Changes in kinematic behavior and collateral ligament strain after medially stabilized TKA using a novel Intraoperative Navigation Platform: a cadaveric study

Changes in kinematic behavior and collateral ligament strain after medially stabilized TKA using a novel Intraoperative Navigation Platform: a cadaveric study | 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 Changes in kinematic behavior and collateral ligament strain after medially stabilized TKA using a novel Intraoperative Navigation Platform: a cadaveric study Arne Van de Vyver, Orçun Taylan, Geert Peersman, Bialy Maciej, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6876936/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 Objectives: This study aimed to analyze to what extent a novel intraoperative navigation platform (Next-AR, Medacta) for total knee arthroplasty (TKA) allows to restore the native knee joint kinematics and strains in the medial collateral ligament (MCL) and lateral collateral ligament (LCL) throughout a squatting motion. Material and methods: Computed tomography (CT) scans of 6 native cadaver legs were used to design patient-specific guides. Bony landmarks and virtual single-line collateral ligaments were identified to acquire real-time intraoperative feedback on bone resection, implant alignment, tibiofemoral kinematics, and collateral ligament elongations using the Next-AR system. The specimens were subjected to squatting (35°-100°) motion using a physiological ex vivo knee simulator while maintaining a constant vertical ankle load of 110N through active quadriceps and bilateral hamstring controls. Subsequently, each knee underwent a medially-stabilized TKA (Medacta) with mechanical alignment technique and was retested under the same conditions as in their native state. The tibiofemoral and patellofemoral kinematics, along with collateral ligament strains, were computed from 3D marker trajectories using a six-camera optical system (Vicon). MCL and LCL insertions—ant, mid, and post bundles—were identified in relation to bone-pin markers using a wand. Results: Both native and post-operative conditions exhibited similar tibial valgus orientation (Root Mean Square Error (RMSE = 1.7°), patellar flexion (RMSE = 1.2°), abduction (RMSE = 0.5°), and rotation (RMSE = 0.4°) during squatting (p > 0.13). However, a significant difference was observed in tibial internal rotation between 35° and 62° (p 0.05). Contrary, LCL strain in all bundles (RMSE < 4.6%) differed significantly from mid to deep flexion in both conditions (p < 0.048). Conclusion: The novel intraoperative Next-AR system not only targets planned knee alignment but also aids in restoring native knee kinematics and elongation of the collateral ligaments through real-time feedback. Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Total knee arthroplasty (TKA) is a highly successful treatment for end-stage knee osteoarthritis and aims to restore pre-operative biomechanical- and kinematic properties mimicking the native knee joint. [ 1 , 2 ] Despite the overall success of TKA, a notable proportion of patients may remain dissatisfied post-surgery. Factors contributing to dissatisfaction include joint pain, reduced motion, instability, implant failure, poor soft tissue balance, and implant choice. [ 3 ] Advancements have been made in various aspects of TKA technologies to address dissatisfaction and alignment outliers, advancements have been made in various aspects of TKA technology. These include improvements in implant design and materials, image-based cutting guides, patient-specific implants, and computer-navigated surgery. [ 4 ] Navigation systems, whether imageless or image-based (CT or MRI) assist in achieving desired alignment goal, thus recreating optimal ligament tension and knee kinematics. There is ongoing debate about which type of implant design is superior. Currently, the most popular designs are cruciate retaining (CR) and posterior stabilized (PS) implants. Additionally, medially stabilized implants have been introduced to mimic natural knee kinematics, such as femoral rollback and ligament behavior, more closely. [ 5 , 6 ] Previous studies have shown that none of the ligament bundles of MCL and LCL showed isometric behavior after TKA, regardless of implant design. Achieving symmetrical flexion- and extension will, therefore, not guarantee optimal soft tissue balance. [ 7 , 17 , 20 ] Preservation of ligament tension during knee motion is challenging in TKA and new technologies are emerging to cope with these challenges. Medacta International has recently introduced the Next-Ar Navigation Platform (Medacta International, Strada Regina, Switzerland), a wireless single use tracking system mounted directly onto bone. This system provides real-time intraoperative feedback by using preoperative CT to identify bony landmarks and ligamentous insertions. Consequently, the surgeon can monitor bone resection, knee alignment, tibiofemoral kinematics and collateral ligament elongation. Precise adjustments can be made during the procedure. This study aims to assess the efficacy of a novel Next-AR system for medially stabilized TKA in restoring native joint kinematics and collateral ligament strains in a cadaveric set-up Materials and Methods Preoperative specimen imaging and surgical planning Seven fresh-frozen full cadaveric legs (age = 80.8 ± 9.59, three unilateral female donors, one unilateral and two bilateral male donors, height = 165 cm ± 0.5, and weight = 66 kg ± 10.5) were obtained following ethical approval from the local Ethics Committee (NH019-2021-04-01). The specimens were screened for potential lower limb disorder and prior surgical intervention. Following, bicortical bone pins were fixed into the femur, tibia, and patella to rigidly attach dedicated rigid marker frames, each containing four reflective spheres. Each specimen's computer tomography (CT) scans (Siemens Somatom Force, Siemens Healthcare, Erlangen, Germany) were then acquired in full extension with a slice thickness of 0.6 mm. Segmentation software (Mimics 25.0, Materialise, Leuven, Belgium) was used based on the well-established algorithm to identify the location of spherical markers and the required anatomical landmarks from CT images. [ 8 , 9 ] These identified landmarks were used to define bone-specific joint coordinate systems for the femur, tibia, and patella based on the Grood and Suntay convention[ 10 ]. Additional CT scans of the hip, knee, and ankle of each subject were acquired conforming to the MyKnee protocol (Medacta International SA, Castel San Pietro, Switzerland) to design patient-specific surgical guides [ 11 ], including the proprietary holders for the Next-AR motion trackers (a camera and a receiver unit), for mechanical alignment technique and to generate input parameters, such as 3D models of the bones, bony landmarks, and insertions of the collateral ligaments [ 12 , 13 ]. Subsequently, these input parameters were exported into the Next-AR Navigation Platform. Specimen preparation Each specimen was thawed 24 hours before testing, with a single freezing-thawing cycle. The femur and the tibia were resected 32 cm proximally and 28 cm distally to the knee joint line, respectively. Care was taken to preserve the joint capsule, ligaments and tendons while removing the skin and subcutaneous tissue around the knee joint. The exposed quadriceps tendon was clamped within a custom metal clamp, and suture loops (2x2 non-absorbable polyester braided suture wire; Cardioxyl, Peters Surgical, Bobigny Cedex, France) were passed through the medial and lateral hamstring tendons. The tibia and femur were embedded in metal containers using an acrylic resin (Struers, Ballerup, Denmark) while positioning the femur in 6° of valgus. Preoperative Testing The native specimens were mounted into an Oxford-based physiological ex-vivo knee simulator and subjected to passive flexion (10°–120°) and squatting (35°–100°), respectively. During passive flexion, the femur pot was rigidly attached to the knee simulator, with the tibia and the tendons left unconstrained. Subsequently, the tibia was manually cycled from maximum extension to maximum flexion angle. For squatting motion, the tibial pot was mounted to the ankle assembly. The suture loops fixed to the medial and collateral hamstring tendons were connected to the medial and lateral electromechanical hamstring actuators through a steel pulley and cable system. The quadriceps clamp was affixed to the quadriceps electromechanical actuators directly through a clevis and pin assembly. During squatting motion, a computer-controlled electromechanical actuator was used to apply a dynamic load to the quadriceps tendon. while computer-controlled electromechanical actuators individually applied a constant 50 N load to the medial and lateral hamstrings. In conjunction with simultaneously controlling the vertical translation of the ankle assembly to facilitate flexion and extension, the controller ensured a constant vertical ankle load of 110 N throughout the squatting motion. Each motion was performed in triplicate, and the trajectories of the retro-reflective spheres attached to the specimens were recorded using six infrared cameras (Vero v1.3, Vicon Motion Systems, Oxford, UK) operating at 100 Hz. After performing functional motion tests, the insertions of the medial collateral ligament (MCL) and lateral collateral ligament (LCL) were carefully exposed. Subsequently, the coordinates of each ligament bundle (anterior, middle, and posterior) were recorded using a dedicated optical motion capture system's wand, equipped with five spherical retro-reflective markers. Moreover, for precise and physiologically accurate computation of Vicon-based ligament elongations, while using a shortest path calculation, the tibial plateau edge was defined as a 3D spline using Mimics (Materialise, Leuven, Belgium). It is noteworthy that such measures were not required for the LCL, given its absence of anatomical wrapping around the tibial plateau. Surgical technique and postoperative testing Two knees were excluded from pre- and postoperative squatting motion analysis due to early quadriceps tendon failure after surgery. All eight knees were included in pre- and postoperative passive flexion analysis. After testing the native knees, each knee underwent a cemented cruciate-sacrificing total knee arthroplasty (medially stabilized, GMK Sphere, Medacta International) using a mechanical alignment technique. First, the patient-specific surgical guides were rigidly fixed to the femur and tibia with bone pins. Following, the Next-AR motion tracker unit—a camera and a receiver—were rigidly attached to detachable device housings mounted on the guides (Fig. 1 A). To minimize potential discrepancies between the positions reported by the motion tracker unit and the actual bone positions, fine-tuning correction was performed throughout the registration process. [ 13 ] Subsequently, the surgical guides were removed while maintaining the camera and receiver units fixed. Before resecting the bones, the absolute change in the collateral ligament lengths to an initial value (extended knee (0°-10°)) was determined and tibiofemoral kinematics were documented during passive flexion-extension. The cutting jigs were affixed to the femur first, followed by the tibia, and then sequential bone resections were carried out. Subsequently, a cemented TKA was implanted. Postoperative collateral ligament elongations and tibiofemoral kinematics were digitally recorded during passive flexion-extension cycles. These recordings were then compared to the preoperatively measured reference curves. No additional cuts or ligament releases were performed during this experiment. Data processing The trajectories of reflective markers captured with the Vicon optical motion capture system were processed using motion tracking software (Nexus 2.9, Vicon, Oxford, UK). Based hereon, the tibio- and patellofemoral kinematics and the elongation of each collateral ligament bundle (anterior, middle and posterior) were computed. For the latter, the method described by Marai et al. was used [ 16 ]. The kinematic variables, along with the collateral ligament elongations, were downsampled and interpolated at 1° intervals of flexion, all within the common knee flexion range shared by all specimens: 10° to 100° for passive flexion and 35° to 10° for squatting. Furthermore, the absolute difference between the output measured at the initial reference knee flexion angle (10° for passive flexion and 35° for squatting) and the value at each subsequent angle was used to compute the engineering strain of collateral ligament bundles throughout the motion. The initial knee flexion angle was considered 0% and all subsequent measurements were expressed to this initial value using a custom code in Matlab (R2022a, Mathworks Inc, Natick, MA, USA). Statistical analysis A linear mixed model was used to compare measured outputs derived from native and postoperative conditions, such as tibio- and patellofemoral kinematics and collateral ligament strains. Subsequently, Tukey's HSD post hoc test was performed for pairwise comparisons at each knee flexion angle. The residuals were assessed for normality, multicollinearity, and heteroscedasticity. No transformations were required as assumptions were met. The Cohen’s d effect size (ES, large ≥ 0.8 and small ≤ 0.2) was computed for the statistically different groups. Additionally, the mean Root-Mean-Square Error (RMSE) for the entire motion was calculated to quantify the difference between the mean curves of the conditions. All statistical analyses were performed in R (R-Studio Version 2023.03.1, Boston, MA), and the significance level was determined at p 0.508, mean Root-Mean-Square Error (RMSE) = 0.763°): an initial increase in varus until mid-flexion, followed by a subsequent decrease throughout the remaining range of motion (Fig. 2 A). For tibial internal-external rotation, the native and postoperative conditions showed a tendency towards increased internal rotation (Fig. 2 C). Nonetheless, a significant difference between the native and postoperative conditions was observed after 81° of knee flexion angle (0.028 < p < 0.048, RMSE = 2.862°, 0.765 0.713). In terms of AP translation of the tibia knee center with respect to the femur knee center, significant differences were observed between 52° and 120° (0.001 < p < 0.045, RMSE = 5.639mm, 1.014 3.854). During squatting, both native and postoperative conditions consistently maintained varus orientation across the entire range of motion (Fig. 2 B). Nonetheless, the native condition tended towards reduced varus compared to TKA. However, no significant difference was detected (p > 0.157, RMSE = 1.734°). In terms of internal-external rotation, both conditions displayed internal rotation, with the native condition exhibiting decreased internal rotation after mid-flexion. However, significant differences between these two conditions were evident only between 35° and 61° of knee flexion (p 0.973). On the other hand, significant differences in AP translation between both conditions were found within the knee flexion range of 35° and 100° (0.001 < p < 0.044, RMSE = 6.426mm, 1.920 3.344), with the native condition displaying lower magnitude translations compared to those of the postoperative condition. Patellofemoral Kinematics In terms of patellar kinematics during squatting, both native and postoperative conditions displayed a closely matched linear increase in patellar flexion (Fig. 3 A), with no significant difference observed (p > 0.140, RMSE = 1.217°). For patella abduction (Fig. 3 B), both conditions maintained a plateau, preserving a consistent offset throughout the entire squatting motion (p > 0.710, RMSE = 0.465°). On the other hand, for patellar tilting (Fig. 3 C), both conditions showed a similar tendency towards the external rotation of the patella to the femur throughout squatting (p > 0.421, RMSE = 0.507), while remaining within the internal rotation region. In addition, although there was no statistical difference observed between both conditions for patellar translations (Fig. 3 D-F) in the anterior-posterior (p > 0.162, RMSE = 1.677 mm), medial-lateral (p > 0.155, RMSE = 2.541 mm), and inferior-superior directions (p > 0.099, RMSE = 1.330 mm), the largest offset between the two conditions was found in the medial-lateral translation, with the native condition showing an increased medial translation compare to the postoperative condition. Collateral Ligament Strains During passive flexion, the strain in the anterior bundle increased (lengthening or tensed) in the native and TKA conditions, with the former showing a greater lengthening. Furthermore, a statistical difference was observed between 55° and 68° (0.045 < p < 0.049, RMSE = 3.792%, 0.397 < ES < 0.358). For the middle bundle, although the native condition showed a slight lengthening until late mid-flexion, both conditions demonstrated decreased strain (shortening or relaxation) during the remaining range of motion, and no statistical difference was observed (p > 0.131, RMSE = 2.69%). In contrast, both conditions exhibited a similar trend for the posterior bundle, decreasing strain (shortening) throughout the entire motion, with no statistical difference (p > 0.127, RMSE = 2.04%). On the other hand, each bundle measured similar strain for LCL strain for both conditions until early mid-flexion. Moreover, the native condition consistently displayed decreasing strain compared to the postoperative condition after mid-flexion. Nevertheless, none of the measured outcomes reached statistical difference (p > 0.589, RMSE 0.078, RMSE = 1.542%), middle (p > 0.204, RMSE = 0.762%) and posterior (p > 0.351, RMSE = 0.827%) bundles of MCL resulted in increasingly similar strain behavior (shortening) from anterior to posterior in both native condition and postoperative conditions, with no statistical difference found. In contrast, the anterior, middle and posterior bundles of LCL exhibited a greater offset between the native and postoperative conditions after early mid-flexion, albeit the pattern was comparable. Moreover, significant differences were detected between the native and the postoperative conditions in terms of the strains in the anterior (69°-100°, 0.012 < p ES > 0.505), middle (73°-93°, 0.037 < p ES > 0.606) and posterior (61°-100°, 0.002 < p ES > 0.505) bundles of the LCL. Discussion The primary finding of this study was that overall tibiofemoral kinematics and collateral ligament strains demonstrated similar patterns throughout full motion range in passive conditions, as targeted using the Next-AR navigation system. Comparable tibiofemoral kinematic behaviors were also observed during squatting motion, albeit with a higher offset, especially in varus-valgus orientation and tibial internal-external rotation. In terms of collateral ligament strains during squatting, the native and TKA conditions exhibited decreasing and similar MCL strain in all bundles. LCL strain was increased after surgery both in passive flexion and squatting in all bundles particularly from early mid-flexion to deep flexion range. During passive motion, the native condition exhibited a marginally higher strain pattern on the MCL bundles (3.792% ≥ RMSE ≤ 2.04%), especially in the anterior and middle bundles. This non-significant difference between the native and TKA conditions could potentially be explained by a reduced varus orientation (RMSE = 0.763°) and increased tibial internal rotation (RMSE = 2.862°) in the native knee compared to TKA. Additionally, the increased anterior translation of the femur up to late mid-flexion observed in TKA may have further contributed to the disparity between the two conditions. As anticipated based on this kinematics behavior in the native and TKA conditions, the strain pattern on the LCL exhibited an opposite trend, with the TKA condition showing increased strain across all LCL bundles (RMSE < 3.684%) throughout knee flexion. This suggests that the kinematic variations in TKA influence the LCL in a manner analogous to the MCL for passive flexion. Correct tibial rotation plays a role in achieving screw home mechanism, however, it is documented that this mechanism is slightly decreased after TKA due to resection of ACL and prosthesis design. [ 17 , 18 ] During squatting motion, the slightly reduced strain in all MCL bundles in the TKA condition, compared to the native condition, may be due to the increased varus orientation following TKA, which likely minimized tension on the medial side. Additionally, the greater tibial internal rotation in the TKA condition might lead to less direct engagement of the MCL bundles. Other studies using different bearing designs showed more pronounced elongation of the anterior MCL during flexion motion. In all studies, the primary determinant of ligament elongation was increased knee flexion. Another explanation for this difference in strain curves might be component design. Elongation of the anterior MCL from extension to 90° flexion was seen in active squatting motion of a CR design. [ 19 , 20 , 21 ] Posterior stabilized designs have been shown to double MCL strain during squatting in a cadaveric setup with peak strains at 60° flexion. [ 22 ] These authors reconfirmed higher MCL strains at > 20° flexion, however, only in mechanically aligned TKA and not in kinematic TKA.[ 22 , 23 ] On the contrary, an in vivo gait study of 30 subjects compared PS, medial pivot and ultracongruent designs in terms of MCL and LCL changes. They found that component design did not demonstrate statistically significant effects on elongation patterns of collaterals. For the LCL bundles, the consistently higher strain (lengthening) observed in the TKA condition seemed to be related to the combined effects of increased varus orientation and tibial internal rotation. Another explanation for higher LCL strain curves might be the external rotation of the femoral component as performed in mechanical alignment. Together, these kinematic behaviors likely pull the lateral side further outward relative to the femur, placing additional stretch on the LCL. Although the native knee exhibited comparable kinematic behavior, the reduced varus orientation and increased posterior translation of the femur relative to the tibia may explain the decreased LCL strain (shortening) observed in the native condition. The effect of patellar kinematics and contact pressure on clinical function after TKA is an ongoing debate. It is hypothesized that higher contact pressures related to prosthesis design, femoral roll forward and internal rotation of the tibia can lead to postoperative anterior knee pain. Other in vitro studies showed higher reduction in mediolateral laxity after TKA and attributed this to overstuffing of the patellofemoral joint after patellar resurfacing. [ 24 , 25 ] Our results showed a reduction in mediolateral translation of only 2mm after surgery. Similar pre- and postoperative patellar kinematics concerning patellar tilt, -abduction, or -flexion were seen in our series indicating a correct restoration of anatomy and contact pressures. Our study shows some limitations. Cadaveric preparation might influence joint- and ligament behavior. The use of the physiological knee simulator mimics loaded squatting motion, however the loads used in the muscles might not accurately reflect the natural loads experienced in vivo. We know that structural damage is occurring in ligaments from 5.14% strain levels and mechanoreceptors in ligaments have been documented [ 26 ], however the clinical value of ligament strain is unknown. On the other hand, a comparison between native and postoperative knees is valuable in terms of recreating native joint conditions. Conclusion Accurate tibiofemoral kinematics and ligament behavior data based on passive flexion-extension motions were achieved with the Next-AR navigation tool. We believe that Next-AR provides a useful tool for the surgeon to accurately balance TKA and achieve targeted biomechanical properties. Declarations Compliance with ethical standards GP has been paid for presentations and has received research support from Medacta. Ethical approval All performed procedures were approved and done in accordance with the institutional research ethics committee (Katholieke Universiteit Leuven, Belgium, NH019 2021-04-01) and the 1964 Declaration of Helsinki and its later amendments for comparable ethi- cal standards. Informed consent Knee specimens were obtained from Anatomy, KU Leuven, Belgium. Donors had dedicated their bodies to education and science during life time. Funding The study was funded and implants were donated by Medacta International, Switzerland. Author Contribution - AVDV: Investigation, Data Curation, Writing - Original Draft, Resources, - OT.: Conceptualization, Methodology, Software, Validation, Formal analysis, Investigation, Data curation, Writing- Original Draft, Visualization, Project administration. - GP: Conceptualization, Methodology, Investigation, Resources, Data Curation, Writing - Review & Editing, Supervision, Project administration, Funding acquisition. - MB: Writing - Review & Editing, Supervision, Project administration.: - MD: Writing - Review & Editing.: - TL: Software, Investigation, Writing - Review & Editing, Project administration. - LS: Conceptualization, Methodology, Investigation, Resources, Data Curation, Writing - Review & Editing, Supervision, Project administration. References Gray HA, Guan S, Young TJ, Dowsey MM, Choong PF, Pandy MG (2020) Comparison of posterior-stabilized, cruciate-retaining, and medial-stabilized knee implant motion during gait. 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J Arthroplasty 32(1):280–285. 10.1016/j.arth.2016.06.044 Steinbrück A, Schröder C, Woiczinski M, Müller T, Müller PE, Jansson V, Fottner A (2016) Influence of tibial rotation in total knee arthroplasty on knee kinematics and retropatellar pressure: an in vitro study. Knee Surg Sports Traumatol Arthrosc. ;24(8):2395 – 401. 10.1007/s00167-015-3503-1 . Epub 2015 Jan 11. PMID: 25577221 Delport H, Labey L, De Corte R, Innocenti B, Vander Sloten J, Bellemans J (2013) Collateral ligament strains during knee joint laxity evaluation before and after TKA. Clin Biomech (Bristol Avon) 28(7):777–782. 10.1016/j.clinbiomech.2013.06.006 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6876936","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":471759818,"identity":"073f53b8-dd83-4d02-a563-55ccd583b539","order_by":0,"name":"Arne Van de Vyver","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/ElEQVRIiWNgGAWjYBADxgYIbQNiNx4gRUsamE2SlsNgEq8W/tlnDz7mqbkj2y+RYybxcc95u7Xth4G21NhE49IicS4v2Zjn2DPjmTNyzCRnPLudvO1MIlDLsbTcBlx6zvAAVbIdTtxw5oyxMc+B28lmB4BaGBsO49Qif4bH/OeMf4cT94O0/DlwLtns/EP8WgyAtjB8bAPawt5j+JjhwAE7sxsEbDE8w2Ms8bHvsPGM422FD3sOJCeY3QDakoDHL3JneAw/JHw7LNvfzLzhwI8DdvZm59MfPvhQY4Pb+wjAYQAiE8EqEwgrBwH2ByDSnjjFo2AUjIJRMJIAABmgah6hECISAAAAAElFTkSuQmCC","orcid":"","institution":"ZAS Cadix","correspondingAuthor":true,"prefix":"","firstName":"Arne","middleName":"Van","lastName":"de Vyver","suffix":""},{"id":471759819,"identity":"0fd9abbf-99eb-4b86-99f9-63ac030bd2ec","order_by":1,"name":"Orçun Taylan","email":"","orcid":"","institution":"Institute for Orthopaedic Research and Training (IORT)","correspondingAuthor":false,"prefix":"","firstName":"Orçun","middleName":"","lastName":"Taylan","suffix":""},{"id":471759820,"identity":"1871b490-54ed-4730-bff1-bac1891cb12d","order_by":2,"name":"Geert Peersman","email":"","orcid":"","institution":"ZAS Cadix","correspondingAuthor":false,"prefix":"","firstName":"Geert","middleName":"","lastName":"Peersman","suffix":""},{"id":471759821,"identity":"6999b1c6-5466-4761-8467-50a80e039c0b","order_by":3,"name":"Bialy Maciej","email":"","orcid":"","institution":"Institute for Orthopaedic Research and Training (IORT)","correspondingAuthor":false,"prefix":"","firstName":"Bialy","middleName":"","lastName":"Maciej","suffix":""},{"id":471759822,"identity":"5aa8bbda-07f7-40f4-988e-3ac3e129b1f3","order_by":4,"name":"Margot Demeulenaere","email":"","orcid":"","institution":"ZAS Cadix","correspondingAuthor":false,"prefix":"","firstName":"Margot","middleName":"","lastName":"Demeulenaere","suffix":""},{"id":471759823,"identity":"b5853560-b479-4b41-888b-50915a5b63cb","order_by":5,"name":"Thomas Lauwagie","email":"","orcid":"","institution":"Institute for Orthopaedic Research and Training (IORT)","correspondingAuthor":false,"prefix":"","firstName":"Thomas","middleName":"","lastName":"Lauwagie","suffix":""},{"id":471759824,"identity":"95ed7c22-cafd-4466-a51a-da6fc2a35083","order_by":6,"name":"Scheys Lennart","email":"","orcid":"","institution":"Institute for Orthopaedic Research and Training (IORT)","correspondingAuthor":false,"prefix":"","firstName":"Scheys","middleName":"","lastName":"Lennart","suffix":""}],"badges":[],"createdAt":"2025-06-12 06:08:33","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6876936/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6876936/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":85361860,"identity":"1e770b24-ba3f-4509-b455-74597c8abfff","added_by":"auto","created_at":"2025-06-25 06:15:08","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":411337,"visible":true,"origin":"","legend":"\u003cp\u003eThe surgical procedure and ex-vivo testing. (A) Patient-specific surgical guide and holders for the camera and the receiver, (B) registration of the bone surface to the model, (C) resection of the bone using dedicated cutting guides, (D) implantation of a cemented total knee arthroplasty (GMK Sphere, Medacta International) and (E) quasistatic squatting in an Oxford-based physiological ex-vivo knee simulator.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6876936/v1/4f4df3e7bfdd8a08baee016f.png"},{"id":85362812,"identity":"95c27015-27a6-41a5-894c-6a9df1c05618","added_by":"auto","created_at":"2025-06-25 06:23:08","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":200269,"visible":true,"origin":"","legend":"\u003cp\u003eTibiofemoral kinematics of the knee in the native condition (black) and TKA (red) conditions during passive flexion (left column) and squatting (right column). (A-B) tibial varus-valgus orientation (varus\u0026lt;0, valgus\u0026gt;0), (C-D) tibial internal-external rotation (external rotation\u0026lt;0, internal rotation\u0026gt;0), and (E-F) tibia AP translation (Posterior\u0026lt;0, Anterior\u0026gt;0). Data are represented as mean (solid) ± SD (shaded) across six specimens. The asterisk indicates a significant difference \u0026lt;0.05, while the dashed black line illustrates the range of knee flexion where this significant difference is found.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6876936/v1/0b5706ac484fd7180c6a83a4.png"},{"id":85361861,"identity":"a0858df2-260b-4eef-bcc4-cf4e3762f07b","added_by":"auto","created_at":"2025-06-25 06:15:08","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":188475,"visible":true,"origin":"","legend":"\u003cp\u003ePatellofemoral kinematics in the native (black) and TKA (red) conditions during squatting motion. (A) Patella flexion, (B) abduction (medial (+)/lateral (−)), (C) tilting (medial (+)/lateral (−)), (D) anterior (+)/posterior (−) translation, (E) medial (+)/lateral (−) translation, and (F) inferior (−)/superior (+) translation. Data are represented as mean (solid) ± SD (shaded) across six specimens. The black arrows on the 3D model of the patella exhibit the motion direction relative to the femur, while blue solid lines display the axis of motion. A-P = Anterior-posterior, M-L = Medial-Lateral, I-S = Inferior-Superior\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-6876936/v1/5bed28c472955743b4385aa6.png"},{"id":85362817,"identity":"b9d2ebda-0e41-47cd-9b78-8ff779885334","added_by":"auto","created_at":"2025-06-25 06:23:08","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":194905,"visible":true,"origin":"","legend":"\u003cp\u003eAbsolute change in medial collateral ligament strain (%, top row) and lateral collateral ligament strain (%, bottom row) in anterior (blue), middle (red) and posterior (pink) bundle (e.g. antMCL) across six specimens during (A,C) passive flexion and (B,D) squatting for the native condition (solid), and following total knee arthroplasty using medially-stabilized GMK sphere (dashed). The data is represented as mean (solid and dashed) ± SD (shaded) across six specimens. The asterisk indicates a significant difference \u0026lt;0.05, while the dashed black line illustrates the range of knee flexion where this significant difference is found. Moreover, the significant differences across groups are represented based on their associated colors. MCL = medial collateral ligament, LCL = lateral collateral ligament, ant = anterior, mid = middle, post = posterior.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-6876936/v1/714fd75241ff1d4391a776ce.png"},{"id":91825517,"identity":"2aca5b2c-d75f-45b2-8713-497e38a9ef33","added_by":"auto","created_at":"2025-09-22 08:31:47","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1580710,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6876936/v1/e3709c91-87d2-44d9-bb64-1859c3478423.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Changes in kinematic behavior and collateral ligament strain after medially stabilized TKA using a novel Intraoperative Navigation Platform: a cadaveric study","fulltext":[{"header":"Introduction","content":"\u003cp\u003eTotal knee arthroplasty (TKA) is a highly successful treatment for end-stage knee osteoarthritis and aims to restore pre-operative biomechanical- and kinematic properties mimicking the native knee joint. [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e] Despite the overall success of TKA, a notable proportion of patients may remain dissatisfied post-surgery. Factors contributing to dissatisfaction include joint pain, reduced motion, instability, implant failure, poor soft tissue balance, and implant choice. [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] Advancements have been made in various aspects of TKA technologies to address dissatisfaction and alignment outliers, advancements have been made in various aspects of TKA technology. These include improvements in implant design and materials, image-based cutting guides, patient-specific implants, and computer-navigated surgery. [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] Navigation systems, whether imageless or image-based (CT or MRI) assist in achieving desired alignment goal, thus recreating optimal ligament tension and knee kinematics.\u003c/p\u003e \u003cp\u003eThere is ongoing debate about which type of implant design is superior. Currently, the most popular designs are cruciate retaining (CR) and posterior stabilized (PS) implants. Additionally, medially stabilized implants have been introduced to mimic natural knee kinematics, such as femoral rollback and ligament behavior, more closely. [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/p\u003e \u003cp\u003ePrevious studies have shown that none of the ligament bundles of MCL and LCL showed isometric behavior after TKA, regardless of implant design. Achieving symmetrical flexion- and extension will, therefore, not guarantee optimal soft tissue balance. [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] Preservation of ligament tension during knee motion is challenging in TKA and new technologies are emerging to cope with these challenges.\u003c/p\u003e \u003cp\u003eMedacta International has recently introduced the Next-Ar Navigation Platform (Medacta International, Strada Regina, Switzerland), a wireless single use tracking system mounted directly onto bone. This system provides real-time intraoperative feedback by using preoperative CT to identify bony landmarks and ligamentous insertions. Consequently, the surgeon can monitor bone resection, knee alignment, tibiofemoral kinematics and collateral ligament elongation. Precise adjustments can be made during the procedure.\u003c/p\u003e \u003cp\u003eThis study aims to assess the efficacy of a novel Next-AR system for medially stabilized TKA in restoring native joint kinematics and collateral ligament strains in a cadaveric set-up\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003ePreoperative specimen imaging and surgical planning\u003c/h2\u003e \u003cp\u003eSeven fresh-frozen full cadaveric legs (age\u0026thinsp;=\u0026thinsp;80.8\u0026thinsp;\u0026plusmn;\u0026thinsp;9.59, three unilateral female donors, one unilateral and two bilateral male donors, height\u0026thinsp;=\u0026thinsp;165 cm\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5, and weight\u0026thinsp;=\u0026thinsp;66 kg\u0026thinsp;\u0026plusmn;\u0026thinsp;10.5) were obtained following ethical approval from the local Ethics Committee (NH019-2021-04-01). The specimens were screened for potential lower limb disorder and prior surgical intervention. Following, bicortical bone pins were fixed into the femur, tibia, and patella to rigidly attach dedicated rigid marker frames, each containing four reflective spheres. Each specimen's computer tomography (CT) scans (Siemens Somatom Force, Siemens Healthcare, Erlangen, Germany) were then acquired in full extension with a slice thickness of 0.6 mm. Segmentation software (Mimics 25.0, Materialise, Leuven, Belgium) was used based on the well-established algorithm to identify the location of spherical markers and the required anatomical landmarks from CT images. [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] These identified landmarks were used to define bone-specific joint coordinate systems for the femur, tibia, and patella based on the Grood and Suntay convention[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAdditional CT scans of the hip, knee, and ankle of each subject were acquired conforming to the MyKnee protocol (Medacta International SA, Castel San Pietro, Switzerland) to design patient-specific surgical guides [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], including the proprietary holders for the Next-AR motion trackers (a camera and a receiver unit), for mechanical alignment technique and to generate input parameters, such as 3D models of the bones, bony landmarks, and insertions of the collateral ligaments [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Subsequently, these input parameters were exported into the Next-AR Navigation Platform.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSpecimen preparation\u003c/h3\u003e\n\u003cp\u003eEach specimen was thawed 24 hours before testing, with a single freezing-thawing cycle. The femur and the tibia were resected 32 cm proximally and 28 cm distally to the knee joint line, respectively. Care was taken to preserve the joint capsule, ligaments and tendons while removing the skin and subcutaneous tissue around the knee joint. The exposed quadriceps tendon was clamped within a custom metal clamp, and suture loops (2x2 non-absorbable polyester braided suture wire; Cardioxyl, Peters Surgical, Bobigny Cedex, France) were passed through the medial and lateral hamstring tendons. The tibia and femur were embedded in metal containers using an acrylic resin (Struers, Ballerup, Denmark) while positioning the femur in 6\u0026deg; of valgus.\u003c/p\u003e\n\u003ch3\u003ePreoperative Testing\u003c/h3\u003e\n\u003cp\u003eThe native specimens were mounted into an Oxford-based physiological ex-vivo knee simulator and subjected to passive flexion (10\u0026deg;\u0026ndash;120\u0026deg;) and squatting (35\u0026deg;\u0026ndash;100\u0026deg;), respectively. During passive flexion, the femur pot was rigidly attached to the knee simulator, with the tibia and the tendons left unconstrained. Subsequently, the tibia was manually cycled from maximum extension to maximum flexion angle.\u003c/p\u003e \u003cp\u003eFor squatting motion, the tibial pot was mounted to the ankle assembly. The suture loops fixed to the medial and collateral hamstring tendons were connected to the medial and lateral electromechanical hamstring actuators through a steel pulley and cable system. The quadriceps clamp was affixed to the quadriceps electromechanical actuators directly through a clevis and pin assembly.\u003c/p\u003e \u003cp\u003eDuring squatting motion, a computer-controlled electromechanical actuator was used to apply a dynamic load to the quadriceps tendon. while computer-controlled electromechanical actuators individually applied a constant 50 N load to the medial and lateral hamstrings. In conjunction with simultaneously controlling the vertical translation of the ankle assembly to facilitate flexion and extension, the controller ensured a constant vertical ankle load of 110 N throughout the squatting motion. Each motion was performed in triplicate, and the trajectories of the retro-reflective spheres attached to the specimens were recorded using six infrared cameras (Vero v1.3, Vicon Motion Systems, Oxford, UK) operating at 100 Hz.\u003c/p\u003e \u003cp\u003eAfter performing functional motion tests, the insertions of the medial collateral ligament (MCL) and lateral collateral ligament (LCL) were carefully exposed. Subsequently, the coordinates of each ligament bundle (anterior, middle, and posterior) were recorded using a dedicated optical motion capture system's wand, equipped with five spherical retro-reflective markers. Moreover, for precise and physiologically accurate computation of Vicon-based ligament elongations, while using a shortest path calculation, the tibial plateau edge was defined as a 3D spline using Mimics (Materialise, Leuven, Belgium). It is noteworthy that such measures were not required for the LCL, given its absence of anatomical wrapping around the tibial plateau.\u003c/p\u003e\n\u003ch3\u003eSurgical technique and postoperative testing\u003c/h3\u003e\n\u003cp\u003eTwo knees were excluded from pre- and postoperative squatting motion analysis due to early quadriceps tendon failure after surgery. All eight knees were included in pre- and postoperative passive flexion analysis.\u003c/p\u003e \u003cp\u003eAfter testing the native knees, each knee underwent a cemented cruciate-sacrificing total knee arthroplasty (medially stabilized, GMK Sphere, Medacta International) using a mechanical alignment technique. First, the patient-specific surgical guides were rigidly fixed to the femur and tibia with bone pins. Following, the Next-AR motion tracker unit\u0026mdash;a camera and a receiver\u0026mdash;were rigidly attached to detachable device housings mounted on the guides (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA). To minimize potential discrepancies between the positions reported by the motion tracker unit and the actual bone positions, fine-tuning correction was performed throughout the registration process. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] Subsequently, the surgical guides were removed while maintaining the camera and receiver units fixed. Before resecting the bones, the absolute change in the collateral ligament lengths to an initial value (extended knee (0\u0026deg;-10\u0026deg;)) was determined and tibiofemoral kinematics were documented during passive flexion-extension.\u003c/p\u003e \u003cp\u003eThe cutting jigs were affixed to the femur first, followed by the tibia, and then sequential bone resections were carried out. Subsequently, a cemented TKA was implanted. Postoperative collateral ligament elongations and tibiofemoral kinematics were digitally recorded during passive flexion-extension cycles. These recordings were then compared to the preoperatively measured reference curves. No additional cuts or ligament releases were performed during this experiment.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eData processing\u003c/h3\u003e\n\u003cp\u003eThe trajectories of reflective markers captured with the Vicon optical motion capture system were processed using motion tracking software (Nexus 2.9, Vicon, Oxford, UK). Based hereon, the tibio- and patellofemoral kinematics and the elongation of each collateral ligament bundle (anterior, middle and posterior) were computed. For the latter, the method described by Marai et al. was used [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe kinematic variables, along with the collateral ligament elongations, were downsampled and interpolated at 1\u0026deg; intervals of flexion, all within the common knee flexion range shared by all specimens: 10\u0026deg; to 100\u0026deg; for passive flexion and 35\u0026deg; to 10\u0026deg; for squatting. Furthermore, the absolute difference between the output measured at the initial reference knee flexion angle (10\u0026deg; for passive flexion and 35\u0026deg; for squatting) and the value at each subsequent angle was used to compute the engineering strain of collateral ligament bundles throughout the motion. The initial knee flexion angle was considered 0% and all subsequent measurements were expressed to this initial value using a custom code in Matlab (R2022a, Mathworks Inc, Natick, MA, USA).\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eA linear mixed model was used to compare measured outputs derived from native and postoperative conditions, such as tibio- and patellofemoral kinematics and collateral ligament strains. Subsequently, Tukey's HSD post hoc test was performed for pairwise comparisons at each knee flexion angle. The residuals were assessed for normality, multicollinearity, and heteroscedasticity. No transformations were required as assumptions were met.\u003c/p\u003e \u003cp\u003eThe Cohen\u0026rsquo;s d effect size (ES, large\u0026thinsp;\u0026ge;\u0026thinsp;0.8 and small\u0026thinsp;\u0026le;\u0026thinsp;0.2) was computed for the statistically different groups. Additionally, the mean Root-Mean-Square Error (RMSE) for the entire motion was calculated to quantify the difference between the mean curves of the conditions. All statistical analyses were performed in R (R-Studio Version 2023.03.1, Boston, MA), and the significance level was determined at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eTibiofemoral Kinematics\u003c/h2\u003e \u003cp\u003eDuring passive flexion, both native and postoperative conditions exhibited a similar trend in varus-valgus behavior (p\u0026thinsp;\u0026gt;\u0026thinsp;0.508, mean Root-Mean-Square Error (RMSE)\u0026thinsp;=\u0026thinsp;0.763\u0026deg;): an initial increase in varus until mid-flexion, followed by a subsequent decrease throughout the remaining range of motion (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA). For tibial internal-external rotation, the native and postoperative conditions showed a tendency towards increased internal rotation (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC). Nonetheless, a significant difference between the native and postoperative conditions was observed after 81\u0026deg; of knee flexion angle (0.028\u0026thinsp;\u0026lt;\u0026thinsp;p\u0026thinsp;\u0026lt;\u0026thinsp;0.048, RMSE\u0026thinsp;=\u0026thinsp;2.862\u0026deg;, 0.765\u0026thinsp;\u0026lt;\u0026thinsp;Effect size (ES)\u0026thinsp;\u0026gt;\u0026thinsp;0.713). In terms of AP translation of the tibia knee center with respect to the femur knee center, significant differences were observed between 52\u0026deg; and 120\u0026deg; (0.001\u0026thinsp;\u0026lt;\u0026thinsp;p\u0026thinsp;\u0026lt;\u0026thinsp;0.045, RMSE\u0026thinsp;=\u0026thinsp;5.639mm, 1.014\u0026thinsp;\u0026lt;\u0026thinsp;Effect size (ES)\u0026thinsp;\u0026gt;\u0026thinsp;3.854).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eDuring squatting, both native and postoperative conditions consistently maintained varus orientation across the entire range of motion (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB). Nonetheless, the native condition tended towards reduced varus compared to TKA. However, no significant difference was detected (p\u0026thinsp;\u0026gt;\u0026thinsp;0.157, RMSE\u0026thinsp;=\u0026thinsp;1.734\u0026deg;). In terms of internal-external rotation, both conditions displayed internal rotation, with the native condition exhibiting decreased internal rotation after mid-flexion. However, significant differences between these two conditions were evident only between 35\u0026deg; and 61\u0026deg; of knee flexion (p\u0026thinsp;\u0026lt;\u0026thinsp;0.045, EMSE\u0026thinsp;=\u0026thinsp;3.284, ES\u0026thinsp;\u0026gt;\u0026thinsp;0.973). On the other hand, significant differences in AP translation between both conditions were found within the knee flexion range of 35\u0026deg; and 100\u0026deg; (0.001\u0026thinsp;\u0026lt;\u0026thinsp;p\u0026thinsp;\u0026lt;\u0026thinsp;0.044, RMSE\u0026thinsp;=\u0026thinsp;6.426mm, 1.920\u0026thinsp;\u0026lt;\u0026thinsp;Effect size (ES)\u0026thinsp;\u0026gt;\u0026thinsp;3.344), with the native condition displaying lower magnitude translations compared to those of the postoperative condition.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003ePatellofemoral Kinematics\u003c/h2\u003e \u003cp\u003eIn terms of patellar kinematics during squatting, both native and postoperative conditions displayed a closely matched linear increase in patellar flexion (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA), with no significant difference observed (p\u0026thinsp;\u0026gt;\u0026thinsp;0.140, RMSE\u0026thinsp;=\u0026thinsp;1.217\u0026deg;). For patella abduction (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB), both conditions maintained a plateau, preserving a consistent offset throughout the entire squatting motion (p\u0026thinsp;\u0026gt;\u0026thinsp;0.710, RMSE\u0026thinsp;=\u0026thinsp;0.465\u0026deg;). On the other hand, for patellar tilting (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC), both conditions showed a similar tendency towards the external rotation of the patella to the femur throughout squatting (p\u0026thinsp;\u0026gt;\u0026thinsp;0.421, RMSE\u0026thinsp;=\u0026thinsp;0.507), while remaining within the internal rotation region.\u003c/p\u003e \u003cp\u003eIn addition, although there was no statistical difference observed between both conditions for patellar translations (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eD-F) in the anterior-posterior (p\u0026thinsp;\u0026gt;\u0026thinsp;0.162, RMSE\u0026thinsp;=\u0026thinsp;1.677 mm), medial-lateral (p\u0026thinsp;\u0026gt;\u0026thinsp;0.155, RMSE\u0026thinsp;=\u0026thinsp;2.541 mm), and inferior-superior directions (p\u0026thinsp;\u0026gt;\u0026thinsp;0.099, RMSE\u0026thinsp;=\u0026thinsp;1.330 mm), the largest offset between the two conditions was found in the medial-lateral translation, with the native condition showing an increased medial translation compare to the postoperative condition.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eCollateral Ligament Strains\u003c/h2\u003e \u003cp\u003eDuring passive flexion, the strain in the anterior bundle increased (lengthening or tensed) in the native and TKA conditions, with the former showing a greater lengthening. Furthermore, a statistical difference was observed between 55\u0026deg; and 68\u0026deg; (0.045\u0026thinsp;\u0026lt;\u0026thinsp;p\u0026thinsp;\u0026lt;\u0026thinsp;0.049, RMSE\u0026thinsp;=\u0026thinsp;3.792%, 0.397\u0026thinsp;\u0026lt;\u0026thinsp;ES\u0026thinsp;\u0026lt;\u0026thinsp;0.358). For the middle bundle, although the native condition showed a slight lengthening until late mid-flexion, both conditions demonstrated decreased strain (shortening or relaxation) during the remaining range of motion, and no statistical difference was observed (p\u0026thinsp;\u0026gt;\u0026thinsp;0.131, RMSE\u0026thinsp;=\u0026thinsp;2.69%). In contrast, both conditions exhibited a similar trend for the posterior bundle, decreasing strain (shortening) throughout the entire motion, with no statistical difference (p\u0026thinsp;\u0026gt;\u0026thinsp;0.127, RMSE\u0026thinsp;=\u0026thinsp;2.04%). On the other hand, each bundle measured similar strain for LCL strain for both conditions until early mid-flexion. Moreover, the native condition consistently displayed decreasing strain compared to the postoperative condition after mid-flexion. Nevertheless, none of the measured outcomes reached statistical difference (p\u0026thinsp;\u0026gt;\u0026thinsp;0.589, RMSE\u0026thinsp;\u0026lt;\u0026thinsp;3.684%).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eDuring squatting, the anterior (p\u0026thinsp;\u0026gt;\u0026thinsp;0.078, RMSE\u0026thinsp;=\u0026thinsp;1.542%), middle (p\u0026thinsp;\u0026gt;\u0026thinsp;0.204, RMSE\u0026thinsp;=\u0026thinsp;0.762%) and posterior (p\u0026thinsp;\u0026gt;\u0026thinsp;0.351, RMSE\u0026thinsp;=\u0026thinsp;0.827%) bundles of MCL resulted in increasingly similar strain behavior (shortening) from anterior to posterior in both native condition and postoperative conditions, with no statistical difference found. In contrast, the anterior, middle and posterior bundles of LCL exhibited a greater offset between the native and postoperative conditions after early mid-flexion, albeit the pattern was comparable. Moreover, significant differences were detected between the native and the postoperative conditions in terms of the strains in the anterior (69\u0026deg;-100\u0026deg;, 0.012\u0026thinsp;\u0026lt;\u0026thinsp;p\u0026thinsp;\u0026lt;\u0026thinsp;0.046, RMSE\u0026thinsp;=\u0026thinsp;3.013%, 0.640\u0026thinsp;\u0026gt;\u0026thinsp;ES\u0026thinsp;\u0026gt;\u0026thinsp;0.505), middle (73\u0026deg;-93\u0026deg;, 0.037\u0026thinsp;\u0026lt;\u0026thinsp;p\u0026thinsp;\u0026lt;\u0026thinsp;0.048, RMSE\u0026thinsp;=\u0026thinsp;3.022%, 0.797\u0026thinsp;\u0026gt;\u0026thinsp;ES\u0026thinsp;\u0026gt;\u0026thinsp;0.606) and posterior (61\u0026deg;-100\u0026deg;, 0.002\u0026thinsp;\u0026lt;\u0026thinsp;p\u0026thinsp;\u0026lt;\u0026thinsp;0.046, RMSE\u0026thinsp;=\u0026thinsp;4.628%%, 1.138\u0026thinsp;\u0026gt;\u0026thinsp;ES\u0026thinsp;\u0026gt;\u0026thinsp;0.505) bundles of the LCL.\u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe primary finding of this study was that overall tibiofemoral kinematics and collateral ligament strains demonstrated similar patterns throughout full motion range in passive conditions, as targeted using the Next-AR navigation system.\u003c/p\u003e \u003cp\u003eComparable tibiofemoral kinematic behaviors were also observed during squatting motion, albeit with a higher offset, especially in varus-valgus orientation and tibial internal-external rotation. In terms of collateral ligament strains during squatting, the native and TKA conditions exhibited decreasing and similar MCL strain in all bundles. LCL strain was increased after surgery both in passive flexion and squatting in all bundles particularly from early mid-flexion to deep flexion range.\u003c/p\u003e \u003cp\u003eDuring passive motion, the native condition exhibited a marginally higher strain pattern on the MCL bundles (3.792% \u0026ge; RMSE\u0026thinsp;\u0026le;\u0026thinsp;2.04%), especially in the anterior and middle bundles. This non-significant difference between the native and TKA conditions could potentially be explained by a reduced varus orientation (RMSE\u0026thinsp;=\u0026thinsp;0.763\u0026deg;) and increased tibial internal rotation (RMSE\u0026thinsp;=\u0026thinsp;2.862\u0026deg;) in the native knee compared to TKA. Additionally, the increased anterior translation of the femur up to late mid-flexion observed in TKA may have further contributed to the disparity between the two conditions. As anticipated based on this kinematics behavior in the native and TKA conditions, the strain pattern on the LCL exhibited an opposite trend, with the TKA condition showing increased strain across all LCL bundles (RMSE\u0026thinsp;\u0026lt;\u0026thinsp;3.684%) throughout knee flexion. This suggests that the kinematic variations in TKA influence the LCL in a manner analogous to the MCL for passive flexion.\u003c/p\u003e \u003cp\u003eCorrect tibial rotation plays a role in achieving screw home mechanism, however, it is documented that this mechanism is slightly decreased after TKA due to resection of ACL and prosthesis design. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eDuring squatting motion, the slightly reduced strain in all MCL bundles in the TKA condition, compared to the native condition, may be due to the increased varus orientation following TKA, which likely minimized tension on the medial side. Additionally, the greater tibial internal rotation in the TKA condition might lead to less direct engagement of the MCL bundles. Other studies using different bearing designs showed more pronounced elongation of the anterior MCL during flexion motion. In all studies, the primary determinant of ligament elongation was increased knee flexion. Another explanation for this difference in strain curves might be component design. Elongation of the anterior MCL from extension to 90\u0026deg; flexion was seen in active squatting motion of a CR design. [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] Posterior stabilized designs have been shown to double MCL strain during squatting in a cadaveric setup with peak strains at 60\u0026deg; flexion. [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e] These authors reconfirmed higher MCL strains at \u0026gt;\u0026thinsp;20\u0026deg; flexion, however, only in mechanically aligned TKA and not in kinematic TKA.[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] On the contrary, an in vivo gait study of 30 subjects compared PS, medial pivot and ultracongruent designs in terms of MCL and LCL changes. They found that component design did not demonstrate statistically significant effects on elongation patterns of collaterals.\u003c/p\u003e \u003cp\u003eFor the LCL bundles, the consistently higher strain (lengthening) observed in the TKA condition seemed to be related to the combined effects of increased varus orientation and tibial internal rotation. Another explanation for higher LCL strain curves might be the external rotation of the femoral component as performed in mechanical alignment. Together, these kinematic behaviors likely pull the lateral side further outward relative to the femur, placing additional stretch on the LCL. Although the native knee exhibited comparable kinematic behavior, the reduced varus orientation and increased posterior translation of the femur relative to the tibia may explain the decreased LCL strain (shortening) observed in the native condition.\u003c/p\u003e \u003cp\u003eThe effect of patellar kinematics and contact pressure on clinical function after TKA is an ongoing debate. It is hypothesized that higher contact pressures related to prosthesis design, femoral roll forward and internal rotation of the tibia can lead to postoperative anterior knee pain. Other in vitro studies showed higher reduction in mediolateral laxity after TKA and attributed this to overstuffing of the patellofemoral joint after patellar resurfacing. [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] Our results showed a reduction in mediolateral translation of only 2mm after surgery. Similar pre- and postoperative patellar kinematics concerning patellar tilt, -abduction, or -flexion were seen in our series indicating a correct restoration of anatomy and contact pressures.\u003c/p\u003e \u003cp\u003eOur study shows some limitations. Cadaveric preparation might influence joint- and ligament behavior. The use of the physiological knee simulator mimics loaded squatting motion, however the loads used in the muscles might not accurately reflect the natural loads experienced in vivo. We know that structural damage is occurring in ligaments from 5.14% strain levels and mechanoreceptors in ligaments have been documented [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], however the clinical value of ligament strain is unknown. On the other hand, a comparison between native and postoperative knees is valuable in terms of recreating native joint conditions.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eAccurate tibiofemoral kinematics and ligament behavior data based on passive flexion-extension motions were achieved with the Next-AR navigation tool. We believe that Next-AR provides a useful tool for the surgeon to accurately balance TKA and achieve targeted biomechanical properties.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eCompliance with ethical standards\u003c/h2\u003e \u003cp\u003eGP has been paid for presentations and has received research support from Medacta.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eEthical approval\u003c/h2\u003e \u003cp\u003eAll performed procedures were approved and done in accordance with the institutional research ethics committee (Katholieke Universiteit Leuven, Belgium, NH019 2021-04-01) and the 1964 Declaration of Helsinki and its later amendments for comparable ethi- cal standards.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eInformed consent\u003c/strong\u003e \u003cp\u003eKnee specimens were obtained from Anatomy, KU Leuven, Belgium. Donors had dedicated their bodies to education and science during life time.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThe study was funded and implants were donated by Medacta International, Switzerland.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003e- AVDV: Investigation, Data Curation, Writing - Original Draft, Resources, - OT.: Conceptualization, Methodology, Software, Validation, Formal analysis, Investigation, Data curation, Writing- Original Draft, Visualization, Project administration. - GP: Conceptualization, Methodology, Investigation, Resources, Data Curation, Writing - Review \u0026amp; Editing, Supervision, Project administration, Funding acquisition. - MB: Writing - Review \u0026amp; Editing, Supervision, Project administration.: - MD: Writing - Review \u0026amp; Editing.: - TL: Software, Investigation, Writing - Review \u0026amp; Editing, Project administration. - LS: Conceptualization, Methodology, Investigation, Resources, Data Curation, Writing - Review \u0026amp; Editing, Supervision, Project administration.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eGray HA, Guan S, Young TJ, Dowsey MM, Choong PF, Pandy MG (2020) Comparison of posterior-stabilized, cruciate-retaining, and medial-stabilized knee implant motion during gait. 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PMID: 25577221\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDelport H, Labey L, De Corte R, Innocenti B, Vander Sloten J, Bellemans J (2013) Collateral ligament strains during knee joint laxity evaluation before and after TKA. Clin Biomech (Bristol Avon) 28(7):777\u0026ndash;782. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.clinbiomech.2013.06.006\u003c/span\u003e\u003cspan address=\"10.1016/j.clinbiomech.2013.06.006\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6876936/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6876936/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eObjectives:\u003c/h2\u003e \u003cp\u003eThis study aimed to analyze to what extent a novel intraoperative navigation platform (Next-AR, Medacta) for total knee arthroplasty (TKA) allows to restore the native knee joint kinematics and strains in the medial collateral ligament (MCL) and lateral collateral ligament (LCL) throughout a squatting motion.\u003c/p\u003e\u003ch2\u003eMaterial and methods:\u003c/h2\u003e \u003cp\u003eComputed tomography (CT) scans of 6 native cadaver legs were used to design patient-specific guides. Bony landmarks and virtual single-line collateral ligaments were identified to acquire real-time intraoperative feedback on bone resection, implant alignment, tibiofemoral kinematics, and collateral ligament elongations using the Next-AR system. The specimens were subjected to squatting (35\u0026deg;-100\u0026deg;) motion using a physiological ex vivo knee simulator while maintaining a constant vertical ankle load of 110N through active quadriceps and bilateral hamstring controls. Subsequently, each knee underwent a medially-stabilized TKA (Medacta) with mechanical alignment technique and was retested under the same conditions as in their native state. The tibiofemoral and patellofemoral kinematics, along with collateral ligament strains, were computed from 3D marker trajectories using a six-camera optical system (Vicon). MCL and LCL insertions\u0026mdash;ant, mid, and post bundles\u0026mdash;were identified in relation to bone-pin markers using a wand.\u003c/p\u003e\u003ch2\u003eResults:\u003c/h2\u003e \u003cp\u003eBoth native and post-operative conditions exhibited similar tibial valgus orientation (Root Mean Square Error (RMSE\u0026thinsp;=\u0026thinsp;1.7\u0026deg;), patellar flexion (RMSE\u0026thinsp;=\u0026thinsp;1.2\u0026deg;), abduction (RMSE\u0026thinsp;=\u0026thinsp;0.5\u0026deg;), and rotation (RMSE\u0026thinsp;=\u0026thinsp;0.4\u0026deg;) during squatting (p\u0026thinsp;\u0026gt;\u0026thinsp;0.13). However, a significant difference was observed in tibial internal rotation between 35\u0026deg; and 62\u0026deg; (p\u0026thinsp;\u0026lt;\u0026thinsp;0.048, RMSE\u0026thinsp;=\u0026thinsp;3.2\u0026deg;). MCL strains in anterior (RMSE\u0026thinsp;=\u0026thinsp;1.5%), middle (RMSE\u0026thinsp;=\u0026thinsp;0.7%), and posterior (RMSE\u0026thinsp;=\u0026thinsp;0.8%) were closely matching in both conditions, showing no statistical differences (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Contrary, LCL strain in all bundles (RMSE\u0026thinsp;\u0026lt;\u0026thinsp;4.6%) differed significantly from mid to deep flexion in both conditions (p\u0026thinsp;\u0026lt;\u0026thinsp;0.048).\u003c/p\u003e\u003ch2\u003eConclusion:\u003c/h2\u003e \u003cp\u003eThe novel intraoperative Next-AR system not only targets planned knee alignment but also aids in restoring native knee kinematics and elongation of the collateral ligaments through real-time feedback.\u003c/p\u003e","manuscriptTitle":"Changes in kinematic behavior and collateral ligament strain after medially stabilized TKA using a novel Intraoperative Navigation Platform: a cadaveric study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-25 06:15:03","doi":"10.21203/rs.3.rs-6876936/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":"7a6fac80-3ad1-49c1-9e1e-89c38292bbbb","owner":[],"postedDate":"June 25th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-09-22T08:23:40+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-25 06:15:03","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6876936","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6876936","identity":"rs-6876936","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}