Comparison of Accuracy Between Two Novel Portable Navigation Systems with Distinct Registration Methods for Lateral Decubitus Total Hip Arthroplasty

Comparison of Accuracy Between Two Novel Portable Navigation Systems with Distinct Registration Methods for Lateral Decubitus Total Hip Arthroplasty | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Comparison of Accuracy Between Two Novel Portable Navigation Systems with Distinct Registration Methods for Lateral Decubitus Total Hip Arthroplasty Yoshinobu Uchihara, Kenichiro Saito, Masakazu Okamoto, Hironori Sugimoto, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5280100/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 8 You are reading this latest preprint version Abstract Accurate cup placement is critical for ensuring satisfactory outcomes following total hip arthroplasty (THA). This study compared the accuracy of two new-generation computed tomography-free, imageless, and portable navigation systems, Navbit Sprint and Naviswiss, in the lateral decubitus position. A retrospective review of 145 patients who underwent primary THA between November 2020 and April 2024 was conducted, with 84 patients in the Navbit Sprint group and 61 patients in the Naviswiss group. The mean absolute navigation error for radiographic inclination (RI) was 3.5 ± 2.3° for Navbit Sprint and 2.5 ± 2.1° for Naviswiss, with a significant difference favouring Naviswiss ( P = 0.0061). For radiographic anteversion (RA), the mean absolute navigation error was 4.3 ± 3.7° for Navbit Sprint and 3.2 ± 2.6° for Naviswiss, with no significant difference ( P = 0.06). The percentage of RI outliers with an absolute navigation error > 5° was significantly higher in the Navbit Sprint group (20%) compared to the Naviswiss group (4.9%), while no significant differences were observed for RA outliers. Both systems demonstrated high accuracy; however, Naviswiss showed superior precision in RI, suggesting that the anatomical landmark registration method is more reliable than the table tilt method employed by Navbit Sprint. Health sciences/Medical research/Outcomes research Physical sciences/Engineering/Biomedical engineering total hip arthroplasty portable navigation acetabular cup orientation computer-assisted surgery Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Incorrect cup alignment during total hip arthroplasty (THA) can result in decreased range of motion and dislocation in the short term, and polyethylene wear and loosening in the long term 12 . Various intraoperative support tools have been developed for accurate cup placement. Although computed tomography (CT)-based navigation and robotic arm-assisted surgery support systems are accurate, they are expensive and not easily available at all institutions 345 . The use of CT-free portable navigation, which is less expensive than CT-based navigation and robotic-arm surgical support systems, has become more widespread in recent years. Currently, various types of CT-free imageless portable navigation systems are available, including an accelerometer-based portable navigation system (HipAlign, OrthAlign, Aliso Viejo, CA, USA), a mini-optical portable hip navigation system (Intellijoint HIP, Intellijoint Surgical, Inc., Waterloo, ON, Canada), a new accelerometer-based portable hip navigation system combined with an infrared stereo camera (Naviswiss AG, Brugg, Switzerland), and an augmented reality-based portable hip system (AR-Hip, Zimmer Biomet Japan, Tokyo, Japan) 367891011121314 . These portable navigation systems have reported relatively good cup placement accuracy following THA in the supine position 131516 . However, first-generation portable navigation systems, such as HipAlign and Intellijoint HIP, have been reported to be less accurate than second-generation navigation systems, such as Naviswiss and AR-Hip, for THA in the lateral decubitus position 717 . These differences in accuracy were attributed to the registration method. The second-generation portable navigation systems employ a registration method that identifies anatomical landmarks of the bilateral anterior superior iliac spine (ASIS). However, a new inertial portable hip navigation system (Navbit Sprint, Navbit Pty Ltd., Sydney, Australia), which employs a new registration method (table tilt method) that does not require the identification of anatomical landmarks, is now available 181920 . This system can reportedly be used in both the supine and lateral decubitus positions and has good accuracy 1920 . To our knowledge, no studies have compared the cup placement accuracy of Navbit Sprint with that of second-generation portable navigation devices. Thus, our study aimed to compare the cup placement accuracy of Navbit Sprint and Naviswiss in THA in the lateral decubitus position. Methods Patients The study was approved by the Institutional Review Board of Nara Medical University (approval number: 3802). The requirement for informed consent was waived owing to the retrospective nature of the study. All methods were performed in accordance with relevant guidelines and regulations. We retrospectively reviewed the records of patients who underwent primary THA in the lateral decubitus position with Navbit Sprint or Naviswiss between November 2020 and April 2024 at two institutions, Nara Medical University and Yoshimoto Orthopaedic and Surgical Hospital. The inclusion criteria were primary THA performed using the Naviswiss or Navbit Sprint with a modified Watson–Jones approach 21 in the lateral decubitus position. The exclusion criteria were as follows: (1) missing postoperative CT data, (2) difficulty in assessing the accuracy of postoperative cup placement, (3) intraoperative navigation failure that resulted in the discontinuation, (4) postoperative pin loosening during THA, (5) Crowe grade 2 or higher deformity, and (6) revision hip arthroplasty. Finally, 84 patients in the Navbit Sprint group and 61 in the Naviswiss group were analysed. The demographic data of the patients are presented in Table 1 . Table 1 Patient's demographics characteristics Navbit Sprint group Naviswiss group P -value (n = 84) (n = 61) Age (years) 69 ± 11 64 ± 9.9 0.006 ** Sex (male/female) 122/72 15/46 0.134 * Body mass index (kg/m 2 ) 24 ± 4.2 24 ± 4.2 0.855 ** Diagnosis (OA/ONFH/Other) 71/10/3 47/12/2 0.437 *** Stem type (cemented stem/cementless stem) 84/0 6/55 < 0.001 * Data are shown as mean ± standard deviation or number. OA: osteoarthritis, ONFH: osteonecrosis of femoral head *: Fisher's exact test, **: Two-tailed t-test, ***: Chi-square test Preoperative planning and surgical procedure Preoperative CT was performed in the supine position, and CT image data were imported into the preoperative planning software ZedHip (Lexi, Tokyo, Japan) to determine the position and angle of cup placement and stem type for each patient. The target placement angles for the cups were determined according to Murray's definition 22 , with a radiographic inclination (RI) of 40° and radiographic anteversion (RA) between 15° and 25°. To avoid iliopsoas impingement 23 , the cup was fine-tuned to ensure it did not protrude beyond the anterior labral limb. For cup placement, the patient was placed in the supine position, and the plane parallel to the operating table passing through both the superior anterior iliac spines (ASIS) was defined as the functional pelvic plane (FPP). Surgery was performed in the lateral recumbent position using a modified Watson–Jones approach. Four orthopaedic specialists (Y.U., K.S., M.O., and H.S.) with 10–22 years of experience, performed all the surgeries, and one surgeon (Y.U.) supervised all the operations. Two or three screws were inserted in all the cases to secure the cups. All the patients were allowed full weight bearing immediately after surgery, and gait training was performed. Portable navigation selection Portable navigation was selected according to the implant manufacturer, which was determined in the preoperative planning phase. First, the stem was determined, and cups produced by the manufacturer were used. All the patients who used SQRUM (Kyocera, Osaka, Japan) used Naviswiss; 53 patients used the Initia stem (Kyocera, Osaka, Japan) and eight patients used the SC stem (Kyocera, Osaka, Japan). All the patients with R3 (Smith & Nephew, Watford, United Kingdom) used Navbit sprint and cemented POLARSTEM (Smith & Nephew, Watford, United Kingdom). Naviswiss has been available since April 2020. Navbit Sprint has been available since April (limited release) and June (general release) 2023. Navbit Sprint Registration and Cup Installation Angle Measurement (Fig. ) Navbit Sprint Registration and Cup Installation Angle Measurement (Fig. 1 ) Navbit Sprint is a single-use computer-aided surgical navigation system with a rate gyro and accelerometer that generates real-time information on inclination and anteversion and uses a novel pelvic reference plane registration method 1819 . The flip technique was used to perform the registration in the supine position before the incision, and surgery was performed in the lateral decubitus position 14 24 . The patient was positioned supine, centred, and parallel to the long axis of the operating table. Two fixation pins (3.2 mm in diameter) were inserted over the patient's iliac crest, and the device mount was placed on the fixation pins. A gravity vector representing the functional anterior-posterior axis was automatically obtained when the Navbit Sprint was placed on the device mount. When the operating table was tilted 10° to the left and right, Navbit Sprint acquired two additional gravity vectors at each tilted position. The vertical vector to these two vectors is the roll axis, which represents the patient's functional vertical axis and creates a functional coordinate system (FPP) for calculating the inclination and anteversion. At the time of cup placement, the cup placement angle was measured by attaching the Navbit Sprint to a device mount attached to the cup impactor. Naviswiss registration and cup installation angle measurement (Fig. ) Naviswiss registration and cup installation angle measurement (Fig. 2 ) Naviswiss is an imageless portable navigation system that uses a handheld infrared stereo camera with a built-in accelerometer and an angular rate meter. The flip technique was used to perform the registration in the supine position before the incision, and the surgery was performed in the lateral decubitus position 1424 . In the supine position, two fixation pins (3.0 mm in diameter) were inserted over the iliac crest to secure the P-tag. The bilateral ASIS was palpated simultaneously with a pelvic calliper with M-tags attached to determine FPP. The two tags were read using an infrared stereo camera to determine the axis of gravity. During cup placement, the P-tag attached to the pelvis and the M-tag attached to the cup impactor were simultaneously read by an infrared stereo camera to measure the cup placement angle. Measurement All patients underwent CT from the pelvis to the knee in the supine position during the first postoperative week. The three-dimensional CT template software, ZedHip, was used to measure the cup placement angle. The installation angles (RI and RA) were measured by superimposing the cup template and the actual cup. Primary outcome: accuracy of portable navigation The navigation error (the difference between the angle measured postoperatively and the angle displayed on the intraoperative navigation screen) was measured. The absolute values of the navigation errors were calculated for each case and the mean ± standard deviation (SD) was used for data analysis. The percentage of cases with an absolute navigation error within 5° and 10° were measured. Univariate analysis was performed to analyse the correlation between the body mass index (BMI) and the absolute value of navigation errors. Secondary outcome: surgical outcome Complications (dislocation, intraoperative fracture, surgical site infection, and nerve palsy) were also recorded. Statistical analysis Based on previous studies, a difference of 2° was considered clinically significant and the sample size was calculated 7 . A power analysis using the Student's t-test (two-sided with an alpha level of 0.05) indicated that 48 cases per group were needed to achieve 90% statistical power to detect a significant group difference. Navigation errors between the two navigations were compared using t-tests and reported along with 95% confidence intervals (CIs) for intergroup differences. Fisher's exact probability test was used to compare the percentage of cases in which the absolute value error of the navigation error was within 5° and 10°. A P -value < 5% was considered significant. Spearman's rank correlation coefficient was used to investigate the correlation between the BMI and cup placement angle navigation errors. Analysis was conducted using R version 4.4.0 (R Foundation for Statistical Computing, Vienna, Austria; 2024-04-24). Results The absolute navigation error in RI was 3.5 ± 2.3° and 2.5 ± 2.1° in the Navbit Sprint and Naviswiss groups, respectively, which was significantly greater in the Navbit Sprint group (95% CI 0.30° to 1.77°, P = 0.0061) (Table 2 and Fig. 3 ). Absolute RA navigation errors were 4.3 ± 3.7° and 3.2 ± 2.6° for the Navbit Sprint and Naviswiss groups, respectively, which were not significantly different between the two groups (95% CI − 0.04° to 1.93°, P = 0.06) (Table 2 and Fig. 4 ). The percentage of outliers with an absolute RI navigation error > 5° was 20% and 4.9% in the Navbit Sprint and Naviswiss groups, respectively, which was significantly more in the Navbit Sprint group ( P = 0.013). The percentage of outliers with RA navigation errors with an absolute value > 5° was 26.2% and 19.7% in the Navbit Sprint and Naviswiss groups, respectively, with no significant difference ( P = 0.43). The percentage of outliers with an absolute RI navigation error > 10° was 0% in both groups. The percentage of outliers with RA navigation errors with an absolute value > 10° was 8.3% and 1.6% in the Navbit Sprint and Naviswiss groups, respectively, with no significant difference ( P = 0.14) (Table 3 ). Univariate analysis revealed no correlation between the BMI and absolute navigation errors for RA and RI in either group (Navbit Sprint group RI: r = 0.055, P = 0.62; RA: r = − 0.043, P = 0.70; Naviswiss group RI: r = 0.012, P = 0.93, RA: r = 0.022, P = 0.87). No complications (dislocation, intraoperative fracture, surgical site infection, or nerve palsy) were observed in any of the patients in either group. Table 2 Absolute values of the navigation error Navbit Sprint group Naviswiss group 95% CI P-value Radiographic inclination (°) 3.5 ± 2.3 2.5 ± 2.1 0.30 to 1.77 0.0061 Radiographic anteversion (°) 4.3 ± 3.7 3.2 ± 2.6 –0.04 to 1.93 0.06 Student's t test, CI: confidence interval Table 3 Proportion of outliers Navbit Sprint group Naviswiss group P -value > 5° in RI (%) 20 4.9 0.013 > 5° in RA (%) 26.2 19.7 0.43 > 10° in RI (%) 0 0 - > 10° in RA (%) 8.3 1.6 0.14 Fisher's exact test, RI: radiographic inclination, RA: radiographic anteversion Discussion We compared the accuracy of cup placement for navigation in THA in the lateral decubitus position between the Navbit Sprint, which uses a new pelvic reference plane registration method (table tilt method), and Naviswiss, which registers the pelvic reference plane by palpating the bilateral ASIS. To our knowledge, this is the first study to compare the accuracy of portable navigation using the table tilt method in lateral THA with that of second-generation portable navigation using palpation of the ASIS to register the pelvic reference plane. Joshua et al. 19 compared the cup placement angles between Navbit Sprint and CT-free stationary navigation ONS (the Stryker Navigation System mobile tower, in combination with the OrthoMap Versatile Hip Software), and reported absolute navigation error RI and RA values of 2.1 ± 2.3° and 2.4 ± 2.1° for Navbit Sprint, and 3.0 ± 2.8° and 4.5 ± 3.2° for ONS, respectively, with Navbit Sprint having a significantly smaller error; however, their findings were based on comparison with non-portable navigation. Tanino et al. 20 reported absolute Navbit Sprint RI and RA navigation errors in lateral THA of 2.8 ± 2.6° and 3.9 ± 2.9°, respectively, with significantly smaller errors in the RI compared with RA; however, this study also did not compare the absolute values with those using portable navigation. In this study, the absolute navigation errors for RI and RA, respectively, were 3.5 ± 2.3° and 4.3 ± 3.7° in the Navbit Sprint and 2.5 ± 2.1° and 4.3 ± 3.7° in the Naviswiss groups. The Naviswiss group had significantly fewer navigation errors in the RI and significantly fewer outliers, indicating greater accuracy of the Naviswiss method of palpating the ASIS than the table tilt method. The Navbit Sprint table tilt method assumes that the body axis during supine registration is parallel to the vertical axis of the bed and that the bilateral ASIS heights are aligned. This assumption may have been incorrect as we ensured this visually in our study. In THA, cup placement should be performed based on the FPP with respect to the operating table in the supine position 25 . Hence, THA in the lateral decubitus position should replicate supine FPP. If registration is performed in the lateral decubitus position, the cup placement angle is based on the assumption that the pelvis is correctly fixed in the positional fixation device at the time of registration. The pelvis is reported to be disjointed when set up in a pelvic fixator; moreover, tilting is most prone to displacement 2627 . Zhu et al. reported that pelvic tilt in the lateral decubitus position is widely distributed in the range from 25° posterior to 20° anterior 28 . Pelvic obliquity affects inclination, whereas pelvic tilt affects anteversion. Therefore, in first-generation navigation devices, including HipAlign and Intellijoint HIP, where registration is performed in the lateral decubitus position, navigation accuracy is expected to decrease, especially in anteversion. Tsukada et al 7 . reported absolute HipAlign RI and RA navigation errors of 4.6 ± 3.1° and 6.4 ± 4.2°, respectively, while Tetsunaga et al 3 . reported absolute HipAlign RI and RA navigation errors of 4.1 ± 3.7° and 6.8 ± 4.8°, respectively. Second-generation navigation, including Naviswiss and AR-Hip, allows the FPP to be registered in the supine position, even with THA in the lateral decubitus position. Thus, it is possible to register bilateral ASIS anatomical landmarks in the supine position and then flip them to the supine position for THA in the lateral THA position (flip technique) 14 . This eliminated errors attributed to pelvic misalignment when changing positions to the lateral decubitus position. Naito et al. 14 compared the absolute values of navigation errors between lateral and supine registration in Naviswiss and reported absolute values of 3.1 ± 2.1° for RI and 4.2 ± 2.8° for RA in the lateral decubitus group and 2.3 ± 2.0° for RA and 3.1 ± 2.4° for RI in the supine group; the accuracy was significantly improved when the patients were registered in the supine position and the flip technique was used. Kurosaka et al 11 . compared the absolute navigation error values between AR-Hip, a second-generation navigation system, and HipAlign, a first-generation navigation system, and reported 3 ± 2° for RI and 2 ± 2° for RA in the AR-Hip group and 3 ± 2° for RA and 5 ± 4° for RI in the HipAlign group. Although no significant difference was observed in RI, AR-Hip exhibited a significantly smaller error in RA; thus, the second generation demonstrated greater accuracy than the first-generation navigation devices. Navbit Sprint can use the flip technique to register the FPP in the supine position and then reposition the patient in the lateral decubitus position. FPP is determined using the table tilt method, which does not use anatomical landmarks such as bilateral ASIS. Jobe et al 18 . stated that navigation that requires accurate identification of bony landmarks, such as both the ASIS, can result in greater navigation errors in patients with obesity; thus, the table tilt method can be considered in these cases. However, neither Navbit Sprint nor Naviswiss demonstrated a correlation between the BMI and navigation errors in this study, which may be attributed to the fact that only 9.7% of the patients in our study had a BMI ≥ 30 kg/m 2 . Simple portable navigation has the advantage of being less expensive and more portable than large stationary CT-based navigation and robotic arm-assisted surgery system 17 . The widespread use of CT-free imageless portable navigation systems that exhibit high cup placement accuracy, low cost, and portability may be considered in the future. This study had several limitations study. First, this was a retrospective study and not a randomised study, which may have led to selection bias and limited the generalisability of the results. To remedy this problem, future randomised controlled trials should be conducted to minimise bias and increase the reliability of the results. Second, the stems used in the Navbit Sprint and Naviswiss groups differed: all patients in the Navbit group used cemented stems, whereas only 12% of patients in the Naviswiss group did. In this study, the stem was first determined and a cup produced by the manufacturer was used, and each navigation was tied to each cup. Bone quality may have differed between the two groups, and the iliac crest pins may have loosened in patients with poor bone quality, affecting navigation accuracy; however, by excluding cases with loose iliac crest pins, the effect was minimised. Third, the screw was inserted after the cup and measured using the navigation device; thus, the possibility of cup movement could not be eliminated in this process. Fourth, the effects of the learning curve were not considered. In conclusion, this study is the first to compare cup placement accuracy in lateral THA between Navbit Sprint, which uses a new pelvic reference plane registration method (table tilt method), and Naviswiss, which registers the pelvic reference plane by palpating the anatomical landmarks. Two different types of imageless portable navigation devices achieved high cup placement accuracy; however, Naviswiss, which employs palpation of anatomical landmarks, demonstrated higher accuracy in inclination. Declarations Acknowledgements We would like to thank Editage (www.editage.com) for English language editing. Author contributions Y.U. collected the data, performed the statistical analysis, and drafted the manuscript. K.S. and M.O. contributed to the interpretation of the data. Y.U., K.S., M.O., H.S., and Y.A. performed the surgeries. Y.Y., Y.M., and Y.I. critically reviewed the manuscript. Y.T. supervised the manuscript preparation. All authors read and approved the final version of the manuscript. Data availability statement The datasets during and/or analyzed during the current study available from the corresponding author on reasonable request. Competing Interests Statement The authors declare no competing interests. References Lewinnek, G. E., Lewis, J. L., Tarr, R., Compere, C. L. & Zimmerman, J. R. Dislocations after total hip-replacement arthroplasties. J. Bone Joint Surg. Am. 60 , 217–220 (1978). Sugano, N., Takao, M., Sakai, T., Nishii, T. & Miki, H. 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Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 16 Nov, 2024 Reviewers agreed at journal 14 Nov, 2024 Reviewers agreed at journal 14 Nov, 2024 Reviewers invited by journal 13 Nov, 2024 Editor assigned by journal 13 Nov, 2024 Editor invited by journal 07 Nov, 2024 Submission checks completed at journal 04 Nov, 2024 First submitted to journal 17 Oct, 2024 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. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5280100","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":378269659,"identity":"f48c9a46-3c84-4b39-83b3-e2e2c74026b2","order_by":0,"name":"Yoshinobu Uchihara","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA40lEQVRIiWNgGAWjYJACZgaDAyDqGJjHxk68FrY0BoYEIMVMlBYGkBYeM7AWBkJaDA7wGH4uKLgjb95+5tuDjz+2yfMxMzB++JiDV4ux9AyDZ4ZzzuRuN5yRcNuwjZmBWXLmNjxa7r8xY+YxOMw4gyF3mzRPwm1GoBY2Zl58Wg7wgLXYz+B/8wykxZ5oLYkzJHLYQFoSCWqRPMBWLA3UkjxD4pmZ5Iy028ltzIzNeP3Cd4B542eeP4dtZ/AnP5P4YHPbdn5788EPH/FoUTiAKcbYgFs9EMjjlx4Fo2AUjIJRAAQAK6RK1yE4HvgAAAAASUVORK5CYII=","orcid":"","institution":"Nara Medical University","correspondingAuthor":true,"prefix":"","firstName":"Yoshinobu","middleName":"","lastName":"Uchihara","suffix":""},{"id":378269660,"identity":"889ea791-81c7-453c-be8b-ea47445b6afd","order_by":1,"name":"Kenichiro Saito","email":"","orcid":"","institution":"Nara Medical University","correspondingAuthor":false,"prefix":"","firstName":"Kenichiro","middleName":"","lastName":"Saito","suffix":""},{"id":378269661,"identity":"c1c56b1c-494f-4f53-811a-8247a9e7ad85","order_by":2,"name":"Masakazu Okamoto","email":"","orcid":"","institution":"Nara Medical University","correspondingAuthor":false,"prefix":"","firstName":"Masakazu","middleName":"","lastName":"Okamoto","suffix":""},{"id":378269662,"identity":"b43fe5ad-25be-49fa-b24a-56ddbb57e5d5","order_by":3,"name":"Hironori Sugimoto","email":"","orcid":"","institution":"Nara Medical University","correspondingAuthor":false,"prefix":"","firstName":"Hironori","middleName":"","lastName":"Sugimoto","suffix":""},{"id":378269663,"identity":"b2346e76-c718-48da-8eae-207432a1ad67","order_by":4,"name":"Yushi Ando","email":"","orcid":"","institution":"Yoshimoto Orthopaedic and Surgical Hospital","correspondingAuthor":false,"prefix":"","firstName":"Yushi","middleName":"","lastName":"Ando","suffix":""},{"id":378269664,"identity":"f96a8ad7-fc24-461b-8724-4f520e035bab","order_by":5,"name":"Yudai Yano","email":"","orcid":"","institution":"Nara Medical University","correspondingAuthor":false,"prefix":"","firstName":"Yudai","middleName":"","lastName":"Yano","suffix":""},{"id":378269665,"identity":"ef4ced73-1872-40fd-9f1d-373d525c18e7","order_by":6,"name":"Yusuke Miura","email":"","orcid":"","institution":"Nara Medical University","correspondingAuthor":false,"prefix":"","firstName":"Yusuke","middleName":"","lastName":"Miura","suffix":""},{"id":378269666,"identity":"72cddfb2-5de4-446c-833e-1d77790b934e","order_by":7,"name":"Yusuke Inagaki","email":"","orcid":"","institution":"Nara Medical University","correspondingAuthor":false,"prefix":"","firstName":"Yusuke","middleName":"","lastName":"Inagaki","suffix":""},{"id":378269667,"identity":"d6ecf5a4-a956-44f2-8605-e49ece5161fe","order_by":8,"name":"Yasuhito Tanaka","email":"","orcid":"","institution":"Nara Medical University","correspondingAuthor":false,"prefix":"","firstName":"Yasuhito","middleName":"","lastName":"Tanaka","suffix":""}],"badges":[],"createdAt":"2024-10-17 06:23:09","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5280100/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5280100/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":70385307,"identity":"6ccca6f4-7aae-4467-a35e-dfd55f53d83c","added_by":"auto","created_at":"2024-12-02 17:05:57","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":325159,"visible":true,"origin":"","legend":"\u003cp\u003eNavbit Sprint: Inertial portable hip navigation system.\u003c/p\u003e\n\u003cp\u003ea. The patient is positioned supine, centred, and parallel to the long axis of the operating table. Two fixation pins are inserted over the patient's iliac crest and the device is mounted on the fixation pins (arrow).\u003c/p\u003e\n\u003cp\u003eb. Table tilt method: When Navbit Sprint is placed on the device mount, a gravity vector representing the functional anterior–posterior axis is automatically obtained (b1). When the operating table is tilted 10° to the left (b2) and 10° to the right (b3), Navbit Sprint acquires two additional gravity vectors at each tilt position, thereby creating the functional pelvic plane (FPP).\u003c/p\u003e\n\u003cp\u003ec. Measurement: When the cup is mounted, the Navbit Sprint is attached to the device mount attached to the cup impactor to measure the cup installation angle. Radiographic inclination (RI) and radiographic anteversion (RA) are displayed in the navigation system.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5280100/v1/ba3314ff1d564088b3d9b142.png"},{"id":70385311,"identity":"50dcb9ea-3230-4e07-9522-0a8a90ce580b","added_by":"auto","created_at":"2024-12-02 17:06:08","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":378175,"visible":true,"origin":"","legend":"\u003cp\u003eNaviswiss: Accelerometer-based portable hip navigation system combined with an infrared stereo camera.\u003c/p\u003e\n\u003cp\u003ea. Registration: Two fixation pins are inserted over the iliac crest in the supine position to secure the P-tag (solid arrow). The bilateral anterior superior iliac spine (ASIS) is palpated simultaneously with pelvic calipers with an M-tag (dashed arrow) attached. The two tags are read using an infrared stereo camera to register the functional pelvic plane (FPP).\u003c/p\u003e\n\u003cp\u003eb. Measurement: When the cup is applied, the P-tag (solid arrow) attached to the pelvis and the M-tag (dashed arrow) attached to the cup impactor are simultaneously read by an infrared stereo camera to measure the cup placement angle, and the radiographic inclination (RI) and radiographic anteversion (RA) are displayed in the navigation system.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5280100/v1/b9da1b0e9fe903f3130c8c7b.png"},{"id":70385309,"identity":"0cb8d129-a3cc-405e-9231-2bfce86df422","added_by":"auto","created_at":"2024-12-02 17:06:02","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":46511,"visible":true,"origin":"","legend":"\u003cp\u003eThe navigation error (the difference between the angle measured postoperatively and the angle displayed on the intraoperative navigation screen) in radiographic inclination (RI) in all the patients.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5280100/v1/70886902603b1b3319072ee5.png"},{"id":70385304,"identity":"3a8d36c1-6857-445f-b95e-7862fcaa1a93","added_by":"auto","created_at":"2024-12-02 17:05:47","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":52089,"visible":true,"origin":"","legend":"\u003cp\u003eThe navigation error (the difference between the angle measured postoperatively and the angle displayed on the intraoperative navigation screen) in radiographic anteversion (RA) in all patients.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5280100/v1/ffabf81e3e50e85327c1c0f0.png"},{"id":70387131,"identity":"42643442-dca0-43f3-a2c2-0f4cbd596f0b","added_by":"auto","created_at":"2024-12-02 17:23:50","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1454670,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5280100/v1/75758db4-bd2c-4d4c-b2ac-9b93eda09854.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Comparison of Accuracy Between Two Novel Portable Navigation Systems with Distinct Registration Methods for Lateral Decubitus Total Hip Arthroplasty","fulltext":[{"header":"Introduction","content":"\u003cp\u003eIncorrect cup alignment during total hip arthroplasty (THA) can result in decreased range of motion and dislocation in the short term, and polyethylene wear and loosening in the long term\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. Various intraoperative support tools have been developed for accurate cup placement. Although computed tomography (CT)-based navigation and robotic arm-assisted surgery support systems are accurate, they are expensive and not easily available at all institutions\u003csup\u003e345\u003c/sup\u003e. The use of CT-free portable navigation, which is less expensive than CT-based navigation and robotic-arm surgical support systems, has become more widespread in recent years. Currently, various types of CT-free imageless portable navigation systems are available, including an accelerometer-based portable navigation system (HipAlign, OrthAlign, Aliso Viejo, CA, USA), a mini-optical portable hip navigation system (Intellijoint HIP, Intellijoint Surgical, Inc., Waterloo, ON, Canada), a new accelerometer-based portable hip navigation system combined with an infrared stereo camera (Naviswiss AG, Brugg, Switzerland), and an augmented reality-based portable hip system (AR-Hip, Zimmer Biomet Japan, Tokyo, Japan)\u003csup\u003e367891011121314\u003c/sup\u003e. These portable navigation systems have reported relatively good cup placement accuracy following THA in the supine position\u003csup\u003e131516\u003c/sup\u003e. However, first-generation portable navigation systems, such as HipAlign and Intellijoint HIP, have been reported to be less accurate than second-generation navigation systems, such as Naviswiss and AR-Hip, for THA in the lateral decubitus position\u003csup\u003e717\u003c/sup\u003e. These differences in accuracy were attributed to the registration method.\u003c/p\u003e \u003cp\u003eThe second-generation portable navigation systems employ a registration method that identifies anatomical landmarks of the bilateral anterior superior iliac spine (ASIS). However, a new inertial portable hip navigation system (Navbit Sprint, Navbit Pty Ltd., Sydney, Australia), which employs a new registration method (table tilt method) that does not require the identification of anatomical landmarks, is now available\u003csup\u003e181920\u003c/sup\u003e. This system can reportedly be used in both the supine and lateral decubitus positions and has good accuracy\u003csup\u003e1920\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eTo our knowledge, no studies have compared the cup placement accuracy of Navbit Sprint with that of second-generation portable navigation devices. Thus, our study aimed to compare the cup placement accuracy of Navbit Sprint and Naviswiss in THA in the lateral decubitus position.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003ePatients\u003c/h2\u003e \u003cp\u003e The study was approved by the Institutional Review Board of Nara Medical University (approval number: 3802). The requirement for informed consent was waived owing to the retrospective nature of the study. All methods were performed in accordance with relevant guidelines and regulations.\u003c/p\u003e \u003cp\u003eWe retrospectively reviewed the records of patients who underwent primary THA in the lateral decubitus position with Navbit Sprint or Naviswiss between November 2020 and April 2024 at two institutions, Nara Medical University and Yoshimoto Orthopaedic and Surgical Hospital.\u003c/p\u003e \u003cp\u003eThe inclusion criteria were primary THA performed using the Naviswiss or Navbit Sprint with a modified Watson\u0026ndash;Jones approach\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e in the lateral decubitus position. The exclusion criteria were as follows: (1) missing postoperative CT data, (2) difficulty in assessing the accuracy of postoperative cup placement, (3) intraoperative navigation failure that resulted in the discontinuation, (4) postoperative pin loosening during THA, (5) Crowe grade 2 or higher deformity, and (6) revision hip arthroplasty. Finally, 84 patients in the Navbit Sprint group and 61 in the Naviswiss group were analysed. The demographic data of the patients are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\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\u003ePatient's demographics characteristics\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNavbit Sprint group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNaviswiss\u003c/p\u003e \u003cp\u003egroup\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;84)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;61)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge (years)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e69\u0026thinsp;\u0026plusmn;\u0026thinsp;11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e64\u0026thinsp;\u0026plusmn;\u0026thinsp;9.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.006\u0026nbsp;**\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex (male/female)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e122/72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15/46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.134\u0026nbsp;*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBody mass index (kg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e24\u0026thinsp;\u0026plusmn;\u0026thinsp;4.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e24\u0026thinsp;\u0026plusmn;\u0026thinsp;4.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.855\u0026nbsp;**\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDiagnosis (OA/ONFH/Other)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e71/10/3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e47/12/2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.437\u0026nbsp;***\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStem type (cemented stem/cementless stem)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e84/0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6/55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u0026nbsp;*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c4\" namest=\"c1\"\u003e \u003cp\u003eData are shown as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation or number.\u003c/p\u003e \u003cp\u003eOA: osteoarthritis, ONFH: osteonecrosis of femoral head\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003e*: Fisher's exact test, **: Two-tailed t-test, ***: Chi-square test\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003ePreoperative planning and surgical procedure\u003c/h3\u003e\n\u003cp\u003ePreoperative CT was performed in the supine position, and CT image data were imported into the preoperative planning software ZedHip (Lexi, Tokyo, Japan) to determine the position and angle of cup placement and stem type for each patient. The target placement angles for the cups were determined according to Murray's definition\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e, with a radiographic inclination (RI) of 40\u0026deg; and radiographic anteversion (RA) between 15\u0026deg; and 25\u0026deg;. To avoid iliopsoas impingement\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e, the cup was fine-tuned to ensure it did not protrude beyond the anterior labral limb. For cup placement, the patient was placed in the supine position, and the plane parallel to the operating table passing through both the superior anterior iliac spines (ASIS) was defined as the functional pelvic plane (FPP).\u003c/p\u003e \u003cp\u003eSurgery was performed in the lateral recumbent position using a modified Watson\u0026ndash;Jones approach. Four orthopaedic specialists (Y.U., K.S., M.O., and H.S.) with 10\u0026ndash;22 years of experience, performed all the surgeries, and one surgeon (Y.U.) supervised all the operations. Two or three screws were inserted in all the cases to secure the cups. All the patients were allowed full weight bearing immediately after surgery, and gait training was performed.\u003c/p\u003e\n\u003ch3\u003ePortable navigation selection\u003c/h3\u003e\n\u003cp\u003ePortable navigation was selected according to the implant manufacturer, which was determined in the preoperative planning phase. First, the stem was determined, and cups produced by the manufacturer were used. All the patients who used SQRUM (Kyocera, Osaka, Japan) used Naviswiss; 53 patients used the Initia stem (Kyocera, Osaka, Japan) and eight patients used the SC stem (Kyocera, Osaka, Japan). All the patients with R3 (Smith \u0026amp; Nephew, Watford, United Kingdom) used Navbit sprint and cemented POLARSTEM (Smith \u0026amp; Nephew, Watford, United Kingdom). Naviswiss has been available since April 2020. Navbit Sprint has been available since April (limited release) and June (general release) 2023.\u003c/p\u003e\n\u003ch3\u003eNavbit Sprint Registration and Cup Installation Angle Measurement (Fig. )\u003c/h3\u003e\n\u003cdiv class=\"Heading\"\u003eNavbit Sprint Registration and Cup Installation Angle Measurement (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e1\u003c/span\u003e)\u003c/div\u003e \u003cp\u003eNavbit Sprint is a single-use computer-aided surgical navigation system with a rate gyro and accelerometer that generates real-time information on inclination and anteversion and uses a novel pelvic reference plane registration method\u003csup\u003e1819\u003c/sup\u003e. The flip technique was used to perform the registration in the supine position before the incision, and surgery was performed in the lateral decubitus position\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. The patient was positioned supine, centred, and parallel to the long axis of the operating table. Two fixation pins (3.2 mm in diameter) were inserted over the patient's iliac crest, and the device mount was placed on the fixation pins.\u003c/p\u003e \u003cp\u003eA gravity vector representing the functional anterior-posterior axis was automatically obtained when the Navbit Sprint was placed on the device mount. When the operating table was tilted 10\u0026deg; to the left and right, Navbit Sprint acquired two additional gravity vectors at each tilted position. The vertical vector to these two vectors is the roll axis, which represents the patient's functional vertical axis and creates a functional coordinate system (FPP) for calculating the inclination and anteversion. At the time of cup placement, the cup placement angle was measured by attaching the Navbit Sprint to a device mount attached to the cup impactor.\u003c/p\u003e\n\u003ch3\u003eNaviswiss registration and cup installation angle measurement (Fig. )\u003c/h3\u003e\n\u003cdiv class=\"Heading\"\u003eNaviswiss registration and cup installation angle measurement (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e2\u003c/span\u003e)\u003c/div\u003e \u003cp\u003eNaviswiss is an imageless portable navigation system that uses a handheld infrared stereo camera with a built-in accelerometer and an angular rate meter. The flip technique was used to perform the registration in the supine position before the incision, and the surgery was performed in the lateral decubitus position\u003csup\u003e1424\u003c/sup\u003e. In the supine position, two fixation pins (3.0 mm in diameter) were inserted over the iliac crest to secure the P-tag. The bilateral ASIS was palpated simultaneously with a pelvic calliper with M-tags attached to determine FPP. The two tags were read using an infrared stereo camera to determine the axis of gravity. During cup placement, the P-tag attached to the pelvis and the M-tag attached to the cup impactor were simultaneously read by an infrared stereo camera to measure the cup placement angle.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eMeasurement\u003c/h2\u003e \u003cp\u003eAll patients underwent CT from the pelvis to the knee in the supine position during the first postoperative week. The three-dimensional CT template software, ZedHip, was used to measure the cup placement angle. The installation angles (RI and RA) were measured by superimposing the cup template and the actual cup.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003ePrimary outcome: accuracy of portable navigation\u003c/h3\u003e\n\u003cp\u003eThe navigation error (the difference between the angle measured postoperatively and the angle displayed on the intraoperative navigation screen) was measured. The absolute values of the navigation errors were calculated for each case and the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD) was used for data analysis. The percentage of cases with an absolute navigation error within 5\u0026deg; and 10\u0026deg; were measured. Univariate analysis was performed to analyse the correlation between the body mass index (BMI) and the absolute value of navigation errors.\u003c/p\u003e\n\u003ch3\u003eSecondary outcome: surgical outcome\u003c/h3\u003e\n\u003cp\u003eComplications (dislocation, intraoperative fracture, surgical site infection, and nerve palsy) were also recorded.\u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eBased on previous studies, a difference of 2\u0026deg; was considered clinically significant and the sample size was calculated\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. A power analysis using the Student's t-test (two-sided with an alpha level of 0.05) indicated that 48 cases per group were needed to achieve 90% statistical power to detect a significant group difference.\u003c/p\u003e \u003cp\u003eNavigation errors between the two navigations were compared using t-tests and reported along with 95% confidence intervals (CIs) for intergroup differences. Fisher's exact probability test was used to compare the percentage of cases in which the absolute value error of the navigation error was within 5\u0026deg; and 10\u0026deg;. A \u003cem\u003eP\u003c/em\u003e-value\u0026thinsp;\u003cem\u003e\u0026lt;\u003c/em\u003e\u0026thinsp;5% was considered significant. Spearman's rank correlation coefficient was used to investigate the correlation between the BMI and cup placement angle navigation errors. Analysis was conducted using R version 4.4.0 (R Foundation for Statistical Computing, Vienna, Austria; 2024-04-24).\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eThe absolute navigation error in RI was 3.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3\u0026deg; and 2.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2.1\u0026deg; in the Navbit Sprint and Naviswiss groups, respectively, which was significantly greater in the Navbit Sprint group (95% CI 0.30\u0026deg; to 1.77\u0026deg;, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.0061) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Absolute RA navigation errors were 4.3\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7\u0026deg; and 3.2\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6\u0026deg; for the Navbit Sprint and Naviswiss groups, respectively, which were not significantly different between the two groups (95% CI \u0026minus;\u0026thinsp;0.04\u0026deg; to 1.93\u0026deg;, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.06) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The percentage of outliers with an absolute RI navigation error\u0026thinsp;\u0026gt;\u0026thinsp;5\u0026deg; was 20% and 4.9% in the Navbit Sprint and Naviswiss groups, respectively, which was significantly more in the Navbit Sprint group (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.013). The percentage of outliers with RA navigation errors with an absolute value\u0026thinsp;\u0026gt;\u0026thinsp;5\u0026deg; was 26.2% and 19.7% in the Navbit Sprint and Naviswiss groups, respectively, with no significant difference (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.43). The percentage of outliers with an absolute RI navigation error\u0026thinsp;\u0026gt;\u0026thinsp;10\u0026deg; was 0% in both groups. The percentage of outliers with RA navigation errors with an absolute value\u0026thinsp;\u0026gt;\u0026thinsp;10\u0026deg; was 8.3% and 1.6% in the Navbit Sprint and Naviswiss groups, respectively, with no significant difference (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.14) (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Univariate analysis revealed no correlation between the BMI and absolute navigation errors for RA and RI in either group (Navbit Sprint group RI: r\u0026thinsp;=\u0026thinsp;0.055, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.62; RA: r = \u0026minus;\u0026thinsp;0.043, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.70; Naviswiss group RI: r\u0026thinsp;=\u0026thinsp;0.012, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.93, RA: r\u0026thinsp;=\u0026thinsp;0.022, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.87). No complications (dislocation, intraoperative fracture, surgical site infection, or nerve palsy) were observed in any of the patients in either group.\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\u003eAbsolute values of the navigation error\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNavbit Sprint group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNaviswiss group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e95% CI\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRadiographic inclination (\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.30 to 1.77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.0061\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRadiographic anteversion (\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.3\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.2\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026ndash;0.04 to 1.93\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.06\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eStudent's t test, CI: confidence interval\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\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\u003eProportion of outliers\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNavbit Sprint group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNaviswiss group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;5\u0026deg; in RI (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.013\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;5\u0026deg; in RA (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e26.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e19.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.43\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;10\u0026deg; in RI (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026gt;\u0026thinsp;10\u0026deg; in RA (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.14\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c3\" namest=\"c1\"\u003e \u003cp\u003eFisher's exact test, RI: radiographic inclination, RA: radiographic anteversion\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eWe compared the accuracy of cup placement for navigation in THA in the lateral decubitus position between the Navbit Sprint, which uses a new pelvic reference plane registration method (table tilt method), and Naviswiss, which registers the pelvic reference plane by palpating the bilateral ASIS. To our knowledge, this is the first study to compare the accuracy of portable navigation using the table tilt method in lateral THA with that of second-generation portable navigation using palpation of the ASIS to register the pelvic reference plane.\u003c/p\u003e \u003cp\u003eJoshua et al.\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e compared the cup placement angles between Navbit Sprint and CT-free stationary navigation ONS (the Stryker Navigation System mobile tower, in combination with the OrthoMap Versatile Hip Software), and reported absolute navigation error RI and RA values of 2.1\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3\u0026deg; and 2.4\u0026thinsp;\u0026plusmn;\u0026thinsp;2.1\u0026deg; for Navbit Sprint, and 3.0\u0026thinsp;\u0026plusmn;\u0026thinsp;2.8\u0026deg; and 4.5\u0026thinsp;\u0026plusmn;\u0026thinsp;3.2\u0026deg; for ONS, respectively, with Navbit Sprint having a significantly smaller error; however, their findings were based on comparison with non-portable navigation. Tanino et al.\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e reported absolute Navbit Sprint RI and RA navigation errors in lateral THA of 2.8\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6\u0026deg; and 3.9\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9\u0026deg;, respectively, with significantly smaller errors in the RI compared with RA; however, this study also did not compare the absolute values with those using portable navigation.\u003c/p\u003e \u003cp\u003eIn this study, the absolute navigation errors for RI and RA, respectively, were 3.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3\u0026deg; and 4.3\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7\u0026deg; in the Navbit Sprint and 2.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2.1\u0026deg; and 4.3\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7\u0026deg; in the Naviswiss groups. The Naviswiss group had significantly fewer navigation errors in the RI and significantly fewer outliers, indicating greater accuracy of the Naviswiss method of palpating the ASIS than the table tilt method. The Navbit Sprint table tilt method assumes that the body axis during supine registration is parallel to the vertical axis of the bed and that the bilateral ASIS heights are aligned. This assumption may have been incorrect as we ensured this visually in our study.\u003c/p\u003e \u003cp\u003eIn THA, cup placement should be performed based on the FPP with respect to the operating table in the supine position\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. Hence, THA in the lateral decubitus position should replicate supine FPP. If registration is performed in the lateral decubitus position, the cup placement angle is based on the assumption that the pelvis is correctly fixed in the positional fixation device at the time of registration. The pelvis is reported to be disjointed when set up in a pelvic fixator; moreover, tilting is most prone to displacement\u003csup\u003e2627\u003c/sup\u003e. Zhu et al. reported that pelvic tilt in the lateral decubitus position is widely distributed in the range from 25\u0026deg; posterior to 20\u0026deg; anterior\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. Pelvic obliquity affects inclination, whereas pelvic tilt affects anteversion. Therefore, in first-generation navigation devices, including HipAlign and Intellijoint HIP, where registration is performed in the lateral decubitus position, navigation accuracy is expected to decrease, especially in anteversion. Tsukada et al\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. reported absolute HipAlign RI and RA navigation errors of 4.6\u0026thinsp;\u0026plusmn;\u0026thinsp;3.1\u0026deg; and 6.4\u0026thinsp;\u0026plusmn;\u0026thinsp;4.2\u0026deg;, respectively, while Tetsunaga et al\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. reported absolute HipAlign RI and RA navigation errors of 4.1\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7\u0026deg; and 6.8\u0026thinsp;\u0026plusmn;\u0026thinsp;4.8\u0026deg;, respectively.\u003c/p\u003e \u003cp\u003eSecond-generation navigation, including Naviswiss and AR-Hip, allows the FPP to be registered in the supine position, even with THA in the lateral decubitus position. Thus, it is possible to register bilateral ASIS anatomical landmarks in the supine position and then flip them to the supine position for THA in the lateral THA position (flip technique)\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. This eliminated errors attributed to pelvic misalignment when changing positions to the lateral decubitus position. Naito et al.\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e compared the absolute values of navigation errors between lateral and supine registration in Naviswiss and reported absolute values of 3.1\u0026thinsp;\u0026plusmn;\u0026thinsp;2.1\u0026deg; for RI and 4.2\u0026thinsp;\u0026plusmn;\u0026thinsp;2.8\u0026deg; for RA in the lateral decubitus group and 2.3\u0026thinsp;\u0026plusmn;\u0026thinsp;2.0\u0026deg; for RA and 3.1\u0026thinsp;\u0026plusmn;\u0026thinsp;2.4\u0026deg; for RI in the supine group; the accuracy was significantly improved when the patients were registered in the supine position and the flip technique was used. Kurosaka et al\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. compared the absolute navigation error values between AR-Hip, a second-generation navigation system, and HipAlign, a first-generation navigation system, and reported 3\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg; for RI and 2\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg; for RA in the AR-Hip group and 3\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg; for RA and 5\u0026thinsp;\u0026plusmn;\u0026thinsp;4\u0026deg; for RI in the HipAlign group. Although no significant difference was observed in RI, AR-Hip exhibited a significantly smaller error in RA; thus, the second generation demonstrated greater accuracy than the first-generation navigation devices.\u003c/p\u003e \u003cp\u003eNavbit Sprint can use the flip technique to register the FPP in the supine position and then reposition the patient in the lateral decubitus position. FPP is determined using the table tilt method, which does not use anatomical landmarks such as bilateral ASIS. Jobe et al\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. stated that navigation that requires accurate identification of bony landmarks, such as both the ASIS, can result in greater navigation errors in patients with obesity; thus, the table tilt method can be considered in these cases. However, neither Navbit Sprint nor Naviswiss demonstrated a correlation between the BMI and navigation errors in this study, which may be attributed to the fact that only 9.7% of the patients in our study had a BMI\u0026thinsp;\u0026ge;\u0026thinsp;30 kg/m\u003csup\u003e2\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eSimple portable navigation has the advantage of being less expensive and more portable than large stationary CT-based navigation and robotic arm-assisted surgery system\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. The widespread use of CT-free imageless portable navigation systems that exhibit high cup placement accuracy, low cost, and portability may be considered in the future.\u003c/p\u003e \u003cp\u003eThis study had several limitations study. First, this was a retrospective study and not a randomised study, which may have led to selection bias and limited the generalisability of the results. To remedy this problem, future randomised controlled trials should be conducted to minimise bias and increase the reliability of the results. Second, the stems used in the Navbit Sprint and Naviswiss groups differed: all patients in the Navbit group used cemented stems, whereas only 12% of patients in the Naviswiss group did. In this study, the stem was first determined and a cup produced by the manufacturer was used, and each navigation was tied to each cup. Bone quality may have differed between the two groups, and the iliac crest pins may have loosened in patients with poor bone quality, affecting navigation accuracy; however, by excluding cases with loose iliac crest pins, the effect was minimised. Third, the screw was inserted after the cup and measured using the navigation device; thus, the possibility of cup movement could not be eliminated in this process. Fourth, the effects of the learning curve were not considered.\u003c/p\u003e \u003cp\u003eIn conclusion, this study is the first to compare cup placement accuracy in lateral THA between Navbit Sprint, which uses a new pelvic reference plane registration method (table tilt method), and Naviswiss, which registers the pelvic reference plane by palpating the anatomical landmarks. Two different types of imageless portable navigation devices achieved high cup placement accuracy; however, Naviswiss, which employs palpation of anatomical landmarks, demonstrated higher accuracy in inclination.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to thank Editage (www.editage.com) for English language editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eY.U. collected the data, performed the statistical analysis, and drafted the manuscript. K.S. and M.O. contributed to the interpretation of the data. Y.U., K.S., M.O., H.S., and Y.A. performed the surgeries. Y.Y., Y.M., and Y.I. critically reviewed the manuscript. Y.T. supervised the manuscript preparation. All authors read and approved the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets during and/or analyzed during the current study available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eLewinnek, G. E., Lewis, J. L., Tarr, R., Compere, C. L. \u0026amp; Zimmerman, J. R. Dislocations after total hip-replacement arthroplasties. \u003cem\u003eJ. Bone Joint Surg. Am.\u003c/em\u003e \u003cb\u003e60\u003c/b\u003e, 217\u0026ndash;220 (1978).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSugano, N., Takao, M., Sakai, T., Nishii, T. \u0026amp; Miki, H. 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Res.\u003c/em\u003e \u003cb\u003e468\u003c/b\u003e, 571\u0026ndash;575 (2010).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"total hip arthroplasty, portable navigation, acetabular cup orientation, computer-assisted surgery","lastPublishedDoi":"10.21203/rs.3.rs-5280100/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5280100/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAccurate cup placement is critical for ensuring satisfactory outcomes following total hip arthroplasty (THA). This study compared the accuracy of two new-generation computed tomography-free, imageless, and portable navigation systems, Navbit Sprint and Naviswiss, in the lateral decubitus position. A retrospective review of 145 patients who underwent primary THA between November 2020 and April 2024 was conducted, with 84 patients in the Navbit Sprint group and 61 patients in the Naviswiss group. The mean absolute navigation error for radiographic inclination (RI) was 3.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2.3\u0026deg; for Navbit Sprint and 2.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2.1\u0026deg; for Naviswiss, with a significant difference favouring Naviswiss (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.0061). For radiographic anteversion (RA), the mean absolute navigation error was 4.3\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7\u0026deg; for Navbit Sprint and 3.2\u0026thinsp;\u0026plusmn;\u0026thinsp;2.6\u0026deg; for Naviswiss, with no significant difference (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.06). The percentage of RI outliers with an absolute navigation error\u0026thinsp;\u0026gt;\u0026thinsp;5\u0026deg; was significantly higher in the Navbit Sprint group (20%) compared to the Naviswiss group (4.9%), while no significant differences were observed for RA outliers. Both systems demonstrated high accuracy; however, Naviswiss showed superior precision in RI, suggesting that the anatomical landmark registration method is more reliable than the table tilt method employed by Navbit Sprint.\u003c/p\u003e","manuscriptTitle":"Comparison of Accuracy Between Two Novel Portable Navigation Systems with Distinct Registration Methods for Lateral Decubitus Total Hip Arthroplasty","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-12-02 16:10:43","doi":"10.21203/rs.3.rs-5280100/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2024-11-17T02:00:09+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"326791892416368276630127098424364425421","date":"2024-11-15T02:53:20+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"158223500509102068201567298813843496974","date":"2024-11-14T17:54:51+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-11-14T02:17:24+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-11-14T02:15:17+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2024-11-07T12:41:30+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-11-04T07:16:54+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2024-10-17T06:08:51+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"b176222b-1ae9-4181-8b59-210a747a802f","owner":[],"postedDate":"December 2nd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":40282368,"name":"Health sciences/Medical research/Outcomes research"},{"id":40282369,"name":"Physical sciences/Engineering/Biomedical engineering"}],"tags":[],"updatedAt":"2024-12-02T16:10:43+00:00","versionOfRecord":[],"versionCreatedAt":"2024-12-02 16:10:43","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5280100","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5280100","identity":"rs-5280100","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}