CT can enhance the measurement accuracy of radiographic anteversion of acetabular cup following total hip arthroplasty

CT can enhance the measurement accuracy of radiographic anteversion of acetabular cup following total hip arthroplasty | 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 can enhance the measurement accuracy of radiographic anteversion of acetabular cup following total hip arthroplasty Wenzhe Wang, Zian Zhang, Zhenchao Huang, Chang Liu, Qianqian Wang, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4862348/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background This study employed a novel method to measure radiographic anteversion (RA) of acetabular cups following total hip arthroplasty (THA) and validated its accuracy in comparison to traditional methods. The new method involves measuring anatomical anteversion (AA) using CT scans and radiographic inclination (RI) from anteroposterior (AP) radiographs, followed by calculating RA through a mathematical function. Methods The imaging data of 152 patients (192 hips) post-THA were retrospectively assessed twice for RA by two independent observers, utilizing Lewinnek’s method, Pradhan’s method, and the new method. Obtaining actual values ​​of RA from patient’s 3D imaging data. The intraobserver and interobserver reliability and accuracy of each method were subsequently compared. Results When compared to Lewinnek’s and Pradhan's method, the new method demonstrated superior intraobserver and interobserver reliability. Furthermore, the values obtained through the new method were closer to the actual values for acetabular RA. Conclusion Leveraging CT data, the new method introduced in this study enhances the accuracy of acetabular radiographic anteversion measurements. Total hip arthroplasty Anteversion Safe zone Measurement Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Accurately measuring acetabular cup anteversion and abduction following total hip arthroplasty (THA) is critically important for assessing the success of THA and guiding revision surgeries in cases of recurrent dislocations. Murray’s definition of anteversion and abduction is widely accepted and used as a standard in the literature 1 . As shown in Figure 1, Murray defined anteversion as follows: anatomical anteversion (AA): the angle between the projection of the cup axis (line OE) onto the horizontal plane (line OF) and the coronal axis (line OC); radiographic anteversion (RA): the angle between the cup axis (line OE) and the coronal plane; operative anteversion (OA): the angle between the projection of the cup axis (line OE) on the sagittal plane (line OD) and the vertical line (line OA). In addition, he defined the angle between the projection of the cup axis (line OE) on the coronal plane (line OB) and the vertical line (line OA) as radiographic inclination (RI). Figure 1: Diagram of acetabular cup abduction and anteversion. The methods for measuring inclination are relatively uniform. The opening of the cup is projected into an ellipse on anteroposterior (AP) radiographs, and cup abduction is the angle between the long axis of the ellipse and the horizontal line 2 (the line through the lower edge of the bilateral teardrop, as shown in Figure 2a), which refers to Murray’s RI. However, the anteversion angle has been measured in various ways in different studies. Lewinnek 2 , Callanan 3 , Pradhan 4 , Widmer 5 , Liaw 6 measured the RA on AP radiographs using different methods 7 . The concept of the “anteversion safe zone” proposed by Lewinnek 2 and Callanan 3 , which is widely accepted and referenced, also refers to this definition of anteversion. However, the disadvantages of measurement on AP radiographs include large errors, low repeatability, strict requirements on patient positioning, and inability to distinguish anteversion or retroversion 2,4-8 . Some studies choose to measure the anteversion angle directly from a CT scan (as shown in Figure 2b), with the advantages of less error and regardless of the patient's position 7,9,10 . However, it should be noted that the anteversion directly measured in a CT is the AA 7 , instead of the RA. In some studies, no distinction is made between the two definitions. It is obviously inappropriate to compare the AA measured in a CT with the RA safe zone proposed by Lewinnek and Callanan. After calculation and review of relevant literature 1,11 , we found that the mathematics relationship shown in Equation 1 existed between several angles. We designed a new measurement method that improves the measurement accuracy of RA in AP radiographs with CT data. Figure 2. Measurements of the RI and AA in AP radiographs. a: The angle between the projection of the cup axis on AP radiographs and the vertical line is the RI, which is equal to the angle between the long axis of the projected ellipse and horizontal line. b: On the appropriate horizontal plane of a hip CT, measure the angle between the projection of the cup axis and the coronal axis (line connecting the center points of bilateral femoral heads) as the AA (γ), which is equal to the angle between the line connecting the endpoints of the cup arc and the sagittal line. RA=tan -1 (tan (AA) ×sin (RI )) Equation 1 Materials and Methods To compare the accuracy of various methods, we conducted a retrospective analysis of AP radiographs, CT scans, and three-dimensional (3D) imaging data from 152 patients (192 hips) who underwent THA at our hospital between December 2020 and December 2023. This study was approved by our institutional review board, and all participants provided informed consent. The 3D imaging data of the bone represents a precise reconstruction of its shape. Accordingly, based on the definition of the RA, we measured the angle between the cup axis and the coronal plane on 3D imaging data, which we denoted as RA3D, using specialized image processing software. The subsequent result substantiates the reliability of this method. Therefore, we adopted the average value of four RA3Ds as the standard value of RA. This study compares the measurement accuracy of our new method with that of two established techniques: Lewinnek’s and Pradhan’s method. Data measurement: ( 1 ) Lewinnek’s and Pradhan’s method: Measure the RA using Lewinnek’s and Pradhan’s method in AP radiographs, recorded as RAp and RAl, respectively (Fig. 3); ( 2 ) The new method: Measure the RI in AP radiographs and AA in CT, respectively, and calculate the RA using Eq. 1, recorded as RAn. ( 3 ) Measurement of RA3D: Measure the RA on CT 3D imaging data using AW VolumeShare 7 (GE Medical System Co Ltd, US) image processing software (Fig. 4). The RAl, RAp, RAn and RA3D of 192 hips were measured by two experienced surgeons in our hospital without prior communication. The results were measured again after 1 week. Figure 3: Two traditional methods of measuring the RA. The opening of the cup is projected into an ellipse on the AP radiographs. a: Lewinnek’s method: measure the major and minor axes of the ellipse, recorded as LA and SA, respectively. RAl = sin − 1 (SA/LA). b: locate one-fifth of the major axis. The perpendicular intersection with the major axis and the ellipse, respectively, and the distance between the two intersection points is denoted by “p”. RAp = sin − 1 (p/(0.4×D)). Figure 4: 3D method using AW VolumeShare 7. a: The software provides three perpendicular planes with the red dot as the origin (the orange plane, the green plane and the blue plane), representing the coronal, horizontal and sagittal planes respectively. In one plane, the other two planes are projected into straight lines. The three planes can be adjusted to fit the patient in different positions. b: First, adjust the orange plane to coincide with the patient's coronal plane (plane ABCO in Fig. 1). Second, in orange plane, adjust the blue line to parallel to the cup axis, and then, the blue plane is the plane OBE in Fig. 1. RA is the angle between the orange line and cup axis ( β ). Statistics: SPSS 25.0 (IBM, USA) was used for statistical analysis, and a P value of less than or equal to 0.05 was considered significant with a 95% confidence interval. Reliability was defined as the consistency of measured values, and accuracy was defined as the proximity to the reference values. The intraclass correlation coefficient (ICC) and 95% confidence interval (CI) were calculated to compare the intraobserver and interobserver reliability. A paired samples t test was used to compare the difference between the measured values of each method and the reference values. The measurement data are expressed as‾x ± s. Result We assessed the intraobserver and interobserver reliability of the four methods, with the results presented in Table 1 . The 3D method exhibits exceptionally high intraobserver and interobserver ICCs, affirming the reliability of using the mean RA3D as actual RA values. The new method also boasts high intraobserver and interobserver ICCs. In contrast, Lewinnek’s and Pradhan’s methods show lower intraobserver and interobserver ICCs. The comparison between the measured values from each method and standard values is detailed in Table 2 . Notably, the difference between RAn and the standard values is the smallest, with the least degree of dispersion. Table 1 Intraobserver and interobserver reliability. Measurement method Interobserver ICC (95% CI) Intraobserver ICC (95% CI) 3D (RA3D) First measurement 0.989(0.986–0.992) Observer A 0.992(0.988–0.995) Second measurement 0.989(0.986–0.992) Observer B 0.993(0.989–0.995) New (RAn) First measurement 0.979(0.969–0.985) Observer A 0.967(0.951–0.979) Second measurement 0.961(0.941–0.974) Observer B 0.978(0.967–0.986) Pradhan (RAp) First measurement 0.823(0.742–0.880) Observer A 0.904(0.865–0.933) Second measurement 0.913(0.875–0.940) Observer B 0.915(0.875–0.941) Lewinnek (RAl) First measurement 0.859(0.792-0.900) Observer A 0.834(0.757–0.888) Second measurement 0.832(0.754–0.887) Observer B 0.917(0.877–0.944) Table 2 Measured values of other methods compared with standard values. Measurement method Observer Measurement Comparison with standard values Difference * (Mean ± SD) Absolute difference (Mean ± SD) Maximum absolute difference New method (RAn) A First measurement 1.19 ± 2.27 1.82 ± 1.80 5.53 Second measurement 1.34 ± 3.19 2.65 ± 2.20 6.39 B First measurement 1.64 ± 2.33 2.12 ± 1.90 5.89 Second measurement 0.99 ± 2.24 1.80 ± 1.66 5.35 Pradhan’s method (RAp) A First measurement -2.14 ± 4.17 3.69 ± 2.87 15.52 Second measurement -2.68 ± 4.80 4.42 ± 3.24 13.33 B First measurement -1.71 ± 3.96 3.18 ± 2.90 17.70 Second measurement -3.10 ± 4.08 4.13 ± 3.03 16.75 Lewinnek’s method (RAl) A First measurement -3.13 ± 4.37 4.36 ± 3.15 15.97 Second measurement 0.21 ± 5.63 4.36 ± 3.54 15.52 B First measurement -0.76 ± 4.66 3.42 ± 3.24 18.32 Second measurement -3.82 ± 4.30 4.70 ± 3.32 17.40 * A positive number indicates that the measured values were greater than standard values. Conversely, a negative number indicated that the measured values were less than standard values. Discussion Accurately measuring the cup angle following THA and comparing it with the "safe zone" 2,3 is crucial for assessing surgical outcomes and guiding surgeons, particularly younger ones, in enhancing their surgical techniques. Moreover, for patients experiencing recurrent dislocation post-THA, precise measurement of the cup angle can inform treatment decisions. Various methods for measuring anteversion have been documented in the literature. The Lewinnek’s method 2 , for instance, employs trigonometric functions to calculate the major and minor axes of the projected ellipse to determine anteversion. Pradhan's method 4 utilizes distinct reference points and lines within the ellipse. Liaw 6 developed a protractor for use on radiographs, simplifying the process of measurement and calculation. Widmer 5 observed that within a specific range, the ratio of the ellipse’s major to minor axis is nearly linearly related to the anteversion angle, leading to the design of a simpler method based on Lewinnek's technique. Callanan 3 utilized the specialized Martell Hip Analysis Suite™ software (Chicago, IL) to analyze hip radiographs and establish the well-known "Callanan safe zone" for acetabular angles. The methods described above measure the RA, typically through the analysis of parameters associated with the ellipse projection on AP hip radiographs, thereby estimating the RA indirectly. During practical application, however, we identified several limitations with these methods: 1. Positional Variability : While some studies have validated the high accuracy of these methods 5, 8, 12 , most validations were conducted using in vitro models. Clinically, patient positioning can deviate from the ideal due to factors like pain, making it challenging to maintain the precise alignment required for accurate measurements. Patients may rotate their bodies instead of aligning perfectly with the X-ray beam, leading to measurement discrepancies. 2. Ellipse identification : Identifying the projected ellipse is a critical initial step. However, in practice, the complex structures of the prosthetic components, such as the metallic edges, coatings, and grooves designed to secure the liner, can create multiple overlapping ellipses on AP radiographs. These projections, further obscured by the femoral head prosthesis, bone, and soft tissues, appear as a series of confusing arcs, making it difficult to precisely define the ellipse and establish the necessary reference points and lines. 3. Trigonometric transformation amplifies errors : Due to the reliance on trigonometric transformations, even minor inaccuracies during measurement can amplify into great errors in the final RA calculations. 4. Anteversion vs. retroversion determination : AP radiographs alone cannot distinguish between anteversion and retroversion, necessitating additional imaging modalities such as CT scans or lateral radiographs. While some of these limitations have been addressed by advanced software solutions, their use is not widespread, and the improvements offered are limited. Yao 13 measured the RA on a cross-table lateral radiograph. In this procedure, the X-ray is directed perpendicularly to the OBE plane (as depicted in Fig. 1), resulting in a radiograph parallel to this plane. The RA is defined as the angle between the cup axis and the long axis of the body in the cross-table lateral view. However, cross-table lateral radiographs are not commonly used in clinical practice due to their complex execution, which involves multiple radiations and adjustments of the X-ray direction. Ghelman 10 noted that this method has low accuracy and yields highly variable results even when the same observer measures different cross-table lateral radiographs of the same patient. Numerous studies have quantified CT measurements (as depicted in Fig. 2b). For instance, a retrospective analysis of 42 patients by Ghelman 10 revealed higher intraobserver and interobserver reliability for CT compared to AP radiographs, as well as independence from variations in patient positioning. It is important to note, however, that the anteversion angle measured via CT is specifically referred to as the AA. Unfortunately, there is currently no established safe zone for AA to assess acetabular angles. This distinction is often overlooked in both clinical practice and literature, where AA and RA are frequently conflated. As illustrated in Table 3 , the relationship between AA, RA, and RI (as defined by Eq. 1) demonstrates that AA and RA are not equivalent, with significant differences between them. Thus, it is clearly inappropriate to compare the AA obtained from CT scans with the RA safe zones proposed by Lewinnek 2 and Callanan 3 . In reviewing the association between acetabular cup position and dislocation, Seagrave 7 observed that various studies employed differing definitions and methods for measuring anteversion. This inconsistency represents a significant confounding factor when comparing acetabular anteversion against target values. Seagrave recommends adopting a more standardized approach to measurement. Table 3 Examples of the mathematical relationships between the RI, RA and AA. RI(°) 30 30 30 40 40 40 50 50 50 RA(°) 5 15 25 5 15 25 5 15 25 AA(°) 9.92 28.19 43.00 7.75 22.63 35.96 6.52 19.28 31.33 In studies employing in vitro models 5, 8, 12 , researchers can directly ascertain the anteversion angle as a standard value. However, in both this study and clinical practice, the actual cup anteversion angle within a patient's body cannot be directly obtained. The 3D method in this study was implemented by precisely defining the RA in a digital model that accurately mirrors the pelvic structure. Consequently, we posit that the measured values from this method can be considered a reliable reference for the actual RA. The extremely high intraobserver and interobserver ICC of RA3Ds further support the accuracy and reliability of the 3D method. The 3D method notably remains unaffected by the patient's position. However, it does have its limitations: it requires specialized image processing software, which means observers must undergo training; the procedure can be intricate, and the use of 3D imaging contributes to higher costs. The new method offers a more straightforward operation and is less influenced by the position of the pelvis compared to existing techniques. AP radiographs and CT scans are standard clinical procedures that do not add additional costs. Our study demonstrated that the new method boasts higher intraobserver and interobserver reliability as well as greater accuracy than the traditional approach. It is important to note, however, that the new method is not entirely immune to variations in pelvic position. While the measurement of the AA on CT scans remains unaffected by pelvic rotation, the measurement of the RI on AP radiographs does show some sensitivity. Using mathematical models, we find that for a patient with an actual RI of 40° and a real RA of 20°, a 5° rotation of the pelvis toward the unaffected side (resulting in the affected hip moving forward and the healthy hip moving backward) would yield a theoretically measured RI of 38.47° on AP radiographs. The theoretical RA calculated using the new method would be 19.41°, a deviation of only 0.59° from the actual value. In contrast, the theoretical RA measured using Lewinnek’s and Pradhan’s methods, without considering other potential measurement errors, would be 23.16°, representing an increase of 3.16°. This clearly indicates that changes in pelvic rotation have a minimal impact on the new method. We observed that recent years have seen a growing body of literature examining the impact of pelvic motion and tilt on acetabular orientation, while challenging the traditional concept of the "safe zone" 14,15 . The new method proves equally effective for measuring RA in both standing and sitting positions, provided that the AP and CT data are complete. Shortcomings: While this study improves the accuracy of measuring RA utilizing basic clinical data such as AP radiographs and CT scans, when compared to traditional methods, it is worth noting that in scenarios where advanced data, software, and tools are available, including 3D imaging data and even joint surgical robotic systems 16 , other methods may potentially achieve even higher levels of accuracy. Conclusion Leveraging CT data, the new method introduced in this study enhances the accuracy of acetabular radiographic anteversion measurements. The 3D method is a sophisticated but highly accurate measurement technique. Abbreviations 3D: three-dimensional THA: total hip arthroplasty RA: radiographic anteversion AA: anatomical anteversion OA: operative anteversion RI: radiographic inclination AP: anteroposterior ICC: intraclass correlation coefficient CI: confidence interval Declarations Ethics approval and consent to participate: This study was approved by the review board of the Affiliated Hospital of Qingdao University (QYFY WZLL 26920) and was carried out in accordance with the Declaration of Helsinki. Informed consent was obtained from all individual participants included in the study. Consent for publication: Patients signed informed consent regarding publishing their data and photographs. Availability of data and materials: None. Competing interests: The authors declare that they have no competing interests. Funding: None. Authors' contributions: WW wrote the paper and analysis the data. ZZ, ZH, CL and QW collected the data. HZ designed the whole study. All authors have read and approved the final manuscript. Acknowledgements: None References Murray DW. The definition and measurement of acetabular orientation. J Bone Joint Surg Br. 1993;75:228–232. Lewinnek G E, Lewis J L, Tarr R, Compere C L, Zimmerman J R. Dislocations after total hip-replacement arthroplasties. J Bone Joint Surg Am 1978; 60 (2): 217-20. Callanan MC, Jarrett B, Bragdon CR, et al. The John Charnley Award: risk factors for cup malpositioning: quality improvement through a joint registry at a tertiary hospital. Clin Orthop Relat Res. 2011;469(2):319-329. Pradhan R. Planar anteversion of the acetabular cup as determined from plain anteroposterior radiographs. J Bone Joint Surg Br. 1999;81:431–5. Widmer KH. A simplified method to determine acetabular cup anteversion from plain radiographs. J Arthroplasty. 2004;19(3):387-390. Liaw CK, Hou SM, Yang RS, Wu TY, Fuh CS. A new tool for measuring cup orientation in total hip arthroplasties from plain radiographs. Clin Orthop Relat Res. 2006;451:134-139. Seagrave KG, Troelsen A, Malchau H, Husted H, Gromov K. Acetabular cup position and risk of dislocation in primary total hip arthroplasty. Acta Orthop. 2017;88(1):10-17. Lee GC, Lee SH, Kang SW, Park HS, Jo S. Accuracy of planar anteversion measurements using anteroposterior radiographs. BMC Musculoskelet Disord. 2019;20(1):586. Huo J, Huang G, Han D, et al. Value of 3D preoperative planning for primary total hip arthroplasty based on artificial intelligence technology. J Orthop Surg Res. 2021;16(1):156. Ghelman B, Kepler CK, Lyman S, Della Valle AG. CT outperforms radiography for determination of acetabular cup version after THA. Clin Orthop Relat Res. 2009;467(9):2362-2370. Yoshimine F. The safe-zones for combined cup and neck anteversions that fulfill the essential range of motion and their optimum combination in total hip replacements. J Biomech. 2006;39(7):1315-1323. Liaw CK, Yang RS, Hou SM, Wu TY, Fuh CS. Measurement of the acetabular cup anteversion on simulated radiographs. J Arthroplasty. 2009;24(3):468-474. Yao L, Yao J, Gold RH. Measurement of acetabular version on the axiolateral radiograph. Clin Orthop Relat Res. 1995;316: 106–111. Tang H, Zhao Y, Wang S, et al. Conversion of the Sagittal Functional Safe Zone to the Coronal Plane Using a Mathematical Algorithm: The Reason for Failure of the Lewinnek Safe Zone. J Bone Joint Surg Am. 2022. Dorr LD, Callaghan JJ. Death of the Lewinnek "Safe Zone". J Arthroplasty. 2019;34(1):1-2. Wang W, Zhang Z, Wang G, Rong C, Xu H, Lu X, Liu Y, Li C, Zhang H. Prospective randomized controlled trial on the accuracy of prosthesis positioning in total hip arthroplasty assisted by a newly designed whole-process robotic arm. Int Orthop. 2023 Feb;47(2):413-419. 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-4862348","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":337051800,"identity":"73e4955c-dae6-47a7-ab9a-7bd1180eca4e","order_by":0,"name":"Wenzhe Wang","email":"","orcid":"","institution":"the Affiliated Hospital of Qingdao University","correspondingAuthor":false,"prefix":"","firstName":"Wenzhe","middleName":"","lastName":"Wang","suffix":""},{"id":337051805,"identity":"ce717384-6117-4a9c-bae1-0b637b9a16f3","order_by":1,"name":"Zian Zhang","email":"","orcid":"","institution":"the Affiliated Hospital of Qingdao University","correspondingAuthor":false,"prefix":"","firstName":"Zian","middleName":"","lastName":"Zhang","suffix":""},{"id":337051807,"identity":"9b5d9c4f-35b9-46d0-a9f6-1927864c16d5","order_by":2,"name":"Zhenchao Huang","email":"","orcid":"","institution":"the Affiliated Hospital of Qingdao University","correspondingAuthor":false,"prefix":"","firstName":"Zhenchao","middleName":"","lastName":"Huang","suffix":""},{"id":337051808,"identity":"b07184ad-2e82-4ed5-bfcc-4608e1e8d5f8","order_by":3,"name":"Chang Liu","email":"","orcid":"","institution":"the Affiliated Hospital of Qingdao University","correspondingAuthor":false,"prefix":"","firstName":"Chang","middleName":"","lastName":"Liu","suffix":""},{"id":337051809,"identity":"11c5b25c-dd74-4624-a0d1-e5579d20d1a1","order_by":4,"name":"Qianqian Wang","email":"","orcid":"","institution":"the Affiliated Hospital of Qingdao University","correspondingAuthor":false,"prefix":"","firstName":"Qianqian","middleName":"","lastName":"Wang","suffix":""},{"id":337051810,"identity":"8f03d696-ceea-4028-902c-8e6ee9590244","order_by":5,"name":"Haining Zhang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+klEQVRIiWNgGAWjYBACAwbGBoYEMIOBgflPhQ0PP38DCVoYeM6kyUjOOEBICzKDt+WwjUFDAn4t5uyH2x483FFrb85+9vALyYbzPAYMBxg/fMzBrcWyJ7HdIPHMcWbLnrw0C8Mdt3nMmRuYJWduw+OwA4ltEoltx9gMDuSYAfXe5rFsOMDGzItPy/mHYC08BuffmBkcbDvHY3AggYCWG2BbaiQMbuQYP2xsO0CMFrAtBwwMbrwxY2Y4k8wjOeNgM36/nE9/Jvmzrc7e4HyO8WeGCjt7fv7mgx8+4tECBYdBBJsEhAOMXCJAHYhg/kCM0lEwCkbBKBh5AABh9Fj6GuHwaQAAAABJRU5ErkJggg==","orcid":"","institution":"the Affiliated Hospital of Qingdao University","correspondingAuthor":true,"prefix":"","firstName":"Haining","middleName":"","lastName":"Zhang","suffix":""}],"badges":[],"createdAt":"2024-08-05 13:29:41","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4862348/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4862348/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":64384079,"identity":"800c88f4-c342-406b-a8b4-fb0a5bf528c3","added_by":"auto","created_at":"2024-09-12 12:15:25","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":89974,"visible":true,"origin":"","legend":"\u003cp\u003eDiagram of acetabular cup abduction and anteversion.\u003c/p\u003e","description":"","filename":"Figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-4862348/v1/a9a897481aed86b07344f536.png"},{"id":64384937,"identity":"2456cffb-13b5-4609-8dce-bb84d6e4b990","added_by":"auto","created_at":"2024-09-12 12:23:25","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":351003,"visible":true,"origin":"","legend":"\u003cp\u003eMeasurements of the RI and AA in AP radiographs. a: The angle between the projection of the cup axis on AP radiographs and the vertical line is the RI, which is equal to the angle between the long axis of the projected ellipse and horizontal line. b: On the appropriate horizontal plane of a hip CT, measure the angle between the projection of the cup axis and the coronal axis (line connecting the center points of bilateral femoral heads) as the AA (γ), which is equal to the angle between the line connecting the endpoints of the cup arc and the sagittal line.\u003c/p\u003e","description":"","filename":"Figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-4862348/v1/3e06db70b1975423fdcf0fc8.png"},{"id":64384081,"identity":"c1e86dd9-e7e3-4583-a967-762cca224d02","added_by":"auto","created_at":"2024-09-12 12:15:25","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":313628,"visible":true,"origin":"","legend":"\u003cp\u003eTwo traditional methods of measuring the RA. The opening of the cup is projected into an ellipse on the AP radiographs. a: Lewinnek’s method: measure the major and minor axes of the ellipse, recorded as LA and SA, respectively. RAl=sin\u003csup\u003e-1\u003c/sup\u003e(SA/LA). b: locate one-fifth of the major axis. The perpendicular intersection with the major axis and the ellipse, respectively, and the distance between the two intersection points is denoted by “p”. RAp=sin\u003csup\u003e-1\u003c/sup\u003e(p/(0.4×D)).\u003c/p\u003e","description":"","filename":"Figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-4862348/v1/f29b3f3c478bf75b7a0c66c1.png"},{"id":64384083,"identity":"0bf41173-fe22-4cb6-adf5-e82dc1b69a0f","added_by":"auto","created_at":"2024-09-12 12:15:25","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":819533,"visible":true,"origin":"","legend":"\u003cp\u003e3D method using AW VolumeShare 7. a: The software provides three perpendicular planes with the red dot as the origin (the orange plane, the green plane and the blue plane), representing the coronal, horizontal and sagittal planes respectively. In one plane, the other two planes are projected into straight lines. The three planes can be adjusted to fit the patient in different positions. b: First, adjust the orange plane to coincide with the patient's coronal plane (plane ABCO in Figure 1). Second, in orange plane, adjust the blue line to parallel to the cup axis, and then, the blue plane is the plane OBE in Figure 1. RA is the angle between the orange line and cup axis (\u003cstrong\u003eβ\u003c/strong\u003e).\u003c/p\u003e","description":"","filename":"Figure4.png","url":"https://assets-eu.researchsquare.com/files/rs-4862348/v1/532123d63b815d350ad60bb0.png"},{"id":64386154,"identity":"390c5887-86ab-4592-990c-922b0bb461d6","added_by":"auto","created_at":"2024-09-12 12:31:30","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2436892,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4862348/v1/a86bf17a-b769-4555-a842-4b04fb105f67.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"CT can enhance the measurement accuracy of radiographic anteversion of acetabular cup following total hip arthroplasty","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAccurately measuring acetabular cup anteversion and abduction following total hip arthroplasty (THA) is critically important for assessing the success of THA and guiding revision surgeries in cases of recurrent dislocations. Murray\u0026rsquo;s definition of anteversion and abduction is widely accepted and used as a standard in the literature\u003csup\u003e1\u003c/sup\u003e. As shown in Figure 1, Murray defined anteversion as follows: anatomical anteversion (AA): the angle between the projection of the cup axis (line OE) onto the horizontal plane (line OF) and the coronal axis (line OC); radiographic anteversion (RA): the angle between the cup axis (line OE) and the coronal plane; operative anteversion (OA): the angle between the projection of the cup axis (line OE) on the sagittal plane (line OD) and the vertical line (line OA). In addition, he defined the angle between the projection of the cup axis (line OE) on the coronal plane (line OB) and the vertical line (line OA) as radiographic inclination (RI).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFigure 1: Diagram of acetabular cup abduction and anteversion.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe methods for measuring inclination are relatively uniform. The opening of the cup is projected into an ellipse on anteroposterior (AP)\u0026nbsp;radiographs, and cup abduction is the angle between the long axis of the ellipse and the horizontal line\u003csup\u003e2\u003c/sup\u003e (the line through the lower edge of the bilateral teardrop, as shown in Figure 2a), which refers to Murray\u0026rsquo;s RI. However, the anteversion angle has been measured in various ways in different studies. Lewinnek\u003csup\u003e2\u003c/sup\u003e, Callanan\u003csup\u003e3\u003c/sup\u003e, Pradhan\u003csup\u003e4\u003c/sup\u003e, Widmer\u003csup\u003e5\u003c/sup\u003e, Liaw\u003csup\u003e6\u003c/sup\u003e measured the RA on AP radiographs using different methods\u003csup\u003e7\u003c/sup\u003e. The concept of the \u0026ldquo;anteversion safe zone\u0026rdquo; proposed by Lewinnek\u003csup\u003e2\u003c/sup\u003e and Callanan\u003csup\u003e3\u003c/sup\u003e, which is widely accepted and referenced, also refers to this definition of anteversion. However, the disadvantages of measurement on AP radiographs include large errors, low repeatability, strict requirements on patient positioning, and inability to distinguish anteversion or retroversion\u003csup\u003e2,4-8\u003c/sup\u003e. Some studies choose to measure the anteversion angle directly from a CT scan (as shown in Figure 2b), with the advantages of less error and regardless of the patient\u0026apos;s position\u003csup\u003e7,9,10\u003c/sup\u003e. However, it should be noted that the anteversion directly measured in a CT is the AA\u003csup\u003e7\u003c/sup\u003e, instead of the RA. In some studies, no distinction is made between the two definitions. It is obviously inappropriate to compare the AA measured in a CT with the RA safe zone proposed by Lewinnek and Callanan. After calculation and review of relevant literature\u003csup\u003e1,11\u003c/sup\u003e, we found that the mathematics relationship shown in Equation 1 existed between several angles. We designed a new measurement method that improves the measurement accuracy of RA in AP radiographs with CT data.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFigure 2. Measurements of the RI and AA in AP radiographs. a: The angle between the projection of the cup axis on AP radiographs and the vertical line is the RI, which is equal to the angle between the long axis of the projected ellipse and horizontal line. b: On the appropriate horizontal plane of a hip CT, measure the angle between the projection of the cup axis and the coronal axis (line connecting the center points of bilateral femoral heads) as the AA (\u0026gamma;), which is equal to the angle between the line connecting the endpoints of the cup arc and the sagittal line.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRA=tan\u003csup\u003e-1\u003c/sup\u003e(tan (AA)\u003c/strong\u003e\u003cstrong\u003e\u0026times;sin (RI\u003c/strong\u003e\u003cstrong\u003e)) \u0026nbsp; \u0026nbsp; \u0026nbsp;Equation 1\u003c/strong\u003e\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cp\u003eTo compare the accuracy of various methods, we conducted a retrospective analysis of AP radiographs, CT scans, and three-dimensional (3D) imaging data from 152 patients (192 hips) who underwent THA at our hospital between December 2020 and December 2023. This study was approved by our institutional review board, and all participants provided informed consent.\u003c/p\u003e \u003cp\u003eThe 3D imaging data of the bone represents a precise reconstruction of its shape. Accordingly, based on the definition of the RA, we measured the angle between the cup axis and the coronal plane on 3D imaging data, which we denoted as RA3D, using specialized image processing software. The subsequent result substantiates the reliability of this method. Therefore, we adopted the average value of four RA3Ds as the standard value of RA. This study compares the measurement accuracy of our new method with that of two established techniques: Lewinnek\u0026rsquo;s and Pradhan\u0026rsquo;s method.\u003c/p\u003e \u003cp\u003eData measurement: (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) Lewinnek\u0026rsquo;s and Pradhan\u0026rsquo;s method: Measure the RA using Lewinnek\u0026rsquo;s and Pradhan\u0026rsquo;s method in AP radiographs, recorded as RAp and RAl, respectively (Fig.\u0026nbsp;3); (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) The new method: Measure the RI in AP radiographs and AA in CT, respectively, and calculate the RA using Eq.\u0026nbsp;1, recorded as RAn. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) Measurement of RA3D: Measure the RA on CT 3D imaging data using AW VolumeShare 7 (GE Medical System Co Ltd, US) image processing software (Fig.\u0026nbsp;4). The RAl, RAp, RAn and RA3D of 192 hips were measured by two experienced surgeons in our hospital without prior communication. The results were measured again after 1 week.\u003c/p\u003e \u003cp\u003eFigure 3: Two traditional methods of measuring the RA. The opening of the cup is projected into an ellipse on the AP radiographs. a: Lewinnek\u0026rsquo;s method: measure the major and minor axes of the ellipse, recorded as LA and SA, respectively. RAl\u0026thinsp;=\u0026thinsp;sin\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e(SA/LA). b: locate one-fifth of the major axis. The perpendicular intersection with the major axis and the ellipse, respectively, and the distance between the two intersection points is denoted by \u0026ldquo;p\u0026rdquo;. RAp\u0026thinsp;=\u0026thinsp;sin\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e(p/(0.4\u0026times;D)).\u003c/p\u003e \u003cp\u003eFigure 4: 3D method using AW VolumeShare 7. a: The software provides three perpendicular planes with the red dot as the origin (the orange plane, the green plane and the blue plane), representing the coronal, horizontal and sagittal planes respectively. In one plane, the other two planes are projected into straight lines. The three planes can be adjusted to fit the patient in different positions. b: First, adjust the orange plane to coincide with the patient's coronal plane (plane ABCO in Fig.\u0026nbsp;1). Second, in orange plane, adjust the blue line to parallel to the cup axis, and then, the blue plane is the plane OBE in Fig.\u0026nbsp;1. RA is the angle between the orange line and cup axis (\u003cb\u003eβ\u003c/b\u003e).\u003c/p\u003e \u003cp\u003eStatistics: SPSS 25.0 (IBM, USA) was used for statistical analysis, and a P value of less than or equal to 0.05 was considered significant with a 95% confidence interval. Reliability was defined as the consistency of measured values, and accuracy was defined as the proximity to the reference values. The intraclass correlation coefficient (ICC) and 95% confidence interval (CI) were calculated to compare the intraobserver and interobserver reliability. A paired samples t test was used to compare the difference between the measured values of each method and the reference values. The measurement data are expressed as\u0026oline;x\u0026thinsp;\u0026plusmn;\u0026thinsp;s.\u003c/p\u003e"},{"header":"Result","content":"\u003cp\u003eWe assessed the intraobserver and interobserver reliability of the four methods, with the results presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The 3D method exhibits exceptionally high intraobserver and interobserver ICCs, affirming the reliability of using the mean RA3D as actual RA values. The new method also boasts high intraobserver and interobserver ICCs. In contrast, Lewinnek\u0026rsquo;s and Pradhan\u0026rsquo;s methods show lower intraobserver and interobserver ICCs. The comparison between the measured values from each method and standard values is detailed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Notably, the difference between RAn and the standard values is the smallest, with the least degree of dispersion.\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\u003eIntraobserver and interobserver reliability.\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=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMeasurement method\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eInterobserver ICC (95% CI)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eIntraobserver ICC (95% CI)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e3D\u003c/p\u003e \u003cp\u003e(RA3D)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFirst measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.989(0.986\u0026ndash;0.992)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eObserver A\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.992(0.988\u0026ndash;0.995)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSecond measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.989(0.986\u0026ndash;0.992)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eObserver B\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.993(0.989\u0026ndash;0.995)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eNew\u003c/p\u003e \u003cp\u003e(RAn)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFirst measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.979(0.969\u0026ndash;0.985)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eObserver A\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.967(0.951\u0026ndash;0.979)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSecond measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.961(0.941\u0026ndash;0.974)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eObserver B\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.978(0.967\u0026ndash;0.986)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePradhan\u003c/p\u003e \u003cp\u003e(RAp)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFirst measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.823(0.742\u0026ndash;0.880)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eObserver A\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.904(0.865\u0026ndash;0.933)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSecond measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.913(0.875\u0026ndash;0.940)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eObserver B\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.915(0.875\u0026ndash;0.941)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eLewinnek\u003c/p\u003e \u003cp\u003e(RAl)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFirst measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.859(0.792-0.900)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eObserver A\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.834(0.757\u0026ndash;0.888)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSecond measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.832(0.754\u0026ndash;0.887)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eObserver B\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.917(0.877\u0026ndash;0.944)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \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\u003eMeasured values of other methods compared with standard values.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\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=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eMeasurement method\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eObserver\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eMeasurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c6\" namest=\"c4\"\u003e \u003cp\u003eComparison with standard values\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDifference\u003cb\u003e*\u003c/b\u003e (Mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eAbsolute difference (Mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMaximum absolute difference\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eNew method\u003c/p\u003e \u003cp\u003e(RAn)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFirst measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.19\u0026thinsp;\u0026plusmn;\u0026thinsp;2.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.82\u0026thinsp;\u0026plusmn;\u0026thinsp;1.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.53\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSecond measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.34\u0026thinsp;\u0026plusmn;\u0026thinsp;3.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.65\u0026thinsp;\u0026plusmn;\u0026thinsp;2.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.39\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFirst measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.64\u0026thinsp;\u0026plusmn;\u0026thinsp;2.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.12\u0026thinsp;\u0026plusmn;\u0026thinsp;1.90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.89\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSecond measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.99\u0026thinsp;\u0026plusmn;\u0026thinsp;2.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.80\u0026thinsp;\u0026plusmn;\u0026thinsp;1.66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.35\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003ePradhan\u0026rsquo;s method\u003c/p\u003e \u003cp\u003e(RAp)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFirst measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-2.14\u0026thinsp;\u0026plusmn;\u0026thinsp;4.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.69\u0026thinsp;\u0026plusmn;\u0026thinsp;2.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e15.52\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSecond measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-2.68\u0026thinsp;\u0026plusmn;\u0026thinsp;4.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.42\u0026thinsp;\u0026plusmn;\u0026thinsp;3.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e13.33\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFirst measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-1.71\u0026thinsp;\u0026plusmn;\u0026thinsp;3.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.18\u0026thinsp;\u0026plusmn;\u0026thinsp;2.90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e17.70\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSecond measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-3.10\u0026thinsp;\u0026plusmn;\u0026thinsp;4.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.13\u0026thinsp;\u0026plusmn;\u0026thinsp;3.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e16.75\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003eLewinnek\u0026rsquo;s method\u003c/p\u003e \u003cp\u003e(RAl)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFirst measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-3.13\u0026thinsp;\u0026plusmn;\u0026thinsp;4.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.36\u0026thinsp;\u0026plusmn;\u0026thinsp;3.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e15.97\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSecond measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.21\u0026thinsp;\u0026plusmn;\u0026thinsp;5.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.36\u0026thinsp;\u0026plusmn;\u0026thinsp;3.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e15.52\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFirst measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-0.76\u0026thinsp;\u0026plusmn;\u0026thinsp;4.66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.42\u0026thinsp;\u0026plusmn;\u0026thinsp;3.24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e18.32\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSecond measurement\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-3.82\u0026thinsp;\u0026plusmn;\u0026thinsp;4.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.70\u0026thinsp;\u0026plusmn;\u0026thinsp;3.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e17.40\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e* A positive number indicates that the measured values were greater than standard values. Conversely, a negative number indicated that the measured values were less than standard values.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eAccurately measuring the cup angle following THA and comparing it with the \"safe zone\"\u003csup\u003e2,3\u003c/sup\u003e is crucial for assessing surgical outcomes and guiding surgeons, particularly younger ones, in enhancing their surgical techniques. Moreover, for patients experiencing recurrent dislocation post-THA, precise measurement of the cup angle can inform treatment decisions. Various methods for measuring anteversion have been documented in the literature. The Lewinnek\u0026rsquo;s method\u003csup\u003e2\u003c/sup\u003e, for instance, employs trigonometric functions to calculate the major and minor axes of the projected ellipse to determine anteversion. Pradhan's method\u003csup\u003e4\u003c/sup\u003e utilizes distinct reference points and lines within the ellipse. Liaw \u003csup\u003e6\u003c/sup\u003e developed a protractor for use on radiographs, simplifying the process of measurement and calculation. Widmer\u003csup\u003e5\u003c/sup\u003e observed that within a specific range, the ratio of the ellipse\u0026rsquo;s major to minor axis is nearly linearly related to the anteversion angle, leading to the design of a simpler method based on Lewinnek's technique. Callanan \u003csup\u003e3\u003c/sup\u003e utilized the specialized Martell Hip Analysis Suite\u0026trade; software (Chicago, IL) to analyze hip radiographs and establish the well-known \"Callanan safe zone\" for acetabular angles.\u003c/p\u003e \u003cp\u003eThe methods described above measure the RA, typically through the analysis of parameters associated with the ellipse projection on AP hip radiographs, thereby estimating the RA indirectly. During practical application, however, we identified several limitations with these methods:\u003c/p\u003e \u003cp\u003e \u003cb\u003e1. Positional Variability\u003c/b\u003e: While some studies have validated the high accuracy of these methods \u003csup\u003e5, 8, 12\u003c/sup\u003e, most validations were conducted using in vitro models. Clinically, patient positioning can deviate from the ideal due to factors like pain, making it challenging to maintain the precise alignment required for accurate measurements. Patients may rotate their bodies instead of aligning perfectly with the X-ray beam, leading to measurement discrepancies. 2. \u003cb\u003eEllipse identification\u003c/b\u003e: Identifying the projected ellipse is a critical initial step. However, in practice, the complex structures of the prosthetic components, such as the metallic edges, coatings, and grooves designed to secure the liner, can create multiple overlapping ellipses on AP radiographs. These projections, further obscured by the femoral head prosthesis, bone, and soft tissues, appear as a series of confusing arcs, making it difficult to precisely define the ellipse and establish the necessary reference points and lines. 3. \u003cb\u003eTrigonometric transformation amplifies errors\u003c/b\u003e: Due to the reliance on trigonometric transformations, even minor inaccuracies during measurement can amplify into great errors in the final RA calculations. 4. \u003cb\u003eAnteversion vs. retroversion determination\u003c/b\u003e: AP radiographs alone cannot distinguish between anteversion and retroversion, necessitating additional imaging modalities such as CT scans or lateral radiographs. While some of these limitations have been addressed by advanced software solutions, their use is not widespread, and the improvements offered are limited.\u003c/p\u003e \u003cp\u003eYao \u003csup\u003e13\u003c/sup\u003e measured the RA on a cross-table lateral radiograph. In this procedure, the X-ray is directed perpendicularly to the OBE plane (as depicted in Fig.\u0026nbsp;1), resulting in a radiograph parallel to this plane. The RA is defined as the angle between the cup axis and the long axis of the body in the cross-table lateral view. However, cross-table lateral radiographs are not commonly used in clinical practice due to their complex execution, which involves multiple radiations and adjustments of the X-ray direction. Ghelman \u003csup\u003e10\u003c/sup\u003e noted that this method has low accuracy and yields highly variable results even when the same observer measures different cross-table lateral radiographs of the same patient.\u003c/p\u003e \u003cp\u003eNumerous studies have quantified CT measurements (as depicted in Fig.\u0026nbsp;2b). For instance, a retrospective analysis of 42 patients by Ghelman \u003csup\u003e10\u003c/sup\u003e revealed higher intraobserver and interobserver reliability for CT compared to AP radiographs, as well as independence from variations in patient positioning. It is important to note, however, that the anteversion angle measured via CT is specifically referred to as the AA. Unfortunately, there is currently no established safe zone for AA to assess acetabular angles. This distinction is often overlooked in both clinical practice and literature, where AA and RA are frequently conflated. As illustrated in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, the relationship between AA, RA, and RI (as defined by Eq.\u0026nbsp;1) demonstrates that AA and RA are not equivalent, with significant differences between them. Thus, it is clearly inappropriate to compare the AA obtained from CT scans with the RA safe zones proposed by Lewinnek\u003csup\u003e2\u003c/sup\u003e and Callanan\u003csup\u003e3\u003c/sup\u003e. In reviewing the association between acetabular cup position and dislocation, Seagrave\u003csup\u003e7\u003c/sup\u003e observed that various studies employed differing definitions and methods for measuring anteversion. This inconsistency represents a significant confounding factor when comparing acetabular anteversion against target values. Seagrave recommends adopting a more standardized approach to measurement.\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\u003eExamples of the mathematical relationships between the RI, RA and AA.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"10\"\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=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRI(\u0026deg;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRA(\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAA(\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e28.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e43.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e22.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e35.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e6.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e19.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e31.33\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eIn studies employing in vitro models\u003csup\u003e5, 8, 12\u003c/sup\u003e, researchers can directly ascertain the anteversion angle as a standard value. However, in both this study and clinical practice, the actual cup anteversion angle within a patient's body cannot be directly obtained. The 3D method in this study was implemented by precisely defining the RA in a digital model that accurately mirrors the pelvic structure. Consequently, we posit that the measured values from this method can be considered a reliable reference for the actual RA. The extremely high intraobserver and interobserver ICC of RA3Ds further support the accuracy and reliability of the 3D method. The 3D method notably remains unaffected by the patient's position. However, it does have its limitations: it requires specialized image processing software, which means observers must undergo training; the procedure can be intricate, and the use of 3D imaging contributes to higher costs.\u003c/p\u003e \u003cp\u003eThe new method offers a more straightforward operation and is less influenced by the position of the pelvis compared to existing techniques. AP radiographs and CT scans are standard clinical procedures that do not add additional costs. Our study demonstrated that the new method boasts higher intraobserver and interobserver reliability as well as greater accuracy than the traditional approach. It is important to note, however, that the new method is not entirely immune to variations in pelvic position. While the measurement of the AA on CT scans remains unaffected by pelvic rotation, the measurement of the RI on AP radiographs does show some sensitivity. Using mathematical models, we find that for a patient with an actual RI of 40\u0026deg; and a real RA of 20\u0026deg;, a 5\u0026deg; rotation of the pelvis toward the unaffected side (resulting in the affected hip moving forward and the healthy hip moving backward) would yield a theoretically measured RI of 38.47\u0026deg; on AP radiographs. The theoretical RA calculated using the new method would be 19.41\u0026deg;, a deviation of only 0.59\u0026deg; from the actual value. In contrast, the theoretical RA measured using Lewinnek\u0026rsquo;s and Pradhan\u0026rsquo;s methods, without considering other potential measurement errors, would be 23.16\u0026deg;, representing an increase of 3.16\u0026deg;. This clearly indicates that changes in pelvic rotation have a minimal impact on the new method.\u003c/p\u003e \u003cp\u003eWe observed that recent years have seen a growing body of literature examining the impact of pelvic motion and tilt on acetabular orientation, while challenging the traditional concept of the \"safe zone\"\u003csup\u003e14,15\u003c/sup\u003e. The new method proves equally effective for measuring RA in both standing and sitting positions, provided that the AP and CT data are complete.\u003c/p\u003e \u003cp\u003eShortcomings: While this study improves the accuracy of measuring RA utilizing basic clinical data such as AP radiographs and CT scans, when compared to traditional methods, it is worth noting that in scenarios where advanced data, software, and tools are available, including 3D imaging data and even joint surgical robotic systems\u003csup\u003e16\u003c/sup\u003e, other methods may potentially achieve even higher levels of accuracy.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eLeveraging CT data, the new method introduced in this study enhances the accuracy of acetabular radiographic anteversion measurements. The 3D method is a sophisticated but highly accurate measurement technique.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003e3D: three-dimensional\u003c/p\u003e\n\u003cp\u003eTHA: total hip arthroplasty\u003c/p\u003e\n\u003cp\u003eRA: radiographic anteversion\u003c/p\u003e\n\u003cp\u003eAA: anatomical anteversion\u003c/p\u003e\n\u003cp\u003eOA: operative anteversion\u003c/p\u003e\n\u003cp\u003eRI: radiographic inclination\u003c/p\u003e\n\u003cp\u003eAP: anteroposterior\u003c/p\u003e\n\u003cp\u003eICC: intraclass correlation coefficient\u003c/p\u003e\n\u003cp\u003eCI: confidence interval\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 review board of the Affiliated Hospital of Qingdao University (QYFY WZLL 26920) and was carried out in accordance with the Declaration of Helsinki. Informed consent was obtained from all individual participants included in the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePatients signed informed consent regarding publishing their data and photographs.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone.\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\u003eNone.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWW wrote the paper and analysis the data. ZZ, ZH, CL and QW collected the data. HZ designed the whole study. All authors have read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMurray DW. The definition and measurement of acetabular orientation. J Bone Joint Surg Br. 1993;75:228\u0026ndash;232.\u003c/li\u003e\n\u003cli\u003eLewinnek G E, Lewis J L, Tarr R, Compere C L, Zimmerman J R. Dislocations after total hip-replacement arthroplasties. J Bone Joint Surg Am 1978; 60 (2): 217-20.\u003c/li\u003e\n\u003cli\u003eCallanan MC, Jarrett B, Bragdon CR, et al. The John Charnley Award: risk factors for cup malpositioning: quality improvement through a joint registry at a tertiary hospital. Clin Orthop Relat Res. 2011;469(2):319-329.\u003c/li\u003e\n\u003cli\u003ePradhan R. Planar anteversion of the acetabular cup as determined from plain anteroposterior radiographs. J Bone Joint Surg Br. 1999;81:431\u0026ndash;5.\u003c/li\u003e\n\u003cli\u003eWidmer KH. A simplified method to determine acetabular cup anteversion from plain radiographs. J Arthroplasty. 2004;19(3):387-390.\u003c/li\u003e\n\u003cli\u003eLiaw CK, Hou SM, Yang RS, Wu TY, Fuh CS. A new tool for measuring cup orientation in total hip arthroplasties from plain radiographs. Clin Orthop Relat Res. 2006;451:134-139.\u003c/li\u003e\n\u003cli\u003eSeagrave KG, Troelsen A, Malchau H, Husted H, Gromov K. Acetabular cup position and risk of dislocation in primary total hip arthroplasty. Acta Orthop. 2017;88(1):10-17.\u003c/li\u003e\n\u003cli\u003eLee GC, Lee SH, Kang SW, Park HS, Jo S. Accuracy of planar anteversion measurements using anteroposterior radiographs. BMC Musculoskelet Disord. 2019;20(1):586.\u003c/li\u003e\n\u003cli\u003eHuo J, Huang G, Han D, et al. Value of 3D preoperative planning for primary total hip arthroplasty based on artificial intelligence technology. J Orthop Surg Res. 2021;16(1):156.\u003c/li\u003e\n\u003cli\u003eGhelman B, Kepler CK, Lyman S, Della Valle AG. CT outperforms radiography for determination of acetabular cup version after THA. Clin Orthop Relat Res. 2009;467(9):2362-2370.\u003c/li\u003e\n\u003cli\u003eYoshimine F. The safe-zones for combined cup and neck anteversions that fulfill the essential range of motion and their optimum combination in total hip replacements. J Biomech. 2006;39(7):1315-1323.\u003c/li\u003e\n\u003cli\u003eLiaw CK, Yang RS, Hou SM, Wu TY, Fuh CS. Measurement of the acetabular cup anteversion on simulated radiographs. J Arthroplasty. 2009;24(3):468-474.\u003c/li\u003e\n\u003cli\u003eYao L, Yao J, Gold RH. Measurement of acetabular version on the axiolateral radiograph. Clin Orthop Relat Res. 1995;316: 106\u0026ndash;111.\u003c/li\u003e\n\u003cli\u003eTang H, Zhao Y, Wang S, et al. Conversion of the Sagittal Functional Safe Zone to the Coronal Plane Using a Mathematical Algorithm: The Reason for Failure of the Lewinnek Safe Zone. J Bone Joint Surg Am. 2022.\u003c/li\u003e\n\u003cli\u003eDorr LD, Callaghan JJ. Death of the Lewinnek \u0026quot;Safe Zone\u0026quot;. J Arthroplasty. 2019;34(1):1-2.\u003c/li\u003e\n\u003cli\u003eWang W, Zhang Z, Wang G, Rong C, Xu H, Lu X, Liu Y, Li C, Zhang H. Prospective randomized controlled trial on the accuracy of prosthesis positioning in total hip arthroplasty assisted by a newly designed whole-process robotic arm. Int Orthop. 2023 Feb;47(2):413-419.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Total hip arthroplasty, Anteversion, Safe zone, Measurement","lastPublishedDoi":"10.21203/rs.3.rs-4862348/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4862348/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eThis study employed a novel method to measure radiographic anteversion (RA) of acetabular cups following total hip arthroplasty (THA) and validated its accuracy in comparison to traditional methods. The new method involves measuring anatomical anteversion (AA) using CT scans and radiographic inclination (RI) from anteroposterior (AP) radiographs, followed by calculating RA through a mathematical function.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThe imaging data of 152 patients (192 hips) post-THA were retrospectively assessed twice for RA by two independent observers, utilizing Lewinnek\u0026rsquo;s method, Pradhan\u0026rsquo;s method, and the new method. Obtaining actual values ​​of RA from patient\u0026rsquo;s 3D imaging data. The intraobserver and interobserver reliability and accuracy of each method were subsequently compared.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eWhen compared to Lewinnek\u0026rsquo;s and Pradhan's method, the new method demonstrated superior intraobserver and interobserver reliability. Furthermore, the values obtained through the new method were closer to the actual values for acetabular RA.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eLeveraging CT data, the new method introduced in this study enhances the accuracy of acetabular radiographic anteversion measurements.\u003c/p\u003e","manuscriptTitle":"CT can enhance the measurement accuracy of radiographic anteversion of acetabular cup following total hip arthroplasty","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-09-12 12:15:20","doi":"10.21203/rs.3.rs-4862348/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"6097bf82-1f18-4187-bae1-a2874961891a","owner":[],"postedDate":"September 12th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-09-12T12:15:22+00:00","versionOfRecord":[],"versionCreatedAt":"2024-09-12 12:15:20","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4862348","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4862348","identity":"rs-4862348","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}