The effect of lower limb rotation on radiographic femoral and tibial joint line obliquity measurements, and the association between the measurements and their changes: a digitally reconstructed radiograph evaluation

The effect of lower limb rotation on radiographic femoral and tibial joint line obliquity measurements, and the association between the measurements and their changes: a digitally reconstructed radiograph evaluation | 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 The effect of lower limb rotation on radiographic femoral and tibial joint line obliquity measurements, and the association between the measurements and their changes: a digitally reconstructed radiograph evaluation Naohiro. Oka, Shigeshi Mori, Yu. Shinyashiki, Nobuhisa. Shokaku, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6628967/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 26 Jul, 2025 Read the published version in Journal of Orthopaedic Surgery and Research → Version 1 posted 9 You are reading this latest preprint version Abstract Background Lower limb rotation at the time of imaging may affect the measurement of joint line angles using plain radiographs, potentially compromising measurement accuracy. Accurate joint line angles are important for orthopaedic surgery planning and limb alignment. This study aimed to investigate the changes in distal femoral and proximal tibial joint line angles in response to limb rotation, and evaluate the correlation between these changes using digitally reconstructed radiographs (DRRs) generated from computed tomography (CT) images. Methods Preoperative CT data from 50 knees scheduled for TKA or unicompartmental knee arthroplasty (UKA) at our institution were analysed using a TKA planning software. The femur and tibia were aligned perpendicularly to their mechanical axes in the coronal and sagittal planes. The surgical epicondylar axis (SEA) and Akagi’s line were used as references for femoral and tibial rotation, respectively, with 0° defined as neutral rotation. Each bone was rotated from 20° external to 20° internal rotation in 5° increments using the software, and DRR images were generated at each position. Lateral Distal Femoral Angle (LDFA), Medial Proximal Tibial Angle (MPTA), and Posterior Tibial Slope (PTS) were measured at each rotational angle. The absolute values and their variations with rotation and correlations between each angle and their respective changes were analysed. Results At 0°, the mean ± SD values were 87.5 ± 2.4°, 83.9 ± 2.6°, and 8.4 ± 3.2° for LDFA, MPTA, and PTS, respectively. The mean changes across 20° external to 20° internal rotation were 0.3° (1.8°–0.6°), 1.1° (1.0°–1.5°), and 6.2° (1.9°–2.4°) for LDFA, MPTA, and PTS, respectively. MPTA was negatively correlated with ΔPTS (r = –0.7). Based on the MPTA values, the patients were categorized into: 84.5° groups. ΔPTS was statistically significant different between the 84.5° groups (4.0 ± 1.9°) (p<0.05 and p<0.001, respectively). Conclusions Limb rotation significantly affects PTS, particularly in cases with greater medial inclination of the tibial plateau. Therefore, caution must be exercised when using plain radiographs for preoperative planning or postoperative evaluation. Knee Radiograph Lower limb rotation Figures Figure 1 Figure 2 Figure 3 Figure 4 Background Total knee arthroplasty (TKA) is a widely performed procedure for end-stage knee osteoarthritis; however, it has been reported that 20–30% of patients remain dissatisfied with the clinical outcomes after surgery[ 1 ].One proposed reason for this dissatisfaction is the insufficient consideration of each patient’s native soft tissue balance. To address this issue, kinematic alignment (KA)-TKA techniques have been introduced in recent years as an alternative approach to conventional mechanical alignment[2.3.4]. KA-TKA aims to restore pre-arthritic coronal alignment and joint line obliquity (JLO), thereby preserving physiological patient-specific joint laxity. The accurate assessment of joint line angles is critical in KA-TKA, and such evaluations are often performed using standard plain radiographs. Lower limb alignment has long been a key factor in preoperative planning, particularly in implant positioning. Among the various alignment parameters, the following joint line inclination angles are considered particularly important: the lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), and posterior tibial slope (PTS). In clinical practice, these measurements are commonly performed using plain radiographs. However, the values may vary depending on the conditions under which the radiographs are obtained, even for the same patient, knee, or observer. A major contributing factor to this variability is lower limb rotation at the time of imaging[5.6]. Several studies have investigated the effects of limb rotation on LDFA, MPTA, and PTS measurements. However, to the best of our knowledge, no previous studies have examined the correlations between the rotational changes in these parameters. In this study, we utilised digitally reconstructed radiographs (DRRs) generated from pre-existing computed tomography (CT) data of the knee joint, allowing us to simulate radiographic images under various rotational conditions without additional radiation exposure. We aimed to evaluate how LDFA, MPTA, and PTS are affected by rotational changes and analyse the relationships among these changes. This study provides novel insights into the reliability and limitations of joint line angle measurements on plain radiographs, which are commonly used in preoperative and postoperative evaluations of TKA. Methods Study Design A retrospective radiographic study was conducted to compare LDFA, MPTA, and PTS measurements. Additionally, correlations between these parameters were analysed. The study protocol was reviewed and approved by the Institutional Review Board of Kindai University Nara Hospital (protocol identification number: 23–087). Informed consent was obtained from all patients for the use of their medical data in this retrospective study. All procedures and investigations were performed in accordance with the ethical standards of the Institutional Research Committee and the 1964 Declaration of Helsinki and its later amendments, or comparable ethical standards. At our institution, CT scans of the entire lower limb are routinely performed for preoperative planning of arthroplasty. For this study, CT data from 50 lower limbs of Japanese patients scheduled for consecutive primary medial TKA or unicompartmental knee arthroplasty (UKA) between April 2017 and May 2021 were used. Measurement of PTS using DRRs and Multiplanar Reconstruction (MPR) Images CT-DICOM data were analysed using a CT-based templating software (3D Template; Kyocera, Osaka, Japan). The femur and tibia were aligned in the coronal and sagittal planes based on their respective mechanical axes. The mechanical axis of the femur was defined as a line connecting the centre of the femoral head to the centre of the knee joint (Fig. 1 a, b). For rotational alignment, the neutral (0°) position was defined as an axis perpendicular to the surgical epicondylar axis (SEA) (Fig. 1 c). Similarly, the mechanical axis of the tibia was defined as a line connecting the centre of the knee to the centre of the ankle joint (Fig. 1 d, e). The rotational reference axis for the tibia was the Akagi’s line, which connects the medial border of the patellar tendon to the posterior cruciate ligament (PCL) attachment site (Fig. 1 f) [ 7 ]. The distal femoral joint line was defined as the line connecting the most distal points of the medial and lateral femoral condyles. The proximal tibial joint line was defined as the line connecting the medial and lateral edges of the tibial plateau. Based on these definitions, three alignment angles were measured: the LDFA, the angle formed between the femoral mechanical axis and the distal femoral joint line on the coronal plane (Fig. 2 a); MPTA, the angle formed between the tibial mechanical axis and the proximal tibial joint line on the coronal plane (Fig. 2 b), and PTS, the angle between the tibial mechanical axis and the slope of the medial tibial plateau in a true sagittal view perpendicular to Akagi’s line (Fig. 2 c). DRRs were generated from the CT data and treated as virtual radiographic images. The LDFA, MPTA, and PTS were measured on these DRRs. Furthermore, the limb was virtually rotated internally and externally in 5° increments around the Akagi’s line, and changes in the three alignment parameters were recorded at each rotation angle (Fig. 2 a–c). Study Cohort We retrospectively analysed the 3D-computed tomography (3D-CT) scans of the lower extremities of 50 patients who underwent knee arthroplasty at our institution. All cases involved moderate knee osteoarthritis classified as Kellgren–Lawrence grade II or III. Patients with a history of high tibial osteotomy on the affected side were excluded. Statistical Analysis All data were normally distributed. Inter- and intra-observer reliability analyses were performed using intraclass correlation coefficients (ICC). Intra-observer reliability was assessed by comparing two measurements taken by observer 1 (NO) four weeks apart. Inter-observer reliability was evaluated between two observers (NS and YS) using the measurements of 20 participants. Intra-class correlation coefficients (ICC; 2-way mixed-effects model, average measures, and absolute agreement) and 95% confidence intervals (CIs) were calculated. An ICC of ≥ 0.80 was considered to indicate excellent reliability. Statistical analyses were performed using the pooled data. Means and standard deviations (SDs) were calculated for all variables. Microsoft Excel 2016 (Microsoft Corp., Redmond, WA, USA) and Bell Curve for Excel (Social Survey Research Information Co., Ltd., Tokyo, Japan) were used. Normality of data distribution was assessed using the Shapiro–Wilk test. Pearson’s correlation analysis was used to evaluate the relationships between DRR-LDFA, DRR-MPTA, and DRR-PTS using their absolute values, and their respective rotational changes (ΔLDFA, ΔMPTA, ΔPTS). Statistical significance was set at P ≤ 0.05. R values were interpreted as follows: <0.10 = trivial, 0.10–0.29 = small, 0.30–0.49 = moderate, 0.50–0.69 = large, 0.70–0.89 = very large, and ≥ 0.90 = nearly perfect. The Mann–Whitney U test was used to compare the mean change in PTS according to MPTA groupings, with a p-value < 0.05 considered statistically significant. Results Study Cohort The mean patient age was 76.6 years (range, 58–98 years). The detailed patient demographics are presented in Table 1. Mechanical Measurements and Changes Associated with Lower Limb Rotation The LDFA, MPTA, and PTS measurements are shown in Table 2. The mean value was 87.5 ± 2.4° for LDFA, 83.9 ± 2.6° for MPTA, and 8.4 ± 3.2° for PTS. Table 3 presents the average changes in these parameters across a rotational range of 20° external to 20° internal rotation (Table 3 − 1: actual values; Table 3 − 2: line graph). The LDFA and MPTA showed minimal changes in response to limb rotation. Both demonstrated a slightly increasing trend from external to internal rotation; however, the changes were < 1° (LDFA: <0.4°, MPTA: <1.1°). In contrast, the PTS exhibited a more marked and consistent increase with internal rotation. Specifically, the PTS value increased from − 3.2° at 20° external rotation to 3.0° at 20° internal rotation. Correlation co-efficient All ICCs were greater than 0.80. The intra-rater reliabilities of the three measurements (LDFA, MPTA, and PTS) on DRR images were 0.93, 0.92, and 0.94, respectively. The inter-rater reliabilities were 0.88, 0.81, and 0.84, respectively. Correlation Between Absolute Values and Rotational Changes of LDFA, MPTA, and PTS The results revealed a strong negative correlation between MPTA and ΔPTS (r = − 0.7) (Fig. 3 ). Differences in PTS Change According to MPTA Values To further investigate the influence of MPTA on PTS changes, knees were divided into three groups based on MPTA values: <82.5°, 82.5–84.5°, and ≥ 84.5° (Fig. 4 ). Significant differences were observed between the groups. In particular, knees with an MPTA < 82.5°, reflecting a markedly varus-inclined tibial plateau, exhibited the largest rotational changes in the PTS. The mean ΔPTS values were 4.0 ± 1.9°; 6.9 ± 1.6°, and 8.6 ± 2.3° for MPTA ≥ 84.5°, MPTA 82.5–84.5°, and MPTA < 82.5°, respectively. Discussion The main findings of this study are as follows: (1) LDFA and MPTA are minimally affected by lower limb rotation; (2) PTS shows considerable variation depending on limb rotation, decreasing with external rotation and increasing with internal rotation; and (3) knees with smaller MPTA values, such as an MPTA < 82.5°, indicating a more varus-inclined tibial plateau, exhibit greater rotational changes in the PTS. These results suggest that planning implant positioning in TKA based solely on joint line inclination measured on plain radiographs, especially the PTS, entails a potential risk of rotational error, highlighting the important implications of our findings in clinical practice. Even within the same knee, joint line measurements may vary depending on the radiographic acquisition conditions. Factors such as the distance between the X-ray source and the knee, angle of beam incidence, and degree of limb rotation can affect the accuracy of the measurements [ 5 ]. Furthermore, knees with advanced osteoarthritic deformities often present flexion and external rotation contractures, making standardised radiographic acquisition more difficult and increasing the potential for measurement error. Several studies have reported that limb rotation affects joint line angles measured on plain radiographs[ 6 ]. However, the extent of these effects varies across studies. Multiple reports have found that LDFA is largely unaffected by limb rotation[7.8], which is consistent with our findings. Likewise, MPTA has been reported to vary by less than 2° within a ± 12° rotation range[ 7 ]. In contrast, other studies have noted significant changes in MPTA beyond 9° of internal rotation or 3° of external rotation[ 8 ]. These discrepancies may stem from the differences in the morphology of the proximal tibial plateau in each study population. In our cohort, the average change in MPTA remained below 1° even with rotations up to ± 20°, indicating high rotational stability. Among the three alignment parameters, the PTS was the most sensitive to limb rotation. Utzschneider et al. reported that the PTS changed by more than 2.5° when lower limb rotation exceeded 40° in cadaveric studies[ 9 ], and other studies have shown an increase of 3° at 40° rotation[ 10 ]. Our study also found that, even at ± 20° rotation, PTS changed by more than 3°, confirming its vulnerability to rotational influence. Although our findings are generally consistent with those of previous reports, our study is unique in that it is the first to explore the interrelationships among rotational changes in the LDFA, MPTA, and PTS. Notably, we found a strong negative correlation between MPTA and ΔPTS, suggesting that knees with smaller MPTA values are more prone to PTS measurement errors due to rotation. KA-TKA has recently gained attention with an emphasis on replicating a patient’s native joint line inclination during surgical planning[ 11 ]. While CT-based measurements are ideal for precise evaluation of joint inclination, they involve concerns related to radiation exposure and cost[12.13]. Plain radiography is the most commonly used imaging method in clinical practice. To obtain standardised plain radiographs, patients are typically instructed to stand barefoot with their patellae facing forward. The gold standard for anteroposterior knee radiographs includes (1) anterior orientation of the patella and (2) a slight overlap between the fibular head and tibia[14.15]. For the lateral views, the ideal criteria include (1) overlapping of the femoral condyles (or posterior condyles), (2) an open patellofemoral joint space, and (3) a slight overlap between the fibular head and tibia[ 16 ]. However, in patients with deformities, achieving the ideal positioning is often challenging[ 17 ]. This difficulty is exacerbated on long-leg radiographs, where ensuring uniform positioning across the entire limb is particularly demanding. Bellemans et al. also noted the limitations of using plain radiographs in their work[ 18 ]. This study had several limitations. First, potential population-dependent factors, such as weight, height, and sex, were not analysed. Second, the sample size was relatively small. Third, CT image acquisition was performed in the prone position, whereas long-leg radiographs are typically taken in the standing, weight-bearing position, which may affect comparability. In addition, knee flexion was not evaluated in this study. The DRR images used in this study differ from conventional radiographs because they lack parallax effects. Finally, image rotation was limited to the mechanical axis of the lower limb. In real clinical scenarios, multiaxial rotation can occur. Future studies that incorporate more realistic, three-dimensional rotational models are warranted. Conclusion This study demonstrated that LDFA and MPTA are minimally affected by lower limb rotation, whereas the PTS is significantly influenced, particularly in cases with smaller MPTA values. Therefore, special attention should be paid to evaluating PTS on plain radiographs during preoperative planning, such as for TKA, as rotational positioning errors may lead to inaccurate PTS measurements. To ensure accurate preoperative assessment, optimisation of radiographic imaging protocols and use of supplemental imaging modalities are recommended. Abbreviations KA Kinematic Alignment TKA Total Knee Arthroplasty UKA Unicompartmental Knee Arthroplasty LDFA Lateral Distal Femoral Angle MPTA Medial Proximal Tibial Angle PTS Posterior Tibial Slope DRR Digitally Reconstructed Radiograph ER External rotation IR Internal rotation MRI Magnetic Resonance Imaging CT Computed Tomography JLO Joint Line Obliquity MPR Multiplanar Reconstruction SEA Surgical Epicondylar Axis PCL posterior cruciate ligament Declarations Ethics approval and consent to participate: The study protocol was reviewed and approved by the Institutional Review Board of Kindai University Nara Hospital (protocol identification number: 23–087). Consent for publication: Informed consent was obtained from all patients for the use of their medical data in this retrospective study. Availability of data and materials The datasets generated and/or analyzed during the current study are not publicly available due to the inclusion of sensitive patient information and privacy concerns, but are available from the corresponding author upon reasonable request. Competing interests The authors declare that they have no competing interests. Funding None. Authors' contributions NO, SM, AM, and KY participated in data collection, analysis and manuscript writing. YU, NS and KH participated in the study design. NO, SM, YU, and SN confirm the authenticity of all the raw data. All authors have read and approved the final manuscript. Acknowledgements Special thanks to the orthopedic surgery team, who assisted in the treatment of the patient. References Parvizi J, Nunley RM, Berend KR, Lombardi AV Jr., Ruh EL, Clohisy JC, et al. High level of residual symptoms in young patients after total knee arthroplasty. Clin Orthop Relat Res. 2014;472:133–7. Blakeney W, Clément J, Desmeules F, Hagemeister N, Rivière C, Vendittoli PA. Kinematic alignment in total knee arthroplasty better reproduces normal gait than mechanical alignment. Knee Surg Sports Traumatol Arthrosc. 2019;27:1410–7. Liu B, Feng C, Tu C. Kinematic alignment versus mechanical alignment in primary total knee arthroplasty: an updated meta-analysis of randomized controlled trials. J Ortho Surg Res. 2022;17:201. Sarzaeem MM, Movahedinia M, Mirahmadi A, Abolghasemian M, Tavakoli M, Amouzadeh Omrani F. Kinematic alignment technique outperforms mechanical alignment in simultaneous bilateral total knee arthroplasty: a randomized controlled trial. J Arthroplasty. 2024;39:2234–40. Oswald MH, Jakob RP, Schneider E, Hoogewoud HM. Radiological analysis of normal axial alignment of femur and tibia in view of total knee arthroplasty. J Arthroplasty. 1993;8:419–26. Sanfridsson J, Arnbjörnsson A, Fridén T, Ryd L, Svahn G, Jonsson K. Femorotibial rotation and the Q-angle related to the dislocating patella. Acta Radiol. 2001;42:218–24. Chung J, Lee J, Han HS, Lee MC, Ro DH. The effect of position on radiographic angle measurements of the lower extremities. BioMed Res Int. 2022;2022:1057227. Jamali AA, Meehan JP, Moroski NM, Anderson MJ, Lamba R, Parise C. Do small changes in rotation affect measurements of lower extremity limb alignment? JOrtho Surg Res. 2017;12:77. Utzschneider S, Goettinger M, Weber P, Horng A, Glaser C, Jansson V, et al. Development and validation of a new method for the radiologic measurement of the tibial slope. Knee Surg Sports Traumatol Arthosc. 2011;19:1643–8. Zhang Y, Chen Y, Qiang M, Zhang K, Li H, Jiang Y, et al. Comparison between three-dimensional CT and conventional radiography in proximal tibia morphology. Medicine. 2018;97:e11632. MacDessi SJ, Griffiths-Jones W, Harris IA, Bellemans J, Chen DB. Coronal Plane Alignment of the Knee (CPAK) classification. Bone Joint J. 2021;103–B(2):329–37. Brenner DJ, Hall EJ. Computed tomography–an increasing source of radiation exposure. N Engl J Med. 2007;357:2277–84. Abdelfadeel W, Houston N, Star A, Saxena A, Hozack WJ. CT planning studies for robotic total knee arthroplasty. Bone Joint J 2020;102-B(6_Supple_A):79–84. de Rocha JL, Pedrinha ISM, Pavão DM, Albuquerque RPE, Sousa EB, Mandarino M, et al. Stress radiography for multiligament knee injuries: a standardized, step-by-step technique. Arthrosc Tech. 2020;9:e1885–92. Vince AS, Singhania AK, Glasgow MM. What knee X-rays do we need? A survey of orthopaedic surgeons in the United Kingdom. Knee. 2000;7:101–4. Wang S, Xiao Z, Lu Y, Zhang Z, Lv F. Radiographic optimization of the lateral position of the knee joint aided by CT images and the maximum intensity projection technique. J Ortho Surg Res. 2021;16:581. Moreland JR, Bassett LW, Hanker GJ. Radiographic analysis of the axial alignment of the lower extremity. J f Bone Joint Surg Am. 1987;69:745–9. Bellemans J, Colyn W, Vandenneucker H, Victor J. The Chitranjan Ranawat award: is neutral mechanical alignment normal for all patients? The concept of constitutional varus. Clin Ortho Relat Res. 2012;470:45–53. Tables Tables 1 to 3 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Table.1.jpg Table 1 Demographic characteristics of the 50 patients included in the study. BMI, body mass index Table.2.jpg Table 2. Baseline measurements of the LDFA, MPTA, and PTS during neutral rotation. LDFA, lateral distal femoral angle; MPTA, medial proximal tibial angle; PTS, posterior tibial slope Table.31.jpg Table 3-1. Effects of limb rotation on LDFA, MPTA, and PTS. Mean and standard deviation of each parameter in 5° increments from 20° external rotation to 20° internal rotation. ER, external rotation; IR, internal rotation; LDFA, lateral distal femoral angle; MPTA, medial proximal tibial angle; PTS, posterior tibial slope Table.32.jpg Table 3-2. Graphical representation of rotational changes in alignment angles. Line graph showing trends in ΔLDFA, ΔMPTA, and ΔPTS across various degrees of lower limb rotation. LDFA, lateral distal femoral angle; MPTA, medial proximal tibial angle; PTS, posterior tibial slope Cite Share Download PDF Status: Published Journal Publication published 26 Jul, 2025 Read the published version in Journal of Orthopaedic Surgery and Research → Version 1 posted Editorial decision: Revision requested 09 Jun, 2025 Reviews received at journal 09 Jun, 2025 Reviews received at journal 08 Jun, 2025 Reviewers agreed at journal 19 May, 2025 Reviewers agreed at journal 18 May, 2025 Reviewers invited by journal 13 May, 2025 Editor assigned by journal 12 May, 2025 Submission checks completed at journal 11 May, 2025 First submitted to journal 09 May, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6628967","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":457168002,"identity":"fb4c3fea-0e47-4ffb-adda-f877e28f3af8","order_by":0,"name":"Naohiro. 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Shinyashiki","email":"","orcid":"","institution":"Kindai University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yu.","middleName":"","lastName":"Shinyashiki","suffix":""},{"id":457168005,"identity":"486ebccc-a647-4bd0-82c3-a0bed0551911","order_by":3,"name":"Nobuhisa. Shokaku","email":"","orcid":"","institution":"Kindai University Nara Hospital","correspondingAuthor":false,"prefix":"","firstName":"Nobuhisa.","middleName":"","lastName":"Shokaku","suffix":""},{"id":457168006,"identity":"04e1f8d2-ff4f-40da-a1b8-290522b49314","order_by":4,"name":"Kenji. Yamasaki","email":"","orcid":"","institution":"Kindai University Nara Hospital","correspondingAuthor":false,"prefix":"","firstName":"Kenji.","middleName":"","lastName":"Yamasaki","suffix":""},{"id":457168007,"identity":"8bd9571e-fc3c-48cd-b129-2be72578637e","order_by":5,"name":"Akihiro Moritake","email":"","orcid":"","institution":"Kindai University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Akihiro","middleName":"","lastName":"Moritake","suffix":""},{"id":457168008,"identity":"3ecb60d8-789d-4d34-9e2a-22d73a435cca","order_by":6,"name":"Kotaro Yamagishi","email":"","orcid":"","institution":"Kindai University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Kotaro","middleName":"","lastName":"Yamagishi","suffix":""},{"id":457168009,"identity":"89ccded3-ce6f-498a-8cfa-c8edafb6c665","order_by":7,"name":"Kazuhiko Hashikoto","email":"","orcid":"","institution":"Kindai University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Kazuhiko","middleName":"","lastName":"Hashikoto","suffix":""},{"id":457168010,"identity":"b817baa9-5ccf-48ae-93aa-04ad7592de8d","order_by":8,"name":"Koji Goto","email":"","orcid":"","institution":"Kindai University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Koji","middleName":"","lastName":"Goto","suffix":""},{"id":457168014,"identity":"7f816f4d-58c0-48f3-825a-110250384b3e","order_by":9,"name":"Daisuke Togawa","email":"","orcid":"","institution":"Kindai University Nara Hospital","correspondingAuthor":false,"prefix":"","firstName":"Daisuke","middleName":"","lastName":"Togawa","suffix":""}],"badges":[],"createdAt":"2025-05-09 13:08:48","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6628967/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6628967/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s13018-025-06106-2","type":"published","date":"2025-07-26T15:58:28+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":83017656,"identity":"429139e9-8f37-40b7-9ed6-3bc28bd7b3e8","added_by":"auto","created_at":"2025-05-19 06:43:19","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":89324,"visible":true,"origin":"","legend":"\u003cp\u003eDefinition of mechanical and rotational axes in the femur and tibia. \u003cbr\u003e\n(a, b) Mechanical axis of the femur from the femoral head centre to the knee centre. \u003cbr\u003e\n(c) Rotational axis of the femur perpendicular to the Surgical Epicondylar Axis (SEA). \u003cbr\u003e\n(d, e) Mechanical axis of the tibia from the knee centre to the ankle centre. \u003cbr\u003e\n(f) Rotational axis of the tibia: Akagi’s line, defined as the line connecting the medial edge of the patellar tendon and posterior cruciate ligament (PCL) insertions.\u003c/p\u003e\n\u003cp\u003eER, external rotation; IR, internal rotation\u003c/p\u003e","description":"","filename":"Fig.1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6628967/v1/0186c1b1af72eefa3c9a2f3c.jpg"},{"id":83019248,"identity":"a317fafe-0303-42d9-9c60-a289a3eb9652","added_by":"auto","created_at":"2025-05-19 07:07:19","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":2150194,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea.\u003c/strong\u003e\u003cbr\u003e\n\u0026nbsp;Measurement of the lateral distal femoral angle (LDFA).\u003cbr\u003e\n\u0026nbsp;Reconstruction of digitally reconstructed radiographs (DRRs) from 3D computed tomography (CT) data of the femur and measurement of the mechanical lateral distal femoral angle under different rotation conditions.\u003c/p\u003e\n\u003cp\u003eER, external rotation; IR, internal rotation\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eb.\u003c/strong\u003e\u003cbr\u003e\n\u0026nbsp;Measurement of the medial proximal tibial angle (MPTA).\u003cbr\u003e\n\u0026nbsp;Digitally reconstructed radiographs (DRRs) from tibial computed tomography (CT) data and measurement of the mechanical medial proximal tibial angle at various rotational positions.ER, external rotation; IR, internal rotation\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ec.\u003c/strong\u003e\u003cbr\u003e\n\u0026nbsp;Measurement of the posterior tibial slope (PTS).\u003cbr\u003e\n\u0026nbsp;A digitally reconstructed radiograph (DRR)-based sagittal view aligned perpendicularly to Akagi’s line was used to assess the posterior tibial slope under internal and external rotation.\u003c/p\u003e\n\u003cp\u003eER, external rotation; IR, internal rotation\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6628967/v1/21b63fb80f79d5656dfa04c8.jpg"},{"id":83017898,"identity":"67551483-6b42-49c3-8312-825486aac3cd","added_by":"auto","created_at":"2025-05-19 06:51:19","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":98987,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation between absolute values and rotational changes in alignment parameters. \u003cbr\u003e\nScatter plots showing correlations between measured lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), and posterior tibial slope (PTS) values and their respective changes (ΔLDFA, ΔMPTA, ΔPTS). Only ΔPTS and MPTA showed a strong negative correlation (r = –0.7).\u003c/p\u003e","description":"","filename":"Fig.3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6628967/v1/ef5ca4a875c074d9c6bad67b.jpg"},{"id":83017654,"identity":"288dac52-99ef-4ac0-b31e-7e6ff895479f","added_by":"auto","created_at":"2025-05-19 06:43:19","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":64406,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of posterior tibial slope change (ΔPTS) across the medial proximal tibial angle (MPTA) groups. \u003cbr\u003e\n \u0026nbsp;The change in PTS due to limb rotation was significantly larger in knees with MPTA \u0026lt;82.5°, indicating greater susceptibility to rotational error. \u003cbr\u003e\n*P \u0026lt; 0.05, **P \u0026lt; 0.01, ***P \u0026lt; 0.001\u003c/p\u003e","description":"","filename":"Fig.4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6628967/v1/0309e62b0b324e6c3ee17737.jpg"},{"id":87756947,"identity":"328bdd3b-8280-418e-8f34-feba54f12374","added_by":"auto","created_at":"2025-07-28 16:10:23","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3116164,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6628967/v1/e37c5782-784d-443f-859f-2e0ada9d55e0.pdf"},{"id":83019246,"identity":"234a88b5-80b3-43fb-a1cc-de8394992e3a","added_by":"auto","created_at":"2025-05-19 07:07:19","extension":"jpg","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":86963,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDemographic characteristics of the 50 patients included in the study.\u003c/p\u003e\n\u003cp\u003eBMI, body mass index\u003c/p\u003e","description":"","filename":"Table.1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6628967/v1/ce4642cd228f45d5f807dbf3.jpg"},{"id":83018692,"identity":"aedd2391-45e9-40c5-9ce1-deb0cf9b9eea","added_by":"auto","created_at":"2025-05-19 06:59:19","extension":"jpg","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":60611,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eTable 2.\u003c/strong\u003e\u003cbr\u003e\nBaseline measurements of the LDFA, MPTA, and PTS during neutral rotation.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eLDFA, lateral distal femoral angle; MPTA, medial proximal tibial angle; PTS, posterior tibial slope\u003c/p\u003e","description":"","filename":"Table.2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6628967/v1/45c9330a9e94aca57e030de0.jpg"},{"id":83018690,"identity":"bce78941-cf37-4bba-89cc-f14f73308a75","added_by":"auto","created_at":"2025-05-19 06:59:19","extension":"jpg","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":80780,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eTable 3-1.\u003c/strong\u003e\u003cbr\u003e\nEffects of limb rotation on LDFA, MPTA, and PTS. \u003cbr\u003e\nMean and standard deviation of each parameter in 5° increments from 20° external rotation to 20° internal rotation.\u003c/p\u003e\n\u003cp\u003eER, external rotation; IR, internal rotation; LDFA, lateral distal femoral angle; MPTA, medial proximal tibial angle; PTS, posterior tibial slope\u003c/p\u003e","description":"","filename":"Table.31.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6628967/v1/41ec94dc715b3a09fb5fcf0e.jpg"},{"id":83018695,"identity":"04d245e5-38f9-40e9-b370-e965a8e968dc","added_by":"auto","created_at":"2025-05-19 06:59:19","extension":"jpg","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":57240,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eTable 3-2.\u003c/strong\u003e\u003cbr\u003e\nGraphical representation of rotational changes in alignment angles. \u003cbr\u003e\nLine graph showing trends in ΔLDFA, ΔMPTA, and ΔPTS across various degrees of lower limb rotation.\u003c/p\u003e\n\u003cp\u003eLDFA, lateral distal femoral angle; MPTA, medial proximal tibial angle; PTS, posterior tibial slope\u003c/p\u003e","description":"","filename":"Table.32.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6628967/v1/095cd9677908969eec84156b.jpg"}],"financialInterests":"No competing interests reported.","formattedTitle":"The effect of lower limb rotation on radiographic femoral and tibial joint line obliquity measurements, and the association between the measurements and their changes: a digitally reconstructed radiograph evaluation","fulltext":[{"header":"Background","content":"\u003cp\u003eTotal knee arthroplasty (TKA) is a widely performed procedure for end-stage knee osteoarthritis; however, it has been reported that 20\u0026ndash;30% of patients remain dissatisfied with the clinical outcomes after surgery[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].One proposed reason for this dissatisfaction is the insufficient consideration of each patient\u0026rsquo;s native soft tissue balance.\u003c/p\u003e \u003cp\u003eTo address this issue, kinematic alignment (KA)-TKA techniques have been introduced in recent years as an alternative approach to conventional mechanical alignment[2.3.4]. KA-TKA aims to restore pre-arthritic coronal alignment and joint line obliquity (JLO), thereby preserving physiological patient-specific joint laxity.\u003c/p\u003e \u003cp\u003eThe accurate assessment of joint line angles is critical in KA-TKA, and such evaluations are often performed using standard plain radiographs.\u003c/p\u003e \u003cp\u003eLower limb alignment has long been a key factor in preoperative planning, particularly in implant positioning. Among the various alignment parameters, the following joint line inclination angles are considered particularly important: the lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), and posterior tibial slope (PTS).\u003c/p\u003e \u003cp\u003eIn clinical practice, these measurements are commonly performed using plain radiographs. However, the values may vary depending on the conditions under which the radiographs are obtained, even for the same patient, knee, or observer. A major contributing factor to this variability is lower limb rotation at the time of imaging[5.6].\u003c/p\u003e \u003cp\u003eSeveral studies have investigated the effects of limb rotation on LDFA, MPTA, and PTS measurements. However, to the best of our knowledge, no previous studies have examined the correlations between the rotational changes in these parameters.\u003c/p\u003e \u003cp\u003eIn this study, we utilised digitally reconstructed radiographs (DRRs) generated from pre-existing computed tomography (CT) data of the knee joint, allowing us to simulate radiographic images under various rotational conditions without additional radiation exposure. We aimed to evaluate how LDFA, MPTA, and PTS are affected by rotational changes and analyse the relationships among these changes.\u003c/p\u003e \u003cp\u003eThis study provides novel insights into the reliability and limitations of joint line angle measurements on plain radiographs, which are commonly used in preoperative and postoperative evaluations of TKA.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy Design\u003c/h2\u003e \u003cp\u003eA retrospective radiographic study was conducted to compare LDFA, MPTA, and PTS measurements. Additionally, correlations between these parameters were analysed.\u003c/p\u003e \u003cp\u003e The study protocol was reviewed and approved by the Institutional Review Board of Kindai University Nara Hospital (protocol identification number: 23\u0026ndash;087). Informed consent was obtained from all patients for the use of their medical data in this retrospective study.\u003c/p\u003e \u003cp\u003e All procedures and investigations were performed in accordance with the ethical standards of the Institutional Research Committee and the 1964 Declaration of Helsinki and its later amendments, or comparable ethical standards.\u003c/p\u003e \u003cp\u003eAt our institution, CT scans of the entire lower limb are routinely performed for preoperative planning of arthroplasty. For this study, CT data from 50 lower limbs of Japanese patients scheduled for consecutive primary medial TKA or unicompartmental knee arthroplasty (UKA) between April 2017 and May 2021 were used.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eMeasurement of PTS using DRRs and Multiplanar Reconstruction (MPR) Images\u003c/h3\u003e\n\u003cp\u003eCT-DICOM data were analysed using a CT-based templating software (3D Template; Kyocera, Osaka, Japan). The femur and tibia were aligned in the coronal and sagittal planes based on their respective mechanical axes.\u003c/p\u003e \u003cp\u003eThe mechanical axis of the femur was defined as a line connecting the centre of the femoral head to the centre of the knee joint (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea, b). For rotational alignment, the neutral (0\u0026deg;) position was defined as an axis perpendicular to the surgical epicondylar axis (SEA) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSimilarly, the mechanical axis of the tibia was defined as a line connecting the centre of the knee to the centre of the ankle joint (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed, e). The rotational reference axis for the tibia was the Akagi\u0026rsquo;s line, which connects the medial border of the patellar tendon to the posterior cruciate ligament (PCL) attachment site (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ef) [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe distal femoral joint line was defined as the line connecting the most distal points of the medial and lateral femoral condyles. The proximal tibial joint line was defined as the line connecting the medial and lateral edges of the tibial plateau.\u003c/p\u003e \u003cp\u003eBased on these definitions, three alignment angles were measured: the LDFA, the angle formed between the femoral mechanical axis and the distal femoral joint line on the coronal plane (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e2\u003c/span\u003ea); MPTA, the angle formed between the tibial mechanical axis and the proximal tibial joint line on the coronal plane (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e2\u003c/span\u003eb), and PTS, the angle between the tibial mechanical axis and the slope of the medial tibial plateau in a true sagittal view perpendicular to Akagi\u0026rsquo;s line (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e2\u003c/span\u003ec).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eDRRs were generated from the CT data and treated as virtual radiographic images. The LDFA, MPTA, and PTS were measured on these DRRs. Furthermore, the limb was virtually rotated internally and externally in 5\u0026deg; increments around the Akagi\u0026rsquo;s line, and changes in the three alignment parameters were recorded at each rotation angle (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e2\u003c/span\u003ea\u0026ndash;c).\u003c/p\u003e\n\u003ch3\u003eStudy Cohort\u003c/h3\u003e\n\u003cp\u003eWe retrospectively analysed the 3D-computed tomography (3D-CT) scans of the lower extremities of 50 patients who underwent knee arthroplasty at our institution.\u003c/p\u003e \u003cp\u003eAll cases involved moderate knee osteoarthritis classified as Kellgren\u0026ndash;Lawrence grade II or III. Patients with a history of high tibial osteotomy on the affected side were excluded.\u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eAll data were normally distributed. Inter- and intra-observer reliability analyses were performed using intraclass correlation coefficients (ICC). Intra-observer reliability was assessed by comparing two measurements taken by observer 1 (NO) four weeks apart. Inter-observer reliability was evaluated between two observers (NS and YS) using the measurements of 20 participants.\u003c/p\u003e \u003cp\u003eIntra-class correlation coefficients (ICC; 2-way mixed-effects model, average measures, and absolute agreement) and 95% confidence intervals (CIs) were calculated. An ICC of \u0026ge;\u0026thinsp;0.80 was considered to indicate excellent reliability.\u003c/p\u003e \u003cp\u003eStatistical analyses were performed using the pooled data. Means and standard deviations (SDs) were calculated for all variables. Microsoft Excel 2016 (Microsoft Corp., Redmond, WA, USA) and Bell Curve for Excel (Social Survey Research Information Co., Ltd., Tokyo, Japan) were used. Normality of data distribution was assessed using the Shapiro\u0026ndash;Wilk test.\u003c/p\u003e \u003cp\u003ePearson\u0026rsquo;s correlation analysis was used to evaluate the relationships between DRR-LDFA, DRR-MPTA, and DRR-PTS using their absolute values, and their respective rotational changes (ΔLDFA, ΔMPTA, ΔPTS). Statistical significance was set at P\u0026thinsp;\u0026le;\u0026thinsp;0.05. R values were interpreted as follows: \u0026lt;0.10\u0026thinsp;=\u0026thinsp;trivial, 0.10\u0026ndash;0.29\u0026thinsp;=\u0026thinsp;small, 0.30\u0026ndash;0.49\u0026thinsp;=\u0026thinsp;moderate, 0.50\u0026ndash;0.69\u0026thinsp;=\u0026thinsp;large, 0.70\u0026ndash;0.89\u0026thinsp;=\u0026thinsp;very large, and \u0026ge;\u0026thinsp;0.90\u0026thinsp;=\u0026thinsp;nearly perfect.\u003c/p\u003e \u003cp\u003eThe Mann\u0026ndash;Whitney U test was used to compare the mean change in PTS according to MPTA groupings, with a p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 considered statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eStudy Cohort\u003c/h2\u003e \u003cp\u003eThe mean patient age was 76.6 years (range, 58\u0026ndash;98 years). The detailed patient demographics are presented in Table\u0026nbsp;1.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eMechanical Measurements and Changes Associated with Lower Limb Rotation\u003c/h3\u003e\n\u003cp\u003eThe LDFA, MPTA, and PTS measurements are shown in Table\u0026nbsp;2. The mean value was 87.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2.4\u0026deg; for LDFA, 83.9\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6\u0026deg; for MPTA, and 8.4\u0026thinsp;\u0026plusmn;\u0026thinsp;3.2\u0026deg; for PTS.\u003c/p\u003e \u003cp\u003eTable\u0026nbsp;3 presents the average changes in these parameters across a rotational range of 20\u0026deg; external to 20\u0026deg; internal rotation (Table\u0026nbsp;3\u0026thinsp;\u0026minus;\u0026thinsp;1: actual values; Table\u0026nbsp;3\u0026thinsp;\u0026minus;\u0026thinsp;2: line graph).\u003c/p\u003e \u003cp\u003eThe LDFA and MPTA showed minimal changes in response to limb rotation. Both demonstrated a slightly increasing trend from external to internal rotation; however, the changes were \u0026lt;\u0026thinsp;1\u0026deg; (LDFA: \u0026lt;0.4\u0026deg;, MPTA: \u0026lt;1.1\u0026deg;).\u003c/p\u003e \u003cp\u003eIn contrast, the PTS exhibited a more marked and consistent increase with internal rotation. Specifically, the PTS value increased from \u0026minus;\u0026thinsp;3.2\u0026deg; at 20\u0026deg; external rotation to 3.0\u0026deg; at 20\u0026deg; internal rotation.\u003c/p\u003e\n\u003ch3\u003eCorrelation co-efficient\u003c/h3\u003e\n\u003cp\u003eAll ICCs were greater than 0.80. The intra-rater reliabilities of the three measurements (LDFA, MPTA, and PTS) on DRR images were 0.93, 0.92, and 0.94, respectively. The inter-rater reliabilities were 0.88, 0.81, and 0.84, respectively.\u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eCorrelation Between Absolute Values and Rotational Changes of LDFA, MPTA, and PTS\u003c/h2\u003e \u003cp\u003eThe results revealed a strong negative correlation between MPTA and ΔPTS (r = \u0026minus;\u0026thinsp;0.7) (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eDifferences in PTS Change According to MPTA Values\u003c/h2\u003e \u003cp\u003eTo further investigate the influence of MPTA on PTS changes, knees were divided into three groups based on MPTA values: \u0026lt;82.5\u0026deg;, 82.5\u0026ndash;84.5\u0026deg;, and \u0026ge;\u0026thinsp;84.5\u0026deg; (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Significant differences were observed between the groups. In particular, knees with an MPTA\u0026thinsp;\u0026lt;\u0026thinsp;82.5\u0026deg;, reflecting a markedly varus-inclined tibial plateau, exhibited the largest rotational changes in the PTS.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe mean ΔPTS values were 4.0\u0026thinsp;\u0026plusmn;\u0026thinsp;1.9\u0026deg;; 6.9\u0026thinsp;\u0026plusmn;\u0026thinsp;1.6\u0026deg;, and 8.6\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3\u0026deg; for MPTA\u0026thinsp;\u0026ge;\u0026thinsp;84.5\u0026deg;, MPTA 82.5\u0026ndash;84.5\u0026deg;, and MPTA\u0026thinsp;\u0026lt;\u0026thinsp;82.5\u0026deg;, respectively.\u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe main findings of this study are as follows: (1) LDFA and MPTA are minimally affected by lower limb rotation; (2) PTS shows considerable variation depending on limb rotation, decreasing with external rotation and increasing with internal rotation; and (3) knees with smaller MPTA values, such as an MPTA\u0026thinsp;\u0026lt;\u0026thinsp;82.5\u0026deg;, indicating a more varus-inclined tibial plateau, exhibit greater rotational changes in the PTS. These results suggest that planning implant positioning in TKA based solely on joint line inclination measured on plain radiographs, especially the PTS, entails a potential risk of rotational error, highlighting the important implications of our findings in clinical practice.\u003c/p\u003e \u003cp\u003eEven within the same knee, joint line measurements may vary depending on the radiographic acquisition conditions. Factors such as the distance between the X-ray source and the knee, angle of beam incidence, and degree of limb rotation can affect the accuracy of the measurements [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Furthermore, knees with advanced osteoarthritic deformities often present flexion and external rotation contractures, making standardised radiographic acquisition more difficult and increasing the potential for measurement error.\u003c/p\u003e \u003cp\u003eSeveral studies have reported that limb rotation affects joint line angles measured on plain radiographs[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. However, the extent of these effects varies across studies. Multiple reports have found that LDFA is largely unaffected by limb rotation[7.8], which is consistent with our findings. Likewise, MPTA has been reported to vary by less than 2\u0026deg; within a\u0026thinsp;\u0026plusmn;\u0026thinsp;12\u0026deg; rotation range[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. In contrast, other studies have noted significant changes in MPTA beyond 9\u0026deg; of internal rotation or 3\u0026deg; of external rotation[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThese discrepancies may stem from the differences in the morphology of the proximal tibial plateau in each study population. In our cohort, the average change in MPTA remained below 1\u0026deg; even with rotations up to \u0026plusmn;\u0026thinsp;20\u0026deg;, indicating high rotational stability.\u003c/p\u003e \u003cp\u003eAmong the three alignment parameters, the PTS was the most sensitive to limb rotation. Utzschneider et al. reported that the PTS changed by more than 2.5\u0026deg; when lower limb rotation exceeded 40\u0026deg; in cadaveric studies[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], and other studies have shown an increase of 3\u0026deg; at 40\u0026deg; rotation[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Our study also found that, even at \u0026plusmn;\u0026thinsp;20\u0026deg; rotation, PTS changed by more than 3\u0026deg;, confirming its vulnerability to rotational influence.\u003c/p\u003e \u003cp\u003eAlthough our findings are generally consistent with those of previous reports, our study is unique in that it is the first to explore the interrelationships among rotational changes in the LDFA, MPTA, and PTS. Notably, we found a strong negative correlation between MPTA and ΔPTS, suggesting that knees with smaller MPTA values are more prone to PTS measurement errors due to rotation.\u003c/p\u003e \u003cp\u003eKA-TKA has recently gained attention with an emphasis on replicating a patient\u0026rsquo;s native joint line inclination during surgical planning[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. While CT-based measurements are ideal for precise evaluation of joint inclination, they involve concerns related to radiation exposure and cost[12.13]. Plain radiography is the most commonly used imaging method in clinical practice. To obtain standardised plain radiographs, patients are typically instructed to stand barefoot with their patellae facing forward. The gold standard for anteroposterior knee radiographs includes (1) anterior orientation of the patella and (2) a slight overlap between the fibular head and tibia[14.15]. For the lateral views, the ideal criteria include (1) overlapping of the femoral condyles (or posterior condyles), (2) an open patellofemoral joint space, and (3) a slight overlap between the fibular head and tibia[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eHowever, in patients with deformities, achieving the ideal positioning is often challenging[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. This difficulty is exacerbated on long-leg radiographs, where ensuring uniform positioning across the entire limb is particularly demanding. Bellemans et al. also noted the limitations of using plain radiographs in their work[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThis study had several limitations. First, potential population-dependent factors, such as weight, height, and sex, were not analysed. Second, the sample size was relatively small. Third, CT image acquisition was performed in the prone position, whereas long-leg radiographs are typically taken in the standing, weight-bearing position, which may affect comparability.\u003c/p\u003e \u003cp\u003eIn addition, knee flexion was not evaluated in this study. The DRR images used in this study differ from conventional radiographs because they lack parallax effects. Finally, image rotation was limited to the mechanical axis of the lower limb. In real clinical scenarios, multiaxial rotation can occur. Future studies that incorporate more realistic, three-dimensional rotational models are warranted.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis study demonstrated that LDFA and MPTA are minimally affected by lower limb rotation, whereas the PTS is significantly influenced, particularly in cases with smaller MPTA values. Therefore, special attention should be paid to evaluating PTS on plain radiographs during preoperative planning, such as for TKA, as rotational positioning errors may lead to inaccurate PTS measurements. To ensure accurate preoperative assessment, optimisation of radiographic imaging protocols and use of supplemental imaging modalities are recommended.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eKA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eKinematic Alignment\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eTKA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eTotal Knee Arthroplasty\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eUKA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eUnicompartmental Knee Arthroplasty\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eLDFA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eLateral Distal Femoral Angle\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eMPTA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMedial Proximal Tibial Angle\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003ePTS\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ePosterior Tibial Slope\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eDRR\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eDigitally Reconstructed Radiograph\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eER\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eExternal rotation\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eIR\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eInternal rotation\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eMRI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMagnetic Resonance Imaging\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eCT\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eComputed Tomography\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eJLO\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eJoint Line Obliquity\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eMPR\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMultiplanar Reconstruction\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eSEA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSurgical Epicondylar Axis\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003ePCL\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eposterior cruciate ligament\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate:\u0026nbsp;\u003c/strong\u003eThe study protocol was reviewed and approved by the Institutional Review Board of Kindai University Nara Hospital (protocol identification number: 23–087).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication:\u0026nbsp;\u003c/strong\u003eInformed consent was obtained from all patients for the use of their medical data in this retrospective study.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated and/or analyzed during the current study are not publicly available due to the inclusion of sensitive patient information and privacy concerns, but are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors' contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNO, SM, AM, and KY participated in data collection, analysis and manuscript writing. YU, NS and KH participated in the study design. NO, SM, YU, and SN confirm the authenticity of all the raw data. 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\u003eSpecial thanks to the orthopedic surgery team, who assisted in the treatment of the patient.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eParvizi J, Nunley RM, Berend KR, Lombardi AV Jr., Ruh EL, Clohisy JC, et al. High level of residual symptoms in young patients after total knee arthroplasty. Clin Orthop Relat Res. 2014;472:133\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBlakeney W, Cl\u0026eacute;ment J, Desmeules F, Hagemeister N, Rivi\u0026egrave;re C, Vendittoli PA. Kinematic alignment in total knee arthroplasty better reproduces normal gait than mechanical alignment. Knee Surg Sports Traumatol Arthrosc. 2019;27:1410\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu B, Feng C, Tu C. Kinematic alignment versus mechanical alignment in primary total knee arthroplasty: an updated meta-analysis of randomized controlled trials. J Ortho Surg Res. 2022;17:201.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSarzaeem MM, Movahedinia M, Mirahmadi A, Abolghasemian M, Tavakoli M, Amouzadeh Omrani F. Kinematic alignment technique outperforms mechanical alignment in simultaneous bilateral total knee arthroplasty: a randomized controlled trial. J Arthroplasty. 2024;39:2234\u0026ndash;40.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOswald MH, Jakob RP, Schneider E, Hoogewoud HM. Radiological analysis of normal axial alignment of femur and tibia in view of total knee arthroplasty. J Arthroplasty. 1993;8:419\u0026ndash;26.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSanfridsson J, Arnbj\u0026ouml;rnsson A, Frid\u0026eacute;n T, Ryd L, Svahn G, Jonsson K. Femorotibial rotation and the Q-angle related to the dislocating patella. Acta Radiol. 2001;42:218\u0026ndash;24.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChung J, Lee J, Han HS, Lee MC, Ro DH. The effect of position on radiographic angle measurements of the lower extremities. BioMed Res Int. 2022;2022:1057227.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJamali AA, Meehan JP, Moroski NM, Anderson MJ, Lamba R, Parise C. Do small changes in rotation affect measurements of lower extremity limb alignment? JOrtho Surg Res. 2017;12:77.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eUtzschneider S, Goettinger M, Weber P, Horng A, Glaser C, Jansson V, et al. Development and validation of a new method for the radiologic measurement of the tibial slope. Knee Surg Sports Traumatol Arthosc. 2011;19:1643\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhang Y, Chen Y, Qiang M, Zhang K, Li H, Jiang Y, et al. Comparison between three-dimensional CT and conventional radiography in proximal tibia morphology. Medicine. 2018;97:e11632.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMacDessi SJ, Griffiths-Jones W, Harris IA, Bellemans J, Chen DB. Coronal Plane Alignment of the Knee (CPAK) classification. Bone Joint J. 2021;103\u0026ndash;B(2):329\u0026ndash;37.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBrenner DJ, Hall EJ. Computed tomography\u0026ndash;an increasing source of radiation exposure. N Engl J Med. 2007;357:2277\u0026ndash;84.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAbdelfadeel W, Houston N, Star A, Saxena A, Hozack WJ. CT planning studies for robotic total knee arthroplasty. Bone Joint J 2020;102-B(6_Supple_A):79\u0026ndash;84.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ede Rocha JL, Pedrinha ISM, Pav\u0026atilde;o DM, Albuquerque RPE, Sousa EB, Mandarino M, et al. Stress radiography for multiligament knee injuries: a standardized, step-by-step technique. Arthrosc Tech. 2020;9:e1885\u0026ndash;92.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVince AS, Singhania AK, Glasgow MM. What knee X-rays do we need? A survey of orthopaedic surgeons in the United Kingdom. Knee. 2000;7:101\u0026ndash;4.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang S, Xiao Z, Lu Y, Zhang Z, Lv F. Radiographic optimization of the lateral position of the knee joint aided by CT images and the maximum intensity projection technique. J Ortho Surg Res. 2021;16:581.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMoreland JR, Bassett LW, Hanker GJ. Radiographic analysis of the axial alignment of the lower extremity. J f Bone Joint Surg Am. 1987;69:745\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBellemans J, Colyn W, Vandenneucker H, Victor J. The Chitranjan Ranawat award: is neutral mechanical alignment normal for all patients? The concept of constitutional varus. Clin Ortho Relat Res. 2012;470:45\u0026ndash;53.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 to 3 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-orthopaedic-surgery-and-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"josr","sideBox":"Learn more about [Journal of Orthopaedic Surgery and Research](http://josr-online.biomedcentral.com)","snPcode":"13018","submissionUrl":"https://submission.nature.com/new-submission/13018/3","title":"Journal of Orthopaedic Surgery and Research","twitterHandle":"@MSKmedBMC","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Knee, Radiograph, Lower limb rotation","lastPublishedDoi":"10.21203/rs.3.rs-6628967/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6628967/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eLower limb rotation at the time of imaging may affect the measurement of joint line angles using plain radiographs, potentially compromising measurement accuracy. Accurate joint line angles are important for orthopaedic surgery planning and limb alignment. \u003cbr\u003e\nThis study aimed to investigate the changes in distal femoral and proximal tibial joint line angles in response to limb rotation, and evaluate the correlation between these changes using digitally reconstructed radiographs (DRRs) generated from computed tomography (CT) images.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePreoperative CT data from 50 knees scheduled for TKA or unicompartmental knee arthroplasty (UKA) at our institution were analysed using a TKA planning software. The femur and tibia were aligned perpendicularly to their mechanical axes in the coronal and sagittal planes. The surgical epicondylar axis (SEA) and Akagi’s line were used as references for femoral and tibial rotation, respectively, with 0° defined as neutral rotation. \u003cbr\u003e\nEach bone was rotated from 20° external to 20° internal rotation in 5° increments using the software, and DRR images were generated at each position. Lateral Distal Femoral Angle (LDFA), Medial Proximal Tibial Angle (MPTA), and Posterior Tibial Slope (PTS) were measured at each rotational angle. \u003cbr\u003e\nThe absolute values and their variations with rotation and correlations between each angle and their respective changes were analysed.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAt 0°, the mean ± SD values were 87.5 ± 2.4°, 83.9 ± 2.6°, and 8.4 ± 3.2° for LDFA, MPTA, and PTS, respectively. The mean changes across 20° external to 20° internal rotation were 0.3° (1.8°–0.6°), 1.1° (1.0°–1.5°), and 6.2° (1.9°–2.4°) for LDFA, MPTA, and PTS, respectively. MPTA was negatively correlated with ΔPTS (r = –0.7). Based on the MPTA values, the patients were categorized into: \u0026lt;82.5°, 82.5–84.5°, and \u0026gt;84.5° groups. ΔPTS was statistically significant different between the \u0026lt;82.5° (8.6 ± 2.3°) and 82.5–84.5° groups (6.9 ± 1.6°) and between the 82.5–84.5° and \u0026gt;84.5° groups (4.0 ± 1.9°) (p\u0026lt;0.05 and p\u0026lt;0.001, respectively).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eLimb rotation significantly affects PTS, particularly in cases with greater medial inclination of the tibial plateau. Therefore, caution must be exercised when using plain radiographs for preoperative planning or postoperative evaluation.\u003c/p\u003e","manuscriptTitle":"The effect of lower limb rotation on radiographic femoral and tibial joint line obliquity measurements, and the association between the measurements and their changes: a digitally reconstructed radiograph evaluation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-19 06:43:14","doi":"10.21203/rs.3.rs-6628967/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-06-09T15:39:49+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-09T10:38:48+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-06-08T12:53:23+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"103292835108964915454410184800623521985","date":"2025-05-19T13:42:05+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"168986197580435339824676289796969596122","date":"2025-05-19T01:04:54+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-05-13T12:00:53+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-05-12T05:16:17+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-05-12T00:50:58+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Orthopaedic Surgery and Research","date":"2025-05-09T12:58:52+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-orthopaedic-surgery-and-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"josr","sideBox":"Learn more about [Journal of Orthopaedic Surgery and Research](http://josr-online.biomedcentral.com)","snPcode":"13018","submissionUrl":"https://submission.nature.com/new-submission/13018/3","title":"Journal of Orthopaedic Surgery and Research","twitterHandle":"@MSKmedBMC","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"db98a094-49d6-440e-beef-1d8ecba23446","owner":[],"postedDate":"May 19th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-07-28T16:07:23+00:00","versionOfRecord":{"articleIdentity":"rs-6628967","link":"https://doi.org/10.1186/s13018-025-06106-2","journal":{"identity":"journal-of-orthopaedic-surgery-and-research","isVorOnly":false,"title":"Journal of Orthopaedic Surgery and Research"},"publishedOn":"2025-07-26 15:58:28","publishedOnDateReadable":"July 26th, 2025"},"versionCreatedAt":"2025-05-19 06:43:14","video":"","vorDoi":"10.1186/s13018-025-06106-2","vorDoiUrl":"https://doi.org/10.1186/s13018-025-06106-2","workflowStages":[]},"version":"v1","identity":"rs-6628967","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6628967","identity":"rs-6628967","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}