Measurement Study of the “Optimal” Screw Axis Location and Its Angles with the First and Second Metacarpals Based on X Imaging of the Scaphoid Bone

Measurement Study of the “Optimal” Screw Axis Location and Its Angles with the First and Second Metacarpals Based on X Imaging of the Scaphoid Bone | 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 Measurement Study of the “Optimal” Screw Axis Location and Its Angles with the First and Second Metacarpals Based on X Imaging of the Scaphoid Bone JingQuan Guo, Qianwen Jia, Bo Wu, Fei Xiao, Keke Cheng, Tianrun Lei This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6740135/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background: Accurate screw placement is critical for successful internal fixation of scaphoid fractures. However, during percutaneous Herbert screw fixation via the volar approach, there is currently no standardized anatomical reference for determining the entry point and screw axis. Traditional methods often rely on experience or intraoperative fluoroscopy, which can increase radiation exposure and reduce accuracy. This study aims to propose a novel reference method based on the angular relationship between the scaphoid screw axis and the first and second metacarpals, and to assess its anatomical consistency and potential clinical utility. Methods: A retrospective analysis was conducted on radiographs of healthy adults from 2021 to 2023, including anteroposterior and lateral wrist views. Two senior trainees and two experienced surgeons measured the imaging data. The measurements included the screw axis length, angles between the screw axis and metacarpal axes, skin thickness(the thickness beneath the skin of the scaphoid tubercle), and entry point distance(the vertical distance from the intersection of the extended screw axis with the palmar skin to the apex of the scaphoid tubercle). The influences of the thumb position, gender, and skin thickness on the screw axis orientation and entry point location were analyzed. Results: A total of 151 adults were analyzed, including 87 females (57.6%) and 64 males (42.4%) with an average age of 43.2 ± 15.9 years. In the lateral view, the mean angle between the screw axis and the second metacarpal axis was 71.5° ± 6.7°, with minimal variance, indicating high consistency across individuals. In the PA view, the angle between the screw axis and the first metacarpal axis varied with the thumb position: 4.8° ± 2.8° in abduction versus 18.7° ± 5.7° at rest. In some cases, the axes were nearly parallel in abduction. The screw axis length measured in the lateral view was closely aligned with that reported in previous anatomical studies(male 2.5 ± 0.3 cm vs female 2.2 ± 0.2 cm, p < 0.005). No significant correlation was found between subcutaneous thickness and entry point distance (r = 0.048, p = 0.559). Additionally, males had greater entry point distances (males 1.5 ± 0.3 cm vs females 1.3 ± 0.3 cm, p < 0.005). Conclusions: In this study, we find a defined anatomical relationship between the scaphoid screw axis and the axes of the first and second metacarpals. Additionally, the guidewire entry point on the skin should be located distal to the scaphoid tubercle, with the distance varying by gender. The second metacarpal is recommended as a lateral view guide because of its stability and consistency, whereas the first metacarpal can be used in the PA view, particularly when the thumb is in abduction. Further clinical validation through prospective studies is warranted. scaphoid positioning percutaneous fixation volar approach screw axis Figures Figure 1 Figure 2 Figure 3 Figure 4 Background Whether surgical treatment is necessary for acute, minimal(displacement < 1 mm without angular deformity or rotational instability), and nondisplaced scaphoid fractures is controversial 1 – 4 . However, early surgical intervention can lead to faster recovery of wrist joint function and reduce joint stiffness 3 , 5 , 6 . Given that scaphoid fractures are more common in young adults and athletes 4 , 7 , 8 , this point becomes particularly important. Percutaneous Herbert screw fixation remains an effective method for treating acute scaphoid fractures 2 , 9 . This approach provides significant biomechanical stability, creating favorable conditions for fracture healing 10 . Owing to the scaphoid being a waist-thin, cashew-shaped bone and its deep anatomical position and irregular shape, percutaneous retrograde Herbert screw fixation is challenging. Discussions have emerged regarding efficient methodologies for swiftly and precisely identifying the entry point and direction for pin insertion. 3D-printed guides—designed from preoperative CT data—have improved precision in percutaneous scaphoid fixation 11 , 12 , and robot-assisted systems offer accurate, minimally invasive screw placement 13 , 14 . However, both technologies require complex preoperative preparations, high costs, and lack widespread availability, limiting their utilization in standard clinical practice 15 . In conventional freehand screw placement, the scaphoid tubercle is typically used as the entry point 16 . With the forearm supinated and the wrist dorsiflexed, the guidewire is advanced toward Lister’s tubercle at a 45° angle to the forearm 16 , 17 . This approach relies on a vague, experience-based reference system that offers limited guidance for freehand screw placement. We aimed to establish a more precise framework to guide clinical insertion. On the basis of clinical experience, the anatomical positions of the carpal and metacarpal bones are relatively stable, with the scaphoid in close proximity to the first and second metacarpals, Moreover, the first and second metacarpals exhibit distinct surface landmarks suitable for reference. The objective of this study was to propose a novel method for determining the entry point and trajectory of scaphoid screw insertion by analyzing the spatial relationship between the scaphoid screw axis and the axes of the first and second metacarpals. This approach aims to provide theoretical support for volar scaphoid fixation techniques. Methods Participants We retrospectively selected adult outpatients (aged > 18 years) who underwent posteroanterior and lateral wrist radiographs at our hospital between 2020 and 2022. Their demographic data were recorded.All participants were excluded if he/she had (1)previous wrist surgery; (2)history of distal radius or carpal bone fractures; (3) traumatic events involving the wrist or hand within the past six months; (4) presence of positive or negative ulnar variance; (5) developmental abnormalities of the forearm or wrist joint; (6) neurological or muscular system disorders. No additional examinations were performed on any participants, and this study utilized the initial scan results without any modifications. All participants were informed of the study's protocol and objectives and provided written informed consent. This study’s protocol was approved by the Ethics Committee of Wuhan Fourth Hospital, and the data were collected and maintained in accordance with the approved guidelines. All participants were informed of the study's protocol and objectives and provided written informed consent. Evaluation Procedure Two senior surgical trainees and two experienced hand surgeons participated in this study to analyze the radiographs. All the participants were thoroughly instructed on the parameter measurement methods and independently conducted the measurements.The results were collected to calculate the average value, which was taken as the final measurement result for statistical analysis. Image measurements were performed via the uWS-RAD workstation (version 5.1, United Imaging Healthcare, Shanghai, China). Data measurement methods On the anteroposterior X-ray of the wrist(Fig. 1 ), we define the “screw axis” as the line connecting the central third of the scaphoid's upper surface projection with the most proximal ulnar corner, and measure the length of the “screw axis” and the angle it forms with the axes of the first and second metacarpals(defining the dorsal bone cortex of the first metacarpal as the axis, and the line connecting the midpoints of the upper and lower articular surfaces of the second metacarpal as the axis). On the lateral X-ray image of the wrist(Fig. 2 ), the “screw axis” is defined by a line connecting the proximal point with the central third of the scaphoid's upper surface.On this basis, the length of the “screw axis”, the angle it forms with the axes of the first and second metacarpals(the axis of the first metacarpal is defined as the line connecting the midpoints of the proximal and distal joint surfaces, and the axis of the second metacarpal is the dorsal cortical line), the skin thickness(the thickness beneath the skin of the scaphoid tubercle), and the entry point distance (the vertical distance from the intersection of the extended screw axis with the palmar skin to the apex of the scaphoid tubercle) are measured. In the anteroposterior view, the dorsal cortex of the first metacarpal is defined as the axis of the first metacarpal because it corresponds to the lateral edge of the thumb on the skin surface, making it convenient for clinical reference. Similarly, in the lateral view, the dorsal cortex of the second metacarpal corresponds to the posterior edge of the palm, facilitating reference and utilization Owing to the thumb’s wide range of motion, consistent positioning during measurement was not feasible. Therefore, we separately measured the angle between the scaphoid screw axis and the first metacarpal axis with the thumb in abduction and at rest. Statistics To enhance the generalizability of our measurement results, we analyzed as many samples as possible. Statistical analysis was carried out via SPSS version 24 for Windows (IBM Corp). The normality of the quantitative data was tested via the Shapiro-Wilk test. Data following a normal distribution are expressed as the mean ± standard deviation unless the data are presented as the interquartile range. The independent samples t-test was uesd to detect whether there were differences in the same measurement items between different groups. Pearson’s test was used to determine whether there was a link between the skin thickness and the entry point distance. A P value of 0 .05 or less was considered statistically significant. Analyze the variability of the measured angles in both the anteroposterior and lateral radiographs separately Results 151 patients were analyzed,including 87 (57.6%) women and 64 (42.4%) men with an average age of 43.2 ± 15.9 years (range 18–79 years). Among them, 70 cases were on the left side and 81 cases were on the right side. In 86 patients, the thumb was in the resting position; in 65 patients, it was in the abducted position. All the data and statistical results are presented in the Table 1 - 4 . In the anteroposterior view, there was a significant difference in the length of the screw axis between different genders (male 2.0 ± 0.3 cm vs female 1.8 ± 0.3 cm, p < 0.005). In the lateral view, there were significant differences in the length of the screw axis (male 2.5 ± 0.3 cm vs female 2.2 ± 0.2 cm, p < 0.005 and the entry point distance༈Male 1.5 ± 0.3cm vs Female 1.3 ± 0.3cm, p < 0.005) between male and female groups. The remaining values showed no significant differences between the groups. Correlation analysis of skin thickness and entry point distance revealed that there was no significant correlation between the two variables(Fig. 3 ). The distance to the entry point did not increase with increasing skin thickness beneath the tubercle of the scaphoid(r = 0.048,p = 0.559). In the anteroposterior view, the thumb position affected the angle (abducted: 4.8° ± 2.8°; resting: 18.7° ± 5.7°). When the thumb was abducted, the first metacarpal axis was more closely aligned with the screw axis, and in some patients(Fig. 4 ), the two axes were nearly parallel. In contrast, in the lateral view, the thumb position seemed to have no impact on the angle (abducted: 52.1° ± 15.6°; resting: 55.0° ± 12.9°). Table 1 Measured values of the main parameters in anteroposterior view parameters Total Left side Right side Male Female Angle between screw axis and first metacarpal axis(degree) Abducted position (n = 65) 4.8 ± 2.8 4.6 ± 2.7 5.0 ± 2.8 4.7 ± 2.5 4.8 ± 2.9 Resting position (n = 86) 18.7 ± 5.7 18.7 ± 5.4 18.6 ± 6.1 16.8 ± 5.1 19.9 ± 5.8 Angle between screw axis and second metacarpal axis(degree) 32.4 ± 8.0 32.0 ± 7.3 32.8 ± 8.5 32.3 ± 7.1 32.5 ± 8.6 Length of screw axis (cm) 1.9 ± 0.3 1.9 ± 0.3 1.9 ± 0.3 2.0 ± 0.3 1.8 ± 0.3 Table 2 Measured values of the main parameters in lateral view parameters Total Left side Right side Male Female Angle between screw axis and first metacarpal axis(degree) Abducted position (n = 65) 52.1 ± 15.6 46.4 ± 12.7 58.4 ± 13.5 52.6 ± 14.0 51.5 ± 14.9 Resting position (n = 86) 55.0 ± 12.9 53.7 ± 14.3 55.9 ± 11.9 52.2 ± 12.9 56.5 ± 12.8 Angle between screw axis and second metacarpal axis(degree) 71.5 ± 6.7 69.3 ± 6.1 73.3 ± 6.6 72.3 ± 6.7 70.8 ± 6.6 Length of screw axis (cm) 2.3 ± 0.3 2.4 ± 0.3 2.3 ± 0.3 2.5 ± 0.3 2.2 ± 0.2 skin thickness of scaphoid tubercle (cm) 0.6 ± 0.2 0.6 ± 0.2 0.6 ± 0.3 0.6 ± 0.2 0.6 ± 0.2 entry point distance (cm) 1.4 ± 0.3 1.5 ± 0.3 1.2 ± 0.2 1.5 ± 0.3 1.3 ± 0.3 Table 3 Independent samples t-test in anteroposterior view parameters Left side Right side Male Female t values p values t values p values Angle between screw axis and first metacarpal axis(degree) Abducted position (n = 65) 1.315 0.193 2.958 0.176 Resting position (n = 86) 1.436 0.324 2.156 0267 Angle between screw axis and second metacarpal axis(degree) 0.815 0.418 -0.138 0.89 Length of screw axis (cm) -0.322 0.749 -4.714 0.001 Table 4 Independent samples t-test in lateral view parameters Left side Right side Male Female t values p values t values p values Angle between screw axis and first metacarpal axis(degree) Abducted position (n = 65) 1.307 0.196 1.044 0.298 Resting position (n = 86) 1.742 0.054 2.076 0.023 Angle between screw axis and second metacarpal axis(degree) 3.013 0.004 -1.389 0.167 Length of screw axis (cm) 0.013 0.989 -7.134 < 0.001 skin thickness of scaphoid tubercle (cm) 0.061 0.951 -2.495 0.014 entry point distance (cm) -1.255 0.216 -3.569 0.002 Discussion Accurate implantation of the Herbert screw guide wire is crucial for surgery. Accurate implantation requires two conditions: 1. Determining the correct skin entry point; 2. The direction of the guide wire should align with the three-dimensional axis of the scaphoid. On the basis of this principle, we conducted measurement studies using X-rays and analyzed the entry point of the guide wire along with three-dimensional reference objects . Currently, there is no consensus on the optimal entry point and axis for percutaneous screw placement. Traditionally, the scaphoid tubercle is used as the entry point t 18 – 21 , with screws aligned centrally and maximized in length 22 – 24 . Evan L. et al 25 . suggested that the ideal starting point for the maximum screw axis is located 1.7 mm dorsal and 0.2 mm radial from the apex of the scaphoid tubercle.However, the volar retrograde approach presents challenges: a centrally placed entry point risks trapezial obstruction 23 and scaphotrapezial arthritis 23 , 26 , whereas the entry point is near the volar side of the scaphoid tuberosity, there is a risk of penetrating the volar cortex, and may cause a "humpback" deformity. While most authors agree that the screw should follow the scaphoid axis, the precise definition of this axis has not been clearly established in the literature. Menapace et al 27 . used cadaveric measurements to define a safe zone for screw insertion that avoids vascular and articular damage, moving 15% of the contralateral scaphoid lateral length—approximately 30% of its width—posteriorly and distally from the volar side of the scaphoid tubercle. Meermans et al 28 . reported that the transtrapezia technique can reliably place screws within the central one-third of the distal pole, but when they approach through the volar scaphoid tubercle, the screws are placed outside the central one-third of the distal pole. Similarly, Keith W et al 24 . found that the volar approach involves approximately the central one-third of the distal pole. On the basis of previous studies, the central one-third of the distal pole on th scaphoid(approximately 30% of its width from the scaphoid tubercle) may represent a critical location for the volar approach, as it neither compromises the blood supply and cortex on the volar side nor damages the scaphotrapezial articular surface while maximizing the central placement of the screw. In this study, we chose the central one-third of the distal scaphoid as the entry point, and the target point of the screw axis was selected as the most proximal ulnar corner to achieve a greater distance,as described in the study by Dean et al 29 . The longest screw length leads to the best bone purchase and greater biomechanical stability for increased construct strength 22 , 30 . ​In this study, we devised a method to define the screw axis. Importantly, the “optimal” screw axis represents the ideal angle and direction without considering the orientation of the fracture line. When a volar approach is used for screw insertion, this axis can serve as a reference, allowing for appropriate adjustments on the basis of the specific clinical situation. Previous studies 31 , 32 have proposed marking the screw axis on the skin via intraoperative fluoroscopy in both the anteroposterior and lateral views to guide freehand insertion. This approach inevitably increases fluoroscopy exposure. Our measurements revealed that the scaphoid screw axis forms consistent angles with the first and second metacarpals, which can serve as anatomical references for the direction of the guidewire. In the lateral view, although the thumb position has minimal influence, the angle between the second metacarpal and the screw axis shows less variability (smaller standard deviation), making it a more stable reference (71.5°). Therefore, we recommend using the second metacarpal as a guide in the lateral view. In the anteroposterior view, owing to the limited visibility of the second metacarpal, the first metacarpal may serve as a more practical reference. However, its position must be considered: approximately 18.7° when it is at rest and 4.8° when abducted. Preoperative anteroposterior wrist radiographs can be taken with the thumb in abduction to assess whether the screw axis aligns parallel to the first metacarpal axis, thereby facilitating simplified intraoperative guidance. Our study revealed that the guidewire entry point should not be placed directly over the scaphoid tubercle, as this may result in a volar deviation of the screw; instead, it should be positioned distal to the tubercle, with a distance of approximately 1.3 mm in females and approximately 1.5 mm in males. Initially, we hypothesized that there would be a positive correlation between skin thickness over the scaphoid tubercle and the distance to the guidewire entry point, on the basis of trigonometric principles. However, analysis revealed no significant correlation (p = 0.559), suggesting that the entry point remains relatively constant regardless of subcutaneous thickness. This may be because the scaphoid tubercle is a bony protrusion with less subcutaneous fat, making it less likely to accumulate fat, which does not significantly affect the entry point. Nonetheless, potential bias and a limited sample size cannot be excluded. The length of the scaphoid long axis has long been a topic of discussion. Kong et al 18 . measured 84 scaphoid specimens and reported that the length of the scaphoid in males was 27.92 mm, while in females was 26.47 mm. However, considering the requirements for subchondral screw placement, the recommended screw length is between 18 to 25 mm. Evan L. et al 25 . found the optimal screw axis length to be 25–28 mm using 3D models. Guo et al 33 ., through 3D CT reconstruction of 30 pairs of wrist joints in Chinese, measured average scaphoid axis lengths of 29.3 mm in males and 26.6 mm in females. Similarly, Meermans et al 34 . reported central axis lengths of 27.14 mm in males and 23.86 mm in females via 3D CT analysis. We measured the length of the scaphoid screw axis via two-dimensional radiographs. Owing to the projection angles, the lateral view length is longer than the anteroposterior view length. Clinically, to avoid the use of screws that are too short, the lateral view length is preferred as the reference. The length of the screw axis we defined on the lateral view(male 2.5 ± 0.3 cm, female 2.2 ± 0.2 cm) closely aligns with the scaphoid long axis values reported in previous studies. Considering the impact of the screw diameter, to avoid penetrating the joint surface, the actual length of the screw used should be shorter than the length of the screw axis by approximately 2-4mm 34 , 28 This study has several limitations. While prior studies often used CT or cadaveric samples to determine optimal screw positioning—with greater consistency and clarity—these methods have limited clinical applicability. Our screw axis was defined via X-rays, as the orientation of the screw is guided by intraoperative fluoroscopy, our approach is more applicable in practice. Additionally, sample size and selection bias may have affected our findings, highlighting the need for larger-scale studies. Although this study focused primarily on proposing a novel anatomical reference for scaphoid screw insertion and validating its theoretical feasibility, we recognize its potential clinical value. Preliminary findings suggest that this method may offer more precise guidance for volar scaphoid fixation. In future work, we plan to conduct clinical trials in collaboration with surgeons to assess the safety, efficacy, and practical utility of this approach, aiming to facilitate its translation from theory to clinical practice. Conclusions We propose a novel reference method for guidewire placement in scaphoid fracture surgery. Specifically, we suggest that the guidewire can be inserted at an angle of 71.5° relative to the dorsum of the hand (aligned with the second metacarpal axis) in the lateral view, and at an angle of 18.7° relative to the lateral edge of the thumb (aligned with the first metacarpal axis) in the anteroposterior view when the thumb is at rest, or at an angle of 4.8° when the thumb is abducted. Preoperatively, obtaining a wrist radiograph with the thumb in abduction can help assess whether the lateral edge of the thumb is parallel to the intended screw axis, thereby providing a more stable reference for screw insertion. The skin entry point is approximately 1.48 cm from the scaphoid tubercle in male patients and 1.26 cm in female patients. The recommended screw length is 2.1–2.3 cm for males and 1.8-2.0 cm for females Declarations Author contributions Jingquan Guo, Bo Wu, and Fei Xiao were responsible for data measurement and study design. Jingquan Guo and Bo Wu conducted the literature review and contributed to manuscript drafting and revision. Qianwen Jia performed the statistical analysis. Keke Cheng and Tianrun Lei was involved in protocol development, gaining ethical approval. All authors reviewed and edited the manuscript and approved the final version of the manuscript Funding The authors received no financial support for the research, authorship, and/or publication of this article. Data availability The data supporting this study's findings are not publicly available due to sensitivity concerns but can be obtained from the corresponding author upon reasonable request. Ethics approval and consent to participate Ethical approval for this study was obtained from the Ethics Committee of the Wuhan Fourth Hospital(KY2024-192-01). All participants and/or their legal guardians provided informed consent prior to enrollment. To ensure privacy, no identifying information has been disclosed. 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Antegrade Versus Retrograde Technique for Fixation of Scaphoid Waist Fractures: A Comparison of Screw Placement. Jnl Wrist Surg . 2020;09(01):034-038. doi:10.1055/s-0039-1698745 Soubeyrand M, Biau D, Mansour C, Mahjoub S, Molina V, Gagey O. Comparison of Percutaneous Dorsal Versus Volar Fixation of Scaphoid Waist Fractures Using a Computer Model in Cadavers. The Journal of Hand Surgery . 2009;34(10):1838-1844. doi:10.1016/j.jhsa.2009.07.012 Chan KW, McAdams TR. Central screw placement in percutaneous screw scaphoid fixation: a cadaveric comparison of proximal and distal techniques. The Journal of Hand Surgery . 2004;29(1):74-79. doi:10.1016/j.jhsa.2003.09.002 Leventhal EL, Wolfe SW, Walsh EF, Crisco JJ. A Computational Approach to the “Optimal” Screw Axis Location and Orientation in the Scaphoid Bone. The Journal of Hand Surgery . 2009;34(4):677-684. doi:10.1016/j.jhsa.2009.01.011 Kang KB, Kim HJ, Park JH, Shin YS. Comparison of Dorsal and Volar Percutaneous Approaches in Acute Scaphoid Fractures: A Meta-Analysis. Harhaus L, ed. PLoS ONE . 2016;11(9):e0162779. doi:10.1371/journal.pone.0162779 Menapace KA, Larabee L, Arnoczky SP, Neginhal VS, Dass AG, Ross LM. Anatomic placement of the Herbert-Whipple screw in scaphoid fractures: A cadaver study. The Journal of Hand Surgery . 2001;26(5):883-892. doi:10.1053/jhsu.2001.27755 Meermans G, Van Glabbeek F, Braem MJ, Van Riet RP, Hubens G, Verstreken F. Comparison of Two Percutaneous Volar Approaches for Screw Fixation of Scaphoid Waist Fractures: Radiographic and Biomechanical Study of an Osteotomy-Simulated Model. The Journal of Bone and Joint Surgery . 2014;96(16):1369-1376. doi:10.2106/JBJS.L.01729 Dean BJF, Riley ND, McCulloch ER, Lane JCE, Touzell AB, Graham AJ. A new acute scaphoid fracture assessment method: a reliability study of the ‘long axis’ measurement. BMC Musculoskelet Disord . 2018;19(1):310. doi:10.1186/s12891-018-2236-y Ramos-Marques N, Ferrão A, Morais B, Barreira M, Teixeira F. Percutaneous Scaphoid Fixation: Experience Value among Different Approaches. J Wrist Surg . 2021;10(01):023-026. doi:10.1055/s-0040-1716352 Meermans G, Verstreken F. Percutaneous Transtrapezial Fixation of Acute Scaphoid Fractures. J Hand Surg Eur Vol . 2008;33(6):791-796. doi:10.1177/1753193408092785 Verstreken F, Meermans G. Transtrapezial Approach for Fixation of Acute Scaphoid Fractures. JBJS Essential Surgical Techniques . 2015;5(4):e29. doi:10.2106/JBJS.ST.O.00052 Guo Y, Tian GL. The length and position of the long axis of the scaphoid measured by analysis of three-dimensional reconstructions of computed tomography images. J Hand Surg Eur Vol . 2011;36(2):98-101. doi:10.1177/1753193410377837 Meermans G, Verstreken F. Influence of Screw Design, Sex, and Approach in Scaphoid Fracture Fixation. Clinical Orthopaedics & Related Research . 2012;470(6):1673-1681. doi:10.1007/s11999-011-2218-y 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. 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-6740135","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":465872263,"identity":"ce9a49a6-10cf-4203-bae3-1a3f6cd6950b","order_by":0,"name":"JingQuan Guo","email":"","orcid":"","institution":"The Wuhan Fourth Hospital, China","correspondingAuthor":false,"prefix":"","firstName":"JingQuan","middleName":"","lastName":"Guo","suffix":""},{"id":465872264,"identity":"f05cd9a4-0ebb-4746-81fb-02b84a1cfca5","order_by":1,"name":"Qianwen Jia","email":"","orcid":"","institution":"Beijing Chaoyang District Seventh Retired Cadre","correspondingAuthor":false,"prefix":"","firstName":"Qianwen","middleName":"","lastName":"Jia","suffix":""},{"id":465872265,"identity":"ec3b1cdd-e74b-4e90-80f1-396925479178","order_by":2,"name":"Bo Wu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAyUlEQVRIiWNgGAWjYBACfvaG9A8SBjU8QAaRWiR7DjxjsCg4JgdkEKnF4EbiM4aKD8zGBjcSiNVyIDntwQ0DtsQNNx9vvMFQYxNN2GEHjqUbzjCQSZx5O63YguFYWm4DIS18B3sSpCWAtvTdzjGTYGw4TFgLw2H+D9J/DJgTG26eIVKLwDGGNAkJA2ZjgRs8RGqR7GFINpAwAAUy0C8JxPiFX/5B4gOJP6CoPLzxxocaGyL8ggQMJBJIUQ7RQqqOUTAKRsEoGBkAAKtDQ6OWQ/QfAAAAAElFTkSuQmCC","orcid":"","institution":"The Wuhan Fourth Hospital, China","correspondingAuthor":true,"prefix":"","firstName":"Bo","middleName":"","lastName":"Wu","suffix":""},{"id":465872266,"identity":"ad533496-bf16-4427-9170-94a784b0a834","order_by":3,"name":"Fei Xiao","email":"","orcid":"","institution":"The Wuhan Fourth Hospital, China","correspondingAuthor":false,"prefix":"","firstName":"Fei","middleName":"","lastName":"Xiao","suffix":""},{"id":465872267,"identity":"56bce2fa-b560-401c-9c92-45634115fc7d","order_by":4,"name":"Keke Cheng","email":"","orcid":"","institution":"The Wuhan Fourth Hospital, China","correspondingAuthor":false,"prefix":"","firstName":"Keke","middleName":"","lastName":"Cheng","suffix":""},{"id":465872268,"identity":"1dfe6a5b-2df4-40fa-a1c3-ddb4b4a7e45e","order_by":5,"name":"Tianrun Lei","email":"","orcid":"","institution":"The Wuhan Fourth Hospital, China","correspondingAuthor":false,"prefix":"","firstName":"Tianrun","middleName":"","lastName":"Lei","suffix":""}],"badges":[],"createdAt":"2025-05-24 16:38:21","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6740135/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6740135/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":83917360,"identity":"aa2c0782-83ae-44d8-ad9e-4cdadd00d168","added_by":"auto","created_at":"2025-06-04 12:57:28","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":406265,"visible":true,"origin":"","legend":"\u003cp\u003eOn the anteroposterior X-ray of the wrist, the DE is the optimal screw axis.BC, DE, and GH are three parallel lines. AB and FG represent the axes of the first and second metacarpals, respectively.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6740135/v1/2e5c0ee7ad58319d72b3040f.png"},{"id":83916408,"identity":"b46a87ad-d21d-4595-8af8-7a3b24a2890e","added_by":"auto","created_at":"2025-06-04 12:49:28","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":241309,"visible":true,"origin":"","legend":"\u003cp\u003eOn the lateral X-ray of the wrist, the XF is the optimal screw axis. XF, HI, and KL are three parallel lines. Point E is where the extended XF line intersects the skin of the palm. AB represents the distance to the entry point, and CD represents the skin thickness of the scaphoid tubercle. GH and JK represent the axes of the first and second metacarpals, respectively\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6740135/v1/d4a22c73d3caaaae71a7a4f9.png"},{"id":83917361,"identity":"923c6b6f-672f-4bd4-982d-78e96b79f261","added_by":"auto","created_at":"2025-06-04 12:57:28","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":283817,"visible":true,"origin":"","legend":"\u003cp\u003eA scatter chart representing the relationship between skin thickness and entry point distance. Pearson's test revealed an r- value of 0.048 and a p-value of 0.559, indicating that there was no significant correlation between the two variables.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6740135/v1/76ba2803d5704113b9fcc767.png"},{"id":83916410,"identity":"b40d55e9-7dd1-4bfc-a25a-61402acb58c5","added_by":"auto","created_at":"2025-06-04 12:49:28","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":443960,"visible":true,"origin":"","legend":"\u003cp\u003ePortions of the patients whose thumb was in the abducted position.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6740135/v1/dda5652774da6da780d4fc04.png"},{"id":88556185,"identity":"5ce081a6-89bc-4132-97cb-e81b773319fc","added_by":"auto","created_at":"2025-08-07 16:31:38","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3413665,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6740135/v1/64771312-c388-4da1-9a44-b677bebdb9c4.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Measurement Study of the “Optimal” Screw Axis Location and Its Angles with the First and Second Metacarpals Based on X Imaging of the Scaphoid Bone","fulltext":[{"header":"Background","content":"\u003cp\u003eWhether surgical treatment is necessary for acute, minimal(displacement \u0026lt; 1 mm without angular deformity or rotational instability), and nondisplaced scaphoid fractures is controversial\u003csup\u003e\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e–\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. However, early surgical intervention can lead to faster recovery of wrist joint function and reduce joint stiffness\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Given that scaphoid fractures are more common in young adults and athletes\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e, this point becomes particularly important. Percutaneous Herbert screw fixation remains an effective method for treating acute scaphoid fractures\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. This approach provides significant biomechanical stability, creating favorable conditions for fracture healing\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eOwing to the scaphoid being a waist-thin, cashew-shaped bone and its deep anatomical position and irregular shape, percutaneous retrograde Herbert screw fixation is challenging. Discussions have emerged regarding efficient methodologies for swiftly and precisely identifying the entry point and direction for pin insertion. 3D-printed guides—designed from preoperative CT data—have improved precision in percutaneous scaphoid fixation \u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e, and robot-assisted systems offer accurate, minimally invasive screw placement\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. However, both technologies require complex preoperative preparations, high costs, and lack widespread availability, limiting their utilization in standard clinical practice\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIn conventional freehand screw placement, the scaphoid tubercle is typically used as the entry point\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. With the forearm supinated and the wrist dorsiflexed, the guidewire is advanced toward Lister’s tubercle at a 45° angle to the forearm\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. This approach relies on a vague, experience-based reference system that offers limited guidance for freehand screw placement. We aimed to establish a more precise framework to guide clinical insertion. On the basis of clinical experience, the anatomical positions of the carpal and metacarpal bones are relatively stable, with the scaphoid in close proximity to the first and second metacarpals, Moreover, the first and second metacarpals exhibit distinct surface landmarks suitable for reference.\u003c/p\u003e \u003cp\u003eThe objective of this study was to propose a novel method for determining the entry point and trajectory of scaphoid screw insertion by analyzing the spatial relationship between the scaphoid screw axis and the axes of the first and second metacarpals. This approach aims to provide theoretical support for volar scaphoid fixation techniques.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e "},{"header":"Methods","content":"\u003cp\u003eParticipants We retrospectively selected adult outpatients (aged \u0026gt; 18 years) who underwent posteroanterior and lateral wrist radiographs at our hospital between 2020 and 2022. Their demographic data were recorded.All participants were excluded if he/she had (1)previous wrist surgery; (2)history of distal radius or carpal bone fractures; (3) traumatic events involving the wrist or hand within the past six months; (4) presence of positive or negative ulnar variance; (5) developmental abnormalities of the forearm or wrist joint; (6) neurological or muscular system disorders. No additional examinations were performed on any participants, and this study utilized the initial scan results without any modifications. All participants were informed of the study's protocol and objectives and provided written informed consent. This study’s protocol was approved by the Ethics Committee of Wuhan Fourth Hospital, and the data were collected and maintained in accordance with the approved guidelines. All participants were informed of the study's protocol and objectives and provided written informed consent.\u003c/p\u003e\u003cp\u003eEvaluation Procedure\u003c/p\u003e\u003cp\u003eTwo senior surgical trainees and two experienced hand surgeons participated in this study to analyze the radiographs. All the participants were thoroughly instructed on the parameter measurement methods and independently conducted the measurements.The results were collected to calculate the average value, which was taken as the final measurement result for statistical analysis. Image measurements were performed via the uWS-RAD workstation (version 5.1, United Imaging Healthcare, Shanghai, China).\u003c/p\u003e\u003cp\u003eData measurement methods\u003c/p\u003e\u003cp\u003eOn the anteroposterior X-ray of the wrist(Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), we define the “screw axis” as the line connecting the central third of the scaphoid's upper surface projection with the most proximal ulnar corner, and measure the length of the “screw axis” and the angle it forms with the axes of the first and second metacarpals(defining the dorsal bone cortex of the first metacarpal as the axis, and the line connecting the midpoints of the upper and lower articular surfaces of the second metacarpal as the axis).\u003c/p\u003e\u003cp\u003eOn the lateral X-ray image of the wrist(Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), the “screw axis” is defined by a line connecting the proximal point with the central third of the scaphoid's upper surface.On this basis, the length of the “screw axis”, the angle it forms with the axes of the first and second metacarpals(the axis of the first metacarpal is defined as the line connecting the midpoints of the proximal and distal joint surfaces, and the axis of the second metacarpal is the dorsal cortical line), the skin thickness(the thickness beneath the skin of the scaphoid tubercle), and the entry point distance (the vertical distance from the intersection of the extended screw axis with the palmar skin to the apex of the scaphoid tubercle) are measured.\u003c/p\u003e\u003cp\u003eIn the anteroposterior view, the dorsal cortex of the first metacarpal is defined as the axis of the first metacarpal because it corresponds to the lateral edge of the thumb on the skin surface, making it convenient for clinical reference. Similarly, in the lateral view, the dorsal cortex of the second metacarpal corresponds to the posterior edge of the palm, facilitating reference and utilization\u003c/p\u003e\u003cp\u003eOwing to the thumb’s wide range of motion, consistent positioning during measurement was not feasible. Therefore, we separately measured the angle between the scaphoid screw axis and the first metacarpal axis with the thumb in abduction and at rest.\u003c/p\u003e\u003cp\u003eStatistics\u003c/p\u003e\u003cp\u003eTo enhance the generalizability of our measurement results, we analyzed as many samples as possible. Statistical analysis was carried out via SPSS version 24 for Windows (IBM Corp). The normality of the quantitative data was tested via the Shapiro-Wilk test. Data following a normal distribution are expressed as the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation \u003cimg src=\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADoAAAATCAYAAADBGB7WAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsMAAA7DAcdvqGQAAAKtSURBVFhH7Zbfa5JhFMeP+w/EqJuikbIla3eCZmJMEkSpKAKt7qIhSbmLSFkFwcKFsEHdzB8E1U0iRRfFQKHsB+aSClxD9kNti7rZ1Ish2y7f3nN8XlFZ+ioobfWBw/Oe8zwvvOc95/k+j4TjgX+AHjbuev4nutuoSTT0/BVoDGeZt7MZvnYTbt+dZB4PihEyv5jl1ENnaKzm/tQjitfb5aujbEVreL1eTi6XM6+znLIOc0+fvaTnSqL44bfGJpjXOdpNNBQK0bupVIorFAos2hhMEouCUOvG3s/AXHoBDHotVflvw2azwfr6Omi1WohGo6BWq9lMY86fO0njA9/j8h6NfUjAvr17wHD8KE0ICHv2wqURFgG4N+mj2MJSjkU6TzgcBqPRCDqdDlwuFygUCjbTnBNDx/hCJsqJzqUXYXCgnyYEMJG1fBHG79yA7ys/4fPXb/Rneg/uh0+xF3C4T85WNgc/TCKRkLndbsjlchUfLR6Ps5XbI5VKweFwQLFYJN/pdNIohgFlH6yuFcpihH2MovMnDJaL3Ih7jBufmGKR9mlnj05PT3N8svQePrfCm3cJyq9HTAsOHumHZb6qo9evsEh3MZvNkMlkwGq1gsVioeq2So+YFtzY2GJP3Wd2dpZMJpOBx+MBv98PPp+PYq1AexSFKF8o9389uC8P9R6gPu+mAAmUSiVSWgG73U4jxsWwmuf3Jw8likKEglQPqu7m5lalZeMzXyiG1i6omtlslnniCAaDEAgESLSwbVUqFSiVSjbbmPT8EhWSEsXzEyuG5ymClcMjBBcJSZ62GOHhkzCs/PhVOZ/EYjKZalS23hqpLiaUTCZBo9FAIpEAvV4PkUiEWlkMr99+5I9N/n7AxKlrN6NuUn0zanrX3clse9dFqv/ATqe2QznuN0G94l8SbOf0AAAAAElFTkSuQmCC\"\u003e\u0026nbsp;unless the data are presented as the interquartile range. The independent samples t-test was uesd to detect whether there were differences in the same measurement items between different groups. Pearson\u0026rsquo;s test was used to determine whether there was a link between the skin thickness and the entry point distance. A P value of 0 .05 or less was considered statistically significant. Analyze the variability of the measured angles in both the anteroposterior and lateral radiographs separately\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e151 patients were analyzed,including 87 (57.6%) women and 64 (42.4%) men with an average age of 43.2\u0026thinsp;\u0026plusmn;\u0026thinsp;15.9 years (range 18\u0026ndash;79 years). Among them, 70 cases were on the left side and 81 cases were on the right side. In 86 patients, the thumb was in the resting position; in 65 patients, it was in the abducted position. All the data and statistical results are presented in the Table\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e-\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eIn the anteroposterior view, there was a significant difference in the length of the screw axis between different genders (male 2.0\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3 cm vs female 1.8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3 cm, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005). In the lateral view, there were significant differences in the length of the screw axis (male 2.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3 cm vs female 2.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2 cm, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005 and the entry point distance༈Male 1.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3cm vs Female 1.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3cm, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005) between male and female groups. The remaining values showed no significant differences between the groups. Correlation analysis of skin thickness and entry point distance revealed that there was no significant correlation between the two variables(Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The distance to the entry point did not increase with increasing skin thickness beneath the tubercle of the scaphoid(r\u0026thinsp;=\u0026thinsp;0.048,p\u0026thinsp;=\u0026thinsp;0.559).\u003c/p\u003e \u003cp\u003eIn the anteroposterior view, the thumb position affected the angle (abducted: 4.8\u0026deg; \u0026plusmn; 2.8\u0026deg;; resting: 18.7\u0026deg; \u0026plusmn; 5.7\u0026deg;). When the thumb was abducted, the first metacarpal axis was more closely aligned with the screw axis, and in some patients(Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), the two axes were nearly parallel. In contrast, in the lateral view, the thumb position seemed to have no impact on the angle (abducted: 52.1\u0026deg; \u0026plusmn; 15.6\u0026deg;; resting: 55.0\u0026deg; \u0026plusmn; 12.9\u0026deg;).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMeasured values of the main parameters in anteroposterior view\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eparameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLeft side\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRight side\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAngle between screw axis and first metacarpal axis(degree)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAbducted position (n\u0026thinsp;=\u0026thinsp;65)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e4.8\u0026thinsp;\u0026plusmn;\u0026thinsp;2.8\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e4.6\u0026thinsp;\u0026plusmn;\u0026thinsp;2.7\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e5.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2.8\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e4.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e4.8\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eResting position (n\u0026thinsp;=\u0026thinsp;86)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e18.7\u0026thinsp;\u0026plusmn;\u0026thinsp;5.7\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e18.7\u0026thinsp;\u0026plusmn;\u0026thinsp;5.4\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e18.6\u0026thinsp;\u0026plusmn;\u0026thinsp;6.1\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e16.8\u0026thinsp;\u0026plusmn;\u0026thinsp;5.1\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e19.9\u0026thinsp;\u0026plusmn;\u0026thinsp;5.8\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAngle between screw axis and second metacarpal axis(degree)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e32.4\u0026thinsp;\u0026plusmn;\u0026thinsp;8.0\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e32.0\u0026thinsp;\u0026plusmn;\u0026thinsp;7.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e32.8\u0026thinsp;\u0026plusmn;\u0026thinsp;8.5\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e32.3\u0026thinsp;\u0026plusmn;\u0026thinsp;7.1\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e32.5\u0026thinsp;\u0026plusmn;\u0026thinsp;8.6\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLength of screw axis (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e1.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e1.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e1.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e2.0\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e1.8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMeasured values of the main parameters in lateral view\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eparameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eLeft side\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eRight side\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAngle between screw axis and first metacarpal axis(degree)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAbducted position (n\u0026thinsp;=\u0026thinsp;65)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e52.1\u0026thinsp;\u0026plusmn;\u0026thinsp;15.6\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e46.4\u0026thinsp;\u0026plusmn;\u0026thinsp;12.7\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e58.4\u0026thinsp;\u0026plusmn;\u0026thinsp;13.5\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e52.6\u0026thinsp;\u0026plusmn;\u0026thinsp;14.0\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e51.5\u0026thinsp;\u0026plusmn;\u0026thinsp;14.9\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eResting position (n\u0026thinsp;=\u0026thinsp;86)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e55.0\u0026thinsp;\u0026plusmn;\u0026thinsp;12.9\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e53.7\u0026thinsp;\u0026plusmn;\u0026thinsp;14.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e55.9\u0026thinsp;\u0026plusmn;\u0026thinsp;11.9\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e52.2\u0026thinsp;\u0026plusmn;\u0026thinsp;12.9\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e56.5\u0026thinsp;\u0026plusmn;\u0026thinsp;12.8\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAngle between screw axis and second metacarpal axis(degree)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e71.5\u0026thinsp;\u0026plusmn;\u0026thinsp;6.7\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e69.3\u0026thinsp;\u0026plusmn;\u0026thinsp;6.1\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e73.3\u0026thinsp;\u0026plusmn;\u0026thinsp;6.6\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e72.3\u0026thinsp;\u0026plusmn;\u0026thinsp;6.7\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e70.8\u0026thinsp;\u0026plusmn;\u0026thinsp;6.6\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLength of screw axis (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e2.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e2.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e2.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e2.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e2.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eskin thickness of scaphoid tubercle (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e0.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e0.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eentry point distance (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e1.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e1.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e1.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e1.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e1.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eIndependent samples t-test in anteroposterior view\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eparameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eLeft side Right side\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eMale Female\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003et values\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ep values\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003et values\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ep values\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAngle between screw axis and first metacarpal axis(degree)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAbducted position (n\u0026thinsp;=\u0026thinsp;65)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e1.315\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.193\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e2.958\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.176\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eResting position (n\u0026thinsp;=\u0026thinsp;86)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e1.436\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.324\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e2.156\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0267\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAngle between screw axis and second metacarpal axis(degree)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e0.815\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.418\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e-0.138\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.89\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLength of screw axis (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e-0.322\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.749\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e-4.714\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eIndependent samples t-test in lateral view\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eparameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eLeft side Right side\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eMale Female\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003et values\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ep values\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003et values\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003ep values\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAngle between screw axis and first metacarpal axis(degree)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAbducted position (n\u0026thinsp;=\u0026thinsp;65)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e1.307\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.196\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e1.044\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.298\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eResting position (n\u0026thinsp;=\u0026thinsp;86)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e1.742\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.054\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e2.076\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.023\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAngle between screw axis and second metacarpal axis(degree)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e3.013\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.004\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e-1.389\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.167\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLength of screw axis (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e0.013\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.989\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e-7.134\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e\u0026lt;\u0026thinsp;0.001\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eskin thickness of scaphoid tubercle (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e0.061\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.951\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e-2.495\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.014\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eentry point distance (cm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e-1.255\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e0.216\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e-3.569\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e0.002\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eAccurate implantation of the Herbert screw guide wire is crucial for surgery. Accurate implantation requires two conditions: 1. Determining the correct skin entry point; 2. The direction of the guide wire should align with the three-dimensional axis of the scaphoid. On the basis of this principle, we conducted measurement studies using X-rays and analyzed the entry point of the guide wire along with three-dimensional reference objects .\u003c/p\u003e \u003cp\u003eCurrently, there is no consensus on the optimal entry point and axis for percutaneous screw placement. Traditionally, the scaphoid tubercle is used as the entry point t\u003csup\u003e\u003cspan additionalcitationids=\"CR19 CR20\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e, with screws aligned centrally and maximized in length\u003csup\u003e\u003cspan additionalcitationids=\"CR23\" citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. Evan L. et al\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. suggested that the ideal starting point for the maximum screw axis is located 1.7 mm dorsal and 0.2 mm radial from the apex of the scaphoid tubercle.However, the volar retrograde approach presents challenges: a centrally placed entry point risks trapezial obstruction\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e and scaphotrapezial arthritis\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e,\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e, whereas the entry point is near the volar side of the scaphoid tuberosity, there is a risk of penetrating the volar cortex, and may cause a \"humpback\" deformity. While most authors agree that the screw should follow the scaphoid axis, the precise definition of this axis has not been clearly established in the literature. Menapace et al\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. used cadaveric measurements to define a safe zone for screw insertion that avoids vascular and articular damage, moving 15% of the contralateral scaphoid lateral length\u0026mdash;approximately 30% of its width\u0026mdash;posteriorly and distally from the volar side of the scaphoid tubercle. Meermans et al\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. reported that the transtrapezia technique can reliably place screws within the central one-third of the distal pole, but when they approach through the volar scaphoid tubercle, the screws are placed outside the central one-third of the distal pole. Similarly, Keith W et al\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. found that the volar approach involves approximately the central one-third of the distal pole. On the basis of previous studies, the central one-third of the distal pole on th scaphoid(approximately 30% of its width from the scaphoid tubercle) may represent a critical location for the volar approach, as it neither compromises the blood supply and cortex on the volar side nor damages the scaphotrapezial articular surface while maximizing the central placement of the screw. In this study, we chose the central one-third of the distal scaphoid as the entry point, and the target point of the screw axis was selected as the most proximal ulnar corner to achieve a greater distance,as described in the study by Dean et al\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. The longest screw length leads to the best bone purchase and greater biomechanical stability for increased construct strength\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. ​In this study, we devised a method to define the screw axis. Importantly, the \u0026ldquo;optimal\u0026rdquo; screw axis represents the ideal angle and direction without considering the orientation of the fracture line. When a volar approach is used for screw insertion, this axis can serve as a reference, allowing for appropriate adjustments on the basis of the specific clinical situation.\u003c/p\u003e \u003cp\u003ePrevious studies\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e,\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e have proposed marking the screw axis on the skin via intraoperative fluoroscopy in both the anteroposterior and lateral views to guide freehand insertion. This approach inevitably increases fluoroscopy exposure. Our measurements revealed that the scaphoid screw axis forms consistent angles with the first and second metacarpals, which can serve as anatomical references for the direction of the guidewire. In the lateral view, although the thumb position has minimal influence, the angle between the second metacarpal and the screw axis shows less variability (smaller standard deviation), making it a more stable reference (71.5\u0026deg;). Therefore, we recommend using the second metacarpal as a guide in the lateral view. In the anteroposterior view, owing to the limited visibility of the second metacarpal, the first metacarpal may serve as a more practical reference. However, its position must be considered: approximately 18.7\u0026deg; when it is at rest and 4.8\u0026deg; when abducted. Preoperative anteroposterior wrist radiographs can be taken with the thumb in abduction to assess whether the screw axis aligns parallel to the first metacarpal axis, thereby facilitating simplified intraoperative guidance.\u003c/p\u003e \u003cp\u003eOur study revealed that the guidewire entry point should not be placed directly over the scaphoid tubercle, as this may result in a volar deviation of the screw; instead, it should be positioned distal to the tubercle, with a distance of approximately 1.3 mm in females and approximately 1.5 mm in males. Initially, we hypothesized that there would be a positive correlation between skin thickness over the scaphoid tubercle and the distance to the guidewire entry point, on the basis of trigonometric principles. However, analysis revealed no significant correlation (p\u0026thinsp;=\u0026thinsp;0.559), suggesting that the entry point remains relatively constant regardless of subcutaneous thickness. This may be because the scaphoid tubercle is a bony protrusion with less subcutaneous fat, making it less likely to accumulate fat, which does not significantly affect the entry point. Nonetheless, potential bias and a limited sample size cannot be excluded.\u003c/p\u003e \u003cp\u003eThe length of the scaphoid long axis has long been a topic of discussion. Kong et al\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. measured 84 scaphoid specimens and reported that the length of the scaphoid in males was 27.92 mm, while in females was 26.47 mm. However, considering the requirements for subchondral screw placement, the recommended screw length is between 18 to 25 mm. Evan L. et al\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. found the optimal screw axis length to be 25\u0026ndash;28 mm using 3D models. Guo et al\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e., through 3D CT reconstruction of 30 pairs of wrist joints in Chinese, measured average scaphoid axis lengths of 29.3 mm in males and 26.6 mm in females. Similarly, Meermans et al\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. reported central axis lengths of 27.14 mm in males and 23.86 mm in females via 3D CT analysis. We measured the length of the scaphoid screw axis via two-dimensional radiographs. Owing to the projection angles, the lateral view length is longer than the anteroposterior view length. Clinically, to avoid the use of screws that are too short, the lateral view length is preferred as the reference. The length of the screw axis we defined on the lateral view(male 2.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3 cm, female 2.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2 cm) closely aligns with the scaphoid long axis values reported in previous studies. Considering the impact of the screw diameter, to avoid penetrating the joint surface, the actual length of the screw used should be shorter than the length of the screw axis by approximately 2-4mm\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e,\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eThis study has several limitations. While prior studies often used CT or cadaveric samples to determine optimal screw positioning\u0026mdash;with greater consistency and clarity\u0026mdash;these methods have limited clinical applicability. Our screw axis was defined via X-rays, as the orientation of the screw is guided by intraoperative fluoroscopy, our approach is more applicable in practice. Additionally, sample size and selection bias may have affected our findings, highlighting the need for larger-scale studies. Although this study focused primarily on proposing a novel anatomical reference for scaphoid screw insertion and validating its theoretical feasibility, we recognize its potential clinical value. Preliminary findings suggest that this method may offer more precise guidance for volar scaphoid fixation. In future work, we plan to conduct clinical trials in collaboration with surgeons to assess the safety, efficacy, and practical utility of this approach, aiming to facilitate its translation from theory to clinical practice.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eWe propose a novel reference method for guidewire placement in scaphoid fracture surgery. Specifically, we suggest that the guidewire can be inserted at an angle of 71.5\u0026deg; relative to the dorsum of the hand (aligned with the second metacarpal axis) in the lateral view, and at an angle of 18.7\u0026deg; relative to the lateral edge of the thumb (aligned with the first metacarpal axis) in the anteroposterior view when the thumb is at rest, or at an angle of 4.8\u0026deg; when the thumb is abducted. Preoperatively, obtaining a wrist radiograph with the thumb in abduction can help assess whether the lateral edge of the thumb is parallel to the intended screw axis, thereby providing a more stable reference for screw insertion. The skin entry point is approximately 1.48 cm from the scaphoid tubercle in male patients and 1.26 cm in female patients. The recommended screw length is 2.1\u0026ndash;2.3 cm for males and 1.8-2.0 cm for females\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eAuthor contributions\u003c/p\u003e\n\u003cp\u003eJingquan Guo, Bo Wu, and Fei Xiao were responsible for data measurement and study design. Jingquan Guo and Bo Wu conducted the literature review and contributed to manuscript drafting and revision. Qianwen Jia performed the statistical analysis. Keke Cheng and Tianrun Lei was involved in protocol development, gaining ethical approval. All authors reviewed and edited the manuscript and approved the final version of the manuscript\u003c/p\u003e\n\u003cp\u003eFunding\u003c/p\u003e\n\u003cp\u003eThe authors received no financial support for the research, authorship, and/or publication of this article.\u003c/p\u003e\n\u003cp\u003eData availability\u003c/p\u003e\n\u003cp\u003eThe data supporting this study\u0026apos;s findings are not publicly available due to sensitivity concerns but can be obtained from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003eEthics approval and consent to participate\u003c/p\u003e\n\u003cp\u003eEthical approval for this study was obtained from the Ethics Committee of the Wuhan Fourth Hospital(KY2024-192-01). All participants and/or their legal guardians provided informed consent prior to enrollment. To ensure privacy, no identifying information has been disclosed.\u003c/p\u003e\n\u003cp\u003eConsent for publication\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003eCompeting interests\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eLi NY, Dennison DG, Shin AY, Pulos NA. Update to Management of Acute Scaphoid Fractures. \u003cem\u003eJ Am Acad Orthop Surg\u003c/em\u003e. Published online June 16, 2023. doi:10.5435/JAAOS-D-22-01210\u003c/li\u003e\n\u003cli\u003eDias JJ, Ring D, Grewal R, Clementson M, Buijze GA, Ho PC. Acute scaphoid fractures: making decisions for treating a troublesome bone. \u003cem\u003eJ Hand Surg Eur Vol\u003c/em\u003e. 2022;47(1):73-79. doi:10.1177/17531934211053441\u003c/li\u003e\n\u003cli\u003eArsalan-Werner A, Sauerbier M, Mehling IM. Current concepts for the treatment of acute scaphoid fractures. \u003cem\u003eEur J Trauma Emerg Surg\u003c/em\u003e. 2016;42(1):3-10. doi:10.1007/s00068-015-0587-8\u003c/li\u003e\n\u003cli\u003eDias JJ. Should Acute Scaphoid Fractures Be Fixed?A Randomized Controlled Trial. \u003cem\u003eJ Bone Joint Surg Am\u003c/em\u003e. 2005;87(10):2160. doi:10.2106/JBJS.D.02305\u003c/li\u003e\n\u003cli\u003eAlnaeem H, Aldekhayel S, Kanevsky J, Neel OF. A Systematic Review and Meta-Analysis Examining the Differences Between Nonsurgical Management and Percutaneous Fixation of Minimally and Nondisplaced Scaphoid Fractures. \u003cem\u003eThe Journal of Hand Surgery\u003c/em\u003e. 2016;41(12):1135-1144.e1. doi:10.1016/j.jhsa.2016.08.023\u003c/li\u003e\n\u003cli\u003eDias J, Brealey S, Choudhary S, et al. Scaphoid Waist Internal Fixation for Fractures Trial (SWIFFT) protocol: a pragmatic multi-centre randomised controlled trial of cast treatment versus surgical fixation for the treatment of bi-cortical, minimally displaced fractures of the scaphoid waist in adults. \u003cem\u003eBMC Musculoskelet Disord\u003c/em\u003e. 2016;17(1):248. doi:10.1186/s12891-016-1107-7\u003c/li\u003e\n\u003cli\u003eHughes TB. Acute Scaphoid Waist Fracture in the Athlete. \u003cem\u003eClinics in Sports Medicine\u003c/em\u003e. 2020;39(2):339-351. doi:10.1016/j.csm.2019.12.007\u003c/li\u003e\n\u003cli\u003eWeller WJ, Thompson NB, Phillips SG, Calandruccio JH. Scaphoid Fractures in Athletes. \u003cem\u003eOrthopedic Clinics of North America\u003c/em\u003e. 2020;51(4):511-516. doi:10.1016/j.ocl.2020.07.001\u003c/li\u003e\n\u003cli\u003ePutnam J. Rethinking Scaphoid Fixation. \u003cem\u003eHand Clinics\u003c/em\u003e. 2023;39(4):597-604. doi:10.1016/j.hcl.2023.05.007\u003c/li\u003e\n\u003cli\u003eAcar B, Kose O, Kati YA, Egerci OF, Turan A, Yuksel HY. Comparison of volar versus dorsal screw fixation for scaphoid waist fractures: A finite element analysis. \u003cem\u003eOrthopaedics \u0026amp; Traumatology: Surgery \u0026amp; Research\u003c/em\u003e. 2018;104(7):1107-1113. doi:10.1016/j.otsr.2018.07.013\u003c/li\u003e\n\u003cli\u003eLi LX, Kedgley AE, Horwitz MD. A Review of the Use of 3D Printing Technology in Treatment of Scaphoid Fractures. \u003cem\u003eJ Hand Surg Asian-Pac Vol\u003c/em\u003e. 2023;28(01):22-33. doi:10.1142/S2424835523500042\u003c/li\u003e\n\u003cli\u003eYin H wei, Xu J, Xu W dong. 3-Dimensional Printing\u0026ndash;Assisted Percutaneous Fixation for Acute Scaphoid Fracture: 1-Shot Procedure. \u003cem\u003eThe Journal of Hand Surgery\u003c/em\u003e. 2017;42(4):301.e1-301.e5. doi:10.1016/j.jhsa.2017.01.017\u003c/li\u003e\n\u003cli\u003eLiu B, Wu F, Chen S, Jiang X, Tian W. Robot-assisted percutaneous scaphoid fracture fixation: a report of ten patients. \u003cem\u003eJ Hand Surg Eur Vol\u003c/em\u003e. 2019;44(7):685-691. doi:10.1177/1753193419848595\u003c/li\u003e\n\u003cli\u003eYi Z, Qi W, Chen S, Zhang Y, Liu B. A Novel Mini‐Invasive Technique of Arthroscopic‐Assisted Reduction and Robot‐Assisted Fixation for Trans‐Scaphoid Perilunate Fracture Dislocations. \u003cem\u003eOrthopaedic Surgery\u003c/em\u003e. 2023;15(4):1203-1209. doi:10.1111/os.13677\u003c/li\u003e\n\u003cli\u003eTen Berg PWL, Dobbe JGG, Brinkhorst ME, et al. Scaphoid screw fixation perpendicular to the fracture plane: Comparing volar and dorsal approaches. \u003cem\u003eOrthopaedics \u0026amp; Traumatology: Surgery \u0026amp; Research\u003c/em\u003e. 2018;104(1):109-113. doi:10.1016/j.otsr.2017.11.013\u003c/li\u003e\n\u003cli\u003eGuo Y, Ma W, Zlotolow D, Wang C, Tong D, Liu K. A Comparison Between Robotic-Assisted Scaphoid Screw Fixation and a Freehand Technique for Acute Scaphoid Fracture: A Randomized, Controlled Trial. \u003cem\u003eThe Journal of Hand Surgery\u003c/em\u003e. 2022;47(12):1172-1179. doi:10.1016/j.jhsa.2022.08.021\u003c/li\u003e\n\u003cli\u003eHohenberger GM, Berzins U, Bakota B, Holweg P, Clement B, Grechenig S. Scaphoid screw placement under minimal radiation exposure. \u003cem\u003eInjury\u003c/em\u003e. 2017;48:S47-S50. doi:10.1016/S0020-1383(17)30739-8\u003c/li\u003e\n\u003cli\u003eWei-yun K, Yong-qing XU, Yu-fei W, Shao-chun C, Zong-liang LIU, Xing-guo LI. Anatomic measurement of wrist scaphoid and its clini-cal significance. 中华创伤杂志英文版. 2009;12(1):41-44. doi:10.3760/cma.j.issn.1008-1275.2009.01.008\u003c/li\u003e\n\u003cli\u003eYin Y, Wang Z, Yi Z, Lim RQR, Chen S, Liu B. A comparative cadaveric study for percutaneous scaphoid fixation: robotic vs freehand. \u003cem\u003eInternational Orthopaedics (SICOT)\u003c/em\u003e. 2024;48(2):521-527. doi:10.1007/s00264-023-06013-3\u003c/li\u003e\n\u003cli\u003eAlmigdad A, Al-Zoubi A, Mustafa A, et al. A review of scaphoid fracture, treatment outcomes, and consequences. \u003cem\u003eInternational Orthopaedics (SICOT)\u003c/em\u003e. 2024;48(2):529-536. doi:10.1007/s00264-023-06014-2\u003c/li\u003e\n\u003cli\u003eLuria S, Lenart L, Lenart B, Peleg E, Kastelec M. Optimal Fixation of Oblique Scaphoid Fractures: A Cadaver Model. \u003cem\u003eThe Journal of Hand Surgery\u003c/em\u003e. 2012;37(7):1400-1404. doi:10.1016/j.jhsa.2012.04.021\u003c/li\u003e\n\u003cli\u003eLucenti L, Lutsky KF, Jones C, Kazarian E, Fletcher D, Beredjiklian PK. Antegrade Versus Retrograde Technique for Fixation of Scaphoid Waist Fractures: A Comparison of Screw Placement. \u003cem\u003eJnl Wrist Surg\u003c/em\u003e. 2020;09(01):034-038. doi:10.1055/s-0039-1698745\u003c/li\u003e\n\u003cli\u003eSoubeyrand M, Biau D, Mansour C, Mahjoub S, Molina V, Gagey O. Comparison of Percutaneous Dorsal Versus Volar Fixation of Scaphoid Waist Fractures Using a Computer Model in Cadavers. \u003cem\u003eThe Journal of Hand Surgery\u003c/em\u003e. 2009;34(10):1838-1844. doi:10.1016/j.jhsa.2009.07.012\u003c/li\u003e\n\u003cli\u003eChan KW, McAdams TR. Central screw placement in percutaneous screw scaphoid fixation: a cadaveric comparison of proximal and distal techniques. \u003cem\u003eThe Journal of Hand Surgery\u003c/em\u003e. 2004;29(1):74-79. doi:10.1016/j.jhsa.2003.09.002\u003c/li\u003e\n\u003cli\u003eLeventhal EL, Wolfe SW, Walsh EF, Crisco JJ. A Computational Approach to the \u0026ldquo;Optimal\u0026rdquo; Screw Axis Location and Orientation in the Scaphoid Bone. \u003cem\u003eThe Journal of Hand Surgery\u003c/em\u003e. 2009;34(4):677-684. doi:10.1016/j.jhsa.2009.01.011\u003c/li\u003e\n\u003cli\u003eKang KB, Kim HJ, Park JH, Shin YS. Comparison of Dorsal and Volar Percutaneous Approaches in Acute Scaphoid Fractures: A Meta-Analysis. Harhaus L, ed. \u003cem\u003ePLoS ONE\u003c/em\u003e. 2016;11(9):e0162779. doi:10.1371/journal.pone.0162779\u003c/li\u003e\n\u003cli\u003eMenapace KA, Larabee L, Arnoczky SP, Neginhal VS, Dass AG, Ross LM. Anatomic placement of the Herbert-Whipple screw in scaphoid fractures: A cadaver study. \u003cem\u003eThe Journal of Hand Surgery\u003c/em\u003e. 2001;26(5):883-892. doi:10.1053/jhsu.2001.27755\u003c/li\u003e\n\u003cli\u003eMeermans G, Van Glabbeek F, Braem MJ, Van Riet RP, Hubens G, Verstreken F. Comparison of Two Percutaneous Volar Approaches for Screw Fixation of Scaphoid Waist Fractures: Radiographic and Biomechanical Study of an Osteotomy-Simulated Model. \u003cem\u003eThe Journal of Bone and Joint Surgery\u003c/em\u003e. 2014;96(16):1369-1376. doi:10.2106/JBJS.L.01729\u003c/li\u003e\n\u003cli\u003eDean BJF, Riley ND, McCulloch ER, Lane JCE, Touzell AB, Graham AJ. A new acute scaphoid fracture assessment method: a reliability study of the \u0026lsquo;long axis\u0026rsquo; measurement. \u003cem\u003eBMC Musculoskelet Disord\u003c/em\u003e. 2018;19(1):310. doi:10.1186/s12891-018-2236-y\u003c/li\u003e\n\u003cli\u003eRamos-Marques N, Ferr\u0026atilde;o A, Morais B, Barreira M, Teixeira F. Percutaneous Scaphoid Fixation: Experience Value among Different Approaches. \u003cem\u003eJ Wrist Surg\u003c/em\u003e. 2021;10(01):023-026. doi:10.1055/s-0040-1716352\u003c/li\u003e\n\u003cli\u003eMeermans G, Verstreken F. Percutaneous Transtrapezial Fixation of Acute Scaphoid Fractures. \u003cem\u003eJ Hand Surg Eur Vol\u003c/em\u003e. 2008;33(6):791-796. doi:10.1177/1753193408092785\u003c/li\u003e\n\u003cli\u003eVerstreken F, Meermans G. Transtrapezial Approach for Fixation of Acute Scaphoid Fractures. \u003cem\u003eJBJS Essential Surgical Techniques\u003c/em\u003e. 2015;5(4):e29. doi:10.2106/JBJS.ST.O.00052\u003c/li\u003e\n\u003cli\u003eGuo Y, Tian GL. The length and position of the long axis of the scaphoid measured by analysis of three-dimensional reconstructions of computed tomography images. \u003cem\u003eJ Hand Surg Eur Vol\u003c/em\u003e. 2011;36(2):98-101. doi:10.1177/1753193410377837\u003c/li\u003e\n\u003cli\u003eMeermans G, Verstreken F. Influence of Screw Design, Sex, and Approach in Scaphoid Fracture Fixation. \u003cem\u003eClinical Orthopaedics \u0026amp; Related Research\u003c/em\u003e. 2012;470(6):1673-1681. doi:10.1007/s11999-011-2218-y\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"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":"scaphoid, positioning, percutaneous fixation, volar approach, screw axis","lastPublishedDoi":"10.21203/rs.3.rs-6740135/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6740135/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground:\u003c/h2\u003e \u003cp\u003eAccurate screw placement is critical for successful internal fixation of scaphoid fractures. However, during percutaneous Herbert screw fixation via the volar approach, there is currently no standardized anatomical reference for determining the entry point and screw axis. Traditional methods often rely on experience or intraoperative fluoroscopy, which can increase radiation exposure and reduce accuracy. This study aims to propose a novel reference method based on the angular relationship between the scaphoid screw axis and the first and second metacarpals, and to assess its anatomical consistency and potential clinical utility.\u003c/p\u003e\u003ch2\u003eMethods:\u003c/h2\u003e \u003cp\u003eA retrospective analysis was conducted on radiographs of healthy adults from 2021 to 2023, including anteroposterior and lateral wrist views. Two senior trainees and two experienced surgeons measured the imaging data. The measurements included the screw axis length, angles between the screw axis and metacarpal axes, skin thickness(the thickness beneath the skin of the scaphoid tubercle), and entry point distance(the vertical distance from the intersection of the extended screw axis with the palmar skin to the apex of the scaphoid tubercle). The influences of the thumb position, gender, and skin thickness on the screw axis orientation and entry point location were analyzed.\u003c/p\u003e\u003ch2\u003eResults:\u003c/h2\u003e \u003cp\u003eA total of 151 adults were analyzed, including 87 females (57.6%) and 64 males (42.4%) with an average age of 43.2\u0026thinsp;\u0026plusmn;\u0026thinsp;15.9 years. In the lateral view, the mean angle between the screw axis and the second metacarpal axis was 71.5\u0026deg; \u0026plusmn; 6.7\u0026deg;, with minimal variance, indicating high consistency across individuals. In the PA view, the angle between the screw axis and the first metacarpal axis varied with the thumb position: 4.8\u0026deg; \u0026plusmn; 2.8\u0026deg; in abduction versus 18.7\u0026deg; \u0026plusmn; 5.7\u0026deg; at rest. In some cases, the axes were nearly parallel in abduction. The screw axis length measured in the lateral view was closely aligned with that reported in previous anatomical studies(male 2.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3 cm vs female 2.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2 cm, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005). No significant correlation was found between subcutaneous thickness and entry point distance (r\u0026thinsp;=\u0026thinsp;0.048, p\u0026thinsp;=\u0026thinsp;0.559). Additionally, males had greater entry point distances (males 1.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3 cm vs females 1.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3 cm, p\u0026thinsp;\u0026lt;\u0026thinsp;0.005).\u003c/p\u003e\u003ch2\u003eConclusions:\u003c/h2\u003e \u003cp\u003eIn this study, we find a defined anatomical relationship between the scaphoid screw axis and the axes of the first and second metacarpals. Additionally, the guidewire entry point on the skin should be located distal to the scaphoid tubercle, with the distance varying by gender. The second metacarpal is recommended as a lateral view guide because of its stability and consistency, whereas the first metacarpal can be used in the PA view, particularly when the thumb is in abduction. Further clinical validation through prospective studies is warranted.\u003c/p\u003e","manuscriptTitle":"Measurement Study of the “Optimal” Screw Axis Location and Its Angles with the First and Second Metacarpals Based on X Imaging of the Scaphoid Bone","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-04 12:49:24","doi":"10.21203/rs.3.rs-6740135/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":"15d709a1-da1d-49eb-a8eb-c5d409f0bcff","owner":[],"postedDate":"June 4th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-08-07T16:23:29+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-04 12:49:24","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6740135","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6740135","identity":"rs-6740135","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}