003cp\u003eIn older adults, S1 transsacral corridor feasibility is frequently limited by lumbosacral transitional anatomy, whereas S2 corridors remain largely preserved. Preoperative CT-based assessment is essential for safe transsacral fixation planning, and alternative sacral levels should be considered in anatomically atypical cases.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eDeclaration of Generative AI Use\u003c/p\u003e\n\u003cp\u003eDuring manuscript preparation, the authors used ChatGPT (OpenAI, 2024 version) to assist with grammar and language editing. All content was subsequently reviewed and approved by the authors.\u003c/p\u003e\n\u003cp\u003eEthical Approval\u003c/p\u003e\n\u003cp\u003eThis study was approved by the local Ethical Committee of the Medical Association.\u003c/p\u003e\n\u003cp\u003eConsent to Participate and Publish\u003c/p\u003e\n\u003cp\u003eWritten informed consent was obtained from all participants or their legal representatives, in accordance with institutional guidelines.\u003c/p\u003e\n\u003cp\u003eFunding Statement\u003c/p\u003e\n\u003cp\u003eThis research received no external funding.\u003c/p\u003e\n\u003cp\u003eData Availability\u003c/p\u003e\n\u003cp\u003eThe datasets generated and analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eHeiman E, Gencarelli Jr P, Tang A, Yingling JM, Liporace FA, Yoon RS (2022) Fragility fractures of the pelvis and sacrum: current trends in literature. Hip pelvis 34(2):69\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNaisan M, Schmitz F, Noufal Y, Afghanyar Y, Fr\u0026ouml;hlich M, Richter M, Hartung P (2025) Transsacral Bar Fixation for Osteoporotic H-Type Sacral Fractures: A Viable Alternative to Spinopelvic Fixation. J Clin Med 14(18):6503\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZiran N, Collinge CA, Smith W, Matta JM (2022) Trans-sacral screw fixation of posterior pelvic ring injuries: review and expert opinion. Patient Saf Surg 16(1):24\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNaisan M, Joumah M, Brenneis M, Richter M, Drees P, Hartung P (2025) Unilateral sacral fragility fractures: a comparative study of unilateral vs. bilateral minimally invasive osteosynthesis. Eur Spine J, 1\u0026ndash;5\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGras F, Gottschling H, Schr\u0026ouml;der M, Marintschev I, Hofmann GO, Burgkart R (2016) Transsacral osseous corridor anatomy is more amenable to screw insertion in males: a biomorphometric analysis of 280 pelves. Clin Orthop Relat Research\u0026reg; 474(10):2304\u0026ndash;2311\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJ\u0026auml;ckle K, Paulisch M, Bl\u0026uuml;chel T, Meier MP, Seitz MT, Acharya MR, Spering C (2022) Analysis of trans-sacral corridors in stabilization of fractures of the pelvic ring. J Orthop Research\u0026reg; 40(5):1194\u0026ndash;1202\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCarlson DA, Scheid DK, Maar DC, Baele JR, Kaehr DM (2000) Safe placement of S1 and S2 iliosacral screws: the vestibule concept. J Orthop Trauma 14(4):264\u0026ndash;269\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKaiser SP, Gardner MJ, Liu J, Routt Jr MC, Morshed S (2014) Anatomic determinants of sacral dysmorphism and implications for safe iliosacral screw placement. JBJS, 96(14), e120\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWagner D, Kamer L, Sawaguchi T, Richards RG, Noser H, Hofmann A, Rommens PM (2017) Morphometry of the sacrum and its implication on trans-sacral corridors using a computed tomography data-based three-dimensional statistical model. Spine J 17(8):1141\u0026ndash;1147\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBasel SK, Barakoti RK, Chaudhary RK, Shrestha BK, Kaucha D, Rijal S (2023) Lumbosacral transitional vertebra among patients visiting the department of orthopaedics in a Tertiary Care Centre: a descriptive cross-sectional study. JNMA: J Nepal Med Association 61(258):102\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFrench HD, Somasundaram AJ, Schaefer NR, Laherty RW (2014) Lumbosacral transitional vertebrae and its prevalence in the Australian population. Global spine J 4(4):229\u0026ndash;232\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHanhivaara J, M\u0026auml;\u0026auml;tt\u0026auml; JH, Kinnunen P, Niinim\u0026auml;ki J, Nevalainen MT (2024) Castellvi classification of lumbosacral transitional vertebrae: comparison between conventional radiography, CT, and MRI. Acta Radiol 65(12):1515\u0026ndash;1520\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMatson DM, MacCormick LM, Sembrano JN, Polly DW (2020) Sacral dysmorphism and lumbosacral transitional vertebrae (LSTV) review. Int J Spine Surg 14(s1):S14\u0026ndash;S19\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOMS ZH III, II OMS III, C. M., Weinstein D Strategies and Safety in Iliosacral Screw Placement\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCarlson DA, Scheid DK, Maar DC, Baele JR, Kaehr DM (2000) Safe placement of S1 and S2 iliosacral screws: the vestibule concept. J Orthop Trauma 14(4):264\u0026ndash;269\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGras F, Gottschling H, Schr\u0026ouml;der M, Marintschev I, Hofmann GO, Burgkart R (2016) Transsacral osseous corridor anatomy is more amenable to screw insertion in males: a biomorphometric analysis of 280 pelves. Clin Orthop Relat Research\u0026reg; 474(10):2304\u0026ndash;2311\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":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"european-journal-of-orthopaedic-surgery-and-traumatology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ejos","sideBox":"Learn more about [European Journal of Orthopaedic Surgery \u0026 Traumatology](http://link.springer.com/journal/590)","snPcode":"590","submissionUrl":"https://submission.springernature.com/new-submission/590/3","title":"European Journal of Orthopaedic Surgery \u0026 Traumatology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Sacral fragility fractures, Safe corridor, Dysmorphism, Castellvi","lastPublishedDoi":"10.21203/rs.3.rs-9313329/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9313329/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003ePurpose:\u003c/h2\u003e \u003cp\u003eTo quantify S1 and S2 transsacral corridor dimensions in an older adult control population and to evaluate the impact of lumbosacral transitional vertebrae (LSTV) and sacral dysmorphism on corridor feasibility. Secondary observations included the presence of alternative S3 corridors in anatomically atypical cases.\u003c/p\u003e\u003ch2\u003eMethods:\u003c/h2\u003e \u003cp\u003eA retrospective CT-based anatomical study was performed in 72 non-fracture controls aged\u0026thinsp;\u0026ge;\u0026thinsp;65 years. Axial, coronal, and longitudinal dimensions of potential S1\u0026ndash;S3 transsacral corridors were measured. LSTV was classified according to Castellvi criteria. Sacral dysmorphism was defined using established CT morphological features independent of corridor feasibility. Corridor feasibility was assessed using axial diameter thresholds (\u0026ge;\u0026thinsp;7.0 mm and \u0026ge;\u0026thinsp;7.3 mm). Group comparisons were performed using non-parametric statistics.\u003c/p\u003e\u003ch2\u003eResults:\u003c/h2\u003e \u003cp\u003eLSTV was present in 26.4% of cases. Absence of a measurable S1 corridor occurred in 23.6% overall and was strongly associated with LSTV (63.2% vs 9.4%, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). In patients without LSTV, S1 corridors showed substantial dimensions (median axial diameter 15.3 mm, length 158 mm), whereas LSTV was associated with marked reduction (median axial diameter 0.0 mm, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). S2 corridors were consistently present across anatomical subgroups and showed no significant reduction in axial diameter. In a small subset of anatomically atypical cases without LSTV, a potential S3 corridor was identified.\u003c/p\u003e\u003ch2\u003eConclusions:\u003c/h2\u003e \u003cp\u003eIn older adults, S1 transsacral corridor feasibility is frequently limited by lumbosacral transitional anatomy, whereas S2 corridors remain reliably preserved. These findings challenge routine reliance on S1 fixation and underscore the importance of CT-based preoperative assessment, with consideration of alternative sacral levels in anatomically complex cases.\u003c/p\u003e\u003ch2\u003eLevel of Evidence\u003c/h2\u003e \u003cp\u003eIII\u003c/p\u003e","manuscriptTitle":"CT-Based Feasibility of Transsacral Osseous Corridors in Older Adults: The Impact of Lumbosacral Transitional Anatomy and Sacral Dysmorphism","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-05-08 13:00:44","doi":"10.21203/rs.3.rs-9313329/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-04-27T14:38:50+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-23T22:57:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"242328060150621427685972986581184711994","date":"2026-04-23T22:28:04+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-23T22:27:50+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-06T12:23:34+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-04-06T12:23:26+00:00","index":"","fulltext":""},{"type":"submitted","content":"European Journal of Orthopaedic Surgery \u0026 Traumatology","date":"2026-04-03T13:20:04+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"european-journal-of-orthopaedic-surgery-and-traumatology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ejos","sideBox":"Learn more about [European Journal of Orthopaedic Surgery \u0026 Traumatology](http://link.springer.com/journal/590)","snPcode":"590","submissionUrl":"https://submission.springernature.com/new-submission/590/3","title":"European Journal of Orthopaedic Surgery \u0026 Traumatology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"73acc1d6-c108-46a4-9536-bdca75090383","owner":[],"postedDate":"May 8th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[],"tags":[],"updatedAt":"2026-05-18T16:55:00+00:00","versionOfRecord":[],"versionCreatedAt":"2026-05-08 13:00:44","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9313329","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9313329","identity":"rs-9313329","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}