Radiographic Overall Linearity of the Forearm

Radiographic Overall Linearity of the Forearm | 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 Radiographic Overall Linearity of the Forearm Thomas Daoulas, Olivier Bozon, Michel Chammas, Louis Lancelle, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6196785/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 Purpose : This study aimed to establish a radiographic standard for a healthy forearm complex by demonstrazting consistent collinearity between three key anatomical axes: the radial neck axis, the ulnar middle third axis, and the forearm rotation axis. The goal was to provide a simple, routine radiographic measurement method and assess the reliability of this measurement. Methods : A prospective, single-center study included 50 patients with no history of upper limb trauma. Standardized bilateral anteroposterior radiographs were obtained in both neutral pronosupination and complete supination. Three anatomical axes were defined: the forearm rotation axis (AB axis), the ulnar axis (U axis), and the radial neck axis (R axis). Two angles (α and β) between these axes were measured to determine the Overall Linearity of the Forearm (OLF). Measurements were conducted using Digital Imaging System software, and both intra- and inter-observer reliability were assessed using intraclass correlation coefficients (ICC) and Pearson’s correlation coefficients. Results : The mean OLF was 4.4° ± 2.3 in neutral pronosupination and 4.0° ± 2.2 in complete supination, with low standard deviations indicating consistent parallelism between the three axes. The mean angles α and β were similar in both pronosupination and supination. Pearson’s correlation for right/left comparison was 0.75 in neutral pronosupination and 0.61 in supination. ICC values for measurement reliability were 0.805 in neutral pronosupination and 0.821 in supination, reflecting good reproducibility. Conclusion : The study established that a consistent collinearity exists among the radial neck axis, ulnar middle third axis, and forearm rotation axis in healthy forearms. This collinearity can be reliably analyzed using routine radiographic images. The Overall Linearity of the Forearm (OLF) provides a useful metric for evaluating forearm morphology and may aid in assessing pathological conditions. forearm malunion measurements anatomy Figures Figure 1 Figure 2 Figure 3 INTRODUCTION The forearm complex is a complex anatomical unit, formed by the radius and ulna, encompassing three joints: the proximal radioulnar joint, the middle radioulnar joint, and the distal radioulnar joint. The wrapping of the radius around the ulna in the axial plane, known as pronosupination, allows the hand to be oriented in space 1 , 2 . Pathological involvement of one or both forearm bones (malunion, growth disorder, congenital anomaly) leads to a modification in the morphology of the forearm complex. This pathological involvement results in a reduction in pronosupination 3 , 4 . The definition of a pathological condition of the forearm complex currently relies on comparing the pathological forearm complex to the contralateral side, which is considered healthy, using radiographic 5 or CT imaging 4 , 6 . Therefore, it always requires comparison with a forearm complex defined as healthy, as it is free from traumatic injury or acquired or congenital morphological disorder. However, no precise radiological description or definition of a healthy forearm complex is found in the literature. The primary objective of this study was to demonstrate that there is a consistent collinearity between the axis of the radial neck, the axis of the middle third of the ulnar shaft, and the arc of rotation of the forearm on a radiograph of a healthy forearm complex in a neutral pronosupination and complete supination. The secondary objective was to assess the correlation between both sides. METHODS The study was approved by the Institutional Review Board, and written consent was systematically obtained from all patients. The authors adhered to the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines for the study’s reporting. Population We conducted a prospective, single-center study. A standardized radiographic protocol was implemented, allowing for the acquisition of bilateral anteroposterior radiographs of the forearm in neutral pronosupination and complete supination in 50 patients with no history of upper limb trauma. The inclusion criteria were healthy adult volunteers who provided written consent before being included in the study. The radiographs were conducted at the expense of the study center. Radiographs were included after both authors independently reviewed and approved their quality: in the anteroposterior radiograph in complete supination, the radial styloid and biceps tuberosity had to be at 180°, and the trochlea and capitulum had to be seen in full face. In the anteroposterior radiograph in neutral pronosupination, the radial styloid and biceps tuberosity also had to be at 180°, with the trochlea and capitulum superimposed. Patients with any pathology affecting the anatomy of the forearm complex (traumatic history, congenital, or acquired anomalies of the forearm complex) were excluded. The sample size was calculated using the method described by Harrison et al. 7 . The method described by Harrison determines sample size by ensuring sufficient statistical power to detect differences in radiographic measurements. It involves calculating the required sample size based on the variability of the measurements (standard deviation) and the desired level of precision or detectable difference. This approach was initially outlined on radiographic analysis methods, where they applied it to lumbar lordosis measurements. Radiographic Measurements We defined three axes applicable to anteroposterior radiographs of the forearm in neutral pronosupination and complete supination (Fig. 1 ). The first axis (AB axis), or forearm rotation axis, connected the center of the radial head and the center of the sigmoid notch (defined as the most radial portion of the notch) of the radius at the wrist. The second axis (R axis), or radial neck axis, was defined by the bisector of the radial neck cortices. The last axis (U axis), or ulnar axis, corresponded to the axis of the middle third of the ulnar shaft. The ulna was divided into three equal parts, and the U axis was defined by the center-medullary axis of the middle third. Based on these three axes, two angles were defined: the angle α between the AB axis and the R axis, and the angle β between the AB axis and the U axis (Fig. 2 ). The vertice of angle α was proximal, that of angle β was distal. These two angles were summed to define the Overall Linearity of the Forearm (OLF). These measurements were performed on anteroposterior radiographs of the forearm in neutral pronosupination and complete supination, and compared to the contralateral side. The Digital Imaging System software (GE Healthcare, Piscataway, NJ) was used for the measurements. Two surgeons specialized in upper limb surgery independently performed the measurements. Sex, age, and the side involved were recorded. Statistical Analysis Inter-observer reproducibility and right-left angle comparisons in the same patient were evaluated using Pearson's correlation. Correlation coefficients (r) between 0.60 and 0.80 were considered good, and those of 0.80 or higher were considered excellent. Measurement reliability was calculated using the intraclass correlation coefficient (ICC), expressed with its 95% confidence interval. The ICC was classified as poor below 0.50, moderate between 0.50 and 0.75, good between 0.75 and 0.90, and excellent above 0.90. Python software (version 3.8.1) was used for statistical analysis. RESULTS Population Fifty-four patients underwent radiographic evaluation. Four patients were excluded because they did not meet the radiographic quality criteria. Therefore, fifty patients were included in the study, consisting of 17 men and 33 women. The mean age was 37 ± 12 years (range 23–59). Bilateral radiographs were obtained in all cases. Radiographic Measurements The mean Overall Linearity of the Forearm (OLF) was 4.4° ± 2.3 (range 0.4–13.6) in neutral pronosupination and 4.0° ± 2.2 (range 0.5–12.1) in complete supination. The mean angle α was 2.8° ± 2.1 (range 0–10) and the mean angle β was 1.7° ± 0.8 (range 0-4.1) in neutral pronosupination. The mean angle α was 2.8° ± 2.1 (range 0-9.8) and the mean angle β was 1.1° ± 0.8 (range 0-3.9) in complete supination. The right/left correlation in the same patient, measured by Pearson's coefficient, was 0.75 in neutral pronosupination and 0.61 in complete supination. The distribution of measurements is illustrated in Fig. 3 . The measurement reliability, calculated by the intraclass correlation coefficient (ICC), was 0.805 [0.66, 0.89] in neutral pronosupination and 0.821 [0.68, 0.9] in complete supination. The inter-observer correlation measured by Pearson's coefficient was 0.60 in neutral pronosupination and 0.61 in complete supination. DISCUSSION We defined the Overall Linearity of the Forearm (OLF) to establish the radiographic normality of a healthy forearm using a simple radiographic assessment that can be routinely utilized. In our series, the mean OLF was 4.4° in neutral pronosupination and 4° in supination, with a low standard deviation, highlighting the consistent parallelism found between the three axes defined in this study within healthy forearm complex. In our study, three axes were defined and analyzed. These three axes were chosen to represent three elements of the forearm complex: the ulna, the radius, and the forearm rotation axis. Numerous methods for measuring the angulation of the radial neck are described in the literature 8 9 10 11 . Some authors measure the radial neck angle as the angle formed between the superior articular surface of the radial head and the radial shaft 12 . However, this measurement does not seem appropriate for assessing the radial neck axis. The tangent line to the superior articular surface of the radial head varies according to the degree of pronosupination. Consequently, the angle described between the superior articular surface of the radial head and the radial shaft inevitably varies according to the degree of pronosupination. Steele and Graham recommend measuring the angulation of the radial neck in multiple axes of pronosupination to assess displacement in the context of fractures 13 . The method of measuring the radial neck axis described here appears reproducible and reliable, independent of the degree of pronosupination and the radiographic incidence. For intra- and inter-observer reproducibility, the middle third of the ulnar shaft was chosen to measure the overall ulnar axis. The middle third forms a straight line regardless of the radiographic incidence, facilitating its measurement. The concept of the forearm rotation axis was developed to consider the "forearm joint" as a whole. This makes it simpler to explain rotational disorders of the forearm complex when abnormalities affect any of its components 14 . The method for measuring the forearm rotation axis varies across studies in the literature 15 . It is generally accepted that the proximal point is formed by the center of the radial head. The distal point varies according to different studies 16 17 18 19 . We chose to consider the center of the sigmoid notch of the radius at the wrist as the distal point of the forearm rotation axis. This point remains unchanged regardless of the degree of pronosupination relative to the center of the radial head and the middle third of the ulnar shaft. Thus, the measurement of the forearm rotation axis does not depend on the degree of pronosupination to be valid. The ICC value was satisfactory for both measurements in neutral pronosupination and complete supination, with values greater than 0.75 for both measurements 20 . A good inter-observer correlation was also observed, with measurements exceeding 0.60. The study group consisted exclusively of patients with no history of trauma or forearm pathology. Therefore, the OLF can be considered a physiological standard in the evaluation of forearm bone disorders. Routine radiographs are not always perfectly executed, making their interpretation challenging. The prospective nature of the study ensured the high quality of the radiographic incidences, in both neutral pronosupination and complete supination. The study group consisted exclusively of patients who underwent perfectly executed radiographs. Currently, the morphological analysis of the forearm complex relies on three-dimensional CT analysis 4 , 6 , 21 . CT analysis allows for precise study of the morphology of the forearm complex and the location and extent of any potential deformity. In cases of morphological disorders (malunion), potential surgical correction may be based on this analysis 15 . More recently, four-dimensional analysis of the forearm complex has been proposed 15 . However, these examinations are not routinely performed during follow-up consultations, for systematic post-operative radiographs, or in emergencies, for example. The use of an isolated radiographic assessment seems outdated and insufficient for analyzing the precise morphology of the forearm complex. However, this simple, rapid radiographic assessment can be useful in a number of situations encountered in everyday practice, such as postoperative analysis of antebrachial frame osteosynthesis, traumatic bone sequelae, or the diagnosis of a malunion whose deformity would not be visible at first glance. Deformities in the frontal and sagittal planes are relatively easy to identify, but rotational deformities are much less so. Malunions of the antebrachial frame are sometimes difficult to identify in comparison with other skeletal regions, not least because of the very particular kinetics of one bone wrapping around the other during pronosupination. Measuring the OLF is an interesting way of assessing the harmony of the antebrachial frame, and can be carried out in routine practice without the need for additional examinations such as a CT scan. Of course, it is not a substitute for further examination if a deformity is suspected, just as malunion in another skeletal region would logically lead to further examination, despite the fact that normal follow-up is based on radiographs. It is a tool to complement the assessment of standard routine radiographs. The measurements of lines AB, R, U, and the angles α and β, when taken independently, do not hold significant value in our opinion. It is the sum of the angles α and β, forming the OLF, that provides a single value reflecting the overall harmony of the forearm complex. The good right/left correlation found in this study suggests that bilateral comparative analysis in the same patient is relevant for evaluating pathological forearm complex, with the patient serving as their own reference. A study focusing on the OLF measurement in pathological forearm complex (malunion, acquired or congenital anomaly) could be of interest. It would allow for the investigation of whether the parallelism of the three axes defined here is compromised in pathological forearm complex. However, the value of this right/left correlation would be lost in cases of bilateral lesions. The study population consisted of patients over 18 years old. The OLF measurement will need to be validated in a pediatric population before it can be extrapolated to children. An adaptation of the measurement should be made in patients whose radial head has not yet ossified on radiographs. To conclude, there is a collinearity between the axis of the radial neck, the axis of the middle third of the ulnar diaphysis, and the forearm rotation axis. This collinearity is consistently observed in a population of 50 healthy volunteer patients and can be analyzed using routine radiographic images. Declarations ETHICS DECLARATIONS: Funding declaration No funding is to be declared for the present study. Ethical approval The study was approved by the Institutional Review Board, and written consent was systematically obtained from all patients. The authors adhered to the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines for the study’s reporting. Informed consent All of the patients provided informed consent to participate in the study. Author Contribution TD : data curation / writing OB : Investigation / methodologyMC : resourcesLL: Conceptualization CL: validation / project administrationBC: project administration All authors have read and agreed to the published version of the manuscript. References LaStayo PC, Lee MJ. The Forearm Complex: Anatomy, Biomechanics and Clinical Considerations. Journal of Hand Therapy . 2006;19(2):137-145. doi:10.1197/j.jht.2006.02.002 Soubeyrand M, Assabah B, Bégin M, Laemmel E, Dos Santos A, Crézé M. Pronation and supination of the hand: Anatomy and biomechanics. Hand Surgery and Rehabilitation . 2017;36(1):2-11. doi:10.1016/j.hansur.2016.09.012 Dumont CE, Thalmann R, Macy JC. The effect of rotational malunion of the radius and the ulna on supination and pronation. J Bone Joint Surg Br . 2002;84(7):1070-1074. doi:10.1302/0301-620x.84b7.12593 Abe S, Murase T, Oka K, Shigi A, Tanaka H, Yoshikawa H. In Vivo Three-Dimensional Analysis of Malunited Forearm Diaphyseal Fractures with Forearm Rotational Restriction. The Journal of Bone and Joint Surgery . 2018;100(17):e113. doi:10.2106/JBJS.17.00934 Blackburn N, Ziv I, Rang M. Correction of the malunited forearm fracture. Clin Orthop Relat Res . 1984;(188):54-57. Miyake J, Oka K, Kataoka T, Moritomo H, Sugamoto K, Murase T. 3-Dimensional Deformity Analysis of Malunited Forearm Diaphyseal Fractures. The Journal of Hand Surgery . 2013;38(7):1356-1365. doi:10.1016/j.jhsa.2013.03.052 Harrison DE, Harrison DD, Cailliet R, Janik TJ, Holland B. Radiographic analysis of lumbar lordosis: centroid, Cobb, TRALL, and Harrison posterior tangent methods. Spine (Phila Pa 1976) . 2001;26(11):E235-242. doi:10.1097/00007632-200106010-00003 Steinberg EL, Golomb D, Salama R, Wientroub S. Radial head and neck fractures in children. J Pediatr Orthop . 1988;8(1):35-40. doi:10.1097/01241398-198801000-00009 Metaizeau JP, Lascombes P, Lemelle JL, Finlayson D, Prevot J. Reduction and fixation of displaced radial neck fractures by closed intramedullary pinning. J Pediatr Orthop . 1993;13(3):355-360. doi:10.1097/01241398-199305000-00015 Rodriguez Merchan EC. Percutaneous reduction of displaced radial neck fractures in children. J Trauma . 1994;37(5):812-814. doi:10.1097/00005373-199411000-00018 Radomisli TE, Rosen AL. Controversies regarding radial neck fractures in children. Clin Orthop Relat Res . 1998;(353):30-39. doi:10.1097/00003086-199808000-00005 Falciglia F, Giordano M, Aulisa AG, Di Lazzaro A, Guzzanti V. Radial neck fractures in children: results when open reduction is indicated. J Pediatr Orthop . 2014;34(8):756-762. doi:10.1097/BPO.0000000000000299 Steele JA, Graham HK. Angulated radial neck fractures in children. A prospective study of percutaneous reduction. J Bone Joint Surg Br . 1992;74(5):760-764. doi:10.1302/0301-620X.74B5.1527130 Graham TJ, Fischer TJ, Hotchkiss RN, Kleinman WB. Disorders of the forearm axis. Hand Clin . 1998;14(2):305-316. Oonk JGM, Dobbe JGG, Strijkers GJ, Van Rijn SK, Streekstra GJ. Kinematic analysis of forearm rotation using four-dimensional computed tomography. J Hand Surg Eur Vol . 2023;48(5):466-475. doi:10.1177/17531934221142520 Hollister AM, Gellman H, Waters RL. The relationship of the interosseous membrane to the axis of rotation of the forearm. Clin Orthop Relat Res . 1994;(298):272-276. Tatebe M, Shinohara T, Okui N, Yamamoto M, Kurimoto S, Hirata H. Tilt of the radius from forearm rotational axis reliably predicts rotational improvement after corrective osteotomy for malunited forearm fractures. Nagoya J Med Sci . 2012;74(1-2):167-171. Tay SC, van Riet R, Kazunari T, Amrami KK, An KN, Berger RA. In-vivo kinematic analysis of forearm rotation using helical axis analysis. Clin Biomech (Bristol) . 2010;25(7):655-659. doi:10.1016/j.clinbiomech.2010.03.010 Oonk JGM, Dobbe JGG, Strijkers GJ, van Rijn SK, Streekstra GJ. Kinematic analysis of forearm rotation using four-dimensional computed tomography. J Hand Surg Eur Vol . 2023;48(5):466-475. doi:10.1177/17531934221142520 Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet . 1986;1(8476):307-310. Oki S, Inaba N, Matsumura N, et al. The relationship between the morphological axis and the kinematic axis of the proximal radius. Surg Radiol Anat . 2019;41(4):423-429. doi:10.1007/s00276-018-2131-0 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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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-6196785","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":432597527,"identity":"1b64be55-1fe2-4ae5-9625-060400663128","order_by":0,"name":"Thomas Daoulas","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABAUlEQVRIie3PsUoDMRjA8e8QziXVNaW9PkPkoC6HPkso3HSDTyApB3GxuN6kr3B9gxzBuARdc9xg3Tvc2CGDwRYRJFdHh/wh5IPkBwlAKPQfw/stYm4JgMzNJ24WcO4T6Adx9yAHiKMvMmZ/JPI4uZ6Uz/XOQvJwd0/Ezr7NyPtyuek14EuPQVOVtysOaaU1aVa8S4mKyovKAJ4K38OKuRkxoMwURIxYR2sV8Qnq4RZ7/1LMW2uBPjnSWPv6TfAQ6VAMtHZEolgciBkgJs+7hON0rdWNTPgiHSvq/qKxl5xWC9VubZY8vpTrj629mp1J2Wx6lXnJod/HR0AoFAqFBvsEZ8xj5bZHKxAAAAAASUVORK5CYII=","orcid":"","institution":"Hôpital Lapeyronie","correspondingAuthor":true,"prefix":"","firstName":"Thomas","middleName":"","lastName":"Daoulas","suffix":""},{"id":432597528,"identity":"5da93cb3-83f4-40ef-b0db-86a6f1917cc6","order_by":1,"name":"Olivier Bozon","email":"","orcid":"","institution":"Hôpital Lapeyronie","correspondingAuthor":false,"prefix":"","firstName":"Olivier","middleName":"","lastName":"Bozon","suffix":""},{"id":432597530,"identity":"90e00200-df21-411d-9e11-56cbc6345f58","order_by":2,"name":"Michel Chammas","email":"","orcid":"","institution":"Hôpital Lapeyronie","correspondingAuthor":false,"prefix":"","firstName":"Michel","middleName":"","lastName":"Chammas","suffix":""},{"id":432597531,"identity":"90490a7c-28ea-445e-ba85-b96a6d3c9dea","order_by":3,"name":"Louis Lancelle","email":"","orcid":"","institution":"Instituts des actuaires","correspondingAuthor":false,"prefix":"","firstName":"Louis","middleName":"","lastName":"Lancelle","suffix":""},{"id":432597534,"identity":"3eae49a6-6d57-46f6-9632-1f03b1fc8e0b","order_by":4,"name":"Cyril Lazerges","email":"","orcid":"","institution":"Hôpital Lapeyronie","correspondingAuthor":false,"prefix":"","firstName":"Cyril","middleName":"","lastName":"Lazerges","suffix":""},{"id":432597535,"identity":"04283c0c-c0d7-4ffb-8dd3-1bd99cfc70f7","order_by":5,"name":"Bertrand Coulet","email":"","orcid":"","institution":"Hôpital Lapeyronie","correspondingAuthor":false,"prefix":"","firstName":"Bertrand","middleName":"","lastName":"Coulet","suffix":""}],"badges":[],"createdAt":"2025-03-10 15:08:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6196785/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6196785/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":79174168,"identity":"e86180c3-6fe7-4f03-ae25-3bab4bec19b9","added_by":"auto","created_at":"2025-03-25 09:50:46","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":358924,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePrimary Axes of the Forearm on Anteroposterior Radiographs of the Forearm in neutral pronosupination. \u003c/strong\u003eAxis AB between the center of the radial head and the center of the sigmoid notch of the radius at the wrist (a). Axis R, corresponding to the bisector of the cortices of the radial neck (b). Axis U, or the center-medullary axis of the middle third of the ulna (c).\u003c/p\u003e","description":"","filename":"Fig1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6196785/v1/68d107b3495b0ca934eb30aa.jpeg"},{"id":79176275,"identity":"f160622e-7937-4305-a7de-b0751301b56b","added_by":"auto","created_at":"2025-03-25 09:58:46","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":140026,"visible":true,"origin":"","legend":"\u003cp\u003eAngles α (a) and β (b) on anteroposterior radiographs of the forearm in neutral pronosupination.\u003c/p\u003e","description":"","filename":"Figure2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6196785/v1/edef4ff20a741c4a014e6a52.jpeg"},{"id":79176280,"identity":"646037f5-6fd9-45e2-acf2-43c34d0565aa","added_by":"auto","created_at":"2025-03-25 09:58:46","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":171089,"visible":true,"origin":"","legend":"\u003cp\u003eRug plot in neutral pronosupination (a) and complete pronosupination (b). The x-axis corresponds to the sum of angles α and β in neutral pronosupination (a) and complete pronosupination (b). The y-axis corresponds to the probability density, i.e. the probability of having a value corresponding to the x-axis for a unit of measurement. The distribution of right/left values is overlapping.\u003c/p\u003e","description":"","filename":"Fig3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6196785/v1/a94046a5c586ab0c9e9dcec0.jpeg"},{"id":86876603,"identity":"73f5f13c-b434-428c-9768-2422c4046854","added_by":"auto","created_at":"2025-07-16 15:31:43","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1094570,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6196785/v1/05e0a7d0-ffd0-4a25-9280-c3d45b342999.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Radiographic Overall Linearity of the Forearm","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eThe forearm complex is a complex anatomical unit, formed by the radius and ulna, encompassing three joints: the proximal radioulnar joint, the middle radioulnar joint, and the distal radioulnar joint. The wrapping of the radius around the ulna in the axial plane, known as pronosupination, allows the hand to be oriented in space \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003ePathological involvement of one or both forearm bones (malunion, growth disorder, congenital anomaly) leads to a modification in the morphology of the forearm complex. This pathological involvement results in a reduction in pronosupination\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe definition of a pathological condition of the forearm complex currently relies on comparing the pathological forearm complex to the contralateral side, which is considered healthy, using radiographic\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e or CT imaging \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Therefore, it always requires comparison with a forearm complex defined as healthy, as it is free from traumatic injury or acquired or congenital morphological disorder. However, no precise radiological description or definition of a healthy forearm complex is found in the literature.\u003c/p\u003e \u003cp\u003eThe primary objective of this study was to demonstrate that there is a consistent collinearity between the axis of the radial neck, the axis of the middle third of the ulnar shaft, and the arc of rotation of the forearm on a radiograph of a healthy forearm complex in a neutral pronosupination and complete supination. The secondary objective was to assess the correlation between both sides.\u003c/p\u003e"},{"header":"METHODS","content":"\u003cp\u003e The study was approved by the Institutional Review Board, and written consent was systematically obtained from all patients. The authors adhered to the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines for the study\u0026rsquo;s reporting.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003ePopulation\u003c/h2\u003e \u003cp\u003eWe conducted a prospective, single-center study. A standardized radiographic protocol was implemented, allowing for the acquisition of bilateral anteroposterior radiographs of the forearm in neutral pronosupination and complete supination in 50 patients with no history of upper limb trauma. The inclusion criteria were healthy adult volunteers who provided written consent before being included in the study. The radiographs were conducted at the expense of the study center.\u003c/p\u003e \u003cp\u003eRadiographs were included after both authors independently reviewed and approved their quality: in the anteroposterior radiograph in complete supination, the radial styloid and biceps tuberosity had to be at 180\u0026deg;, and the trochlea and capitulum had to be seen in full face. In the anteroposterior radiograph in neutral pronosupination, the radial styloid and biceps tuberosity also had to be at 180\u0026deg;, with the trochlea and capitulum superimposed. Patients with any pathology affecting the anatomy of the forearm complex (traumatic history, congenital, or acquired anomalies of the forearm complex) were excluded. The sample size was calculated using the method described by Harrison et al.\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. The method described by Harrison determines sample size by ensuring sufficient statistical power to detect differences in radiographic measurements. It involves calculating the required sample size based on the variability of the measurements (standard deviation) and the desired level of precision or detectable difference. This approach was initially outlined on radiographic analysis methods, where they applied it to lumbar lordosis measurements.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eRadiographic Measurements\u003c/h3\u003e\n\u003cp\u003eWe defined three axes applicable to anteroposterior radiographs of the forearm in neutral pronosupination and complete supination (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The first axis (AB axis), or forearm rotation axis, connected the center of the radial head and the center of the sigmoid notch (defined as the most radial portion of the notch) of the radius at the wrist. The second axis (R axis), or radial neck axis, was defined by the bisector of the radial neck cortices. The last axis (U axis), or ulnar axis, corresponded to the axis of the middle third of the ulnar shaft. The ulna was divided into three equal parts, and the U axis was defined by the center-medullary axis of the middle third. Based on these three axes, two angles were defined: the angle α between the AB axis and the R axis, and the angle β between the AB axis and the U axis (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The vertice of angle α was proximal, that of angle β was distal. These two angles were summed to define the Overall Linearity of the Forearm (OLF).\u003c/p\u003e \u003cp\u003eThese measurements were performed on anteroposterior radiographs of the forearm in neutral pronosupination and complete supination, and compared to the contralateral side. The Digital Imaging System software (GE Healthcare, Piscataway, NJ) was used for the measurements. Two surgeons specialized in upper limb surgery independently performed the measurements. Sex, age, and the side involved were recorded.\u003c/p\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eInter-observer reproducibility and right-left angle comparisons in the same patient were evaluated using Pearson's correlation. Correlation coefficients (r) between 0.60 and 0.80 were considered good, and those of 0.80 or higher were considered excellent. Measurement reliability was calculated using the intraclass correlation coefficient (ICC), expressed with its 95% confidence interval. The ICC was classified as poor below 0.50, moderate between 0.50 and 0.75, good between 0.75 and 0.90, and excellent above 0.90. Python software (version 3.8.1) was used for statistical analysis.\u003c/p\u003e \u003c/div\u003e"},{"header":"RESULTS","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003ePopulation\u003c/h2\u003e \u003cp\u003eFifty-four patients underwent radiographic evaluation. Four patients were excluded because they did not meet the radiographic quality criteria. Therefore, fifty patients were included in the study, consisting of 17 men and 33 women. The mean age was 37\u0026thinsp;\u0026plusmn;\u0026thinsp;12 years (range 23\u0026ndash;59). Bilateral radiographs were obtained in all cases.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eRadiographic Measurements\u003c/h2\u003e \u003cp\u003eThe mean Overall Linearity of the Forearm (OLF) was 4.4\u0026deg; \u0026plusmn; 2.3 (range 0.4\u0026ndash;13.6) in neutral pronosupination and 4.0\u0026deg; \u0026plusmn; 2.2 (range 0.5\u0026ndash;12.1) in complete supination. The mean angle α was 2.8\u0026deg; \u0026plusmn; 2.1 (range 0\u0026ndash;10) and the mean angle β was 1.7\u0026deg; \u0026plusmn; 0.8 (range 0-4.1) in neutral pronosupination. The mean angle α was 2.8\u0026deg; \u0026plusmn; 2.1 (range 0-9.8) and the mean angle β was 1.1\u0026deg; \u0026plusmn; 0.8 (range 0-3.9) in complete supination. The right/left correlation in the same patient, measured by Pearson's coefficient, was 0.75 in neutral pronosupination and 0.61 in complete supination. The distribution of measurements is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The measurement reliability, calculated by the intraclass correlation coefficient (ICC), was 0.805 [0.66, 0.89] in neutral pronosupination and 0.821 [0.68, 0.9] in complete supination. The inter-observer correlation measured by Pearson's coefficient was 0.60 in neutral pronosupination and 0.61 in complete supination.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eWe defined the Overall Linearity of the Forearm (OLF) to establish the radiographic normality of a healthy forearm using a simple radiographic assessment that can be routinely utilized. In our series, the mean OLF was 4.4\u0026deg; in neutral pronosupination and 4\u0026deg; in supination, with a low standard deviation, highlighting the consistent parallelism found between the three axes defined in this study within healthy forearm complex.\u003c/p\u003e \u003cp\u003eIn our study, three axes were defined and analyzed. These three axes were chosen to represent three elements of the forearm complex: the ulna, the radius, and the forearm rotation axis. Numerous methods for measuring the angulation of the radial neck are described in the literature \u003csup\u003e8 9 10 11\u003c/sup\u003e. Some authors measure the radial neck angle as the angle formed between the superior articular surface of the radial head and the radial shaft \u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. However, this measurement does not seem appropriate for assessing the radial neck axis. The tangent line to the superior articular surface of the radial head varies according to the degree of pronosupination. Consequently, the angle described between the superior articular surface of the radial head and the radial shaft inevitably varies according to the degree of pronosupination. Steele and Graham recommend measuring the angulation of the radial neck in multiple axes of pronosupination to assess displacement in the context of fractures \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. The method of measuring the radial neck axis described here appears reproducible and reliable, independent of the degree of pronosupination and the radiographic incidence. For intra- and inter-observer reproducibility, the middle third of the ulnar shaft was chosen to measure the overall ulnar axis. The middle third forms a straight line regardless of the radiographic incidence, facilitating its measurement. The concept of the forearm rotation axis was developed to consider the \"forearm joint\" as a whole. This makes it simpler to explain rotational disorders of the forearm complex when abnormalities affect any of its components\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. The method for measuring the forearm rotation axis varies across studies in the literature \u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. It is generally accepted that the proximal point is formed by the center of the radial head. The distal point varies according to different studies \u003csup\u003e16 17 18 19\u003c/sup\u003e. We chose to consider the center of the sigmoid notch of the radius at the wrist as the distal point of the forearm rotation axis. This point remains unchanged regardless of the degree of pronosupination relative to the center of the radial head and the middle third of the ulnar shaft. Thus, the measurement of the forearm rotation axis does not depend on the degree of pronosupination to be valid.\u003c/p\u003e \u003cp\u003eThe ICC value was satisfactory for both measurements in neutral pronosupination and complete supination, with values greater than 0.75 for both measurements \u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. A good inter-observer correlation was also observed, with measurements exceeding 0.60.\u003c/p\u003e \u003cp\u003eThe study group consisted exclusively of patients with no history of trauma or forearm pathology. Therefore, the OLF can be considered a physiological standard in the evaluation of forearm bone disorders. Routine radiographs are not always perfectly executed, making their interpretation challenging. The prospective nature of the study ensured the high quality of the radiographic incidences, in both neutral pronosupination and complete supination. The study group consisted exclusively of patients who underwent perfectly executed radiographs.\u003c/p\u003e \u003cp\u003eCurrently, the morphological analysis of the forearm complex relies on three-dimensional CT analysis \u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. CT analysis allows for precise study of the morphology of the forearm complex and the location and extent of any potential deformity. In cases of morphological disorders (malunion), potential surgical correction may be based on this analysis \u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. More recently, four-dimensional analysis of the forearm complex has been proposed \u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. However, these examinations are not routinely performed during follow-up consultations, for systematic post-operative radiographs, or in emergencies, for example.\u003c/p\u003e \u003cp\u003eThe use of an isolated radiographic assessment seems outdated and insufficient for analyzing the precise morphology of the forearm complex. However, this simple, rapid radiographic assessment can be useful in a number of situations encountered in everyday practice, such as postoperative analysis of antebrachial frame osteosynthesis, traumatic bone sequelae, or the diagnosis of a malunion whose deformity would not be visible at first glance.\u003c/p\u003e \u003cp\u003eDeformities in the frontal and sagittal planes are relatively easy to identify, but rotational deformities are much less so. Malunions of the antebrachial frame are sometimes difficult to identify in comparison with other skeletal regions, not least because of the very particular kinetics of one bone wrapping around the other during pronosupination. Measuring the OLF is an interesting way of assessing the harmony of the antebrachial frame, and can be carried out in routine practice without the need for additional examinations such as a CT scan.\u003c/p\u003e \u003cp\u003eOf course, it is not a substitute for further examination if a deformity is suspected, just as malunion in another skeletal region would logically lead to further examination, despite the fact that normal follow-up is based on radiographs. It is a tool to complement the assessment of standard routine radiographs.\u003c/p\u003e \u003cp\u003eThe measurements of lines AB, R, U, and the angles α and β, when taken independently, do not hold significant value in our opinion. It is the sum of the angles α and β, forming the OLF, that provides a single value reflecting the overall harmony of the forearm complex.\u003c/p\u003e \u003cp\u003eThe good right/left correlation found in this study suggests that bilateral comparative analysis in the same patient is relevant for evaluating pathological forearm complex, with the patient serving as their own reference. A study focusing on the OLF measurement in pathological forearm complex (malunion, acquired or congenital anomaly) could be of interest. It would allow for the investigation of whether the parallelism of the three axes defined here is compromised in pathological forearm complex. However, the value of this right/left correlation would be lost in cases of bilateral lesions.\u003c/p\u003e \u003cp\u003eThe study population consisted of patients over 18 years old. The OLF measurement will need to be validated in a pediatric population before it can be extrapolated to children. An adaptation of the measurement should be made in patients whose radial head has not yet ossified on radiographs.\u003c/p\u003e \u003cp\u003eTo conclude, there is a collinearity between the axis of the radial neck, the axis of the middle third of the ulnar diaphysis, and the forearm rotation axis. This collinearity is consistently observed in a population of 50 healthy volunteer patients and can be analyzed using routine radiographic images.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003e\u003cu\u003eETHICS DECLARATIONS:\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cu\u003eFunding declaration\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo funding is to be declared for the present study. \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cu\u003eEthical approval\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was approved by the Institutional Review Board, and written consent was systematically obtained from all patients. The authors adhered to the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines for the study\u0026rsquo;s reporting.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cu\u003eInformed consent\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll of the patients provided informed consent to participate in the study.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eTD : data curation / writing OB : Investigation / methodologyMC : resourcesLL: Conceptualization CL: validation / project administrationBC: project administration All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eLaStayo PC, Lee MJ. The Forearm Complex: Anatomy, Biomechanics and Clinical Considerations. \u003cem\u003eJournal of Hand Therapy\u003c/em\u003e. 2006;19(2):137-145. doi:10.1197/j.jht.2006.02.002\u003c/li\u003e\n\u003cli\u003eSoubeyrand M, Assabah B, B\u0026eacute;gin M, Laemmel E, Dos Santos A, Cr\u0026eacute;z\u0026eacute; M. Pronation and supination of the hand: Anatomy and biomechanics. \u003cem\u003eHand Surgery and Rehabilitation\u003c/em\u003e. 2017;36(1):2-11. doi:10.1016/j.hansur.2016.09.012\u003c/li\u003e\n\u003cli\u003eDumont CE, Thalmann R, Macy JC. The effect of rotational malunion of the radius and the ulna on supination and pronation. \u003cem\u003eJ Bone Joint Surg Br\u003c/em\u003e. 2002;84(7):1070-1074. doi:10.1302/0301-620x.84b7.12593\u003c/li\u003e\n\u003cli\u003eAbe S, Murase T, Oka K, Shigi A, Tanaka H, Yoshikawa H. In Vivo Three-Dimensional Analysis of Malunited Forearm Diaphyseal Fractures with Forearm Rotational Restriction. \u003cem\u003eThe Journal of Bone and Joint Surgery\u003c/em\u003e. 2018;100(17):e113. doi:10.2106/JBJS.17.00934\u003c/li\u003e\n\u003cli\u003eBlackburn N, Ziv I, Rang M. Correction of the malunited forearm fracture. \u003cem\u003eClin Orthop Relat Res\u003c/em\u003e. 1984;(188):54-57.\u003c/li\u003e\n\u003cli\u003eMiyake J, Oka K, Kataoka T, Moritomo H, Sugamoto K, Murase T. 3-Dimensional Deformity Analysis of Malunited Forearm Diaphyseal Fractures. \u003cem\u003eThe Journal of Hand Surgery\u003c/em\u003e. 2013;38(7):1356-1365. doi:10.1016/j.jhsa.2013.03.052\u003c/li\u003e\n\u003cli\u003eHarrison DE, Harrison DD, Cailliet R, Janik TJ, Holland B. Radiographic analysis of lumbar lordosis: centroid, Cobb, TRALL, and Harrison posterior tangent methods. \u003cem\u003eSpine (Phila Pa 1976)\u003c/em\u003e. 2001;26(11):E235-242. doi:10.1097/00007632-200106010-00003\u003c/li\u003e\n\u003cli\u003eSteinberg EL, Golomb D, Salama R, Wientroub S. Radial head and neck fractures in children. \u003cem\u003eJ Pediatr Orthop\u003c/em\u003e. 1988;8(1):35-40. doi:10.1097/01241398-198801000-00009\u003c/li\u003e\n\u003cli\u003eMetaizeau JP, Lascombes P, Lemelle JL, Finlayson D, Prevot J. Reduction and fixation of displaced radial neck fractures by closed intramedullary pinning. \u003cem\u003eJ Pediatr Orthop\u003c/em\u003e. 1993;13(3):355-360. doi:10.1097/01241398-199305000-00015\u003c/li\u003e\n\u003cli\u003eRodriguez Merchan EC. Percutaneous reduction of displaced radial neck fractures in children. \u003cem\u003eJ Trauma\u003c/em\u003e. 1994;37(5):812-814. doi:10.1097/00005373-199411000-00018\u003c/li\u003e\n\u003cli\u003eRadomisli TE, Rosen AL. Controversies regarding radial neck fractures in children. \u003cem\u003eClin Orthop Relat Res\u003c/em\u003e. 1998;(353):30-39. doi:10.1097/00003086-199808000-00005\u003c/li\u003e\n\u003cli\u003eFalciglia F, Giordano M, Aulisa AG, Di Lazzaro A, Guzzanti V. Radial neck fractures in children: results when open reduction is indicated. \u003cem\u003eJ Pediatr Orthop\u003c/em\u003e. 2014;34(8):756-762. doi:10.1097/BPO.0000000000000299\u003c/li\u003e\n\u003cli\u003eSteele JA, Graham HK. Angulated radial neck fractures in children. A prospective study of percutaneous reduction. \u003cem\u003eJ Bone Joint Surg Br\u003c/em\u003e. 1992;74(5):760-764. doi:10.1302/0301-620X.74B5.1527130\u003c/li\u003e\n\u003cli\u003eGraham TJ, Fischer TJ, Hotchkiss RN, Kleinman WB. Disorders of the forearm axis. \u003cem\u003eHand Clin\u003c/em\u003e. 1998;14(2):305-316.\u003c/li\u003e\n\u003cli\u003eOonk JGM, Dobbe JGG, Strijkers GJ, Van Rijn SK, Streekstra GJ. Kinematic analysis of forearm rotation using four-dimensional computed tomography. \u003cem\u003eJ Hand Surg Eur Vol\u003c/em\u003e. 2023;48(5):466-475. doi:10.1177/17531934221142520\u003c/li\u003e\n\u003cli\u003eHollister AM, Gellman H, Waters RL. The relationship of the interosseous membrane to the axis of rotation of the forearm. \u003cem\u003eClin Orthop Relat Res\u003c/em\u003e. 1994;(298):272-276.\u003c/li\u003e\n\u003cli\u003eTatebe M, Shinohara T, Okui N, Yamamoto M, Kurimoto S, Hirata H. Tilt of the radius from forearm rotational axis reliably predicts rotational improvement after corrective osteotomy for malunited forearm fractures. \u003cem\u003eNagoya J Med Sci\u003c/em\u003e. 2012;74(1-2):167-171.\u003c/li\u003e\n\u003cli\u003eTay SC, van Riet R, Kazunari T, Amrami KK, An KN, Berger RA. In-vivo kinematic analysis of forearm rotation using helical axis analysis. \u003cem\u003eClin Biomech (Bristol)\u003c/em\u003e. 2010;25(7):655-659. doi:10.1016/j.clinbiomech.2010.03.010\u003c/li\u003e\n\u003cli\u003eOonk JGM, Dobbe JGG, Strijkers GJ, van Rijn SK, Streekstra GJ. Kinematic analysis of forearm rotation using four-dimensional computed tomography. \u003cem\u003eJ Hand Surg Eur Vol\u003c/em\u003e. 2023;48(5):466-475. doi:10.1177/17531934221142520\u003c/li\u003e\n\u003cli\u003eBland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. \u003cem\u003eLancet\u003c/em\u003e. 1986;1(8476):307-310.\u003c/li\u003e\n\u003cli\u003eOki S, Inaba N, Matsumura N, et al. The relationship between the morphological axis and the kinematic axis of the proximal radius. \u003cem\u003eSurg Radiol Anat\u003c/em\u003e. 2019;41(4):423-429. doi:10.1007/s00276-018-2131-0\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":"forearm, malunion, measurements, anatomy","lastPublishedDoi":"10.21203/rs.3.rs-6196785/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6196785/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003ePurpose\u003c/strong\u003e: This study aimed to establish a radiographic standard for a healthy forearm complex by demonstrazting consistent collinearity between three key anatomical axes: the radial neck axis, the ulnar middle third axis, and the forearm rotation axis.\u003c/p\u003e\n\u003cp\u003eThe goal was to provide a simple, routine radiographic measurement method and assess the reliability of this measurement.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e: A prospective, single-center study included 50 patients with no history of upper limb trauma. Standardized bilateral anteroposterior radiographs were obtained in both neutral pronosupination and complete supination. Three anatomical axes were defined: the forearm rotation axis (AB axis), the ulnar axis (U axis), and the radial neck axis (R axis). Two angles (α and β) between these axes were measured to determine the Overall Linearity of the Forearm (OLF). Measurements were conducted using Digital Imaging System software, and both intra- and inter-observer reliability were assessed using intraclass correlation coefficients (ICC) and Pearson’s correlation coefficients.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e: The mean OLF was 4.4° ± 2.3 in neutral pronosupination and 4.0° ± 2.2 in complete supination, with low standard deviations indicating consistent parallelism between the three axes. The mean angles α and β were similar in both pronosupination and supination. Pearson’s correlation for right/left comparison was 0.75 in neutral pronosupination and 0.61 in supination. ICC values for measurement reliability were 0.805 in neutral pronosupination and 0.821 in supination, reflecting good reproducibility.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e: The study established that a consistent collinearity exists among the radial neck axis, ulnar middle third axis, and forearm rotation axis in healthy forearms. This collinearity can be reliably analyzed using routine radiographic images. The Overall Linearity of the Forearm (OLF) provides a useful metric for evaluating forearm morphology and may aid in assessing pathological conditions.\u003c/p\u003e","manuscriptTitle":"Radiographic Overall Linearity of the Forearm","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-03-25 09:50:41","doi":"10.21203/rs.3.rs-6196785/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":"35275c9f-57c2-42ac-8a59-c6de36cf2897","owner":[],"postedDate":"March 25th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-07-16T15:23:33+00:00","versionOfRecord":[],"versionCreatedAt":"2025-03-25 09:50:41","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6196785","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6196785","identity":"rs-6196785","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}