Robot‑assisted knee surgery: precision without superiority in joint line–patella restoration

Robot‑assisted knee surgery: precision without superiority in joint line–patella restoration | 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 Robot‑assisted knee surgery: precision without superiority in joint line–patella restoration Carlos Peñaherrera-Carrillo, Susana Cabrera-Ávila, Francisco Endara Urresta, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8289973/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 10 Feb, 2026 Read the published version in Journal of Robotic Surgery → Version 1 posted 9 You are reading this latest preprint version Abstract Introduction: Robot-assisted total knee arthroplasty (rTKA) has been proposed to improve precision in implant positioning and joint line restoration compared with manual TKA (mTKA). However, it remains unclear whether this increased accuracy results in superior functional or radiographic outcomes. This study aimed to compare mechanical alignment and patellofemoral restoration between robotic and manual techniques. Materials and Methods: A retrospective study including 600 consecutives primary TKAs performed from 2015 to 2024 was conducted. Patients were allocated into robotic (n=300) and manual (n=300) groups. All procedures were performed by the same arthroplasty team using a standardized surgical protocol and identical prosthesis model. Radiographic assessment included femorotibial mechanical axis and patellar orientation at a minimum of 12 months. Alignment was considered adequate when the absolute angular discrepancy was ≤2°. Statistical analyses included χ² tests, Student’s t-tests, and equivalence testing with the Two One-Sided Tests (TOST) method. Results: Baseline demographics were comparable between groups. All knees achieved alignment within the ≤2° tolerance (100% vs. 100%). Mean angular discrepancy showed no significant differences (manual 0.52° vs. robotic 0.48°; p=0.37). The robotic technique achieved a higher rate of exact matches (64% vs. 52%), while both remained within clinically accepted limits. Equivalence and non-inferiority analyses confirmed statistically and clinically equivalent outcomes between techniques. Conclusions: Robot-assisted TKA provides greater geometric precision; however, this advantage does not translate into measurable clinical or radiographic superiority when the manual technique is performed under a standardized protocol by experienced surgeons. Both methods demonstrated equivalent performance in restoring mechanical alignment and patellofemoral relationships. Level of Evidence: III. Retrospective comparative study. Arthroplasty Replacement Knee Robotics Knee Joint Patella Radiographic Image Interpretation Computer-Assisted Figures Figure 1 Figure 2 Figure 3 Introduction Knee osteoarthritis (KOA) is a common condition in older adults due to progressive wear and destruction of articular cartilage, and is a degenerative joint disease resulting from many factors. As a result of factors such as increased life expectancy and obesity, its prevalence continues to rise. Depending on the source, prevalence estimates range from 10% to 13%, with a 40% prevalence in patients entering their seventh decade ( 1 ). It is estimated that KOA will affect 78.4 million Americans by 2040 ( 2 ). The prevalence of symptomatic gonarthrosis is estimated at 44.7%. ( 3 ) According to the Mexican government, the prevalence rate is 10.5%, with females predominating (11.7%) and males (8.71%). ( 4 ) A patient with KOA experiences pain, swelling, stiffness, and limitations in daily life. ( 1 ) Treatment is determined by the severity of symptoms and the degree of joint wear, classified according to Kellgren–Lawrence ( 5 ). Among the nonsurgical and surgical options, total knee arthroplasty (TKA) is indicated in patients with severe degeneration and significant symptoms ( 6 ). The number of TKAs performed in the United States has increased by 134% over 20 years. ( 7 ) Further studies predict that primary TKAs will increase by 139% by 2040 and by 469% by 2060. ( 7 – 9 ) Despite being widely performed, well accepted, safe, and cost-effective, patient satisfaction rates remain between 82% and 89%. Dissatisfaction is caused by a variety of factors, including malalignment, incorrect prosthesis indication, soft-tissue imbalance, instability, high preoperative expectations, and altered joint line and patellar height (PH). ( 10 – 12 ) After TKA, any change in the joint line affects the biomechanics. ( 13 ) This changes the center of rotation, the isometry of the medial collateral ligament (MCL), resulting in midflexion instability. ( 14 , 15 ) Furthermore, JL elevation reduces posterior condylar offset, negatively affecting flexion angle and extensor mechanism force. A reported postoperative JL elevation after primary TKA ranges between 1.1 and 5.6 millimeters. ( 16 , 17 ) Studies suggest functional impairments occur when JL elevation exceeds 3 to 5 millimeters compared with preoperative values. ( 18 ) In response to dissatisfaction rates, robotic surgery has emerged as a potential solution. ( 19 ) Robotic knee arthroplasty (rTKA) has been shown to increase procedural precision. In comparison with conventional techniques, it achieves near-anatomical results in joint‑line position and has been reported to yield better functional outcomes. ( 20 – 24 ) Because evidence remains limited, this investigation was undertaken to examine rTKA, its relationship with joint‑line height and patellar position, and its impact on medium‑term functional outcomes. Materials and Methods A retrospective study comparing robot-assisted (rTKA) and conventional manual knee arthroplasty techniques was performed. The study period was January 2015 to December 2024, at a single high-specialty hospital. Population and Inclusion Criteria Three hundred consecutive primary TKAs were included in each group (total = 600), all performed by the same surgical team: Robotic group (n = 300): robot navigation and execution system-assisted. Manual group (n = 300): conventional intramedullary/extramedullary mechanical guides. Inclusion criteria: patients with primary knee osteoarthritis (Kellgren–Lawrence grade III or IV), tricompartmental disease, elective TKA indication, and a minimum radiographic follow‑up of 12 months. Exclusion criteria: prior peri‑articular fracture, revision surgery, non‑standard prosthesis, or deformities beyond 15°. Ethical Considerations The protocol was approved by the local Ethics and Research Committee and followed the principles of the Declaration of Helsinki. All patients provided informed consent for the procedure and anonymous use of their clinical data. Surgical Technique All surgeries followed a standardized protocol: regional anesthesia, medial parapatellar approach, distal femur and proximal tibia exposure, sequential soft tissue release, and extension/flexion gap balancing. In the robotic group, a navigation system with intraoperative three‑dimensional mapping, anatomic point registration, and guided bone cuts was used. In the manual group, cutting was done with standard extramedullary and intramedullary mechanical guides. In both groups, the same postero-stabilized (PS) prosthetic model was implanted, and the same cementing and postoperative rehabilitation protocols were applied. Radiographic Evaluation and Measurements Radiographs were obtained at 3, 6, and 12 months, and then annually, with a mean follow‑up of 24 ± 6 months. Measurements were made by two independent observers blinded to the surgical technique, using weight‑bearing anteroposterior and strict lateral radiographs. The following were determined: Femoro‑tibial mechanical axis (Line Axis, LA). Postoperative patellar orientation and position. Absolute angular discrepancy between the two parameters, classified as: − 0° (exact match), − 1° (mild deviation), − 2° (moderate discrepancy, clinically acceptable ≤ 2°). Alignment was defined as adequate if the absolute discrepancy was ≤ 2°. Statistical Analysis Data were analyzed using SPSS v.27 (IBM Corp., Armonk, NY). Continuous variables are presented as mean ± standard deviation (SD) or median [interquartile range], depending on distribution. Categorical variables were compared using χ² test or Fisher’s exact test; continuous variables with Student’s t‑test or Mann–Whitney U test. Equivalence analyses used a predefined margin of ± 10% and bilateral non‑inferiority testing (margin 5%), using the Two One‑Sided Tests (TOST) approach. A p‑value < 0.05 was considered statistically significant. Results Patient Flow and Baseline Characteristics Six hundred consecutive primary TKAs between January 2015 and December 2024 were analyzed, divided equally into robotic and manual groups (n = 300 each). Technique selection depended solely on robotic system availability, rather than on patient clinical characteristics, thereby avoiding indication bias. The same experienced arthroplasty team conducted all surgeries under a standardized protocol (medial parapatellar approach, distal femur/proximal tibia exposure, ligamentous release, gap balance, intra‑operative femoral rotation verification using epicondyles and Whiteside’s line, and final patellofemoral congruence check). The robotic group used intraoperative 3‑D mapping and guided cuts; the manual group used traditional mechanical guides. The same PS prosthesis model and identical cementing and rehabilitation protocols were used. Baseline demographics and clinical features were comparable: mean age 67.8 ± 8.9 years in manual vs. 66.5 ± 9.2 years in robotic (p = 0.21); female proportion 62% vs. 59% (p = 0.48); mean BMI 28.6 ± 4.3 vs. 28.9 ± 4.1 kg/m² (p = 0.63); prevalence of comorbidities (diabetes, hypertension, tricompartmental osteoarthritis, varus deformity > 10°) was similar (p > 0.05). Minimum radiographic follow‑up was 12 months, averaging 24 ± 6 months, during which there were no prosthetic loosening, revisions, or major complications influencing postoperative alignment. No patients were lost to follow‑up or excluded after surgery. (Table 1 ) Table 1 Baseline characteristics of the cohort Variable Manual (n = 300) Robotic (n = 300) P Value Age (years), mean ± SD 67.8 ± 8.9 66.5 ± 9.2 0.21 Sex female, n (%) 186 (62.0) 177 (59.0) 0.48 BMI (kg/m²), mean ± SD 28.6 ± 4.3 28.9 ± 4.1 0.63 Diabetes mellitus, n (%) 47 (15.7) 44 (14.7) 0.74 Hypertension, n (%) 179 (59.7) 182 (60.7) 0.82 Deformity > 10°, n (%) 38 (12.7) 41 (13.7) 0.73 PCL retention (CR), n (%) 300 (100) 300 (100) – Patellar component, n (%) 262 (87.3) 258 (86.0) 0.67 Concordance between the femoro‑tibial mechanical axis and post‑operative patellar position Evaluation of postoperative concordance between the femoro‑tibial mechanical axis (LA) and patellar orientation showed comparable performance in both techniques. Defining adequate alignment as absolute discrepancy ≤ 2°, 100% of knees in both groups achieved this criterion (p = 1.000, Fisher’s exact test), demonstrating that robotic and manual surgeries attain clinically satisfactory patellofemoral alignment. This indicates that within the functionally accepted range (< 2°), the probability of correct alignment is equivalent for both methods. From a clinical and biomechanical perspective, no significant superiority of robotic assistance over manual technique is evident when the exact alignment and balancing principles are followed. Distribution of Angular Discrepancy To examine residual angular variability more closely, the absolute difference between the mechanical axis and patellar position was classified: 0° (exact match), 1° (mild deviation), and 2° (moderate discrepancy, still clinically acceptable). In the manual technique group, 52% of cases showed exact coincidence (0°), 44% a deviation of 1°, and 4% a discrepancy of 2°. In the robotic group, 64% had exact coincidence, 24% a 1° deviation, and 12% a 2° discrepancy. (Fig. 1 ) Although the χ² test identified differences in distribution shape (p < 0.001), all measurements remained within the clinically accepted range for both groups. Mean angular values were similar: manual 0.52° vs. robotic 0.48° (difference = − 0.04°; p = 0.37). Medians were 0° in both groups, with identical IQRs (0–1°), confirming low and equivalent angular dispersion. (Fig. 2 ) Geometrically, the robotic technique showed a more ‘polarized’ pattern, a higher rate of exact matches, but a slight increase in 2° deviations. In contrast, the manual technique concentrated more cases at 1°, suggesting a centralized but equally controlled variability. None of these patterns implied behavior outside the optimal functional alignment range. (Table 2 ) Table 2 Postoperative angular outcomes Variable Manual (n = 300) Robotic (n = 300) Difference (IC 95%) P Value Exact match (0°), n (%) 156 (52.0) 192 (64.0) + 12.0 (+ 0.8 a + 22.9) 0.0029 Mild deviation (1°), n (%) 132 (44.0) 72 (24.0) –20.0 (–29.5 a − 10.6) < 0.001 Moderate discrepancy (2°), n (%) 12 (4.0) 36 (12.0) + 8.0 (+ 2.8 a + 13.2) 0.001 Within tolerance (≤ 2°), n (%) 300 (100) 300 (100) 0.0 (–2.1 a + 2.1) 1.000 Mean discrepancy (°) ± DE 0.52 ± 0.63 0.48 ± 0.71 –0.04 (–0.15 a + 0.23) 0.37 Median [IQR] (°) 0 [0–1] 0 [0–1] – – Equivalence and Non‑Inferiority Analysis An equivalence analysis with a ± 10% margin in the proportion of knees aligned within ± 2° was performed. The 95% confidence interval (CI) for the difference in proportions (0.0%; 95% CI − 2.1% to + 2.1%) lay entirely within the predefined margin, demonstrating both clinical and statistical equivalence between the techniques. (Fig. 3 ) Additionally, a bilateral non‑inferiority analysis (margin 5%) confirmed that neither method was inferior (p 10°, BMI > 35 kg/m², or non‑standard prostheses—maintained identical results (100% within ± 2° in both cohorts). (Table 3 ) Table 3 Equivalence and non-inferiority analysis Comparation Observed difference (%) Equivalence margin (%) 95% CI of the difference Result Proportion within ± 2° (Robotic – Manual) 0.0 ± 10 [–2.1, + 2.1] Equivalent Idem (margin ± 5%) 0.0 ± 5 [–2.1, + 2.1] Equivalent Two-sided non-inferiority test (5% margin) 0.0 5 [–2.1, + 2.1] Non-inferiority demonstrated Sensitivity analysis (excluding BMI > 35 or deformity > 10°) 0.0 ± 10 [–2.4, + 1.8] Unchanged result Clinical Interpretation Overall, the results demonstrate that under standardized operative conditions and controlled execution, robot‑assisted and conventional manual TKA achieve equivalent patellofemoral alignment. Every case in both cohorts fell within the clinically acceptable tolerance (< 2°), without increased angular dispersion or a higher malalignment rate. Although the robotic technique achieved a greater proportion of exact 0° coincidences, this reflects increased mathematical precision rather than a tangible clinical benefit. The slight variability observed in the manual technique falls within the expected measurement precision of radiographic methods and has no functional consequences. Consequently, evidence suggests that in the hands of experienced surgeons following a reproducible surgical protocol, robot‑assisted TKA does not offer significant clinical advantages over manual technique with respect to mechanical axis alignment or patellofemoral congruence. In summary, both approaches demonstrated equivalent biomechanical and functional behavior, with consistent, reproducible, and clinically satisfactory results, supporting the absence of a significant difference between the two surgical modalities. Discussion Robot-assisted total knee arthroplasty (rTKA) has emerged as a technological alternative to the conventional manual technique (mTKA) in advanced gonarthrosis. In our study, both groups achieved mechanical alignment and patellofemoral congruence within the clinically acceptable range, with no significant functional differences between techniques. This finding is consistent with a recent meta-analysis showing that although rTKA achieves better postoperative alignment, it does not translate into clear clinical or functional improvements in the short to mid-term ( 25 – 27 ). From a biomechanical perspective, accuracy in implant positioning and restoration of the joint line are essential to prevent instability, ligament-muscular imbalance, or alterations in the extensor mechanism. Several studies indicate that rTKA reduces the rate of out-of-range cases in the mechanical axis (HKA) and other complementary implant-related angles ( 26 , 28 ). However, improvements in precision have not consistently translated into greater satisfaction or increased range of motion at one year postoperatively. This may be explained by the high proficiency achieved by experienced surgeons using the manual technique, or by the influence of other factors (such as soft-tissue balancing, rehabilitation protocols, or patient expectations), which may play a role as important as geometric accuracy. In the context of severe deformities, altered joint lines, or revision cases, rTKA may offer a more evident advantage. Recent studies support that the greater investment in technology is justified when anatomy presents major challenges or when a minimal margin of error is required ( 29 , 30 ). For primary procedures without added complexity, however, the equivalent clinical outcomes suggest that the manual technique remains a valid and efficient option. Methodologically, the current trend in comparing surgical techniques is to use equivalence or non-inferiority designs rather than simply demonstrating superiority. Several studies have emphasized that reproducibility and standardization of the surgical protocol—rather than mere technological adoption—are key to optimizing outcomes ( 31 ). This aligns with our findings: the experience of the surgical team, a standardized robotic assistance system, and appropriate patient selection can level the field between both techniques. Finally, several limitations of our study must be acknowledged. First, the retrospective design reduces the ability to establish causality and may introduce selection bias, although both groups were comparable in baseline variables. Secondly, the follow-up period, although adequate to evaluate functional outcomes and mid-term alignment, does not allow conclusions regarding implant durability or long-term complications. Additionally, the study was conducted in a single center with a single surgical team, which enhances technical homogeneity but limits the generalizability of the findings to settings with different learning curves or technological resources. Cost-effectiveness, operative time, and the robotic learning curve were also not analyzed, despite being decisive factors in clinical implementation. In this sense, although the findings provide internal robustness, they should be interpreted with caution regarding their broader applicability. Conclusions Robot-assisted total knee arthroplasty provides superior geometric precision in restoring the joint line and patellofemoral alignment; however, this accuracy does not translate into significant clinical benefits when manual surgery is performed under a standardized protocol by experienced surgeons. Both techniques demonstrated safety, reproducibility, and equivalent functional outcomes, confirming the clinical non-inferiority of the manual technique compared with the robotic one. The use of assisted technology should be reserved for cases with high anatomical complexity or severe deformities, prioritizing treatment individualization and optimization of surgical resources. Abbreviations SD: standard deviation BMI: body mass index PCL: posterior cruciate ligament CR: cruciate retaining CI: confidence interval Declarations Credit author statement: Author: Carlos Patricio Peñaherrera Carrillo Contribution: conception of work, data curation, research, formal analysis, drafting work, critically revised work for intellectual content, final approval for publication, agreement of accountability Author: María Susana Cabrera Ávila Contribution: conception of work, data curation, research, drafting work, final approval for publication, and agreement of accountability Author: Francisco Endara Urresta Contribution: conception of work, research, drafting work, critically revised work for intellectual content, final approval for publication, and agreement of accountability Author: Alejandro Xavier Barros Castro Contribution: conception of work, drafting work, critically revised work for intellectual content, final approval for publication, and agreement of accountability Author: Eduardo Durán-Arce Contribution: conception of work, drafting work, critically revised work for intellectual content, final approval for publication, and agreement of accountability Author: Alejandro Guillermo Gallegos-Tejeda Contribution: conception of work, drafting work, critically revised work for intellectual content, final approval for publication, and agreement of accountability Author: Carlos Enrique Suárez Ahedo Contribution: conception of work, critically revised work for intellectual content, major revisions for intellectual content, final approval for publication, agreement of accountability Author: Carlos Javier Pineda Villaseñor Contribution: conception of work, critically revised work for intellectual content, major revisions for intellectual content, final approval for publication, agreement of accountability Conflict of interest None of the authors declare any conflicts of interest. 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Cite Share Download PDF Status: Published Journal Publication published 10 Feb, 2026 Read the published version in Journal of Robotic Surgery → Version 1 posted Editorial decision: Revision requested 21 Dec, 2025 Reviews received at journal 21 Dec, 2025 Reviewers agreed at journal 21 Dec, 2025 Reviews received at journal 14 Dec, 2025 Reviewers agreed at journal 07 Dec, 2025 Reviewers invited by journal 07 Dec, 2025 Editor assigned by journal 07 Dec, 2025 Submission checks completed at journal 06 Dec, 2025 First submitted to journal 05 Dec, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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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-8289973","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":557787258,"identity":"edcb76ec-54dc-4719-897b-74c3b45e987a","order_by":0,"name":"Carlos Peñaherrera-Carrillo","email":"","orcid":"","institution":"National Autonomous University of Mexico","correspondingAuthor":false,"prefix":"","firstName":"Carlos","middleName":"","lastName":"Peñaherrera-Carrillo","suffix":""},{"id":557787260,"identity":"891c9f29-19b3-4a5c-bbc9-d8a428a5ffca","order_by":1,"name":"Susana Cabrera-Ávila","email":"","orcid":"","institution":"National 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16:40:01","extension":"xml","order_by":9,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":90120,"visible":true,"origin":"","legend":"","description":"","filename":"94a35f67074648369c0067bc20ec43561structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8289973/v1/7208cbef71abdb5d9217a925.xml"},{"id":98023083,"identity":"97c166fe-118e-4761-9ad1-dcf64a9b3c7f","added_by":"auto","created_at":"2025-12-12 01:14:54","extension":"html","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":105047,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8289973/v1/ef09dadd8cafba6f6e578851.html"},{"id":98023069,"identity":"c5ed8b8c-2696-4516-bdca-018e6fdfb7cd","added_by":"auto","created_at":"2025-12-12 01:14:54","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":48280,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution of angular discrepancy between the femorotibial mechanical axis and patellar position according to the surgical technique. Although the distributions differ in shape, all values remain within the clinical tolerance (≤ 2°).\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8289973/v1/523290c805a9c50675e7a9f9.png"},{"id":98427386,"identity":"12fccc45-6243-434b-8847-98679bc100ca","added_by":"auto","created_at":"2025-12-17 16:40:16","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":338299,"visible":true,"origin":"","legend":"\u003cp\u003eBoxplots of absolute discrepancy. Both groups show overlapping medians and low dispersion, with no significant differences (p \u0026gt; 0.05).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8289973/v1/03729c1c0c40c9ba2ab7e272.png"},{"id":98424641,"identity":"14e3ff56-a752-4dde-9802-7454e577c198","added_by":"auto","created_at":"2025-12-17 16:33:36","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":288125,"visible":true,"origin":"","legend":"\u003cp\u003eTwo-one-sided equivalence test (TOST) for the proportion of alignments within ±2°. The observed difference (0%) and its 95% CI (–2.1 to +2.1) lie entirely within the ±10% margin, confirming clinical equivalence between robotic and manual surgery.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8289973/v1/7534c637a68d3e981aff8c05.png"},{"id":102785582,"identity":"a3f62fea-5780-402c-ae9a-fe0b01c77b11","added_by":"auto","created_at":"2026-02-16 16:08:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1273400,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8289973/v1/0d7b6515-46e2-4d80-952a-d70e365868d0.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Robot‑assisted knee surgery: precision without superiority in joint line–patella restoration","fulltext":[{"header":"Introduction","content":"\u003cp\u003eKnee osteoarthritis (KOA) is a common condition in older adults due to progressive wear and destruction of articular cartilage, and is a degenerative joint disease resulting from many factors. As a result of factors such as increased life expectancy and obesity, its prevalence continues to rise. Depending on the source, prevalence estimates range from 10% to 13%, with a 40% prevalence in patients entering their seventh decade (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). It is estimated that KOA will affect 78.4\u0026nbsp;million Americans by 2040 (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). The prevalence of symptomatic gonarthrosis is estimated at 44.7%. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) According to the Mexican government, the prevalence rate is 10.5%, with females predominating (11.7%) and males (8.71%). (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e) A patient with KOA experiences pain, swelling, stiffness, and limitations in daily life. (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e)\u003c/p\u003e\u003cp\u003eTreatment is determined by the severity of symptoms and the degree of joint wear, classified according to Kellgren\u0026ndash;Lawrence (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). Among the nonsurgical and surgical options, total knee arthroplasty (TKA) is indicated in patients with severe degeneration and significant symptoms (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe number of TKAs performed in the United States has increased by 134% over 20 years. (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e) Further studies predict that primary TKAs will increase by 139% by 2040 and by 469% by 2060. (\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e)\u003c/p\u003e\u003cp\u003eDespite being widely performed, well accepted, safe, and cost-effective, patient satisfaction rates remain between 82% and 89%. Dissatisfaction is caused by a variety of factors, including malalignment, incorrect prosthesis indication, soft-tissue imbalance, instability, high preoperative expectations, and altered joint line and patellar height (PH). (\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e)\u003c/p\u003e\u003cp\u003eAfter TKA, any change in the joint line affects the biomechanics. (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e) This changes the center of rotation, the isometry of the medial collateral ligament (MCL), resulting in midflexion instability. (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e)\u003c/p\u003e\u003cp\u003eFurthermore, JL elevation reduces posterior condylar offset, negatively affecting flexion angle and extensor mechanism force. A reported postoperative JL elevation after primary TKA ranges between 1.1 and 5.6 millimeters. (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e)\u003c/p\u003e\u003cp\u003eStudies suggest functional impairments occur when JL elevation exceeds 3 to 5 millimeters compared with preoperative values. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e)\u003c/p\u003e\u003cp\u003eIn response to dissatisfaction rates, robotic surgery has emerged as a potential solution. (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e) Robotic knee arthroplasty (rTKA) has been shown to increase procedural precision. In comparison with conventional techniques, it achieves near-anatomical results in joint‑line position and has been reported to yield better functional outcomes. (\u003cspan additionalcitationids=\"CR21 CR22 CR23\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e)\u003c/p\u003e\u003cp\u003eBecause evidence remains limited, this investigation was undertaken to examine rTKA, its relationship with joint‑line height and patellar position, and its impact on medium‑term functional outcomes.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cp\u003eA retrospective study comparing robot-assisted (rTKA) and conventional manual knee arthroplasty techniques was performed. The study period was January 2015 to December 2024, at a single high-specialty hospital.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003ePopulation and Inclusion Criteria\u003c/h2\u003e\u003cp\u003eThree hundred consecutive primary TKAs were included in each group (total\u0026thinsp;=\u0026thinsp;600), all performed by the same surgical team:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eRobotic group (n\u0026thinsp;=\u0026thinsp;300): robot navigation and execution system-assisted.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eManual group (n\u0026thinsp;=\u0026thinsp;300): conventional intramedullary/extramedullary mechanical guides.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eInclusion criteria: patients with primary knee osteoarthritis (Kellgren\u0026ndash;Lawrence grade III or IV), tricompartmental disease, elective TKA indication, and a minimum radiographic follow‑up of 12 months. Exclusion criteria: prior peri‑articular fracture, revision surgery, non‑standard prosthesis, or deformities beyond 15\u0026deg;.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eEthical Considerations\u003c/h3\u003e\n\u003cp\u003e The protocol was approved by the local Ethics and Research Committee and followed the principles of the Declaration of Helsinki. All patients provided informed consent for the procedure and anonymous use of their clinical data.\u003c/p\u003e\n\u003ch3\u003eSurgical Technique\u003c/h3\u003e\n\u003cp\u003eAll surgeries followed a standardized protocol: regional anesthesia, medial parapatellar approach, distal femur and proximal tibia exposure, sequential soft tissue release, and extension/flexion gap balancing.\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eIn the robotic group, a navigation system with intraoperative three‑dimensional mapping, anatomic point registration, and guided bone cuts was used.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eIn the manual group, cutting was done with standard extramedullary and intramedullary mechanical guides. In both groups, the same postero-stabilized (PS) prosthetic model was implanted, and the same cementing and postoperative rehabilitation protocols were applied.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\n\u003ch3\u003eRadiographic Evaluation and Measurements\u003c/h3\u003e\n\u003cp\u003eRadiographs were obtained at 3, 6, and 12 months, and then annually, with a mean follow‑up of 24\u0026thinsp;\u0026plusmn;\u0026thinsp;6 months. Measurements were made by two independent observers blinded to the surgical technique, using weight‑bearing anteroposterior and strict lateral radiographs. The following were determined:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eFemoro‑tibial mechanical axis (Line Axis, LA).\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003ePostoperative patellar orientation and position.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eAbsolute angular discrepancy between the two parameters, classified as:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u0026minus;\u0026thinsp;0\u0026deg; (exact match),\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u0026minus;\u0026thinsp;1\u0026deg; (mild deviation),\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u0026minus;\u0026thinsp;2\u0026deg; (moderate discrepancy, clinically acceptable\u0026thinsp;\u0026le;\u0026thinsp;2\u0026deg;).\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eAlignment was defined as adequate if the absolute discrepancy was \u0026le;\u0026thinsp;2\u0026deg;.\u003c/p\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003eStatistical Analysis\u003c/h2\u003e\u003cp\u003eData were analyzed using SPSS v.27 (IBM Corp., Armonk, NY). Continuous variables are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD) or median [interquartile range], depending on distribution. Categorical variables were compared using χ\u0026sup2; test or Fisher\u0026rsquo;s exact test; continuous variables with Student\u0026rsquo;s t‑test or Mann\u0026ndash;Whitney U test. Equivalence analyses used a predefined margin of \u0026plusmn;\u0026thinsp;10% and bilateral non‑inferiority testing (margin 5%), using the Two One‑Sided Tests (TOST) approach. A p‑value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003ePatient Flow and Baseline Characteristics\u003c/h2\u003e\u003cp\u003eSix hundred consecutive primary TKAs between January 2015 and December 2024 were analyzed, divided equally into robotic and manual groups (n\u0026thinsp;=\u0026thinsp;300 each). Technique selection depended solely on robotic system availability, rather than on patient clinical characteristics, thereby avoiding indication bias. The same experienced arthroplasty team conducted all surgeries under a standardized protocol (medial parapatellar approach, distal femur/proximal tibia exposure, ligamentous release, gap balance, intra‑operative femoral rotation verification using epicondyles and Whiteside\u0026rsquo;s line, and final patellofemoral congruence check). The robotic group used intraoperative 3‑D mapping and guided cuts; the manual group used traditional mechanical guides. The same PS prosthesis model and identical cementing and rehabilitation protocols were used.\u003c/p\u003e\u003cp\u003eBaseline demographics and clinical features were comparable: mean age 67.8\u0026thinsp;\u0026plusmn;\u0026thinsp;8.9 years in manual vs. 66.5\u0026thinsp;\u0026plusmn;\u0026thinsp;9.2 years in robotic (p\u0026thinsp;=\u0026thinsp;0.21); female proportion 62% vs. 59% (p\u0026thinsp;=\u0026thinsp;0.48); mean BMI 28.6\u0026thinsp;\u0026plusmn;\u0026thinsp;4.3 vs. 28.9\u0026thinsp;\u0026plusmn;\u0026thinsp;4.1 kg/m\u0026sup2; (p\u0026thinsp;=\u0026thinsp;0.63); prevalence of comorbidities (diabetes, hypertension, tricompartmental osteoarthritis, varus deformity\u0026thinsp;\u0026gt;\u0026thinsp;10\u0026deg;) was similar (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Minimum radiographic follow‑up was 12 months, averaging 24\u0026thinsp;\u0026plusmn;\u0026thinsp;6 months, during which there were no prosthetic loosening, revisions, or major complications influencing postoperative alignment. No patients were lost to follow‑up or excluded after surgery. (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\u003eBaseline characteristics of the cohort\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\u003cp\u003eVariable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eManual (n\u0026thinsp;=\u0026thinsp;300)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRobotic (n\u0026thinsp;=\u0026thinsp;300)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\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\u003eAge (years), mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e67.8\u0026thinsp;\u0026plusmn;\u0026thinsp;8.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e66.5\u0026thinsp;\u0026plusmn;\u0026thinsp;9.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.21\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSex female, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e186 (62.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e177 (59.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.48\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBMI (kg/m\u0026sup2;), mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e28.6\u0026thinsp;\u0026plusmn;\u0026thinsp;4.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e28.9\u0026thinsp;\u0026plusmn;\u0026thinsp;4.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.63\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDiabetes mellitus, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e47 (15.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e44 (14.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.74\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHypertension, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e179 (59.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e182 (60.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.82\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDeformity\u0026thinsp;\u0026gt;\u0026thinsp;10\u0026deg;, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e38 (12.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e41 (13.7)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.73\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePCL retention (CR), n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e300 (100)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e300 (100)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePatellar component, n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e262 (87.3)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e258 (86.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.67\u003c/p\u003e\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\u003eConcordance between the femoro‑tibial mechanical axis and post‑operative patellar position\u003c/h3\u003e\n\u003cp\u003eEvaluation of postoperative concordance between the femoro‑tibial mechanical axis (LA) and patellar orientation showed comparable performance in both techniques. Defining adequate alignment as absolute discrepancy\u0026thinsp;\u0026le;\u0026thinsp;2\u0026deg;, 100% of knees in both groups achieved this criterion (p\u0026thinsp;=\u0026thinsp;1.000, Fisher\u0026rsquo;s exact test), demonstrating that robotic and manual surgeries attain clinically satisfactory patellofemoral alignment. This indicates that within the functionally accepted range (\u0026lt;\u0026thinsp;2\u0026deg;), the probability of correct alignment is equivalent for both methods. From a clinical and biomechanical perspective, no significant superiority of robotic assistance over manual technique is evident when the exact alignment and balancing principles are followed.\u003c/p\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003eDistribution of Angular Discrepancy\u003c/h2\u003e\u003cp\u003eTo examine residual angular variability more closely, the absolute difference between the mechanical axis and patellar position was classified: 0\u0026deg; (exact match), 1\u0026deg; (mild deviation), and 2\u0026deg; (moderate discrepancy, still clinically acceptable). In the manual technique group, 52% of cases showed exact coincidence (0\u0026deg;), 44% a deviation of 1\u0026deg;, and 4% a discrepancy of 2\u0026deg;. In the robotic group, 64% had exact coincidence, 24% a 1\u0026deg; deviation, and 12% a 2\u0026deg; discrepancy. (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e)\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAlthough the χ\u0026sup2; test identified differences in distribution shape (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), all measurements remained within the clinically accepted range for both groups. Mean angular values were similar: manual 0.52\u0026deg; vs. robotic 0.48\u0026deg; (difference = \u0026minus;\u0026thinsp;0.04\u0026deg;; p\u0026thinsp;=\u0026thinsp;0.37). Medians were 0\u0026deg; in both groups, with identical IQRs (0\u0026ndash;1\u0026deg;), confirming low and equivalent angular dispersion. (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e)\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eGeometrically, the robotic technique showed a more \u0026lsquo;polarized\u0026rsquo; pattern, a higher rate of exact matches, but a slight increase in 2\u0026deg; deviations. In contrast, the manual technique concentrated more cases at 1\u0026deg;, suggesting a centralized but equally controlled variability. None of these patterns implied behavior outside the optimal functional alignment range. (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e)\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003ePostoperative angular outcomes\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\u003cp\u003eVariable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eManual (n\u0026thinsp;=\u0026thinsp;300)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRobotic (n\u0026thinsp;=\u0026thinsp;300)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eDifference (IC 95%)\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\u003eExact match (0\u0026deg;), n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e156 (52.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e192 (64.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e+\u0026thinsp;12.0 (+\u0026thinsp;0.8 a\u0026thinsp;+\u0026thinsp;22.9)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.0029\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMild deviation (1\u0026deg;), n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e132 (44.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e72 (24.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026ndash;20.0 (\u0026ndash;29.5 a \u0026minus;\u0026thinsp;10.6)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eModerate discrepancy (2\u0026deg;), n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e12 (4.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e36 (12.0)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e+\u0026thinsp;8.0 (+\u0026thinsp;2.8 a\u0026thinsp;+\u0026thinsp;13.2)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.001\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eWithin tolerance (\u0026le;\u0026thinsp;2\u0026deg;), n (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e300 (100)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e300 (100)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0.0 (\u0026ndash;2.1 a\u0026thinsp;+\u0026thinsp;2.1)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1.000\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMean discrepancy (\u0026deg;)\u0026thinsp;\u0026plusmn;\u0026thinsp;DE\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.52\u0026thinsp;\u0026plusmn;\u0026thinsp;0.63\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0.48\u0026thinsp;\u0026plusmn;\u0026thinsp;0.71\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026ndash;0.04 (\u0026ndash;0.15 a\u0026thinsp;+\u0026thinsp;0.23)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0.37\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eMedian [IQR] (\u0026deg;)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 [0\u0026ndash;1]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0 [0\u0026ndash;1]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u0026ndash;\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003eEquivalence and Non‑Inferiority Analysis\u003c/h2\u003e\u003cp\u003eAn equivalence analysis with a\u0026thinsp;\u0026plusmn;\u0026thinsp;10% margin in the proportion of knees aligned within \u0026plusmn;\u0026thinsp;2\u0026deg; was performed. The 95% confidence interval (CI) for the difference in proportions (0.0%; 95% CI \u0026minus;\u0026thinsp;2.1% to +\u0026thinsp;2.1%) lay entirely within the predefined margin, demonstrating both clinical and statistical equivalence between the techniques. (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e)\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAdditionally, a bilateral non‑inferiority analysis (margin 5%) confirmed that neither method was inferior (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001 for both TOST contrasts), consolidating the conclusion of equivalent performance. Sensitivity analyses\u0026mdash;excluding cases with deformities\u0026thinsp;\u0026gt;\u0026thinsp;10\u0026deg;, BMI\u0026thinsp;\u0026gt;\u0026thinsp;35 kg/m\u0026sup2;, or non‑standard prostheses\u0026mdash;maintained identical results (100% within \u0026plusmn;\u0026thinsp;2\u0026deg; in both cohorts). (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\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\u003eEquivalence and non-inferiority analysis\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"+\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eComparation\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eObserved difference (%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eEquivalence margin (%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e95% CI of the difference\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eResult\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eProportion within \u0026plusmn;\u0026thinsp;2\u0026deg; (Robotic \u0026ndash; Manual)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026plusmn;\u0026thinsp;10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"+\" colname=\"c4\"\u003e\u003cp\u003e[\u0026ndash;2.1, + 2.1]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eEquivalent\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eIdem (margin\u0026thinsp;\u0026plusmn;\u0026thinsp;5%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026plusmn;\u0026thinsp;5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"+\" colname=\"c4\"\u003e\u003cp\u003e[\u0026ndash;2.1, + 2.1]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eEquivalent\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTwo-sided non-inferiority test (5% margin)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"+\" colname=\"c4\"\u003e\u003cp\u003e[\u0026ndash;2.1, + 2.1]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eNon-inferiority demonstrated\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSensitivity analysis (excluding BMI\u0026thinsp;\u0026gt;\u0026thinsp;35 or deformity\u0026thinsp;\u0026gt;\u0026thinsp;10\u0026deg;)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u0026plusmn;\u0026thinsp;10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"+\" colname=\"c4\"\u003e\u003cp\u003e[\u0026ndash;2.4, + 1.8]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eUnchanged result\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003eClinical Interpretation\u003c/h2\u003e\u003cp\u003eOverall, the results demonstrate that under standardized operative conditions and controlled execution, robot‑assisted and conventional manual TKA achieve equivalent patellofemoral alignment. Every case in both cohorts fell within the clinically acceptable tolerance (\u0026lt;\u0026thinsp;2\u0026deg;), without increased angular dispersion or a higher malalignment rate. Although the robotic technique achieved a greater proportion of exact 0\u0026deg; coincidences, this reflects increased mathematical precision rather than a tangible clinical benefit. The slight variability observed in the manual technique falls within the expected measurement precision of radiographic methods and has no functional consequences. Consequently, evidence suggests that in the hands of experienced surgeons following a reproducible surgical protocol, robot‑assisted TKA does not offer significant clinical advantages over manual technique with respect to mechanical axis alignment or patellofemoral congruence. In summary, both approaches demonstrated equivalent biomechanical and functional behavior, with consistent, reproducible, and clinically satisfactory results, supporting the absence of a significant difference between the two surgical modalities.\u003c/p\u003e\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eRobot-assisted total knee arthroplasty (rTKA) has emerged as a technological alternative to the conventional manual technique (mTKA) in advanced gonarthrosis. In our study, both groups achieved mechanical alignment and patellofemoral congruence within the clinically acceptable range, with no significant functional differences between techniques. This finding is consistent with a recent meta-analysis showing that although rTKA achieves better postoperative alignment, it does not translate into clear clinical or functional improvements in the short to mid-term (\u003cspan additionalcitationids=\"CR26\" citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eFrom a biomechanical perspective, accuracy in implant positioning and restoration of the joint line are essential to prevent instability, ligament-muscular imbalance, or alterations in the extensor mechanism. Several studies indicate that rTKA reduces the rate of out-of-range cases in the mechanical axis (HKA) and other complementary implant-related angles (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e). However, improvements in precision have not consistently translated into greater satisfaction or increased range of motion at one year postoperatively. This may be explained by the high proficiency achieved by experienced surgeons using the manual technique, or by the influence of other factors (such as soft-tissue balancing, rehabilitation protocols, or patient expectations), which may play a role as important as geometric accuracy.\u003c/p\u003e\u003cp\u003eIn the context of severe deformities, altered joint lines, or revision cases, rTKA may offer a more evident advantage. Recent studies support that the greater investment in technology is justified when anatomy presents major challenges or when a minimal margin of error is required (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e). For primary procedures without added complexity, however, the equivalent clinical outcomes suggest that the manual technique remains a valid and efficient option.\u003c/p\u003e\u003cp\u003eMethodologically, the current trend in comparing surgical techniques is to use equivalence or non-inferiority designs rather than simply demonstrating superiority. Several studies have emphasized that reproducibility and standardization of the surgical protocol\u0026mdash;rather than mere technological adoption\u0026mdash;are key to optimizing outcomes (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e). This aligns with our findings: the experience of the surgical team, a standardized robotic assistance system, and appropriate patient selection can level the field between both techniques.\u003c/p\u003e\u003cp\u003eFinally, several limitations of our study must be acknowledged. First, the retrospective design reduces the ability to establish causality and may introduce selection bias, although both groups were comparable in baseline variables. Secondly, the follow-up period, although adequate to evaluate functional outcomes and mid-term alignment, does not allow conclusions regarding implant durability or long-term complications. Additionally, the study was conducted in a single center with a single surgical team, which enhances technical homogeneity but limits the generalizability of the findings to settings with different learning curves or technological resources. Cost-effectiveness, operative time, and the robotic learning curve were also not analyzed, despite being decisive factors in clinical implementation. In this sense, although the findings provide internal robustness, they should be interpreted with caution regarding their broader applicability.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eRobot-assisted total knee arthroplasty provides superior geometric precision in restoring the joint line and patellofemoral alignment; however, this accuracy does not translate into significant clinical benefits when manual surgery is performed under a standardized protocol by experienced surgeons.\u003c/p\u003e\u003cp\u003eBoth techniques demonstrated safety, reproducibility, and equivalent functional outcomes, confirming the clinical non-inferiority of the manual technique compared with the robotic one.\u003c/p\u003e\u003cp\u003eThe use of assisted technology should be reserved for cases with high anatomical complexity or severe deformities, prioritizing treatment individualization and optimization of surgical resources.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003e\u003cstrong\u003eSD:\u0026nbsp;\u003c/strong\u003estandard deviation\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eBMI:\u0026nbsp;\u003c/strong\u003ebody mass index\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePCL:\u0026nbsp;\u003c/strong\u003eposterior cruciate ligament\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCR:\u0026nbsp;\u003c/strong\u003ecruciate retaining\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCI:\u003c/strong\u003e confidence interval\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eCredit author statement:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor:\u0026nbsp;\u003c/strong\u003eCarlos Patricio Peñaherrera Carrillo\u003c/p\u003e\n\u003cp\u003eContribution: conception of work, data curation, research, formal analysis, drafting work, critically revised work for intellectual content, final approval for publication, agreement of accountability\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor:\u003c/strong\u003e María Susana Cabrera Ávila\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eContribution: conception of work, data curation, research, drafting work, final approval for publication, and agreement of accountability\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor:\u0026nbsp;\u003c/strong\u003eFrancisco Endara Urresta\u003c/p\u003e\n\u003cp\u003eContribution: conception of work, research, drafting work, critically revised work for intellectual content, final approval for publication, and agreement of accountability\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor:\u003c/strong\u003e Alejandro Xavier Barros Castro\u003c/p\u003e\n\u003cp\u003eContribution: conception of work, drafting work, critically revised work for intellectual content, final approval for publication, and agreement of accountability\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor:\u0026nbsp;\u003c/strong\u003eEduardo Durán-Arce\u003c/p\u003e\n\u003cp\u003eContribution: conception of work, drafting work, critically revised work for intellectual content, final approval for publication, and agreement of accountability\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor:\u0026nbsp;\u003c/strong\u003eAlejandro Guillermo Gallegos-Tejeda\u003c/p\u003e\n\u003cp\u003eContribution: conception of work, drafting work, critically revised work for intellectual content, final approval for publication, and agreement of accountability\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor:\u003c/strong\u003e Carlos Enrique Suárez Ahedo\u003c/p\u003e\n\u003cp\u003eContribution: conception of work, critically revised work for intellectual content, major revisions for intellectual content, final approval for publication, agreement of accountability\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor:\u0026nbsp;\u003c/strong\u003eCarlos Javier Pineda Villaseñor\u003c/p\u003e\n\u003cp\u003eContribution: conception of work, critically revised work for intellectual content, major revisions for intellectual content, final approval for publication, agreement of accountability\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone of the authors declare any conflicts of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFinancial funding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone of the authors declare any financial funding.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eHsu H, Siwiec RM. 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Med Int Mex 2013; 29 (1): 67-92.\u003c/li\u003e\n\u003cli\u003eKellgren J \u0026amp; Lawrence J. Radiological Assessment of Osteo-Arthrosis. Ann Rheum Dis. 1957;16(4):494-502. doi:10.1136/ard.16.4.494\u003c/li\u003e\n\u003cli\u003eAweid O, Haider Z, Saed A, Kalairajah Y. Treatment modalities for hip and knee osteoarthritis: A systematic review of safety. J Orthop Surg (Hong Kong). 2018 May-Aug;26(3):2309499018808669\u003c/li\u003e\n\u003cli\u003eHome | Agency for Healthcare Research and Quality, https://www.ahrq.gov/ (Accessed 20 Nov 2022).\u003c/li\u003e\n\u003cli\u003eShichman I, Roof M, Askew N, Nherera L, Rozell JC, Seyler TM, Schwarzkopf R. Projections and Epidemiology of Primary Hip and Knee Arthroplasty in Medicare Patients to 2040-2060. JB JS Open Access. 2023 Feb 28;8(1):e22.00112. doi: 10.2106/JBJS.OA.22.00112. PMID: 36864906; PMCID: PMC9974080.\u003c/li\u003e\n\u003cli\u003eKahlenberg CA, Nwachukwu BU, McLawhorn AS, Cross MB, Cornell CN, Padgett DE. Patient satisfaction after total knee replacement: a systematic review. HSS J 2018;14:192\u0026ndash;201\u003c/li\u003e\n\u003cli\u003eBourne RB, Chesworth BM, Davis AM, Mahomed NN, Charron KDJ. Patient satisfaction after total knee arthroplasty: who is satisfied and who is not? Clin Orthop Relat Res 2010;468:57\u0026ndash;63\u003c/li\u003e\n\u003cli\u003eLording T, Lustig S, Neyret P. Coronal alignment after total knee arthroplasty. EFORT Open Rev 2017;1:12\u0026ndash;17\u003c/li\u003e\n\u003cli\u003eMatsuda S, Kawahara S, Okazaki K, Tashiro Y, Iwamoto Y. Postoperative alignment and ROM affect patient satisfaction after TKA. Clin Orthop Relat Res 2013;471:127\u0026ndash;133.\u003c/li\u003e\n\u003cli\u003eLieshout van, Valkering KP, Koen, Etten-Jamaludin van, Gino, Geenen van. The negative effect of joint line elevation after total knee arthroplasty on outcome. 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Arthroplasty. 2022 Jan 5;4(1).\u003c/li\u003e\n\u003cli\u003eGaillard R, Bankhead C, Budhiparama NC, C\u0026eacute;cile Batailler, Elvire Servien, Lustig S. Influence of Patella Height on Total Knee Arthroplasty: Outcomes and Survival. Journal of Arthroplasty. 2019 Mar 1;34(3):469\u0026ndash;77.\u003c/li\u003e\n\u003cli\u003eNakano N, Kuroda Y, Masanori Tsubosaka, Tomoyuki Kamenaga, Ishida K, Hayashi S, et al. The influence of patellar height on patellofemoral contact force during total knee arthroplasty. Journal of Joint Surgery and Research. 2023 Aug 18;1(1):186\u0026ndash;91.\u003c/li\u003e\n\u003cli\u003eJobe Shatrov, Milad Khasian, Lording T, Monk AP, Parker D, Lustig S. Robotic assessment of patella tracking in total knee arthroplasty. Journal of ISAKOS Joint Disorders \u0026amp; Orthopaedic Sports Medicine. 2024 Jun 21;9(5):100287\u0026ndash;7.\u003c/li\u003e\n\u003cli\u003eMayne AI, Harshadkumar Rajgor, Chathura Munasinghe, Agrawal Y, Pagkalos J, Davis ET, et al. The ROSA robotic-arm system reliably restores joint line height, patella height and posterior condylar offset in total knee arthroplasty. The Knee. 2024 Mar 11;48:1\u0026ndash;7.\u003c/li\u003e\n\u003cli\u003eAlrajeb R, Zarti M, Zakaria Shuia, Osama Alzobi, Ahmed G, Aissam Elmhiregh. Robotic-assisted versus conventional total knee arthroplasty: a systematic review and meta-analysis of randomized controlled trials. European Journal of Orthopaedic Surgery and Traumatology. 2023 Dec 22;PubMed\u003c/li\u003e\n\u003cli\u003eRiantho A, Christian J, Fidiasrianto K, Elson E, Irvan I, Handy Haryono, et al. Radiographic Outcomes of Robot-Assisted Versus Conventional Total Knee Arthroplasty. JB \u0026amp; JS Open Access. 2023 Jan 1;8(2).\u003c/li\u003e\n\u003cli\u003eFu X, She Y, Jin G, Liu C, Liu Z, Li W, et al. Comparison of robotic-assisted total knee arthroplasty: an updated systematic review and meta-analysis. Journal of Robotic Surgery. 2024 Jul 25;18(1).\u003c/li\u003e\n\u003cli\u003eSun, C., Ma, Q., Zhang, X. et al. Improved alignment accuracy but similar early clinical outcomes with NAVIO imageless robotic-assisted vs. conventional total knee arthroplasty: a meta-analysis. J Orthop Surg Res 20, 619 (2025). https://doi.org/10.1186/s13018-025-06013-6\u003c/li\u003e\n\u003cli\u003eXing, P., Qu, J., Feng, S. et al. Comparison of the efficacy of robot-assisted total knee arthroplasty in patients with knee osteoarthritis with varying severity deformity. J Orthop Surg Res 19, 872 (2024). https://doi.org/10.1186/s13018-024-05372-w\u003c/li\u003e\n\u003cli\u003eChen, J., Loke, R.W.K., Lim, K.KL. et al. Survivorship in robotic total knee arthroplasty compared with conventional total knee arthroplasty: A systematic review and meta-analysis. Arthroplasty 7, 21 (2025). https://doi.org/10.1186/s42836-025-00304-3\u003c/li\u003e\n\u003cli\u003e\u0026Uuml;mit Mert, Moh\u0026rsquo;d Yazan Khasawneh, Ghandour M, Zuabi AA, Horst K, Hildebrand F, et al. Comparative Efficacy and Precision of Robot-Assisted vs. Conventional Total Knee Arthroplasty: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Journal of Clinical Medicine J. Clin. Med. 2025, 14, 3249. https://doi.org/10.3390/jcm14093249\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-robotic-surgery","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jors","sideBox":"Learn more about [Journal of Robotic Surgery](http://link.springer.com/journal/11701)","snPcode":"11701","submissionUrl":"https://submission.nature.com/new-submission/11701/3","title":"Journal of Robotic Surgery","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Arthroplasty, Replacement, Knee; Robotics; Knee Joint; Patella; Radiographic Image Interpretation, Computer-Assisted","lastPublishedDoi":"10.21203/rs.3.rs-8289973/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8289973/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eIntroduction: \u003c/strong\u003eRobot-assisted total knee arthroplasty (rTKA) has been proposed to improve precision in implant positioning and joint line restoration compared with manual TKA (mTKA). However, it remains unclear whether this increased accuracy results in superior functional or radiographic outcomes. This study aimed to compare mechanical alignment and patellofemoral restoration between robotic and manual techniques.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMaterials and Methods: \u003c/strong\u003eA retrospective study including 600 consecutives primary TKAs performed from 2015 to 2024 was conducted. Patients were allocated into robotic (n=300) and manual (n=300) groups. All procedures were performed by the same arthroplasty team using a standardized surgical protocol and identical prosthesis model. Radiographic assessment included femorotibial mechanical axis and patellar orientation at a minimum of 12 months. Alignment was considered adequate when the absolute angular discrepancy was ≤2°. Statistical analyses included χ² tests, Student’s t-tests, and equivalence testing with the Two One-Sided Tests (TOST) method.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e Baseline demographics were comparable between groups. All knees achieved alignment within the ≤2° tolerance (100% vs. 100%). Mean angular discrepancy showed no significant differences (manual 0.52° vs. robotic 0.48°; p=0.37). The robotic technique achieved a higher rate of exact matches (64% vs. 52%), while both remained within clinically accepted limits. Equivalence and non-inferiority analyses confirmed statistically and clinically equivalent outcomes between techniques. Conclusions: Robot-assisted TKA provides greater geometric precision; however, this advantage does not translate into measurable clinical or radiographic superiority when the manual technique is performed under a standardized protocol by experienced surgeons. Both methods demonstrated equivalent performance in restoring mechanical alignment and patellofemoral relationships.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLevel of Evidence: \u003c/strong\u003eIII. Retrospective comparative study.\u003c/p\u003e","manuscriptTitle":"Robot‑assisted knee surgery: precision without superiority in joint line–patella restoration","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-12 01:14:49","doi":"10.21203/rs.3.rs-8289973/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-12-21T21:27:27+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-21T21:25:54+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"58202013881031313315092846353476812083","date":"2025-12-21T20:52:48+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-14T22:08:17+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"114319427763364520318160603583539772823","date":"2025-12-07T22:42:43+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-12-07T13:08:00+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-12-07T13:03:01+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-06T06:53:18+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Robotic Surgery","date":"2025-12-05T17:26:19+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-robotic-surgery","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jors","sideBox":"Learn more about [Journal of Robotic Surgery](http://link.springer.com/journal/11701)","snPcode":"11701","submissionUrl":"https://submission.nature.com/new-submission/11701/3","title":"Journal of Robotic Surgery","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"e385ff43-c204-4139-be71-45b5a775102d","owner":[],"postedDate":"December 12th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-02-16T16:06:28+00:00","versionOfRecord":{"articleIdentity":"rs-8289973","link":"https://doi.org/10.1007/s11701-026-03149-3","journal":{"identity":"journal-of-robotic-surgery","isVorOnly":false,"title":"Journal of Robotic Surgery"},"publishedOn":"2026-02-10 15:57:57","publishedOnDateReadable":"February 10th, 2026"},"versionCreatedAt":"2025-12-12 01:14:49","video":"","vorDoi":"10.1007/s11701-026-03149-3","vorDoiUrl":"https://doi.org/10.1007/s11701-026-03149-3","workflowStages":[]},"version":"v1","identity":"rs-8289973","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8289973","identity":"rs-8289973","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}